National Museum of Nature and Science Monographs
No. 45Olenekian (Early Triassic)
stratigraphy andfossil assemblages
in northeastern Vietnam

Edited by
Yasunari Shigeta
Toshifumi Komatsu
Takumi Maekawa
Huyen Dang Tran

National Museum of Nature and Science
Tokyo, March 2014

Editorial Board
Kazumi Yokoyama, Department of Geology & Paleontology, Editor-in-Chief
Yukiyasu Tsutsumi, Department of Geology & Paleontology
Tsukasa Iwashima, Department of Botany
Masanobu Higuchi, Department of Botany
Toshiaki Kuramochi, Department of Zoology
Gento Shinohara, Department of Zoology
Yuji Mizoguchi, Department of Anthropology
Yousuke Kaifu, Department of Anthropology
Itaru Ishii, Department of Science and Engineering
Toshihiro Horaguchi, Department of Science and Engineering
National Museum of Nature and Science
Ueno Park, Tokyo 110–8718
Japan

Copyright © 2014
National Museum of Nature and Science, Tokyo
Published on March 31, 2014
Printed by Kokusai Bunkensha Co. Ltd., Tokyo
ISSN: 1881-9109
ISBN: 978-4-87803-038-3

		v

Contents
Contributors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
Abstract. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii
Introduction(Y. Shigeta, T. Komatsu, H. T. Dang, T. Maekawa, O. Takahashi,
G. Tanaka and Y. Tsutsumi).. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Paleogeographical and geological setting(T. Komatsu, Y. Shigeta and H. T. Dang). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Stratigraphy of the Bac Thuy Formation(T. Komatsu, T. Maekawa and Y. Shigeta).. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Depositional environments of the Bac Thuy Formation(T. Komatsu, T. Maekawa, Y. Shigeta, H. T. Dang and P. D. Nguyen). . . . . . . . . . . . . . 35
Biostratigraphy
Ammonoid succession (Y. Shigeta). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
Conodont succession (T. Maekawa and T. Komatsu). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Correlation (Y. Shigeta and T. Maekawa). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Age of rhyolite from the Khon Lang Formation(Y. Tsutsumi and T. Komatsu). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Discussion
Aspects of Smithian ammonoid fauna (Y. Shigeta). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Internal features in the early whorls of ammonoids(Y. Shigeta and T. Maekawa). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Ammonoid mode of occurrence (Y. Shigeta and T. Komatsu). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Smithian gastropod assemblages of the Bac Thuy Formation(A. Kaim, A. Nützel and T. Maekawa). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Bivalve assemblages and mode of occurrence(T. Komatsu, H. T. Dang and T. C. Dinh).. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
Brief note on the radiolarian faunas of the Upper Smithian (Lower Triassic)(O. Takahashi). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Systematic Paleontology
Cephalopods (Y. Shigeta and H. D. Nguyen). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Gastropods (A. Kaim, A. Nützel and T. Maekawa). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
Bivalves (T. Komatsu, H. T. Dang and T. C. Dinh). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
Conodonts (T. Maekawa and H. Igo).. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
Ostracods (G. Tanaka, T. Komatsu and T. Maekawa). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271
Radiolarians (O. Takahashi and Y. Miyake). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 278
Concluding remarks (Y. Shigeta, T. Komatsu, T. Maekawa and H. T. Dang). . . . . . . . . . . . . . . . . . . 294
Acknowledgements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
References.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295

vi

Contributors
Huyen Dang Tran Department of Paleontology and Stratigraphy, Vietnam Institute of
Geosciences and Mineral Resources (VIGMR), Hanoi, Vietnam (E-mail: rigmr@fpt.vn)
Tien Dinh Cong Department of Paleontology and Stratigraphy, Vietnam Institute of Geosciences
and Mineral Resources (VIGMR), Hanoi, Vietnam (E-mail: dc_tien4985@yahoo.com)
Hisayoshi Igo Institute of Natural History, 3–14–24 Takada, Toshima-ku, Tokyo 171–0033,
Japan (E-mail: igohisa@mac.com)
Andrzej Kaim American Museum of Natural History, Central Park West at 79th Street, New
York, NY 10024–5192, U.S.A. and Instytut Paleobiologii PAN, ul. Twarda 51/55 00–818
Warszawa, Poland (E-mail: kaim@twarda.pan.pl)
Toshifumi Komatsu Graduate School of Science and Technology, Kumamoto University, 2–39–
1 Kurokami, Chuo-ku, Kumamoto 860–8555, Japan (E-mail: komatsu@sci.kumamoto-u.ac.jp)
Huu Nguyen Dinh Department of Paleontology and Stratigraphy, Vietnam Institute of
Geosciences and Mineral Resources (VIGMR), Hanoi, Vietnam (E-mail: rigmr@fpt.vn)
Phong Nguyen Duc Department of Paleontology and Stratigraphy, Vietnam Institute of
Geosciences and Mineral Resources (VIGMR), Hanoi, Vietnam (E-mail: phongcs@gmail.com)
Alexander Nützel Bayerische Staatssammlung für Paläontologie und Geologie, Richard WagnerStr. 10, 80333 München, Germany (E-mail: a.nuetzel@lrz.uni-muenchen.de)
Takumi Maekawa Graduate School of Science and Technology, Kumamoto University, 2–39–1
Kurokami, Chuo-ku, Kumamoto 860–8555, Japan (E-mail: 127d9009@st.kumamoto-u.ac.jp)
Yuka Miyake Graduate School of Science and Technology, Kumamoto University, 2–39–1
Kurokami, Chuo-ku, Kumamoto 860–8555, Japan (E-mail: y.m.ctty@gmail.com)
Yasunari Shigeta Department of Geology and Paleontology, National Museum of Nature andScience, 4–1–1 Amakubo, Tsukuba, Ibaraki 305–0005, Japan (E-mail: shigeta@kahaku.go.jp)
Osamu Takahashi Department of Astronomy and Earth Sciences, Tokyo Gakugei University,
4–1–1 Nukuikitamachi, Koganei, Tokyo 184–8501, Japan (E-mail: takahasi@u-gakugei.ac.jp)
Gengo Tanaka BioGeos, Japan Agency for Marine-Earth Science and Technology, 2–15
Natsushima, Yokosuka, Kanagawa 237–0061, Japan (E-mail: gengostra@yahoo.co.jp)
Yukiyasu Tsutsumi Department of Geology and Paleontology, National Museum of Nature andScience, 4–1–1 Amakubo, Tsukuba, Ibaraki 305–0005, Japan (E-mail: ytsutsu@kahaku.go.jp)		vii

Abstract
Reported herein are extensive data resulting from a through investigation of the stratigraphy andpaleontology of the Olenekian Bac Thuy Formation (Lower Triassic) in Lang Son City and the surrounding
Chi Lang District of northeastern Vietnam. The Bac Thuy Formation conformably overlies the siliciclastic
sandstone and mudstone of the Induan to Olenekian Lang Son Formation (Lower Triassic) and isunconformably overlain by rhyolitic rocks of the Middle Triassic Khon Lang Formation. Commonly
divided into three parts, the Bac Thuy Formation consists of a lower part comprised mainly of limestone
and mudstone, a middle part characterized by organic-rich dark gray limestone and an upper part composedof thick mudstone, sandstone and limestone. Its depositional environment consists of tidal flat, waveinfluenced carbonate platform, and slope and marginal basin plain deposits. The intervals of organic-richdark gray limestone and mudstone intercalated in the succession of slope to marginal basin plane facies arecharacterized by monospecific fossil and ichno-fossil assemblages, which suggest anoxic to dysoxic
conditions.
The Bac Thuy Formation is very fossiliferous. Various types of fossils, e.g. cephalopods, gastropods,
bivalves and conodonts, are abundant throughout the sequence, whereas ostracods and radiolarians arepresent only in the middle part. Five distinct ammonoid faunas, the Flemingites rursiradiatus beds,
Urdyceras tulongensis beds, Owenites koeneni beds, Xenoceltites variocostatus beds, Tirolites cf. cassianus
beds and Tirolites sp. nov. beds, as well as three conodont zones, Novispathodus ex gr. waageni Zone,
Novispathodus pingdingshanensis Zone and Triassospathodus symmetricus Zone are recognized inascending order. Based on these ammonoid and conodont occurrences, the formation ranges in age from
Middle Smithian (middle Early Olenekian) to Early Spathian (early Late Olenekian), and the Smithian/Spathian boundary occurs in the organic-rich dark gray mudstone in the middle part of the formation.
Radiometric ages of zircons reveal that the age of the rhyolite in the basal part of the overlying Khon Lang
Formation is 237.7±1.9 Ma, which infers a latest Ladinian to earliest Carnian age.
Ammonoid faunas exhibit a very strong relationship with other Tethyan faunas, but show a relatively
weak relationship with faunas on opposite sides of the Panthalassa. In contrast, Lower Spathian bivalve
occurrences demonstrate probable faunal exchanges between the Tethys and Panthalassa. The gastropod
fauna is characterized only by larvae or early juveniles of taxa displaying a mostly planktotrophic type ofdevelopment, which indicates an unfavourable benthic environment for gastropods. The radiolarian fauna
dominated by entactinarians from the Upper Smithian includes a mixture of Paleozoic and Triassic types.
The ammonoid mode of occurrence suggests that while the supratidal to intertidal environment was
uninhabitable, the majority of ammonoids probably lived in the subtidal flat to storm-wave-influenced
shallow marine environment typical of a carbonate platform. After death their shells were transported fromtheir biotope to the slope to marginal basin plane by gravity flow. Almost all bivalve species were alsotransported more or less from their original habitats to offshore environments. However, epifaunal
Crittendenia and Bositra probably inhabited the hemipelagic deposits of the slope and marginal basin plane
environments, judging from their mode of fossil occurrence and shell preservation.
The limestone in the lower part of the Bac Thuy Formation contains many larval and/or juvenile shellsof gastropods, whose external ornamentation is exceptionally well preserved. Acid treatment of this same
limestone also produced many small ammonoid specimens free of obscuring matrix, thus permitting
observation of the unique three-dimensional geometry of their internal features.
One hundred nineteen taxa (cephalopods: 42, gastropods: 8, bivalves: 5, conodonts: 46, ostracods: 6,
radiorarians: 12) including seven new species (ammonoid: Gaudemandites langsonensis; radiolarians:
Multisphaera triassorobusta, Retentactinia? kycungensis, R.? parvisphaera, Plenoentactinia? terespongia,
Paroertlispongus spinorientalis, ostracoda: Paracypris vietnamensis) are described.
Key words: Ammonoids, Bac Thuy Formation, biostratigraphy, conodonts, Lower Triassic, northeastern
Vietnam, Olenekian, Smithian, Spathian, stratigraphy

viii

ベトナム北東部のオレネキアン階（下部三畳系）層序と化石群（重田康成・小松俊文・前川匠・
Huyen Dang Tran 編）
ベトナム北東部のランソン市とチーラン地域周辺に分布するオレネキアン階（下部三畳系）バ
クトゥイ層について，層序学的研究と古生物学的研究を通して得られた様々な結果を報告する．
バクトゥイ層は，インドゥアン階〜オレネキアン階の珪砕屑性岩類（砂岩や泥岩）より成るラン
ソン層に整合で重なり，中部三畳系コンラン層の流紋岩類に不整合で覆われる．バクトゥイ層は，
主に石灰岩や泥岩によって形成される下部，有機物に富む暗灰色の石灰岩や泥岩で特徴づけられ
る中部，厚い泥岩，砂岩，石灰岩より成る上部に分けられ，干潟，波浪が卓越する炭酸塩プラッ
トフォームの浅海相，陸棚斜面，海盆縁辺の堆積環境から成る．陸棚斜面相から海盆縁辺相に見られる有機物に富む暗灰色の石灰岩や泥岩は，単調な化石群や生痕化石群で特徴づけられ，無酸
素から貧酸素の環境を示す．
バクトゥイ層からは，様々な化石が産出する．頭足類，巻貝類，二枚貝類，コノドント類は，全層準を通して豊富に産出するが，貝形虫類や放散虫類は中部のみから産出する．アンモノイド
化 石 層 は， 下 位 か ら Flemingites rursiradiatus 層，Urdyceras tulongensis 層，Owenites koeneni 層，
Xenoceltites variocostatus 層，Tirolites cf. cassianus 層，Tirolites sp. nov. 層の 5 層が認められた．またコノドント化石帯は，下位から Novispathodus ex gr. waageni 帯，Novispathodus pingdingshanensis
帯，Triassospathodus symmetricus 帯の 3 帯が認められた．これらの化石に基づくと，バクトゥイ層の年代は，スミシアン中期（オレネキアン前期の中頃）〜スパシアン前期（オレネキアン後期の前半）で，スミシアン／スパシアン境界はバクトゥイ層中部の有機物に富む暗灰色泥岩中に位置する．コンラン層最下部の流紋岩中のジルコンの放射年代は，237.7±1.9 Ma であり，ラディニ
アン末期あるいはカーニアン最初期を示す．
バクトゥイ層のアンモノイド化石群は，他のテチス域の化石群と強い関連性を示すが，パンサ
ラッサ海両岸の化石群とは比較的関係性が弱い．一方，スパシアン階下部の二枚貝化石は，テチ
ス域とパンサラッサ域の間での動物群の交流を示す．巻貝化石は，プランクトン栄養型の浮遊幼生あるいは稚貝のみが産出するが，これは海底が巻貝類には好ましくない環境であったことを意味する。スミシアン階上部の放散虫化石群は，Entactinaria 目が優占し，古生代型と三畳紀型の種群が混在する．
アンモノイド化石の産状から，潮上帯〜潮間帯は，生息に不適な環境であり，アンモノイドの大部分は潮下帯〜暴風時に波浪の影響を受ける浅海の炭酸塩プラットフォームに生息していたと考えられる．バクトゥイ層のアンモノイドの多くは，死後，その殻が重力流により生息域から陸
棚斜面や海盆縁辺に運搬されたものである．二枚貝類の多くも生息域から沖合環境へ殻が運搬されたと考えられるが，産状や殻の保存状態から判断して，表在性の Crittendenia や Bositra は陸棚
斜面や海盆縁辺で生息していたと思われる．
バクトゥイ層下部の石灰岩には，表面装飾が例外的に保存良好な巻貝類の幼生や稚貝の殻が多数含まれている．また，酸処理により殻内部の充填物が除去され内部形態の三次元構造が観察可能となった多数の微小なアンモノイド化石を得ることができる．
本 論 文 で は，7 新 種（ ア ン モ ノ イ ド 類：Gaudemandites langsonensis， 放 散 虫 類：Multisphaera
triassorobusta, Retentactinia? kycungensis, R.? parvisphaera, Plenoentactinia? terespongia,
Paroertlispongus spinorientalis，貝形虫類：Paracypris vietnamensis）を含む 119 分類群（アンモノ
イド類：42，巻貝類：8，二枚貝類：5，コノドント類：46，貝形類：6，放散虫類：12）を記載した．
Huyen Dang Tran・Tien Dinh Cong・猪郷久義・Andrzej Kaim・
小松俊文・Huu Nguyen Dinh・Phong Nguyen Duc・Alexander Nützel・
前川匠・三宅優佳・重田康成・高橋修・田中源吾・堤之恭Olenekian (Early Triassic) in northeastern Vietnam

Introduction(by Y. Shigeta, T. Komatsu, H. T. Dang,
T. Maekawa, O. Takahashi, G. Tanaka
and Y. Tsutsumi)
Lower Triassic marine deposits, widelydistributed in northeastern Vietnam, have attracted the attention of many scientists beginning with the early work of pioneering Frenchgeologists and paleontologists. During theearly twentieth century, Jean-Baptiste-Henri
Counillon (1860–1923) and Henri Mansuy(1857–1937) collected various types of Lower
Triassic molluscan fossils in Lang Son Province, and Mansuy (1908) is credited withbeing the first worker to describe ammonoids
from the area. Furthermore, the 1908 work of
Mansuy represents the first description of Triassic ammonoids from the country of Vietnam.
Then in 1940, Professor Josué Heilmann Hoffet (1901–1945), while working at the University of Indochina, (established in 1906, now
the Vietnam National University, Hanoi), collected ammonoids from limestone beds, approximately 24 km southeast of Lang Son City.
During the late twentieth century, Vietnamese paleontologists began investigating
the Lower Triassic outcrops in Lang Son Province and eventually described the ammonoids,
bivalves and conodonts they collected. In
1977, Nguyen Dinh Huu described several important age diagnostic Olenekian ammonoids
from the Na Trang area, near Lang Son City.
Then, in 1980 Vu Khuc erected the Bac Thuy
Formation for the numerous carbonate beds inLang Son Province and later he also describedseveral Olenekian ammonoids from the Bac
Thuy and Na Trang areas (Vu Khuc, 1984,1991). During the period from 1988 to 2005,
Dr. Dang Tran Huyen and Nguyen Dinh Huu
conducted an extensive study of the paleontology and stratigraphy of the formation (Dangand Nguyen K. Q., 2000; Dang and Nguyen,
D. H., 2005; Dang, 2006). Dr. Bui Duc Thang
studied conodonts from the formation and reported typical Smithian (= Early Olenekian)1

conodont assemblages (Bui, 1989). Taken together, these studies reveal that the Lower Triassic of northeastern Vietnam yields numerous
well-preserved fossils from various horizons
within a relatively complete biostratigraphic
sequence.
Similar fossiliferous Lower Triassic deposits also crop out in South China, and theseoutcrops have been extensively studied by various authors beginning with the pioneer works
of Chao (1950, 1959) who first documented
the occurrence of rich Early Triassic ammonoid faunas in northwestern Guangxi. Morerecently, Lehrmann et al. (2001, 2003, 2007a,b) and Galfetti et al. (2008) conducted detailed
studies of the lithofacies and depositional environments of the Lower Triassic in this area.
Brayard and Bucher (2008) and Brühwiler etal. (2008) recognized several Griesbachian toSmithian-aged ammonoid faunas in northwestern Guangxi and constructed a new, very highresolution biostratigraphical zonation, portionsof which can be correlated with various Tethyan localities as well as certain faunal horizonsin the eastern Panthalassic basins. Kaim et al.
(2010) discovered and described a well-preserved Greisbachian gastropod fauna, and
Goudemand et al. (2012) described early Triassic conodont clusters from the area. Chen etal. (2013) reported on the size variation of
conodonts in sediments representing the Smithian/Spathian boundary. These studies havecontributed significantly to achieving an improved understanding of the environment anddynamics of the biotic recovery after the endPermian mass extinction.
In order to better understand the regionalcorrelation and reconstruction of Early Triassic depositional environments, tectonics, biofacies and marine ecosystems in northeastern
Vietnam, Japanese and Vietnamese workers in2005 organized a joint working group under
the leadership of Dr. Toshifumi Komatsu. During the period from 2006 to 2012, various
members of the group conducted several scientific expeditions to Lang Son Province (Fig.

2Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 1. Photographs of the Geologic Museum in Hanoi and major members of the Japanese-Vietnamese Joint
Resaearch Group. 1, Geologic Museum (Bao Tang Dia Chat) in Hanoi, Vietnam. Numerous specimens ofLower Triassic megafossils collected by Vu Khuc and Huu Nguyen Dinh from the Bac Thuy Formation arereposited here. 2, Dr. Huyen Dang Tran, Tien Dinh Cong and Dr. Toshifumi Komatsu. 3, Phuong Nguyen Duc(driver), Huu Nguyen Dinh, Takumi Maekawa, Dr. Yasunari Shigeta and Dr. Huyen Dang Tran at the Bac
Thuy Railway Station. 4, Phong Nguyen Duc.

Olenekian (Early Triassic) in northeastern Vietnam1), where they investigated all geological andpaleontological aspects of the extensive outcrops including lithostratigraphy, biostratigraphy, isotope stratigraphy, sedimentology, paleobiology, and systematic paleontology.
These studies have resulted in several reports, some of which are preliminary in nature. They include descriptions of several Olenekian bivalves (e.g., Crittendenia) by Komatsu et al. (2013), and Komatsu et al. (2014)
have reported that the depositional environment of the Bac Thuy Formation consists
mainly of intertidal, wave and storm dominated shallow marine, slope, and marginal basin
plain deposits. Komatsu et al. (2011) and
Maekawa et al. (2012) have presented preliminary reports in regular meeting of the Palaeontological Society of Japan regarding the Smithian to Spathian conodont, bivalve, and ammonoid assemblages. In order to document theenormous amount of resultant data concerning
the Lower Triassic in northeastern Vietnam, adecision was made to publish a monographwith financial support from the National Museum of Nature and Science with Dr. Yasunari
Shigeta as chief editor. This volume includes asystematic paleontology section for the cephalopods, bivalves, gastropods, conodonts, ostracods and radiolarians collected from the Bac
Thuy Formation, as well as a description of
the formation’s sedimentary environments andthat of the upper part of the underlying Lang
Son Formation. Also included is a section
dealing with the zircon geochronology of theoverlying Khon Lang Formation.
Research methods
Fossil-bearing rock samples were collected following a careful bed-by-bed approachwith special attention devoted to taphonomic
considerations. Megafossils were recoveredfrom host rocks in the laboratory by use of air
tool and/or air abrasion equipment. Siliconcasts were made of specimens consisting onlyof outer molds. Over 100 limestone samples

3

have been examined in an effort to investigate
microfossils. Conodonts and micro gastropods
were removed by applying 5–8% acetic acidto approximately 0.5 to 2 kg sample, then sieving residues (0.177 mm and 1 mm screens) andwashing in water. Radiolarians were extracted
by applying 5% hydrochloric acid to 0.5 kg
samples for 24 hours, then sieving residues(0.300 mm and 0.075 mm screens) and washing in water. Ostracods were removed by applying 5% acetic acid for two weeks, thenwashing in water.
During field work, facies analyses of thebeds were performed based on lithology, sedimentary structures, grain size, paleocurrent
data, and fossil content in order to reconstructdepositional environments. In the laboratory,
we observed the detailed sedimentary structures and fabrics of block samples and also
prepared thin sections for petrographic analysis and observation of microfossils. Sedimentological terminology follows that of Tucker
and Wright (1990), Tucker (1991), Reading
and Collinson (1996), Mulder and Alexander(2001), and Mulder (2011).
Radiometric ages of rhyolite samples wereobtained by zircon U-Pb dating using a Laser
Ablation Inductively Coupled Plasma Mass
Spectrometry (LA-ICP-MS) unit installed at
the National Museum of Nature and Science,
Tsukuba. Procedures for sample preparationand their subsequent analyses for zircon are
the same as those described by Tsutsumi et al.
(2012). The quadrupole ICP-MS is an Agilent
7700x, and the laser ablation system is an ESINWR213. A spot size of 25 μm and laser
power 4–5 J/cm2 were adopted. He gas wasused as the carrier gas instead of Ar gas to enhance a higher transport efficiency of ablatedmaterials (e.g. Eggins et al., 1998). Common
Pb corrections for the concordia diagrams aswell as for each age were made using 208Pb
and 207Pb, respectively (Williams, 1998), on
the basis of the model for common Pb compositions proposed by Stacey and Kramers(1975). The pooled ages presented in this4

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 2. Paleogeographical map of the Early Triassic showing the position of northeastern Vietnam and otherareas. Paleomaps modified after Péron et al., 2005, Brayard et al., 2006 and Brayard et al., 2009. 1: South Primorye, 2: South China, 3: Kamura, Taho and Iwai limestones (Japan), 4: Timor, 5: South Tibet, 6: Spiti, 7:
Salt Range, 8: Madagascar, 9: Oman, 10: Afghanistan, 11: Caucasus, 12: Chios, 13: Albania, 14: Chulitna(Alaska), 15: Nevada, 16: Idaho/Utah, 17: British Columbia, 18: Ellesmere Island, 19: Spitsbergen, 20:
Greenland, 21: Olenek River area.

study were calculated using the Isoplot/Ex
software (Ludwig, 2003).
Repository of specimens
All fossils and rock samples collected during our field work were transported from Vietnam to Japan with permission from the Vietnamese Government and other concerned authorities. All cephalopod, gastropod, ostracodand conodont specimens are reposited at the
National Museum of Nature and Science, Tsukuba. Bivalves are stored in the Faculty of
Science, Kumamoto University, Kumamoto,and radiolarian specimens are stored at Tokyo
Gakugei University, Koganei.
Paleogeographical and geological setting(by T. Komatsu, Y. Shigeta and H. T. Dang)
Tectonic activity of South China and Indochina blocks that probably began in the latePaleozoic continued throughout the Early to
Middle Triassic (Metcalfe, 1998, 2009; Lep-

vrier et al., 2004; Nakano et al., 2008, 2010).
According to Metcalfe (2009), the South
China block originally rifted and separated
from the northern margin of Gondwanaland in
the Devonian and drifted northward in the Triassic. The Indochina craton was deeply subducted beneath the South China craton in the
Early Triassic (Nakano et al., 2010).
In the Early Triassic, the Nanpanjiang and
An Chau basins were widely exposed on theSouth China block (Enos et al., 2006; Lehrmann et al., 2007a, b; Galfetti et al., 2008;
Komatsu et al., 2014). The Nanpanjiang basin
is a vast, shallow to deep marine embayment
in the southern part of the South China block.
During the late Permian to Early Triassic, it
was located in the eastern Tethys seaway near
the equator (Metcalfe, 1998, 2009). The An
Chau basin in Vietnam, which is located in thesouthern part of the South China block (Fig.
2), was continuous with the southeastern Nanpanjiang basin during the Triassic.
In the southwestern part of Guangxi Province, south China, the Nanpanjiang basin sur-

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 3. Map showing the study area and An Chau basin in Lang Son Province, northeastern Vietnam. Studiedsections (BT, KC, NT, PK and BR) are located in the central part of Lang Son Province.

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Shigeta, Komatsu, Maekawa and Dang (eds.)

rounds several large, isolated platforms, including the Chongzuo-Pingguo and Debao
platforms (Lehrmann et al., 2007a, b). In the
Chongzuo area of southwestern Guangxi
Province, the Early Triassic Nanpanjiang basin
is filled with mudstone and debris flow deposits of the Induan to Olenekian Luolou Formation and with isolated shallow marine platform
deposits of the Induan Majiaoling and Induan
to Olenekian Beisi formations (Lehrmann etal., 2007a, b). In Vietnam, the Early Triassic
An Chau basin is filled mainly with marine deposits of the Lower Triassic Lang Son and Bac
Thuy formations and the Middle Triassic volcanic rocks of the Khon Lang Formation.
Komatsu et al. (2014) reported the Olenekian
Bac Thuy Formation is lithologically equivalent to the Luolou Formation in the Nanpanjiang basin.
According to Lehrmann et al. (2007b),
who examined long-term subsidence patterns
during the Proterozoic to Triassic, the Yangtze
platform and other, isolated platforms—including the Chongzuo-Pingguo platform andthe Great Bank of Guizhou—were characterized by high subsidence and sedimentation
rates during the Olenekian to Anisian in the
Chongzuo area; peak subsidence rates occurred earlier in the southern basin (i.e., in the
Pingguo and Chongzuo areas) than in thenorthern basin. During the Olenekian to Anisian, in the Nanpanjiang basin the huge accommodation space was filled with carbonate
and siliciclastic gravity flow deposits. However, the timing and source area of the siliciclastic gravity flows in the southern Nanpanjiangbasin are poorly understood, although Enos etal. (2006) suggested that the Middle Triassic
turbidites originated from the east in association with the Jiangnan uplift in the northernbasin.
In contrast, Lower Triassic siliciclastic
sediments are common in the shallow to deep
marine facies in the An Chau basin (Komatsu
and Dang, 2007; Komatsu et al., 2010, 2014).
According to Komatsu et al. (2014), thick si-

Fig. 4. Stratigraphic subdivisions of the Lower
Triassic System in An Chau basin, northeastern
Vietnam. The Olenekian Bac Thuy Formationconsists of carbonates and siliciclastics.

liciclastic slump deposits accumulated in aslope environment are intercalated within theupper part of the Induan to early Olenekian
Lang Son Formation. Many turbidite beds
consisting of siliciclastics are embedded in the
Olenekian Bac Thuy Formation. Climbing-ripple and current-ripple laminations in high- andlow-density marginal basin turbidites indicate
eastward, northeastward, and southeastward
paleocurrent directions in the Bac Thuy Formation (Komatsu et al., 2014). These observations suggest that the Lower Triassic siliciclastic sediments in the southern Nanpanjiangbasin originated mainly from the shelf in the
An Chau basin or from a landmass in northern
Vietnam. Moreover, it seems that the landmass
was distributed in the western margin of the
An Chau basin.
Stratigraphy of the Bac Thuy Formation(by T. Komatsu, T. Maekawa and Y. Shigeta)
The Bac Thuy Formation was establishedby Vu Khuc (1980), and its stratotype is locat-

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 5. Columnar sections of the Lang Son (upper part) and Bac Thuy formations in the central part of Lang Son
Province.

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Shigeta, Komatsu, Maekawa and Dang (eds.)

ed near the Bac Thuy railway station in the
Bac Thuy area (BT), Chi Lang District, Lang
Son Province. It is also well exposed in the
Pac Khanh (PK), Ban Ru (BR), Na Trang(NT) and Ky Cung River (KC) areas, in thecentral part of Lang Son Province (Fig. 3).
The formation conformably overlies theLower Triassic (Induan to Olenekian) Lang
Son Formation, which consists mainly of siliciclastic sandstone and mudstone in the Na
Trang, Bac Thuy and Ban Ru areas, and it isunconformably overlain by the Middle Triassic Khon Lang Formation, which consists predominately of rhyolitic rocks in these areas(Fig. 4). The Bac Thuy Formation is generally
divided into three parts, namely a lower partconsisting mainly of limestone and mudstone,
a middle part characterized by organic-richdark gray limestone and an upper part composed of thick mudstone, sandstone and limestone (Fig. 5).
Bac Thuy area
Exposures: Two sections, BT01 and BT02,
near the Bac Thuy railway station (stratotype)and one section (BT03) at Na Cong, in Chi
Lang District (Figs. 3, 5–11).
Thickness: 45 m at BT02 (Figs. 5, 8).
Lithology: The lowermost part of the Bac
Thuy Formation (3 m thick) consists of a basal
alternation of thin-bedded limestone andgreenish gray mudstone that is overlain by 2 m
thick interval of fossiliferous bedded limestone (Figs. 6, 9–11). This limestone bed interval, which contains abundant ammonoid shells
and a thin slump bed, is also characterized bysutured stylolite (BT01–03). Although the
middle part of the formation is not well exposed, the upper part is represented by a thickmassive and dominant greenish-gray mudstone containing shelly sandstone layers.
Megafossils: The thin limestone beds ofthe basal limestone/greenish gray mudstonealternation and the lower part of the overlying
fossiliferous limestone beds yield Flemingites

rursiradiatus Chao, 1959, Pseudaspidites muthianus (Krafft and Diener, 1909), Submeekoceras hsüyüchieni (Chao, 1959) and Jinyaceras
cf. bellum Brayard and Bucher, 2008. The
middle part of the fossiliferous limestone beds
intercalated with the thin slump bed contains
Urdyceras tulongensis Brühwiler et al. 2010,
Ussuria kwangsiana Chao, 1959, Galfettites
simplicitatis Brayard and Bucher 2008, Pseudaspidites
muthianus,
Submeekoceras
hsüyüchieni, Jinyaceras cf. bellum, Paranannites sinensis (Chao, 1959) and Aspenites acutus Hyatt and Smith, 1905. Owenites koeneni
Hyatt and Smith, 1905 is the characteristic
ammonoid in the upper part of the 2 m thickfossiliferous limestone beds, but Preflorianites
radians Chao, 1959, Dieneroceras? goudemandi (Brayard and Bucher, 2008), Leyecerasrothi Brayard and Bucher, 2008, Parussuria
compressa (Hyatt and Smith, 1905), Nammalites sp. indet. and Pseudosageceras multilobatum Noetling, 1905a also occur in this interval. Megafossils are not found in the middle
part of the formation. Xenoceltites? sp. indet.,
Tirolites sp. nov., Columbites sp. indet., Yvesgalleticeras? sp. indet. and Eodanubites? sp.
indet. occur in the greenish-gray mudstone of
the upper part. The bivalves, Crittendenia australasiatica (Krumbeck, 1924), “Pseudomonotis” himaica (Bittner, 1899) and Bositra sp.
indet. are also commonly found in the upper
part of the formation.
Microfossils: Microfossils are abundant in
the 2 m thick fossiliferous limestone bed interval in the lower part of the formation, but thebasal thin limestone/mudstone alternation
yields only poorly preserved microfossils.
Conodonts, including Novispathodus ex gr.
waageni (Sweet, 1970b), Conservatella conservativa (Müller, 1956), Discretella discreta(Müller, 1956), and D. robustus (Wang andWang, 1976) are commonly found throughout
the fossiliferous limestone interval. In particular, the lower part of this interval is especiallyrich, yielding various species of conodonts
such as Eurygnathodus costatus Staesche,Olenekian (Early Triassic) in northeastern Vietnam

Fig. 6.

Basal part of the Bac Thuy Formation in BT01, which conformably overlies the Lang Son Formation.

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 7. Distribution of ammonoid, gastropod, and conodont taxa in BT01. Legend is shown in Fig. 5. Nvw:
Novispathodus ex gr. waageni Zone, Fr: Flemingites rursiradiatus beds, Ut: Urdyceras tulongensis beds, Ok:
Owenites koeneni beds.

Olenekian (Early Triassic) in northeastern Vietnam

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 8. Distribution of ammonoid, gastropod, bivalve, and conodont taxa in BT02. Legend is shown in Fig. 5.
Nvw: Novispathodus ex gr. waageni Zone, Fr: Flemingites rursiradiatus beds, Ut: Urdyceras tulongensis
beds, Ok: Owenites koeneni beds, Xv: Xenoceltites variocostatus beds, T: Tirolites sp. nov. beds.

Olenekian (Early Triassic) in northeastern Vietnam

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 9. Alternating thin-bedded limestone and mudstone and 2 m thick fossiliferous bedded limestone interval in
the basal part of the BacThuy Formation in BT01. 1, 2 m thick bedded limestone interval containing abundantammonoids, gastropods and conodonts. 2, Bedding plane in the 2 m thick fossiliferous bedded limestone interval at BT01-09. Many ammonoid sections are visible.

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 10. 1, 2 m thick fossiliferous bedded limestone interval containing abundant ammonoids in the basal part ofthe Bac Thuy Formation in BT03. Scale is 20 cm. 2, Bedding plane in the ammonoid supported shell-concentration in the 2 m thick fossiliferous bedded limestone interval.

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 11. Bedding plane in the ammonoid supported shell-concentration in the 2 m thick fossiliferous bedded
limestone interval in the basal part of the Bac Thuy Formation in BT03. Owenites koeneni and Preflorianites
radians occur abundantly in the ammonoid supported shell-concentration.

Olenekian (Early Triassic) in northeastern Vietnam

1964, Neospathodus aff. concavus Zhao andOrchard, 2007, Ns. cristagalli (Huckriede,1958), Ns. dieneri Sweet, 1970a, Ns. novaehollandiae McTavish, 1973, Ns. pakistanensis
Sweet, 1970b, Ns. posterolongatus Zhao andOrchard, 2007 and Ns. spitiensis Goel, 1977.
The middle part of the limestone bed interval is intercalated with a slump bed containing
the conodonts, Ns. dieneri, Ns. novaehollandiae, Ns. spitiensis, Guangxidella bransoni(Müller, 1956), Smithodus longiusculus(Buryi, 1979), and two species of Hadrodontina?, as well as the gastropods Worhtenia? sp.
indet., Atorcula sp. indet. and Naticopsis sp.
indet. A.
The upper part of the limestone bed interval yields the conodont Guangxidella bransoni, and the gastropods Anomphalus? sp. indet.,
Abrekopsis sp. indet., Strobeus sp. indet., Ampezzopleura sp. indet. Atorcula sp. indet. andNaticopsis sp. indet. A and B. Microfossils are
not found in the middle and upper parts of theformation.
Ky Cung River
Exposures: Two sections, KC01, 02 along
the Ky Cung River near Na Pan, in Lang Son
City (Figs. 3, 5, 12–16)
Thickness: Greater than 100 m (Figs. 5, 12,
15).
Lithology: The lower part of the formation(95 m thick), which is poorly exposed in thisarea, consists of limestone breccias, bedded
limestone, carbonate slump beds and greenish
gray mudstone (Figs. 13, 14, 16). Embeddedin the basal part at KC01 are 4 m thick typicalshallow marine carbonates consisting of oolites, lenticular to wavy beddings, tidal bundles containing mud drapes and cross-stratified limestone. Thin bivalve shells and smallammonoids commonly occur in the oolitic
limestone and cross-stratified limestone, anddesiccation cracks are typically found in thelenticular to wavy bedding (Komatsu et al.,2014). The middle part of the formation (3 m

17thick) is characterized by organic-rich darkgray thin-bedded limestone yielding abundantradiolarians and bivalves, and mudstone containing dark gray calcareous nodules. The
upper part of the formation (12 m thick) consists of thick mudstone intercalated with limestone breccias, thin bedded limestone, thin turbidite beds and sandstone/mudstone alternations. Ammonoid and bivalve shell lag deposits, and cross- and parallel-laminations characterize the thin turbidite beds.
Megafossils: Ammonoids are common in
the limestone breccias and bedded limestone
in the lower part of the formation. Owenites
koeneni and Dieneroceras? goudemandi aredominant, but other taxa are also found in two
different horizons as follows: Juvenites sinuosus (Kiparisova, 1947), Paranannites sinensis,
Preflorianites radians, Leyeceras rothi, Anaflemingites hochulii Brayard and Bucher, 2008,
Parussuria compressa and Aspenites acutus in
the lower portion, and Guodunites monneti
Brayard and Bucher, 2008 in the upper portion. The organic-rich dark gray carbonate
beds in the middle part of the formation contain the following megafossils: ammonoid–Xenoceltites variocostatus Brayard and Bucher,2008 and bivalves–abundant Crittendenia australasiatica, rare Crittendenia langsonensis
Komatsu and Dang, 2013 and Bositra limbata(Guo, 1985).
The upper part of the formation yields thebivalves–Crittendenia australasiatica, Leptochondria bittneri (Kiparisova, 1938), “Pseudomonotis” himaica, Bositra limbata and Bositra sp. indet. and ammonoids, whose shells
form thin lenticular shell concentrations (Figs.
17–19). Ammonoid composition changes toward the upward sequence within the upper
part of the formation. Tirolites cf. cassianus(Quenstedt, 1849) is common in the greenishgray mudstone of the lower portion, while Tirolites sp. nov., Columbites sp. indet., Yvesgalleticeras? sp. indet. are abundant in the middle portion. Also occurring in the middle portion are Procarnites? sp. indet., Eodanubites?

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 12. Distribution of ammonoid, gastropod, and conodont taxa in KC01. Legend is shown in Fig. 5. Nvw:
Novispathodus ex gr. waageni Zone, Ok: Owenites koeneni beds.

Olenekian (Early Triassic) in northeastern Vietnam

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 13. Exposures of the lower part of the Bac Thuy Formation along a tributary of the Ky Cung River in
KC01. 1, Limestone breccia, slump bed and bedded limestone. 2, Secondarily deformed bedded limestone(slump bedding).

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 14. Exposures of the lower part of the Bac Thuy Formation along a tributary of the Ky Cung River in
KC01. 1, Outcrop showing the fault contact between shallow marine limestone of the Bac Thuy Formation
and underlying Lang Son Formation in KC01. 2, Shallow marine carbonate lithofacies.

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 15. Distribution of ammonoid, gastropod, bivalve, conodont, and radiolarian taxa in KC02. Legend isshown in Fig. 5. Nvw: Novispathodus ex gr. waageni Zone, Nvp: Novispathodus pingdingshanensis Zone,
Trs: Triassospathodus symmetricus Zone, Ok: Owenites koeneni beds, Xv: Xenoceltites variocostatus beds,
Tc: Tirolites cf. cassianus beds, T: Tirolites sp. nov. beds.

Olenekian (Early Triassic) in northeastern Vietnam

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 16. Exposures of the lower and middle parts of the Bac Thuy Formation in KC02. 1, Limestone breccia,
thin-bedded limestone and thick mudstone cropping out along the Ky Cung River. The Smithian/Spathianboundary is intercalated in alternating organic-rich dark gray bedded limestone and mudstone at KC02-10 and
KC02-11. 2, Thick limestone breccia containing intraclasts composed mainly of oolitic and bioclastic shallow
marine limestone and thin-bedded hemipelagic limestone.

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 17. Shell concentration (KMSP-5138) consisting of “Pseudomonotis” himaica and Crittendenia australasiatica in the Td division of a thin turbidite layer in thick hemipelagic mudstone at KC02-15. Disarticulatedshells are scattered on the basal erosive surface of the low-density turbidite layer.

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 18.

Early Spathian ammonoids in a low-density turbidite layer from KC02-14.

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 19.

Early Spathian ammonoids in a low-density turbidite layer from KC02-14.

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Shigeta, Komatsu, Maekawa and Dang (eds.)

sp. indet. and Goudemandites langsonensis
Shigeta and Nguyen sp. nov. Only rare specimens of Eodanubites? sp. indet. occur in thegreenish-gray mudstone in the upper portion.
Microfossils: The bedded limestone in thelower part of the formation contains abundantmicrofossils as follows: conodonts–Novispathodus ex gr. waageni, Ns. dieneri, Ns. novaehollandiae, Ns. posterolongatus, Ns. spitiensis,
Discretella discreta, D. robustus, Guangxidella bransoni, and Smithodus longiusculus, gastropods–Worhtenia? sp. indet., Anomphalus?
sp. indet., Atorcula sp. indet. and Naticopsis
sp. indet. A and B.
In the middle part of the formation, thedark gray thin-bedded limestone and calcareous nodules contain the following fossils: conodonts–Novispathodus ex gr. waageni, Nv.
pingdingshanensis (Zhao and Orchard, 2007),
Nv. sp. nov. A Goudemand and Orchard, 2012,
and Icriospathodus? zaksi (Buryi, 1979),
abundant radiolarians–Multisphaera triassorobusta Takahashi, sp. nov., Retentactinia? kycungensis Takahashi, sp. nov., R. parvisphaera
Takahashi, sp. nov., Plenoentactinia? terespongia Takahashi, sp. nov., Spongentactinia?
sp. indet., Pentactinocarpus? aff. acanthicus
Dumitrica, 1978, Triassothamnus verticillatus(Dumitrica, 1978), Tandarnia recoarensis Dumitrica, 1982 and Paroertlispongus spinorientalis Takahashi, sp. nov., gastropod–Anomphalus? sp. indet.
In the upper part of the formation, the thinbedded limestone and thin layered shell concentrations contain conodonts as follows:
abundant Novispathodus triangularis (Bender,1970), Triassospathodus homeri (Bender,1970), T. symmetricus (Orchard, 1995), Icriospathodus collinsoni (Solien, 1979), and rareI.? crassatus (Orchard, 1995) and Nv. pingdingshanensis.
Na Trang area
Exposures: Five sections, NT01–05
around Na Trang Village, in Lang Son City

(Figs. 3, 5, 20–22)
Thickness: 50 m (Figs. 5, 21).
Lithology: The lower part of the formation(20–26 m thick, NT01–04) consists of thickgreenish gray mudstone, limestone breccias
and thin bedded limestone. The 0.2–4 m thicklimestone breccias, characterized by structureless clast- or matrix supported textures, exhibit
typical channel-like bodies. The middle part
(6 m thick) is dominated by organic-rich darkgray thin-bedded limestone, mudstone andsandstone. Organic-rich dark gray calcareous
nodules are abundant in the dark gray mudstone. These dark gray carbonates yield abundant radiolarians, and commonly containmonospecific ammonoids and bivalves. The
sandstone is characterized by normal and inverse-grading, cross- and convolute-laminations. The upper part of the formation (18 mthick) is composed of thick greenish graymudstone overlain by 3 m thick alternations ofsandstone and mudstone (Fig. 22). The thickmudstone portion is commonly intercalatedwith thin shelly sandstone layers. The sandstone/mudstone alternations contain climbing
ripples, parallel- and convolute-laminations.
At NT05 the upper part is intercalated withlimestone breccias and thin bedded limestone.
Megafossils: Fossils have not been foundin the lower part of the formation, but the following megafossils have been collected fromthe organic-rich dark gray carbonates in the
middle part: ammonoid–Xenoceltites variocostatus, nautiloid–Trematoceras sp. indet.,
and bivalves–abundant Crittendenia australasiatica, rare Crittendenia langsonensis, and a
fragment of Leptochondria bittneri. The
greenish-gray mudstone in the upper part contains the following ammonoids: Tirolites sp.
nov., Columbites sp. indet. and Eodanubites?
sp. indet., noutiloid–Trematoceras sp. indet.,
and the bivalves–Crittendenia australasiatica,
Leptochondria bittneri, “Pseudomonotis” himaica and Bositra sp. indet.
Microfossils: In the middle part of the formation, the organic-rich dark gray thin-bedded

Fig. 20. Route map in the Na Trang area (NT01, 02, 03). The upper part of the Lang Son, Bac Thuy and Khon Lang formations are widely distributed in the area. The alternatingorganic-rich dark gray bedded limestone and mudstone contains abundant bivalves, ammonoids and radiolarians (NT01-01–09). The Spathian ammonoids, Tirolites andColumbites, are commonly found in thin turbidite layers (NT01-10, NT01-11).

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 21. Distribution of nautiloid, ammonoid, gastropod, bivalve, conodont, ostracoda and radiolarian taxa in
NT01. Legend is shown in Fig. 5. Nvp: Novispathodus pingdingshanensis Zone, Xv: Xenoceltites variocostatusbeds, T: Tirolites sp. nov. beds.

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 22. Exposures of the upper part of the Bac Thuy Formation in NT01. 1, Hemipelagic mudstone intercalatedwith turbidite layers that contain abundant ammonoids and bivalves. 2. Outcrop showing unconformity between the Bac Thuy Formation consisting mainly of concentrated density flow to turbidity flow deposits andoverlaying volcanic rocks of the Khon Lang Formation in NT01.

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Fig. 23. Distribution of ammonoid and conodont taxa in PK01. Legend is shown in Fig. 5. Nvw: Novispathodus
ex gr. waageni Zone, Ok: Owenites koeneni beds.

limestone contains rare conodonts–Novispathodus pingdingshanensis, Novispathodus sp.
nov. A, and Icriospathodus? zaksi, abundantradiolarians–Retentactinia? kycungensis Takahashi, sp. nov., Parentactinia nakatsugawaensis Sashida, 1983, P. cf. pugnax Bumitrica, 1978, and Paroertlispongus spinorientalis
Takahashi, sp. nov., and ostracods–two speciesof Bairdia.
Pac Khanh area
Exposures: One section, PK01, in Chi
Lang District (Figs. 3, 5, 23, 24)
Thickness: Greater than 14 m (Figs. 5, 23).
Lithology: The lower part of the formation, which is poorly exposed in this area, consists mainly of limestone breccia, bedded
limestone with abundant ammonoid shells,
and greenish gray mudstone (Figs. 24). Ammonoid composition and mode of occurrencein the bedded limestone are quite similar to
those of the ammonoids in the lower part ofthe Bac Thuy section stratotype. The middle
part of the formation (2 m thick) is characterized by sandstone and dark gray mudstone
containing organic-rich calcareous nodules.
The upper part of the formation in the Pac
Khanh section is distinguished by alternating
sandstone and mudstone whose lithology resembles that of the uppermost Na Trang(NT01) and Ky Cung River (KC02) sections.
Megafossils: Because of the difficulty encountered in collecting macrofossils from theunusually hard limestone breccias and bedded
limestone, only the ammonoid Owenites koeneni is recognized in the lower part of the formation. Megafossils have not been found in
the middle and upper parts of the formation.
Microfossils: The conodonts, Discretella
discreta and Guangxidella bransoni occur
commonly in the bedded limestone in thelower part of the formation.

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 24.

Fossiliferous bedded limestone containing abundant ammonoids in the Bac Thuy Formation in PK01.

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Fig. 25. Distribution of ammonoid, bivalve, conodont, and ostracoda taxa in BR01. Legend is shown in Fig. 5.
Nvp: Novispathodus pingdingshanensis Zone, Xv: Xenoceltites variocostatus beds, T: Tirolites sp. nov. beds.

Olenekian (Early Triassic) in northeastern Vietnam

Ban Ru area
Exposures: One section, BR01, in Chi
Lang District (Figs. 3, 5, 25)
Thickness: Greater than 185 m by Dang
(2006). However, the lower part of the section
was not closely examined (Figs. 5, 25).
Lithology: The lower part of the formationis composed mainly of mudstone, limestone
breccias and bedded limestone, while the middle part of the formation (13 m thick) consists
predominately of dark gray organic-rich thinbedded limestone and mudstone containing
dark gray calcareous nodules that commonly
yield ostracods and bivalves. Lithologically,
the middle part of the Ban Ru section closely
resembles the middle parts of the Na Trang(NT01) and Ky Cung (KC02) sections. The
upper part of the section (30 m thick), dominated by thick greenish gray mudstone, is lithologically similar to the upper parts of the Bac
Thuy (BT02) and Na Trang (NT01) sections.
Taken together, the thickness of the middle
and upper parts of the Ban Ru (BR01) section
exceeds 40 m, which is much thicker than thesame intervals in the other section.
Megafossils: Megafossils have not beenfound in the lower part of the formation, but
the ammonoid Xenoceltites variocostatus andbivalve Crittendenia australasiatica are quite
common in the middle part. The upper part of
the formation yields rare specimens of the ammonoid Columbites sp. indet., and bivalves
Crittendenia australasiatica, Bositra limbata
and “Pseudomonotis” himaica.
Microfossils: The organic-rich dark graythim-bedded limestone in the middle part of
the formation yields rare conodonts including
Novispathodus pingdingshanensis, Icriospathodus? zaksi, as well as fragments of conodontelements. Also found are abundant ostracods,
Paracypris vietnamensis Tanaka and Komatsu
sp. nov. and Paracypris sp. A. Microfossils
have not been found in the lower and upperparts of the formation.

35

Depositional environments of
the Bac Thuy Formation(by T. Komatsu, T. Maekawa, Y. Shigeta,
H. T. Dang and P. D. Nguyen)
Depositional environments of the Triassic
systems in the An Chau basin have been documented by Komatsu and Dang (2007), Komatsu et al. (2010) and Komatsu et al. (2014).
The Olenekian stage in this basin, consistingof the upper part of the Lang Son and Bac
Thuy formations, is composed of mixed carbonate and siliciclastic shallow marine to marginal basin deposits (Fig. 26). Dominated bysiliciclastic facies, the upper part of Lang Son
Formation is composed mainly of storm andwave-influenced shallow marine deposits,characterized by wave ripples and hummocky
cross-stratification as well as slope deposits(Komatsu and Dang, 2007; Komatsu et al.,2014). According to Komatsu et al. (2014), theBac Thuy Formation consists of a tidal flat,wave-influenced carbonate platform, and slopeand marginal basin plain deposits (Fig. 26).
The lower part of Bac Thuy Formation is locally intercalated with tidal deposits andwave-influenced shallow marine carbonates at
KC01 (Figs. 27–31). The tidal flat deposits arecomposed mainly of lenticular and wavy bedding with thin flat-bedded carbonates containing desiccation cracks (Fig. 27). Current ripples in the lenticular and wavy bedding exhibit
bi-directional paleocurrents. These tidal deposits are intercalated with cross-stratified
limestone characterized by tidal bundle carbonates containing mud drapes. The tidal bundles may have accumulated in response to migration of sand bars formed by tidal currents
in intertidal to subtidal zones (Dalrymple,
1992, 2010). Desiccation cracks containing
tepee structures are generally formed on the
supratidal and upper intertidal zones in arid tosemiarid environments (Wright 1990; Wrightand Burchette, 1996; Pratt, 2010). The subtidal
carbonates yield poorly preserved bivalves,ammonoids and conodonts (Figs. 28, 30, 31).

36

Shigeta, Komatsu, Maekawa and Dang (eds.)

The shallow marine carbonates containwave-ripples, low-angle cross-stratification(hummocky cross-stratification?, Fig. 29),
ooids and abundant typical marine mollusks
and microfossils (Figs. 29–31). The Smithianconodont, Novispathodus waageni (= Neospathodus waageni), is common in the shallow marine carbonates (Fig. 12). Marine molluscan fossil assemblages are characterized byabundant small bivalves and Smithian ammonoids such as Owenites koeneni. These thin bivalve shells typically show an edgewise arrangement (i.e., flat shells arranged perpendicular to the bedding, Kidwell et al., 1986) generated by strong wave currents (Fig. 31). Cyclic tidal deposits and wave-influenced shallow marine carbonates consist of typical retrogradational parasequence sets suggestingtransgressive sequences (Komatsu et al.,2014). These tidal and wave influenced deposits were probably accumulated in a typicalshallow marine environment on an isolated
carbonate platform.
Slope and marginal basin-plain deposits,
dominant in the upper part of Bac Thuy Formation, are widely distributed in Lang Son
Province (BT02, KC02, NT01–05, PK01,
BR01, in Figs. 32–35). These slope deposits
are characterized by limestone breccias, highdensity turbidites, slump beds and hemi-pelagic mudstone and limestone (Komatsu et al.,2014). Abundant concentrations of ammonoid
shells, associated with limestone breccias or
slump beds, are embedded in slope deposits(BT01–03, PK01).
Marginal basin-plain deposits consist of
typical turbidite beds, minor limestone breccias and thick hemipelagic mudstone containing marl layers. These marl layers yield the
Spathian ammonoids Tirolites and Columbites,
the bivalve Leptochondria bittneri and conodonts Triassospathodus and Icriospathodus.
The classical turbidite sets may represent frontal splay environments in the marginal basin
plain. Clastics apparently were supplied fromthe west, hence the paleocurrent directions of

the siliciclastic gravity flow deposits were approximately eastward (Komatsu et al., 2014).
These Olenekian carbonate and siliciclastic facies in the Bac Thuy Formation exhibit a typical transgressive succession.
The Smithian/Spathian boundary and latest Smithian anoxic to dysoxic facies, characterized by organic-rich dark gray bedded limestone and mudstone, are embedded in a succession ranging from slope to marginal basinplain facies composed mainly of gravity flow
and hemipelagic deposits (Komatsu et al.,2014). The uppermost part of the organic-richmudstone bed is intercalated with the Smithian/Spathian boundary as indicated by the first
appearance of Tilorites cf. cassianus (KC02,
NT01). The anoxic to dysoxic facies, composed of dark gray radiolarian and molluskshell bioclastic wackestone and dark graymudstone, is characterized by rare bioturbation, small pyrite crystal aggregates and richorganic matter. The pyrite aggregates werepossibly generated under anoxic sediments
and/or under stagnant water conditions. The
organic-rich dark gray mudstones containweakly parallel and cross-laminations, and areintercalated with so-called high density turbidite beds characterized by massive, normal
and inverse graded coarse grained calcareous
sandstones (Fig. 34). Very small grazing traces(pascichnia), such as Spirophycus isp. andPhycosiphon isp. are commonly found insome layers (Fig. 29). These ichnofossil assemblages, dominated by pascichnia and characterized by low diversity and moderately
high density, indicate opportunistic producers(Bromley, 1996). Ekdale and Mason (1988)
proposed that pascichnia-dominated trace fossil assemblages were formed under less oxygenated conditions than domichnia-dominatedassemblages, suggesting anoxic to dysoxic
conditions.
The organic-rich carbonates and mudstoneyield abundant low-diversity molluscan fossils
and microfossils. Microfossil assemblages aremainly composed of spheroidal radiolarians

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 26.

Sedimentary facies and depositional environments. Modified from Komatsu et al. (2014).

37

38

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 27. Vertical cross sections of slabs from KC01. These deposits are interpreted to have accumulated in a tidal
flat environment (Komatsu et al., 2014). 1, Alternating thin flat-bedded limestone and mudstone. 2, Intraclastic limestone containing tepee structures and desiccation cracks. Upper part of the slab is characterized by reworked desiccation clasts.

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 28. Shallow marine carbonate lithofacies in KC01. 1, Bioclastic, oolitic and intraclastic limestone containing abundant thin-shelled bivalves and ammonoids at KC01-05. 2, Bioclastic, oolitic and intraclastic limestone at KC01-03.

39

40

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 29. 1–3, Vertical cross sections of shallow marine limestone slabs from KC01. 1, Intraclastic, oolitic, andbioclastic limestone from KC01-03. 2, Intraclastic limestone showing normal grading from KC01-09. 3, Lowangle cross-stratified limestone (hummocky cross-stratified limestone?) from KC01-05. 4, Vertical cross section of hemipelagic limestone slab from PK01. Bioclastic limestone contains ammonoid (arrows) and bivalve
shells. The ammonoid shells show geopetal structures. 5, Laminated organic-rich dark gray mudstone from
NT01. 6, Laminated organic-rich dark gray limestone containing small burrows in KC02 overlying well-laminated organic-rich black lime mudstone. 7, Calcareous sandstone showing normal grading and weakly bioturbated organic-rich, black lime mudstone containing tiny ichnofossils, Spirophycus isp. in NT01.

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 30. Photomicrographs of vertical thin sections. 1–2, Bioclastic limestone containing juvenile ammonoids
from KC01-03. 3–4, Oolitic limestone from KC01-08. 5–6, Bioclastic limestone containing fragmental anddisarticulated thin-shelled bivalves from KC01-08. Thin-shelled bivalves are arranged edgewise and perpendicular to the bedding, which indicates formation by strong wave currents.

41

42

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 31. Photomicrographs of vertical thin sections. 1–2, Bioclastic limestone containing thin-shelled bivalves
and juvenile ammonoids from BT01-14. 3, Sutured stylolites commonly found in hemipelagic limestone from
KC01-14. 4, Organic-rich dark gray calcareous nodule containing abundant spheroidal radiolarians fromNT01-07. 5, Organic-rich dark gray limestone containing abundant spheroidal radiolarians from KC02-10. 6,
Organic-rich dark gray calcareous nodule containing abundant spheroidal radiolarians and ostracods fromBR01-05.

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 32. Lithofacies of slope deposits. 1, Exposures of isolated channel-filling limestone breccias in hemipelagic
mudstone in NT02. 2, Limestone breccia containing slump beds and overlying thin-bedded marl at KC02-03.

43

44

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 33. Lithofacies of slope deposits in KC02. 1, Limestone breccia characterized by matrix- and clast-supports.
2, Clast-supported limestone breccia containing pebble and cobble intraclasts.

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 34. 1–2, Fossiliferous bedded limestone in PK01. 1, Fossiliferous bedded limestone overlain by thin-bedded
limestone (T. B. L) and limestone breccia (L. B.). 2, Fossiliferous bedded limestone containing abundant ammonoids (e.g. Owenites koeneni) at PK01-02. 3–4, Exposures of gravity flow deposits in NT01. 3, Gravelly
and very coarse calcareous sandstone displaying normal and inverse grading. 4, Convolute- and parallel laminated calcareous sandstone and mudstone. The basal part of the calcareous sandstone occasionally contains
flame structures.

45

46

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 35. Vertical cross sections of sandstone in the upper part of the Bac Thuy Formation. 1–2, Very fine siliciclastic sandstone contains climbing-ripple lamination from NT01. 3, Thin calcareous turbidite characterized
by Tc and Td divisions is embedded in thick hemipelagic mudstone at KC02-15.

Olenekian (Early Triassic) in northeastern Vietnam

and poorly ornamented ostracods (Fig. 31).
Komatsu et al. (2011, 2013) reported a monospecific ammonoid assemblage composed of
Xenoceltites variocostatus and a thin-shelled
epifaunal bivalve assemblage consisting mainly of Crittendenia australasiatica from this facies. In the Ban Ru area, a low diversity ostracod assemblage from the organic-rich darkgray bedded limestone is composed of several
species of Paracypris of which Paracypris
vietnamensis and Paracypris sp. A are abundant. A similar low diversity assemblage exists
in the same lithologic unit in the Na Trangarea, in which only two species of Bairdia arecommon.
Biostratigraphy
Ammonoid succession (by Y. Shigeta)
Based on carefully controlled bed-by-bed
sampling, a total of five distinct Olenekian(Smithian and Spathian) ammonoid faunas arerecognized in the studied area (Fig. 36). Thesefaunas, ranging in age from the earliest Middle
Smithian through the Early Spathian, represent
a more or less continuous succession that canbe correlated with other Tethyan sequencessuch as the Salt Range (Pakistan), Spiti(India), Tulong (South Tibet), Oman andSouth China as well as the eastern Panthalassa. Formal zones are not introduced forthese assemblages because fossil occurrences
are not stratigraphically continuous and ourknowledge of Early Triassic ammonoid faunas
in northeastern Vietnam is only in a preliminary stage. Hence, the term “beds” is used todescribe each of the local faunal sequences.
Flemingites rursiradiatus beds: Thesebeds, of earliest Middle Smithian age (Brayard
et al., 2013), are well-documented from thelower part of the fossiliferous limestone bedsin the basal portion of the Bac Thuy Formation in exposures at Bac Thuy (sections BT01,
02). Flemingites rursiradiatus as well as Pseudaspidites
muthianus,
Submeekoceras
hsüyüchieni and Jinyaceras cf. bellum all co-47

occur in these beds. This fauna correlates withthat from the Flemingites rursiradiatus beds inGuangxi, South China (Brayard and Bucher,2008) and Oman (Brühwiler et al., 2012a), as
well as the Flemingites beds in Spiti (Brühwiler et al., 2012c), Flemingites flemingianus
beds of the Salt Range (Brühwiler et al.,2012b) and Flemingites sp. beds of Utah, USA(Brayard et al., 2013).
Urdyceras tulongensis beds: This subdivision, which occurs in the middle part of thebasal portion of the Bac Thuy Formation in
exposures at Bac Thuy (sections BT01, 02), ischaracterized by the association of Urdycerastulongensis, Ussuria kwangsiana, Galfetites
simplicitatis, Pseudaspidites muthianus, Submeekoceras hsüyüchieni, Jinyaceras cf. bellum, Paranannites sinensis and Aspenites acutus.
Recently, Brühwiler et al. (2010) documented the occurrence of Urdyceras tulongensis in the Brayardites compressus beds (lower
Middle Smithian) at Tulong, South Tibet, andsince an equivalent fauna is not known fromSouth China, Brühwiler et al. (2010, 2012c)
pointed out that the Brayardites compressus
beds can probably be correlated with an interval between the Flemingites rursiradiatus
beds and the Owenites koeneni beds of South
China. Although Brayardites compressus
Brühwiler et al., 2010 has not yet been foundin northeastern Vietnam, the occurrence of U.
tulongensis supports the suggestion of Brühwiler et al. (2010, 2012c). Therefore, this subdivision is considered to be of early Middle
Smithian age.
Owenites koeneni beds: This subdivisionoccurs in the upper part of the basal portion of
the Bac Thuy Formation in the Bac Thuy sections (BT01, 02) and the Pac Khanh section(PK01) as well as in limestone breccia andbedded limestone in the lower portion of the
Bac Thuy Formation exposed along the Ky
Cung River (sections KC01, 02). These beds
are mainly characterized by Owenites koeneni
and Dieneroceras? goudemandi, but other taxa

48

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 36. Ammonoid and conodont biostratigraphic subdivision of the Lower Triassic of northeastern Vietnumand correlation with other regions. N. p.: Novispathodus pingdingshanenesis, T. s.: Triassospathodus symmetricus.

Olenekian (Early Triassic) in northeastern Vietnam

49

50

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 37.

Distribution of index ammonoid taxa in the Bac Thuy Formation.

Olenekian (Early Triassic) in northeastern Vietnam

are also found at two different horizons as follows: Preflorianites radians, Leyeceras rothi,
Anaflemingites hochulii, Juvenites sinuosus
and Parussuria compressa in the lower part
(Leyeceras horizon), and Guodunites monneti
in the upper part (Guodunites horizon).
In Guangxi, South China, Brayard and Bucher (2008) subdivided the Middle SmithianOwenites koeneni beds into three horizons inascending order as follows: Ussuria, Hanielites and Inyoites horizons. The Leyeceras
horizon, of middle Middle Smithian age, probably can be correlated with the Ussuria andHanielites horizons as well as the Nammalites
pilatoides beds in the Salt Range (Brühwiler etal., 2012b), Spiti (Brühwiler et al., 2012c) and
Tulong (Brühwiler et al., 2010). The Guodunites horizon, of late Middle Smithian age, correlates with the Inyoites horizon of South
China and Utah, USA (Brayard et al., 2013),
the Meekoceras gracilitatis Zone in Nevada,
USA (Jenks et al., 2010) and the Nyalamites
angustecostatus beds in the Salt Range (Brühwiler et al., 2012b), Spiti (Brühwiler et al.,2012c) and South Tibet (Brühwiler et al.,2010).
Xenoceltites variocostatus beds: Thesebeds, which are well-documented from the
middle portion of the Bac Thuy Formation(sections NT01, KC02, BT02, BR01), arecharacterized by the unique occurrence of Xenoceltites variocostatus. This subdivision is
middle to late Late Smithian in age, because
X. variocostatus occurs in the upper part of theAnasibilites multiformis beds in Guangxi,
South China (Brayard and Bucher, 2008), theGlyptophiceras sinuatus beds of South Tibet(Brühwiler et al., 2010) and the Salt Range(Brühwiler et al., 2012b) and the Subvishnuites posterus beds in Spiti (Brühwiler et al.,2012c).
Tirolites cf. cassianus beds: Of earliest
Early Spathian age, these beds are well-documented in the upper portion of the Bac Thuy
Formation exposed along the Ky Cung River(section KC02). Also found with Tirolites cf.

51

cassianus are Pseudosageceras sp. and Xenoceltites? sp. Tirolites cassianus has long beenrecognized as one of the more important agediagnostic species of the earliest Early Spathian in the Tethys (Krystyn, 1974; Posenato,
1992).
Tirolites sp. nov. beds: This subdivision, ofEarly Spathian age, occurs in the upper portion of the Bac Thuy Formation (sections
NT01, KC02, BT02, BR01). Its fauna is characterized by the association of Tirolites sp.
nov., Columbites sp., Xenoceltites? sp., Yvesgalleticeras? sp., Procarnites? sp., Eodanubites? sp. and Goudemandites langsonensis sp.
nov. Tirolites and Columbites are typical agediagnostic taxa of the Early Spathian (Kummel, 1969; Guex et al., 2010).
Conodont succession (by T. Maekawa and T.
Komatsu)
The Lower Triassic section in the northeastern Vietnam can be divided into three conodont zones in ascending order as follows:
Novispathodus ex gr. waageni Zone, Novispathodus pingdingshanensis Zone, and Triassospathodus symmetricus Zone (Fig. 36).
Novispathodus ex gr. waageni Zone: This
zone begins with the first occurrence of Novispathodus ex gr. waageni and ends with thefirst occurrence of Nv. pingdingshanensis. The
following taxa are associated: Conservatellaconservativa, C. sp. indet. A, Discretella discreta, D. robustus, D. sp. indet. A through G,
Guangxidella bransoni, G. sp. indet. A, G. sp.
indet. B, Eurygnathodus costatus, Neospathodus aff. concavus, Ns. cristagalli, Ns. dieneri,
Ns. novaehollandiae, Ns. pakistanensis, Ns.
posterolongatus, Ns. spitiensis, Ns. sp. indet.
A, Ns. sp. indet. B, Ns. sp. indet. C, Smithodus
longiusculus, Novispathodus pingdingshanensis, Hadrodontina? sp. indet. A, and H.? sp.
indet. B. The Zone encompasses the Flemingites rursiradiatus, Urdyceras tulongensis,
Owenites koeneni, and part of the Xenoceltites
variocostatus ammonoid beds in the Bac Thuy
Formation. Conodonts are abundant in the in-52

Shigeta, Komatsu, Maekawa and Dang (eds.)

terval between the Flemingites rursiradiatus
beds and Owenites koeneni beds, but are
scarce in the Xenoceltites variocostatus beds.
Novispathodus waageni is a well-known
species whose range covers the entire Smithian (Sweet et al., 1971; Orchard, 2007a). Sweet(1970b) first reported the species from the Mianwali Formation, West Pakistan and designated it as the guide species of Zone 7, whichcorresponds to the Smithian part of the formation. Subsequently, Nv. waageni has been reported from throughout the Smithian in otherparts of the world (McTavish, 1973; Mosher,
1973; Goel, 1977; Buryi, 1979; Solien, 1979;
Wang and Cao, 1981; Koike, 1982; Matsuda,
1983; Beyers and Orchard, 1991; Orchard,
2007b; Orchard and Krystyn, 2007; Zhao etal., 2007; Orchard, 2008; Beranek et al., 2010;
Goudemand et al., 2012 etc.). Orchard andKrystyn (2007), Zhao et al. (2007) and Orchard (2010) reported that the first appearance
datum of the species is an indicator of the Ind­
uan/Olenekian boundary (IOB). Furthermore,
the range of the species extends to the uppermost Smithian (Orchard, 2007a; Zhao et al.,2007).
A significant morphological change in Novispathodus waageni was pointed out by Matsuda (1983), Orchard and Krystyn (2007),
Zhao et al. (2007) and Igo (2009). Orchard
and Krystyn (2007) divided the species into
six morphotypes based on the form of denticles, lateral ribs, and basal cavities of abundant specimens from the Mud section, Spiti,
India. According to Orchard and Krystyn(2007), the first appearance data of thesemorpho­types are different, and Morphotype 1(M1), which has a prominent lateral rib, is theoldest, with a range limited to the lowermost
part of the formation. M1 does not occur in the
Bac Thuy Formation, which indicates thatlowermost Smithian strata are not included in
the formation.
Discretella discreta was first describedfrom the Smithian ammonoid beds at Crittenden Springs, Nevada as Ctenognathus discreta(Müller, 1956). It has also been reported from
Malaysia (Koike, 1982), South China (Duan,
1987), northeastern Vietnam (Bui, 1989),
Spiti, India (Krystyn et al., 2007), and British
Columbia (Orchard, 2008; Beranek et al.,2010). In particular, Krystyn et al. (2007) andOrchard (2007b) reported the occurrence of D.
discreta from the Rohillites rohilla ammonoid
Zone (= Lower Smithian) of Spiti, India, andOrchard (2008) reported that it co-occurs with
the Smithian ammonoid Euflemingites romunderi Tozer, 1961, which indicates an Early to
Middle Smithian age. Thus, D. discreta ranges
from the Lower to the Middle Smithian, andits occurrence extends from throughout the
Tethyan realm to the Panthalassan region.
Hence, this world-wide species is an important
indicator of Lower to Middle Smithian sediments.
Abundant specimens of Guangxidellabransoni occur in the middle part of the Bac
Thuy Formation in association with Conservatella conservativa and Discretella discreta,and its range extends from throughout the Urdyceras tulongensis ammonoid beds up
through the Leyeceras horizon of the Owenites
koeneni ammonoid beds. G. bransoni, characterized by an arched element and cordiform
basal cavity, has only been reported from thePanthalassan realm; Nevada (Müller, 1956),
Utah (Solien, 1979), northeastern Vietnam(Bui, 1989), and South China (Zhang andYang, 1991).
Eurygnathodus costatus is a well-known
species that ranges from the Upper Dienerian
to the Lower Smithian in certain parts of theworld. This segminiplanate element is characteristic and its distribution is limited mainly to
the Tethyan realm. However, the species has
been reported from Smithian strata in British
Columbia, Canada (Beyers and Orchard,1991). In the Bac Thuy Formation, the species
co-occurrs with Flemingites rursiradiatus, andit also coexists with flemingitid ammonoids in
Spiti and South China (Orchard and Krystyn,
2007; Zhao et al., 2007).

Olenekian (Early Triassic) in northeastern Vietnam

Smithodus longiusculus, which has only
been reported from a few worldwide locations,co-occurs with the following ammonoids andconodonts: Arctoceras tuberculatum (Smith,1932) and Furnishius triserratus (Buryi, 1997,
South Primorye); Euflemingites romunderi and
Neospathodus waageni (= Novispathodus waageni) (Mosher, 1973, British Columbia). Thesetaxa indicate that S. longiusculus ranges fromthe Lower to the Middle Smithian, and furthermore, its geographical occurrence is limited to the marginal region of Panthalassa.
Novispathodus pingdingshanensis Zone:
This zone extends from the first occurrence ofNovispathodus pingdingshanenesis to the first
appearance of Triassospathodus symmetricus.
Other co-occurring taxa include Nv. ex gr.
waageni, Nv. sp. nov. A, Nv. sp. indet. A, andIcriospathodus? zaksi. The zone encompasses
the Xenoceltites variocostatus and Tirolites cf.
cassianus ammonoid beds.
Compared to the other two zones, conodonts in this zone are fewer in number andtheir size is smaller. Chen et al. (2013) reported a size reduction in conodonts around theSmithian/Spathian boundary (SSB) and suggested that the phenomenon is related to the
SSB global worming event. In this study, asimilar trend is also documented near the SSB
in the Bac Thuy Formation.
Novispathodus pingdingshanenesis was
first described by Zhao et al. (2007) from theWest Pingdingshan section, Anfui Province,
South China. Subsequently, the taxa has beenreported from other Chinese localities including Anhui (Liang et al., 2011), Guizhou (Ji etal., 2011) and Guangxi (Goudemand et al.,2012). These authors reported only a lowermost Spathian occurrence for the species.
However, in Guangxi (Goudemand et al.,2012) and northeastern Vietnam (this study),
Nv. pingdingshanensis co-occurs with Xenoceltites variocostatus, which indicates a latest
Smithian age. Furthermore, in this study the
Spathian part of the Bac Thuy Formation also
yields the mentioned species. This evidence

53

revises the range of the species downwards
such that it extends from the uppermost Smithian to the Lower Spathian.
Icriospathodus? zaksi, an important species for recognition of the SSB, was first described by Buryi (1979) from the upper part of
the Anasibirites nevolini Zone (= Upper Smithian) and the lower part of the Tirolites cassianus Zone (= Lower Spathian) in South Primorye, Russia (Buryi, 1979). The taxa has
also been reported from the southern Alps
(Perri and Andraghetti, 1987, pl. 33, figs. 1–4)
where it co-occurs with Triassospathodus
symmetricus (Perri and Andraghetti, 1987, pl.
33, fig. 5), which indicates a range from theLower to the Upper Spathian (both species
were described as Neospathodus triangularis).
According to these reports, the range of I.?
zaksi extends from the uppermost Smithian to
the Lower Spathian.
The form of the P1 element of Icriospathodus? zaksi resembles that of I. collinsoni except for a single row of denticles. Obviously,
the species exhibits a form that is ancestral to
I. collinsoni, but their rarity in the Bac Thuy
Formation makes it difficult to resolve theevolutionary process between them. However,
the existence of I.? zaksi may result in a revision of conodont biostratigraphy around the
SSB based on the evolutionary process of
Neospathodus or Novispathodus.
Novispathodus sp. nov. A has only beenreported from the Guangxi Province, South
China (Goudemand et al., 2012) where it cooccurs with Nv. pingdingshanensis and Nv.
waageni. Moreover, according to Goudemand
et al. (2012), these species were collectedfrom the Xenoceltites ammonoid Zone, whichcontains the latest Smithian aged ammonoid
X. variocostatus.
Triassospathodus symmetricus Zone: Thiszone, consisting of typical Spathian species, isdefined by the first appearance of Triassospathodus symmetricus. Co-occuring taxa include Novispathodus pingdingshanensis, Nv.
triangularis, T. homeri, Icriospathodus collin-54

Shigeta, Komatsu, Maekawa and Dang (eds.)

soni, and I.? crassatus. The zone encompasses
the Tirolites cf. cassianus and Tirolites sp. nov.
ammonoid beds. In this study, relatively few
conodonts were collected in the middle toupper parts of the zone, but the occurrence of
Nv. pingdingshanensis at KC02-17 demonstrates that the zone is continuous.
Triassospathodus symmetricus, first reported from Jabal Safra, Oman by Orchard(1995), is described as having a symmetricalsegminate element with fused and reclined
denticles, and a strongly expanded subtriangular or subquadrate basal cavity, which exhibits
several morphological changes (Orchard,1995). In addition, the larger basal cavity andfewer posterior processes are different fromthose of T. homeri. Furthermore, its range extends from the Lower to the Upper Spathian(Orchard, 1995).
In the Bac Thuy Formation, Triassospathodus symmetricus also exhibits morphologicalvariations of the denticulation and basal cavity. In addition, its posterior small processes
gradually increase from the lowermost to thelower part of the zone (KC02-12 to KC02-15).
T. homeri also co-occurs with T. symmetricus
in KC02-15, which indicates rapid evolutionof Triassospathodus. T. symmetricus probably
evolved into T. homeri during early Spathiantime.
Novispathodus triangularis and Triassospathodus homeri are well-known Spathianspecies and have been reported from many localities. In addition, the range of these species
has been extended to the uppermost Spathian(Orchard, 2010).
The P1 element of Icriospathouds collinsoni is characterized by ridge-like denticles anda developed lateral rib. Although its range isof relatively short duration, its distribution
covers a wide area, extending from the Tethys
to Panthalassa and also to the boreal region(Sweet et al., 1971; Solien, 1979; Duan, 1987;
Koike, 1992; Orchard, 1995; Lucas and Orchard, 2007; Ji et al., 2011). These facts demonstrate that I. collinsoni is one of the mostimportant index fossils for the Lower Spathian.
Correlation (by Y. Shigeta and T. Maekawa)
Based on Smithian ammonoid and conodont biostratigraphy (Fig. 37), the lowest partof the basal portion of the Bac Thuy Formation, containing the Flemingites rursiradiatus
beds and the lower part of the Novispathodus
ex. gr. waageni Zone, can be correlated withthe lowermost Middle Smithian. The overlying middle and upper parts of the basal portionof the Bac Thuy Formation, characterized by
the Urdyceras tulongensis beds and the
Leyeceras horizon of the Owenites koeneni
beds, are correlatable with the lower to middle
Middle Smithian. The Guodunites horizon of
the Owenites koeneni beds indicates that theupper lower portion of the Bac Thuy Formation is correlatable with the upper Middle
Smithian.
A change in the ammonoid and conodont
assemblages in middle portion of the Bac
Thuy Formation, in which the Xenoceltites
variocostatus beds and the Novispathodus
pingdingshanensis Zone are recognized, suggests that this part is correlatable with theUpper Smithian (Fig. 37). The upper portionof the Bac Thuy Formation, yielding the Early
Spathian ammonoid Tirolites and Columbites
and a typical Spathian conodont Icriospathodus collinsoni and Triassospathodus homeri,can be correlated with the Lower Spathian(Fig. 37).
Age of rhyolite from the Khon Lang
Formation(by Y. Tsutsumi and T. Komatsu)
Rhyolite samples from the basal part of
the Khon Lang Formation at NT01 were investigated for radiometric age analysis of zircon. Cathodoluminescence imaging reveals(Fig. 38) that the sample includes two types ofzircon grains, those exhibiting core-rim structure (core-rim grains) and those having less

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 38. Cathodoluminescence images of typical zircon grain in the sample. Circles on the images indicate theanalyzed spots by LA-ICP-MS.

Fig. 39. Tera-Wasserberg U-Pb concordia diagram of all data from the sample. 207Pb* and 206Pb* indicate radiometric 207Pb and 206Pb, respectively.

55

56

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 40. Tera-Wasserberg U-Pb concordia diagrams and age distribution plot of the zircons from the sample.
207
Pb* and 206Pb* indicate radiometric 207Pb and 206Pb, respectively.

Fig. 41. Probability distribution diagram of the core ages from the grains that show core-rim structure. The
207
Pb*/206Pb* ages for older (>1 Ga) zircons, and 206Pb*/238U ages for younger zircons are used in this diagram. 207Pb* and 206Pb* indicate radiometric 207Pb and 206Pb, respectively.

Olenekian (Early Triassic) in northeastern Vietnam

core (core-less grains). The core-less grainsshow magmatic oscillatory zoning.
The ages of the core-less grains and rims
in the core-rim grains show a concentration of~240 Ma, but data from the cores in the corerim grains yield older and variable ages (Fig.
39). The weighted mean age of the core-lessgrains and rims in the core-rim grains indicate
237.7±1.9 Ma (95% conf.; Fig. 40), which isthought to be the magmatism (eruption) age ofthe rhyolite. On the other hand, the cores in
the core-rim grains indicate multiple ages
(Fig. 41); ca. >500 Ma, 600–800 Ma, 800–
1100 Ma, ~2500 Ma and ~3000 Ma. This agedistribution is analogous to the detrital zircon
from the South China Craton (e.g. Xu. et al.,2007; Jia et al., 2010). In consideration of theabove data, the zircon cores are thought tohave originated from rocks of sedimentary-origin associated with the South China Craton,and the cores thought to be xenocrysts were
captured by the rhyolitic magma from the wall
and/or cap rocks when the magma rose in thesurrounding rocks.
Discussion
Aspects of Smithian ammonoid fauna(by Y. Shigeta)
Because of the difficulty encountered incollecting macrofossils from the very hard
limestones in the Bac Thuy Formation, a complete faunal list of Smithian ammonoids is not
yet possible. However, ammonoids collectedthus far and described herein clearly suggestthat the Smithian ammonoid fauna in northeastern Vietnam is nearly identical to that ofSouth China (Chao, 1959; Brayard and Bucher, 2008).
These ammonoid taxa exhibit six different
geographical distribution patterns (Fig. 42).
The first pattern, characterized by endemic
distribution restricted to South China andnortheastern Vietnam, is represented by Ussuria kwangsiana (Fig. 42.1), Jinyaceras cf.
bellum, Paranannites sinensis and Paranan-

57

nites involutus (Chao, 1959). The second pattern, consisting of numerous taxa, exhibits arelatively wide distribution in the Tethys (e.g.
South China, Timor, South Tibet, Spiti, theSalt Range, Oman), and includes the following
species: Preflorianites radians (Fig. 42.2), Xenoceltites variocostatus, Pseudaspidites muthianus, Leyeceras rothi, Guodunites monneti,
Dieneroceras? goudemandi, Flemingites rursiradiatus, Anaflemingites hochulii, Galfettites
simplicitatis, Urdyceras tulongensis and Submeekoceras hsüyüchieni. Aspenites acutus, theonly taxon of third pattern (Fig. 42.3) is distributed in the Tethys and the eastern equatorial side of the Panthalassa (e.g. California, Nevada, Utah, Idaho). In contrast, the fourth pattern, consisting of Juvenites sinuosus (Fig.
42.4) also exhibits a Tethyan distribution, but
its Panthalassan distribution is limited to thewestern middle latitude (South Promorye). Parussuria compressa and Owenites koeneni(Fig. 42.5), which are widely distributed in thelow- to middle-paleolatitudinal regions in the
Tethys and both sides of the Panthalassa, aremembers of the fifth pattern. The sixth patternis represented by the pandemic distribution of
Pseudosageceras multilobatum (Fig. 42.6),
which occurs in the Tethys, both sides of thePanthalassa and the Boreal Realm (e.g. Arctic
Canada, Spitsbergen).
Most species belonging to the first, second, and fourth distribution patterns also haverelated species belonging to the same genus inother low- to middle-paleolatitudinal regions.
For example, Preflorianites toulai (Smith,1932), Xenoceltites youngi Kummel andSteele, 1962, Pseudaspidites silberlingi Jenkset al., 2010, Galfettites lucasi Jenks et al.,2010, Anaflemingites silberlingi Kummel andSteele, 1962, A. russelli (Hyatt and Smith,1905), Guodunites hooveri (Hyatt and Smith,1905), Submeekoceras mushbachanum (White,
1879) and Juvenites septentrionalis Smith,
1932 all occur on the eastern equatorial side of
the Panthalassa (western USA). Brayard et al.
(2006, 2009) discussed the paleobiogeography

58

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 42. Paleogeographical distribution of selected Smithian ammonoids. Paleomaps modified after Péron et al.,2005, Brayard et al., 2006 and Brayard et al., 2009. 1, Ussuria kwangsiana. 2, Preflorianites radians. 3,
Aspenites acutus. 4, Juvenites sinuosus. 5, Owenites koeneni. 6, Paseudosageceras multilobatum.

Olenekian (Early Triassic) in northeastern Vietnam

59

60

Shigeta, Komatsu, Maekawa and Dang (eds.)of Smithian ammonoids from South China andconcluded that the fauna exhibits strong affinities at the generic level with the low-paleolatitudinal regions (Tethys and eastern Panthalassa) and South Primorye. However, Shigeta
et al. (2009) pointed out that the Smithian ammonoid fauna in South Primorye contains
many endemic species and it actually sharesvery few common species with South China.
Thus, faunal affinity at the generic level does
not coincide with that at the specific level for
Smithian ammonoids. Smithian ammonoid occurrences in the Bac Thuy Formation suggestthat the fauna exhibits a very strong relationship with other Tethyan faunas, but relatively
weak relationships with faunas on both sidesof the Panthalassa.
Internal features in the early whorls ofammonoids (by Y. Shigeta and T. Maekawa)
Following the treatment of limestone samples from the Bac Thuy Formation with acetic
acid, many well-preserved micro-ammonoid
specimens free of obscuring matrix were
found in the residue together with abundantconodonts. The sparry calcite filling of thephragmocones had been completely dissolved
as had all of the shell material, thus leaving
only insoluble thin layers (probably of organic
origin) that originally covered the shell sur­faces. This phenomenon permitted observationof the unique three-dimensional geometry of
the internal features of the early whorls.
These early whorls consist of the initialchamber, caecum, flange, siphuncle, and septa(Fig. 43). Shaped somewhat like a rugby football, the initial chamber is separated from thesucceeding whorls by the first septum (= proseptum), which is slightly convex adapically.
The bulb-like beginning of the siphuncle,
termed the caecum, is attached to the insidesurface of the initial chamber and is located in
the ventral position at the first septum. A granular structure is also visible on the inside surface of the initial chamber near the inner lip ofinitial chamber (= flange).

Since the mid-nineteenth century, many
workers have studied the internal shell features of the early whorls of ammonoids, and it
has been determined that these embryonicshells all share a number of common morphological features (Landman et al., 1996). The
relative shape of these features as well as theirsize and position with respect to each other appear to be stable at higher taxonomic levels(Druschits and Khiami, 1970; Druschits andDoguzhaeva, 1974, 1981; Tanabe et al., 1979,
2003; Tanabe and Ohtsuka, 1985; Ohtsuka,
1986; Tanabe et al., 1994; Landman et al.,
1996; Shigeta et al., 2001). This fact suggeststhat these internal shell features are strongly
constrained phylogenetically, and therefore, it
is possible to investigate the higher-level systematics and evolution of the ammonoids on
the basis of subtle changes in these features.
Shigeta et al. (2001) studied these early internal shell features in 40 species of the Goniatitida, Prolecanitida and Ceratitida, and discussed the origin of the Ceratitida. Shigeta andWeitschat (2004) also discussed the origin of
the Ammonitina inferred from the internal
shell features of some latest Triassic and Jurassic ammonoids.
Compared to Carboniferous, Permian, Jurassic and Cretaceous ammonoids, the internal
shell features of Triassic ammonoids have received relatively little attention. Most previous
studies, excluding that of Weitschat (1986),
are based on the observation of sections polished parallel to the median section plane ofmatrix-filled specimens (Arkadiev and
Vavilov, 1984; Vavilov, 1992; Zakharov, 1978;
Shigeta and Weitschat, 2004). After dissolving
the sparry calcite filling of the phragmocones
with acetic acid, Weitschat (1986) then described the three-dimensional inner structuresthat included complex networks of cameral
membranes in Middle Anisian ammonoids
from Central Spitsbergen.
It is quite rare to find specimens whosephragmocones are free of interior matrix, but
this preservational feature has been noted inOlenekian (Early Triassic) in northeastern Vietnam

Fig. 43. Internal features in the early whorls of the Lower Triassic ammonoids from the Bac Thuy Formation innortheastern Vietnam. 1–2, NMNS PM23855, from BR01-06. 3–4, NMNS PM23856, from PK01-01. 5,
NMNS PM23857, from BT02-01. 6, NMNS PM23858, from KC01-10. C: caecum, F: flange, IC: initialchamber, S: siphuncle, S1: first septum (proseptum), S2: second septum, S3: third septum, S4: fourth septum.

61

62

Shigeta, Komatsu, Maekawa and Dang (eds.)

some Jurassic and Cretaceous ammonoids.
This phenomenon permits detailed observations regarding the shape and spacing of thefirst few septa and associated structures in theearly whorls (Landman and Bandel, 1985),
and it has contributed significantly to the understanding of the sequence of embryonic development (Bandel, 1982). Furthermore,
Maeda and Seilacher (1996) reported the existence of fungal “pseudomorphs” preserved in
the hollow phragmocone of a Cretaceous ammonoid from Hokkaido and discussed early
decay processes. Recently, Hoffmann’s (2010)
study of a hollow Cretaceous ammonoid from
northern Kamchatka with a three-dimensional
visualization method that utilized a computer
tomography (CT-scan) showed a clear imageof internal shell features.
Acid treatment of limestone samples fromvarious horizons of the Bac Thuy Formation
yields numerous well-preserved micro-ammonoids whose phragmocones are free of obscuring matrix. Continued studies of the internal
shell features of these specimens may provide
an important key for understanding the detailed microstructural relationships of theirmorphological features, as well help establish
a clearer understanding of the higher taxonomy and evolution of Early Triassic ammonoids.
Ammonoid mode of occurrence (by Y.
Shigeta and T. Komatsu)
Ammonoids are not preserved in the portion of the lower part of the Bac Thuy Formation consisting of wavy, lenticular thin flatbedded carbonates and intraclastic limestones
containing angular flat carbonate pebbles andcobbles that were deposited in a tidal flat environment, between the supratidal and intertidal
zones (Komatsu et al., 2014). However, thecross-stratified limestones presumably deposited in an intertidal to subtidal calcareous
sand-flat environment do yield rare, poorly
preserved ammonoids. Various types of ammonoids occur abundantly in the alternating

beds of bioclastic, oolitic, and intraclastic
limestone characterized by wave ripples andlow-angle cross-stratification that were deposited in a subtidal flat to storm-wave-influenced
shallow marine environment. Ammonoids arealso abundant in the alternating beds of bioclastic and intraclastic limestone formed byconcentrated density flows as well as the marlsof hemipelagic calcareous deposits. Poorly
preserved ammonoids occur only rarely in the
structureless intraclastic limestones that probably represent transgressive lag deposits. Ammonoids are not found in the limestone breccias formed by debris flows.
In the middle part of the Bac Thuy Formation, only Xenoceltites variocostatus occurs in
the organic-rich dark gray bioclastic limestone
and mudstone. The limestone is interpreted asa turbidity flow deposit (calciturbidite), whereas the mudstone is considered to be a hemipelagic siliciclastic deposit formed in an anoxic
to dysoxic environment in a slope to marginalbasin plain (Komatsu et al., 2014). Ammonoid
shells were probably transported by turbidity
flows.
In the upper part of the Bac Thuy Formation, ammonoids are preserved mainly in fineto very-fine grained calcareous sandstone embedded in a thick and weakly laminated mudstone. The sandstone beds are typical of distal
turbidites, and the mudstone accumulated
from suspension under calm conditions (Komatsu et al., 2014). As with the middle part ofthe Bac Thuy Formation, ammonoid shells
were probably transported by turbidity flows.
The scarcity of ammonoids in the surrounding
mudstone suggests that the slope to marginalbasin plane was not a suitable environment inwhich to live. A similar mode of occurrence ofammonoids has been reported for the gravity
flow deposits of the Lower Triassic Abrek section in South Primorye, Russia (Shigeta et al.,2009).
In summary, the ammonoid mode of occurrence in the Bac Thuy Formation suggeststhat while the supratidal to intertidal environ-

Olenekian (Early Triassic) in northeastern Vietnam

ment was uninhabitable, the majority of ammonoids probably lived in the subtidal flat tostorm-wave-influenced shallow marine environment typical of a carbonate platform. After
death their shells were transported from theirbiotope to the slope to marginal basin plane bygravity flow.
Smithian gastropod assemblages of the Bac
Thuy Formation (by A. Kaim, A. Nützel and
T. Maekawa)All gastropods described and illustrated inthis paper were removed from the limestone
samples by applying acetic acid. The specimens are silicified larval and/or juvenile shells
or their moulds. The preservation of the shells
vary from well preserved shells with external
ornamentation preserved (e.g., Figs. 125.1–
125.3, 132.4–132.6, 135.4–135.6), shells where
the external layer peeled off (e.g., Figs.125.7–
125.12, 132.7–132.9) and specimens where
only internal mould is preserved (Figs. 123.1–
123.3, 130.6, 132.1–132.3, 133.4–133.9). Boththe preservation and the larval/juvenile natureof the specimens cause that the detailed taxonomy (i.e., species level) is impossible.
The gastropods come from the fossiliferous limestone beds in the basal portion of the
Bac Thuy Formation (BTF) exposed at Bac
Thuy (sections BT01, 02), bedded limestone
in the lower to middle portions of the BTF exposed along the Ky Cung River (sections
KC01, 02), and the upper middle portion of
the BTF (section KC02). Gastropod shells
have been found in following stratigraphic
levels of the Smithian though they significantly differ in number and preservation (Table 1).
Lowest Middle Smithian gastropods: Only
two poorly preserved gastropods were collected from the Flemingites rursiradiatus beds.
Specimen NMNS PM23849 from BT01-04(Fig. 123.1–123.3) is moderately high-spired
juvenile shell with deeply incised suture. The
shell is poorly preserved with no external ornamentation preserved. The shell may have

63

Table 1. The number of gastropod taxa and the numberof specimens in the recognized ammonoid biostratigraphic units. F: Flemingites rursiradiatus beds, O:
Owenites koeneni beds, X: Xenoceltites variocostatus beds, F/O: beds between the Flemingites rursiradiatus and the Owenites koeneni beds.
Species

F

F/O

O

X
1

Worthenia sp. indet.
Anomphalus sp. indet.
Abrekopsis sp. indet.
Naticopsis sp. indet. A
Naticopsis sp. indet. B
Strobeus sp. indet.
Ampezzopleura sp. indet.
Atorcula sp. indet.
Others

1
1

10
1

8
1
7
9
1
2
4
4

Total specimens

2

15

36

2

Total taxa

2

4

8

2

2
2

1

belonged to a caenogastropod juvenile (seee.g., Atorcula-type and Ampezzopleura-typejuvenile shells it this paper). Another single
poorly preserved specimen NMNS PM23848
from BT02-01 (Fig. 123.4–123.6) may belong
to Atorcula though the preservation does notallow any precise identification.
Lower Middle Smithian gastropods: Fifteen juvenile gastropod shells representing
four taxa were obtained from beds between
the Flemingites rursiradiatus beds and theOwenites koeneni beds. They are dominatedby Atorcula sp. indet. (10 specimens) associated by Worthenia sp. indet. (2 specimens), Naticopsis sp. indet. A (2 specimens) and single
poorly preserved gastropod (Fig. 127.10–
127.12) that could not be matched to any otherspecies recognized in the samples from Vietnam.
Middle to upper Middle Smithian gastropods: The Owenites koeneni beds provided not
only the richest by number but also most diversified assemblage of gastropods: thirty-six
shells are classifies in eight taxa. Most common are neritoids represented by sixteen specimens of Naticopsis (sp. indet. A + sp. indet. B)
and single specimen of Abrekopsis? sp. indet.
Anomphalus? sp. indet. (8 specimens) is also
common. Atorcula sp. indet. (4 specimens),

64

Shigeta, Komatsu, Maekawa and Dang (eds.)

Ampezzopleura sp. indet. (2 specimens), andStrobeus sp. indet. (1 specimen). Additional
four specimens are too poorly preserved forgeneric identification (Figs. 130.6, 133.4–
133.12).
Upper Smithian gastropods: Single specimen of Anomphalus? sp. and Naticopsis sp.
indet. A were collected from the Xenoceltites
variocostatus beds.
The shells found in the Smithian of northeasternVietnam are only larval conchs or early
juveniles of taxa displaying mostly planktotrophic type of development. This is indicated by
the small size of the specimens (smaller 1 mm)
and the fact that the initial whorl is present inmost specimens showing that the apical portions of gastropods are present. Gastropod larval fall assemblages have been reported fromseveral Palaeozoic formations (Bockelie andYochelson, 1979; Herholz, 1992; Nützel andMapes, 2001; Nützel et al., 2007; Mapes andNützel, 2009). Nützel and Mapes (2001) and
Mapes and Nützel (2009) reported a larval fall
assemblage from the Mississippian of theUnited States and showed that metamorphosis
and growth to larger adult sizes of the larvae
was impossible due to anoxic condition in bottom waters. The same is probably the case in
the studied assemblages from the Early Triassic of Vietnam. The gastropods either failed tosurvive metamorphosis or died soon thereafter.
Most likely the bottom water was dysoxic or
periodically anoxic.
Most of the taxa present in the investigated samples have also been reported from otherassociations of Smithian or more generally
Early Triassic age (see e.g. Batten and Stokes,
1986; Nützel, 2005; Nützel and Schubert,
2005; Wheeley and Twitchett, 2005; Kaim,
2009; Kaim et al., 2010, 2013). The only taxa
not recorded before in the Early Triassic are
Anomphalus and Atorcula though known from
Permian and Late Triassic and therefore notsurprising in the Early Triassic.

Bivalve assemblages and mode of occurrence(by T. Komatsu, H. T. Dang and T. C. Dinh)
Bivalves are found in uppermost Smithian
to lowermost Spathian marginal basin deposits
consisting of thin-bedded turbidite limestone(= calciturbidite), marl and hemipelagic mudstone containing calcareous nodules. The calciturbidites are composed mainly of Tb (parallel laminated limestone), Tc (cross-laminatedlimestone) and Td (week parallel laminatedlimestone and marl) divisions. Well-preserved
shells are commonly found in the calciturbidites, marls and calcareous nodules, but nearly
all specimens in the hemipelagic mudstone arepoorly preserved and completely flattened.
Bivalve preservation exhibits two different
types in the modes of occurrence. The first
type is a shell- and matrix-supported thin
(1–3 cm) lenticular shell-concentration within
the thin calciturbidite beds and marl layers
consisting of ammonoids and bivalves such as
Crittendenia australasiatica, C. langsonensis,
Leptochondria bittneri, Bositra limbata and“Pseudomonotis” himaica. In Facies 8, which
consists of organic-rich dark gray wackestone
and hemipelagic mudstone containing marllayers (Komatsu et al., 2014), C. australasiatica is the dominant species, accounting for+80% of the bivalve assemblage from thebasal parts of Tb, Tc and Td divisions of theorganic-rich dark gray calciturbidites. In Facies 10, which consists of thick hemipelagic
mudstone intercalated with sandstone andwackestone layers (Komatsu et al., 2014), C.
australasiatica and “Pseudomonotis” himaica
are abundant in the Tc and Td divisions of theturbidite wackestone layers, respectively (Fig.
17). Furthermore, in both Facies 8 and 10 B.
limbata, Bositra sp. indet. and juveniles of
Crittendenia form small lenticular shell-concentrations 3–10 cm thick in the Td divisionsof the thin turbidite layers and hemipelagic
mudstone. These bivalves are commonly disarticulated and/or fragmentary, which is indicative of gravity flow transport and typical allochthonous occurrence.

Olenekian (Early Triassic) in northeastern Vietnam

The second mode of occurrence consistsof shell-scattered beds in the hemipelagic
mudstone overlying the calciturbidite andmarl. Both articulated and disarticulated shellsof B. limbata and Bositra sp. indet. are foundin the hemipelagic mudstone. Some of the articulated shells are preserved in a butterfly position, and disarticulated right and left valvesof the same individual are seen to occasionallyoverlap. Both articulated and disarticulatedshells of C. australasiatica are also commonly
found in the hemipelagic mudstones of Facies
8. These species may represent a parautochthonous assemblage.
Brief note on the radiolarian faunas of theUpper Smithian (Lower Triassic) (by O.
Takahashi)
Very little has been published on the distributions and relative abundances of radiolarians in the Lower Triassic, particularly in the
Induan and lower Olenekian (Smithian), as radiolarian occurrences from these times are apparently restricted and scarce, and the diversity is very low. Induan and lower Olenekian radiolarians have been recovered from the following five sections: the Dienerian (upper Induan) to lower Smithian (lower Olenekian)marly limestone beds of northwestern Turkey(Kozur et al., 1996a), the Induan to Olenekianchert beds of northern New Zealand (Kamata
et al., 2007; Takemura et al., 2007; Hori et al.,2011), the Dienerian limestone beds of southern Thailand (Sashida et al., 1998), the Smithian chert beds of central Oregon (Blome andReed, 1992), and the Olenekian limestone
beds of southern Italy (Marsella et al., 1993).
In addition, Sugiyama (1997) described wellpreserved Early Triassic radiolarian faunas
from central Japan; his Follicucullus-Parentactinia Assemblage Zone (TR0), which correlates with the lower part of the Parentactinia
nakatsugawaensis assemblage of Sugiyama(1992) and the lower part of the Stylosphaerafragilis Zone of Bragin (1991), may be early
Spathian or older in age.

65

The Upper Smithian radiolarian faunafrom the Bac Thuy Formation presented in thisstudy has a unique species composition and a
relatively high diversity for this stratigraphic
level. The fauna includes a mixture of Paleozoic- and Triassic-type radiolarians. The Paleozoic-type radiolarians are dominated by entactinarians with several species of the following genera: Multisphaera, Plenoentactinia,
Retentactinia, and Spongentactinia. These
genera have been reported from the Devonian
and Carboniferous of western Australia(Aitchison, 1993; Won, 1997) and western
Germany (Won, 1990), and from the Permianof Urals (Afanasieva, 2000; Dumitrica, 2011),
but none of them have been previously reported from Mesozoic strata. Interestingly, thesame type of faunas, dominated by entactinarians, have been reported in other faunas fromthe Lower Triassic limestone beds such as: theDienerian to lower Smithian of Turkey (Kozur
et al., 1996a), the Dienerian of Thailand(Sashida et al., 1998), and the latest Spathian
to earliest Anisian of Thailand (Sashida andIgo, 1992). Moreover, all of these Early Triassic occurrences have been restricted to limestone beds in low-latitude regions along thewestern margin of Panthalassa (Scotese,
2002). Therefore, the radiolarian fauna described here has the biostratigraphic potential
to be of Early Triassic age, and may also have
paleogeographic and paleoceanographic affinities to Early Triassic low-latitude faunas along
the western margin of Panthalassa.
Systematic Paleontology
Cephalopods (by Y. Shigeta and H. D. Nguyen)
Systematic descriptions basically follow
the classification established by Sweet (1964)
for orthocerids and Tozer (1981, 1994) for ceratitids and phylloceratids. Morphologicalterms are those used in the Treatise on Invertebrate Paleontology (Moore, 1957, 1964).
Quantifiers used to describe the size and shapeof ammonoid shell replicate those proposed by

66

Shigeta, Komatsu, Maekawa and Dang (eds.)

Matsumoto (1954, p. 246) and modified by
Haggart (1989, table 8.1).
Abbreviations for shell dimensions: D =shell diameter; U = umbilical diameter; H =whorl height; W = whorl width.
Institution abbreviations: CGM = Central
Research Geological Prospecting Museum(CNIGR Museum), St. Petersburg; GPIBo =Goldfuss Museum (Steinmann Institute), Bonn
University; GSI = Geological Survey of India,
Kolkata; IPUW = Department of Palaeontology, University of Vienna, Vienna; NIGP = Nanjing Institute of Geology and Palaeontology,
Chinese Academy of Sciences, Nanjing;
NMNS = National Museum of Nature and Science, Tsukuba; PIMUZ = Institute and Museum of Paleontology, University of Zurich, Zurich; USNM = Smithonian National Museumof Natural History, Washington, D. C.
Class Cephalopoda Cuvier, 1795
Order Orthocerida Kuhn, 1940
Superfamily Orthoceratoidea McCoy, 1844
Family Orthoceratidae McCoy, 1844
Genus Trematoceras Eichwald, 1851

tinguished by the fine transverse lirae on thejuvenile shell, which contrasts with network
lirae on the juvenile shell of T. subcampanile(Shigeta and Zakharov, 2009, Fig. 27). They
differ from T. mangishlakense Schastlivtceva(1981) and T. insperatum Schastlivtceva(1988) by the smaller angle of shell expansison. The described specimens are morphologically very similar to T. campanile (Mojsisovics, 1882), T. vulgare Schastlivtceva (1981), T.
ciarum Schastlivtceva (1986), and T. boreale
Schastlivtceva (1986), but a definitive species
assignment cannot be made due to an insufficient number of well-preserved specimens.
Occurrence: Described specimens fromNT01-04 within the portion of the Novispathodus pingdingshanensis Zone represented by
the Xenoceltites variocostatus beds (Upper
Smithian = upper Lower Olenekian) in the Bac
Thuy Formation, northeastern Vietnam.
Order Ceratitida Hyatt, 1884
Superfamily Xenodiscoidea Frech, 1902
Family Kashmiritidae Spath, 1934
Genus Preflorianites Spath, 1930

Type species: Orthoceras elegans Münster,
1841.

Type species: Danubites strongi Hyatt andSmith, 1905.

Trematoceras sp. indet.

Preflorianites radians Chao, 1959

Figs. 44, 45

Figs. 46, 47

Material examined: Five specimens,
NMNS PM23459–23463, from NT01-04.
Description: Moderately expanding orthoconic shell with 4–5 degree adoral angle of expansion and circular whorl cross-section. Juvenile shell ornamented with fine transverse
lirae, while adult body chamber exhibits very
weak ribs as well as fine transverse lirae. Siphuncle located at center, with cylindrical connecting ring and short, orthochoanitic septal
neck. Suture simple and straight. Cameral deposits not observed.
Discussion: Although the described specimens are very close to Trematoceras subcampanile (Kiparisova, 1954), they are easily dis-

Xenodiscus bittneri Hyatt and Smith, 1905. Welter, 1922,
p. 106, pl. 158, figs. 8–9.
Preflorianites radians Chao, 1959, p. 196, pl. 3, figs. 6–8;
Brühwiler et al., 2012a, p. 15, pl. 1, figs. 8–9, pl. 2,
figs. 1–7.
? Glyptophiceras langsonense Vu Khuc, 1984, p. 31, pl. 1,
figs. 2–3, pl. 2, fig. 1; Vu Khuc, 1991, p. 121, pl. 45,
figs. 1–3, pl. 50, fig. 3.
Pseudoceltites? angustecostatus (Welter, 1922). Brayard
and Bucher, 2008, p. 18, pl. 3, figs. 1–7, text-fig. 19.
Preflorianites cf. radians Chao, 1959. Brühwiler et al.,2012c, p. 132, fig. 13A–E.

Holotype: NIGP 12564, figured by Chao
(1959, p. 196, pl. 3, figs. 7–8), from theOwenitian (Middle Smithian) of the Tientung
district (Tsoteng), western Guangxi, SouthOlenekian (Early Triassic) in northeastern Vietnam

Fig. 44. Trematoceras sp. indet. from NT01-04. 1, NMNS PM23459. 2–5, NMNS PM23460. 6–7, NMNS
PM23461. 8–10, NMNS PM23462.

67

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 45.

Trematoceras sp. indet., NMNS PM23463, from NT01-04. Arrow indicates position of last septum.

Olenekian (Early Triassic) in northeastern Vietnam

China.
Material examined: Five specimens,
NMNS PM23464–23468, from BT01-14, one
specimen, NMNS PM23469, from BT02-03,
one specimen, NMNS PM23470, from a float
limestone block at BT03, one specimen,
NMNS PM23471, from KC01-10, and three
specimens, NMNS PM23472–23474, from
KC01-13.
Description: Evolute, fairly compressedshell with elliptical whorl section, arched venter, indistinct ventral shoulders and slightly
convex flanks with maximum whorl widthslightly below mid-flank. Umbilicus fairly
wide with moderately high, nearly verticalwall and rounded shoulders. Ornamentationconsists of regularly spaced, strong, radial orslightly rursiradiate rounded ribs arising onumbilical shoulder and fading away on ventral
shoulder. Suture ceratitic. First lateral saddle
higher than second saddle, and third saddle
lower than second saddle. First lateral lobe
deep, wide with many denticulations at base,and second lateral lobe one-half depth of firstlobe.
Measurements (mm):Specimen no.

U

H

W

U/D W/HNMNS PM23466 32.0 13.0

D

—

—

0.41

—

NMNS PM23467 33.5 15.0

—

—

0.45

—

NMNS PM23472 39.5 17.8 12.4 10.0 0.45 0.81
NMNS PM23464 57.0 25.0 17.0 13.3 0.44 0.78
NMNS PM23465 59.2 28.5 17.0 14.0 0.48 0.82
NMNS PM23470 77.0 38.0 22.0 17.2 0.49 0.78
NMNS PM23468 79.0 42.3

—

—

0.54

—

NMNS PM23474 79.0 40.0 20.0 16.0 0.51 0.80

Discussion: The shell features of the specimens described herein match well with specimens from South China described as Pseudoceltites? cf. angustecostatus by Brayard andBucher (2008). However, as Brühwiler et al.
(2012a, p. 15) later indicated, these Chinaese
specimens actually belong to Preflorianites radians.
Brühwiler et al. (2012a) recently described Preflorianites radians from exotic

69

blocks in Oman, and illustrated the intraspecific variation in shell form and ornamentation ofthis species. One of their specimens, PIMUZ
27316 (Pl. 2, fig. 7), has a slightly narrower
umbilicus and weaker ribs than the typicalshell of this species (e.g. PIMUZ 27311, Pl. 2,
fig. 1). This particular specimen is very similar
to a specimen from Timor described as Xenodiscus bittneri by Welter (1922, pl. 158, figs.
8–9). Welter’s specimen probably should be
assigned to P. radians.
The specimen described as Preflorianites
cf. radians by Brühwiler et al. (2012c, PIMUZ
28201) from Spiti exhibits a slightly more involute coiling than P. radians, but this specimen is slightly flattened. Had its shell not been
deformed, its coiling would be more evolute,
which would fit well within the range of variation of P. radians.
Specimens attributed to Preflorianites cf.
radians by Brayard and Bucher (2008) fromthe Flemingites rursiradiatus beds (lowest
Middle Smithian) of South China have weaker
ornamentation and thicker whorls than P. radians. This taxon probably represents the ancestor of P. radians because it is otherwise very
similar.
Occurrence: Described specimens fromBT01-14, BT02-03, BT03, KC01-10 and
KC01-13 within the portion of the Novispathodus ex gr. waageni Zone that includes the
Leyeceras horizon of the Owenites koeneni
beds (middle Middle Smithian = middle Lower
Olenekian) in the Bac Thuy Formation, northeastern Vietnam. This species also occurs in
the Middle Smithian of South China(Owenites koeneni beds, Brayard and Bucher,2008), Timor (Welter, 1922), Spiti (Truempyceras compressum horizon, Brühwiler et al.,2012c), and Oman (Owenites koeneni fauna,
Brühwiler et al., 2012a).
Family Xenoceltidae Spath, 1930
Genus Xenoceltites Spath, 1930
Type species: Xenoceltites subevolutus

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 46. Preflorianites radians Chao, 1959 from BT01-14. 1–2, 10, NMNS PM23464. 3–4, NMNS PM23465.
5–6, NMNS PM23466. 7–8, NMNS PM23467. 9, NMNS PM23468.

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 47. Preflorianites radians Chao, 1959. 1–4, NMNS PM23472, from KC01-13. 5–6, NMNS PM23473, from
KC01-13. 7, NMNS PM23474, from KC01-13. 8, NMNS PM23471, from KC01-10. 9–10, NMNS PM23469,
from BT02-03. 11–12, NMNS PM23470, from BT03.

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Spath, 1930.
Xenoceltites variocostatus Brayard andBucher, 2008
Figs. 48–51
Xenoceltites variocostatus Brayard and Bucher, 2008, p.
21, pl. 5, figs, 1–14, pl. 6, figs. 1–6, text-fig. 21.
Xenoceltites cf. variocostatus Brayard and Bucher, 2008.
Brühwiler et al., 2010, p. 411, fig. 7.1–7.2; Brühwiler
et al., 2012b, p. 31, fig. 24A–AG; Brühwiler et al.,2012c, p. 134, fig. 14A–G.

Holotype: PIMUZ 25838, figured by Brayard and Bucher (2008, p. 21, pl. 5, fig. 1),
from the Anasibirites multiformis beds in
Waili, northwestern Guangxi, South China.
Material examined: One specimen, NMNS
PM23483, from NT01-04, one specimen,
NMNS PM23484, from NT01-05, one specimen, NMNS PM23485, from NT01-06, fourteen specimens, NMNS PM23475–23482,
23492–23497, from NT01-07, one specimen,
NMNS PM23498, from NT01-09, three specimens, NMNS PM23486–23488, from KC0210, and one specimen, NMNS PM23489, fromBR01-05.
Description: Early whorls (up to 10 mm indiameter): Fairly evolute, fairly compressed tovery compressed shell with elliptical whorl
section, arched venter, indistinct ventral shoulders and slightly convex flanks with maximum
whorl width at mid-flank. Umbilicus moderately wide with low, nearly vertical wall androunded shoulders. Ornamentation consists ofconspicuous, sinuous, prorsiradiate ribs arising
at umbilical shoulder, becoming strongly projected at ventral shoulders, and crossing venterin an acute convex arch.
Middle whorls (10–50 mm in diameter):As size increase, elliptical whorl section tends
to become more compressed, with narrowrounded to sub-acute venter and slightly convex flanks with maximum whorl width near
mid-flank. Umbilicus varies from fairly narrow to fairly wide with low, oblique wall androunded shoulders. Distinctive ribs graduallylose strength and become low, weak, fold-type

ribs. Shell surface covered by numerous
growth lines, which arise at umbilical seam,
curve backwards on umbilical shoulder, become sinuous, prorsiradiate, and cross venterin broad convex arch. Suture ceratitic. First
lateral saddle nearly equal to second saddle,
and third saddle lower than second saddle.
First lateral lobe deep, wide with many denticulations at base, and second lateral lobe nearly
equal to first lobe.
Later whorls (over 50 mm in diameter): As
shell grows larger, whorl section becomeseven more compressed and umbilicus becomes narrower. Shell surface ornamented by
growth lines as well as low, weak, fold-type
ribs.
Measurements (mm):Specimen no.
D
NMNS PM23489 11.7
NMNS PM23497 12.1
NMNS PM23495 12.7
NMNS PM23496 14.1
NMNS PM23485 15.3
NMNS PM23498 16.5
NMNS PM23475 22.2
NMNS PM23478 23.0
NMNS PM23483 26.0
NMNS PM23484 31.5
NMNS PM23488 37.0
NMNS PM23477 40.0
NMNS PM23482 46.0
NMNS PM23479 49.0
NMNS PM23481 49.3
NMNS PM23480 50.0
NMNS PM23487 59.0
NMNS PM23486 68.0

U
3.4
4.1
5.0
5.3
4.8
5.0
9.4
7.6
8.0
10.2
10.2
12.5
15.4
15.7
15.2
17.0
14.3
20.6

H
5.0
4.4
4.8
4.9
6.2
7.2
7.0
9.0
10.3
12.8
15.0
15.0
17.8
19.0
19.0
17.5
25.4
28.0

W
4.0
3.3
4.2
3.6
4.0
4.2
5.3
5.6
5.4
7.2
6.8
8.5
10.0
11.0
11.2
10.5
12.3
14.3

U/D
0.29
0.34
0.39
0.38
0.31
0.30
0.42
0.33
0.31
0.32
0.28
0.31
0.33
0.32
0.31
0.34
0.24
0.30

W/H
0.80
0.75
0.88
0.73
0.65
0.58
0.76
0.62
0.52
0.56
0.45
0.56
0.56
0.58
0.59
0.60
0.48
0.51

Discussion: NMNS PM23475 has a very
similar shell morphology to the type specimens of Xenoceltites variocostatus, but most
specimens described herein exhibit a slightly
narrower umbilicus at comparable shell sizes.
Because the other shell features are very similar to those of the types, our specimens are
considered to be assignable to X. variocostatus. Close scrutiny of the type specimens together with the Vietnam specimens reveals
that this species displays a wide range of intra-Olenekian (Early Triassic) in northeastern Vietnam

Fig. 48. Xenoceltites variocostatus Brayard and Bucher, 2008 from KC02-10. 1–4, NMNS PM23486. 5–8,
NMNS PM23487. 9–12, NMNS PM23488.

73

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 49. Xenoceltites variocostatus Brayard and Bucher, 2008. 1–4, NMNS PM23475, from NT01-07. 5–8,
NMNS PM23483, from NT01-04. 9–12, NMNS PM23484, from NT01-05. 13–14, NMNS PM23476, fromNT01-07. 15–18, NMNS PM23477, from NT01-07. 19–20, NMNS PM23478, from NT01-07. 21–24, NMNS
PM23479, from NT01-07. 25–26, NMNS PM23485, from NT01-06.

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 50. Xenoceltites variocostatus Brayard and Bucher, 2008 from NT01-07. 1–4, NMNS PM23480. 5–8,
NMNS PM23481. 9–12, NMNS PM23482.

75

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 51. Xenoceltites variocostatus Brayard and Bucher, 2008. 1, NMNS PM23492, from NT01-07. 2, NMNS
PM23493, from NT01-07. 3–4, NMNS PM23494, from NT01-07. 5–7, NMNS PM23495, from NT01-07.
8–11, NMNS PM23496, from NT01-07. 12–14, NMNS PM2497, from NT01-07. 15–16, NMNS PM23498,
from NT01-09. 17–20, NMNS PM23489, from BR01-05. 21, NMNS PM23484, from NT01-05.

specific variation with respect to umbilical diameter.
Specimens described as Xenoceltites cf.
variocostatus by Brühwiler et al. (2010) fromSouth Tibet, Brühwiler et al. (2012b) from theSalt Range and Brühwiler et al. (2012c) from
Spiti all have slightly thinner whorls than thetypes, but otherwise are very similar. Thisvariation almost certainly should be included
within the intraspecific variation of X. variocostatus.
Xenoceltites compressus Chao, 1959 from
the Middle Smithian of South China is very
close to X. variocostatus, but differs by its
slightly phylloid saddles. It possibly should be

assigned to Subflemingites Spath, 1934.
Occurrence: Described specimens fromNT01-04 to NT01-07, NT01-09, KC02-10 and
BR01-05 within the portion of the Novispathodus pingdingshanensis Zone represented by
the Xenoceltites variocostatus beds (Upper
Smithian = upper Lower Olenekian) in the Bac
Thuy Formation, northeastern Vietnam. This
species also occurs in the Upper Smithian inSouth China (Anasibirites multiformis beds,
Brayard and Bucher, 2008), South Tibet(Glyptophiceras sinuatum beds, Brühwiler etal., 2010), Spiti (Subvishnuites posterus beds,
Brühwiler et al., 2012c) and the Salt Range(Glyptophiceras sinuatum beds, Brühwiler etOlenekian (Early Triassic) in northeastern Vietnam

Fig. 52. Xenoceltites? sp. indet. 1, NMNS PM23640, from KC02-11. 2, NMNS PM23641, from KC02-11. 3,
NMNS PM23642, from KC02-11. 4–8, rubber casts of outer molds. 4, NMNS PM23643, from KC02-15. 5,
NMNS PM23644, from KC02-15. 6, NMNS PM23645, from KC02-14. 7, NMNS PM23761, from KC02-12.
8, NMNS PM23490, from BT02-05. 9, NMNS PM23491, from BT02-05.

77

78

Shigeta, Komatsu, Maekawa and Dang (eds.)al., 2012b).
Xenoceltites? sp. indet.
Fig. 52

Material examined: Two specimens,
NMNS PM23490–23491, from BT02-05,
three specimens, NMNS PM23640–23642,
from KC02-11, one specimen, NMNS
PM23761, from KC02-12, and three specimens, NMNS PM23643–23645, from KC0215.
Description: Fairly evolute, very compressed shell with elliptical whorl section,rounded to subacute venter, indistinct ventral
shoulders, and slightly convex flanks withmaximum whorl width at mid-flank. Umbilicus moderately wide with low, nearly verticalwall and rounded shoulders. Ornamentationconsists of low, weak, fold-type ribs. Suture
not visible.
Discussion: Assignment of these specimens to Xenoceltites is uncertain because of
their poor preservation and is based only on
the similarity of their morphology with Xenoceltites.
Occurrence: Described specimens from
KC02-11 within the portion of the Novispathodus pingdingshanensis Zone that includes the
Tirolites cf. cassianus beds (lowest Lower
Spathian = lowest Upper Olenekian), and those
form KC02-12 and KC02-15 within the portion of the Triasssospathodus symmetricus
Zone that includes the Tirolites cf. cassianus
beds (lowest Lower Spathian = lowest Upper
Olenekian) and Tirolites sp. nov. beds (Lower
Spathian = lower Upper Olenekian) and fromBT02-05, whose horizon probably lies within
the the Tirolites cf. cassianus beds in the Bac
Thuy Formation, northeastern Vietnam.

Superfamily Meekoceratoidea Waagen, 1895
Family Proptychitidae Waagen, 1895
Genus Pseudaspidites Spath, 1934
Type species: Aspidites muthianus Kraft
and Diener, 1909.
Pseudaspidites muthianus (Krafft and Diener,
1909)
Figs. 53–56
Aspidites muthianus Krafft and Diener, 1909, p. 59, pl. 6,
fig. 5, pl. 15, figs. 1–2.
Clypeoceras lenticulare Chao, 1959, p. 225, pl. 12, figs.
3–5, text-fig. 19b.
Clypeoceras kwangiense Chao, 1959, p. 226, pl. 17, figs.
1–2, text-fig. 19a.
Pseudaspidites lolouensis Chao, 1959, p. 229, pl. 13, figs.
17–21, text-figs. 20a, 21a.
Pseudaspidites kwangsianus Chao, 1959, p. 230, pl. 12,
figs. 6–8, text-fig. 21d.
Pseudaspidites simplex Chao, 1959, p. 231, pl. 13, figs.
6–13, pl. 45, figs. 5–7, text-figs. 20b, 21b.
Pseudaspidites stenosellatus Chao, 1959, p. 231, pl. 13,
figs. 4–5, pl. 45, fig. 8, text-fig. 21c.
Pseudaspidites aberrans Chao, 1959, p. 232, pl. 13, figs.
14–15, text-fig. 20d.
Pseudaspidites longisellatus Chao, 1959, p. 232, pl. 13,
figs. 1–3, text-fig. 20c.
Proptychites hemialis var. involutus Chao, 1959, p. 237,
pl. 15, figs. 13–16, text-fig. 24d.
Proptychites markhami Chao, 1959, p. 239, pl. 15, figs.
3–5, text-fig. 23c.
Proptychites sinensis Chao, 1959, p. 240, pl. 16, figs. 5–6,
pl. 17, figs. 14–16, text-fig. 22c.
Proptychites angusellatus Chao, 1959, p. 240, pl. 15, figs.
1–2.
Proptychites aff. trilobatus Waagen, 1895. Chao, 1959, p.
241, pl. 16, figs. 11–12, text-fig. 24c.
Proptychites latilobatus Chao, 1959, p. 243, pl. 16, figs.
1–2, pl. 19, figs. 4–5.
Proptychites abnormalis Chao, 1959, p. 243, pl. 16, figs.
3–4.
Proptychites sp. A. Chao, 1959, p. 243, pl. 15, figs. 9–12.
Ussuriceras sp. Chao, 1959, p. 247, pl. 19, fig. 1.
Pseudohedenstroemia magna Chao, 1959, p. 265, pl. 41,
figs. 13–16, pl. 45, figs. 1–2, text-fig. 32b.
Pseudaspidites muthianus (Krafft and Diener, 1909). Brayard and Bucher, 2008, p. 33, pl. 10, figs. 1–10, pl.
扌Fig. 53. Pseudaspidites muthianus (Krafft and Diener, 1909). 1–2, NMNS PM23505, from BT01-11. 3–4,
NMNS PM23503, from BT01-05.

Olenekian (Early Triassic) in northeastern Vietnam

79

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 54. 1–4, Pseudaspidites muthianus (Krafft and Diener, 1909), NMNS PM23504, from BT01-09.

11, figs. 1–4, text-fig. 31; Brühwiler et al., 2012c, p.
136, figs. 14M–R.
Pseudaspidites sp. Brühwiler et al., 2010, p. 413, fig.
7.11a-e.
non Pseudaspidites cf. muthianus (Krafft and Diener,
1909). Brühwiler et al., 2012a, p. 17, pl. 3, figs. 3–5.
Pseudaspidites cf. muthianus (Krafft and Diener, 1909).
Brühwiler et al., 2012b, p. 53, figs. 37A–B, I.

Lectotype: Specimen designated by Spath(1934, p. 163), is GSI 9404, original of Krafft
and Diener (1909, p. 59, pl. 6, fig. 5) from the“Hedenstroemia” beds at Mud, Spiti area,
northwest Himalayan region.
Material examined: Three specimens,
NMNS PM23499–23501, from BT01-03, one
specimen, NMNS PM23502, from BT01-04,
one specimen, NMNS PM23503, from BT0105, one specimen, NMNS PM23504, fromBT01-09, and one specimen, NMNS PM23505,
from BT01-11.
Description: Very involute, very compressed shell with elliptical whorl section,arched venter (juveniles) or subtabulate venter(mature), indistinct ventral shoulders, andslightly convex flanks with maximum whorl
width at mid-flank. Narrow umbilicus withmoderately high, vertical wall and roundedshoulders. Ornamentation consists of weak radial folds. Suture ceratitic. Lateral saddle elongated, and second saddle slanted slightly toward umbilicus. First lateral lobe deep, widewith many denticulations at base, and second
lateral lobe about two thirds depth of first lobe.
Measurements (mm):Specimen no.
NMNS PM23500

D
61.0

U
H
W U/D W/H
7.8 31.7 16.5 0.13 0.52
扌Fig. 55. 1–4, Pseudaspidites muthianus (Krafft and Diener, 1909), NMNS PM23499, from BT01-03.

Olenekian (Early Triassic) in northeastern Vietnam

81

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 56. Pseudaspidites muthianus (Krafft and Diener, 1909). 1–2, NMNS PM234502, from BT01-04. 3–4,
NMNS PM23500, from BT01-03. 5–8, NMNS PM23501, from BT01-03.

Olenekian (Early Triassic) in northeastern Vietnam
NMNS PM23504 73.0 10.1 40.0 19.2
NMNS PM23501 78.0 8.5 ——NMNS PM23499 87.0 12.0 46.5 20.5
NMNS PM23505 105.5 17.0 52.0 28.0
NMNS PM23503 —— 64.0 33.0

0.14
0.11
0.14
0.16
—

0.48
—
0.44
0.54
0.52

Discussion: Brayard and Bucher (2008)
discussed and illustrated the intraspecific variation of Pseudaspidites muthianus from South
China and synonymized many species described by Chao (1959). we agree with theiranalysis. According to this demonstrated range
of intraspecific variation, a specimen described as Pseudaspidites sp. by Brühwiler etal. (2010) from South Tibet should be included within the intraspecific variation of P. muthianus. A specimen from the Salt Range described as P. cf. muthianus by Brühwiler et al.
(2012b) is more evolute than specimens of P.
muthianus of comparative size from South
China and Spiti. This particular specimen may
represent an evolute variant as stated by Brühwiler et al. (2012b, p. 53), because it otherwise is very similar. In contrast, specimens described as P. cf. muthianus by Brühwiler et al.
(2012a) from exotic blocks in Oman have asubammonitic suture that is very similar tothat of Ussuritid ammonoids. These specimens
probably should be assigned to Ussuritids.
Smith (1932) described three specimensfrom Idaho as Clypeoceras muthianum, andKummel and Steele (1962) later erected Pseudaspidites wheeleri based on these three specimens (Smith, 1932, pl. 27, figs. 1, 2). This
species differs from P. muthianus by its much
more involute coiling.
Occurrence: Described specimens fromBT01-03, BT01-04, BT01-05, BT01-09 andBT01-11 within the portion of the Novispathodus ex gr. waageni Zone that includes theFlemingites rursiradiatus beds (lowest Middle
Smithian = middle Lower Olenekian) and Urdyceras tulongensis beds (lower Middle Smithian = middle Lower Olenekian) in the Bac
Thuy Formation, northeastern Vietnam. This
species also occurs in the Middle Smithian inSouth China (Flemingites rursiradiatus beds

83

and Owenites koeneni beds, Brayard and Bucher, 2008), South Tibet (Brayardites compressus beds, Brühwiler et al., 2010), Spiti(Brayardites compressus beds and Escarguelites spitiensis horizon, Brühwiler et al.,2012c), and the Salt Range (Radioceras evolvens beds, Brühwiler et al., 2012b).
Genus Leyeceras Brayard and Bucher, 2008
Type species: Leyeceras rothi Brayard andBucher, 2008.
Leyeceras rothi Brayard and Bucher, 2008
Figs. 57–62
Leyeceras rothi Brayard and Bucher, 2008, p. 39, pl. 14,
figs. 1–3.
? Leyeceras cf. rothi Brayard and Bucher, 2008. Brühwiler et al., 2012a, p. 18, pl. 5, figs. 1–5, pl. 6, figs. 1–3.

Holotype: PIMUZ 25964, figured by Brayard and Bucher (2008, p. 39, pl. 14, fig. 3),
from the Owenites koeneni beds in Jinya,
northwestern Guangxi, South China.
Material examined: Two specimens,
NMNS PM23518–23519, from BT02-03, one
specimen, NMNS PM23520, from a float
limestone block at PK01, one specimen,
NMNS PM23521, from KC01-11, two specimens, NMNS PM23514, 23522, from KC0113, and one specimen, NMNS PM23523, froma float limestone block at BT02.
Description: Moderately evolute, very
compressed shell with elliptical whorl section,arched or subtabulate venter, indistinct ventral
shoulders, and slightly convex flanks withmaximum whorl width near mid-flank. Fairly
narrow umbilicus with moderately high, vertical wall and rounded shoulders. Ornamentation consists only of radial lirae. Suture ceratitic. Lateral saddle elongated, and second saddle slanted slightly toward umbilicus. First lateral lobe deep, wide with many denticulations
at base, and second lateral lobe about two
thirds depth of first lobe.
Measurements (mm):Specimen no.

D

U

H

W

U/D W/H

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 57. Leyeceras rothi Brayard and Bucher, 2008, from BT02-03. 1–2, NMNS PM23518. 3–6, NMNS
PM23519.

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 58. Leyeceras rothi Brayard and Bucher, 2008, NMNS PM23523, from a float limestone block at BT02.

85

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 59.

Leyeceras rothi Brayard and Bucher, 2008, NMNS PM23523, from a float limestone block at BT02.

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 60.

Leyeceras rothi Brayard and Bucher, 2008, NMNS PM23523, from a float limestone block at BT02.

87

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 61. Leyeceras rothi Brayard and Bucher, 2008, from KC01-13. 1–2, NMNS PM23522. 3–5, NMNS
PM23514.

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 62. Leyeceras rothi Brayard and Bucher, 2008. 1–2, NMNS PM23520, from a float limestone block at
PK01. 3–4, NMNS PM23521, from KC01-11.

89

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Shigeta, Komatsu, Maekawa and Dang (eds.)

NMNS PM23519 61.0
NMNS PM23518 89.0
NMNS PM23520 94.0
NMNS PM23521 100.2
NMNS PM23522 138.5
NMNS PM23523 163.0

12.8
20.2
21.7
23.0
28.8
39.5

31.0
40.0
43.0
46.0
68.4
75.0

17.0
—
10.5
—
29.0
31.0

0.21
0.23
0.23
0.23
0.21
0.24

0.55
—
0.48
—
0.42
0.41

Discussion: Specimens described as
Leyeceras cf. rothi by Brühwiler et al. (2012a)from Oman have more convex flanks than thetype specimens of L. rothi from South China,
but otherwise are very similar. They may beconspecific with L. rothi.
Occurrence: Described specimens fromBT02-03, KC01-11 and KC01-13 within the
portion of the Novispathodus ex gr. waageni
Zone that includes the Leyeceras horizon of
the Owenites koeneni beds (middle Middle
Smithian = middle Lower Olenekian) in the
Bac Thuy Formation, northeastern Vietnam.
This species also occurs in the Middle Smithian in South China (Owenites koeneni beds,
Brayard and Bucher, 2008).
Genus Guodunites Brayard and Bucher, 2008
Type species: Guodunites monneti Brayard
and Bucher, 2008.
Guodunites monneti
Brayard and Bucher, 2008
Fig. 63
Guodunites monneti Brayard and Bucher, 2008, p. 83, pl.
44, figs. 1–2; Brayard et al., 2009, p. 473, pl. 1, figs.
1–14, text-fig. 3A–C; Brühwiler et al., 2012a, p. 19,
pl. 7, figs. 1–5.
? Guodunites cf. monneti Brayard and Bucher, 2008.
Jenks et al., 2010, p. 10, figs. 6A–D, 7.
Guodunites cf. monneti Brayard and Bucher, 2008. Jenkset al., 2010, p. 10, fig. 6E–H.

Holotype: PIMUZ 26193, figured by Brayard and Bucher (2008, p. 83, pl. 44, fig. 1),
from the Owenites koeneni beds in Jinya,
northwestern Guangxi, South China.
Material examined: Three specimens,
NMNS PM23515–23517, from KC02-02.
Description: Fairly involute, very compressed shell with narrowly rounded venter,

indistinct ventral shoulders, and slightly convex flanks with maximum whorl width near
mid-flank. Umbilicus fairly narrow with gently inclined wall. Ornamentation consists ofdistinct, fine strigation on flanks disappearing
on venter as well as slightly biconcave growthlines that become strongly projected on ventral
shoulders. Suture line not well preserved.
Measurements (mm):Specimen no.
DUH
W U/D W/H
NMNS PM23515 29.2 7.7 13.4 7.3 0.26 0.54
NMNS PM23516 59.1 11.4 27.3 12.0 0.19 0.44

Discussion: Jenks et al. (2010) describedfour medium-sized specimens as Guodunites
cf. monneti from western USA. One specimen(Jenks et al., 2010, fig. 6E–H) is nearly identical to G. monneti from Oman and South China
and is clearly conspecific with G. monneti.
However, the other three specimens have amuch wider umbilicus (U/D: 0.25–0.27, Jenkset al., 2010, table 4) than G. monneti (U/D:
0.18–0.20, Brayard et al., 2009, table 1). They
may belong to a more evolute form of G. monneti.
A poorly preserved specimen described as
Owenites slavini (Popov, 1962) by Kummel
and Erben (1968, p. 124, pl. 21, figs. 3–4;
GPIBo. 24) from Afghanistan is characterized
as having a very compressed shell with a narrowly rounded venter and slightly convex
flanks ornamentated by strigation. The specimen is somewhat similar to Guodunites monneti as stated by Brayard et al. (2009, p. 476),
but differs by stronger strigation covering its
flanks and venter. G. monneti has fine strigation on its flanks, but it disappears on the venter. Kummel and Erben’s (1968) specimen is
not conspecific with G. monneti.
Occurrence: Described specimen from
KC02-02 within the portion of the Novispathodus ex gr. waageni Zone that includes the
Guodunites horizon of the Owenites koeneni
beds (upper Middle Smithian = middle Lower
Olenekian) in the Bac Thuy Formation, northeastern Vietnam. This species also occurs in
the Middle Smithian in South China (Owenites

Olenekian (Early Triassic) in northeastern Vietnam

91

Fig. 63. Guodunites monneti Brayard and Bucher, 2008, from KC02-02. 1–2, NMNS PM23515. 3–4, NMNS
PM23516. 5–6, NMNS PM23517.

koeneni beds, Brayard and Bucher, 2008),
Oman (Owenites koeneni fauna, Brühwiler etal., 2012a), and western USA (Meekoceras
gracilitatis Zone, Jenks et al., 2010).
Family Dieneroceratidae Spath, 1934
Genus Dieneroceras Spath, 1934
Type species: Ophiceras dieneri Hyatt andSmith, 1905.
Dieneroceras? goudemandi (Brayard andBucher, 2008)
Figs. 64–66?Dieneroceras tientungense Chao, 1959, p. 192, pl. 2, figs.
5–6, 8–10, 29.
?Dieneroceras? vermiforme Chao, 1959, p. 192, pl. 2, figs.
14–16, 28, text-fig. 7b.
?Dieneroceras ovale Chao, 1959, p. 192, pl. 2, figs. 11–
13, text-fig. 7a.
Pseudoflemingites goudemandi Brayard and Bucher, 2008,

p. 49, pl. 22, figs. 1–5, text-fig. 44.
Pseudoflemingites goudemandi Brayard and Bucher, 2008.
Brühwiler et al., 2012a, p. 24, pl. 14, figs. 4–5.

Holotype: PIMUZ 26004, figured by Brayard and Bucher (2008, p. 49, pl. 22, fig. 2),
from the Owenites koeneni beds in Jinya,
northwestern Guangxi, South China.
Material examined: one specimen, NMNS
PM23546, from KC01-01, one specimen,
NMNS PM23547, from KC01-10, one specimen, NMNS PM23548, from KC01-11, six
specimens, NMNS PM23549–23554, from
KC01-13, one specimen, NMNS PM23555,
from KC02-02, three specimens, NMNS
PM23556–23558, from BT02-03, and two
specimens, NMNS PM23559–23560, fromBT01-14.
Description: Very evolute, fairly compressed shell with elliptical whorl section,subtabulate venter, slightly rounded shoulders,92

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 64. Dieneroceras? goudemandi (Brayard and Bucher, 2008). 1–2, NMNS PM23556, from BT02-03. 3–6,
NMNS PM23557, from BT02-03. 7–8, NMNS PM23558, from BT02-03. 9–10, NMNS PM23559, fromBT01-14. 11–13, NMNS PM23560, from BT01-14.

Olenekian (Early Triassic) in northeastern Vietnam

93

Fig. 65. Dieneroceras? goudemandi (Brayard and Bucher, 2008), from KC01-13. 1–4, NMNS PM23552. 5–6,
NMNS PM23553. 7–9, NMNS PM23554.

and slightly convex flanks with maximum
whorl width at mid-flank. Umbilicus fairly
wide with low, nearly vertical wall and rounded shoulders. Surface smooth or ornamented
with weak radial folds. Suture ceratitic. First
lateral saddle nearly equal to second saddle,
and third saddle lower than second saddle.
First lateral lobe deep, wide with many denticulations at base, and second lateral lobe half
depth of first lobe.
Measurements (mm):Specimen no.

D

U

H

W

U/D W/HNMNS PM23557
NMNS PM23549
NMNS PM23553
NMNS PM23555
NMNS PM23550
NMNS PM23546
NMNS PM23554
NMNS PM23559
NMNS PM23547
NMNS PM23558
NMNS PM23560
NMNS PM23552
NMNS PM23551

23.0
25.0
25.8
26.9
30.2
32.6
35.3
39.0
52.5
54.0
55.6
60.1
73.8

10.7
11.4
12.3
13.7
13.8
14.0
15.1
19.2
25.6
25.9
23.8
28.0
34.3

7.1
6.8
8.3
7.3
9.5
11.0
11.1
11.1
16.0
15.3
18.0
17.7
21.2

6.0
4.4
7.4
6.6
6.7
—
8.3
8.0
—
11.0
11.2
12.8
14.0

0.47
0.46
0.48
0.51
0.46
0.43
0.43
0.49
0.49
0.48
0.43
0.47
0.46

0.85
0.65
0.89
0.90
0.72
—
0.75
0.72
—
0.72
0.62
0.72
0.66

94

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 66. Dieneroceras? goudemandi (Brayard and Bucher, 2008). 1, NMNS PM23546, from KC01-01. 2–3,
NMNS PM23547, from KC01-10. 4–5, NMNS PM23548, from KC01-11. 6–7, NMNS PM23549, from
KC01-13. 8–9, NMNS PM23550, from KC01-13. 10–11, NMNS PM23551, from KC01-13. 12–13, NMNS
PM23555, from KC02-02.

Olenekian (Early Triassic) in northeastern Vietnam
NMNS PM23556 91.0 43.1 28.0 15.3 0.47 0.55

Flemingites rursiradiatus Chao, 1959

Discussion: Brayard and Bucher (2008) attributed this species to Pseudoflemingites
Spath, 1930, but their specimens’ elliptical
whorl section, subtabulate venter and slightly
rounded ventral shoulders do not agree wellwith the diagnostic characters of Pseudoflemingites, which has a narrowly rounded venterand indistinct shoulders. Even though theoverall shell morphology of this species issimilar to that of Dieneroceras, the smooth
shell surface differs from Dieneroceras, which
is characterized by fine strigation. Therefore,
the assignment to this genus is questionable.
Chao (1959) described three new species,
Dieneroceras tientungense, D.? vermiforme,
and D. ovale, from the middle Smithian(Owenitan) of South China. Their shells,
which are less than 4 cm in diameter, are very
similar to the inner whorls of the type specimens of Pseudoflemingites goudemandi Brayard and Bucher, 2008. Ultimately, they may
be shown to be conspecific with this taxon, but
further taxonomic studies are necessary toconfirm this attribution.
Occurrence: Described specimen from
KC01-01, KC01-010, KC01-11, KC01-13,
KC02-02, BT02-03 and BT01-14 within the
portion of the Novispathodus ex gr. waageni
Zone that includes the Owenites koeneni beds
(middle to upper Middle Smithian = middle
Lower Olenekian) in the Bac Thuy Formation,
northeastern Vietnam. This species also occurs
in the Middle Smithian in South China(Owenites koeneni beds, Brayard and Bucher,2008) and Oman (Owenites koeneni fauna,
Brühwiler et al., 2012a).

Figs. 67, 68.1

Family Flemingitidae Hyatt, 1900
Genus Flemingites Waagen, 1895
Type species: Ceratites flemingianus deKoninck, 1863.

95?Flemingites evolutus Chao, 1959, p. 204, pl. 7, figs. 13–
14, pl. 8, figs. 5–6, text-fig. 12c.
?Flemingites nalilingensis Chao, 1959, p. 205, pl. 6, figs.
6–7, text-fig. 12d.
Flemingites rursiradiatus Chao, 1959, p. 205, pl. 6, figs.
1–5, 8–10, text-fig. 13; Brayard and Bucher, 2008, p.
44, pl. 18, figs. 1–7, pl. 9, figs. 1–3, text-fig. 39;
Brühwiler et al., 2012a, p. 20, pl. 12, figs. 1–5.
Flemingites ellipticus Chao, 1959, p. 206, pl. 4, figs. 5–7,
10–12, text-fig. 12a.
?Flemingites ellipticus var. kaohwaiensis Chao, 1959, p.
207, pl. 4, figs. 8–9.
Flemingites kwangsiensis Chao, 1959, p. 208, pl. 8, fig. 8.
Flemingites cf. rursiradiatus Chao, 1959. Vu Khuc, 1984,
p. 34, pl. 1, figs. 4–5; Vu Khuc, 1991, p. 122, pl. 46,
figs. 2–3.
Flemingites aff. flemingianus (de Koninck, 1863). Vu
Khuc, 1984, p. 34, pl. 3, fig. 2; Vu Khuc, 1991, p.
122, pl. 46, fig. 1.
Flemingites flemingianus (de Koninck, 1863). Brayard
and Bucher, 2008, p. 44, pl. 17, figs. 1–5, text-fig. 38.

Holotype: NIGP 12174, figured by Chao
(1959, p. 205, pl. 6, figs. 8–10), from theFlemingitan (lower Smithian) in the Linglo
district (Lolou), western Guangxi, South
China.
Material examined: Five specimens,
NMNS PM23506–23509, 23513 from BT0103, one specimen, NMNS PM23510, fromBT01-05 and one specimen, NMNS
PM23511, from BT02-01.
Description: Very evolute, fairly compressed shell with elliptical to subquadratic
whorl section, subtabulate venter, roundedventral shoulders, and slightly convex flanks
with maximum whorl width at mid-flank. Umbilicus fairly wide with moderately high, nearly vertical wall and rounded shoulders. Ornamentation consists of conspicuous, dense strigation covering entire shell and variable
strength, radial to conspicuous rursiradiate ribs
arising on umbilical shoulder and fading awayon ventral shoulder. Suture not preserved.
Measurements (mm):Specimen no.
DUH
W U/D W/H
NMNS PM23513 21.0 10.1 13.0 10.0 0.41 0.77

96

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 67. Flemingites rursiradiatus Chao, 1959. 1–3, NMNS PM23511, from BT02-01. 4–5, NMNS PM23513,
from BT01-03. 6, NMNS PM23506 (rubber cast of outer mold), from BT01-03. 7, NMNS PM23509 (rubber
cast of outer mold), from BT01-03. 8–9, NMNS PM23508, from BT01-03. 10, NMNS PM23510, from BT0105.

Olenekian (Early Triassic) in northeastern Vietnam

97

Fig. 68. 1, Flemingites rursiradiatus Chao, 1959, NMNS PM23507, from BT01-03. 2, Euflemingites sp. indet.,
NMNS PM23512 (rubber cast of outer mold), from a float limestone block at BT02.

NMNS PM23506 47.0 19.5 7.3 6.1 0.48 0.84
NMNS PM23508 69.5 31.0 20.5 14.5 0.45 0.71
NMNS PM23507 85.0 39.0 —— 0.46 —NMNS PM23511 —— 31.0 17.0 — 0.55

Discussion: Brayard and Bucher (2008)
collected many specimens assignable to Flemingites from a 3 m thick limestone bed in the
Luolou Formation, South China and identified
them as Flemingites rursiradiatus, F. flemingianus and F. radiates. Brühwiler et al.
(2012b, p. 68) later pointed out that specimens
described as F. flemingianus by Brayard andBucher (2008) differ from that taxon by theirmore evolute coiling and lower whorl heightat comparable size, and stated that they may
represent a weakly ribbed variant of F. rursiradiatus. Specimens assigned to F. rursiradiatus by Brayard and Bucher (2008) exhibit awide range of intraspecific variation and they
include forms very similar to the types of F.
ellipticus and F. kwangsiensis erected by Chao
(1959). This evidence suggests that these two
species of Chao are conspecific. Chao’s otherspecies, F. evolutus, F. nalilingensis and F. ellipticus var. kaohwaiensis are also very similar
to juveniles of F. rursiradiatus, but it is questionable whether they are conspecific because
their ornamentation is poorly preserved.
Occurrence: Described specimens fromBT01-03, BT01-05 and BT02-01 within the
portion of the Novispathodus ex gr. waageni
Zone that includes the Flemingites rursiradiatus beds (lowest Middle Smithian = middle
Lower Olenekian) in the Bac Thuy Formation,
northeastern Vietnam. This species also occurs
in the lowest Middle Smithian in South China(Flemingites rursiradiatus beds, Brayard andBucher, 2008) and Oman (Flemingites rursiradiatus fauna, Brühwiler et al., 2012a).
Genus Euflemingites Spath, 1934
Type species: Flemingites guyerdetiformis
Welter, 1922.

98

Shigeta, Komatsu, Maekawa and Dang (eds.)

Euflemingites sp. indet.
Fig. 68.2

Material examined: One specimen, NMNS
PM23512, from a float limestone block at
BT02.
Description: Moderately evolute, very
compressed shell with rounded venter, indistinct ventral shoulders, and gently convex
flanks forming an elliptical whorl section withmaximum whorl width at mid-flank. Umbilicus fairly narrow with moderately high, vertical wall and rounded shoulders. Ornamentation consists of conspicuous, dense strigation
covering entire shell. Spiral ridges number
about 25 between umbilical shoulders andmid-line of venter. Suture not preserved.
Discussion: The described specimen isvery similar to Euflemingites tsotengensis
Chao, 1959 from South China, E. guyerdetiformis (Welter, 1922) from Timor, E. prynadai(Kiparisova, 1947) from South Primorye andE. cirratus (White, 1879) from western USA,but the fragmental nature of the specimen precludes a definitive species assignment.
Occurrence: Described specimen was
found in a float limestone block at BT02. Although the exact horizon from which the block
originated is uncertain, judging from the locality where it was found, it certainly came froma limestone bed (Middle Smithian) in the Bac
Thuy Formation, northeastern Vietnam.
Genus Anaflemingites Kummel and Steele,
1962Type species: Anaflemingites silberlingi
Kummel and Steele, 1962.
Anaflemingites hochulii Brayard and Bucher,2008
Figs. 69–72
Anaflemingites hochulii Brayard and Bucher, 2008, p. 51,
pl. 23, figs. 3–6, text-fig. 45.
Subflemingites involutus (Welter, 1922). Brühwiler et al.,2012a, p. 23, pl. 13, figs. 1–3.

Holotype: PIMUZ 26020, figured by Brayard and Bucher (2008, p. 51, pl. 24, fig. 5),
from the Owenites koeneni beds in Jinya,
northwestern Guangxi, South China.
Material examined: Three specimens,
NMNS PM23773–23775, from float limestone
blocks at BT02 and five specimens, NMNS
PM23776–23780, from KC01-13.
Description: Moderate to fairly evolute,
very compressed shell with elliptical whorl
section, rounded venter, indistinct ventral
shoulders, and slightly convex flanks withmaximum whorl width at mid-flank. Umbilicus moderately wide with low, gently sloped
wall and rounded shoulders. Ornamentation onjuvenile whorls consists of sinuous growthlines and weak strigation near venter. Suture
ceratitic. First lateral saddle lower than second
saddle. First and second lateral lobes deep,
wide with many denticulations at base.
Measurements (mm):Specimen no.
D
NMNS PM23774 33.8
NMNS PM23773 43.0
NMNS PM23775 60.2
NMNS PM23776 82.2
NMNS PM23780 151.3

U
11.2
14.8
18.8
25.6
51.9

H
13.5
16.2
28.2
34.0
58.3

W
8.7
10.9
13.2
14.0
21.7

U/D
0.33
0.34
0.31
0.31
0.34

W/H
0.64
0.67
0.47
0.41
0.37

Discussion: Specimens described as Subflemingites involutus (Welter, 1922) by Brühwiler et al. (2012a) from Oman are very similar to Anaflemingites hochulii, and are clearlyconspecific. A. silberlingi Kummel and Steele,
1962 from western USA is also very close to
A. hochulii, but differs by the fine strigationthat covers its entire shell (Jenks et al., 2010).
Occurrence: Described specimens from
KC01-13 within the portion of the Novispathodus ex gr. waageni Zone that includes the
Leyeceras horizon of the Owenites koeneni
beds (middle Middle Smithian = middle Lower
Olenekian) in the Bac Thuy Formation, northeastern Vietnam. This species also occurs in
the Middle Smithian in South China (Owenites
koeneni beds, Brayard and Bucher, 2008) andOman (Owenites koeneni fauna, Brühwiler etal., 2012a).

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 69. Anaflemingites hochulii Brayard and Bucher, 2008, from float limestone blocks at BT02. 1–5, NMNS
PM23773. 6–10, NMNS PM23774. 11–14, NMNS PM23775.

99

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 70.

Anaflemingites hochulii Brayard and Bucher, 2008. NMNS PM23780, from KC01-13.

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 71.

Anaflemingites hochulii Brayard and Bucher, 2008. NMNS PM23780, from KC01-13.

101

102

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 72. Anaflemingites hochulii Brayard and Bucher, 2008, from KC01-13. 1–2, NMNS PM23776. 3–4, NMNS
PM23777. 5–6, NMNS PM23778. 7–8, NMNS PM23779.

Olenekian (Early Triassic) in northeastern Vietnam

Family Galfettitidae Brühwiler et al., 2010
Genus Galfettites Brayard and Bucher, 2008
Type species: Galfettites simplicitatis Brayard and Bucher, 2008.
Revised diagnosis: Laterally compressed
Galfettitidae with flat, parallel flanks and narrow tabulate venter.
Discussion: Brayard and Bucher (2008)
described the venter of the type species of thisgenus, Galfettites simplicitatis as narrowly
curved to subtabulate. However, the ventral
part of their type specimens is poorly preserved. Recently, Brühwiler et al. (2012a)
studied and illustrated many well-preserved
specimens assignable to Galfettites from
Oman and stated that the taxon’s venter is tabulate. Jenks et al. (2010) earlier reported thatspecimens referable to Galfettites from Nevada also have a tabulate venter. Therefore,
the original diagnosis of the genus with regard
to its venter is revised from a “narrowly
curved venter” to a “narrow tabulate venter”.
Meekoceras wanneri Welter, 1922, matches
well with the revised diagnosis and is herein
assigned to Galfettites.
Galfettites simplicitatis
Bryard and Bucher, 2008
Figs. 73, 74? Meekoceras wanneri Welter, 1922,p. 129, pl. 164, figs.
17–18, pl. 165, figs. 18–19.
Galfettites simplicitatis Brayard and Bucher, 2008, p. 48,
pl. 21, figs. 1–2, text-fig. 43; Brühwiler et al., 2012a,
p. 26, pl. 15, figs. 1–4, pl. 16, fig. 1.

Holotype: PIMUZ 26002, figured by Brayard and Bucher (2008, p. 48, pl. 21, fig. 2),
from the Owenites koeneni beds in Jinya,
northwestern Guangxi, South China.
Material examined: One specimen, NMNS
PM23781, from a float limestone block at
BT02 and two specimens, NMNS PM23782–
23783, from BT01-09.
Description: Very evolute, very compressed shell with angular ventral shoulders,and flat parallel flanks for two-thirds of flank,

103

then gradually converging toward tabulate
venter. Umbilicus moderately wide with low,nearly vertical wall and rounded shoulders.
Ornamentation consists of low, broad, prorsiradiate ribs visible on outer flank. Suture ceratitic with subphylloid saddles. First lateral saddle equal but narrower than second saddle, andthird saddle lower. First lateral lobe deep,
wide with many denticulations at base, andsecond lateral lobe half depth of first lobe.
Measurements (mm):Specimen no.
DUH
W U/D W/H
NMNS PM23783 41.7 15.1 —— 0.36 —NMNS PM23781 93.1 37.5 34.0 15.0 0.40 0.44

Discussion: Brühwiler et al. (2012a) previously recognized the similarity in shape of“Meekoceras” wanneri Welter, 1922 from
Timor and G. simplicitatis, but they hesitatedto synonymize them because the suture line of“M.” wanneri is unknown. However, thesesimilarities in shell morphology and ornamentation provide convincing evidence that thetwo taxa are almost certainly conspecific.
Occurrence: Described specimens fromBT01-09 within the portion of the Novispathodus ex gr. waageni Zone that includes the Urdyceras tulongensis beds (lower Middle Smithian = middle Lower Olenekian) in the Bac
Thuy Formation, northeastern Vietnam. This
species also occurs in the Middle Smithian inSouth China (Owenites koeneni beds, Brayard
and Bucher, 2008) and Oman (Owenites koeneni fauna, Brühwiler et al., 2012a).
Genus Urdyceras Brayard and Bucher, 2008
Type species: Urdyceras insolitus Brayard
and Bucher, 2008.
Urdyceras tulongensis Brühwiler et al., 2010
Fig. 75
Urdyceras tulongensis Brühwiler et al., 2010, p. 416, fig.
10.5–10.11.

Holotype: PIMUZ 27644, figured by
Brühwiler et al. (2010, p. 416, fig. 10.6), fromthe Brayardites compressus beds (lower Mid-

104

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 73. Galfettites simplicitatis Brayard and Bucher, 2008. 1–2, NMNS PM23781, from a float limestone blockat BT02. 3–5, NMNS PM23782, from BT01-09. 6–7, NMNS PM23783, from BT01-09.

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 74.

105

Galfettites simplicitatis Brayard and Bucher, 2008. NMNS PM23781, from BT02-02.

dle Smithian) in Tulong, South Tibet.
Material examined: Four specimens,
NMNS PM23785–23788, from BT01-09 andone specimen, NMNS PM23784, from BT0202.
Description: Moderately evolute, fairly
compressed shell with subrectangular whorl
section, tabulate venter, angular ventral shoulders, and slightly convex flanks with maximum whorl width near umbilical shoulder.
Umbilicus moderately wide with moderately
high, nearly vertical wall and rounded shoulders. Ornamentation consists of strong, radialor slightly rursiradiate ribs arising on umbilical shoulder and fading away on ventral shoul-der. Suture ceratitic. First lateral saddle lower
and narrower than second saddle, and third
saddle lower than second saddle. First laterallobe deep, wide with many denticulations atbase, and second lateral lobe half depth of firstlobe.
Measurements (mm):Specimen no.
NMNS PM23784
NMNS PM23785
NMNS PM23788
NMNS PM23786
NMNS PM23787

D
22.0
25.7
33.4
43.0
74.0

U
H
W U/D
8.2 8.4 6.0 0.37
10.0 8.8 7.6 0.39
11.0 13.0 9.8 0.33
16.7 15.7 11.9 0.39
23.0 34.0 22.0 0.31

W/H
0.71
0.86
0.75
0.79
0.65

Discussion: The described specimens havestronger radial ribs and a wider umbilicus thanthe holotype of Urdyceras tulongensis, but

106

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 75. Urdyceras tulongensis Brühwiler et al., 2010. 1–2, NMNS PM23784, from BT02-02. 3–10, from BT0109. 3–4, NMNS PM23785. 5–6, NMNS PM23786. 7, NMNS PM23787. 8–10, NMNS PM23788.

they are very similar to two of the paratypes(i.e. PIMUZ 27643, 27646; Brühwiler et al.,2010, fig. 10.5, 10.8), which have strong ribson their inner flanks and a moderately wide
umbilicus. Therefore, the described specimens
are considered to fit well within the intraspecific variation of U. tulongensis.
The shell diameters of the type specimensof Urdyceras tulongensis are less than 40 mm.
In contrast, NMNS PM23787 is a partial
whorl section more than 74 mm in diameterthat shares many similarities with U. tulongen­sis, such as a tabulate venter and radial ribs.
This evidence suggests that this particularspecimen is probably an adult shell of U. tu­
longensis.
Occurrence: Described specimens fromBT01-09 and BT02-02 within the portion of
the Novispathodus ex gr. waageni Zone that
includes the Urdyceras tulongensis beds
(lower Middle Smithian = middle Lower Olenekian) in the Bac Thuy Formation, northeastern Vietnam. This species also occurs at thelower Middle Smithian (Brayardites compres­sus beds) in South Tibet (Brühwiler et al.,2010).

Olenekian (Early Triassic) in northeastern Vietnam

Family Arctoceratidae Arthaber, 1911
Genus Submeekoceras Spath, 1934
Type species: Meekoceras mushbachanum
White, 1879.
Submeekoceras hsüyüchieni (Chao, 1959)
Figs. 76–78? Prionolobus ophionus var. involutus Chao, 1959, p. 201,
pl. 9, figs. 11–15, text-fig. 11b.
Prionolobus hsüyüchieni Chao, 1959, p. 202, pl. 9, figs.
9–10, text-fig. 11c.
Paranorites ovalis Chao, 1959, p. 217, pl. 9, figs. 16–19,
text-fig. 16b.
Paranorites linguisellatus Chao, 1959, p. 218, pl. 10, figs.
1–2, text-fig. 16c.
Paranorites aff. linguisellatus Chao, 1959, p. 218, pl. 10,
figs. 3–4.
Meekoceras lativentrosum Chao, 1959, p. 309, pl. 38, figs.
15–18, text-fig. 43a.
Meekoceras densistriatum Chao, 1959, p. 310, pl. 38, figs.
1–3, 19, text-fig. 43b.
Meekoceras yukiangense Chao, 1959, p. 311, pl. 39, figs.
1–7, 13, text-fig. 44a.
Meekoceras kaohwaiense Chao, 1959, p. 311, pl. 40, figs.
16–18, text-fig. 44b.
Meekoceras pulchriforme Chao, 1959, p. 313, pl. 40, figs.
14–15, text-fig. 44c.
Meekoceras (Submeekoceras) subquadratum Chao, 1959,
p. 317, pl. 14, figs. 1–5, pl. 39, figs. 8–9, text-fig.
45c.
Meekoceras (Submeekoceras) quadratum Chao, 1959, p.
318, pl. 39, figs. 10–11, 22–23.
Meekoceras (Submeekoceras) sp. indet. Chao, 1959, p.
319, pl. 40, fig. 20.
Meekoceras (Submeekoceras) lolouense Chao, 1959, p.
320, pl. 10, figs. 7–8, text-fig. 45d.
Meekoceras (Submeekoceras) longiseptatum Chao, 1959,
p. 321, pl. 10, figs. 5–6, text-fig. 46c.
Arctoceras mushbachanum (White, 1879). Kummel andErben, 1968, p. 131, pl. 21, figs. 1–2.
Submeekoceras mushbachanum (White, 1879). Brayard
and Bucher, 2008, p. 52, pl. 16, fig. 4, pl. 26, figs.
1–9, text-fig. 46; Brühwiler et al., 2012a, p. 30, pl.
17, figs. 1–3.

Holotype: NIGP 12119, figured by Chao
(1959, p. 202, pl. 9, figs. 9–10), from theFlemingites bed in the Linglo district (Lolou),western Guangxi, South China.
Material examined: Five specimens,
NMNS PM23624–23628, from BT01-03, two107

specimens, NMNS PM23629–23630, fromBT01-09, one specimen, NMNS PM23631,
from KC01-01, and three specimens, NMNS
PM23632–23634, from float limestone blocks
at BT02.
Description: Moderately evolute, very
compressed shell with elliptical whorl section,arched venter, indistinct ventral shoulders, andslightly convex flanks with maximum whorl
width near mid-flank. Fairly narrow umbilicus
with moderately high, vertical wall and rounded shoulders. Ornamentation consists of sinuous growth lines and weak, fold-type ribs. Suture ceratitic. First and second lateral saddles
narrowly elongated. First lateral lobe deep,
wide with many denticulations at base, andsecond lateral lobe about two thirds depth offirst lobe.
Measurements (mm):Specimen no.
NMNS PM23629
NMNS PM23630
NMNS PM23626
NMNS PM23624
NMNS PM23625
NMNS PM23628
NMNS PM23632
NMNS PM23633
NMNS PM23634

D
35.4
38.6
51.0
51.5
53.9
—
70.3
77.2
—

U
7.5
11.3
11.3
14.4
12.6
17.3
20.3
21.1
28.1

H
16.2
16.3
23.0
21.9
22.5
36.0
28.3
33.0
40.8

W
7.2
7.7
12.5
12.5
12.1
19.7
13.0
18.7
22.6

U/D
0.21
0.29
0.22
0.28
0.23
—
0.29
0.27
—

W/H
0.44
0.47
0.54
0.57
0.54
0.55
0.46
0.57
0.55

Discussion: Even though Chao (1959) firstassigned this species to Prionolobus Waagen,
1895, its shell morphology, which is similar to
Arctoceratidae without umbilical tubercles,
clearly suggests that it belongs to Submeeko­
ceras. This species is very close to type species of the genus, S. mushbachanum (White,
1879), but the latter has a more involute shellwith a narrower umbilicus. Specimens attributed to S. mushbachanum by Brayard and Bucher (2008) from South China are characterized by a more evolute shell with a wider umbilicus than the type specimen of S. mush­bachanum and other illustrated specimens described by Smith (1932) from western USA.
They are herein assigned to S. hsüyüchieni.
Similar specimens were described as compris-108

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 76. Submeekoceras hsüyüchieni (Chao, 1959), from BT01-03. 1–4, NMNS PM23624. 5–8, NMNS
PM23625. 9–11, NMNS PM23626.

Olenekian (Early Triassic) in northeastern Vietnam

109

Fig. 77. Submeekoceras hsüyüchieni (Chao, 1959). 1–4, NMNS PM23629, from BT01-09. 5–6, NMNS
PM23630, from BT01-09. 7, NMNS PM23627, from BT01-03. 8–9, NMNS PM23628 from BT01-03. 10–12,
NMNS PM23631, from KC01-01.

110

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 78. Submeekoceras hsüyüchieni (Chao, 1959), from float limestone blocks at BT02. 1–2, NMNS PM23632.
3–4, NMNS PM23633. 5–6, NMNS PM23634.

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 79.

111

Nammalites sp. indet., from BT02-03. 1–2, NMNS PM23524. 3–4, NMNS PM23525.

ing several different species by Chao (1959,
see above synonymy list), but they probably fit
within the interspecific variation of a single
species because their morphological differences are insignificant. Prionolobus ophionus var.
involutus Chao, 1959 is somewhat similar to
Submeekoceras hsüyüchieni, but it is unclear
if they are conspecific because the type specimen of the former species is very small (diameter ~30 mm) and its preservation is quite
poor.
Occurrence: Described specimens fromBT01-03, BT01-09 and KC01-01 within the
portion of the Novispathodus ex gr. waageni
Zone that includes the Flemingites rursiradia­
tus beds (lowest Middle Smithian = middle
Lower Olenekian) and Urdyceras tulongensis
beds (lower Middle Smithian = middle Lower
Olenekian) in the Bac Thuy Formation, northeastern Vietnam. This species also occurs in
the Middle Smithian in South China (Fleming­
ites rursiradiatus beds and Owenites koeneni
beds, Brayard and Bucher, 2008), Afganistan(Kummel and Erben, 1968), and Oman (Flem­
ingites rursiradiatus fauna and Owenites
koeneni fauna, Brühwiler et al., 2012a).
Genus Nammalites Brühwiler et al., 2010
Type species:(Guex, 1978).

Nammalites

pilatoides

Nammalites sp. indet.
Fig. 79

Material examined: Two specimens,
NMNS PM23524–23525, from BT02-03.
Description: Moderately evolute, fairly
compressed shell with rounded venter, indistinct ventral shoulders, and slightly convex
flanks with maximum whorl width near umbilical shoulder. Umbilicus moderately wide withmoderately high, nearly vertical wall androunded shoulders. Ornamentation consists of
distant, rursiradiate ribs that develop elongatedbullar near umbilicus and fade out toward venter. Suture not well preserved.
Measurements (mm):Specimen no.
DUH
W U/D W/H
NMNS PM23524 40.0 13.4 15.0 11.0 0.34 0.73
NMNS PM23524 34.8 12.5 12.6 9.0 0.36 0.71

Discussion: Even though the present specimens are poorly preserved, their distinctive
features enable me to assign them with reasonable confidence to the genus Nammalites.
They differ from Nammalites pilatoides(Guex, 1978) by their wider umbilicus; thisfeature in combination with their poor preservation precludes a definitive species assignment.
Occurrence: Described specimens fromBT02-03 within the portion of the Novispatho­
dus ex gr. waageni Zone that includes theOwenites koeneni beds (Middle Smithian =112

Shigeta, Komatsu, Maekawa and Dang (eds.)

middle Lower Olenekian) in the Bac Thuy
Formation, northeastern Vietnam.
Family Ussuridae Spath, 1930
Genus Ussuria Diener, 1895
Type species: Ussuria schamarae Diener,
1895.
Ussuria kwangsiana Chao, 1959
Fig. 80
Ussuria kwangsiana Chao, 1959, p. 258, pl. 31, figs.
8–10, pl. 8, text-fig. 30a; Brayard and Bucher, 2008,
p. 54, pl. 27, figs. 1–3, text-fig. 47.
Ussuria pakungiana Chao, 1959, p. 258, pl. 31, figs. 1–3,
pl. 8, text-fig 30c, d.
Ussuria longilobata Chao, 1959, p. 259, pl. 31, figs. 4–7,
pl. 8, text-fig 30b.
Ussuria lenticularis Vu Khuc, 1984, p. 79, pl. 6, fig. 5,
text-fig. 14; Vu Khuc, 1991, p. 140, pl. 47, fig. 4,
text-fig. 4–1.

Holotype: NIGP 12321, figured by Chao
(1959, p. 258, pl. 31, figs. 8–10), from theOwenitan (middle Smithian) in the Tiengno
district (Pakung), western Guangxi, South
China.
Material examined: One specimen, NMNS
PM23526, from BT02-02 and one specimen,
NMNS PM23527, from BT01-09.
Description: Very involute, very compressed oxycone with narrowly rounded venter and gently convex flanks with maximum
width near umbilicus. Umbilicus very narrow
with high, perpendicular wall and roundedshoulders. Shell surface smooth. Suture subammonitic, with distinctly phylloid saddles
and strongly indented lobes.
Measurements (mm):Specimen no.
D
NMNS PM23527 42.1
NMNS PM23526 69.0

U
3.8
4.7

H
W U/D W/H
24.5 10.6 0.09 0.43
41.2 17.7 0.07 0.43

Discussion: Chao (1959) erected Ussuria
pakungiana and U. longilobata from the same
locality as U. kwangsiana in South China.
They are differentiated from U. kwangsiana
only by small differences in their suture line,
but otherwise are very similar. These two taxa

probably represent juvenile whorls of U.
kwangsiana and the difference in suture line isinterpreted to simply be the result of intraspecific variation or ontogenetic variation. According to Brayard and Bucher (2008), U.
kwangsiana has a nearly occluded umbilicus.
U. lenticularis Vu Khuc, 1984 from the Bac
Thuy Formationis is very similar to the described specimens and probably should besynonymized with U. kwangsiana.
Occurrence: Described specimens fromBT01-09 and BT02-02 within the portion of
the Novispathodus ex gr. waageni Zone that
includes the Urdyceras tulongensis beds
(lower Middle Smithian = middle Lower Olenekian) in the Bac Thuy Formation, northeastern Vietnam. This species also occurs in the
Middle Smithian (Owenites koeneni beds) inSouth China (Brayard and Bucher, 2008).
Genus Parussuria Spath, 1930
Type species: Ussuria compressa Hyattand Smith, 1905.
Parussuria compressa(Hyatt and Smith, 1905)
Figs. 81, 82
Ussuria compressa Hyatt and Smith, 1905, p. 89, pl. 3,
figs. 6–11.
Sturia compressa (Hyatt and Smith, 1905). Smith, 1932,
p. 93, pl. 3, figs. 6–11.
Parussuria compressa (Hyatt and Smith, 1905). Spath,
1934, fig. 66c–d; Kummel and Steele, 1962, p. 690,
pl. 99, fig. 23, pl. 102, fig. 11; Shevyrev, 1995, p. 37,
pl. 4, fig. 6, text-fig. 16; Brayard and Bucher, 2008,
p. 56, pl. 12, fig. 17; Brühwiler et al., 2012a, p. 31,
pl. 18, figs. 8–14; Brayard et al., 2013, p. 191, fig.
57a–f.
Metussuria spathi Chao, 1959, p. 261, pl. 21, fig. 3, pl. 31,
fig. 13.
Parussuria semenovi Zakharov, 1968, p. 59, pl. 5, fig. 4,
text-fig. 8e.

Holotype: USNM 75250, figured by Hyattand Smith (1905, p. 89, pl. 3, figs. 6–7), from
the Meekoceras beds (middle Smithian) in the
Inyo Range, California, western USA.
Material examined: One specimen, NMNSOlenekian (Early Triassic) in northeastern Vietnam

113

Fig. 80. Ussuria kwangsiana Chao, 1959. 1–3, NMNS PM23526, from BT02–02. 4–8, NMNS PM23527, fromBT01-09.

PM23528, from BT02-03 and four specimens,
NMNS PM23529–23532, from KC01-13.
Description: Very involute, very compressed oxycone with very narrowly rounded
venter and gently convex flanks with maximum width near umbilicus. Flanks graduallyconvergent to venter. Umbilicus occluded withlow, oblique wall and rounded shoulders. Shellsurface smooth. Suture subammonitic, withdeeply divided, phylloid saddles and strongly

indented lobes.
Measurements (mm):Specimen no.
NMNS PM23529
NMNS PM23530
NMNS PM23531
NMNS PM23528
NMNS PM23532

D
40.6
44.6
—
72.4
—

U
0.0
0.0
0.0
0.0
0.0

H
27.1
29.0
35.3
50.0
55.4

W
11.6
13.2
15.0
18.0
18.9

W/H
0.43
0.46
0.42
0.36
0.34

Discussion: Metussuria spathi Chao, 1959
from South China has a subammonitic suture

114

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 81. Parussuria compressa (Hyatt and Smith, 1905) from KC01-13. 1–4, NMNS PM23530. 5–8, NMNS
PM23531. 9–10, NMNS PM23532.

Olenekian (Early Triassic) in northeastern Vietnam

115

Fig. 82. Parussuria compressa (Hyatt and Smith, 1905). 1–4, NMNS PM23528, from BT02-03. 5–9, NMNS
PM23529, from KC01-12.

116

Shigeta, Komatsu, Maekawa and Dang (eds.)

line with deeply divided, phylloid saddles andstrongly indented lobes. This evidence clearlysuggests that this species should be assigned
to Parussuria. Furthermore, its shell morphology does not exhibit any significant differences from Parussuria compressa and is hereinconsidered as a synonym. P. semenovi Zakharov, 1968 from South Primorye, whose sutureline and shell morphology is very similar, isalso probably conspecific with P. compressa.
Occurrence: Described specimens fromBT02-03 and KC01-13 within the portion of
the Novispathodus ex gr. waageni Zone that
includes the Leyeceras horizon of theOwenites koeneni beds (middle Middle Smithian = middle Lower Olenekian) in the Bac
Thuy Formation, northeastern Vietnam. This
species also occurs in the Middle Smithian inSouth China (Owenites koeneni beds, Brayard
and Bucher, 2008), Oman (Owenites koeneni
fauna, Brühwiler et al., 2012a), northwestern
Caucasus(Owenites-Dieneroceras
beds,
Shevyrev, 1995), western USA (Meekoceras
gracilitatis Zone, Kummel and Steele, 1962;
Owenites beds, Brayard et al., 2013) andSouth Primorye (Owenites koeneni Zone,
Zakharov, 1968).
Family Melagathiceratidae Tozer, 1971
Genus Jinyaceras Brayard and Bucher, 2008
Type species: Jinyaceras bellum Brayard
and Bucher, 2008.
Jinyaceras cf. bellum
Brayard and Bucher, 2008
Fig. 83.1–83.15
cf. Jinyaceras bellum Brayard and Bucher, 2008, p. 31, pl.
9, figs. 1–19, text-figs. 29.

Material examined: Two specimens,
NMNS PM23539–23540, from BT01-03, one
specimen, NMNS PM23541, from BT01-09,
one specimen, NMNS PM23542, from BT0202, and one specimen, NMNS PM23543, froma float limestone block at BT02.
Description: Moderately involute, fairly

depressed shell with broadly arched venter,rounded ventral shoulders, and slightly convex
flanks gradually converging from umbilicalshoulders to venter. Umbilicus fairly narrow
with moderately high, nearly vertical wall androunded shoulders. Ornamentation consists of
distant, prorsiradiate constrictions that become
weaker on venter. Suture not well preserved.
Measurements (mm):Specimen no.
NMNS PM23542
NMNS PM23543
NMNS PM23541
NMNS PM23539
NMNS PM23540

D
14.4
14.6
14.7
14.7
19.8

U
3.4
4.5
3.9
4.2
4.8

H
6.0
5.7
6.4
5.7
5.5

W
8.3
6.6
6.6
7.1
6.8

U/D
0.24
0.31
0.27
0.29
0.24

W/H
1.38
1.16
1.03
1.25
1.23

Discussion: The described specimens arevery similar to Jinyaceras bellum from South
China, but their poor preservation prevents a
definitive species assignment. Chao (1959) attributed two new species to Kashmirites Diener, 1913, K. prorsiradiatus and K. varians,
and also described two specimens as K. subar­
matus Diener, 1913, all of which are very
close to J. bellum. They may be conspecific,
but further taxonomic studies are necessary toconfirm the synonymy.
Occurrence: Described specimens fromBT01-03, BT01-09 and BT02-02 within the
portion of the Novispathodus ex gr. waageni
Zone that includes the Flemingites rursiradia­
tus beds (lowest Middle Smithian = middle
Lower Olenekian) and Urdyceras tulongensis
beds (lower Middle Smithian = middle Lower
Olenekian) in the Bac Thuy Formation, northeastern Vietnam. Jinyaceras bellum occurs in
the Middle Smithian in South China (Fleming­
ites rursiradiatus beds and Owenites koeneni
beds, Brayard and Bucher, 2008).
Jinyaceras? sp. indet.
Fig. 83.16–83.19

Material examined: One specimen, NMNS
PM23544, from BT02-02 and one specimen,
NMNS PM23545, from BT01-09.
Description: Moderately involute shellwith equal whorl height and width. Venter

Olenekian (Early Triassic) in northeastern Vietnam

117

Fig. 83. 1–15, Jinyaceras cf. bellum Brayard and Bucher, 2008. 1–3, NMNS PM23539, from BT01-03. 4–6,
NMNS PM23540, from BT01-03. 7–8, NMNS PM23541, from BT01-09. 9–11, NMNS PM23542, fromBT02-02. 12–15, NMNS PM23543, from a float limestone block at BT02. 16–19, Jinyaceras? sp. indet. 16–
17, NMNS PM23544, from BT02-02. 18–19, NMNS PM23545, from BT01-09.

118

Shigeta, Komatsu, Maekawa and Dang (eds.)

broadly arched with rounded shoulders andslightly convex flanks with maximum whorl
width near umbilicus. Umbilicus fairly narrow
with moderately high, nearly vertical wall androunded shoulders. Ornamentation consists of
distant, prorsiradiate constrictions. Suture notwell preserved.
Measurements (mm):Specimen no.
DUH
W U/D W/H
NMNS PM23545 31.8 7.0 14.2 14.5 0.22 1.02
NMNS PM23544 46.0 10.5 20.0 18.0 0.23 0.90

Discussion: The assignment of the described specimens to Jinyaceras is uncertain
and is based only on the similarity of theirmorphology with Jinyaceras. However, these
specimens are larger than specimens assigned
to Jinyaceras by previous authors (Brayard
and Bucher, 2008; Brühwiler et al., 2010,2012a, 2012c).
Occurrence: Described specimens fromBT01-09 and BT02-02 within the portion of
the Novispathodus ex gr. waageni Zone that
includes the Urdyceras tulongensis beds
(lower Middle Smithian = middle Lower Olenekian) in the Bac Thuy Formation, northeastern Vietnam.
Genus Juvenites Smith, 1927
Type species: Juvenites kraffti Smith,
1927.
Juvenites sinuosus (Kiparisova, 1947)
Fig. 84
Nannites sinuosus Kiparisova, 1947, p. 141, pl. 27, figs.
7–8.
Nannites sinuosus var. pressula Kiparisova, 1947, p.141,
pl. 27, fig. 6, text-fig. 27.
Juvenites kwangsianus Chao, 1959, p. 287, pl. 26, figs.
6–8.
Juvenites medius (Diener, 1909). Chao, 1959, p. 288, pl.
25, figs. 11–20.
Juvenites septentrionalis Smith, 1932. Chao, 1959, p. 289,
pl. 25, figs. 6–10.
Juvenites orientalis Chao, 1959, p. 290, pl. 26, figs. 3–5.
Juvenites sp. A. Chao, 1959, p. 290, pl. 25, figs. 21–22.
Juvenites sp. B. Chao, 1959, p. 291, pl. 25, figs. 23–27.
Anasibirites simplex Chao, 1959, p. 327, pl. 40, figs. 7–9.

Juvenites sp. Kummel and Sakagami, 1960, p. 8, pl. 1, fig.
2.
Nannites cf. septentrionalis (Smith, 1932). Kiparisova,
1961, p. 132, pl. 27, fig. 13.
Nannites aff. sinuosus Kiparisova, 1947. Kiparisova,
1961, p. 133, pl. 27, fig. 12, text-fig. 100.
Nannites simplex (Chao, 1959). Zakharov, 1968, p. 117,
pl. 22, figs. 3–7.
Juvenites sinuosus (Kiparisova, 1947). Shevyrev, 1995, p.
23, pl. 1, fig. 1–2.
Juvenites procurvus Brayard and Bucher, 2008, p. 32, pl.
22, figs. 6–12, text-figs. 30; Brühwiler et al., 2012a,
p. 41, pl. 22, figs. 10–11; Brühwiler et al., 2012c, p.
163, fig. 37AK–AP.
Juvenites cf. thermarum (Smith, 1927). Brühwiler et al.,2012a, p. 39, pl. 22, figs. 1–9.
Juvenites sp. Brühwiler et al., 2012b, p. 105, fig. 89AN–
AX.

Holotype: CGM 43/6259, figured by Kiparisova (1947, p. 141, pl. 27, fig. 8), from the
middle Smithian (Owenites-Dienerocerasbeds) in northwestern Caucasus.
Material examined: One specimen, NMNS
PM23533, from KC01-03 and five specimens,
NMNS PM23534–23538, from KC01-13.
Description: Fairly involute, very depressed shell with semicircular whorl section
and convex flanks gradually converging from
abruptly rounded umbilical shoulders toarched venter. Umbilicus moderately widewith moderately high, nearly vertical wall andabruptly rounded shoulders. Ornamentationconsists of distant, forward projected constrictions, becoming denser on mature body chamber. Suture not well preserved.
Measurements (mm):Specimen no.
NMNS PM23538
NMNS PM23535
NMNS PM23537
NMNS PM23536
NMNS PM23533
NMNS PM23534

D
12.8
16.0
17.0
17.7
18.2
18.8

U
4.1
4.9
5.2
5.7
6.2
6.4

H
4.8
6.5
6.6
6.4
6.3
7.0

W
8.4
11.3
10.5
9.5
10.3
10.4

U/D
0.32
0.31
0.31
0.32
0.34
0.34

W/H
1.75
1.73
1.59
1.48
1.63
1.49

Discussion: Countless specimens referable
to the genus Juvenites are known not only
from eastern Panthalassa (western USA), butalso from the Tethys (northwestern Caucasus,
Oman, Spiti, the Salt Range, South China) andOlenekian (Early Triassic) in northeastern Vietnam

119

Fig. 84. Juvenites sinuosus (Kiparisova, 1947). 1–4, NMNS PM23533, from KC01-03. 5–8, NMNS PM23534,
from KC01-13. 9–12, NMNS PM23536, from KC01-13. 13–14, NMNS PM23535, from KC01-13. 15–16,
NMNS PM23537, from KC01-13. 17–20, NMNS PM23538, from KC01-13.

120

Shigeta, Komatsu, Maekawa and Dang (eds.)

western Panthalassa (South Primorye). Manydifferent species have been erected based only
on slight differences in shell shape and sutureline, but the intraspecific variation of each species is not yet that well understood.
Brayard and Bucher (2008) recently erected Juvenites procurvus based on seven specimens from South China ranging from juvenile
to mature stages. Some of these specimens arevery similar to other species previously described from the Tethys and western Panthalassa. For example, PIMUZ 26010 (Brayard
and Bucher, 2008, pl. 22, fig. 8, holotype) is
quite similar to the holotype of J. sinuosus(Kiparisova, 1947, pl. 27, fig. 8), and PIMUZ
26009 (Brayard and Bucher, 2008, pl. 22, fig.
7) is very close to holotype of J. kwangsianus(Chao, 1959, pl. 26, figs. 6–7). In addition,
PIMUZ 26012 (Brayard and Bucher, 2008, pl.
22, fig. 10) is similar to holotype of J. orienta­lis (Chao, 1959, pl. 26, figs. 3–4). These very
close similarities strongly suggest that the previously described species from the Tethys andwestern Panthalassa synonymized above probably fall within the intraspecific or ontogenetic
variation J. sinuosus.
Occurrence: Described specimens from
KC01-03 and KC01-13 within the portion of
the Novispathodus ex gr. waageni Zone that
includes the Leyeceras horizon of theOwenites koeneni beds (middle Middle Smithian = middle Lower Olenekian) in the Bac
Thuy Formation, northeastern Vietnam. This
species also occurs in the Middle Smithian inSouth China (Owenites koeneni beds, Brayard
and Bucher, 2008), Spiti (Pseudoceltites multi­
plicatus beds, Brühwiler et al., 2012c), theSalt Range (Brayardites compressus beds,
Brühwiler et al., 2012b), Oman (Owenites
koeneni fauna, Brühwiler et al., 2012a), northwestern Caucasus (Owenites-Dieneroceras
beds, Shevyrev, 1995), and South Primorye(Owenites koeneni Zone, Zakharov, 1968).

Genus Paranannites Hyatt and Smith, 1905
Type species: Paranannites aspenensis
Hyatt and Smith, 1905.
Paranannites sinensis (Chao, 1959)
Figs. 85–87
Prosphingites sinensis Chao, 1959, p. 297, pl. 25, figs.
1–5, pl. 27, figs. 1–17, text-fig. 40a–c.
Paranannites spathi (Frebold, 1930). Brayard and Bucher,
2008, p. 63, pl. 35, figs. 10–19, text-fig. 55.
Juvenites cf. spathi (Frebold, 1930). Brühwiler et al.
(2012c), p. 161, pl. 37A–O.

Lectotype: Specimen NIGP 12587, figured
by Chao (1959, p. 297, pl. 27, figs. 16–17)
from the Owenitan (middle Smithian) in the
Tientung district (Kaoyunling), western
Guangxi, South China, here designated.
Material examined: Three specimens,
NMNS PM23564–23566, from KC01-07, one
specimen, NMNS PM23567, from KC01-10,
seven specimens, NMNS PM23568–23574,
from BT02-02, and three specimens, NMNS
PM23561–23563, from a float limestone blockat BT02.
Description: Fairly involute, fairly depressed shell characterized by subtrigonal
whorl section with narrowly rounded to subangular venter and convex flanks gradually converging from umbilical shoulders to venter.
Maximum whorl width occurs on umbilicalshoulders. Umbilicus fairly narrow with high,vertical wall and abruptly rounded shoulders.
Ornamentation consists of variable strength,
prorsiradiate constrictions. Suture not wellpreserved.
Measurements (mm):Specimen no.
NMNS PM23565
NMNS PM23567
NMNS PM23563
NMNS PM23569
NMNS PM23570
NMNS PM23561
NMNS PM23571
NMNS PM23562
NMNS PM23573

DU
19.6 5.2
26.0 5.7
30.0 5.6
32.0 6.1
33.8 5.5
38.7 7.4
38.7 8.4
40.3 8.842.0 10.1

H
7.8
10.5
13.4
15.0
15.7
18.9
16.0
15.0
18.5

W
11.6
—
18.4
18.0
18.0
24.1
23.5
19.5
27.0

U/D
0.27
0.21
0.19
0.19
0.16
0.19
0.22
0.22
0.24

W/H
1.48
—
1.37
1.20
1.15
1.28
1.47
1.30
1.46

Olenekian (Early Triassic) in northeastern Vietnam

121

Fig. 85. Paranannites sinensis (Chao, 1959) from BT02-02. 1–2, NMNS PM23571. 3–4, NMNS PM23572. 5–7,
NMNS PM23573. 8–10, NMNS PM23574.

122

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 86. Paranannites sinensis (Chao, 1959) from a float limestone block at BT02. 1–4, NMNS PM23561. 5–8,
NMNS PM23562. 9–12, NMNS PM23563.

Olenekian (Early Triassic) in northeastern Vietnam

123

Fig. 87. Paranannites sinensis (Chao, 1959). 1–2, NMNS PM23564, from KC01-07. 3–4, NMNS PM23565,
from KC01-07. 5–6, NMNS PM23566, from KC01-07. 7–8, NMNS PM23567, from KC01-10. 9–10, NMNS
PM23568, from BT02-02. 11–14, NMNS PM23569, from BT02-02. 15–18, NMNS PM23570, from BT02-02.

124

Shigeta, Komatsu, Maekawa and Dang (eds.)

NMNS PM23572 47.3 9.3 22.5 — 0.20 —NMNS PM23574 51.0 13.1 18.5 27.6 0.26 1.49

Discussion: Paranannites sinensis is very
close to P. spathi (Frebold, 1930) from the
Spathian (Upper Olenekian) of Spitsbergen,but differs by its variable strength constrictions. In contrast, P. spathi is ornamented with
distant, fine ribs. Specimens described as P.
spathi from Arctic Canada by Tozer (1961,
1994) and South Tibet by Brühwiler et al.
(2010) are somewhat similar to P. sinensis, but
their venters are more rounded. The same observation holds true for specimens from Spiti
attributed to Juvenites cf. spathi by Brühwiler
et al. (2012c).
Occurrence: Described specimens fromBT02-02, KC01-07 and KC01-10 within the
portion of the Novispathodus ex gr. waageni
Zone that includes the Urdyceras tulongensis
beds (lower Middle Smithian = middle Lower
Olenekian) and the Leyeceras horizon of
Owenites koeneni beds (middle Middle Smithian = middle Lower Olenekian) in the Bac
Thuy Formation, northeastern Vietnam. This
species also occurs in the Middle Smithian(Owenites koeneni beds) in South China (Brayard and Bucher, 2008).
Paranannites involutus (Chao, 1959)
Fig. 88.1–88.4
Prosphingites involutus Chao, 1959, p. 297, pl. 28, figs.
1–11, text-fig. 39c.
“Paranannites” ovum Brayard and Bucher, 2008, p. 65, pl.
34, figs. 4–5.

Holotype: NIGP 12575, figured by Chao
(1959, p. 297, pl. 28, fig. 1–2), from theOwenitian (middle Smithian) in the Tientung
district (Tsoteng), western Guangxi, South
China.
Material examined: two specimens,
NMNS PM2357–23578, from a float limestone block at PK01.
Description: Involute, very depressed shellwith broadly rounded venter and convex
flanks gradually converging from umbilicalshoulders to venter. Maximum whorl width
occurs on umbilical shoulders. Umbilicus fairly narrow with high, vertical wall and abruptly
rounded shoulders. Shell surface smooth. Suture not well preserved.
Measurements (mm):Specimen no.
D
NMNS PM23578 29.6
NMNS PM23577 36.5

U
6.8
6.2

H
W U/D W/H
11.4 23.0 0.23 2.02
16.3 29.5 0.17 1.81

Discussion: Two specimens (PIMUZ
26090, 26091) described as “Paranannites”
ovum by Brayard and Bucher (2008, pl. 34,
figs. 4–5), which are characterized by a moredepressed shell than the type specimens, arevery similar to P. involutus and are probably
conspecific.
Occurrence: Described specimens from
PK01 within the portion of the Novispathodus
ex gr. waageni Zone that includes theOwenites koeneni beds (middle to upper Middle Smithian = middle Lower Olenekian) in the
Bac Thuy Formation, northeastern Vietnam.
This species also occurs in the middle Smithian (Owenitian) in South China (Chao, 1959).
Paranannites sp. indet.
Fig. 88.5–88.12

Material examined: One specimen, NMNS
PM23772, from BT01-09, one specimen,
NMNS PM23575, from BT01-11, and one
specimen, NMNS PM23576, from a float
limestone block at BT02.
Description: Very involute, fairly compressed shell characterized by a subelliptical
whorl section with rounded venter and convex
flanks gradually converging from umbilicalshoulders to venter. Maximum whorl width
occurs near umbilical shoulders. Umbilicus
narrow with moderately high, vertical wall
and abruptly rounded shoulders. Ornamentation consists of weak, forward projected constrictions. Suture not well preserved.
Measurements (mm):Specimen no.
D
NMNS PM23772 27.0

U
3.8

H
W U/D W/H
13.7 13.3 0.14 0.97

Olenekian (Early Triassic) in northeastern Vietnam

125

Fig. 88. 1–4, Paranannites involutus (Chao, 1959) from PK01. 1–2, NMNS PM23577. 3–4, NMNS PM23578.
5–12, Paranannites sp. indet. 5–6, NMNS PM23772, from BT01-09. 7–9, NMNS PM23575, from BT01-11.
10–12, NMNS PM23576, from a float limestone block at BT02.

126

Shigeta, Komatsu, Maekawa and Dang (eds.)

NMNS PM23575 37.9
NMNS PM23576 47.5

4.2
7.4

19.0 16.4 0.11 0.86
21.7 19.6 0.16 0.90

Discussion: The described specimens are
somewhat similar to Paranannites aspenensis
Hyatt and Smith (1905, p. 81) from western
USA in that they exhibit a fairly compressedshell with a narrow umbilicus, but the numberof available specimens is insufficient to makea definitive species assignment.
Occurrence: Described specimens fromBT01-09 and BT01-11 within the portion of
the Novispathodus ex gr. waageni Zone that
includes the Urdyceras tulongensis beds
(lower Middle Smithian = middle Lower Olenekian) in the Bac Thuy Formation, northeastern Vietnam.
Genus Owenites Hyatt and Smith, 1905
Type species: Owenites koeneni Hyatt andSmith, 1905.
Owenites koeneni Hyatt and Smith, 1905
Figs. 89–96
Owenites koeneni Hyatt and Smith, 1905, p. 83, pl. 10,
figs. 1–22; Smith, 1932, p. 100, pl. 10, figs. 1–22;
Spath, 1934, p. 185, text-fig. 57a–c; Kummel andSteele, 1962, p. 674, pl. 101, figs. 3–7, text-figs.
9–10; Popov, 1962, p. 44, pl. 6, fig. 6; Kuenzi, 1965,
p. 374, pl. 53, figs. 1–6, text-figs. 3d, 6; Hada, 1966,
pl. 4, figs. 2–4; Kummel and Erben, 1968, p. 121, pl.
19, figs. 10–15; Zakharov, 1968, p. 94, pl. 18, figs.
1–3, text-figs. 21, 24a–c; Collignon, 1973, p. 139, pl.
4, figs. 2–3; Bando, 1981, p. 158, pl. 17, fig. 7;
Shevyrev, 1990, p. 118, pl. 1, fig. 5; Shevyrev, 1995,
p. 51, pl. 5, figs. 1–3; Brayard and Bucher, 2008, p.
67, pl. 36, figs. 1–8, text-fig. 58; Brühwiler et al.,2010, p. 426, fig. 15.9; Brühwiler et al., 2012a, p. 43,
pl. 25, figs. 1–6; Brühwiler et al., 2012c, p. 155, fig.
35AH–AJ; Brayard et al., 2013, p. 204, fig. 74a–i.
Owenites egrediens Welter, 1922, p. 151, pl. 168, figs. 22–
26, text-figs. 14–18; Smith, 1932, p. 100, pl. 52, figs.
6–8; Spath, 1934, p. 186, text-figs. 56, 57d–f.
Owenites zitteli Smith, 1932, p. 101, pl.52, figs. 1–5.
Owenites aff. egrediens Welter, 1922. Kiparisova, 1947, p.
139, pl. 32, figs. 1–3.
Kingites shimizui Sakagami, 1955, p. 138, pl. 2, fig. 2.
Owenites pakungensis Chao, 1959, p. 248, pl. 21, figs.
6–8, text-fig. 26a.

Owenites pakungensis var. compressus Chao, 1959, p.
248, pl. 21, figs. 4–5.
Owenites costatus Chao, 1959, p. 249, pl. 22, figs. 10–18,
22–23, text-fig. 26c.
Owenites costatus var. lenticuluris Chao, 1959, p. 249, pl.
22, figs. 7–9, text-fig. 26d.
Pseudowenites oxynotus Chao, 1959, p. 252, pl. 23, figs.
1–16, text-fig. 27a–d; Vu Khuc, 1984, p. 82, pl. 7,
figs. 3–4; Vu Khuc, 1991, p. 142, pl. 52, figs. 4–5.
Owenites shimizui (Sakagami, 1955). Kummel and Sakagami, 1960, p. 6, pl. 5, figs. 5–6.
Owenites cf. koeneni Hyatt and Smith, 1905. Kummel,
1959, p. 441, figs. 2–4.
Owenites carinatus Shevyrev, 1968, p. 189, pl. 16, fig. 1;
Vu Khuc, 1984, p. 81, pl. 6, figs. 1–4, text-fig. 16; Vu
Khuc, 1991, p. 142, pl. 52, figs. 2–3, pl. 53, figs. 1–2,
text-fig. 4.4.
? Owenites cf. koeneni Hyatt and Smith, 1905. Nichols
and Silberling, 1979, pl. 1, figs. 17–18.

Holotype: USNM 75261, figured by Hyattand Smith (1905, p. 83, pl. 10, figs. 1–4), from
the Meekoceras beds (middle Smithian) in
Inyo Range, California, western USA.
Material examined: One specimen, NMNS
PM23579, from KC01-07, two specimens,
NMNS PM23580–23581, from KC01-10, two
specimens, NMNS PM23582–23583, from
KC01-11, one specimen, twenty one specimens, NMNS PM23603–23623 from KC0113, NMNS PM23584, from KC02-02, fivespecimens, NMNS PM23589–23593, fromBT01-14, nine specimens, NMNS PM23594–
23602, from BT02-03, one specimen, NMNS
PM23584, from BT02-04, one specimen,
NMNS PM23586, from a float limestone
block at BT03, one specimen, NMNS
PM23587, from PK01-01, and one specimen,
NMNS PM23588, from PK01-02.
Description: During earlier growth stages,
very involute, fairly compressed shell characterized by lenticular whorl section with angular venter and convex flanks gradually converging from umbilical shoulders to venter.
Maximum whorl width occurs near umbilicalshoulders. Umbilicus very narrow with moderately high, oblique wall and rounded shoulders. Ornamentation consists of weak, forward
projected folds. As growth proceeds, whorl

Olenekian (Early Triassic) in northeastern Vietnam

127

Fig. 89. Owenites koeneni Hyatt and Smith, 1905. 1–2, NMNS PM23579, from KC01-07. 3–4, NMNS
PM23580, from KC01-10. 5–6, NMNS PM23581, from KC01-10. 7–9, NMNS PM23582, from KC01-11.
10–11, NMNS PM23583, from KC01-13. 12–14, NMNS PM23584, from KC02-02. 15–16, NMNS
PM23585, from BT02-04. 17–18, NMNS PM23586, from BT03. 19–20, NMNS PM23587, from PK01-01.
21–22, NMNS PM23588, from PK01-02.

128

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 90. Owenites koeneni Hyatt and Smith, 1905, from KC01-13. 1–2, NMNS PM23603. 3–4, NMNS
PM23604. 5–7, NMNS PM23605. 8–10, NMNS PM23606. 11–12, NMNS PM23607. 13–15, NMNS
PM23608. 16–19, NMNS PM23609. 20–21, NMNS PM23610. 22–23, NMNS PM23611. 24–25, NMNS
PM23612.

Olenekian (Early Triassic) in northeastern Vietnam

129

Fig. 91. Owenites koeneni Hyatt and Smith, 1905, from KC01-13. 1–2, NMNS PM23613. 3–5, NMNS
PM23614. 6–7, NMNS PM23615. 8–9, NMNS PM23616. 10–11, NMNS PM23617. 12–15, NMNS
PM23618.

130

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 92. Owenites koeneni Hyatt and Smith, 1905, from KC01-13. 1–4, NMNS PM23619. 5–6, NMNS
PM23620. 7–8, NMNS PM23621. 9–10, NMNS PM23622. 11–13, NMNS PM23623.

Olenekian (Early Triassic) in northeastern Vietnam

131

Fig. 93. Owenites koeneni Hyatt and Smith, 1905, from BT01-14. 1–3, NMNS PM23589. 4–6, NMNS
PM23590. 7–10, NMNS PM23591. 11–12, NMNS PM23592. 13–14, NMNS PM23593.

132

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 94. Owenites koeneni Hyatt and Smith, 1905, from BT02-03. 1–2, NMNS PM23594. 3–4, NMNS
PM23595. 5–6, NMNS PM23596. 7–8, NMNS PM23597. 9–10, NMNS PM23598. 11–12, NMNS PM23599.

Olenekian (Early Triassic) in northeastern Vietnam

133

Fig. 95. Owenites koeneni Hyatt and Smith, 1905, from BT02-03. 1–4, NMNS PM23600. 5–8, NMNS
PM23601. 9–12, NMNS PM23602.

134

Shigeta, Komatsu, Maekawa and Dang (eds.)

Olenekian (Early Triassic) in northeastern Vietnam

section tends to become more compressed,
and umbilical width becomes wider. Suture
not well preserved.
Measurements (mm):Specimen no.
NMNS PM23584
NMNS PM23603
NMNS PM23605
NMNS PM23604
NMNS PM23609
NMNS PM23583
NMNS PM23582
NMNS PM23607
NMNS PM23613
NMNS PM23610
NMNS PM23580
NMNS PM23581
NMNS PM23588
NMNS PM23615
NMNS PM23585
NMNS PM23589
NMNS PM23587
NMNS PM23616
NMNS PM23593
NMNS PM23607
NMNS PM23592
NMNS PM23590
NMNS PM23606
NMNS PM23595
NMNS PM23614
NMNS PM23598
NMNS PM23623
NMNS PM23611
NMNS PM23621
NMNS PM23622
NMNS PM23596
NMNS PM23599
NMNS PM23619
NMNS PM23620
NMNS PM23612
NMNS PM23602
扌

D
14.2
14.3
19.9
21.6
23.0
24.0
24.5
31.0
31.0
31.1
31.2
32.3
32.8
32.9
37.2
37.8
38.0
38.5
42.4
43.9
44.3
45.7
46.0
49.0
49.5
50.0
50.0
50.4
52.0
52.5
53.0
53.0
53.0
54.4
55.4
56.7

U
1.1
0.8
1.0
1.1
1.5
1.0
2.4
4.5
3.1
3.0
4.5
4.4
2.2
4.0
5.7
6.3
4.7
7.4
9.7
7.1
7.4
8.2
7.0
12.4
8.4
10.2
7.8
8.3
12.1
14.2
14.3
11.8
9.9
8.1
12.9
10.5

H
7.9
7.9
10.6
10.9
12.9
13.0
12.9
15.1
15.7
15.0
15.3
15.3
16.7
16.0
18.2
17.4
19.1
17.1
17.9
19.9
19.0
21.0
20.1
21.0
22.0
21.2
23.2
23.0
21.6
20.2
21.2
23.0
23.4
25.0
23.8
25.7

W
5.7
5.6
7.5
7.8
8.3
9.2
8.8
9.5
9.5
10.0
10.0
10.2
10.6
9.6
11.1
12.2
14.0
10.2
13.3
12.6
13.4
13.1
11.1
14.0
13.8
12.7
14.0
11.8
12.5
14.5
14.7
13.1
16.2
14.5
15.0
14.7

U/D
0.08
0.06
0.05
0.05
0.07
0.04
0.10
0.15
0.10
0.10
0.14
0.14
0.07
0.12
0.15
0.17
0.12
0.19
0.23
0.16
0.17
0.18
0.15
0.25
0.17
0.20
0.16
0.16
0.23
0.27
0.27
0.22
0.19
0.15
0.23
0.19

W/H
0.78
0.70
0.71
0.71
0.64
0.71
0.68
0.63
0.61
0.66
0.65
0.67
0.63
0.60
0.61
0.70
0.73
0.60
0.74
0.63
0.71
0.67
0.55
0.67
0.63
0.60
0.60
0.51
0.58
0.72
0.69
0.57
0.69
0.58
0.63
0.57

NMNS PM23600
NMNS PM23597
NMNS PM23601
NMNS PM23617
NMNS PM23586
NMNS PM23594
NMNS PM23618
NMNS PM23591

58.0
58.7
60.5
60.7
61.4
63.5
63.6
64.2

135
13.2
14.8
14.8
15.8
16.2
13.6
15.4
12.1

24.3
22.6
24.8
24.9
25.3
28.8
27.8
25.7

16.1
15.0
16.9
15.7
15.1
17.5
16.2
14.0

0.23
0.25
0.24
0.26
0.26
0.21
0.24
0.19

0.66
0.66
0.68
0.63
0.60
0.61
0.58
0.54

Discussion: Morphologically, the described specimens are highly variable and include shell forms ranging from fairly compressed to very compressed with an umbilicus
that varies from very narrow to fairly narrow.
Shell form ratios (U/D, W/H) of the holotypesof Owenites koeneni Hyatt and Smith, 1905,
Kingites shimizui Sakagami, 1955, O. pakun­
gensis Chao, 1959, O. pakungensis var. com­pressus Chao, 1959, O. costatus Chao, 1959,
O. costatus var. lenticuluris Chao, 1959, Pseu­
dowenites oxynotus Chao, 1959, and O. cari­
natus Shevyrev, 1968 for the most part are included within the variation of the described
specimens (Fig. 89). This evidence strongly
suggests that these type specimens merely represent the variants of a single species, andhence, they should be synonymized with O.
koeneni, the first described taxon of these various species.
The holotype of Owenites zitteli Smith,
1932 has a more compressed shell with a narrower umbilicus than these specimens, but according to Kummel and Steele (1962), it probably is a more compressed variant of O. koen­
eni. The lectotype of O. egrediens Welter,
1922 has a more depressed shell, but otherwise is very similar to O. koeneni. It probably
represents a more depressed variant of O.
koeneni. Similar depressed forms are known

Fig. 96. Scatter diagrams of umbilical diameter/shell diameter (U/D) versus shell diameter (D) and whorl width/
whorl height (W/H) versus shell diameter (D) for Owenites koeneni Hyatt and Smith, 1905 from the Bac Thuy
Formation, northeastern Vietnam (black circles) and ten selected type specimens referable to Owenites. Numbered squares correspond as follows. 1: Owenites koeneni (holotype), 2: O. egrediens Welter, 1922 (lectotype), 3: O. zitteli Smith, 1932 (holotype), 4: Kingites shimizui Sakagami, 1955 (holotype), 5: O. pakungensis
Chao, 1959 (holotype), 6: O. pakungensis var. compressus Chao, 1959 (holotype), 7: O. costatus Chao, 1959
(holotype), 8: O. costatus var. lenticuluris Chao, 1959 (holotype), 9: Pseudowenites oxynotus Chao, 1959 (holotype), 10: O. carinatus Shevyrev, 1968 (holotype). Most of the type specimen shell form ratios fit well within those of the specimens from the Bac Thuy Formation.

136

Shigeta, Komatsu, Maekawa and Dang (eds.)

from Tulong (Brühwiler et al., 2010) andOman (Brühwiler et al., 2012a) and they too,have been assigned to O. koeneni. Nichols andSilberling (1979) described a specimen as
Owenites cf. koeneni from South-central Alaska, but their generic assignment is questionable because its ventral view is not shown.
Occurrence: Described specimens from
KC01-07, KC01-10, KC01-11, KC01-13,
KC02-02, BT01-14, BT02-03, BT02-04,
BT03, PK01-01 and PK01-02 within the portion of the Novispathodus ex gr. waageni Zone
that includes the Leyeceras and Guodunites
horizons of the Owenites koeneni beds (middle
to upper Middle Smithian = middle Lower Olenekian) in the Bac Thuy Formation, northeastern Vietnam. This species also occurs in the
Middle Smithian in South China (Owenites
koeneni beds, Brayard and Bucher, 2008;
Chao, 1959), Malaya (Hada, 1966), Timor(Welter, 1922), South Tibet (Pseudoceltites
multiplicatus beds and Nyalamites anguste­
costatus beds, Brühwiler et al., 2010), Spiti(Nyalamites angustecostatus beds, Brühwiler
et al., 2012c), Kashmir (Owenites-Kashmirites
Zone, Bando, 1981), Afganistan (Kummel andErben, 1968; Collignon, 1973), Oman
(Owenites koeneni fauna, Brühwiler et al.,2012a), northwestern Caucasus (Shevyrev,
1968, 1990, 1995), New Zealand (Kummel,
1959), Japan (Kummel and Sakagami, 1960),
South Primorye (Owenites koeneni Zone,
Zakharov, 1968), and western USA (Meekoc­
eras gracilitatis Zone, Kummel and Steele,
1962, Kuenzi, 1965; Owenites beds, Brayard
et al., 2013).
Superfamily Sageceratoidea Hyatt, 1884
Family Aspenitidae Spath, 1934
Genus Aspenites Hyatt and Smith, 1905
Type species: Aspenites acutus Hyatt andSmith, 1905.

Aspenites acutus Hyatt and Smith, 1905
Fig. 97
Aspenites acutus Hyatt and Smith, 1905, p. 96, pl. 2, figs.
9–13, pl. 3, figs. 1–5; Smith, 1932, p. 86, pl. 2, figs.
9–13, pl. 3, figs. 1–5, pl. 30, figs. 1–26, pl. 60, figs.
4–6; Chao, 1959, p. 269, pl. 35, figs. 12–18, 23, textfigs. 34a; Kummel and Steele, 1962, p. 692, pl. 99,
figs. 16–17; Nichols and Silberling, 1979, pl. 1, figs.
12–14; Brayard and Bucher, 2008, p. 77, pl. 42, figs.
1–9, text-fig. 67; Brühwiler et al., 2010, p. 429, fig.
16.12, 16.13; Brühwiler et al., 2012a, p. 48, pl. 26,
figs. 1–2; Brühwiler et al., 2012c, p. 166, fig. 41A–
M; Brayard et al., 2013, p. 212, fig. 81a–j.
Aspenites laevis Welter, 1922, p. 99, pl. 155, figs. 4–5;
Smith, 1932, p. 86, pl. 28, figs. 28–33; Chao, 1959,
p. 270, pl. 35, figs. 9–11, text-fig. 34b.
Aspenites obtusus Smith, 1932, p. 86, pl. 31, figs. 8–10.
Hemiaspenites obtusus (Smith, 1932). Kummel andSteele, 1962, p. 666, pl. 99, fig. 18.
Aspenites cf. acutus Hyatt and Smith, 1905. Nichols andSilberling, 1979, pl. 1, figs. 15–16.

Holotype: USNM 75249, figured by Hyattand Smith (1905, p. 96, pl. 3, figs. 1–2), from
the Meekoceras beds (middle Smithian) in the
Inyo Range, California, western USA.
Material examined: One specimen, NMNS
PM23635, from BT01-09 and one specimen,
NMNS PM23636, from KC01-13.
Description: Very involute, very compressed oxycone with acutely keeled venterand slightly convex flanks with maximum
width at mid-flank. Umbilicus occluded. Shellsurface smooth or ornamented with radialfolds. Suture ceratitic with many adventitious
elements.
Measurements (mm):Specimen no.
D
NMNS PM23636 30.7
NMNS PM23635 48.8

U
0.0
0.0

H
18.8
30.0

W
5.6
—

U/D W/H
0.0 0.18
0.0—

Discussion: Aspenites laevis Welter, 1922
and A. obtusus Smith, 1932 were synonymized
with A. acutus by Brayard and Bucher (2008,
p. 77), and we agree with their interpretation.
Hedenstroemia acuta Kraft and Diner, 1909
from Spiti is somewhat similar to A. acutus,
but differs by its suture line, which has laterallobes with many denticulations at the base andwide lateral saddles.

Olenekian (Early Triassic) in northeastern Vietnam

137

Fig. 97. Aspenites acutus Hyatt and Smith, 1905. 1, NMNS PM23635, from BT01-09. 2–5, NMNS PM23636,
from KC01-13.

Occurrence: Described specimens fromBT01-09 and KC01-03 within the portion of
the Novispathodus ex gr. waageni Zone that
includes the Urdyceras tulongensis beds
(lower Middle Smithian = middle Lower Olenekian) and Leyeceras horizon of theOwenites koeneni beds (middle Middle Smithian = middle Lower Olenekian) in the Bac
Thuy Formation, northeastern Vietnam. This
species also occurs in the Middle Smithian inSouth China (Flemingites rursiradiatus beds
and Owenites koeneni beds, Brayard and Bucher, 2008), Timor (Welter, 1922), South Tibet(Brayardites compressus beds, Brühwiler etal., 2010), Spiti (Brayardites compressus beds,
Brühwiler et al., 2012c), Oman (Rohilites
omanensis fauna, Nammalites pilatoides
fauna, and Owenites koeneni fauna, Brühwiler
et al., 2012a), South-central Alaska (Nichols
and Silberling, 1979) and western USA(Meekoceras gracilitatis Zone, Kummel andSteele, 1962; Owenites beds, Brayard et al.,2013).
Family Hedenstroemiidae Hyatt, 1884
Genus Pseudosageceras Diener, 1895
Type species: Pseudosageceras sp. indet.
Diener, 1895.

Pseudosageceras multilobatum
Noetling, 1905aFigs. 98, 99
Pseudosageceras sp. indet. Diener, 1895, p. 28, pl. 1, fig.
8.
Pseudosageceras multilobatum Noetling, 1905a, p. 181,
pls. 19–27; Noetling, 1905b, pl. 23, fig. 4, pl. 25, fig.
1, pl. 26, fig. 3; Krafft and Diener, 1909, p. 145, pl.
21, fig. 5; Welter, 1922, p. 94, fig. 3; Smith, 1932, p.
87, pl. 4, figs. 1–3, pl. 5, figs. 1–6, pl. 25, figs. 7–16,
pl. 60, fig. 32, pl. 63, figs. 1–6; Collignon, 1933, p.
56, pl. 11, fig. 2; Spath, 1934, p. 54, text-fig. 6a; Kiparisova,1947, p. 127, pl. 25, figs. 3–4; Chao, 1959, p.
183, pl. 1, figs. 9, 12; Kummel, 1966, p. 388, pl. 1,
figs. 11–12; Hada, 1966, pl. 4, fig. 6; Kummel andErben, 1968, p. 112, pl. 19, fig. 9; Shevyrev, 1968, p.
79, pl. 1, figs. 1–2; Collignon, 1973, p. 5, pl. 1, fig. 1;
Weitschat and Lehmann, 1978, p. 75, pl. 10, fig. 2;
Vu Khuc, 1984, p. 26, pl. 1, fig. 1, text-fig. 1; Pakistani-Japanese Research Group, 1985, pl. 12, figs.
5–7; Vu Khuc, 1991, p. 119, pl. 45, figs. 5–6, text-fig.
2.2; Tozer, 1994, p. 83, pl. 18, fig. 1, text-fig. 17;
Brayard and Bucher, 2008, p. 70, pl. 37, figs. 1–5;
Shigeta and Zakharov, in Shigeta et al., 2009, p. 140,
figs. 129–130; Brühwiler et al., 2010, p. 429, fig.
16.14; Brühwiler et al., 2012a, p. 47, pl. 26, fig. 4;
Brühwiler et al., 2012c, p. 109, fig. 95A–N; Brayard
et al., 2013, p. 208, fig. 77a–f.
non Pseudosageceras multilobatum Noetling, 1905a.
Kummel and Steele, 1962, p. 701, pl. 102, figs. 1–2.

Lectotype: Designated by Spath (1934, p.

138

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 98. Pseudosageceras multilobatum Noetling, 1905, from BT02-02. 1–2, NMNS PM23638.

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 99.

139

Pseudosageceras multilobatum Noetling, 1905, from BT01-14. 1–3, NMNS PM23637.

54), is original of Noetling (1905a, p. 181, pl.
19, fig. 1, pl. 24, fig. 12) from the Ceratite
Marls of the Salt Range, Pakistan.
Material examined: One specimen, NMNS
PM23637, from BT01-14 and one specimen,
NMNS PM23638, from BT02-02.
Description: Very involute, very compressed oxycone with very narrow, bicarinate
venter and weakly convex flanks, gently convergent from occluded umbilicus to venter.
Shell surface smooth. Suture ceratitic withmany adventitious elements.
Discussion: The specimen described as
Pseudosageceras multilobatum by Kummel
and Steele (1962, pl. 102, figs. 1–2) from Ne-

vada is characterized by an acutely keeled
venter and wider lobes and saddles than Pseu­
dosageceras. It probably should be assigned to
Aspenites. As earlier reported by Shigeta andZakharov (in Shigeta et al., 2009), the specimen described as Pseudosageceras sp. by Diener (1895) from South Primorye is only a partial phragmocone, but it displays the sameshell shape and suture as P. multilobatum, andthus, is probably conspecific.
Occurrence: Described specimens fromBT02-02 and BT01-14 within the portion of
the Novispathodus ex gr. waageni Zone that
includes the Urdyceras tulongensis beds
(lower Middle Smithian = middle Lower Ole-

140

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 100. Pseudosageceras sp. indet. 1–6, from KC02-11. 1–2, NMNS PM23648. 3, NMNS PM23649 (rubber
cast of outer mold). 4–5, NMNS PM23650. 6, NMNS PM23651. 7, NMNS PM23760, from KC02-13. 8,
NMNS PM23652 (rubber cast of outer mold), from KC02-15.

nekian) and the Leyeceras horizon of theOwenites koeneni beds (middle Middle Smithian = middle Lower Olenekian) in the Bac
Thuy Formation, northeastern Vietnam. Thistaxon, which is probably the most cosmopolitan species of the Early Triassic, occurs in theSmithian in South China (Chao, 1959; Brayard and Bucher, 2008), Malaya (Hada, 1966),
Timor (Welter, 1922), South Tibet (Brühwiler
et al., 2010), Spiti (Krafft and Diener, 1909),
Afganistan (Kummel and Erben, 1968; Collignon, 1973), Salt Range (Kummel, 1966;
Brühwiler et al., 2012b), Madagascar (Collignon, 1933), Oman (Brühwiler et al., 2012a),northwestern Caucasus (Shevyrev, 1968),
South Primorye (Kiparisova, 1961), western
USA (Hyatt and Smith, 1905, Smith, 1932,
Brayard et al., 2013), Arctic Canada (Tozer,
1994) and Spitsbergen (Weitschat and Lehm-

ann, 1978).
Pseudosageceras sp. indet.
Fig. 100Material examined: Four specimens,
NMNS PM23648–23651, from KC02-11, one
specimen, NMNS PM23760, from KC02-13
and one specimen, NMNS PM23652, from
KC02-15.
Description: Very involute, very compressed shell with very narrow, bicarinate venter. Umbilicus occluded. Suture ceratitic withmany adventitious elements.
Discussion: The described specimens arevery similar to Pseudosageceras multilobatum
Noetling, 1905, but a definitive assignment in
not possible because of their poor preservation.

Olenekian (Early Triassic) in northeastern Vietnam

Occurrence: Described specimen from
KC02-11 within the portion of the Novispath­odus pingdingshanensis Zone represented by
the Tirolites cf. cassianus beds (lowest Lower
Spathian = lowest Upper Olenekian), thosefrom KC02-13 and KC02-15 within the portion of the Triassospathodus symmetricus
Zone represented by the Tirolites cf. cassianus
beds (lowest Lower Spathian = lowest Upper
Olenekian) and Tirolites sp. nov. beds (Lower
Spathian = lower Upper Olenekian) in the Bac
Thuy Formation, northeastern Vietnam.
Superfamily Dinaritoidea Mojsisovics, 1882
Family Tirolitidae Mojisisovics, 1882
Genus Tirolites Mojsisovics, 1879
Type species: Tirolites idrianus Hauer,
1865.
Tirolites cf. cassianus (Quenstedt, 1849)
Fig. 101
cf. Ceratites cassianus Quenstedt, 1849, p. 231, pl. 18, fig.
11.
cf. Tirolites spinosus Mojsisovics, 1882, p. 70, pl. 2, fig. 2.
cf. Tirolites darwini Mojsisovics, 1882. Kittl, 1903, p. 60,
pl. 11, figs. 1–2.
cf. Tirolites spinosior Kittl, 1903, p. 62, pl. 11, fig. 5.
cf. Tirolites toulai Kittl, 1903, p. 64, pl. 11, fig. 11.

Material examined: Four specimens,
NMNS PM23662–23665, from KC02-11, two
specimens, NMNS PM23762–23763, from
KC02-12, and two specimens, NMNS
PM23765–23766, from KC02-13.
Description: Very evolute, very compressed shell with arched venter, rounded ventral shoulders, and slightly convex flanks. Umbilicus fairly wide with moderately high, gently inclined wall. Ornamentation consists ofspiny tubercles on ventrolateral shoulders aswell as strong radial ribs on early to middle
growth stages. Ribs decrease in strength andbecome much finer, while ventrolateral tubercles exhibit attenuation in strength and finallydisappear on mature body chamber. Suture notpreserved.

141

Measurements (mm):Specimen no.
NMNS PM23662
NMNS PM23665
NMNS PM23663
NMNS PM23664

D
39.2
57.0
59.0
89.0

U
16.2
24.0
26.5
37.0

H
14.0
21.5
20.8
32.0

W
—
—
—
—

U/D W/H
0.41 —
0.42 —
0.43 —
0.42 —

Discussion: Even though the present specimens are significantly deformed and crushed,
their distinctive ornamentation and shell shapeenable me to identify them with reasonableconfidence as Tirolites cassianus. Specimen
NMNS PM23664 is very close to specimens
described as T. spinosus by Mojsisovics (1882,
pl. 2, fig. 2), T. darwini Mojsisovics, 1882 byKittl (1903, pl. 11, figs. 1–2), T. spinosior by
Kittl (1903, pl. 11, fig. 5), and T. toulai by
Kittl (1903, pl. 11, fig. 11). These species weresynonymized with T. cassianus by Kummel(1969).
Occurrence: Described specimens from
KC02-11 within the portion of the Novispath­odus pingdingshanensis Zone represented by
the Tirolites cf. cassianus beds (lowest Lower
Spathian = lowest Upper Olenekian), and thoseof KC02-12 and KC02-13 within the portionof the Triassospathodus symmetricus Zone
represented by the Tirolites cf. cassianus beds
(lowest Lower Spathian = lowest Upper Olenekian) in the Bac Thuy Formation, northeastern Vietnam. Tirolites cassianus occurs in thelowest Lower Spathian in the Alps (Werfen
Formation), Dalmatia and associated regions(Mojsisovics, 1882; Kittl, 1903; Krystyn,
1974; Posenato, 1992), and Mangyshlak(Shevyrev, 1968).
Tirolites sp. nov.
Figs. 102–113

Material examined: Seven specimens,
NMNS PM23666–23672, from KC02-14,
twenty specimens, NMNS PM23673–23690,
23768–23769, from KC02-15, two specimen,
NMNS PM23770–23771, from KC02-16, four
specimen, NMNS PM23695–23698, from
KC02-18, two specimens, NMNS PM23691–

142

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 101. Tirolites cf. cassianus (Quenstedt, 1849). 1–4, from KC02-11. 1, NMNS PM23662. 2, NMNS
PM23665 (rubber cast of outer mold). 3, NMNS PM23663. 4, NMNS PM23664. 5–6, from KC02-12. 5,
NMNS PM23762 (rubber cast of outer mold). 6, NMNS PN23763 (rubber cast of outer mold). 7–8, from
KC02-13. 7, NMNS PM23765. 8, NMNS PM23766.

Olenekian (Early Triassic) in northeastern Vietnam

143

Fig. 102. Tirolites sp. nov. 1–4, from NT01-10. 1, NMNS PM23764. 2, NMNS PM23693. 3–4, NMNS
PM23694 (rubber casts of outer molds).

23692, from BT02-06, and three specimens,
NMNS PM23693–23694, 23764, from NT0110.
Description: Fairly evolute, very compressed shell with rectangular whorl section,broadly rounded or nearly tabulate venter,rounded ventral shoulders, and slightly convex
flanks with maximum whorl width near ventral shoulder. Umbilicus moderately wide withmoderately high, gently inclined wall. Ornamentation consists of large, spiny tubercles onventrolateral shoulders as well as variable
strength, slightly sinuous, prorsiradiate ribsthat arise on or slightly above umbilical shoulder and culminate in the large tubercles on theventral shoulder. Ribs and ventrolateral tubercles abruptly disappear on mature body chamber, but weaker tubercles may rarely re-occur.
Suture not preserved.
Measurements (mm):Specimen no.

D

U

H

W

U/D W/HNMNS PM23678
NMNS PM23668
NMNS PM23666
NMNS PM23676
NMNS PM23679
NMNS PM23770
NMNS PM23684
NMNS PM23695
NMNS PM23670
NMNS PM23683
NMNS PM23771
NMNS PM23685
NMNS PM23769
NMNS PM23677
NMNS PM23768
NMNS PM23687

62.4
65.0
72.0
72.5
74.0
74.0
75.5
76.0
78.0
79.0
79.0
80.5
82.5
84.0
87.0
90.5

21.0
20.5
24.0
24.0
23.5
25.6
25.6
25.0
25.0
26.3
28.0
27.0
31.0
26.4
31.0
30.4

25.0
25.0
28.0
30.5
28.0
29.0
30.0
27.0
31.5
31.7
—
32.0
30.0
34.0
31.0
35.5

—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—

0.34
0.32
0.33
0.33
0.32
0.35
0.34
0.33
0.32
0.33
0.35
0.34
0.38
0.31
0.36
0.34

—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—

Discussion: The described specimens differ from Tirolites cassianus (Quenstedt, 1849)
by their more involute shell, narrower umbilicus and nearly smooth mature body chamber,and they likely represent a new species. However, we hesitate to propose a new specific144

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 103.

Tirolites sp. nov., from KC02-14. 1–4, NMNS PM23666. 5–8, NMNS PM23667.

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 104.

Tirolites sp. nov., from KC02-14. 1–4, NMNS PM23668. 5, NMNS PM23669.

145

146

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 105. Tirolites sp. nov., from KC02-4. 1–4, NMNS PM23670. 5, NMNS PM23671 (rubber cast of outermold). 6, NMNS PM23672 (rubber cast of outer mold).

Olenekian (Early Triassic) in northeastern Vietnam

147

Fig. 106. Tirolites sp. nov., from KC02-15. 1, NMNS PM23673. 2, NMNS PM23674. 3, NMNS PM23675. 4,
NMNS PM23676. 5, NMNS PM23677. All specimens are rubber casts of the outer molds.

148

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 107. Tirolites sp. nov., from KC02-15. 1, NMNS PM23678. 2, NMNS PM23679. 3, NMNS PM23680. 4,
NMNS PM23681.

Olenekian (Early Triassic) in northeastern Vietnam

Fig. 108.

Tirolites sp. nov., from KC02-15. 1–3, NMNS PM23684. 4, NMNS PM23682. 5, NMNS PM23683.

149

150

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 109.

Tirolites sp. nov., from KC02-15. 1–4, NMNS PM23685. 5–8, NMNS PM23686.

Olenekian (Early Triassic) in northeastern Vietnam

151

Fig. 110. Tirolites sp. nov., from KC02-15. 1–4, NMNS PM23687. 5, NMNS PM23688 (rubber cast of outermold).

152

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 111. Tirolites sp. nov., from KC02-15. 1–4, NMNS PM23690. 5, NMNS PM23689 (rubber cast of outermold).

Olenekian (Early Triassic) in northeastern Vietnam

153

Fig. 112. Tirolites sp. nov. 1–2, from KC02-15. 1, NMNS PM23768. 2, NMNS PM23769. 3–4, from KC02-16.
3, NMNS PM23770 (rubber cast of outer mold). 4, NMNS PM23771 (rubber cast of outer mold).

154

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 113. Tirolites sp. nov. 1–4, from KC02-18. 1, NMNS PM23695. 2, NMNS PM23696. 3, NMNS PM23697.
4, NMNS PM23698. 5–6, from BT02-06. 5, NMNS PM23692. 6, NMNS PM23691. All specimens are rubber
casts of outer molds.

Olenekian (Early Triassic) in northeastern Vietnam

name because the specimens are poorly preserved and the suture line is unknown.
Occurrence: Described specimens from
KC02-14, KC02-15 and KC02-16 within the
portion of the Triassospathodus symmetricus
Zone represented by the Tirolites sp. nov. beds
(Lower Spathian = lower Upper Olenekian),and those from BT02-06, KC02-18 and NT0110 within the Tirolites sp. nov. beds (Lower
Spathian = lower Upper Olenekian) in the Bac
Thuy Formation, northeastern Vietnam.
Family Columbitidae Spath, 1934
Genus Columbites Hyatt and Smith, 1905
Type species: Columbites parisianus Hyattand Smith, 1905.
Columbites sp. indet.
Fig. 114

Material examined: Six specimens,
NMNS PM23699–23704, from KC02-14, four
specimens, NMNS PM23705–23708, from
KC02-15, one specimen, NMNS PM23709,
from KC02-18, two specimens, NMNS
PM23710–23711, from BT02-06, one specimen, NMNS PM23712, from BR01-08, three
specimens, NMNS PM23713–23715, fromNT01-10, one specimen, NMNS PM23716,
from NT01-11, and one specimen, NMNS
PM23716, from NT01-12.
Description: Very evolute, fairly depressedshell with quadratic whorl section, broadly
rounded venter, rounded ventral shoulders,and slightly convex flanks. Umbilicus widewith moderately high, gently inclined wall.
Ornamentation consists of strong radial ribsthat arise on umbilical shoulder and project
forward prominently on outer flanks, thus creating impression of tubercles and sinus onventral shoulders. Ribs continue across venter
adorally and are associated with parallel anddeep, but variable strength constrictions. Suture not preserved.
Discussion: The described specimens are
more or less laterally crushed – they may sim-155

ply be juvenile forms of an undetermined species of Columbites. Although they appear to be
somewhat similar to Columbites parisianus
Hyatt and Smith, 1905, their poor preservationprecludes a definitive species assignment.
Occurrence: Described specimens from
KC02-14 and KC02-15 within the portion of
the Triassospathodus symmetricus Zone represented by the Tirolites sp. nov. beds (Lower
Spathian = lower Upper Olenekian), and thosefrom KC02-18, BT02-06, BR01-08, NT01-10,
NT01-11 and NT01-12 within the Tirolites sp.
nov. beds (Lower Spathian = lower Upper Olenekian) in the Bac Thuy Formation, northeastern Vietnam.
Genus Yvesgalleticeras Guex et al., 2005
Type species: Preflorianites montpelieren­
sis Kummel, 1969.
Yvesgalleticeras? sp. indet.
Fig. 115

Material examined: Five specimens,
NMNS PM23718–23722, from BT02-06, one
specimen, NMNS PM23723, from BT02-07,
one specimen, NMNS PM23724, from BT0208, one specimen, NMNS PM23725, from
KC02-15, and one specimen, NMNS
PM23726, from KC02-18.
Description: Very evolute, fairly compressed shell with elliptical whorl section,rounded venter, rounded ventral shoulders,and slightly convex flanks with maximum
whorl width near mid-flank. Umbilicus widewith low, gently inclined wall. Ornamentationconsists of radial to slightly concave ribs. Suture not preserved.
Discussion: The assignment of the specimens to Yvesgalleticeras is uncertain becauseof their poor preservation and lack of suturelines, and is based only on the similarity of
their morphology with Yvesgalleticeras. In
particular, they are somewhat similar to inner
whorls of Yvesgalleticeras montpelierense(Kummel, 1969) from western USA (Guex et156

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 114. Columbites sp. indet. 1–10, from KC02-14. 1, NMNS PM23699. 2–3, NMNS PM23700. 4, NMNS
PM23701. 5–7, NMNS PM23702. 8, NMNS PM23703. 9–10, NMNS PM23704. 11–13, rubber casts of outermolds from KC02-15. 11, NMNS PM23705. 12, NMNS PM23706. 13, NMNS PM23707. 14, NMNS
PM23708, from KC02-14. 15, NMNS PM23709, from KC02-18. 16–17, rubber casts of outer molds fromBT02-06. 16, NMNS PM23710. 17, NMNS PM23711. 18, NMNS PM23712 (rubber cast of outer mold),from BR01-08. 19–21, from NT01-10. 19, NMNS PM23713. 20, NMNS PM23714 (rubber cast of outermold). 21, NMNS PM23715. 22, NMNS PM23716, from NT01-11. 23, NMNS PM23717, from NT01-12.

Olenekian (Early Triassic) in northeastern Vietnam

157

Fig. 115. Yvesgalleticeras? sp. indet. 1–5, from BT02-06. 1, NMNS PM23718. 2, NMNS PM23719. 3, NMNS
PM23720. 4, NMNS PM23721. 5, NMNS PM23722. 6, NMNS PM23723, from BT02-07. 7, NMNS
PM23724, from BT02-08. 8, NMNS PM23725, from KC02-15. 9, NMNS PM23726, from KC02-18. All
specimens except for NMNS PM23725 are rubber casts of outer molds.

al., 2010).
Occurrence: Described specimens from
KC02-15 within the portion of the Triasso­
spathodus symmetricus Zone represented by
the Tirolites sp. nov. beds (Lower Spathian = lower Upper Olenekian), and those from
KC02-18, BT02-06, BT02-07 and BT02-08
within the Tirolites sp. nov. beds (Lower
Spathian = lower Upper Olenekian) in the Bac
Thuy Formation, northeastern Vietnam.
Superfamily Megaphyllitoidea Mojsisovics,
1896
Family Procarnitidae Chao, 1959
Genus Procarnites Arthaber, 1911
Type species: Parapopanoceras kokeni
Arthaber, 1908.
Procarnites? sp. indet.
Fig. 116

Material examined: Three specimens,
NMNS PM23653–23655, from KC02-14.
Description: Fairly involute, very com-pressed shell with subelliptical whorl section,
narrow rounded venter, indistinct ventral
shoulders, and slightly convex flanks withmaximum whorl width at mid-flank. Umbilicus fairly narrow with moderately high, vertical wall and abruptly rounded shoulders. Ornamentation consists of sigmoidal growthlines strongly projected forwards on outerflank and low, weak folds. Suture ceratitic
with subphylloid saddles. First lateral saddle
lower than second saddle, and third saddle
only slightly lower than second saddle. First
lateral lobe deep, wide with many denticulations at base, and second lateral lobe narrowerand shallower than first lobe.
Measurements (mm):Specimen no.
D
NMNS PM23654 40.9

U
9.7

H
17.7

W
9.2

U/D W/H
0.34 0.52

Discussion: The assignment of the specimens to Procarnites is uncertain because of
their poor preservation and is based only thesimilarity of their shell morphology and sutureline with Procarnites. They are somewhat
similar to specimen (IPUW 1911-4-11) de-158

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 116. Procarnites? sp. indet., from KC02-14. 1–4, NMNS PM23653. 5–6, NMNS PM23654. 7–10, NMNS
PM23655.

Olenekian (Early Triassic) in northeastern Vietnam

159

Fig. 117. Eodanubites? sp. indet. 1–5, from KC02-14. 1, NMNS PM23727 (rubber cast of outer mold). 2–4,
NMNS PM23728. 5, NMNS PM23729. 6–7, from KC02-15. 6, NMNS PM23730 (rubber cast of outer mold).
7, NMNS PM23731 (rubber cast of outer mold). 8, NMNS PM23732, from KC02-19. 9, NMNS PM23733(rubber cast of outer mold), from BT02-08. 10–12, from NT01-08. 10, NMNS PM23734 (rubber cast of outermold). 11, NMNS PM23735 (rubber cast of outer mold). 12, NMNS PM23736.

scribed as Procarnites kokeni (Arthaber, 1908)
by Arthaber (1911, pl. 18, fig. 5) in that it has
a slender shell form.
Occurrence: Described specimen from
KC02-14 within the portion of the Triasso­
spathodus symmetricus Zone represented by
the Tirolites sp. nov. beds (Lower Spathian =lower Upper Olenekian) in the Bac Thuy Formation, northeastern Vietnam.

Superfamily Ceratitaceae Mojsisovics, 1879
Family Danubitidae Spath, 1951
Genus Eodanubites Wang, 1978
Type species: Eodanubites xinyuanensis
Wang, 1978.
Eodanubites? sp. indet.
Figs. 117, 118

Material examined: Three specimens,
NMNS PM23727–23729, from KC02-14, two
specimens, NMNS PM23730–23731, from
KC02-15, one specimen, NMNS PM23732,

160

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 118. Eodanubites? sp. indet., from BT02-06. 1, NMNS PM23737. 2, NMNS PM23738. 3, NMNS
PM23739. 4, NMNS PM23740. 5, NMNS PM23741. 6, NMNS PM23742. 7, NMNS PM23743. 8, NMNS
PM23744. 9, NMNS PM23745. 10, NMNS PM23746. 11, NMNS PM23747. 12, NMNS PM23748. 13,
NMNS PM23749. 14, NMNS PM23750. 15, NMNS PM23751. 16, NMNS PM23752. 17, NMNS PM23753.
All specimens are rubber casts of outer molds.

Olenekian (Early Triassic) in northeastern Vietnam

from KC02-19, seventeen specimens, NMNS
PM23737–23753, from BT02-06, one specimen, NMNS PM23733, from BT02-08, andthree specimens, NMNS PM23734–23736,
from NT01-10.
Description: Fairly evolute, fairly compressed shell with elliptical whorl section,rounded venter, rounded ventral shoulders,and slightly convex flanks with maximum
whorl width near mid-flank. Umbilicus fairly
wide with low, vertical wall and roundedshoulders. Ornamentation consists of strong,radial or slightly rursiradiate rounded ribs arising on umbilical shoulder, becoming mostprominent at mid-flank and weakening at ventral shoulder. Suture not preserved.
Discussion: Assignment of the specimens
to Eodanubites is uncertain because of theirpoor preservation and lack of suture lines, andis based only on the similarity of their morphology with Eodanubites. They are somewhat similar to Eodanubites (Dumitricaceras)
judae (Guex et al., 2005) from western USA(Guex et al., 2010).
Occurrence: Described specimens from
KC02-14 and KC02-15 within the portion of
the Triassospathodus symmetricus Zone represented by the Tirolites sp. nov. beds (Lower
Spathian = lower Upper Olenekian), and thosefrom KC02-19, BT02-06, BT02-08 and NT0110 within the Tirolites sp. nov. beds (Lower
Spathian = lower Upper Olenekian) in the Bac
Thuy Formation, northeastern Vietnam.
Order Phylloceratida Zittel, 1884
Superfamily Ussuritoidea Hyatt, 1900
Family Palaeophyllitidae Popov, in Luppov
and Drushchits, 1958
Genus Goudemandites Brühwiler et al., 2012aType species: Goudemandites sinensis
Brühwiler et al., 2012a.

161

Gaudemandites langsonensis
Shigeta and Nguyen sp. nov.
Fig. 119
Eophyllites sp. nov. Tong et al., 2004, p. 201, pl. 2, figs.
16–17.

Type specimen: Holotype, NMNS
PM23639, consists of the phragmocone andmost of the body chamber, which begins at adiameter of about 60 mm and occupies nearly
two-thirds of the outer whorl. Specimen wascollected from KC02-14.
Diagnosis: Moderatory evolute Goude­
mandites with subtrapezoidal whorl section,
ornamented with slightly biconcave, fine lirae
and very weak, radial plications.
Etymology: Named after Lang Son City,
northeastern Vietnam.
Description: Moderately evolute, fairly
compressed shell with subtrapezoidal whorl
section, broadly rounded venter, rounded ventral shoulders, and slightly convex flanks withmaximum whorl width near umbilical shoulder. Umbilicus moderately wide with moderately high, vertical wall and rounded shoulders. Ornamentation consists of very weak, radial plications, as well as slightly biconcave,fine lirae. Suture ceratitic with subphylloid
saddles. First lateral saddle nearly equal tosecond saddle, and third saddle even lower.
First lateral lobe deep, wide with many denticulations at base, and second lateral lobe about
two thirds depth of first lobe.
Measurements (mm):Specimen no.
DUH
W U/D W/H
NMNS PM23639 60.0 18.9 26.5 22.7 0.32 0.86

Comparison: Gaudemandites langsonensis
sp. nov. is close to G. sinensis Brühwiler et al.,2012a from the Middle Smithian in South
China and Oman, but differs by its subtrapezoidal whorl section and ornamentation consisting of very weak, radial plications. Specimens described as Eophyllites sp. nov. by
Tong et al. (2004, pl. 2, figs. 16) from the Co­
lumbites-Tirolites Zone in East China are very
similar to G. langsonensis and are probably

162

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 119. Gaudemandites langsonensis Shigeta and Nguyen sp. nov., from KC02-14. 1–5, NMNS PM23639, holotype. White arrows indicate shell breakage. Suture line drawn at position indicated by black arrow.

Olenekian (Early Triassic) in northeastern Vietnam

conspecific.
Remarks: A major sub-lethal shell break
and repair scar are visible on the shell of theholotype. Its outer flank and ventral portion
were severly damaged and nearly one-sixth ofthe outer whorl was lost.
Occurrence: Described specimen from
KC02-14 within the portion of the Triasso­
spathodus symmetricus Zone represented by
the Tirolites sp. nov. beds (Lower Spathian = lower Upper Olenekian) in the Bac Thuy
Formation, northeastern Vietnam. This species
also occurs in the Lower Spathian (Colum­
bites-Tirolites Zone in Tong et al., 2004) inEast China.
Incertae sedis
Genus gen. indet. A
Fig. 120.1–120.3

Material examined: One specimen, NMNS
PM23754, from BT02-04.
Description: Moderately evolute, fairly
compressed shell with elliptical whorl section,arched venter, rounded ventral shoulders, andslightly convex flanks with maximum whorl
width near mid-flank. Umbilicus fairly narrow
with moderately high, vertical wall and rounded shoulders. Ornamentation consists of sigmoidal ribs, more pronounced near venter. Suture not visible.
Occurrence: Described specimen fromBT02-04 within the portion of the Novispatho­
dus ex gr. waageni Zone that includes the
Leyeceras horizon of the Owenites koeneni
beds (middle Middle Smithian = middle lower
Olenekian) in the Bac Thuy Formation, northeastern Vietnam.
Genus gen. indet. B
Fig. 120.4–120.5

Material examined: One specimen, NMNS
PM23755, from BT01-09.
Description: Very evolute, very compressed shell with narrow tabulate venter,rounded ventral shoulders, and convex flanks

163

with maximum whorl width near mid-flank.
Umbilicus fairly wide with moderately high,oblique wall and rounded shoulders. Shell surface smooth. Suture not visible.
Occurrence: Described specimens fromBT01-09 within the portion of the Novispatho­
dus ex gr. waageni Zone that includes the Ur­
dyceras tulongensis beds (lower Middle Smithian = middle Lower Olenekian) in the Bac
Thuy Formation, northeastern Vietnam.
Genus gen. indet. C
Fig. 121.1–121.2

Material examined: One specimen, NMNS
PM23756, from KC01-10.
Description: Involute, fairly compressedshell with tabulate or subtabulate venter, angular ventral shoulders, and slightly convex
flanks with maximum whorl width near midflank. Umbilicus narrow. Ornamentation consists of dense, concave,fine and projected ribs.
Suture not visible.
Occurrence: Described specimen from
KC01-10 within the portion of the Novispath­odus ex gr. waageni Zone that includes the
Leyeceras horizon of the Owenites koeneni
beds (middle Middle Smithian = middle Lower
Olenekian) in the Bac Thuy Formation, northeastern Vietnam.
Genus gen. indet. D
Fig. 121.3–121.4

Material examined: One specimen, NMNS
PM23757, from NT01-10.
Description: Fairly evolute, very compressed shell with subelliptical whorl section,arched venter, rounded ventral shoulders, andflat, subparallel flanks. Umbilicus moderately
wide with moderately high, oblique wall. Ornamentation consists of dense, sigmoidal fineribs strongly projected forwards on outerflank. Suture not preserved.
Occurrence: Described specimen fromNT01-10 within the Tirolites sp. nov. beds
(Lower Spathian = lower Upper Olenekian) in164

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 120. 1–3, Genus gen. indet. A, NMNS PM23754, from BT02-04. 4–5, Genus gen. indet. B, NMNS
PM23755, from BT01-09.

Olenekian (Early Triassic) in northeastern Vietnam

165

Fig. 121. 1–2, Genus gen. indet. C, NMNS PM23756, from KC01-10. 3–4, Genus gen. indet. D, NMNS
PM23757 (rubber cast of outer mold), from NT01-10. 5–7, Genus gen. indet. E. 5, NMNS PM23758 (rubber
cast of outer mold), from KC02-15. 6–7, NMNS PM23759, from KC02-14. 8–10, Genus gen. indet. F. 8,
NMNS PM23767, from KC02-16. 9, NMNS PM23646 (rubber cast of outer mold), from a float mudstone
block at KC02. 10, NMNS PM23647 (rubber cast of outer mold), from a float mudstone block at KC02.

166

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 122. 1–6, Genus gen. indet. G, from KC02-14. 1, NMNS PM23656. 2, NMNS PM23657. 3, NMNS
PM23658. 4, NMNS PM23659. 5, NMNS PM23660. 6, NMNS PM23661. All specimens are rubber casts ofouter molds.7, Genus gen. indet. H, NMNS PM23789 (rubber cast of outer mold), from KC02-16.

the Bac Thuy Formation, northeastern Vietnam.
Genus gen. indet. E
Fig. 121.5–121.7

Material examined: One specimen, NMNS
PM23759, from KC02-14 and one specimen,
NMNS PM23758, from KC02-15.
Description: Very evolute, very compressed shell with elliptical whorl section,arched venter, rounded ventral shoulders, andslightly convex flanks with maximum whorl
width near mid-flank. Umbilicus wide withlow, vertical wall and rounded shoulders. Ornamentation consists of periodic major ribs
with parabolic nodes on ventrolateral margin
and radial rounded ribs, arising on umbilicalshoulder, becoming most prominent at midflank and weakening at ventral shoulder. Suture not preserved.
Occurrence: Described specimen from

Olenekian (Early Triassic) in northeastern Vietnam

KC02-14 and KC02-15 within the portion of
the Triassospathodus symmetricus Zone represented by the Tirolites sp. beds (Lower Spathian = lower Upper Olenekian) in the Bac Thuy
Formation, northeastern Vietnam.
Genus gen. indet. F
Fig. 121.8–121.10

Material examined: Two specimens,
NMNS PM23646–23647, from float mudstone
blocks in KC02 and one specimen, NMNS
PM23767, from KC02-16.
Description: Moderately evolute, very
compressed shell with slightly convex flanks
with maximum whorl width near mid-flank.
Umbilicus moderately wide with low, verticalwall and rounded shoulders. Ornamentationconsists of strong, sigmoidal ribs. Suture notpreserved.
Occurrence: Described specimens from
KC02-16 within the portion of the Triasso­
spathodus symmetricus Zone represented by
the Tirolites sp. nov. beds (Lower Spathian = lower Upper Olenekian), and those fromfloat mudstone blocks probably derived fromthe mudstone within the Tirolites sp. nov. beds
(Lower Spathian = lower Upper Olenekian) in
the Bac Thuy Formation, northeastern Vietnam.
Genus gen. indet. G
Fig. 122.1–122.6

Material examined: Six specimens,
NMNS PM23656–23661, from KC02-15.
Description: Fairly evolute, very compressed shell with subelliptical whorl section,arched venter, rounded ventral shoulders, andflat, subparallel flanks. Umbilicus moderately
wide with moderately high, vertical wall andabruptly rounded shoulders. Ornamentationconsists of sigmoidal growth lines that form
umbilical bullae and rib-like plications, becoming strongly projected forwards on outerflank. Suture not preserved.
Measurements (mm):Specimen no.
NMNS PM23657
NMNS PM23656
NMNS PM23661
NMNS PM23659
NMNS PM23660

167

D
24.6
32.0
33.0
45.0
57.0

U
8.2
11.8
11.3
14.5
21.0

H
9.6
12.5
11.8
19.2
20.2

W
—
—
—
—
—

U/D W/H
0.33 —
0.37 —
0.34 —
0.32 —
0.37 —

Occurrence: Described specimen from
KC02-15 within the portion of the Triasso­
spathodus symmetricus Zone represented by
the Tirolites sp. nov. beds (Lower Spathian = lower Upper Olenekian) in the Bac Thuy
Formation, northeastern Vietnam.
Genus gen. indet. H
Fig. 122.7

Material examined: One specimen, NMNS
PM23789, from KC02-16.
Description: Very involute, very compressed shell with narrow rounded venter,rounded ventral shoulders, and slightly convex
flanks with maximum whorl width near midflank. Umbilicus narrow with low, verticalwall and abruptly rounded shoulders. Suturewith probably subphylloid saddles partly visible.
Measurements (mm):Specimen no.
D
NMNS PM23789 35.0

U
5.0

H
18.6

W
—

U/D W/H
0.14 —

Occurrence: Described specimen from
KC02-16 within the portion of the Triasso­
spathodus symmetricus Zone represented by
the Tirolites sp. nov. beds (Lower Spathian = lower Upper Olenekian) in the Bac Thuy
Formation, northeastern Vietnam.
Gastropods (by A. Kaim, A. Nützel and T.
Maekawa)
Systematic descriptions basically follow
the classification by Bouchet et al. (2005).
Morphological terms are those used in theTreatise on Invertebrate Paleontology (Cox,1960) and the glossary of malacological terms
by Arnold (1965).
The present material consists entirely ofsmall specimens (smaller 1 mm) and repre-

168

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 123. Gastropods from the lowest Middle Smithian. 1–3, unidentified caenogastropod, NMNS PM23849,
from BT01-04. 4–6, ?Atorcula sp. indet., NMNS PM23848, from BT02-01.

sents protoconchs and/or early juveniles. The
specimens are silicified and most are internalmoulds so that the ornament is rarely preserved. For these reasons, open nomenclaturemust be used and all generic assignments aretentative. However, it is possible to characterize various different forms.
Institution abbreviation: NMNS = National
Museum of Nature and Science, Tsukuba
Class Gastropoda Cuvier, 1795
Order Vetigastropoda Salvini-Plawen, 1980
Superfamily Trochonematoidea von Zittel, 1895
Family Lophospiridae Wenz, 1938
Genus Worthenia de Koninck, 1883
Type species: Turbo tabulatus Conrad,
1835.

Worthenia? sp. indet.
Fig. 124.1–124.6

Material examined: One juvenile specimen, NMNS PM23800, from BT01-06 andone specimen, NMNS PM23801, from KC0104.
Description: Shell from sample BT01-06(Fig. 124.1–124.3) relatively well preserved
consisting of 3.5 round convex turbiniform
whorls with deep sutures and covered with
granular micro-ornament. Small umbilicus
present. Aperture circular. Demarcation between larval shell and teleoconch not visible.
Selenizone not yet developed.
Discussion: This shell is most likely a juvenile of a Worthenia-like gastropod. Bandel(2009) argues that the Triassic species ofWorthenia should be classified as Pseudos­
chizogonium Kutassy, 1937 (with the Late Tri-

Olenekian (Early Triassic) in northeastern Vietnam

169

Fig. 124. Gastropods from the lower Middle Smithian. 1–6, Worthenia? sp. indet. 1–3, NMNS PM23800, fromBT01-06. 4–6, NMNS PM23801, from KC01-04. 7–12, Naticopsis sp. indet. A. 7–9, NMNS PM23812, fromBT01-06. 10–12, NMNS PM23813, from BT01-07.

170

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 125. Gastropods from the lower Middle Smithian. Atorcula sp. indet. 1–3, NMNS PM23840, from KC0104. 4–6, NMNS PM23834, from BT01-07. 7–9, NMNS PM23835, from BT01-07. 10–12, NMNS PM23836,
from BT01-07.

Olenekian (Early Triassic) in northeastern Vietnam

171

Fig. 126. Gastropods from the lower Middle Smithian. Atorcula sp. indet. 1–3, NMNS PM23837, from BT0107. 4–6, NMNS PM23838, from BT01-07. 7–9, NMNS PM23839, from BT01-07. 10–12, NMNS PM23841,
from KC01-04.

172

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 127. Gastropods from the lower Middle Smithian. 1–6, Atorcula sp. indet. 1–3, NMNS PM23842, from
KC01-04. 4–6, NMNS PM23843, from BT01-06. 7–9, unidentified caenogastropod, NMNS PM23850, fromBT01-06.

Olenekian (Early Triassic) in northeastern Vietnam

assic type species Pseudoschizogonium turric­ulatum Kutassy, 1937) rather than Worthenia(having the Carboniferous type species). The
problem of Pseudoschizogonium vs. Worthe­nia needs further research in our opinion assome Triassic species (including our specimens from Vietnam) are more reminiscent of
the Carboniferous type species of Worthenia
than the Late Triassic type species of Pseudos­
chizogonium. The Early Triassic species ofWorthenia were previously reported from
Utah, USA (Batten and Stokes, 1986), Oman
(Wheeley and Twitchett, 2005), and South Primorye, Russia (Kaim, 2009). Some additional
reports from Greenland (Spath, 1930, 1935)
and China (Pan, 1982; Zhan, 1995) require review. Unpublished micrographs of early
whorls of Worthenia from the Smithian Sinbad
Limestone closely resemble the present specimens from Vietnam. In these species, the slit
develops late during ontogeny.
Occurrence: Described specimen collectedfrom BT01-06 and KC01-04 within the Novis­
pathodus ex gr. waageni Zone in the Bac Thuy
Formation, northeastern Vietnam. BT01-06 is
located between the Flemingites rursiradiatus
beds (lowest Middle Smithian = middle Lower
Olenekian) and the Urdyceras tulongensis
beds (lower Middle Smithian = middle Lower
Olenekian). KC01-04 is located beneath theOwenites koeneni beds (middle Middle Smithian = middle Lower Olenekian).
Superfamily Trochoidea Rafinesque, 1815
Family Turbinidae Rafinesque, 1815
Subfamily Anomphalinae Wenz, 1938
Genus Anomphalus Meek and Worthen, 1867
Type species: Anomphalus rotulus Meek
and Worthen, 1867.
Anomphalus? sp. indet.

173

specimens, NMNS PM23805–23809, from
KC02-03, and one specimen, NMNS
PM23810, from KC02-10.
Description: All available specimens juveniles of about two whorls or less. Shells lowspired, rotelliform with convex whorls. Shellsurface smooth. Initial whorl orthostrophic.
Protoconch/teleoconch demarcation not visible. Umbilicus well developed. Aperture circular.
Discussion: The shells under consideration
are poorly preserved juveniles of rather simple
morphology. The low rotelliform shells withorthostrophic protoconch are characteristic forsmall vetigastropods of turbinid affinity. Suchshells in the Paleozoic and Triassic (see e.g.,Haas, 1953; Bandel, 1993; Nützel and Nakazawa, 2012) are classified in the family Anomphalidae (here downranked to subfamily). We
follow this identification in preliminarily classifying our shells from Vietnam as Anompha­
lus? sp. indet.
Occurrence: Described specimens fromBT01-15, KC02-02 and KC02-03 within theNovispathodus ex gr. waageni Zone that includes the Leyeceras and the Guodunites horizons of the Owenites koeneni beds (middle toupper Middle Smithian = middle Lower Olenekian), and those from KC02–10 within the
portion of the Novispathodus pingdingshanen­
sis Zone represented by the Xenoceltites vario­
costatus beds (Upper Smithian = upper Lower
Olenekian) in the Bac Thuy Formation, northeastern Vietnam.
Order Neritimorpha Koken, 1896
Superfamily Neritoidea Rafinesque, 1815
Family Naticopsidae Waagen, 1880
Genus Abrekopsis Kaim, 2009
Type species: Naticopsis (Naticopsis) de­pressispirus Batten and Stokes, 1986.

Figs. 128.4–128.12, 134

Material examined: One specimen, NMNS
PM23802, from BT01-15, two specimens,
NMNS PM23803–23804, from KC02-02, five

Abrekopsis? sp. indet.
Fig. 128.13–128.15

Material examined: One specimen, NMNS

174

Shigeta, Komatsu, Maekawa and Dang (eds.)

PM23811, from BT02-03.
Description: Juvenile neritoid shell withflattened upper whorl surface and whorls embracing above periphery. Shell surface densely
covered with fine orthoclinal lirae probably reflecting some selective erosional feature of external shell layer. Aperture drop-shaped. Smallumbilicus present.
Discussion: The shell resembles Abrekop­
sis depressispirus (Batten and Stokes, 1986)
from the Early Triassic of Russia (Kaim,
2009) and the United States (Batten andStokes, 1986), however, it is juvenile andpoorly preserved; the diagnostic protoconch isalso preserved and it may actually belong also
to some other neritoid gastropod. The suture is
reduced in the earliest whorls and this may indicate that this neritimorph resorbed the innershell walls as is typical for modern Neritidae.
Occurrence: Described specimen fromBT02-03 within the portion of the Novispatho­
dus ex gr. waageni Zone represented by the
Leyeceras horizon of the Owenites koeneni
beds (middle Middle Smithian = middle Lower
Olenekian) in the Bac Thuy Formation, northeastern Vietnam.
Genus Naticopsis McCoy, 1844
Type species: Naticopsis phillipsii McCoy,
1844.
Naticopsis sp. indet. A
Figs. 124.7–124.12, 130.7–130.12, 131, 132.1–132.3,
135.1–135.3

Material examined: One specimen, NMNS
PM23812, from BT01-06, one specimen,
NMNS PM23813, from BT01-07, two specimens, NMNS PM23814–23815, from BT0115, four specimens, NMNS PM23816–23819,
from BT02-03, one specimen, NMNS
PM23820, from KC01-12, and one specimen,
NMNS PM23821, from KC02-10.
Description: Juvenile relatively highspired naticopsid shell with shallow but sharply incised suture and bulbous initial whorl.

Aperture drop-shaped.
Discussion: The shells under considerations are similar to Naticopsis utahensis Batten and Stokes, 1986 from Early Triassic of
Utah (Batten and Stokes, 1986). Similar species have also been reported from the Early
Triassic of China (Kaim et al., 2010) and Pakistan (Kaim et al., 2013), however, the juvenile
nature of our material discourages us from attributing the Naticopsis sp. indet. A to any formally named species.
Occurrence: Described specimens collected from BT01-06, BT01-07, BT01-15, BT0203 and KC01-12 within the Novispathodus ex
gr. waageni Zone in the Bac Thuy Formation,
northeastern Vietnam. BT01-06 and BT01-07
are located between the Flemingites rursiradi­
atus beds (lowest Middle Smithian = middle
Lower Olenekian) and the Urdyceras tulon­
gensis beds (lower Middle Smithian = middle
Lower Olenekian). BT01-15, BT02-03 andKC01-12 are located the Leyeceras horizon of
the Owenites koeneni beds (middle Middle
Smithian = middle Lower Olenekian), andthose from KC02-10 within the portion of theNovispathodus pingdingshanensis Zone represented by the Xenoceltites variocostatus beds
(Upper Smithian = upper Lower Olenekian) in
the Bac Thuy Formation, northeastern Vietnam.
Naticopsis sp. indet. B
Figs. 129, 130.1–130.5

Material examined: Five specimens,
NMNS PM23822–23826, from BT02-03,
three specimens, NMNS PM23827–23829,
from BT01-14, and one specimen, NMNS
PM23830, from KC01-13.
Description: Juvenile relatively low-spired
naticopsid shell with slightly flattened upper
whorl surface and shallow but sharply incised
suture and bulbous initial whorl. Aperture
rectangular with rounded corners.
Discussion: Naticopsis sp. indet. B differsfrom Naticopsis sp. indet. A in having polygo-Olenekian (Early Triassic) in northeastern Vietnam

175

Fig. 128. Gastropods from the middle to upper Middle Smithian. 1–3, Strobeus sp. indet., NMNS PM23831,
from BT01-15. 4–12, Anomphalus? sp. indet. 4–6, NMNS PM23802, from BT01-15. 7–9, NMNS PM23803,
from KC02-02. 10–12, NMNS PM23804, from KC02-02. 13–15, Abrekopsis? sp. indet., NMNS PM23811,
from BT02-03.

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 129. Gastropods from the middle to upper Middle Smithian. Naticopsis sp. indet. B. 1–3, NMNS PM23830,
from KC01-13. 4–6, NMNS PM23822, from BT02-03. 7–9, NMNS PM23823, from BT02-03. 10–12, NMNS
PM23824, from BT02-03. 13–14, NMNS PM23827, from BT01-14. 15, NMNS PM23828, from BT01-14.

Olenekian (Early Triassic) in northeastern Vietnam

177

Fig. 130. Gastropods from the middle to upper Middle Smithian. 1–5, Naticopsis sp. indet. B. 1, NMNS
PM23829, from BT01-14. 2–3, NMNS PM23825, from BT02-03. 4–5, NMNS PM23826, from BT02-03. 6,
unidentified gastropod, NMNS PM23851, from KC01-12. 7–12, Naticopsis sp. indet. A. 7–9, NMNS
PM23814, from BT01-15. 10–12, NMNS PM23815, from BT01-15.

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 131. Gastropods from the upper Middle Smithian. Naticopsis sp. indet. A, from BT02-03. 1–3, NMNS
PM23816. 4–6, NMNS PM23817. 7–9, NMNS PM23818. 10–12, NMNS PM23819.

Olenekian (Early Triassic) in northeastern Vietnam

179

Fig. 132. Gastropods from the middle to upper Middle Smithian. 1–3, Naticopsis sp. indet. A, NMNS PM23820,
from KC01-12. 4–9, Ampezzopleura sp. indet., from BT02-03. 4–6, NMNS PM23832. 7–9, NMNS PM23833.

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 133. Gastropods from the middle Middle Smithian. 1–3, Atorcula sp. indet., NMNS PM23844, from BT0115. 4–9, unidentified caenogastropods, from KC01-13. 4–6, NMNS PM23852. 7–9, NMNS PM23853. 10–12,
unidentified ?gastropod, NMNS PM23854, from KC01-13.

扌Fig. 134. Gastropods from the upper Middle and Upper Smithian. Anomphalus? sp. indet. 1–15, from KC02-03,
1–3, NMNS PM23805. 4–6, NMNS PM23806. 7–9, NMNS PM23807. 10–12, NMNS PM23808. 13–15,
NMNS PM23809. 16–18, NMNS PM23810, from KC02-10.

Olenekian (Early Triassic) in northeastern Vietnam

181

182

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 135. Gastropods from the upper Middle and Upper Smithian. 1–3, Naticopsis sp. indet. A, NMNS
PM23821, from KC02-10. 4–12, Atorcula sp. indet., from KC02-03. 4–6, NMNS PM23845. 7–9, NMNS
PM23846. 10–12, NMNS PM23847.

Olenekian (Early Triassic) in northeastern Vietnam

nal aperture rather than drop-shaped, more
flattened upper whorl surface, and a lower
shell profile. The gross shell morphology of
Naticopsis sp. indet. B is similar to Abrekopsis
depressispirus (Batten and Stokes, 1986) but
the initial whorl is bulbous (naticopsid) andnot flattened as in Abrekopsis (see Kaim,
2009). All shells are early juveniles and we refrain from identifying them to a species level.
Occurrence: Described specimens fromBT01-14, BT02-03 and KC01-13 within the
portion of the Novispathodus ex gr. waageni
Zone represented by the Leyeceras horizon of
the Owenites koeneni beds (middle Middle
Smithian = middle Lower Olenekian) in the
Bac Thuy Formation, northeastern Vietnam.
Order Caenogastropoda Cox, 1960
Superfamily Acteoninoidea Cossmann, 1895
Family Soleniscidae Knight, 1931
Genus Strobeus de Koninck, 1881
Type species: Strobeus ventricosus deKoninck, 1881.
Strobeus sp. indet.
Fig. 128.1–128.3

Material examined: One specimen, NMNS
PM23831, from BT01-15.
Description: Shell of globular fusiform
shape with 3.5 juvenile whorls preserved. Initial whorl corroded. Demarcation between
protoconch and teleoconch not discernible.
Shell surface smooth. Suture moderately impressed, flanks evenly convex with no shoulder or ramp. No clear demarcation between
flank and base. Growth lines not discernible.
Discussion: The shell under consideration
is similar to early whorls of Strobeus pakista­
nensis Kaim, Nützel, Hautmann, and Bucher,2013 from the Smithian of Pakistan (Kaim etal., 2013) though we refrain from including
the shells from Vietnam to the latter species
because of its juvenile nature. Other Early Triassic Strobeus are known from the Smithian of
Utah (Batten and Stokes, 1986; Nützel, 2005),

183

Dienerian of Russia (Kaim, 2009), and from
Griesbachian of Oman (Wheeley and Twitchett, 2005).
Occurrence: Described specimen fromBT01-15 within the portion of the Novispatho­
dus ex gr. waageni Zone within or above theOwenites koeneni beds (middle Middle Smithian = middle Lower Olenekian) in the Bac
Thuy Formation, northeastern Vietnam.
Superfamily Zygopleuroidea Wenz, 1938
Family Zygopleuridae Wenz, 1938
Subfamily Ampezzopleurinae Nützel, 1998
Genus Ampezzopleura Bandel, 1991
Type species: Ampezzopleura tenuis Bandel, 1991.
Ampezzopleura sp. indet.
Fig. 132.4–132.9.

Material examined: Two specimens,
NMNS PM23832–23833, from BT02-03.
Description: Protoconch 1 smooth, slightly bulbous, and composed of about one whorl.
Protoconch 2 composed of 2.5 whorls ornamented by 30 axial ribs per whorl; axial ribs
straight opisthocline to slightly sigmoidal,
continuous from suture to suture. Teleoconch
not present, either not developed or not preserved.
Discussion: The specimen NMNS
PM23832 is a well preserved larval shell of
Ampezzopleura. The specimen NMNS
PM23833 is classified to Ampezzopleura only
conditionally as its external surface is eroded
away and the identification is based solely on
gross shell morphology. We refrain from putting any species name on the larval shellalone. A single species of this genus was identified from the Early Triassic, Ampezzopleurarugosa (Batten and Stokes, 1986) has been reported from the Smithian of Utah, UnitedStates (Nützel and Schulbert, 2005).
Occurrence: Described specimen fromBT02-03 within the portion of the Novispatho­
dus ex gr. waageni Zone represented by the184

Shigeta, Komatsu, Maekawa and Dang (eds.)

Leyeceras horizon of the Owenites koeneni
beds (middle Middle Smithian = middle Lower
Olenekian) in the Bac Thuy Formation, northeastern Vietnam.
Family Protorculidae Bandel 1991
Genus Atorcula Nützel, 1998
Type species: Melania canalifera zu Münster, 1841 sensu Kittl, 1894.
Atorcula sp. indet.
Figs. 123.4–123.6, 125, 126, 127.1–127.6, 133.1–133.3,
135.4–135.12

Material examined: Six specimens,
NMNS PM23834–23839, from BT01-07,
three specimens, NMNS PM23840–23842,
from KC01-04, one specimen, NMNS
PM23843, from BT01-06, one specimen,
NMNS PM23844, from BT01-15, three specimens, NMNS PM23845–23847, from KC0203, and one specimen, NMNS PM23848, fromBT02-01.
Description: Protoconch 1 smooth andcomposed of about one whorl. Protoconch 2
composed of about 1.5–2 whorls ornamented
by about 30 axial ribs; axial ribs opisthocyrt,slightly more incurved in abapical shell portion, and continuous from suture to suture. Teleoconch smooth, whorls convex and sutures
deeply incised. Aperture circular.
Discussion: Atorcula unites protorculid
gastropods characterised by an axially-ribbed
protoconch followed by smooth high-spired
shells; the present taxon differs from the typespecies in being relatively low and in having
convex whorls and incised suture. Most of theshells from Vietnam, which we attributed tothis genus have the outermost ornamented
shell layer eroded away. Nevertheless, in a
number of specimens the protoconch ornamentation is partially or wholly preserved(e.g., Figs. 125.1–125.6, 126.5, 135.4–135.6).
Occurrence: Described specimens fromBT01-06, BT01-07, BT01-15, BT02-01,
KC01-04 and KC02-03 within the Novispath­odus ex gr. waageni Zone in the Bac Thuy
Formation, northeastern Vietnam. BT02-01 isrepresented by the Flemingites rursiradiatus
beds (lowest Middle Smithian = middle Lower
Olenekian). BT01-06 and BT01-07 are locatedbetween the Flemingites rursiradiatus beds
and the Urdyceras tulongensis beds (lower
Middle Smithian = middle Lower Olenekian).
KC01-04 is located beneath the Owenites
koeneni beds (middle Middle Smithian =middle Lower Olenekian). BT01-15 is represented by the Leyeceras horizon of theOwenites koeneni beds. KC02-03 is locatedabove the Guodunites horizon of the Owenites
koeneni beds. Atorcula is known from the Late
Triassic (Nützel 1998); it also resembles someOmphaloptycha species from the Early Triassic which have been reported from Utah (Batten and Stokes, 1986) and Russia (Kaim,
2009).
Bivalves (by T. Komatsu, H. T. Dang and T.
C. Dinh)
Systematic descriptions basically follow
the classification established by Newell (1938)
and Moore (1969).
Abbreviations for shell dimensions: RV =right valve; LV = left valve; H  =shell height;
L = shell length; T = shell thickness.
Institution abbreviations: KMSP = Facultyof Science, Kumamoto University.
Class Bivalvia Linné, 1758
Order Pterioida Newell, 1965
Superfamily Posidonioidea Frech, 1909
Family Posidoniidae Frech, 1909
Genus Bositra de Gregorio, 1886
Type species: Posidonia ornati Quenstedt,
1856.
Remarks: Emended diagnoses of Posido­
nia Bronn, 1828 and Bositra were describedby Waller and Stanley (2005). According toWaller and Stanley (2005), the characteristicsof the right anterior auricle and byssal sinus ofOlenekian (Early Triassic) in northeastern Vietnam

185

Fig. 136. 1–4, Bositra limbata (Guo, 1985). 1, KMSP-5131, from KC02-15, external cast of left valve. 2,
KMSP-5132, from NT01-12, external cast of articulated valves. 3, KMSP-5133, from NT01-07, external castof incomplete left valve. 4, KMSP-5134, from KC02-14, internal cast of left valve. 5, Bositra sp. indet,
KMSP-5135, from KC02-03, external cast of left valve. 6–7, Leptochondria bittneri (Kiparisova, 1938) from
KC02-14. 6, KMSP-5136, external cast of left valve. 7, KMSP-5137, external cast of left valve. 8–10, Critten­
denia langsonensis Komatsu and Dang, 2013. 8, KMSP-5117 (paratype), from KC02-08, left valve. 9, KMSP5120, from NT01-04, left valve. 10, KMSP-5119 (holotype), from NT01-09, left valve. Thick scale bars indicate 1 cm. Thin scale bars 5 mm.

Posidonia are more in line with placement
near the Pterineidae rather than the Pterinopectinidae. Bositra has a single adductor muscle scar and an alivincular ligament. In contrast, Posidonia is characterized by a duplivincular ligament system and anisomyarian adductor musculature. The Triassic “Posidonia”
is placed in Bositra and is common in early
Mesozoic offshore sediments (Waller andStanley, 2005).
Bositra limbata (Guo, 1985)
Fig. 136.1–136.4
Posidonia limbata Guo, 1985, pl. 15, figs. 1, 2.

Types: Type specimens figured by Guo(1985, pl. 15, figs. 1, 2) from the Middle Triassic Baifeng Formation, Jiuzhai, Funing, Yunnan, South China.
Material examined: Disarticulated left
valves and articulated valves (KMSP-5131–
5134) collected from dark gray and greenish
gray laminated mudstones and marls in NT01
and KC02. KMSP-5131 and 5134 are moder-ately well preserved.
Description: Shell small for genus, equivalve, suborbicular to transversely oval in outline, shell length greater than shell height; test
very thin; moderately convex valves, dorsal
margin short and straight, ventral margins
rounded, umbo not prominent but inflated, situated slightly anterior to the middle, auricles
lacking; shell surface (except for umbonalarea) covered with broad concentric ribs, finelamellae and undulations; umbonal area covered with coarse concentric folds and undulations; byssal notch lacking; ligament and adductor muscle impressions unknown.
Measurements (in mm):
Specimen no.
KMSP-5131
KMSP-5134

H
3.2
1.9+

L
4.0
2.3

T
―
―

Remarks
LV
LV

Discussion: Bositra limbata has been described as Posidonia limbata from the Middle
Triassic Baifeng Formation, Jiuzhai, Funing,
Yunnan, South China (Guo, 1985). Guo(1985) described the umbonal area and ornamentation of this species in detail, reporting

186

Shigeta, Komatsu, Maekawa and Dang (eds.)

that the early stage of the shell is much more
inflated than the surrounding tissue, which islike “a gypsy-hat margin”. Fine broad concentric lamellae are rarely found on the fold.
In Vietnam, “Posidonia”, are commonly
reported from the Middle Triassic (Vu Khuc etal., 1991), although almost all species of these
Triassic “Posidonia” probably belonged to
Bositra. These Middle Triassic Vietnamese“Posidonia” are ornamented by many clear
concentric ribs and have never been reported
from the Lower Triassic.
Occurrence: Described specimens fromNT01-07 and KC02-09 within the Novispatho­
dus pingdingshanensis Zone represented by
the Xenoceltites variocostatus beds (upper
Smithian = upper Lower Olenekian), and thosefrom BR01-06 between the Xenoceltites vario­
costatus beds and Tirolites sp. nov. beds
(lower Spathian = lower Upper Olenekian),and those from KC02-14 and KC02-15 within
the Triassospathodus symmetricus Zone represented by the Tirolites sp. nov. beds, and thosefrom NT01-11, NT01-12 and BR01-08 within
the Tirolites sp. nov. beds in the Bac Thuy
Formation, northeastern Vietnam. They co-occur with Crittendenia australasiatica, Critten­
denia langsonensis, Leptochondria bittneri,and “Pseudomonotis” himaica. This species
also occurs in the Middle Triassic Baifeng
Formation, Yunnan, South China (Guo, 1985).
Bositra sp. indet.
Fig. 136.5

Material examined: Poorly preserved disarticulated left valve (KMSP-5135) collectedfrom greenish gray laminated mudstone.
Description: Shell small and suborbicular
to elongately ovate; shell length greater thanshell height; test very thin; moderately convex
valve; dorsal margin short and straight; ventral
margins rounded; umbo not prominent but inflated, situated a little anterior to middle; auricles lacking; shell surface covered with fineweak concentric ribs and undulations; umbo-

nal area smooth; byssal notch lacking; ligament and adductor muscle impressions unknown.
Measurements (in mm):
Specimen no.
KMSP-5135

H
2.0

L
3.0

T
―

Remarks
LV

Discussion: This species is characterized
by an elongately ovate shell ornamented withweak concentric ribs. In contrast, B. limbata is
suborbicular to transversely oval in outline
and is characterized by broad concentric ribs.
Occurrence: Described specimen from
KC02-03 within the portion of the Novispath­odus ex gr. waageni Zone above the Guodun­
ites horizon of the Owenites koeneni beds
(upper Middle Smithian = middle Lower Olenekian) in the Bac Thuy Formation, northeastern Vietnam.
Order Pterioida Newell, 1965
Superfamily Pterinopectinacea Newell, 1938
Family Pterinopectinidae Newell, 1938
Subfamily Claraiinae Gavrilova, 1996
Genus Crittendenia Newell and Boyd, 1995
Type species: Crittendenia kummeli Newell and Boyd, 1995.
Crittendenia australasiatica(Krumbeck, 1924)
Fig. 137
Pseudomonotis australasiatica Krumbeck, 1924, pl. 8,
figs. 8–10.
Pseudomonotis subconvexa Krumbeck, 1924, pl. 8, fig.
12a, b.
Claraia australasiatica (Krumbeck, 1924). Kiparisova,
1938, pl. 3, figs. 8, 9a, b, 10.
Crittendenia australasiatica (Krumbeck, 1924). Komatsu
and Dang, 2013, figs. 4.1–4.18, 4.24, 4.26–4.28.

Types: Type specimens sketched by Krumbeck (1924, pl. 8, figs. 8–10) from the Lower
Triassic, Timor, Indonesia.
Material examined: Abundant well-preserved left valves and several right valves collected from calcareous nodules and limestone
beds (KMSP-5100–5115, 5122–5124). Over-Olenekian (Early Triassic) in northeastern Vietnam

187

Fig. 137. Crittendenia australasiatica (Krumbeck, 1924). 1, KMSP-5110, from NT01-09, external view of left
valve. 2, Dorsal view of KMSP-5110, umbonal showing imprint of ammonoid (Xenoceltites variocostatus
Brayard and Bucher, 2008). 3, KMSP-5111, from NT01-09, left valve. 4, KMSP-5101, from NT01-09, left
valve, 5, KMSP-5126 (left valve) and KMSP-5122 (right valve), from KC02-08, KMSP-5122 (lower) showing irregular attachment cicatrix on right valve. 6, KMSP-5105, from NT01-04, left valve. 7, KMSP-5127,
from NT01-04, left valve. 8, KMSP-5128, from BR01-04, left valve. 9, KMSP-5116, from NT01-07, right andleft valves, showing anterior auricle of right valve. 10, KMSP-5129, from KC02-06, left valve. 11, KMSP5123, from NT01-04, right valve. 12, KMSP-5114, from NT01-05, right valve. 13, KMSP-5113, from NT0204, modes of occurrence of C. australasiatica and ammonoid shells. 14, Crittendenia langsonensis Komatsu
and Dang, 2013 (small arrow), KMSP-5125, and C. australasiatica (large arrow), KMSP-5108, from NT0107, left valves. 15, KMSP-5123, umbonal area showing imprint of ammonoid (X. variocostatus) umbilicus onright valve. 16, KMSP-5124, from NT01-07, modes of occurrence of C. australasiatica and ammonoid shells.
17, KMSP-5124, umbonal area showing imprint of ammonoid (X. variocostatus) umbilicus on right valve.
Thick scale bars indicate 1 cm. Thin scale bars 5 mm.

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Shigeta, Komatsu, Maekawa and Dang (eds.)

lapping solitary right and left valves found in a
calcareous nodule (KMSP-5116; Fig. 137. 9).
Description: Shell moderate in size forgenus, inequivalve, orbicular or suborbicularin outline; length and height of shells subequal, or height slightly greater than length;
test very thin; hinge line straight and moderately long for genus; strongly convex left
valve, orthocline; anterior wing small without
sinus, posterior wing also small and indistinguishable; ventral margins rounded, umbo
protruded above hinge line, situated mostly
central; umbonal angle about 90 to 120 degrees; shell surface of left valve moderately
smooth except for very weak concentric
growthlines, irregularly faint radial threads,
and ribs occasionally showing growth stop;slightly inflated right valve ornamented withirregularly, very weak radials and growthlines,
posterior wing not differentiated, anterior auricle small for genus, surface of auricle smooth,narrow and moderately deep byssal notch conspicuous; dorsal area of right valve and umbonal area of left valve occasionally imprinted
by the reflecting substrate, for example, anammonoid umbilicus.
Measurements (in mm):
Specimen no.
KMSP-5100
KMSP-5101
KMSP-5102
KMSP-5111
KMSP-5113
KMSP-5114
KMSP-5128

H
33.1
28.9
26.1
29.1
22.4
23.6
12.1+

L
34.4
31.2
26.2
32.0
20.7
22.1
11.2

T
11.8
8.8
8.5
9.5
3.7
4.4
3.1

Remarks
LV
LV
LV
LV
RV
RV
LV

Discussion: Crittendenia australasiatica
has been described as Pseudomonotis austral­
asiatica on the basis of the left valve from theLower Triassic Timor, Indonesia (Krumbeck,1924). Komatsu et al. (2013) recently reported
some well-preserved right and left valves ofthis species from NT01-03 to NT01-07 within
the Xenoceltites variocostatus beds in the Bac
Thuy Formation; they described right valves
and juveniles of this species in detail.
The described specimens show an impor-tant diagnostic characteristic for the genus.
Small attachment imprints are clearly marked
on the umbonal area of the left valve and near
the byssal notch of the right valve (Fig.
137.15–137.17). Some of the imprints of theattachments are coiled impressions of ammonoid umbilicus of Xenoceltites variocostatus(Fig. 137.2, 137.15–137.17). Newell and Boyd
(1995) described Crittendenia kummeli specimens characterized by a coiled negative impression of an ammonoid umbilicus from the
Meekoceras zone of the Thaynes Formation,
northeast Nevada, USA.
Occurrence: Described specimens from
KC02-06, KC02-07 and BR01-01 to BR01-04,
below the Xenoceltites variocostatus beds
(Upper Smithian = upper Lower Olenekian),and those from BT02-05, KC02-10, KC02-11,
NT01-01 to NT01-07, NT01-09 and BR01-05
within the Novispathodus pingdingshanensis
Zone that includes the Xenoceltites vario­
costatus beds and Tirolites cf. cassianus beds,
and those from KC02-12 to KC02-17 within
the Triassospathodus symmetricus Zone that
includes the Tirolites cf. cassianus beds (lowest Lower Spathian = lowest Upper Olenekian)and Tirolites sp. nov. beds (Lower Spathian = lower Upper Olenelian), and those fromBR01-06 and BR01-07 between the Xenocelt­
ites variocostatus beds and Tirolites sp. nov.
beds, and those from BT02-07, BT02-08,
KC02-18, NT01-10 to NT01-12, and BR01-08
within the Tirolites sp. nov. beds in the Bac
Thuy Formation, northeastern Vietnam. This
species also occurs in the Lower Triassic in
Timor, Indonesia (Krumbeck, 1924) and theupper Smithian to lower Spathian on Russky
Island, South Primorye, Russia (Kiparisova,1938).
Crittendenia langsonensis Komatsu andDang, 2013
Figs. 136.8–136.10, 137.14
Crittendenia langsonensis Komatsu and Dang, 2013, figs.
4.19–4.24, 10.

Olenekian (Early Triassic) in northeastern Vietnam

Holotype: Holotype KMSP-5119, figured
by Komatsu and Dang (2013, fig. 4.21) fromNT01-06 within the Xenoceltites variocostatusbeds in the Bac Thuy Formation.
Material examined: Holotype (KMSP5119), paratypes (KMSP-5117, 5118, 5120)
from NT01-04, 07, and 09, and one specimen
from KC02-08.
Descriptions: Shells of average size forgenus, inequivalve and inequilateral, prosocline, suborbicular in outline, slightly longer
than high; test very thin; surface ornamented
with growth lines and irregularly faint threads
and radials occasionally representing growthstop; hinge line moderately long and straight;
left valve inflated, strongly prosogyrous umbo
protruded above hinge line, situated about 1/3
to 2/5 of the way from the anterior margin;umbonal angle about 95 to 105 degrees; obtuse anterior left wing very small without
sinus; posterior left wing inconspicuous, ventral margins rounded; right valve gently convex, non-protruded umbo; right spatulate
small anterior auricle ornamented with fineclear ribs parallel to the anterior auricle end;
byssal sinus; hinge unknown.
Measurements (in mm):
Specimen no.
KMSP-5119
KMSP-5117
KMSP-5120
KMSP-5125

H
27.5+
12.7
8.9
12.1

L
28.6
13.5
9.6
10.9

T
7.8
5.0
3.5
4.9

Remarks
LV (Holotype)
LV (Paratype)
LV (Paratype)
LV

Discussion: Crittendenia langsonensis ischaracterized as a prosocline species and is ornamented with faint radial threads on the left
valve. Prosocline species are not common inthis genus. Olenekian (upper Smithian?/Spathian) C. nammalensis (Nakazawa, 1996) characterized as typical prosocline shells describedby Waterhouse (2000) are reported from theLangpo Member, Gungdang Formation,
Manang, Nepal and the Sungjar Formation,
the Salt Range, Pakistan. However, only poorly preserved C. nammalensis are figured andsketched by Waterhouse (2000).
Occurrence: Described specimens from

189

KC02-08 and NT01-05 to NT01-09 within the
portion of the Novispathodus pingdingshanen­
sis Zone represented by the Xenoceltites vario­
costatus beds (Upper Smithian = upper Lower
Olenekian) in the Bac Thuy Formation, northeastern Vietnam.
Superfamily Pseudomonotoidea Newell, 1938
Family Leptochondriidae Newell and Boyd, 1995
Genus Leptochondria Bittner, 1891
Type species: Pecten (Leptochondria) aeo­
licus Bittner, 1891.
Leptochondria bittneri (Kiparisova, 1938)
Fig. 136.6–136.7
Pseudomonotis cf. multiformis Bittner, 1899, p.10, pl. 2,
figs. 11–14.
Pecten (Velopecten) bittneri Kiparisova, 1938, p. 289, pl.
4, figs. 5–9, 11, 13.

Holotype: Right valve, figured by Kiparisova (1938, p. 289, pl. 4, fig. 13), from theLower Triassic, Russky Island, South Primorye, Russia.
Material examined: Disarticulated left
valves collected from dark gray and greenish
gray laminated shales (KMSP-5136, 5137).
Almost all specimens moderately well preserved.
Description: Left valve moderate in sizefor genus, suborbicular in outline, moderately
inflated; test very thin; dorsal margin short andstraight, ventral margins well rounded, umboslightly projecting above dorsal margin, situated central; anterior and posterior auricles
right-angled to obtuse, indistinctly delimited
from disk; shell surface ornamented with fineradial ribs and concentric lamellae, close-set
radial ribs, intercalating in two or three ranks;
about 15 to 20 first-order ribs slightly prominent, weaker ribs separated by first-order ribs,
first- and second-order ribs rarely bifurcated;concentric fine lamellae irregularly spaced on
marginal ventral surface; hinge and internal
structures unknown, right valve not collected.
Measurements (mm):190
Specimen no.
KMSP-5136
KMSP-5137

Shigeta, Komatsu, Maekawa and Dang (eds.)
H
8.1
10.7

L
8.0
11.1

T
―
―

Remarks
LV
LV

Discussion: The ornamentations of Lepto­
chondria bittneri are more or less variable.
According to Kiparisova (1938, pl. 4, figs.
5–9, 11, 13), the shell surface is irregularly
covered by concentric lamellae and very fineconcentric ribs. Furthermore, the number, sequence, and strength of the radial ribs arequite variable. In addition, third-order radialribs and concentric erect lamellae are notfound on some Russian specimens (e.g. fig. 9,
pl. 4 in Kiparisova, 1938). Vietnamese specimens are similar to specimens of Kiparisova(1938, pl. 4, figs. 5–7).
Leptochondria bittneri resembles L. mini­ma (Kiparisova, 1938) described from the Induan Lazurnaya Formation and Induan to Olenekian (Smithian) Zhitkov Formation by Kiparisova (1938). L. minima is also characterizedby variable shell ornamentations. However,the primary ribs of L. bittneri are much stronger than those of L. minima (Kumagae andNakazawa, 2009). In addition, L. bittneri is
distinguished from L. minima, which is characterized by very fine numerous radial ribs.
Leptochondria cf. bittneri reported fromthe Lower Triassic Daye Formation, Guizhou,
South China, by Gu (1976) and the Guizhou
Bureau of Geology and Mineral Resources(1987) is very similar to L. bittneri. However,
we cannot confirm, because the umbonal areaof the specimen figured by Gu (1976, pl. 29,
fig. 4) is poorly preserved.
Occurrence: Described specimens fromNT01-07 to NT01-09 within the Novispatho­
dus pingdingshanensis Zone represented by
the Xenoceltites variocostatus beds (upper
Smithian = upper Lower Olenekian), and thosefrom KC02-14 within the Triassospathodus
symmetricus Zone represented by the Tirolites
sp. nov. beds (Lower Spathian = lower Upper
Olenekian), and those from BR01-07 between
the Xenoceltites variocostatus beds and Tiro­
lites sp. nov. beds in the Bac Thuy Formation,

northeastern Vietnam. This species also occurs
in the Lower Triassic Tobizin Formation inSouth Primorye, Russia (Bittner, 1899; Kiparisova, 1938).
Conodonts (by T. Maekawa and H. Igo)
Terminology for the orientation of elements has largely been modified by intensive
analysis of multielement reconstruction of
conodont animals (e.g., Purnell et al., 2000).
All specimens described herein are discrete P
elements; hence, the orientation terms proposed by Orchard (1995, 2005) are utilized,
and the superageneric classification proposedby Orchard (2005, 2007a) and Sweet (1988)
has also been adopted.
Institution abbreviation: MPC = Micro­
paleo­n­tology Collection, National Museum of
Nature and Science, Tsukuba.
Order Ozarkodinida Dzik, 1976
Superfamily Gondolelloidea (Lindström, 1970)
Family Gondolellidae Lindström, 1970
Subfamily Mullerinae Orchard, 2005
Genus Conservatella Orchard, 2005
Type species: Ctenognathus conservativa
Müller, 1956.
Conservatella conservativa (Müller, 1956)
Figs. 138–140, 141.1–141.6
Ctenognathus conservativa Müller, 1956, p. 821, pl. 95,
fig. 25.
Neospathodus conservativa (Müller, 1956). Buryi, 1979,
p. 50, pl. 9, fig. 1.
Neospathodus conservativus (Müller, 1956). Sweet et al.,1971, pl. 1, fig. 10; Solien, 1979, p. 303, pl. 3, figs.
5–6.
multielement apparatuses, Conservatella aff. conservativa(Müller, 1956). Orchard, 2005, p. 81, text-fig. 7.
Conservatella conservativa (Müller, 1956). Orchard,
2008, p. 402, figs. 8.20–8.21.

Material examined: Three specimens,
MPC25067–25069, from BT01-03, two specimens, MPC25070, 25071, from BT01-04, one
specimen, MPC25072, from BT01-06, four
specimens, MPC25073–25076 from BT01-07,

Olenekian (Early Triassic) in northeastern Vietnam

191

Fig. 138. Conservatella conservativa (Müller, 1956). 1–4, MPC25067, from BT01-03. 5–7, MPC25068, fromBT01-03. 8–10, MPC25069, from BT01-03. 11–13, MPC25070, from BT01-04. 14–16, MPC25071, fromBT01-04. 17–19, MPC25072, from BT01-06.

192

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 139. Conservatella conservativa (Müller, 1956). 1–3, MPC25073, from BT01-07. 4–6, MPC25074, fromBT01-07. 7–9, MPC25075, from BT01-07. 10–12, MPC25076, from BT01-07. 13–15, MPC25077, fromBT01-10. 16–18, MPC25078, from BT01-10.

Olenekian (Early Triassic) in northeastern Vietnam

193

Fig. 140. Conservatella conservativa (Müller, 1956). 1–3, MPC25079, from BT01-10. 4–6, MPC25080, fromBT01-10. 7–9, MPC25081, from BT01-12. 10–12, MPC25082, from BT01-14. 13–15, MPC25083, fromBT02-01. 16–18, MPC25084, from BT02-01. 19–21, MPC25085, from BT02-02. 22–24, MPC25086, fromBT02-02.

194

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 141. 1–6, Conservatella conservativa (Müller, 1956). 1–3, MPC25087, from BT02-02. 4–6, MPC25088,
from BT03-01. 7–12, Conservatella sp. indet. A. 7–9, MPC25089, from BT01-03. 10–12, MPC25090, fromBT01-04. 13–33, Discretella discreta (Müller, 1956). 13–15, MPC25091, from BT01-03. 16–18, MPC25092,
from BT01-03. 19–21, MPC25093, from BT01-03. 22–24, MPC25094, from BT01-04. 25–27, MPC25095,
from BT01-06. 28–30, MPC25096, from BT01-06. 31–33, MPC25097, from BT01-06.

Olenekian (Early Triassic) in northeastern Vietnam

four specimens, MPC25077–25080, fromBT01-10, one specimen, MPC25081, fromBT01-12, one specimen, MPC25082, fromBT01-14, two specimens, MPC25083, 25084,
from BT02-01, three specimens, MPC25085–
25087, from BT02-02, and one specimen,
MPC25088, from BT03-01.
Description: Laterally compressed, rectangular or rhombic segminate elements 0.59–
1.26 mm in length, average 0.85 mm; 0.31–
0.85 mm in height, average 0.49 mm; length toheight ratio 1.2–2.2, average 1.7 for twentytwo specimens. Pointed spine-like denticles
vary in number from 7 to 14, average 11,
straight or slightly reclined posteriorly, discrete in upper two-thirds, fused in lower onethird. Basal margin straight or slightly upturned in anterior and upturned 5–40 degrees,
average 18 degrees at middle to one-third posterior margin. Triangular, non-expanded, flator slightly convex basal cavity posteriorly extended. Anterior groove continues to posterior
end. Some elements curved left or right side
posteriorly.
Remarks: The Bac Thuy Formation includes many well preserved specimens ofConservatella conservativa (Müller, 1956)
that exhibit denticles and a groove at different
growth stages. The length of the denticule andthe upturned position of the basal part of theelement are variable, but they share somecommon features including slightly fused denticles and a non-expanded and non-concave
basal cavity, features that are recognized onlyin
thisspecies.
Smaller
specimens(MPC25068–25071, 25078, etc.), in contrast
to larger ones with typical form (MPC25067,
25072–25076, etc.), are probably juveniles,
and have fused short denticles. These features
are different from juvenile specimens of Dis­cretella discreta (Müller, 1956), whose denticles are more discrete and fewer in number.
Occurrence: Described specimens fromBT01-03, BT01-04, BT01-06, BT01-07,
BT01-10, BT01-12, BT01-14, BT02-01,
BT02-02 and BT03-01 within the portion of

195

the Novispathodus ex gr. waageni Zone that
includes the Flemingites rursiradiatus beds
(lowest Middle Smithian = middle Lower Olenekian), Urdyceras tulongensis beds (lower
Middle Smithian = middle Lower Olenekian)and Leyeceras horizon of the Owenites koene­ni beds (middle Middle Smithian = middle
Lower Olenekian) in the Bac Thuy Formation,
northeastern Vietnam. This species also occurs
in the Middle Smithian in Nevada (Meekoc­
eras beds, Müller, 1956; Sweet et al., 1971),
Utah (Furnishius Zone to Parachirognathus
Zone, Solien, 1979), South Primorye, Russia(Parachirognathus-Furnishius Zone, Buryi,1979), Jabra Safra, Oman (Orchard, 2005),
and Canadian Arctic (Euflemingites romunderi
Zone, Orchard, 2008).
Conservatella sp. indet. A
Fig. 141.7–141.12

Material examined: One specimen,
MPC25089, from BT01-03, and one specimen, MPC25090, from BT01-04.
Description: Two laterally compressedsegminate elements 0.61–0.84 mm in length;0.39–0.52 mm in height; length to height ratio
1.6. Strongly reclined and fused denticles total
13 and 14 in number. Cusp situated at middle
to posterior part with two posterior small denticles. Basal margin straight in anterior andslightly upturned in posterior. Non-expandedbasal cavity extended posteriorly. Anterior
shallow groove extends to basal pit.
Remarks: The laterally compressed element with fused denticles suggests that the described specimens belong to the genus Con­
servatella. However, their extremely reclined
and fused denticles are different from those of
the type species of the genus, C. conservativa(Müller, 1956). They probably represent an
unknown species of Conservatella.
Occurrence: Described specimens fromBT01-03 and BT01-04 within the portion of
the Novispathodus ex gr. waageni Zone represented by the Flemingites rursiradiatus beds

196

Shigeta, Komatsu, Maekawa and Dang (eds.)(lowest Middle Smithian = middle Lower Olenekian) in the Bac Thuy Formation, northeastern Vietnam.
Genus Discretella Orchard, 2005
Type species: Ctenognathus discreta Müller, 1956.
Discretella discreta (Müller, 1956)
Figs. 141.13–141.33, 142–145, 146.1–146.30
Ctenognathus discreta Müller, 1956, p. 821, pl. 95, fig. 28.
Neospathodus conservativus (Müller, 1956). Koike, 1982,
p. 36, pl. 6, figs. 12–14.
Neospathodus discretus (Müller, 1956). Tian et al., 1983,
p. 376, pl. 95, fig. 1.
Neospathodus aff. cristagalli (Huckriede, 1958). Bui,
1989, p. 404, pl. 30, fig. 1.
multielement apparatuses, Discretella sp. A, Orchard,
2005, p. 83, text-fig. 8.
Discretella discreta (Müller, 1956). Orchard, 2008, p. 402,
figs. 8.18–8.19; Beranek et al., 2010, figs. 6.18, 6.19.

Material examined: Three specimens,
MPC25091–25093, from BT01-03, one specimen, MPC25094, from BT01-04, three specimens, MPC25095–25097, from BT01-06, four
specimens, MPC25098–25101, from BT0107, five specimens, MPC25102–25106, fromBT01-10, one specimen, MPC25107, fromBT01-12, two specimens, MPC25108, 25109,
from BT01-14, seven specimens, MPC25110–
25116, from BT02-01, four specimens,
MPC25117–25120 from BT02-02, one specimen, MPC25121, from BT02-03, two specimens, MPC25122, 25123, from BT03-01, one
specimen, MPC25124, from KC01-01, three
specimens, MPC25125–25127, from KC0104, two specimens, MPC25128, 25129, from
KC01-05, four specimens, MPC25130-25133,
from KC01-11, four specimens, MPC25134–
25137, from KC01-12, two specimens,
MPC25138, 25139, from KC01-13, one specimen, MPC25140, from KC02-02, and two
specimens, MPC25141, 25142, from PK0102.
Description: Long and slender segminate
elements 0.35–1.36 mm in length, average

0.77 mm; 0.27–0.72 mm in height, average
0.42 mm; length to height ratio 1.1–2.4, average 1.7 for fifty-two specimens. General profile of element rectangular, highest point situated at posterior one-third to posterior margin.
Lower margin of element almost straight toslightly undulated and posterior part upturnedin some specimens. Discrete denticles vary innumber from 4 to 13, average 8, sub-erect orreclined posteriorly. Cusp situated above basal
cavity and bears one to three small denticles atposterior end. Sub-rounded and posteriorly
elongated basal cavity with a thin pit. Anteriorgroove continues to posterior end.
Remarks: The Bac Thuy Formation includes many well preserved specimens of Dis­cretella discreta (Müller, 1956), and two morphotypes (A and B) are also recognized. Morphotype A (MPC25097, 25101, 25103, etc.) ischaracterized by a higher cusp with two or
three small posterior denticles and a roundedbasal cavity. The posterior part of the lower
margin is downturned. Morphotype A is identical to the typical form of D. discreta described by Müller (1956) from Nevada. Morphotype B (MPC25095, 25096, 25100, etc.)
can be distinguished by its triangular larger
denticle and upturned posterior margin.
Occurrence: Described specimens fromBT01-03, BT01-04, BT01-06, BT01-07,
BT01-10, BT01-12, BT01-14, BT02-01,
BT02-02, BT02-03, BT03-01, KC01-01,
KC01-04, KC01-05, KC01-11, KC01-12,
KC01-13, KC02-02 and PK01-02 within the
portion of the Novispathodus ex gr. waageni
Zone that includes the Flemingites rursiradia­
tus beds (lowest Middle Smithian =middle Lower Olenekian), Urdyceras tulon­
gensis beds (lower Middle Smithian = middle
Lower Olenekian) and Owenites koeneni beds
(middle Middle Smithian = middle Lower Olenekian) in the Bac Thuy Formation, northeastern Vietnam. This species also occurs in the
Middle Smithian in Nevada (Meekoceras
beds, Müller, 1956), Gunong Keriang, West
Malaysia (Koike, 1982), Tibet (Tian et al.,

Olenekian (Early Triassic) in northeastern Vietnam

197

Fig. 142. Discretella discreta (Müller, 1956). 1–3, MPC25098, from BT01-07. 4–6, MPC25099, from BT01-07.
7–9, MPC25100, from BT01-07. 10–12, MPC25101, from BT01-07. 13–15, MPC25102, from BT01-10. 16–
18, MPC25103, from BT01-10. 19–21, MPC25104, from BT01-10. 22–24, MPC25105, from BT01-10.

198

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 143. Discretella discreta (Müller, 1956). 1–3, MPC25106, from BT01-10. 4–6, MPC25107, from BT01-12.
7–9, MPC25108, from BT01-14. 10–12, MPC25109, from BT01-14. 13–15, MPC25110, from BT02-01. 16–
17, MPC25111, from BT02-01. 18–20, MPC25112, from BT02-01. 21–23, MPC25113, from BT02-01. 24–
26, MPC25114, from BT02-01. 27–29, MPC25115, from BT02-01. 30–32, MPC25116, from BT02-01. 33–
35, MPC25117, from BT02-02.

Olenekian (Early Triassic) in northeastern Vietnam

199

Fig. 144. Discretella discreta (Müller, 1956). 1–3, MPC25118, from BT02-02. 4–6, MPC25119, from BT02-02.
7–9, MPC25120, from BT02-02. 10–12, MPC25121, from BT02-03. 13–15, MPC25122, from BT03-01. 16–
18, MPC25123, from BT03-01. 19–21, MPC25124, from KC01-01. 22–24, MPC25125, from KC01-04. 25–
27, MPC25126, from KC01-04.

200

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 145. Discretella discreta (Müller, 1956). 1–3, MPC25127, from KC01-04. 4–6, MPC25128, from KC01-05.
7–9, MPC25129, from KC01-05. 10–12, MPC25130, from KC01-11. 13–15, MPC25131, from KC01-11. 16–
18, MPC25132, from KC01-11.

Olenekian (Early Triassic) in northeastern Vietnam

201

Fig. 146. 1–30, Discretella discreta (Müller, 1956). 1–3, MPC25133, from KC01-11. 4–6, MPC25134, from
KC01-12. 7–9, MPC25135, from KC01-12. 10–12, MPC25136, from KC01-12. 13–15, MPC25137, from
KC01-12. 16–18, MPC25138, from KC01-13. 19–21, MPC25139, from KC01-13. 22–24, MPC25140, from
KC02-02. 25–27, MPC25141, from PK01-02. 28–30, MPC21542, from PK01-02. 31–33, Discretella robustus(Wang and Wang, 1976), MPC25143, from BT01-03.

202

Shigeta, Komatsu, Maekawa and Dang (eds.)

1983), Jabal Safra, Oman (Orchard, 2005),
British Columbia, Canada (Beranek et al,2010), and Canadian Arctic (Euflemingites ro­munderi Zone, Orchard, 2008).
Discretella robustus (Wang and Wang, 1976)
Figs. 146.31–146.33, 147–150?Ctenognathus discreta Müller, 1956, p. 821, pl. 95, fig.
24.
Cratognathodus robustus Wang and Wang, 1976, p. 397,
pl. 3, figs. 21–25.
Cratognathodus robustus Wang and Z. H. Wang, 1976.
Tian et al., 1983, p. 347, pl. 88, figs. 8, 9.
Neospathodus discreta (Müller, 1956). Buryi, 1979, p. 52,
pl. 7, figs. 2–6.
Guangxidella? robustus (Wang and Wang, 1976). Orchard, 2007a, fig. 1.

Material examined: Two specimens,
MPC25143, 25144, from BT01-03, four specimens, MPC25145–25148, from BT01-04, six
specimens, MPC25149–25154, from BT0106, one specimen, MPC25155, from BT01-07,
four specimens, MPC25156–25159, fromBT01-10, one specimen, MPC25160, fromBT01-12, five specimens, MPC25161–25165,
from BT01-14, four specimens, MPC25166–
25169, from BT01-15, two specimens,
MPC25170, 25171, from BT02-01, eight specimens, MPC25172–25179, from BT02-02,
two specimens, MPC25180, 25181, fromBT02-03, two specimens, MPC25182, 25183,
from KC01-01, two specimens, MPC25184,
25185, from KC01-10, and one specimen,
MPC25186, from KC02-03.
Description: Segminate elements 0.43–
1.69 mm in length, average 0.64 mm; 0.26–
0.91 mm in height, average 0.41 mm; length toheight ratio 1.0–2.4, average 1.6 for forty-four
specimens. General profile of element triangular or trapezoidal, highest point situated at
posterior one-third to posterior margin. Lower
margin of element almost straight, posterior
part downturned in those specimens whose
lower margins are bowed. Almost discrete
denticles vary in number from 4 to 13, average8, sub-erect or gradually reclined posteriorly.

Cusp longer and two times larger than otherdenticles, bears one to 4 small denticles atposterior end. Element shows sigmoidal shapein lower view. Flared basal cavity sub-rounded
and concave with a thin pit. Anterior groovecontinues to posterior end.
Remarks: Typical elements of Discretellarobustus (Wang and Wang, 1976) have astrongly reclined large posterior cusp with twoor three small posterior denticles, exhibits asigmoidal shape in the lower view, and differsfrom those of typical D. discreta (Müller,
1956). Ctenognathus discreta (Müller, 1956,
pl. 98, fig. 24) is somewhat similar to D. ro­bustus, but it is questionable whether they areconspecific because the cusp of C. discreta is
broken and the lower view is not illustrated.
Occurrence: Described specimens fromBT01-03, BT01-04, BT01-06, BT01-07,
BT01-10, BT01-12, BT01-14, BT01-15,
BT02-01, BT02-01, BT02-03, KC01-01,
KC01-10 and KC02-03 within the portion of
the Novispathodus ex gr. waageni Zone that
includes the Flemingites rursiradiatus beds
(lowest Middle Smithian = middle Lower Olenekian), Urdyceras tulongensis beds (lower
Middle Smithian = middle Lower Olenekian)and Owenites koeneni beds (middle Middle
Smithian = middle Lower Olenekian) in the
Bac Thuy Formation, northeastern Vietnam.
This species also occurs in the Middle Smithian in Nevada (Meekoceras beds, Müller,
1956), Qomolangma, Tibet (Wang and Wang,
1976; Tian et al., 1983), and South Primorye,
Russia (Parachirognathus-Furnishius Zone,
Buryi, 1979).
Discretella sp. indet. A
Fig. 151.1–151.18
Discretella discreta (Müller, 1956). Bondarenko et al.,2013, p. 60, figs. 7.1, 7.2.

Material examined: Two specimens,
MPC25187, 25188, from BT02-02, one specimen, MPC25189, from KC01-10, two specimens, MPC25190, 25191, from KC02-02, andOlenekian (Early Triassic) in northeastern Vietnam

203

Fig. 147. Discretella robustus (Wang and Wang, 1976). 1–3, MPC25144, from BT01-03. 4–6, MPC25145, fromBT01-04. 7–9, MPC25146, from BT01-04. 10–12, MPC25147, from BT01-04. 13–15, MPC25148, fromBT01-04. 16–18, MPC25149, from BT01-06. 19–21, MPC25150, from BT01-06. 22–24, MPC25151, fromBT01-06. 25–27, MPC25152, from BT01-06. 28–30, MPC25153, from BT01-06. 31–33, MPC25154, fromBT01-06.

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 148. Discretella robustus (Wang and Wang, 1976). 1–3, MPC25155, from BT01-07. 4–6, MPC25156, fromBT01-10. 7–9, MPC25157, from BT01-10. 10–12, MPC25158, from BT01-10. 13–15, MPC25159, fromBT01-10. 16–18, MPC25160, from BT01-12. 19–21, MPC25161, from BT01-14. 22–24, MPC25162, fromBT01-14. 25–27, MPC25163, from BT01-14. 28–30, MPC25164, from BT01-14. 31, MPC25165, fromBT01-14. 32, MPC25166, from BT01-15. 33–35, MPC25167, from BT01-15. 36–38, MPC25168, fromBT01-15. 39–41, MPC25169, from BT01-15.

Olenekian (Early Triassic) in northeastern Vietnam

205

Fig. 149. Discretella robustus (Wang and Wang, 1976). 1–3, MPC25170, from BT02-01. 4–6, MPC25171, fromBT02-01. 7–9, MPC25172, from BT02-02. 10–12, MPC25173, from BT02-02. 13–15, MPC25174, fromBT02-02. 16–18, MPC25175, from BT02-02. 19–21, MPC25176, from BT02-02. 22–24, MPC25177, fromBT02-02. 25–27, MPC25178, from BT02-02.

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 150. Discretella robustus (Wang and Wang, 1976). 1–3, MPC25179, from BT02-02. 4–6, MPC25180, fromBT02-03. 7–9, MPC25181, from BT02-03. 10–12, MPC25182, from KC01-01. 13–15, MPC25183, from
KC01-01. 16–18, MPC25184, from KC01-10. 19–21, MPC25185, from KC01-10. 22–24, MPC25186, from
KC02-03.

Olenekian (Early Triassic) in northeastern Vietnam

one specimen, MPC25192, from KC02-03.
Description: Triangular segminate elements 0.43–0.73 mm in length, average
0.57 mm; 0.31–0.58 mm in height, average
0.49 mm; length to height ratio 0.7–1.4, average 1.2 for six specimens. Discrete, triangulardenticles vary in number from 3 to 5, average
4, revealing showing gradual size increase
posteriorly. Largest denticle twice the size ofothers, and strongly inclined posteriorly.
Small, triangular marginal process situated at
posterior end. Lower margin generally straightor weakly upturned in anterior part, and downturned or slightly deflected upward in posterior part. Element exhibits sigmoidal shape inlower view. Sub-rounded basal cavity elongated posteriorly. Shallow furrow extends frombasal pit to anterior end.
Remarks: The described specimens are triangular in lateral view and sigmoidal in lower
view. These features indicate a close phylogenetic relationship with Discretella robustus(Wang and Wang, 1976). The first appearanceof D. sp. indet. A occurs higher than that of D.
robustus in the Bac Thuy Formation. This evidence suggests that D. sp. A probably evolved
from D. robustus during early Middle Smithian time.
The number of denticles on the described
specimens apparently decreases with youngeraged taxa. Specimens from the Urdyceras tu­
longensis beds have five denticles, but thosefrom the Owenites koeneni beds bear only four
denticles. The size of the cusp also gradually
increases in younger-aged taxa.
Specimens described as Discretella discre­ta (Müller, 1956) from South Primorye, Russia
by Bondarenko et al. (2013, p. 60, Fig. 7.1,
7.2) are identical to D. sp. indet. A.
Occurrence: Described specimens fromBT02-02, KC01-10, KC02-02 and KC02-03
within the portion of the Novispathodus ex gr.
waageni Zone that includes the Urdyceras tu­
longensis beds (lower Middle Smithian = middle Lower Olenekian) and the Leyeceras andthe Guodunites horizons of the Owenites koen­

207

eni beds (middle to upper Middle Smithian = middle Lower Olenekian) in the Bac Thuy
Formation, northeastern Vietnam. This species
also occurs in the Anasibirites nevolini Zone
(Upper Smithian) in South Primorye, Russia(Bondarenko et al., 2013).
Discretella sp. indet. B
Fig. 151.19–151.24

Material examined: Two specimens,
MPC25193, 25194, from BT01-03.
Description: Two laterally compressedsegminate elements 0.53–0.56 mm in length;0.32–0.36 mm in height; length to height ratio
1.6–1.7. Laterally compressed, erect spine-likedenticles total 9 and 11 in number. Cusp situated in middle part of element. Denticle size
gradually decreases both anteriorly and posteiorly. Basal margin shows biangular shape inlateral view. Anterior part of elements appears
sigmoidal or straight in lower view. Basal cavity sub-rounded and elongated posteriorly.
Shallow groove extends from basal pit to anterior end.
Remarks: Described specimens have completely discrete denticles and a sub-roundedbasal cavity. These features are common in
Discretella discreta (Müller, 1956). However,the biangular lateral shape of the element issimilar to that of Conservatella conservativa(Müller, 1956). Thus, this feature indicatesthat these specimens are probably ancestoral
to C. conservativa.
Occurrence: Described specimens fromBT01-03 within the portion of the Novispatho­
dus ex gr. waageni Zone in the Flemingites
rursiradiatus beds (lowest Middle Smithian = middle Lower Olenekian) in the Bac Thuy
Formation, northeastern Vietnam.
Discretella sp. indet. C
Fig. 151.25–151.28

Material examined: One specimen,
MPC25195, from BT01-07.
Description: Anterior branched segminate

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Fig. 151. 1–18, Discretella sp. indet. A. 1–3, MPC25187, from BT02-02. 4–6, MPC25188, from BT02-02. 7–9,
MPC25189, from KC01-10. 10–12, MPC25190, from KC02-02. 13–15, MPC25191, from KC02-02. 16–18,
MPC25192, from KC02-03. 19–24, Discretella sp. indet. B from BT01-03. 19–21, MPC25193. 22–24,
MPC25194. 25–28, Discretella sp. indet. C, MPC25195, from BT01-07.

Olenekian (Early Triassic) in northeastern Vietnam

element 1.23 mm in length; 0.68 mm in height;
length to height ratio 1.8. Upper edge consistsof node-like robust discrete denticles, withcusp situated in one-third of anterior and posterior (posterior cusp lost). Denticles total 11
in number, including two small, barely remaining posterior denticles. Denticle size decreases from cusp anteriorly and posteriorly,
and same in middle part. Lower margin
straight. Prominent lateral rib developed. Anterior margin turns 60 degrees to the left inupper view. Branch cusp extends in parallelwith anterior margin from left side of anterior
one-third, and then turns anteriorly in upper
view. Rounded basal cavity situated in posterior with a deep pit in lower view. Broad, deep
furrow extends anteriorly and branched at anterior one-third.
Remarks: The discrete denticles, including
the small posterior ones and the rounded basal
cavity suggest that the described specimen belongs to the genus Discretella, but no definitive assignment can be made.
Occurrence: Specimen from BT01-07
within the portion of the Novispathodus ex gr.
waageni Zone between the Flemingites rursiradiatus beds (lowest Middle Smithian = middle Lower Olenekian) and Urdyceras tulongensis beds (lower Middle Smithian = middle
Lower Olenekian) in the Bac Thuy Formation,
northeastern Vietnam.
Discretella sp. indet. D
Fig. 152.1–152.6

Material examined: Two specimens,
MPC25196, 25197, from BT01-07.
Description: Two segminate elements 1.0–
1.36 mm in length; 0.51–0.67 mm in height;
length to height ratio 2.0. General profile of element triangular, slightly bowed lower edge.
Upper edge bears several pointed denticles, including one larger posterior cusp with one or
two small processes. Cusp three times larger
than other denticles, with two pronged ends.
Denticles total 9 in number. Lower edge

209

straight in anterior, downturned in posterior
below cusp. Aboral surface broad with rounded basal cavity below cusp. Groove extended
to both anterior and posterior ends throughbasal pit.
Remarks: The described specimens differ
from other species of Discretella in having
two pronged cusps and an arched basal margin. However, a definitive species assignment
cannot be made due to an insufficient numberof specimens. Their lateral profiles are somewhat similar to that of Guangxidella bransoni(Müller, 1956), except for the small posterior
processes.
Occurrence: Described specimens fromBT01-07 within the portion of the Novispathodus ex gr. waageni Zone between the Flemingites rursiradiatus beds (lowest Middle Smithian = middle Lower Olenekian) and Urdycerastulongensis beds (lower Middle Smithian = middle Lower Olenekian) in the Bac Thuy
Formation, northeastern Vietnam.
Discretella sp. indet. E
Fig. 152.7–152.9

Material examined: One specimen,
MPC25198, from BT01-10.
Remarks: The described specimen lacks
the anterior part, but it differs from other species of Discretella in having a rectangularshaped element, small pole-like denticles, anda triangular shaped posterior cusp.
Occurrence: Specimen from BT01-10
within the portion of the Novispathodus ex gr.
waageni Zone between the Urdyceras tulongensis beds (lower Middle Smithian = middle
Lower Olenekian) and Leyceras horizon of theOwenites koeneni beds (middle Middle Smithian = middle Lower Olenekian) in the Bac
Thuy Formation, northeastern Vietnam.
Discretella sp. indet. F
Fig. 152.10–152.12

Material examined: One
MPC25199, from BT01-15.

specimen,

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Fig. 152. 1–6, Discretella sp. indet. D from BT01-07. 1–3, MPC25196. 4–6, MPC25197. 7–9, Discretella sp.
indet. E, MPC25198, from BT01-10. 10–12, Discretella sp. indet. F, MPC25199, from BT01-15. 13–15, Discretella sp. indet. G, MPC25200, from KC02-02. 16–18, Guangxidella bransoni (Müller, 1956), MPC25201,
from BT01-06.

Olenekian (Early Triassic) in northeastern Vietnam

Remarks: The lateral profile of this specimen is similar to that of Discretella robustus(Wang and Wang, 1976), but it differs by having a space in front of the cusp and a non-expanded basal cavity.
Occurrence: Specimen from BT01-15
within the portion of the Novispathodus ex gr.
waageni Zone above the Leyeceras horizon of
the Owenites koeneni beds (middle Middle
Smithian = middle Lower Olenekian) in the
Bac Thuy Formation, northeastern Vietnam.
Discretella sp. indet. G
Fig. 152.13–152.15

Material examined: One specimen,
MPC25200, from KC02-02.
Description: Laterally compressed segminate element 0.63 mm in length; 0.44 mm
height; length to height ratio 1.4. Erect denticles total 6 in number. Lower margin upturnedin anterior two-thirds and posterior one-third.
Rounded basal cavity slightly wider than thewidth of element. Shallow groove extends
from basal pit to anterior end.
Remarks: The described specimen is distinguished from other species of Discretella by
the strongly upturned anterior lower margin,
straight denticles and small basal cavity.
Occurrence: Described specimen from
KC02-02 within the portion of the Novispathodus ex gr. waageni Zone represented by the
Guodunites horizon of the Owenites koeneni
beds (upper Middle Smithian = middle Lower
Olenekian) in the Bac Thuy Formation, northeastern Vietnam.
Genus Gunagxidella Zhang and Yang, 1991
Type species: Neoprioniodus bransoni
Müller, 1956.
Guangxidella bransoni (Müller, 1956)
Figs. 152.16–125.18, 153–159, 160.1–160.4
Neoprioniodus bransoni Müller, 1956, p. 829, pl. 95, figs.
19–21.
Neoprioniodus bicuspidatus Müller, 1956, p. 828, pl. 95,

211

figs. 16–17.
Neospathodus bicuspidatus (Müller, 1956). Solien, 1979,
p. 302, pl. 3, figs. 2–3.
Ozarkordina gigantea Bui, 1989, p. 409, pl. 31, figs. 10,
14.
multielement apparatuses, Guangxidella typica Zhang andYang, 1991, p. 33, pl. 1, figs. 1a-b, 2a-b.

Material examined: Three specimens,
MPC25201–25203, from BT01-06, four specimens, MPC25204–25207, from BT01-10, two
specimens, MPC25208, 25209, from BT0114, seven specimens, MPC25210–25216, fromBT01-15, six specimens, MPC25217–25222,
from BT02-02, ten specimens, MPC25223–
25232, from BT02-03, eight specimens,
MPC25233–25240, from BT03-01, six specimens, MPC25241–25246, from KC01-07, two
specimens, MPC25247, 25248, from KC0110, and nine specimens, MPC25249–25257,
from PK01-02.
Description: Bowed segminate elements
0.43–1.45 mm in length, average 0.76 mm;
0.25–0.78 mm in height, average 0.40 mm;
length to height ratio 1.3–2.6, average 1.9 forfifty-seven specimens. Bowed carina bears
pointed denticles in upper part and more orless in concave lower part. Spine and nodelike denticles vary in number from 5 to 12, average 8. Most denticles almost entirely discrete in small specimens, but fused over halfof the length in large specimens. Denticle size
increases posteriorly. Cusp situated in posterior end, and is two to three times larger thanothers. Sub-rounded or rectangular, cordiformlike basal cavity branches at posterior end.
Width of basal cavity two times width of element. Deep furrow extends from basal pit toanterior end.
Remarks: The described specimens show awide range of intraspecific variation in theform of denticles and basal cavity. However,all specimens share features characterized by
the bow-like lateral form and cusp situated in
the posterior end. They also include forms(MPC25202, 25211, 25214, etc.) that are very
similar to the holotype of Guangxidella bran-

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Fig. 153. Guangxidella bransoni (Müller, 1956). 1–3, MPC25202, from BT01-06. 4–6, MPC25203, from BT0106. 7–9, MPC25204, from BT01-10. 10–12, MPC25205, from BT01-10. 13–15, MPC25206, from BT01-10.
16–18, MPC25207, from BT01-10.

Olenekian (Early Triassic) in northeastern Vietnam

213

Fig. 154. Guangxidella bransoni (Müller, 1956). 1–3, MPC25208, from BT01-14. 4–6, MPC25209, from BT0114. 7–9, MPC25210, from BT01-15. 10–12, MPC25211, from BT01-15. 13–15, MPC25212, from BT01-15.
16–18, MPC25213, from BT01-15. 19–21, MPC25214, from BT01-15.

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Fig. 155. Guangxidella bransoni (Müller, 1956). 1–3, MPC25215, from BT01-15. 4–6, MPC25216, from BT0115. 7–9, MPC25217, from BT02-02. 10–12, MPC25218, from BT02-02. 13–15, MPC25219, from BT02-02.
16–18, MPC25220, from BT02-02. 19–21, MPC25221, from BT02-02. 22–24, MPC25222, from BT02-02.

Olenekian (Early Triassic) in northeastern Vietnam

215

Fig. 156. Guangxidella bransoni (Müller, 1956) from BT02-03. 1–3, MPC25223. 4–6, MPC25224. 7–9,
MPC25225. 10–12, MPC25226. 13–15, MPC25227. 16–18, MPC25228. 19–21, MPC25229. 22–24,
MPC25230. 25–27, MPC23231.

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Fig. 157. Guangxidella bransoni (Müller, 1956). 1–3, MPC25232, from BT02-03. 4–6, MPC25233, from BT0301. 7–9, MPC25234, from BT03-01. 10–12, MPC25235, from BT03-01. 13–15, MPC25236, from BT03-01.
16–18, MPC25237, from BT03-01. 19–21, MPC25238, from BT03-01. 22–24, MPC25239, from BT03-01.
25–27, MPC25240, from BT03-01.

Olenekian (Early Triassic) in northeastern Vietnam

217

Fig. 158. Guangxidella bransoni (Müller, 1956). 1–3, MPC25241, from KC01-07. 4–6, MPC25242, from KC0107. 7–9, MPC25243, from KC01-07. 10–12, MPC25244, from KC01-07. 13–15, MPC25245, from KC01-07.
16–18, MPC25246, from KC01-07. 19–21, MPC25247, from KC01-10.

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Fig. 159. Guangxidella bransoni (Müller, 1956). 1–3, MPC25248, from KC01-10. 4–7, MPC25249, from PK0102. 8–11, MPC25250, from PK01-02. 12–15, MPC25251, from PK01-02. 16–19, MPC25252, from PK01-02.
20–23, MPC25253, from PK01-02. 24–26, MPC25254, from PK01-02. 27–29, MPC25255, from PK01-02.
30–32, MPC25256, from PK01-02.

Olenekian (Early Triassic) in northeastern Vietnam

219

Fig. 160. 1–4, Guangxidella bransoni (Müller, 1956), MPC25257, from PK01-02. 5–10, Guangxidella sp. indet.
A from BT01-06. 5–7, MPC25258. 8–10, MPC25259. 11–16, Guangxidella sp. indet. B. 11–13, MPC25260,
from BT02-02. 14–16, MPC25261, from KC01-07.

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soni (Müller, 1956, pl. 95, figs. 20, 21).
Occurrence: Described specimens fromBT01-06, BT01-10, BT01-14, BT01-15,
BT02-02, BT02-03, BT03-01, KC01-07,
KC01-10 and PK01-02 within the portion of
the Novispathodus ex gr. waageni Zone that
includes the Urdyceras tulongensis beds
(lower Middle Smithian = middle Lower Olenekian) and the Leyeceras horizon of theOwenites koeneni beds (middle Middle Smithian = middle Lower Olenekian) in the Bac
Thuy Formation, northeastern Vietnam. This
species also occurs in the Middle Smithian at
Crittenden Springs, Nevada (Meekoceras
beds, Müller, 1956), the Luolou Formation,
Guangxi, China (Neospathodus waageni Zone,
Zhang and Yang, 1991), the Thaynes Formation, Utah (Parachirognathus Zone, Solien,1979) and the Taho limestone, Southwest
Japan (unpublished).
Guangxidella sp. indet. A
Fig. 160.5–160.10

Material examined: Two specimens,
MPC25258, 25259, from BT01-06.
Description: Two triangular segminate elements 0.76 mm in length; 0.54–0.56 mm inheight; length to height ratio 1.4. Robust denticles total 4 and 5 in number, reclined posteriorly. Cusp situated in posterior end, threetimes larger than other denticles. Roundedbasal cavity expanded in posterior end. Shallow groove extends from basal pit to anterior
end.
Remarks: The described specimens arevery similar to the juvenile form of Guangxidella bransoni (Müller, 1956), but differ inhaving a larger element size, robust denticles
and a rounded basal cavity.
Occurrence: Described specimens fromBT01-06 within the portion of the Novispathodus ex gr. waageni Zone between the Flemingites rursiradiatus beds (lowest Middle Smithian = middle Lower Olenekian) and Urdycerastulongensis beds (lower Middle Smithi-

an = middle Lower Olenekian) in the Bac Thuy
Formation, northeastern Vietnam.
Guangxidella sp. indet. B
Figs. 160.11–160.16, 161.1–161.3

Material examined: One specimen,
MPC25260, from BT02-02, one specimen,
MPC25261, from KC01-07, and one specimen
MPC25262, from KC01-11.
Description: Three triangular segminate
elements 0.63–0.84 mm in length, average
0.77 mm; 0.43–0.55 mm in height, average
0.50 mm; length to height ratio 1.5–1.6. Lower
margin slightly concave and down-turned posteriorly. Completely discrete and pointed denticles total 5 to 6 in number. Denticle size andinclination gradually increases posteriorly.
Cusp situated in posterior end. Sub-roundedbasal cavity extends posteriorly. Shallow furrow runs from basal pit to anterior end.
Remarks: The described specimens differ
from Guangxidella bransoni (Müller, 1956) byslightly bowed elements with quite discrete
denticles and non-branched basal cavity, andfrom Guangxidella sp. indet. A. by a smaller
basal cavity and slender lateral form.
Occurrence: Described specimens fromBT02-02, KC01-07 and KC01-11 within the
portion of the Novispathodus ex gr. waageni
Zone that includes the Urdyceras tulongensis
beds (lower Middle Smithian = middle Lower
Olenekian) and the Leyeceras horizon of theOwenites koeneni beds (middle Middle Smithian = middle Lower Olenekian) in the Bac
Thuy Formation, northeastern Vietnam.
Subfamily Neogondolellinae Hirsch, 1994
Genus Eurygnathodus Staesche, 1964
Type species: Eurygnathodus costatus
Staesche, 1964.
Eurygnathodus costatus Staesche, 1964
Fig. 161.4–161.6
Eurygnathodus costatus Staesche, 1964, p. 269, pl. 28,
figs. 1–6; Budurov and Pantic, 1973, p. 51, pl. pl. 1,

Olenekian (Early Triassic) in northeastern Vietnam

221

Fig. 161. 1–3, Guangxidella sp. indet. B, MPC25262, from KC01-11. 4–6, Eurygnathodus costatus Staesche,
1964, MPC25263, from BT01-03. 7–9, Neospathodus aff. concavus Zhao and Orchard, 2007, MPC25264,
from BT01-07. 10–12, Neospathodus cristagalli (Huckriede, 1958), MPC25265, from BT01-04. 13–45, Neospathodus dieneri Sweet, 1970a. 13–15, MPC25266, from BT01-04. 16–18, MPC25267, from BT01-07. 19–
21, MPC25268, from BT01-07. 22–24, MPC25269, from BT02-02. 25–27, MPC25270, from KC01-01. 28–
30, MPC25271, from KC01-13. 31–33, MPC25272, from KC01-13. 34–36, MPC25273, from KC01-13. 37–
39, MPC25274, from KC02-02. 40–42, MPC25275, from KC02-02. 43–45, MPC25276, from KC02-02.

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Shigeta, Komatsu, Maekawa and Dang (eds.)

figs. 1–15; Igo, 2009, p. 183, figs. 152.23–152.24;
Orchard, 2010, figs. 5.9, 5.10.
Platyvillosus costatus (Staesche, 1964). Goel, 1977, p.
1098, pl. 2, figs. 15–21; Wang and Cao, 1981, p. 371,
pl. 2, figs. 1–4, 28, 29, 30, 33; Koike, 1982, p. 44, pl.
5, figs. 1–9; Tian et al., 1983, p. 391, pl. 81, fig. 2;
Matsuda, 1984, p. 128, pl. 6, figs. 6–10; Duan, 1987,
pl. 3, fig. 4; Koike, 1988, pl. 1, figs. 1–57, pl. 2, figs.
1–37; Bui, 1989, p. 411, pl. 31, figs. 7–9; Beyers andOrchard, 1991, pl. 5, fig. 10; Cao and Wang, 1993,
pl. 56, fig. 16; Wang and Zhong, 1994, p. 404, pl.1,
figs. 15, 23.

Material examined: One specimen,
MPC25263, from BT01-03.
Description: Dextral segminiplanete element; outline of platform ellipsoidal withsharply pointed anterior and posterior ends;
length 0.53 mm; width 0.25 mm; length towidth ratio 2.1. Upper surface of the platform
bears 10 transverse ridge-like denticles, denticle form straight in middle part and curved
convexly toward center in middle to both anterior and posterior parts. Element exhibits
slightly bowed lateral form. Basal cavity narrow, sub-rounded. Groove runs from basal pit
to anterior end.
Remarks: Koike (1988) demonstrated
morphological variation in the ornamentationof Platyvillosus costatus (Staesche, 1964)(= Eurygnathodus costatus Staesche, 1964)
based on abundant specimens from the Taho
limestone, Southwest Japan. He recognized
four morphotypes (Central form, Morphotypeα, β, γ, σ) and fifteen forms (A–O) based on
the ornamentation on the platform. Central
form (= Form A) is characterized by transverse
ridges covering the entire width of the platform. This form is identical to the holotype of
this species (Staesche, 1964, pl. 28, figs. 1–4).
Morphotype α has nodose denticles and is subdivided into three forms (Form B, C, D). Morphotype β exhibits a size increase of denticles
in the axial region and includes three forms(Form E, F, G). Morphotype γ represents a tendency toward development of increasingly
prominent nodose to ridge-like denticulationand consists of four forms (Form H, I, J, K).

Morphotype σ shows a tendency to decrease inoral ornamentation and includes four forms(Form L, M, N, O).
The described specimen has conspicuous
ridge-like denticles, which extend the entire
width of the platform. This feature matches
well with Form A of Koike (1988). Bui (1989)
described some specimens of Eurygnathodus
costatus from the Bac Thuy Formation, one ofwhich (Bui, 1989, pl. 31, fig. 7) is identical toForm A and a second type with weak ridgelike denticles (Bui, 1989, pl. 31, figs. 8, 9), isvery similar to Form L of Morphotype σ.
Occurrence: Specimen from BT01-03
within the portion of the Novispathodus ex gr.
waageni Zone in the Flemingites rursiradiatus
beds (lowest Middle Smithian = middle Lower
Olenekian) in the Bac Thuy Formation, northeastern Vietnam. This species also occurs in
Lower Triassic formations in South Tirol(Staesche, 1964), Spiti, India (Goel, 1977; Orchard and Krystyn, 2007; Orchard, 2010),
Kashmir, India (Matsuda, 1984), South China(Wang and Cao, 1981; Wang and Zhong,1994), Malaysia (Koike, 1982), Southwest
Japan (Koike, 1988), British Columbia, Canada (Neogonlodella milleri Zone, Beyers andOrchard, 1991), South Primorye, Russia (Neospathodus dieneri-Ns. pakistanensis Zone and
Neospathodus ex gr. waageni-Ns. novaehollandiae Zone, Shigeta et al., 2009). According
to Orchard and Krystyn (2007) and Shigeta etal. (2009), this species ranges from the Upper
Dienerian to the Smithian.
Genus Neospathodus Mosher, 1968
Type species: Spathognathodus cristagalli
Huckriede, 1968.
Neospathodus aff. concavus Zhao andOrchard, 2007
Fig. 161.7–161.9
aff. Neospathodus concavus Zhao and Orchard, 2007, in
Zhao et al., 2007, p. 35, pl. 1, figs. 1A–C; Orchard
and Krystyn, 2007, fig. 4; Igo, 2009, p. 184–185, fig.

Olenekian (Early Triassic) in northeastern Vietnam
154.13.

Material examined: One specimen,
MPC25264, from BT01-07.
Description: Bowed segminate element
0.73 mm in length; 0.48 mm in height; length
to height ratio 1.5. Pole-like pointed denticles
total 12 in number. Lower part of element
straight anteriorly and downturned at posterior
margin. Non-expanded basal cavity convex toaboral surface. Groove extends to anterior end.
Remarks: The described specimen is similar to Neospathodus concavus Zhao and Orchard, 2007 in having a bowed element, butdiffers by a convex, non-expanded basal cavity. Ns. concavus has an arched blade, a concave, expanded and rounded basal cavity, anda prominent lateral rib.
Occurrence: Described specimen fromBT01-07 within a portion of the Novispathodus ex gr. waageni Zone between the Flemingites rursiradiatus beds (lowest Middle Smithian = middle Lower Olenekian) and Urdycerastulongensis beds (lower Middle Smithian = middle Lower Olenekian) in the Bac Thuy
Formation, northeastern Vietnam. This species
also occurs in the Upper Dienerian (upper
Upper Induan, Neospathodus cristagalli Zone
with Gyronites frequens Zone) in the Mikin
Formation at the Mud Section, Spiti, India(Orchard and Krystyn, 2007), in the Lower
Smithian (lower Lower Olenekian) in Anhui
Province, South China (Neospathodus waageni eowaageni Subzone to Neospathodus waageni waageni Subzone with Flemingites-Euflemeingites Zone, Zhao et al., 2007) and South
Primorye (Neospathodus ex gr. waageni-Ns.
novaehollandiae Zone with Clypeoceras timorense Zone, Shigeta et al., 2009).
Neospathodus cristagalli (Huckriede, 1958)
Fig. 161.10–161.12
Spathognathodus cristagalli Huckriede, 1958, p. 161, pl.
10, fig. 14, 15.
Neospathodus cristagalli (Huckriede, 1958). Sweet,
1970a, p. 9, pl. 1, figs. 18, 21; Sweet, 1970b, p. 246,
pl. 1, figs. 14, 15; Mosher, 1973, p. 170, pl. 20, fig. 4;

223

Matsuda, 1982, p. 92, pl. 3, figs. 1–12; Tian et al.,1983, p. 375, pl. 80, figs. 2a, 2b; Orchard andKrystyn, 2007, pl. 1, fig. 5.
multielement apparatuses, Neospathodus cf. cristagalli(Huckriede, 1958). Orchard, 2005, p. 88, text-fig. 14.

Material examined: One specimen,
MPC25265, from BT01-04
Description: Laterally compressed bladelike element 0.75 mm in length; 0.48 mm inheight; length to height ratio 1.6, with arched
upper edge. Basal margin straight anteriorly
and slightly turned upward in the posterior
one-third. Reclined broad denticles, 12 in
number, lower part fused and upper part discrete, highest point situated in posterior onethird of element. Triangular shaped large process situated at posterior end. Basal cavity oblong, with deep pit, and groove extends frompit to anterior end.
Remarks: The described specimen has aterminal triangular denticle at the posterior
end, which is a diagnostic feature of Neospathodus cristagalli (Huckriede, 1958). The
lateral form of the element and the ratio of the
fused part of the denticles of the described
specimen are similar to those of the holotype(Huckriede, 1958, pl. 10, fig. 15) and specimens described by various authors (e.g.
Sweet, 1970a, b; Matsuda, 1982; Tian et al.,1983).
Occurrence: Described specimen fromBT01-04 within the portion of the Novispathodus ex gr. waageni Zone in the Flemingites
rursiradiatus beds (lowest Middle Smithian = middle Lower Olenekian) in the Bac Thuy
Formation, northeastern Vietnam. This species
also ranges from the Upper Dienerian (upper
Upper Induan) to the Smithian (Lower Olenekian) in the Salt Range, Pakistan (Huckriede, 1958; Sweet, 1970a, b), British Columbia,
Canada (Vavilovites sverdrupi Zone, Mosher,1973), Kashmir, India (Matsuda, 1982), Tibet(Tian et al., 1983), and the Mikin Formation at
the Mud Section, Spiti, India (Neospathodus
cristagalli Zone to Neospathodus waageni
sensu stricto Zone with Gyronites frequens

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Zone, Meekophiceras? vercherei beds, and Rohillites rohilla Zone, Krystyn et al., 2007; Orchard, 2007b; Orchard and Krystyn, 2007).
Neospathodus dieneri Sweet, 1970aFigs. 161.13–161.45, 162, 163, 164.1–164.6
Neospathodus dieneri Sweet, 1970a, p. 9, pl. 1, fig. 17;
Sweet, 1970b, p. 249, pl. 1, figs. 1, 4; McTavish,
1973, p. 293, pl. 2, figs. 3, 6; Birkenmajer and Trammer, 1975, pl. 1, fig. 4; Buryi, 1979, p. 52, pl. 7. fig.
7; Wang and Cao, 1981, pl. 2, figs. 24, 25; Matsuda,
1982, p. 90, pl. 2, figs. 1–11; Koike, 1982, p. 37, pl.
6, figs. 15–21, 25; Beyers and Orchard, 1991, pl. 5,
fig. 4; Wang and Zhong, 1994, p. 400, pl. 1, figs. 18;
Zhao and Orchard (in Zhao et al., 2007), p. 35, pl. 1,
figs. 12A, B, 9A, B, C, 11A, B, C; Orchard andKrystyn, 2007, figs. 3, 6, 7; Igo , 2009, p. 186, 188,
figs. 151.6–151.16, 152.8, 152.9; Beranek et al.,2010, figs. 6.20, 6.21.

Material examined: One specimen,
MPC25266, from BT01-04, two specimens,
MPC25267, 25268, from BT01-07, one specimen, MPC25269, from BT02-02, one specimen, MPC25270, from KC01-01, three specimens, MPC25271–25273, from KC01-11,
forty specimens, MPC25274–25313, from
KC02-02, and one specimen, MPC25314,
from KC02-03.
Description: Sub-triangular or sub-squaresegminate elements 0.32–0.55 mm in length,
average 0.41 mm; 0.32–0.55 mm in height, average 0.38 mm; length to height ratio 0.7–1.6,
average 1.1 for forty-nine specimens. Denticles erect or slightly reclined posteriorly, andvary in number from 4 to 9, average 6. Cusp
situated at posterior end. Some specimens
have small posterior denticle. Lower margin ofelement straight and slightly upturned or concave anteriorly, and upturned posteriorly.
Rounded or sub-rounded basal cavity extends
one-fourth to one-half the length of the element and is slightly or strongly concave.
Groove runs from basal pit to anterior end.
Remarks: Zhao et al. (2007) recognized
three morphotypes in Neospathodus dieneri
Sweet, 1970a. Morphotype 1 has the longest
posterior terminal cusp, which is broader inwidth than the other morphotypes. Morphotype 2 is characterized by a penultimate denticle as large as the terminal cusp. Morphotype
3 has an additional posterior denticle, which isbroader in width and shorter in length than theother denticles. These morphotypes occur continuously in ascending order from the Upper
Dienerian to the Smithian part of the Yinkeng
Formation in the West Pingingshan Section,
South China (Zhao et al., 2007). Specimensfrom the Bac Thuy Formation include all morphotypes of Zhao et al. (2007), and their ranges are equal.
Occurrence: Described specimens fromBT01-04, BT01-07, BT02-02, KC01-01,
KC01-11, KC02-02 and KC02-03 within the
portion of the Novispathodus ex gr. waageni
Zone that includes the Flemingites rursiradiatus beds (lowest Middle Smithian = middle
Lower Olenekian), Urdyceras tulongensis
beds (lower Middle Smithian = middle Lower
Olenekian) and the Leyeceras and Guodunites
horizons of the Owenites koeneni beds (middle
to upper Middle Smithian = middle Lower Olenekian) in the Bac Thuy Formation, northeastern Vietnam. This species also ranges from theDienerian (Upper Induan) to the Smithian(Lower Olenekian) in the Salt Range, West
Pakistan (Zone 3 to middle part of Zone 7,
Sweet, 1970a, b), Australia (McTavish, 1973),
Svalbard (Birkenmajer and Trammer, 1975;
Hatlebarg and Clark, 1984), Spiti, India (Goel,
1977; Orchard and Krystyn, 2007), South Primorye, Russia (Neospathodus dieneri-Ns. pakistanensis Zone with Clypeoceras spitiense“bed” and lower part of Paranorites varians
Zone, Shigeta et al., 2009), South China (Neospathodus dieneri M1 Zone to lower part of
Neospathodus waageni waageni Subzone withupper part of Ophiceras-Lytophiceras Zone,
Prionolobus-Gyronites Zone, and lower partof Fleminigites-Euflemingites Zone, Wang andCao, 1981; Zhao et al., 2007), Kashmir, India(Matsuda, 1982), Malaysia (Koike, 1982), andBritish Columbia, Canada (Beyers and Orchard, 1991; Beranek et al., 2010). Ns. dieneri

Olenekian (Early Triassic) in northeastern Vietnam

225

Fig. 162. Neospathodus dieneri Sweet, 1970a from KC02-02. 1–3, MPC25277. 4–6, MPC25278. 7–9,
MPC25279. 10–12, MPC25280. 13–15, MPC25281. 16–18, MPC25282. 19–21, MPC25283. 22–24,
MPC25284. 25–27, MPC25285. 28–30, MPC25286. 31–33, MPC25287. 34–36, MPC25288. 37–39,
MPC25289. 40–42, MPC25290. 43–45, MPC25291. 46–48, MPC25292. 49–51, MPC25293. 52–54,
MPC25294.

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Fig. 163. Neospathodus dieneri Sweet, 1970a from KC02-02. 1–3, MPC25295. 4–6, MPC25296. 7–9,
MPC25297. 10–12, MPC25298. 13–15, MPC25299. 16–18, MPC25300. 19–21, MPC25301. 22–24,
MPC25302. 25–27, MPC25303. 28–30, MPC25304. 31–33, MPC25305. 34–36, MPC25306. 37–39,
MPC25307. 40–42, MPC25308. 43–45, MPC25309. 46–48, MPC25310. 49–51, MPC25311. 52–54,
MPC25312.

Olenekian (Early Triassic) in northeastern Vietnam

227

Fig. 164. 1–6, Neospathodus dieneri Sweet, 1970a. 1–3, MPC25313, from KC02-02. 4–6, MPC25314, from
KC02-03. 7–24, Neospathodus novaehollandiae McTavish, 1973. 7–9, MPC25315, from BT01-03. 10–12,
MPC25316, from BT01-07. 13–15, MPC25317, from BT01-10. 16–18, MPC25318, from BT01-10. 19–21,
MPC25319, from BT01-10. 22–24, MPC25320, from BT01-10.

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attains its maximum abundance at KC02-02 in
the Bac Thuy Formation. A similar phenomenon is also reported from the Ns. w. waageni
Subzone in the Yinkeng Formation, South
China (Zhao et al., 2007).
Neospathodus novaehollandiae McTavish, 1973
Figs. 164.7–164.24, 165.1–165.3
Neospathodus novaehollandiae McTavish, 1973, p. 294,
figs. 4, 5, 14, 16–23; Goel, 1977, p. 1091, pl. 1, figs.
1, 2; Beyers and Orchard, 1991, pl. 5, fig. 7; Orchard,
2007b, figs. 15–18, 27, 28; Igo, 2009, p. 188, 190,
figs. 153.8–153.14, 154.7–154.11, 155.1–155.11.

Material examined: One specimen,
MPC25315, from BT01-03, one specimen,
MPC25316, from BT01-07, four specimens,
MPC25317–25320, from BT01-10, and one
specimen, MPC25321, from KC01-05.
Description: Blade-like large elements
0.49–1.25 mm in length, average 0.86 mm;
0.35–0.64 mm in height, average 0.48 mm;
length to height ratio 1.4–2.0, average 1.8 forseven specimens. Robust, broad, pole-like andfused denticles vary in number from 8 to 12,
average 10, sub-erect or reclined posteriorly.
Upper edge forms arched or straight outline.
Cusp, situated in nearby posterior end, bears
one to three small posterior denticles. Some
specimens have a cusp twice as long as otherdenticles. Prominent lateral rib at middle andlower parts of element. Lower margin straightin larger element, and straight anteriorly andupturned in posterior one-third in smaller
specimen (MPC25320). Rounded basal cavity
expanded in posterior one-third of element.
Deep furrow extends from both anterior andposterior ends.
Remarks: The element of Neospathodus
novaehollandiae Mctavish, 1973 resembles
that of Ns. pakistanensis Sweet, 1970b, but
previous authors have already pointed out thatNs. novaehollandiae has a larger element, astronger lateral rib, and a straighter lower margin than Ns. pakistanensis. These features enable us to distinguish the mentioned species.

Occurrence: Described specimens fromBT01-03, BT01-10 and KC01-05 within the
portion of the Novispathodus ex gr. waageni
Zone that includes the Flemingites rursiradiatus beds (lowest Middle Smithian = middle
Lower Olenekian) and Urdyceras tulongensis
beds (lower Middle Smithian = middle Lower
Olenekian) in the Bac Thuy Formation, northeastern Vietnam. This species also occurs in
the Smithian (Lower Olenekian) in West Australia (McTavish, 1973), Spiti, India (Goel,
1977; Orchard, 2007b), British Columbia,
Canada (Beyers and Orchard, 1991), andSouth Primorye, Russia (Neospathodus ex gr.
waageni-Ns. novaehollandiae Zone with Clypeoceras timorense Zone and Radioprionites
abrekensis “bed”, Shigeta et al., 2009).
Neospathodus pakistanensis Sweet, 1970b
Fig. 165.4–165.24
Neospathodus pakistanensis Sweet, 1970b, p. 254, pl. 1,
figs. 16, 17; McTavish, 1973, p. 295, pl. 1, figs. 1, 2;
Buryi, 1979, p. 57, pl. 9. fig. 2; Wang and Cao, 1981,
p. 367, pl. 2, fig. 27; Matsuda, 1983, p. 87, pl. 1, figs.
1–5; Tian et al., 1983, p. 379, pl. 81, fig. 3; Hatlebarg
and Clark, 1984, pl. 1, fig. 5; Beyers and Orchard,
1991, pl. 5, fig. 2; Cao and Wang, 1993, pl. 56, fig.
14; Orchard, 2007b, figs. 19, 20, 23–26; Orchard andKrystyn, 2007, figs. 19, 20; Orchard, 2008, p. 407,
figs. 8.11, 8.12; Igo, 2009, p. 190, 192, figs. 151.18–
151.26, 152.1–152.7, 152.10–152.13, 152.20–
152.21, 153.1–153.7, 154.1–154.6; Beranek et al.,2010, figs. 6.31–6.33.
Neospathodus homeri (Bender, 1970). Bui, 1989, p. 402,
pl. 31, fig. 16.

Material examined: Five specimens,
MPC25322–25326, from BT01-03, one specimen, MPC25327, from BT01-04, and one
specimen, MPC25328, from BT01-06.
Description: Blade-like elements 0.51–
0.75 mm in length, average 0.60 mm; 0.36–
0.47 mm in height, average 0.35 mm; length toheight ratio 1.4–2.1, average 1.7 for sevenspecimens. Upper edge of element straight orarched, highest point located at posterior onethird, lower edge generally straight or upwardat anterior end, posterior part of lower marginOlenekian (Early Triassic) in northeastern Vietnam

229

Fig. 165. 1–3, Neospathodus novaehollandiae McTavish, 1973, MPC25321, from KC01-05. 4–24, Neospathodus pakistanensis Sweet, 1970b. 4–6, MPC25322, from BT01-03. 7–9, MPC25323, from BT01-03. 10–12,
MPC25324, from BT01-03. 13–15, MPC25325, from BT01-03. 16–18, MPC25326, from BT01-03. 19–21,
MPC25327, from BT01-04. 22–24, MPC25328, from BT01-06. 25–33, Neospathodus posterolongatus Zhao
and Orchard, 2007 from BT01-03. 25–27, MPC25329. 28–30, MPC25330. 31–33, MPC25331.

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slightly deflected upward or slightly downturned posteriorly. Spine-like denticles vary innumber from 9 to 13, average 10, erect or reclined posteriorly. Cusp bears two posterior
small denticles. Rounded or sub-rounded basal
cavity situated in posterior one-third. Groove
extends from basal pit to anterior end.
Remarks: Neospathodus pakistanensis
Sweet, 1970b is characterized by its blade-likeelement, sub-rounded basal cavity, several
posterior small denticles, and a strongly downturned posterior lower margin. Although thedescribed specimens have a slightly upturned
lower posterior margin, they share many features with Ns. pakistanensis.
Occurrence: Described specimens fromBT01-03, BT04 and BT01-06 within the portion of the Novispathodus ex gr. waageni Zone
that includes the Flemingites rursiradiatus
beds (lowest Middle Smithian = lower Lower
Olenekian) in the Bac Thuy Formation, northeastern Vietnam. This species also ranges fromthe Upper Dienerian (upper Upper Induan) to
Lower Smithian (lower Lower Olenekian) in
the Salt Range, Pakistan (Zone 6, Sweet,
1970b), West Australia (McTavish, 1973),
South Primorye (Buryi, 1979; Neospathodus
dieneri-Ns. pakistanensis Zone and Neospathodus ex gr. waageni-Ns. novaehollandiae
Zone with Clypeoceras spitienze “bed”, Paranorites varians Zone, and Clypeoceras timorenze Zone, Shigeta et al., 2009), South
China (Wang and Cao, 1981; Cao and Wang,
1993), Kashmir, India (Matsuda, 1983), Tibet(Tian et al., 1983), and the Mikin Formation at
the Mud Section, Spiti, India (Krystyn et al.,2007; Orchard, 2007b; Orchard and Krystyn,2007).
Neospathodus posterolongatus Zhao andOrchard, 2007
Figs. 165.25–165.33, 166.1–166.18
Neospathodus waageni subsp. B Zhao, 2004, p. 42, fig. 2.
Neospathodus posterolongatus Zhao and Orchard, in Zhao
et al., 2007, p. 36, pl. 1, figs. 2A, B. C; Orchard,
2007b, figs. 1–6; Orchard, 2008, p. 407, figs. 8.3, 8.4;

Beranek et al., 2010, figs. 6.24, 6.25.

Material examined: Four specimens,
MPC25329–25332, from BT01-03, three specimens, MPC25333–25335, from BT01-04, andtwo specimens, MPC25336, 25337, from
KC01-01.
Description: Blade-like elements 0.53–
0.78 mm in length, average 0.64 mm; 0.35–
0.54 mm in height, average 0.43 mm; length toheight ratio 1.3–1.9, average 1.5 for nine specimens. Arched upper edge bears needle-likedenticles that vary in number from 10 to 13,
average 12, discrete in upper half, reclined anteriorly in anterior part, erect or inclined posteriorly in center and posterior parts, denticle
size decreases both anteriorly and posteriorly.
Cusp situated in posterior one-third. Loweredge straight and slightly upturned in anterior
end. Ellipsoidal basal cavity extended to posterior with shallow pit. Groove runs frombasal pit to anterior end.
Remarks: Neospathodus posterolongatus
Zhao and Orchard, 2007 is distinguishable
from the typical Ns. waageni Sweet, 1970b by
the posterior elongation of the basal cavity andthe presence of small secondary posterior denticles (Zhao and Orchard, 2007).
Occurrence: Described specimens fromBT01-03, BT01-4, and KC01-01 within the
portion of the Novispathodus ex gr. waageni
Zone that includes the Flemingites rursiradiatus beds (lowest Middle Smithian = middle
Lower Olenekian) in the Bac Thuy Formation,
northeastern Vietnam.
The first appearance datum (FAD) of Neospathodus posterolongatus in the Yingkeng
Formation at the West Pingdingshan Section,
South China is situated 3 cm below the FAD of
the ammonoids Flemingites and Euflemingites,
which indicates the Induan/Olenekian Boundary (IOB) of this formation. This evidence
suggests that Ns. posterolongatus may haveage diagnostic potential for the IOB (Zhao etal., 2007). In addition, this species co-occurs
with Ns. ex gr. waageni Morphotype 1, whoseOlenekian (Early Triassic) in northeastern Vietnam

231

Fig. 166. 1–18, Neospathodus posterolongatus Zhao and Orchard, 2007. 1–3, MPC25332, from BT01-03. 4–6,
MPC25333, from BT01-04. 7–9, MPC25334, from BT01-04. 10–12, MPC25335, from BT01-04. 13–15,
MPC25336, from KC01-01. 16–18, MPC25337, from KC01-01. 19–33, Neospathodus spitiensis Goel, 1977.
19–21, MPC25338, from BT01-03. 22–24, MPC25339, from BT01-03. 25–27, MPC25340, from BT01-03.
28–30, MPC25341, from BT01-03. 31–33, MPC25342, from BT01-04.

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FAD defines the IOB in the Mianwali Formation of Spiti, India (Krystyn et al., 2007; Orchard and Krystyn, 2007).
This species also ranges from the Upper
Dienerian (upper Upper Induan) to Lower
Smithian (lower Lower Olenekian) in the
Yingkeng Formation, South China (Neospathodus waageni eowaageni Subzone and lower
part of Neospathodus waageni waageni Subzone with uppermost part of Prionolobus-Gyronites Zone and lower part of FlemingitesEuflemingites Zone, Zhao et al., 2007), theMikin Formation in the Mud section, Spiti,
India (Neospathodus waageni sensu lato Zone
and Neospathodus waageni sensu stricto Zone
with Rohillites rohilla Zone, Krystyn et al.,2007; Orchard, 2007b), in British Columbia,
Canada (Beranek et al., 2010), and the Canadian Arctic (Euflemingites romunderi Zone,
Orchard, 2008).
Neospathodus spitiensis Goel, 1977
Figs. 166.19–166.33, 167–169, 170.1–170.6
Neospathodus spitiensis Goel, 1977, p. 1094, pl. 1, figs.
14–18; Duan, 1987, pl. 2, fig. 19; Orchard andKrystyn, 2007, figs. 23, 24; Igo, 2009, p. 194, figs.
156.1–156.6, 156.21–156.22.
Neospathodus homeri (Bender, 1970). Bui, 1989, p. 402,
pl. 31, fig. 15.

Material examined: Four specimens,
MPC25338–25341, from BT01-03, two specimens, MPC25342, 25343, from BT01-04,
nineteen specimens, MPC25344–25362, fromBT01-07, five specimens, MPC25363–25367,
from BT01-10, two specimens, MPC25368,
25369, from BT01-12, one specimen,
MPC25370, from BT02-01, one specimen,
MPC25371, from KC01-01, three specimens,
MPC25372–25374, from KC01-04, two specimens, MPC25375, 25376, from KC01-05, andone specimen, MPC25377, from KC01-06.
Description: Laterally compressed segminate elements 0.38–0.81 mm in length, average
0.60 mm; 0.35–0.60 mm in height, average
0.45 mm; length to height ratio 0.9–2.2, average 1.3 for forty specimens. Upper part of ele-ment arched and consists of laterally compressed, fairly discrete denticles. Denticles
vary in number from 8 to 13, average 10, suberect or reclined anteriorly, gradually inclined
to posterior end. Cusp situated in posterior
one-third with 2 to 4 small posterior denticles.
Some specimens have a large triangularshaped process at posterior end. Basal margin
straight or almost upturned in anterior part,and upturned 10–40 degrees in posterior part.
Anterior part occupies more than half of element. Sub-triangular or sub-rounded basal
cavity unexpanded in general, and gradually
narrows toward posterior end. Groove extends
from anterior end to posterior end.
Remarks: Neospathodus spitiensis Goel,1977 is characterized by its arched elementwith mostly discrete denticles, upturned basal
margin of posterior one-third to half, and narrow triangular shaped basal cavity, which extends posteriorly (Goel, 1977; Orchard andKrystyn, 2007). Igo (2009) reported that somespecimens of this species have a posteriorly
extended elliptical basal cavity. The described
specimens exhibit a wide range of intraspecificvariation in basal cavity form and denticulation, but they also include similar forms reported by previous authors. Some specimens
have a large triangular process, which has
never been reported.
Occurrence: Described specimens fromBT01-03, BT01-04, BT01-07, BT01-10,
BT01-12, BT02-01, KC01-01, KC01-04,
KC01-05 and KC01-06 within the portion of
the Novispathodus ex gr. waageni Zone that
includes the Flemingites rursiradiatus beds
(lowest Middle Smithian = middle Lower Olenekian) and Urdyceras tulongensis beds
(lower Middle Smithian = middle Lower Olenekian) in the Bac Thuy Formation, northeastern Vietnam. This species also occurs in theLower Smithian (lower Lower Olenekian) in
Spiti, India (Goel, 1977; Krystyn et al., 2007;
Orchard and Krystyn, 2007), South China(Duan, 1987; Zhao et al., 2007), and South
Primorye, Russia (Igo, 2009).

Olenekian (Early Triassic) in northeastern Vietnam

233

Fig. 167. Neospathodus spitiensis Goel, 1977. 1–3, MPC25343, from BT01-04. 4–7, MPC25344, from BT01-07.
8–10, MPC25345, from BT01-07. 11–13, MPC25346, from BT01-07. 14–16, MPC25347, from BT01-07. 17–
19, MPC25348, from BT01-07. 20–22, MPC25349, from BT01-07. 23–24, MPC25350, from BT01-07. 25–
27, MPC25351, from BT01-07. 28–30, MPC25352, from BT01-07.

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 168. Neospathodus spitiensis Goel, 1977. 1–3, MPC25353, from BT01-07. 4–6, MPC25354, from BT01-07.
7–9, MPC25355, from BT01-07. 10–12, MPC25356, from BT01-07. 13–15, MPC25357, from BT01-07. 16–
18, MPC25358, from BT01-07. 19–21, MPC25359, from BT01-07. 22–24, MPC25360, from BT01-07. 25–
27, MPC25361, from BT01-07. 28–30, MPC25362, from BT01-07. 31–33, MPC25363, from BT01-10. 34–
36, MPC25364, from BT01-10.

Olenekian (Early Triassic) in northeastern Vietnam

235

Fig. 169. Neospathodus spitiensis Goel, 1977. 1–3, MPC25365, from BT01-10. 4–6, MPC25366, from BT01-10.
7–9, MPC25367, from BT01-10. 10–12, MPC25368, from BT01-12. 13–15, MPC25369, from BT01-12. 16–
18, MPC25370, from BT02-01. 19–20, MPC25371, from KC01-01. 21–23, MPC25372, from KC01-04. 24–
26, MPC25373, from KC01-04. 27–29, MPC25374, from KC01-04. 30–32, MPC25375, from KC01-05.

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 170. 1–6, Neospathodus spitiensis Goel, 1977. 1–3, MPC25376, from KC01-05. 4–6, MPC25377, from
KC01-06. 7–33, Neospathodus sp. indet. A. 7–9, MPC25378, from BT01-03. 10–12, MPC25379, from BT0106. 13–15, MPC25380, from BT01-10. 16–18, MPC25381, from BT01-10. 19–21, MPC25382, from BT0112. 22–24, MPC25383, from BT01-12. 25–27, MPC25384, from BT01-12. 28–30, MPC25385, from BT0114. 31–33, MPC25386, from KC01-13.

Olenekian (Early Triassic) in northeastern Vietnam

237

The first appearance datum of this species
is located in bed 15 of the Muth section in
Spiti (Orchard and Krystyn, 2007; Krystyn etal., 2007) and bed 26 of the West Pingdingshang section in Anhui Province, South China(Zhao et al., 2007), both of which correspondto the Flemingites-Euflemingites Zone of theSmithian (Orchard and Krystyn, 2007; Orchard, 2010).

includes the Flemingites rursiradiatus beds
(lowest Middle Smithian = middle Lower Olenekian), Urdyceras tulongensis beds (lower
Middle Smithian = middle Lower Olenekian)and Leyeceras horizon of the Owenites koeneni beds (middle Middle Smithian = middle
Lower Olenekian) in the Bac Thuy Formation,
northeastern Vietnam.

Neospathodus sp. indet. A

Fig. 171.1–171.3

Fig. 170.7–170.33

Material examined: One specimen,
MPC25378, from BT01-03, one specimen,
MPC25379, from BT01-06, two specimens,
MPC25380, 25381, from BT01-10, three specimens, MPC25382–25384, from BT01-12, one
specimen, MPC25385, from BT01-14, andone specimen, MPC25286, from KC01-13.
Description: Segminate elements 0.39–
0.62 mm in length, average 0.50 mm; 0.45–
0.65 mm in height, average 0.56 mm; length toheight ratio 0.7–0.9, average 0.9 for nine specimens. Lateral profile of elements exhibits
chevron-like form, with arched upper edge.
Reclined slender denticles vary in number
from 6 to 9, average 7. Cusp situated in centerof element, size twice as large as other denticles. Large terminal process exhibits a triangular shape. Lower edge straight or almost upturned in anterior half, and upturned 15–40 degrees in posterior half. Outline of expandedbasal cavity triangular. Anterior furrow extends to basal pit.
Remarks: The described specimen is very
close to Neospathodus spitiensis Goel, 1977 inhaving a triangular terminal process at theposterior end and a triangular basal cavity,
whose height is greater than its length, but differs by its vertical long element and a slightly
fewer number of denticles.
Occurrence: Described specimens fromBT01-03, BT01-06, BT01-10, BT01-12,
BT01-14 and KC01-13 within the portion of
the Novispathodus ex gr. waageni Zone that

Neospathodus sp. indet. B
Material examined: One specimen,
MPC25387, from BT01-04.
Description: Blade-like segminate element
0.77 mm in length; 0.48 mm in height; length
to height ratio 1.6. Lateral form of element
rectangular with arched upper edge and slightly bowed lower edge. Pointed slender denticles total 10 in number, discrete in upper half
and fused in lower half, gradually reclined
posteriorly. Large-sized terminal cusp triangular in shape. Elliptical basal cavity situated at
posterior end. Narrow groove extends to anterior end.
Remarks: The described specimen is very
close to Neospathodus pakistanensis Sweet,
1970b in having a rectangular lateral shapeand elliptical basal cavity, but differs by its triangular shaped terminal cusp.
Occurrence: Described specimen fromBT01-04 within the portion of the Novispathodus ex gr. waageni Zone represented by the
Flemingites rursiradiatus beds (lowest Middle
Smithian = middle Lower Olenekian) in the
Bac Thuy Formation, northeastern Vietnam.
Neospathodus sp. indet. C
Fig. 171.4–171.6

Material examined: One specimen,
MPC25388, from KC01-11.
Remarks: The specimen is characterized
by its strongly reclined, laterally compressed
denticles, which are discrete in the upper twothirds. The form in lower view is slightly sigmoidal, and the width of the element is longer

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Fig. 171. 1–3, Neospathodus sp. indet. B, MPC25387, from BT01-04. 4–6, Neospathodus sp. indet. C,
MPC25388, from KC01-11. 7–12, Smithodus longiusculus (Buryi, 1979). 7–9, MPC25389, from BT01-07.
10–12, MPC25390, from KC01-01. 13–31, Novispathodus pingdingshanensis (Zhao and Orchard, 2007). 13–
16, MPC25391, from KC02-08. 17–18, MPC25392, from KC02-10. 19–21, MPC25393, from KC02-12. 22–
24, MPC25394, from KC01-17. 25–28, MPC25395, from NT01-07. 29–31, MPC25396, from NT01-07.

Olenekian (Early Triassic) in northeastern Vietnam

than other species of Neospathouds. It is close
to Ns. sp. nov. S by Orchard (2008), but differs
by its lack of the terminal largest cusp and therhomboidal outline of its basal cavity.
Occurrence: Described specimen from
KC01-11 within the portion of the Novispathodus ex gr. waageni Zone represented by the
Leyeceras horizon of the Owenites koeneni
beds (middle Middle Smithian = middle Lower
Olenekian) in the Bac Thuy Formation, northeastern Vietnam.
Genus Smithodus Budurov, Buryi and Sudar,
1988
Type species: Neospathodus longiusculus
Buryi, 1979.
Smithodus longiusculus (Buryi, 1979)
Fig. 171.7–171.12
Anchignathodus sp. A, Mosher, 1973, p. 152, pl. 17, fig. 1.
Neospathodus longiusculus Buryi, 1979, p. 58, pl. 12, fig.
1, pl. 13, fig. 1, pl. 14, fig. 1.
Smithodus longiusculus (Buryi, 1979). Buryi, 1997, pl. 1,
figs. 1, 2; Orchard, 2007a, fig. 2.

Material examined: One specimen,
MPC25389, from BT01-07, and one specimen, MPC25390, from KC01-01.
Description: Two rectangular blade-likeelements 1.16–1.17 mm in length; 0.45–
0.46 mm in height; length to height ratio 2.5–
2.6. Long, straight, and thin blade bears shortnode-like denticles totaling 12 and 15 in number, erect or reclined posteriorly. Cusp situatednear posterior end. Basal margin straight,
slightly upturned in anterior end, downturnedinposterior
one-fourth.
Specimen(MPC25390) has prominent lateral rib. Wide,large, sub-rounded basal cavity situated below
cusp, extends to posterior end, strongly concave. Deep broad furrow extends from anterior end to posterior end.
Occurrence: Described specimens collected from BT01-07 and KC01-01 within the Novispathodus ex gr. waageni Zone in the Bac
Thuy Formation, northeastern Vietnam. BT01-239

07 is located between the Flemingites rursiradiatus beds (lowest Middle Smithian = middle
Lower Olenekian) and Urdyceras tulongensis
beds (lower Middle Smithian = middle Lower
Olenekian). KC01-01 is located beneath theOwenites koeneni beds (middle Middle Smithian = middle Lower Olenekian). Mosher(1973) reported the occurrence of Smithodus
longiusculus in the Euflemingites romunderi
Zone (Middle Smithian) in Canada, and Buryi(1979) described the species from the Anasibirites nevolini Zone (Upper Smithian). Thus,
this species ranges from the middle to Upper
Smithian.
Subfamily Novispathodinae Orchard, 2005
Genus Novispathodus Orchard, 2005
Type species: Novispathodus abruptus(Orchard, 1995).
Novispathodus pingdingshanensis (Zhao andOrchard, 2007)
Fig. 171.13–171.31
Neospathodus pingdingshanensis Zhao and Orchard,
2007, in Zhao et al., 2007, p. 36, pl. 1, figs. 4A, B, C;
Ji et al., 2011, figs. 4.7–4.9; Liang et al., 2011, figs.
1–3.
multielement apparatuses, Novispathodus pingdingshanensis (Zhao and Orchard, 2007). Goudemand andOrchard (in Goudemand et al., 2012), p. 1030, figs.
2B, F, I, J, M, Q, AD, 3T, U, 6.

Material examined: One specimen,
MPC25391, from KC02-08, one specimen,
25392, from KC02-10, one specimen,
MPC25393, from KC02-12, one specimen,
MPC25394, from KC02-17, and two specimens, MPC25395, 25396, from NT01-07.
Description: Small segminate elements
0.19–0.44 mm in length, average 0.30 mm;
0.17–0.29 mm in height, average 0.24 mm;
length to height ratio 1.1–1.5, average 1.2 forsix specimens. Arched upper edge bears mostly fused, triangular-shaped denticles, varying
in number from 4 to 12, average 8, reclined
posteriorly. Cusp situated in posterior one-

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third with a few small posterior denticles.
Basal margin straight or upturned in anterior.
Large broadly expanded oval or sub-roundedbasal cavity upturned on inner margin, flat todownturned on outer margin, and occupying
more than half of basal margin with deep pit.
Groove extends to anterior end.
Remarks: The described specimens include the juveniles (MPC25392, MPC25394),
whose sizes are one-half of the others. However, the feature whereby the large basal cavity
exceeds more than half of the length of element is common in all specimens.
Occurrence: Described specimens from
KC02-08, KC02-10 and NT01-07 within the
portion of the Novispathodus pingdingshanensis Zone represented by the Xenoceltites variocostatus beds (Upper Smithian = upper Lower
Olenekian), and those from KC02-12 andKC02-17 within the portion of the Triasssospathodus symmetricus Zone that includes the
Tirolites cf. cassianus beds (lowest Lower
Spathian = lowest Upper Olenekian) and Tirolites sp. nov. beds (Lower Spathian = lower
Upper Olenekian) in the Bac Thuy Formation,
northeastern Vietnam. This species also occurs
in South China (Zhao et al., 2007; Ji et al.,2011; Liang et al., 2011; Goudemand et al.,2012).
Zhao and Orchard (in Zhao et al, 2007)
originally described this species as Neospathodus from Chaohu, Anhui Province, South
China and defined the Ns. pingdingshanensis(= Novispathodus pingdingshanensis) Zone in
the Yinkeng Formation (Zhao et al., 2007).
The zone extends from just above the Ns.
waageni Zone to the base of the Ns. homeri
Zone. Previous authors (Zhao et al., 2007;
Liang et al., 2011) have suggested that Nv.
pingdingshanensis is a zonal-index taxon forthe lowermost Lower Spathian based on theevidence that ammonoids defining the base of
the Spathian co-occur with this species. However, the species also occurs with Xenoceltites
variocostatus, which is an index ammonoid
for the Upper Smithian (Goudemand et al.,2012 and this study) in South China and northeastern Vietnam. This fact suggests that the
FAD of Nv. pingdingshanensis occurs in theUpper Smithian.
Novispathodus triangularis (Bender, 1970)
Figs. 172, 173, 174.1–174.30
Neospathodus cristagalli (Huckriede, 1958). Mosher,
1968, p. 930, pl. 115, fig. 2.
Spathognathodus triangularis Bender, 1970, p. 530, pl. 5,
figs. 22a, b.
Neospathodus biangularis Z. H. Wang and Cao, 1981, p.
367, pl. 2, figs. 22, 23; Wang and Cao, 1993, pl. 56,
fig. 15.
Neospathodus triangularis (Bender, 1970). Sweet, 1970b,
p. 253, pl. 1, figs. 7, 8; Goel, 1977, p. 1097, pl. 2,
figs. 12, 13; Solien, 1979, p. 304, pl. 3, fig. 7; Koike,
1981, pl. 1, fig. 6; Duan et al., 1983, p. 380, pl. 97,
figs. 3a, b; Matsuda, 1983, pp. 93–94, pl. 3, figs. 5–9;
Wang and Zhong, 1994, pl. 1, figs. 1, 2, 6, 10; Orchard, 1995, p. 116, 118, figs. 3.–3.4; Lucas and Orchard, 2007, figs. 10–12; Ji et al., 2011, figs. 3.7,
3.11.
Neospathodus curtatus Orchard, 1995, p. 119, figs. 3.8–
3.13.

Material examined: One specimen,
MPC25397, from KC02-14, and thirty-four
specimens, MPC25398–25431, from KC0215.
Description: P1 element: Trapezoidalshaped, small segminate elements 0.37–
0.57 mm in length, average 0.45 mm; 0.27–
0.38 mm in height, average 0.33 mm; 0.16–
0.35 mm, average 0.22 mm in width; length toheight ratio 1.2–1.7, average 1.4 for thirtythree specimens. Arched upper edge bears
erect or radial, small, fused, spine-like denticles varying in number from 10 to 14, average
12. Cusp situated from center to posterior ofelement. Denticle size gradually decreases
from cusp to both anterior and posterior ends.
Lower edge consists of straight or concave anterior part and strongly downturned posterior
margin. Sub-triangular or sub-quadrangular,
strongly concave basal cavity occupies posterior one-third to one-half length of element.
Groove extends from basal pit to anterior end.

Olenekian (Early Triassic) in northeastern Vietnam

241

Fig. 172. Novispathodus triangularis (Bender, 1970), P1 element. 1–3, MPC25397, from KC02-14. 4–6,
MPC25398, from KC02-15. 7–9, MPC25399, from KC02-15. 10–12, MPC25400, from KC02-15. 13–15,
MPC25401, from KC02-15. 16–18, MPC25402, from KC02-15. 19–21, MPC25403, from KC02-15. 22–24,
MPC25404, from KC02-15. 25–27, MPC25405, from KC02-15. 28–30, MPC25406, from KC02-15.

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Fig. 173. Novispathodus triangularis (Bender, 1970), P1 element, from KC02-15. 1–3, MPC25407. 4–6,
MPC25408. 7–9, MPC25409. 10–12, MPC25410. 13–15, MPC25411. 16–18, MPC25412. 19–21,
MPC25413. 22–24, MPC25414. 25–27, MPC25415. 28–30, MPC25416. 31–33, MPC25417. 34–36,
MPC25418. 37–39, MPC25419. 40–42, MPC25420. 43–45, MPC25421.

Olenekian (Early Triassic) in northeastern Vietnam

243

Fig. 174. 1–30, Novispathodus triangularis (Bender, 1970) from KC02-15. 1–3, P1 element, MPC25422. 4–6, P1
element, MPC25423. 7–9, P1 element, MPC25424. 10–12, P1 element, MPC25425. 13–15, P1 element,
MPC25426. 16–18, P1 element, MPC25427. 19–21, P1 element, MPC25428. 22–24, P1 element, MPC25429.
25–27, P2 element, MPC25430. 28–30, P2 element, MPC25431. 31–57, Novispathodus ex gr. waageni (Sweet,
1970b) from BT01–03. 31–33, MPC25432. 34–36, MPC25433. 37–39, MPC25434. 40–42, MPC25435. 43–
45, MPC25436. 46–48, MPC25437. 49–51, MPC25438. 52–54, MPC25439. 55–57, MPC25440.

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P2 element: Two laterally compressed, triangular-shaped segminate elements 0.49–
0.52 mm in length; 0.29 mm in height; length
to height ratio 1.7–1.8. Broad denticles total
10 in number. Size and inclination of denticles
gradually increase toward posterior end. Posterior terminal cusp bears 1 or 2 small denticles. Basal margin of element bowed. Aboral
surface concave, and slightly expanded aroundbasal pit. Groove extends from anterior end toposterior end.
Remarks: Some of the described specimens (MPC25398, 25407, 25414, etc.) have 2
to 4 small posterior processes, and hence, areclose to Neospathodus curtatus Orchard,
1995, which is probably one of the morphological variants of Novispathodus triangularis(Bender, 1970). The P2 elements of the described specimens show that the denticulation
gradually increases in size and inclination.
They are close to the P2 elements of Nv.
abruptus Orchard (2005), but the number ofdenticles is fewer.
Occurrence: Described specimens from
KC02-14 and KC02-15 within the portion of
the Triasssospathodus symmetricus Zone represented by the Tirolites sp. nov. beds (Lower
Spathian = lower Upper Olenekian) in the Bac
Thuy Formation, northeastern Vietnam. This
species occurs in the lowermost Lower Spathian in the Salt Range (Sweet, 1970b) and western USA (Sweet et al., 1971), and its range extends to the uppermost Spathian (Orchard,2010). This species is also known from Nevada (Mosher, 1968; Lucus and Orchard,2007), Chios, Greek (Bender, 1970), Spiti,
India (Goel, 1977), Southwest Japan (Koike,1981), South China (Wang and Cao, 1981;
Wang and Zhong, 1994), and Oman (Orchard,1995).
Novispathodus ex gr. waageni (Sweet, 1970b)
Figs. 174.31–174.57, 175–180, 181.1–181.31
Neospathodus waageni Sweet, 1970b, p. 260, pl. 1, figs.
11, 12; McTavish, 1973, p. 300, pl. 2, figs. 11, 22.
25–28; Mosher, 1973, p. 172, pl. 20, fig. 5; Goel,

1977, p. 1094, pl. 2, figs. 1–4; Solien, 1979, p. 304,
pl. 3, fig. 9; Buryi, 1979, p. 56, pl. 7, figs. 8, 9; Wang
and Cao, 1981, pl. 2, fig. 26; Koike, 1982, p. 39, pl.
6, figs. 24–27; Matsuda, 1983, p. 88, pl. 1, figs. 6–10,
pl. 2, figs. 1–7; Duan, 1987, pl. 2, figs. 7; Cao andWang, 1993, p. 261, pl. 56, figs. 5, 11; Wang andZhong, 1994, p. 402, pl. 1, figs. 12, 13; Nakrem etal., 2008, figs. 5.7, 5.8, 5.11, 5.14; Orchard, 2008, p.
40, figs. 8.1, 8.2, 8.8, 8.9; Beranek et al., 2010, figs.
6.22, 6.23.
Neospathodus waageni waageni Sweet, 1970b. Zhao andOrchard (in Zhao et al., 2007), p. 36, pl. 1, figs. 10A,
B.
Neospathodus waageni eowaageni Zhao and Orchard,
2007, in Zhao et al., 2007, p. 36, pl. 1, figs. 5A, B.
Neospathodus ex gr. waageni (Sweet, 1970b). Orchard
and Krystyn, 2007, figs. 8–18; Igo, 2009, p. 194, figs.
152.14–152.19, 156.7–156.19.
Novispathodus waageni (Sweet, 1970b). Goudemand andOrchard (in Goudemand et al., 2012), p. 1031, figs.
3D, E, H, N, S, T.

Material examined: Twenty-three specimens, MPC25432–25454, from BT01-03, ninespecimens, MPC25455–25463, from BT0104, seven specimens, MPC25464–25470, fromBT01-06, six specimens, MPC25471–25476,
fromBT01-07,
eighteen
specimens,
MPC25477–25494, from BT01-10, eight specimens, MPC25495–25502, from BT01-12, six
specimens, MPC25503–25508, from BT0201, two specimens, MPC25509, 25510, from
BT02–02, three specimens, MPC25511–
25513, from KC01-01, nine specimens,
MPC25514–25522, from KC01-04, one specimen, MPC25523, from KC01-05, four specimens, MPC25524–25527, from KC01-06, two
specimens, MPC25528, 25529, from KC0108, two specimens, MPC25530, 25531, from
KC01-11, two specimens, MPC25532, 25533,
from KC01-12, two specimens, MPC25534,
25535, from KC01-13, and one specimen,
MPC25536, from KC02-08.
Description: Laterally compressed archedelements 0.30–0.78 mm in length, average
0.49 mm; 0.27–0. 60 mm in height, average
0.41 mm; length to height ratio 0.9–1.8, average 1.2 for one hundred-five specimens.
Arched upper edge bears sharp pointed denti-

Olenekian (Early Triassic) in northeastern Vietnam

245

Fig. 175. Novispathodus ex gr. waageni (Sweet, 1970b) from BT01-03. 1–3, MPC25441. 4–6, MPC25442. 7–9,
MPC25443. 10–12, MPC25444. 13–15, MPC25445. 16–18, MPC25446. 19–21, MPC25447. 22–24,
MPC25448. 25–27, MPC25449. 28–30, MPC25450. 31–33, MPC25451.

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Fig. 176. Novispathodus ex gr. waageni (Sweet, 1970b). 1–3, MPC25452, from BT01-03. 4–6, MPC25453, fromBT01-03. 7–9, MPC25454, from BT01-03. 10–12, MPC25455, from BT01-04. 13–15, MPC25456, fromBT01-04. 16–18, MPC25457, from BT01-04. 19–21, MPC25458, from BT01-04. 22–24, MPC25459, fromBT01-04. 25–27, MPC25460, from BT01-04. 28–30, MPC25461, from BT01-04. 31–33, MPC25462, fromBT01-04. 34–36, MPC25463, from BT01-04. 37–39, MPC25464, from BT01-06. 40–42, MPC25465, fromBT01-06.

Olenekian (Early Triassic) in northeastern Vietnam

247

Fig. 177. Novispathodus ex gr. waageni (Sweet, 1970b). 1–3, MPC25466, from BT01-06. 4–6, MPC25467, fromBT01-06. 7–9, MPC25468, from BT01-06. 10–12, MPC25469, from BT01-06. 13–15, MPC25470, fromBT01-06. 16–18, MPC25471, from BT01-07. 19–21, MPC25472, from BT01-07. 22–24, MPC25473, fromBT01-07. 25–27, MPC25474, from BT01-07. 28–30, MPC25475, from BT01-07. 31–33, MPC25476, fromBT01-07. 34–36, MPC25477, from BT01-10. 37–39, MPC25478, from BT01-10. 40–42, MPC25479, fromBT01-10. 43–45, MPC25480, from BT01-10. 46–48, MPC25481, from BT01-10.

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Fig. 178. Novispathodus ex gr. waageni (Sweet, 1970b). 1–3, MPC25482, from BT01-10. 4–6, MPC25483, fromBT01-10. 7–9, MPC25484, from BT01-10. 10–12, MPC25485, from BT01-10. 13–15, MPC25486, fromBT01-10. 16–18, MPC25487, from BT01-10. 19–21, MPC25488, from BT01-10. 22–24, MPC25489, fromBT01-10. 25–27, MPC25490, from BT01-10. 28–30, MPC25491, from BT01-10. 31–33, MPC25492, fromBT01-10. 34–36, MPC25493, from BT01-10. 37–39, MPC25494, from BT01-10. 40–42, MPC25495, fromBT01-12. 43–45, MPC25496, from BT01-12.

Olenekian (Early Triassic) in northeastern Vietnam

249

Fig. 179. Novispathodus ex gr. waageni (Sweet, 1970b). 1–3, MPC25497, from BT01-12. 4–6, MPC25498,
from BT01-12. 7–9, MPC25499, from BT01-12. 10–12, MPC25500, from BT01-12. 13–15, MPC25501,
from BT01-12. 16–18, MPC25502, from BT01-12. 19–21, MPC25503, from BT02-01. 22–24, MPC25504,
from BT02-01. 25–27, MPC25505, from BT02-01. 28–30, MPC25506, from BT02-01. 31–33, MPC25507,
from BT02-01. 34–36, MPC25508, from BT02-01. 37–39, MPC25509, from BT02-02.

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Fig. 180. Novispathodus ex gr. waageni (Sweet, 1970b). 1–3, MPC25510, from BT02-02. 4–6, MPC25511, from
KC01-01. 7–9, MPC25512, from KC01-01. 10–12, MPC25513, from KC01-01. 13–15, MPC25514, from
KC01-04. 16–18, MPC25515, from KC01-04. 19–21, MPC25516, from KC01-04. 22–24, MPC25517, from
KC01-04. 25–27, MPC25518, from KC01-04. 28–30, MPC25519, from KC01-04. 31–33, MPC25520, from
KC01-04. 34–36, MPC25521, from KC01-04. 37–39, MPC25522, from KC01-04. 40–42, MPC25523, from
KC01-05. 43–45, MPC25524, from KC01-06. 46–47, MPC25525, from KC01-06. 48–49, MPC25526, from
KC01-06.

Olenekian (Early Triassic) in northeastern Vietnam

251

Fig. 181. 1–31, Novispathodus ex gr. waageni (Sweet, 1970b). 1–3, MPC25527, from KC01-06. 4–6,
MPC25528, from KC01-08. 7–9, MPC25529, from KC01-08. 10–12, MPC25530, from KC01-11. 13–15,
MPC25531, from KC01-11. 16–18, MPC25532, from KC01-12. 19–21, MPC25533, from KC01-12. 22–24,
MPC25534, from KC01-13. 25–27, MPC25535, from KC01-13. 28–31, MPC25536, from KC02-08. 32–38,
Novispathodus sp. nov. A Goudemand and Orchard, 2012. 32–34, MPC25537, from KC02-08. 35–38,
MPC25538, from NT01-07. 39–42, Novispathodus sp. indet. A, MPC25539, from NT01-07. 43–48, Triassospathodus homeri (Bender, 1970) from KC02-15. 43–45, MPC25540. 46–48, MPC25541.

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cles, varying in number from 6 to 13, average
9, discrete in upper one-third to one-half, suberect or reclined posteriorly, some specimens
have 1 to 3 small posterior denticles. Loweredge straight or curved slightly upward anteriorly, posterior margin upturned about 5–40 degrees. Rounded or sub-rounded basal cavity
expanded at posterior end, occupies one-fourth
to one-half of length of element, and is slightly concave. Groove extends from basal pit toanterior end.
Remarks: Following Sweet’s (1970b) firstdescription of Novispathodus waageni fromthe Salt Range as Neospathodus waageni,
Zhao et al. (2007) subdivided it into three subspecies: Ns. waageni waageni, Ns. w. eowaageni, and Ns. posterolongatus, based on many
specimens collected from the West Pingdingshan section. Furthermore, Orchard andKrystyn (2007) recognized six morphotypes
including two subspecies (Ns. w. waageni and
Ns. w. eowaageni), based on specimens foundat Spiti, India. Morphotype 1 is characterized
by the developed platform flange in the lateralside of the element. Morphotype 2 is the sameas the holotype (= Ns. w. waageni). Morphotype 3 is relatively small with a length toheight ratio of about 1.1 and is the same as Ns.
w. eowaageni. Morphotype 4 has a few small
denticles at the posterior end of the element.
Morphotype 5 has a large triangular shaped
terminal cusp. Morphotype 6 has denticles
spreading in a radial fashion from the base.
The described specimens contain Morphotypes 2, 3, 4, 5 and 6, with Morphotypes 4 and5 being relatively abundant. Specimen(MPC25536) from KC02-08 within the Nv.
pingdingshanensis Zone is smaller than theothers and has an undulating basal margin.
The size of basal cavity is smaller than that of
Nv. pingdingshanensis (Zhao and Orchard,2007).
Occurrence: Described specimens fromBT01-03, BT01-04, BT01-06, BT01-07,
BT01-10, BT01-12, BT02-01, BT02-02,
KC01-01, KC01-04, KC01-05, KC01-06,

KC01-08, KC01-11, KC01-12 and KC01-13
within the portion of the Novispathodus ex gr.
waageni Zone that includes the Flemingites
rursiradiatus beds, Urdyceras tulongensis
beds and Owenites koeneni beds (lowest to
middle Middle Smithian = middle Lower Olenekian), and KC02-08 within the portion of
the Novispathodus pingdingshanensis Zone
represented by the Xenoceltites variocostatusbeds (Upper Smithian = upper Lower Olenekian) in the Bac Thuy Formation, northeastern
Vietnam.
Novispathodus waageni is a well-known
Smithian species throughout the world, and its
FAD defines the IOB (Orchard, 2007a, b; Orchard and Krystyn, 2007; Zhao et al., 2007;
Shigeta et al., 2009; Orchard, 2010). According to Zhao et al. (2007) and Goudemand etal. (2012), Nv. waageni occurs in the uppermost Smithian with Nv. pingdingshanensis.
Therefore, Nv. waageni ranges throughout theentire Smithian.
Novispathodus sp. nov. A Goudemand andOrchard, 2012
Fig. 181.32–181.38
Novispathodus sp. nov. A Goudemand and Orchard, in
Goudemand et al., 2012, p.1031 figs. 2A, R, Z.

Material examined: One specimen,
MPC25537, from KC02-08, and one specimen, MPC25538, from NT01-07.
Description: Segminate elements 0.34–
0.41 mm in length; 0.24–0.25 mm in height;
length to height ratio 1.4–1.6 for two specimens, with arched upper edge. Highest point
situated near posterior end. Lower margin ofelement almost straight. Mostly fused andpointed denticles total 7 and 10 in number,sub-erect or reclined posteriorly. Large basal
cavity rounded and slightly concave. Groove
extends from basal pit to anterior end.
Remarks: The described specimens including juvenile (MPC25537) are characterized bya straight lower margin and mostly fused andpointed denticles, which are reclined posteri-Olenekian (Early Triassic) in northeastern Vietnam

orly. The basal cavity is smaller than that ofNovispathodus pingdingshanensis (Zhao andOrchard, 2007). These features match wellwith specimens of Nv. sp. nov. A described by
Goudemand and Orchard (in Goudemand etal., 2012) from South China.
Occurrence: Described specimens from
KC02-08 and NT01-07 within the portion of
the Novispathodus pingdingshanensis Zone
represented by the Xenoceltites variocostatusbeds (Upper Smithian = upper Lower Olenekian) in the Bac Thuy Formation, northeastern
Vietnam. This species also occurs in the lowest Spathian part of the Tsoteng section,
Guangxi, South China (Goudemand et al.,2012).
Novispathodus sp. indet. A
Fig. 181.39–181.42

Material examined: One specimen,
MPC25539, from NT01-07.
Description: Small segminate element
0.41 mm in length; 0.25 mm in height; length
to height ratio 1.6, with arched upper edge.
Node-like short denticles total 12 in number,sub-erect or reclined posteriorly. Smallest terminal process strongly reclined posteriorly.
Highest point situated above basal cavity.
Lower margin of element slightly bowed.
Asymmetrical sub-triangular basal cavity occupies posterior half of element. Thin furrow
extends from basal pit to anterior end.
Remarks: The described segminate element has a few small posterior denticles,
which are straight or reclined posteriorly and alarge basal cavity. These distinctive features
enable it to be assigned with reasonable confidence to the genus Novispathodus. The lateralview resembles Icriospathodus? crassatus(Orchard, 1995) and I.? zaksi (Buryi, 1979),
but these species have a more robust denticulation and an expanded lateral rib.
Occurrence: Described specimen fromNT01-07 within the portion of the Novispathodus pingdingshanensis Zone in the Xenocelt-

253

ites variocostatus beds (Upper Smithian = upper Lower Olenekian) in the Bac Thuy
Formation, northeastern Vietnam.
Genus Triassospathodus Kozur, 1998
Type species: Spathognathodus homeri
Bender, 1970.
Triassospathodus homeri (Bender, 1970)
Fig. 181.43–181.48
Spathognathodus homeri Bender, 1970, p. 528, pl. 5, figs.
16a, b, c.
Neospathodus homeri (Bender, 1970). Sweet, 1970b, p.
245, pl. 1, figs. 2, 3, 9, 10; Matsuda, 1983, p. 94, pl.
5, figs. 2a, b; Wang and Zhong, 1994, p. 400–401, pl.
1, fig. 27; Orchard, 1995, p. 115, figs. 2.1–2.3, 2.7–
2.9, 2.14–2.17, 2.20, 2.21.
multielement apparatuses, Triassospathodus homeri(Bender, 1970). Orchard, 2005, p. 93, text-fig. 19.
Triassospathodus ex gr. homeri (Bender, 1970). Lucas andOrchard, 2007, figs. 7.8, 7.9; Orchard et al., 2007a,figs. 5.5, 5.6; Orchard et al., 2007b, figs. 6.10–6.12;
Orchrad, 2010, figs. 7.15, 7.16.

Material examined: Two specimens,
MPC25540, 25541, from KC02-15.
Description: Two slender blade-like elements 0.64–0.74 mm in length; 0.30–0.39 mm
in height; length to height ratio 1.9–2.1.
Arched upper edge bears triangular-shaped
fused denticles totaling 11 and 16 in number,including 3 or 4 posterior small terminal processes, gradually reclined posteriorly. Cusp
situated in middle part of element. Basal margin straight in anterior two-thirds, downturnedin posterior one-third. Sub-rounded basal cavity elongated and curved laterally at terminal
end. Narrow groove extends from basal pit toanterior end.
Remarks: Triassospathodus homeri (Bender, 1970) is one of the well-known characteristic species of the Spathian. According to Orchard (1995), the diagnostic features of thetaxon include the posteriorly elongated elliptical basal cavity and the presence of several
small posterior processes. In contrast, T. symmetricus (Orchard, 1995) lacks small posterior

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denticles and the asymmetrical basal cavity,
which is slightly elongated posteriorly. In the
Bac Thuy Formation, the FAD of T. homeri at
KC02-15 occurs above the FAD of T. symmetricus at KC02-12. This evidence suggests that
T. homeri evolved from T. symmetricus during
earliest Spathian time.
Occurrence: Described specimens from
KC02-15 within the portion of the Triassospathodus symmetricus Zone represented by
the Tirolites sp. nov. beds (Lower Spathian = lower Upper Olenekian) in the Bac Thuy
Formation, northeastern Vietnam. This species
also occurs in the Spathian (Upper Olenekian)in Chios (Bender, 1970), Desli Caira, North
Dobrogea, Romania (Orchard et al., 2007a),the Salt Range, Pakistan (Sweet, 1970), Kashmir, India (Matsuda, 1983), Jabal Safra, Oman
(Orchard, 1995), Southern Jiangsu, China(Duan, 1987), and Guizhou, South China (Orchard et al., 2007b).
Triassospathodus symmetricus (Orchard, 1995)
Figs. 182–185, 186.1–186.3
Neospathodus cristagalli (Huckriede, 1958). Mosher,
1968, p. 930, pl. 115, fig. 1
Neospathodus triangularis (Bender, 1970). Sweet, 1970b,
pp. 253–254, pl. 1, figs. 7, 8; Perri and Andraghetti,
1987, p. 311, pl. 33, figs. 5a, b, c.
Neospathodus homeri (Bender, 1970). Mosher, 1973, p.
171, pl. 20, fig. 14; Goel, 1977, p. 1097, pl. 2, figs.
10, 11; Duan, 1987, pl. 2, figs. 8, 9; Cao and Wang,
1993, pl. 56, figs. 1, 2; Ji et al., 2011, p. 220, figs.
3.9a, b. c.
Neospathodus ex gr. homeri (Bender, 1970). Orchard,
1994, pl. 1, figs. 11, 15–18.
Neospathodus symmetricus Orchard, 1995, p. 120, figs.
2.6, 2.10–2.13, 2.18; Koike, 2004, p. 137, figs. 6.34–
6.38; Ji et al., 2011, figs. 3.5a, b, c.

Material examined: Two specimens,
MPC25542, 25543, from KC02-12, three
specimens, MPC25544–25546, from KC0214, and forty-three specimens, MPC25547–
25589, from KC02-15.
Description: Laterally compressed bladelike elements 0.41–0.87 mm in length, average
0.61 mm; 0.22–0.41 mm in height, average

0.33 mm; length to height ratio 1.6–2.7, average 1.9 for forty-eight specimens. Straight or
arcuate upper edge bears sub-traingular, pointed and fused denticles varying in number from10 to 18, average 13, erect and gradually reclined posteriorly. Basal margin slightly orstrongly bowed. Some specimens have posterior small denticles above terminal basal cavity. Several elements have a well-developed
lateral rib in middle part of element. Basalcavity concave, and exhibits various shapes:
circular, elliptical, sub-triangular, square, cordiform. Narrow furrow extends to anterior
end.
Remarks: The described specimens from
KC02-15 display a wide range of intraspecificvariation in the form of their denticulation,basal cavities, and basal margins.
Occurrence: Described specimens from
KC02-12, KC02-14 and KC02-15 within the
portion of the Triassospathodus symmetricus
Zone that includes the Tirolites cf. cassianus
beds (lowest Lower Spathian = lowest Upper
Olenekian) and Tirolites sp. nov. beds (Lower
Spathian = lower Upper Olenekian) in the Bac
Thuy Formation, northeastern Vietnam.
This species also occurs in the Spathian in
the Salt Range, Pakistan (Zone 9, Sweet,
1970b), the Werfen Formation, southern Alps,
Italy (Perri and Andraghetti, 1987), British
Columbia, Canada (Keyserlingites subrobustus
Zone, Mosher, 1973 and Orchard, 1994), Spiti,
India (Goel, 1977), the Prida Formation, Nevada (Subcolumbites beds and Neopopanoceras hangi Zone, Orchard, 1994), the Luolou
Formation, Qingyan Section, Guizhou, South
China (Neospathodus homeri Zone, Ji et al.,2011), and the Taho limestone, Southwest
Japan (Koike, 2004).
The FAD of Triassospathodus symmetricus occurs in the lowest Spathian, but its lastappearance datum (LAD) is unknown. The
exact range of this taxon must be clarified withrespect to its occurrence in other Spathianaged formations and detailed descriptions ofco-occurring species must be included.

Olenekian (Early Triassic) in northeastern Vietnam

255

Fig. 182. Triassospathodus symmetricus (Orchard, 1995). 1–4, MPC25542, from KC02-12. 5–7, MPC25543,
from KC02-12. 8–11, MPC25544, from KC02-14. 12–15, MPC25545, from KC02-14. 16–18, MPC25546,
from KC02-14. 19–21, MPC25547, from KC02-15. 22–24, MPC25548, from KC02-15. 25–27, MPC25549,
from KC02-15. 28–30, MPC25550, from KC02-15. 31–33, MPC25551, from KC02-15. 34–36, MPC25552,
from KC02-15. 37–39, MPC25553, from KC02-15. 40–42, MPC25554, from KC02-15.

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Fig. 183. Triassospathodus symmetricus (Orchard, 1995) from KC02-15. 1–3, MPC25555. 4–6, MPC25556.
7–9, MPC25557. 10–12, MPC25558. 13–15, MPC25559. 16–18, MPC25560. 19–21, MPC25561. 22–24,
MPC25562. 25–27, MPC25563. 28–30, MPC25564. 31–33, MPC25565. 34–36, MPC25566.

Olenekian (Early Triassic) in northeastern Vietnam

257

Fig. 184. Triassospathodus symmetricus (Orchard, 1995) from KC02-15. 1–3, MPC25567. 4–6, MPC25568.
7–9, MPC25569. 10–12, MPC25570. 13–15, MPC25571. 16–18, MPC25572. 19–21, MPC25573. 22–24,
MPC25574. 25–28, MPC25575. 29–31, MPC25576.

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Fig. 185. Triassospathodus symmetricus (Orchard, 1995) from KC02-15. 1–3, MPC25577. 4–6, MPC25578.
7–9, MPC25579. 10–12, MPC25580. 13–15, MPC25581. 16–18, MPC25582. 19–21, MPC25583. 22–23,
MPC25584. 24–26, MPC25585. 27–29, MPC25586. 30–32, MPC25587. 33–35, MPC25588.

Olenekian (Early Triassic) in northeastern Vietnam

259

Fig. 186. 1–3, Triassospathodus symmetricus (Orchard, 1995), MPC25589, from KC02-15. 4–5, Hadrodontina?
sp. indet. A, MPC25590, from BT01-07. 6–9, Hadrodontina? sp. indet. B, MPC25591, from BT02-02. 10–22,
Icriospathodus collinsoni (Solien, 1979). 10–13, MPC25592, from KC02-14. 14–16, MPC25593, from KC0214. 17–19, MPC25594, from KC02-15. 20–22, MPC25595, from KC02-15.

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Subfamily Uncertain
Genus Icriospathodus Krahl, Kauffmann,
Kozur, Richter, Foerster and Heinritzi, 1983
Type species: Neospathodus collinsoni Solien, 1979.
Icriospathodus collinsoni (Solien, 1979)
Figs. 186.10–186.22, 187–191, 192.1–192.6
Icriodus. Clark et al., 1964, pl. 60, figs. 1a, b.
Neospathodus sp. G. Sweet et al., 1971, pl. 1, fig. 13;
Buryi, 1979, p. 49, pl. 9, figs. 3a–c, pl. 18, figs. 4a, b.
Neospathodus collinsoni Solien, 1979, p. 302, pl. 3, figs.
10, 12–20.; Clark et al., 1979, pl. 1, figs. 11, 12;Duan, 1987, pl. 2, figs. 1–6; Cao and Wang, 1993, pl.
55, figs.12, 13.
Neospathodus? collinsoni Solien, 1979. Koike, 1981, pl.
1, figs. 42–44.
Spathoicriodus collinsoni Budurov, Sudar and Gupta,
1987, p. 175.
Spathoicriodus collinsoni (Solien, 1979). Koike, 1992, p.
357–361, figs. 12.1–12.42, 12.44, 12.47–12.50, 13.8–
13.37.
Icriospathodus collinsoni (Solien, 1979). Orchard, 1995,
p. 113, figs. 2.22–2.24; Nakazawa et al., 1994, pl. 1,
fig. 30; Lucas and Orchard, 2007, figs. 7.4–7.7, 7.13–
7.15; Ji et al., 2011, figs. 4.5a-c.
multielement apparatuses, Icriospathodus collinsoni (Solien, 1979). Orchard, 2005, p. 96, text-fig. 22.

Material examined: Two specimens,
MPC25592, 25593, from KC02-14, and fiftyfour specimens, MPC25594–25647, from
KC02-15.
Description: Blade-like robust elements
0.50–0.92 mm in length, average 0.64 mm;
0.20–0.36 mm in height, average 0.27 mm;
length to height ratio 1.4–2.9, average 2.0 for
fifty-six specimens, with rectangular generalprofile. Upper part of element consists ofpointed node-like and ridge-like denticles.
Prominent strong rib extended to posterior end
in the middle part of element, flanged laterally
above basal cavity. Lower margin straight orbowed at both anterior and posterior ends,
downturned prominently. Denticles, varying in
number from 10 to 18, average 12, change tospine or node-like form at both anterior andposterior ends, and exhibit biserial ribs or sin-

gle ridge across platform. Line of denticulation straight, or slightly or strongly curved tosinistral or dextral sides of element at posterior end. Some specimens have small pointed
denticles extended along the posterior margin.
Denticles show some variation in size andform. Ridge-like denticles widest in middle orslightly posterior part of element, gradually
decreasing to both anterior and posterior ends,
highest point situated in posterior one-fourth,and lowest in anterior end. Strongly concave
basal cavity exhibits various shapes: subround, triangular, square, parallelogram, pentagon. Some posterior margins branched or remarkably elongated to lateral side at posterior
end. Deep furrow extends from basal pit to anterior end.
Remarks: Koike (1992) demonstrated awide range of intraspecific variation in theplatform morphology and denticulation of
Spathoicriodus collinsoni (Solien, 1979)(= Icriospathodus collinsoni [Solien, 1979])
from the Taho limestone, Southwest Japan,
and consequently divided into three forms (α,β, γ) on the basis of the degree of developmentof its ridge-like denticles. Form α is marked
by having transverse ridge-like denticles on
the entire platform. Form β has narrow uniserial or a few biserial denticles on the middle
portion of the platform. Form γ has laterallycompressed or laterally rounded and tipped
denticles (lacking ridge-like denticles orpaired platform nodes) on the entire platform.
Form γ and other forms co-occur in Oman,Southwest Japan, and Idaho, Form γ occurs byitself in the Spathian of California (Orchard,1995). Orchard (1995) separated Form γ fromthe other forms based on their differences indenticulation and FAD (Form γ occurs earlier
than the other forms), and proposed a new
species, Neospathodus crassatus Orchard,
1995 (= I.? crassatus [Orchard, 1995]).
Occurrence: Described specimens from
KC02-14 and KC02-15 within the portion of
the Triassospathodus symmetricus Zone represented by the Tirolites sp. nov. beds (Lower

Olenekian (Early Triassic) in northeastern Vietnam

261

Fig. 187. Icriospathodus collinsoni (Solien, 1979) from KC02-15. 1–3, MPC25596. 4–6, MPC25597. 7–9,
MPC25598. 10–12, MPC25599. 13–15, MPC25600. 16–18, MPC25601. 19–21, MPC25602. 22–24,
MPC25603. 25–27, MPC25604. 28–30, MPC25605. 31–33, MPC25606. 34–36, MPC25607. 37–39,
MPC25608. 40–42, MPC25609.

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Fig. 188. Icriospathodus collinsoni (Solien, 1979) from KC02-15. 1–3, MPC25610. 4–6, MPC25611. 7–9,
MPC25612. 10–12, MPC25613. 13–15, MPC25614. 16–18, MPC25615. 19–21, MPC25616. 22–24,
MPC25617. 25–27, MPC25618. 28–30, MPC25619. 31–33, MPC25620. 34–36, MPC25621. 37–39,
MPC25622.

Olenekian (Early Triassic) in northeastern Vietnam

263

Fig. 189. Icriospathodus collinsoni (Solien, 1979) from KC02-15. 1–3, MPC25623. 4–6, MPC25624. 7–9,
MPC25625. 10–12, MPC25626. 13–15, MPC25627. 16–18, MPC25628. 19–21, MPC25629. 22–24,
MPC25630.

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Fig. 190. Icriospathodus collinsoni (Solien, 1979) from KC02-15. 1–3, MPC25631. 4–6, MPC25632. 7–9,
MPC25633. 10–12, MPC25634. 13–15, MPC25635. 16–18, MPC25636. 19–21, MPC25637. 22–24,
MPC25638.

Olenekian (Early Triassic) in northeastern Vietnam

265

Fig. 191. Icriospathodus collinsoni (Solien, 1979) from KC02-15. 1–3, MPC25639. 4–6, MPC25640. 7–9,
MPC25641. 10–12, MPC25642. 13–15, MPC25643. 16–18, MPC25644. 19–21, MPC25645.

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Fig. 192. 1–6, Icriospathodus collinsoni (Solien, 1979) from KC02-15. 1–3, MPC25646. 4–6, MPC25647. 7–9,
Icriospathodus? crassatus (Orchard, 1995), MPC25648, from KC02-15. 10–29, Icriospathodus? zaksi (Buryi,1979). 10–13, MPC25649, from KC02-08. 14–17, MPC25650, from KC02-10. 18–21, MPC25651, from
KC02-10. 22–25, MPC25652, from NT01-07. 26–29, MPC25653, from NT01-09. 30–32, Genus gen. indet.
A, MPC25654, from BT01-03.

Olenekian (Early Triassic) in northeastern Vietnam

267

Spathian = lower Upper Olenekian) in the Bac
Thuy Formation, northeastern Vietnam. This
species also occurs in the Lower Spathian in
Idaho (upper part of Zone 10 and Zone 11,
Sweet et al., 1971), the Thaynes Formation,
Utah (middle and upper part of Platyvillosus
Zone and Neospathodus collinsoni Zone, Solien, 1979), Nevada (Clark et al., 1964; Lucas
and Orchard, 2007), South Primorye (Tirolites
cassianus Zone, Buryi, 1979), the Taho limestone, Southwest Japan (Koike, 1981, 1992),
South China (Duan, 1987; Ji et al., 2011), andSvalvard (Hatleberg and Clark, 1984).
According to Sweet et al. (1971), Solien(1979), and Lucas and Orchard (2007), in
North America, I. collinsoni occurs in the Columbites beds and its FAD is placed slightly
above the Smithian/Spathian boundary (SSB),
which is indicated by the FAD of Platyvillosus
asperatus Clark, Sincavage and Stone. P.
asperatus has been reported only from thewestern part of Panthalassa and it co-occurs
with Ns. homeri (Bender, 1970) (= Triassospathodus homeri [Bender, 1970]) and Ns. triangularis (Bender, 1970) (= Novispathodus
triangularis [Bender, 1970]). In the Bac Thuy
Formation, I. collinsoni (KC02-14) co-occurs
with Columbites sp. indet. and its FAD isplaced slightly above the FAD of Tirolites cf.
cassianus (KC02-11), the ammonoid thatmarks the SSB. This fact agrees with other reports.

0.22 mm in height; 0.23 mm in width; length toheight ratio 2.4; length to width ratio 2.3, withrectangular lateral profile. Node-like denticles
total 11 in number, and contain one small posterior process. Cusp situated near posterior
end. Lower edge straight, slightly undulated
below cusp. Square basal cavity expanded at
posterior end with a deep pit. Furrow extends
from pit to anterior end
Remarks: The described specimen closely
resembles Icriospathodus collinsoni (Solien,1979) in its lateral and lower views, but itlacks the ridge-like denticles on its platform. It
also resembles I.? zaksi (Buryi, 1979), but thewidth of the element is smaller.
Occurrence: Described specimen from
KC02-15 within the portion of the Triassospathodus symmetricus Zone represented by
the Tirolites sp. nov. beds (Lower Spathian = lower Upper Olenekian) in the Bac Thuy
Formation, northeastern Vietnam. This species
also occurs in the Lower Spathian in Southwest Japan (Koike, 1992), Oman, Idaho andCalifornia (Orchard, 1995), and South China(Ji et al., 2011).

Icriospathodus? crassatus (Orchard, 1995)

Material examined: One specimen,
MPC25469, from KC02-08, two specimens,
MPC25450, 25451, from KC02-10, one specimen, MPC25452, from NT01-07, and one
specimen, MPC25453, from NT01-09.
Description: Robust segminate elements
0.35–0.65 mm in length, average 0.48 mm;
0.25–0.30 mm in height, average 0.28 mm;
0.23–0.36 mm in width, average 0.27 mm;
length to height ratio 1.3–2.1, average 1.7;
length to width ratio 1.5–2.1, average 1.9 forfive specimens, with rectangular lateral pro-

Fig. 192.7–192.9
Spathoicriodus collinsoni (Solien, 1979). Koike, 1992, p.
357, figs. 12.1–12.12, 12.43, 12.45–12.46, 12.51–
12.53, 13.1–13.7.
Neospathodus crassatus Orcahrd, 1995, p. 120, figs. 2.19,
2.25–2.57, Ji et al., 2011, figs. 4.2a-c.
Icriospathodus? crassatus (Orchard, 1995). Orchard,
2007a, p. 60. fig. 2.

Material examined: One specimen,
MPC25648, from KC02-15.
Description: Robust rectangular-shaped
segminate element 0.52 mm in length;

Icriospathodus? zaksi (Buryi, 1979)
Fig. 192.10–192.29
Neospathodus zaksi Buryi, 1979, p. 60, pl. 18, figs. 3a, b.
Neospathodus triangularis (Bender, 1970). Perri and Andraghetti, 1987, p. 311, pl. 33, figs. 1–4.
Icriosapthodus? zaksi (Buryi, 1979). Orchard, 2007a, p.
105, fig. 2.

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file. Short, robust, triangular-shaped denticles
vary in number from 7 to 12, average 9, gradually becomes smaller towards both anterior
and posterior ends, extremely small at posterior end. Terminal processes in some specimens
turn to the sinistral side. Cusp situated in posterior one-third, except for MPC25651. Specimen (MPC25650) has terminal processes
along the posterior margin of element. In lateral view, prominent lateral rib developed in
middle part of element, becoming strong posteriorly. Lower margin straight or curved
slightly upward in anterior-most part, downcurved or slightly deflected upward in posterior part. Sub-rounded or rectangular asymmetrical basal cavity strongly concave. Deep furrow extends from the basal pit to anterior end.
Remarks: The described specimens, which
include a juvenile (MPC25649), show a broad
morphological variation in the platform. Specifically, one specimen (MPC25650) has a laterally expanded element and terminal process
at the posterior end. Koike (1992) reported
similar morphological variations in Icriospathodus collinsoni (Solien, 1979) and I.? crassatus (Orchard, 1995).
Occurrence: Described specimens from
KC02-08, KC02-10, NT01-07 and NT01-09
within the portion of the Novispathodus pingdingshanensis Zone that represents the Xenoceltites variocostatus beds (Upper Smithian = upper Lower Olenekian) in the Bac Thuy
Formation, northeastern Vietnam. This species
also ranges from the Upper Smithian (upper
Lower Olenekian) to the Lower Spathian(lower Upper Olenekian) in South Primorye,
Russia (upper part of Anasibirites nevolini
Zone and lower part of Tirolites cassianus
Zone, Buryi, 1979), and the Werfen Formation, southern Alps, Italy (Perri and Andraghetti, 1987).

Order Prioniodinida Sweet, 1988
Familly Ellisoniidae, Clark, 1972
Genus Hadrodontina Staesche, 1964
Type species: Hadrodontina anceps Staesche, 1964.
Hadrodontina? sp. indet. A
Fig. 186.4, 186.5

Material examined: one specimen,
MPC25590, from BT01-07.
Remarks: The specimen is characterized
by an arcuatiform element with robust denticles that are reclined posteriorly, and a cuspthat is longer and larger than the other denticles. Assignment of this specimen to
Hadrodontina is uncertain, but its arched form
with strongly inclined pole-like processes andnon-expanded basal cavity suggest that this element belongs to the family Ellisoniidae.
Occurrence: Described specimen fromBT01-07 in the portion of the Novispathodus
ex gr. waageni Zone between the Flemingites
rursiradiatus beds (lowest Middle Smithian = middle Lower Olenekian) and Urdycerastulongensis beds (lower Middle Smithian = middle Lower Olenekian) in the Bac Thuy
Formation, northeastern Vietnam.
Hadrodontina? sp. indet. B
Fig. 186.6–186.9

Material examined: One specimen,
MPC25591, from BT02-02.
Description: Angulate-like arcuatiform element 1.13 mm in length; 0.82 mm in height.
Platform strongly bowed in lateral view, sigmoidal in upper view and V-shaped in lower
view. Node-like denticles arranged in threerows: 13 on each side, with 6 in the center, inclination and size gradually increase posteriorly. Largest process situated in middle part ofelement, four times larger than other denticles.
Remarks: The assignment of this specimen
to Hadrodontina is uncertain, but it is somewhat similar to the specimen of Hadrodontina

Olenekian (Early Triassic) in northeastern Vietnam

anceps Staesche, 1964 described by Perri andAndraghetti (1987, pl. 33, fig. 1a), in having
three rows of denticles on the platform, butdiffers by its pole-like denticles arranged in aradial fashion on the symmetrical platform.
Occurrence: Described specimen fromBT02-02 within the portion of the Novispathodus ex gr. waageni Zone represented by the
Urdyceras tulongensis beds (lower Middle
Smithian = middle Lower Olenekian) in the
Bac Thuy Formation, northeastern Vietnam.
Incertae sedis
Genus gen. indet. A
Fig. 192.30–192.32

Material examined: One specimen,
MPC25654, from BT01-03
Remarks: The completely discrete denticles, which total 5 in number, and the lack ofan expanded basal cavity, indicate that this element belongs to the P2 element of an uncertain species.
Occurrence: Described specimen fromBT01-03 within the portion of the Novispathodus ex gr. waageni Zone that represents theFlemingites rursiradiatus beds (lowest Middle
Smithian = middle Lower Olenekian) in the
Bac Thuy Formation, northeastern Vietnam.
Genus gen. indet. B
Fig. 193.1–193.4

Material examined: One specimen,
MPC25655, from BT01-06
Remarks: This specimen is similar to Furnishius triserratus Clark, 1959 in its branchedanterior part, but the latter has double lines ofdenticles on both anterior branches. The lateralform of this specimen is close to species of thegenus Neospathodus, but such an assignment
would be uncertain based on only one specimen.
Occurrence: Described specimen fromBT01-06 within the portion of the Novispathodus ex gr. waageni Zone between the Flemingites rursiradiatus beds (lowest Middle Smithi-269

an = middle Lower Olenekian) and Urdycerastulongensis beds (lower Middle Smithian = middle Lower Olenekian) in the Bac Thuy
Formation, northeastern Vietnam.
Genus gen. indet. C
Fig. 193.5–193.7

Material examined: One specimen,
MPC25656, from BT01-06
Remarks: This specimen is similar to Discretella in having discrete denticles and arounded basal cavity, but the more robust andstrongly laterally curved posterior part of theelement makes it difficult to determine an assignment.
Occurrence: Described specimen fromBT01-06 within the portion of the Novispathodus ex gr. waageni Zone between the Flemingites rursiradiatus beds (lowest Middle Smithian = middle Lower Olenekian) and Urdycerastulongensis beds (lower Middle Smithian = middle Lower Olenekian) in the Bac Thuy
Formation, northeastern Vietnam.
Genus gen. indet. D
Fig. 193.8–193.12

Material examined: One specimen,
MPC25657, from BT01-07, and one specimen, MPC25658, from PK01-02.
Remarks: The specimens have a large reclined cusp on a relatively short platform.
Specimen MPC25658 has several processes
on both the anterior and posterior sides of thecusp and a strongly expanded platform, whencompared with specimen MPC25657. Theseelements probably exhibit different growthstages.
Occurrence: Described specimen fromBT01-07 within the portion of the Novispathodus ex gr. waageni Zone between the Flemingites rursiradiatus beds (lowest Middle Smithian = middle Lower Olenekian) and Urdycerastulongensis beds (lower Middle Smithian = middle Lower Olenekian), and from
PK01-02 within the portion of the Novispatho-

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Fig. 193. 1–4, Genus gen. indet. B, MPC25655, from BT01-06. 5–7, Genus gen. indet. C, MPC25656, fromBT01-06. 8–12, Genus gen. indet. D. 8–9, MPC25657, from BT01-07. 10–12, MPC25658, from PK01-02.
13–21, Genus gen. indet. E. 13–15, MPC25659, from BT02-01. 16–18, MPC25660, from BT02-01. 19–21,
MPC25661, from BT03-01. 22–24, Genus gen. indet. F, MPC25662, from BT02-03. 25–27, Genus gen. indet.
G, MPC25663, from KC01-05. 28–30, Genus gen. indet. H, MPC25664, from PK01-02.

Olenekian (Early Triassic) in northeastern Vietnam

dus ex gr. waageni Zone represented by theOwenites koeneni beds (middle Middle Smithian = middle Lower Olenekian) in the Bac
Thuy Formation, northeastern Vietnam.
Genus gen. indet. E
Fig. 193.13–193.21

Material examined: Two specimens,
MPC25659, 25660, from BT02-01, and one
specimen, MPC25661, from BT03-01.
Remarks: The specimens are characterized
by a laterally curved element with strongly reclined denticles and a large cusp situated in
the posterior one-third. These features indicatethat the specimens probably belong to the P2
element of the family Gondolellidea.
Occurrence: Described specimens collected from BT02-01 within the portion of the Novispathodus ex gr. waageni Zone represented
by the Flemingites rursiradiatus beds (lowest
Middle Smithian = middle Lower Olenekian),and from BT03-01 within the portion of theNovispathodus ex gr. waageni Zone represented by the Owenites koeneni beds (middle Middle Smithian = middle Lower Olenekian) in the
Bac Thuy Formation, northeastern Vietnam.
Genus gen. indet. F
Fig. 193.22–193.24

Material examined: One specimen,
MPC25662, from BT02-03.
Remarks: The specimen lacks a part of its
lower side, but discrete needle-like denticles
on the upper side are similar to those of the P2
element of species in the subfamily Mulleninae.
Occurrence: Described specimen fromBT02-03 within the portion of the Novispathodus ex gr. waageni Zone represented by the
Leyeceras horizon of the Owenites koeneni
beds (middle Middle Smithian = middle Lower
Olenekian) in the Bac Thuy Formation, northeastern Vietnam.

271

Genus gen. indet. G
Fig. 193.25–193.27

Material examined: One specimen,
MPC25663, from KC01-05.
Remarks: This specimen exhibits a “V”
shaped platform with laterally compressedshort denticles in the upper view. An affiliation
assignment of this element is not possible.
Occurrence: Described specimen from
KC01-05 within the portion of the Novispathodus ex gr. waageni Zone below the Owenites
koeneni beds (middle Middle Smithian = middle Lower Olenekian) in the Bac Thuy Formation, northeastern Vietnam.
Genus gen. indet. H
Fig. 193.28–193.30

Material examined: One specimen,
MPC25664, from PK01-02.
Remarks: This bowed specimen lacks theanterior part of element. Discrete long processes and a slightly expanded basal cavity
demonstrate that this element belongs to the P2
element of species in the family Gondolellidea.
Occurrence: Described specimen from
PK01-02 within the portion of the Novispathodus ex gr. waageni Zone represented by theOwenites koeneni beds (middle Middle Smithian = middle Lower Olenekian) in the Bac
Thuy Formation, northeastern Vietnam.
Ostracods (by G. Tanaka,T. Komatsu and T.
Maekawa)
Most of the ostracod specimens recoveredby acid treatment of limestone samples haveconsisted of incomplete, fragmented, orcrushed valves or carapaces, but six species
belonging two genera have been recognized
and several well-preserved specimens are described in this paper. The morphological terms
used are based on the work of Moore (1961).
Abbreviations: L = length, H = height, W =width, LV = left valve, RV = right valve, C =carapace.

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Institution abbreviation: MPC = Micro­
paleo­nt­ology Collection, National Museum of
Nature and Science, Tsukuba.
Phylum Arthropoda Latreille, 1829
Subphylum Crustacea Brünnich, 1772
Class Ostracoda Latreille, 1802
Order Podocopida Sars, 1866
Suborder Cypridocopina Jones, 1901
Superfamily Cypridoidea Baird, 1845
Family Candonidae Kaufmann, 1900
Genus Paracypris Sars, 1866
Type species: Paracypris polita Sars, 1866.
Paracypris vietnamensis
Tanaka and Komatsu sp. nov.
Figs. 194, 195

Type specimens: Holotype, MPC25845;
paratypes, seven specimens, MPC25846–
25852. Type specimens were collected fromBR01-04.
Diagnosis: LV larger than RV, overlapping
along anterior to posterior margin via dorsal
margin. Posterior margin protruded with small
curvature and protruding toward postero-ventral direction.
Etymology: After Vietnam, where the typespecimens are from.
Description: Valve sub-trapezoidal in lateral view and anterior end higher than posterior end (Figs. 194.1, 195.1). LV larger than RV,
overlapping along anterior to posterior margin
via dorsal margin (Fig. 195.3). Anterior cardinal angle obtuse at about 150 degrees, posterior cardinal angle obtuse at about 140 degrees.
In lateral view, lower half of anterior marginacutely rounded and protruded antero-ventrally; dorsal margin straight, inclined toward posterior; ventral margin sinuate and concave at
middle; one-third of lower posterior margin
protruded, with small curvature and protruding
in a postero-ventral direction, and two-thirdsof upper posterior margin broadly arched in
RV (Fig. 195.3), broadly arched postero-dorsally in LV (Fig. 195.1). Surface of C finely

reticulated (Figs. 194.3, 195.4), probably
shrinking after diagenesis or acid-treatment.
Reticulation probably due to shrinkage of thechitinous membrane, because same reticulation is observed on internal surface of thevalve (Figs. 194.7, 194.8, 195.7). Extremely
thin valve (1.5–5.0 μm) (Figs. 194.5, 194.7,
194.8, 195.2, 195.5, 195.7). Normal pore canals (Fig. 194.3) are sporadically distributed,
and diameter of each is about 1.5 μm. In dorsal
view, bullet-shaped carapace, LV larger thanRV, anterior end protruding more than posterior end. In internal view, straight hinge line
(Fig. 194.6) runs parallel to dorsal margin(Fig. 194.6) in LV. Sulcus of RV (Fig. 195.6)
fit straight hinge bar of RV. Adont hinge. Duplicature developed in antero-dorsal to postero-dorsal areas along ventral area, broadly inantero-ventral and postero-ventral areas (Figs.
194.6, 194.7, 195.6, 195.7). Adductor muscle
scars not observed. Sexual dimorphism unknown.
Discussion: Paracypris vietnamensis sp.
nov. is similar to Paracypris jinyaensis
Crasquin-Soleau, 2006 (in Crasquin-Soleau etal., 2006) from the Early Triassic (Olenekian)strata of the Fengshan area, Guangxi Province,
South China, but differs from it in terms of its
postero-ventrally bended caudal process, its
more rounded lateral outline, and its slightly
sinuated ventral margin. Paracypris vietnamensis sp. nov. resembles Paracypris sp. reported by Wei (1981) from the Middle Triassic
Leikoupo Formation of Weiyuan of Sichuan,South China, but can be distinguished from
Paracypris sp. by its small carapace and by its
widely arched posterior margin and morerounded lateral outline in the RV. The new
species is similar to Paracypris? scalaris Wei,
1981 from the Early Triassic Jialingjiang Formation of Sichuan, South China, but differsfrom the latter in terms of its more acute posterior margin, the tendency for its dorsal margin to be inclined toward the posterior, and its
more blunt anterior and posterior cardinal angles.

Olenekian (Early Triassic) in northeastern Vietnam

273

Fig. 194. Paracypris vietnamensis Tanaka and Komatsu sp. nov., from BR01-04. 1, 3, MPC25848, paratype. 1,
Left lateral view of C. 3, Enlargement of mid-posterior area. 2, MPC25849, paratype, ventral view of internalvalve of RV. 4, MPC25850, paratype, lateral view of RV. 5, MPC25851, paratype, lateral view of RV. 6–8,
MPC25852, paratype. 6, Internal view of LV. 7, Enlargement of anterior area. 8, Magnified antero-dorsal margin.

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 195. Paracypris vietnamensis Tanaka and Komatsu sp. nov., from BR01-04. 1–2, MPC25846, paratype. 1,
External view of LV. 2, Enlargement of antero-ventral area. 3–5, MPC25845, holotype. 3, Right lateral viewof C. 4, Enlargement of mid-dorsal area. 5, Magnification of dorso-posterior area. 6–7, MPC25847, paratype.
6, Internal view of partly broken RV. 7, Enlagement of postro-ventral area.

Olenekian (Early Triassic) in northeastern Vietnam

Occurrence: Described specimens fromBR01-04 within the Novispathodus pingdingshanensis Zone below the Xenoceltites variocostatus beds (Upper Smithian = upper Lower
Olenekian) in the Bac Thuy Formation, northeastern Vietnam.
Paracypris sp. indet. A
Figs. 196.1–196.5, 197.3–197.5, 197.7, 197.8

Material examined: Five specimens,
MPC25853–25857, from BR01-04.
Discussion: This species is similar to P.
jinyaensis
Crasquin-Soleau,
2006(in
Crasquin-Soleau et al., 2006) from the Early
Triassic (Olenekian) strata of the Fengshanarea, Guangxi Province, South China, but differs from it in the straight upper half of its anterior margin, its more acute caudal process,and its lack of an evenly rounded anterior margin. Paracypris sp. indet. A resembles Paracypris sp. reported by Wei (1981) from the Middle Triassic Leikoupo Formation of Weiyuan
in Sichuan, South China, but it can be distinguished from P. sp. by its small carapace, ventrally arched anterior margin, and more rounded posterior margin. This species is similar to
Paracypris badongensis Guan, 1985 from theMiddle Triassic Baotahe Formation, Hubei
Province, South China, but differs from it inthat it has a more protruded caudal process, astraight dorsal margin, and a more inflated carapace from the dorsal view.
Occurrence: Described specimens fromBR01-04 within the Novispathodus pingdingshanensis Zone below the Xenoceltites variocostatus beds (Upper Smithian = upper Lower
Olenekian) in the Bac Thuy Formation, northeastern Vietnam.
Paracypris sp. indet. B
Figs. 196.6, 196.7, 197.6

Material examined: Two specimens,
MPC25858–25859, from BR01-04.
Discussion: This species is similar to
Paracypris sp. Wei, 1981 from the Middle Tri-275

assic Leikoupo Formation, Sichuan Province,
South China, but differs from it in that it has abroadly arched anterior margin, higher lateraloutline, and sinuated ventral margin.
Occurrence: Described specimens fromBR01-04 within the Novispathodus pingdingshanensis Zone below the Xenoceltites variocostatus beds (Upper Smithian = upper Lower
Olenekian) in the Bac Thuy Formation, northeastern Vietnam.
Paracypris sp. indet. C
Fig. 197.1, 197.2

Material examined: One specimen,
MPC25860, from BR01-04.
Discussion: This species is similar to
Paracypris? scalaris Wei, 1981 from the Early
Triassic Jialingjiang Formation, Sichuan Province, South China, but it differs from the latterin terms of its broadly arched dorsal margin,
evenly arched anterior margin, and higher lateral outline.
Occurrence: Described specimens fromBR01-04 within the Novispathodus pingdingshanensis Zone below the Xenoceltites variocostatus beds (Upper Smithian = upper Lower
Olenekian) in the Bac Thuy Formation, northeastern Vietnam.
Superfamily Bairdiacea Sars, 1887
Family Bairdiidae Sars, 1887
Genus Bairdia McCoy, 1844
Type species: Bairdia curia McCoy, 1844.
Bairdia sp. indet. A
Fig. 198.3–198.5

Material examined: One specimen,
MPC25862, from NT01-08.
Discussion: This species is similar to Bairdia wailiensis Crasquin-Soleau, 2006 (inCrasquin-Soleau et al., 2006) from the Early
Triassic (Olenekian) strata of the Jinya/Waili
section, Guangxi Province, South China, butdiffers from it in the more steeply inclined

276

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 196. 1–5, Paracypris sp. indet. A from BR01-04. 1, 2, MPC25853. 1, External view of LV. 2, Enlargementof broken part of anterior area, showing outer and inner shells. 3–5, MPC25854. 3, Right lateral view of C. 4,
Enlargement of dorsal margin. 5, Magnified broken area of postero-dorsal margin. 6, 7, Paracypris sp. indet.
B, MPC25858 from BR01-04. 6, Fragment of internal view of RV. 7, Enlargement of postero-ventral area,
showing duplicature.

Olenekian (Early Triassic) in northeastern Vietnam

277

Fig. 197. 1, 2, Paracypris sp. indet. C, MPC25860 from BR01-04. 1, External view of RV. 2, Enlargement ofcentral area showing attached diatom-like organism. 3–5, 7, 8, Paracypris sp. indet. A from BR01-04. 3, 4,
MPC25855. 3, Internal view of LV. 4, Close-up of postero-ventral area. 5, MPC25856, dorsal view of C. 7–8,
MPC25857. 7, External view of LV. 8, Enlargement of mid-ventral area, showing tube-like structure (center ofimage). 6, Paracypris sp. indet. B, MPC25859, from BR01-04, internal view of RV. im: inner margin, LV: left
valve, npc: normal pore canal, RV: right valve, su: sulcus.

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 198. 1, 2, Bairdia sp. indet. B, MPC25861, from NT01-09. 1, Internal view of RV. 2, External view. 3–5,
Bairdia sp. indet. A, MPC25862, from NT01-08. 3, Right lateral view of C. 4, Dorsal view of C. 5, Left lateral view of C.

upper half of the posterior margin, more
broadly arched dorsal margin, and sinuatedventral margin.
Occurrence: Described specimens fromNT01-08 within the Novispathodus pingdingshanensis Zone represented by the Xenoceltites variocostatus beds (Upper Smithian = upper Lower Olenekian) in the Bac Thuy
Formation, northeastern Vietnam.
Bairdia sp. indet. B
Fig. 198.1, 198.2

Material examined: One specimen,
MPC25861, from NT01-09.
Discussion: This specimen is juvenile because of the presence of a weakly developed
inner margin. This species is similar to Bairdia
sp. Wei, 1981 from the Early Triassic Jialingjiang Formation, Sichuan Province, South
China, but differs from the latter in that it has
a longer upper half of anterior margin, broadly
arched anterior margin, and longer dorsal margin.
Occurrence: Described specimen fromNT01-09 within the Novispathodus pingdingshanensis Zone represented by the Xenoceltites variocostatus beds (Upper Smithian =upper Lower Olenekian) in the Bac Thuy For-mation, northeastern Vietnam.
Radiolarians (by O. Takahashi and Y.
Miyake)Systematic descriptions are basically following the classification by De Wever et al.
(2001).
Institution abbreviations: TGU = Tokyo
Gakugei University.
Subclass Radiolaria Müller, 1858
Superorder Polycystina Ehrenberg, 1838,
emend Riedel, 1967
Order Entactinaria Kozur and Mostler, 1982
Family Tetrentactiniidae Kozur and Mostler,
1979
Genus Multisphaera Nazarov and Afanasieva,
2000, emend Dumitrica, 2011
Type species: Multisphaera impersepta
Nazarov and Afanasieva, 2000.
Remarks: The genus Multisphaera was
first described by Nazarov and Afanasieva in
Afanasieva (2000) from the Lower Permian
Russian Platform. According to the emended
description by Dumitrica (2011), Multisphaera
possesses four or five concentric latticespheres, which originated from an eccentricOlenekian (Early Triassic) in northeastern Vietnam

four-rayed initial spicule, consisting of a double medullary shell, a single cortical shell, andone or two intermediary shells. The initial
spicule has a very short median bar and fourspines arranged tetrahedrally. Based on its
morphological features, especially the tetrahedral arrangement of the initial spicule, Dumitrica (2011) transferred the genus to the family
Tetrentactiniidae.
Multisphaera triassorobusta Takahashi, sp. nov.
Fig. 199

Material examined: Holotype, TGU 8717
(Fig. 199.1), from KC02-10. Seven specimens,
TGU 8604, 8626, 8705, 8714, 8715, 8717,
8718, from KC02-10, seven specimens, TGU
9001, 9010, 9013, 9207, 9209, 9210, 9216,
from NT01-05, and three specimens, TGU
8907, 8911, 8913, from NT01-07.
Diagnosis: Large robust concentric shell,
comprising two medullary, one intermediary,and one cortical shells with up to about 15
three-bladed radial spines. Radial spines proximally cylindrical become three-bladed outside second medullary shell and increase theirbreadth distally up to the cortical shell.
Etymology: According to its occurrence inTriassic beds and the Latin noun robustus (robust) indicating its robust form.
Description: Fully grown specimens possess four concentric spheres comprising two
medullary shells, one intermediary shell, andone cortical shell with up to about 15 threebladed radial spines of uniform size and distribution. Inner medullary (1st) shell sphericaland with small regularly arranged simple
pores, approximately 20 on the half sphere.
Outer medullary (2nd) shell also spherical andcomposed of an irregular network of very thindelicate anastomosing bars that sometimes has
a sponge-like appearance. Between first andsecond medullary shell the radial spines arecylindrical. They become three-bladed outside
second medullary shell and increase theirbreadth distally up to the cortical shell. Out-279

side it they have not been observed because allof them are broken off. Numerous thorns or
cylindrical thin short spines arise from the surface of the outer medullary shell. They may
stop inside the space of the intermediary shellor may touch the wall of the latter when wellpreserved. Intermediary (3rd) shell composedof an irregular, delicate, anastomosing lacelike network of very thin bars; an almost identical texture is observed on the outer medullary shell. Cortical (4th) shell large, robust,rough-surfaced and composed of a very irregular loose spongy framework.
Measurements (3–5 specimens): Diameterof cortical shell 311–353 μm (mean =329.7 μm); diameter of intermediary shell
207–225 μm (mean = 216.0 μm); diameter ofouter medullary shell 92–116 μm (mean =105.8 μm); and diameter of inner medullaryshell 27–35 μm (mean = 31.2 μm).
Remarks: The observed specimens of thisspecies were generally broken. Although thetetrahedral initial spicule allowed emendationof the diagnosis of the genus (Dumitrica,2011) was not visible because of poor preservation, the set of several fragmentary imagesof this species shows all the other diagnostic
features of the genus Multisphaera such as:
double medullary shell, connected to the intermediary and cortical shells through about 15
three-bladed radial spines, which are thin andcylindrical between first and second medullaryshells and three-bladed outside it. Also thestructure of the intermediary shell resembles
that of the type species of the genus Multisphaera. Multisphaera triassorobusta sp. nov.
differs from Multisphaera impersepta Nazarov
and Afanasieva, 2000 in having fewer radial
spines and robust cortical shell.
Discussion: The genus Multisphaera has
been represented until present only by its typespecies (M. impersepta) and considered tooccur only in the Lower Permian. M. triassorobusta sp. nov., found in the Lower Triassic(upper Smithian), would prove that the genus
Multisphaera crossed the P–T crisis. Although

280

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig 199. Multisphaera triassorobusta Takahashi, sp. nov. 1, TGU 8717, holotype, from KC02-10. 2, TGU 8714,
from KC02-10. 3, 5, TGU 8705, from KC02-10. 4, TGU 9210, from NT01-05. 6, TGU 8626, from KC02-10.
Scale bars = 100 μm (1–4), 50 μm (5), 20 μm (6).

Olenekian (Early Triassic) in northeastern Vietnam

the family Tetrentactiniidae lineage has beensuggested to have a long gap between theLower Permian (Afanasieva, 2000) and Upper
Jurassic (Dumitrica and Zügel, 2000; Dumitrica, 2011), M. triassorobusta sp. nov. probably
fills partly the gap between the Permian andJurassic genera of this family. It might suggestthat the radiolarians bearing tetrahedrally arranged initial spicule represent a single family
during this period at least, although Dumitrica(2013) erected a new family for the Jurassic
genera with tetrahedral spicule.
Occurrence: Described specimens fromNT01-05, NT01-07 and KC02-10 within theNovispathodus pingdingshanensis Zone represented by the Xenoceltites variocostatus beds
(Upper Smithian = upper Lower Olenekian) in
the Bac Thuy Formation, northeastern Vietnam.
Family Spongentactiniidae Nazarov, 1975
(syn: Retentactiniinae Won, 1997)
Genus Retentactinia Won, 1997
Type species: Retentactinia repleta Won,
1997.
Remarks: According to Won (1997), themost characteristic feature of the genus Retentactinia is having a network frame (N-frame)
structure. This structure appears as an innershell and is clearly separated from the spongy
tissue of the outer shell. The N-frame is connected directly to the inner surface of the outershell by six rays of the initial spicule. This
genus differs from the genus Spongentactinia
Nazarov, 1975 in having the N-frame structure.
Retentactinia? kycungensis Takahashi, sp. nov.
Fig. 200

Material examined: Holotype, TGU 9118
(Fig. 200.1), from NT01-05. Eight specimens,
TGU 8606, 8627, 8632, 8702, 8703, 8712,
8805, 8808, from KC02-10, and eight specimens, TGU 9015, 9020, 9021, 9108, 9113,
9118, 9208, 9212, from NT01-05.

281

Diagnosis: Moderately sized, loose
spongy spinulate shell with six long, proximally three-bladed but distally cylindrical radial spines. Apophyses forming an N-frame
structure.
Etymology: The species is named after the
Ky Cung River, where the uppermost part ofthe Bac Thuy Formation is exposed and from
where the radiolarian-bearing limestone samples come.
Description: Test spherical, consisting ofthin uniform spongy tissue. Surface of theshell consisting of an irregular and loose
spongy framework with numerous microthorns. Six long, straight, proximally threebladed but distally cylindrical radial spines
asymmetrically arranged. They are unequal inlength, one or two being slightly longer.
Spines directly connected to the six rays of theinitial spicule that has a short median bar.
Apophyses of the species forming an N-frame
structure.
Measurements (8 specimens): Diameter ofshell 116–156 μm (mean = 138.0 μm); length of
apical spine 100–156 μm (mean = 131.1 μm);
length of other spines 95–116 μm (mean =101.8 μm).
Remarks: The shell texture and the frameof the internal network of Retentactinia? kycungensis sp. nov. resemble those of Retentactinia repleta Won, 1997, the type species of
the genus. However, our species differs from
R. repleta in having six cylindrical long spines
connected to the N-frame.
Occurrence: Described specimens fromNT01-05 and KC02-10 within the Novispathodus pingdingshanensis Zone represented by
the Xenoceltites variocostatus beds (Upper
Smithian = upper Lower Olenekian) in the Bac
Thuy Formation, northeastern Vietnam.
Retentactinia? parvisphaera Takahashi, sp. nov.
Fig. 201

Material examined: Holotype, TGU 9116
(Fig. 201.1), from NT01-05. Three specimens,

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Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 200. Retentactinia? kycungensis Takahashi, sp. nov. 1, TGU 9118, holotype, from NT01-05. 2, TGU 8808,
from KC02-10. 3, TGU 9021, from NT01-05. 4, TGU 8606, from KC02-10. 5, TGU 9020, from NT01-05. 6,
TGU 8627, from KC02-10. Scale bars = 100 μm (1, 2, 4), 50 μm (3, 5, 6).

Olenekian (Early Triassic) in northeastern Vietnam

283

Fig. 201. Retentactinia? parvisphaera Takahashi, sp. nov. 1, TGU 9116, holotype, from NT01-05. 2, TGU 8607,
from KC02-10. 3, TGU 8816, from KC02-10. 4, TGU 8819, from KC02-10. 5, TGU 9213, from NT01-05. 6,
TGU 9101 from NT01-05. Scale bars = 100 μm.

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Shigeta, Komatsu, Maekawa and Dang (eds.)

TGU 8607, 8616, 8819, from KC02-10, ten
specimens, TGU 9007, 9014, 9101, 9114,
9116, 9117, 9202–9204, 9213, from NT01-05,
and five specimens, TGU 8903, 8908–8910,
8912, from NT01-07.
Diagnosis: Small spherical shell, consisting of a coarse fragile meshwork with six
short conical spines. Spines robust, connected
to initial spicule with very short median bar.
Apophyses forming an N-frame structure.
Etymology: The Latin adjective parvus(small) and the noun sphaera (sphere), indicating its small size and spherical form.
Description: Test small and spherical, consisting of a coarse or middle coarse meshwork
and six spines. In some specimens, a finespongy tissue covers partly the coarse meshwork. Spines are robust and arranged asymmetrically. They are conical but slightly threebladed proximally and connected to the six
thick rays of the initial spicule that has a very
short median bar. The four thick, straight, longer rays of the initial spicule arise from near
the midpoint of the shell; two short rays also
arise from the N-framed inner structure of theshell.
Measurements (8 specimens): Diameter ofshell 87–126 μm (mean = 111.0 μm); length ofspines 58–97 μm (mean = 74.2 μm).
Remarks: The genus Retentactinia has aspongy shell with weakly developed spines,
except for Retentactinia interreticulata Won,
1997, which possesses robust three-bladed radial spines. Retentactinia? parvisphaera sp.
nov. differs from other Retentactinia species inhaving a very coarse and fragile meshwork on
the shell surface and small, straight, but robust
spines.
Occurrence: Described specimens fromNT01-05, NT01-07 and KC02-10 within theNovispathodus pingdingshanensis Zone represented by the Xenoceltites variocostatus beds
(Upper Smithian = upper Lower Olenekian) in
the Bac Thuy Formation, northeastern Vietnam.

Genus Plenoentactinia Won, 1997
Type species: Plenoentactinia sexangula
Won, 1997.
Plenoentactinia? terespongia Takahashi, sp. nov.
Fig. 202

Material examined: Holotype, TGU 8719
(Fig. 202.2), from KC02-10. Four specimens,
TGU 8620, 8621, 8701, 8706, from KC02-10,
nine specimens, TGU 9003, 9004, 9006,
9017–9019, 9104, 9105, 9107, from NT01-05,
and one specimen, TGU 8904, from NT01-07.
Diagnosis: Moderately sized, thick nonlayered spongy shell with eight long, cylindrical slender spines. A six-rayed initial spiculewith a short median bar.
Etymology: The Latin adjective teres (fine,smooth) and the noun spongia (sponge) indicate its compact spongy tissues of the shell.
Description: Test spherical, spongy, andnon-layered with eight slender, cylindrical radial spines. Size of the test relatively variable;
however, the inner and superficial structure of
the shell and the arrangement of the main
spines have a similar development within thespecies. Single unlayered shell consisting ofvery compact, thick spongy tissue and witheight long radial spines of uniform length andshape. Pores on the inner surface of the shellcharacteristically larger and more irregular inshape than those on the outer surface. A sixrayed initial spicule with a short median bar
was observed in some specimens. This meansthat some spines are not prolongation of the
spicule rays.
Measurements (5 specimens): Diameter ofshell 139–170 μm (mean = 153.7 μm); length ofspines 108–164 μm (mean = 140.8 μm).
Remarks: Plenoentactinia? terespongia sp.
nov. differs from the species Won (1997) assigned unquestionably to this genus in having
the spines circular in cross section and may becompared only with Plenoentactinia? abstrusa(Aitchison, 1993) (Won, 1997).
Occurrence: Described specimens from

Olenekian (Early Triassic) in northeastern Vietnam285

Fig. 202. Plenoentactinia? terespongia Takahashi, sp. nov. 1, TGU 8701, from KC02-10. 2, TGU 8719, holotype, from KC02-10. 3, TGU 8621, from KC02-10. 4, TGU 8620, from KC02-10. 5, TGU 8904, from NT0107. Scale bars = 100 μm (1–3), 50 μm (4, 5).

286

Shigeta, Komatsu, Maekawa and Dang (eds.)

NT01-05, NT01-07 and KC02-10 within theNovispathodus pingdingshanensis Zone represented by the Xenoceltites variocostatus beds
(Upper Smithian = upper Lower Olenekian) in
the Bac Thuy Formation, northeastern Vietnam.
Genus Spongentactinia Nazarov, 1975
Type species: Spongentactinia fungosa
Nazarov, 1975.
Spongentactinia? sp. indet.
Fig. 203.1–203.4

Material examined: One specimen, TGU
9111, from NT01-05, and three specimens,
TGU 8609, 8616, 8623, from KC02-10.
Remarks: We recovered only very poorly
preserved and fragmental specimens of thisspecies. The specimens have thin, fragile,
spherical spongy shell with four or five, possibly six long, slender needle-like spines.
Spongy shell has rather loose meshes, verythin and irregular bars and seems to be disposed in concentric layer and traversed by aseries of thin radial bars. Spicule center is not
visible due to the poor preservation.
Occurrence: Described specimens fromNT01-05 and KC02-10 within the Novispathodus pingdingshanensis Zone represented by
the Xenoceltites variocostatus beds (Upper
Smithian = upper Lower Olenekian) in the Bac
Thuy Formation, northeastern Vietnam.
Family Palaeoscenidiidae Riedel, 1967,
emend Furutani, 1983
(syn: Parentactiniidae Kozur and Mostler, 1981;
Protoentactiniidae Kozur, Mostler and
Repetski, 1996)
Genus Parentactinia Dumitrica, 1978
Type species: Parentactinia pugnax Dumitrica, 1978.

Parentactinia nakatsugawaensis Sashida,
1983
Fig. 204.1–204.3
Parentactinia nakatsugawaensis Sashida, 1983, p. 172, pl.
37, figs. 1–9; Sashida, 1991, p. 687, figs. 5.15, 5.16,
6.1, 6.3–6.6; Sugiyama, 1992, p. 1212, 1213, figs.
14.7–14.10; Sugiyama, 1997, p. 184, figs. 27.2, 27.3;
Sashida et al., 2000a, p. 801, fig. 8.24; Sashida et al.,2000b, p. 86, figs. 7.1–7.7.

Material examined: Two specimens, TGU
9115, 9211, from NT01-05, and two specimens, TGU 8902, 8905, from NT01-07.
Remarks:
Parentactinia
nakatsugawaensis, especially when poorly preserved, resembles the spiculate nassellarian species Tandarnia recoarensis Dumitrica, 1982, as suggested by Sashida (1983). However, both are
distinguishable by the presence of a latticed
shell and/or branching pattern of the spines. P.
nakatsugawaensis has a loose hemispheric latticed shell, among the four basal spines; thebasal spines are rather straight and are longer
than those of T. recoarensis. Furthermore, P.
nakatsugawaensis has no apical verticil.
Occurrence: Described specimens fromNT01-05 and NT01-07 within the Novispathodus pingdingshanensis Zone represented by
the Xenoceltites variocostatus beds (Upper
Smithian = upper Lower Olenekian) in the Bac
Thuy Formation, northeastern Vietnam. This
species also occurs in the Lower Triassic(Spathian?) chert beds of central Japan (Sashida, 1983, 1991; Sugiyama, 1992, 1997) andthe Spathian chert beds of the southern andnorthern Thailand (Sashida et al., 2000a, b).
Parentactinia cf. pugnax Dumitrica, 1978
Fig. 203.5
cf. Parentactinia pugnax Dumitrica, 1978, p. 50, pl. 4,
figs. 4?, 5, pl. 5, figs. 1–3; Kozur and Mostler, 1994,
p. 45, pl. 1, figs. 11, 12.

Material examined: One specimen, TGU
9215, from NT01-05.
Remarks: From this species we found only
the fragment illustrated. It has a globular shellOlenekian (Early Triassic) in northeastern Vietnam

287

Fig. 203. 1–4, Spongentactinia? sp. indet. 1, TGU 8623, from KC02-10. 2, TGU 8616, from KC02-10. 3, TGU
8609, from KC02-10. 4, TGU 9111, from NT01-05. 5, Parentactinia cf. pugnax Dumitrica, 1978, TGU 9215,
from NT01-05. Scale bars = 100 μm.

288

Shigeta, Komatsu, Maekawa and Dang (eds.)

and an eccentric and robust initial spicule withan extremely short median bar, four basal
spines and probably three apical spines ofwhich only two are preserved. Basal spines are
longer than the apical ones, relatively straight
and arranged under different angles relative tothe axis of shell. They are prolonged outside
the shell as relatively long spines. Test is also
robust with pores of irregular shape, size andarrangement. Our specimen resembles verymuch the late Illyrian or early Fassanian specimen questionably assigned to Parentactinia
pugnax Dumitrica, 1978. This specimen has
also three apical spines and a globular shellthat includes in it also the medial bar.
Occurrence: Described specimens fromNT01-05 within the Novispathodus pingdingshanensis Zone represented by the Xenoceltites variocostatus beds (Upper Smithian = upper Lower Olenekian) in the Bac Thuy
Formation, northeastern Vietnam. Parentactinia pugnax occurs fairly rare in the upper Illyrian (= uppermost Anisian) or lower Fassanian(lowest Ladinian) at Recoaro, northern Italy(Dumitrica, 1978) and Balaton Highland,
western Hungary (Kozur and Mostler, 1994).
Family Pentactinocarpidae Dumitrica, 1978
Genus Pentactinocarpus Dumitrica, 1978
Type species: Pentactinocarpus fusiformis
Dumitrica, 1978.
Pentactinocarpus? aff. acanthicus
Dumitrica, 1978
Fig. 204.4–204.7
aff. Pentactinocarpus acanthicus Dumitrica, 1978, p. 44,
pl. 3, fig. 3; Kozur and Mostler, 1994, p. 46, pl. 2,
figs. 3, 5.

Material examined: Four specimens, TGU
8614, 8618, 8625, 8806, from KC02-10, andfour specimens, TGU 9008, 9112, 9120, 9214,
from NT01-05.
Remarks: Our specimens have a large subspherical shell with long conical apical andantapical spines. Five or more basal spines ex-

tend laterally downward or slightly upward.
Pores are elliptical or sub-circular and irregularly arranged. Although our specimens arepoorly preserved, the characteristic featuresare similar to those of Pentactinocarpus acanthicus described from the uppermost Anisianto lowest Ladinian of Recoaro, Italy by Dumitrica (1978). However, our specimens differ
from the type species in having more than fourbasal spines in some specimens, no primaryring around the spicule center and no intercalary spines between the four basal spines.
Until present this genus was not yet recorded
at stratigraphic levels older than late Anisian.
Occurrence: Described specimens fromNT01-05 and KC02-10 within the Novispathodus pingdingshanensis Zone represented by
the Xenoceltites variocostatus beds (Upper
Smithian = upper Lower Olenekian) in the Bac
Thuy Formation, northeastern Vietnam.
Family Thalassothamnidae Haecker, 1906
Genus Triassothamnus Kozur and Mostler, 1981
(syn: Archaeothamnulus Dumitrica, 1982)
Type species: Palacantholithus? verticillatus Dumitrica, 1978.
Triassothamnus verticillatus (Dumitrica, 1978)
Fig. 205
Palacantholithus? verticillatus Dumitrica, 1978, p. 42, pl.
1, fig. 1, pl. 2, fig. 5.
Archaeothamnulus verticillatus (Dumitrica, 1978). Dumitrica, 1982, p. 418, pl. 5, figs. 3, 4, pl. 7, fig. 4.

Material examined: Three specimens,
TGU 8615, 8802, 8803, from KC02-10, one
specimen, TGU 9011, from NT01-05, and one
specimen, TGU 8906, from NT01-07.
Remarks: Our specimens have a long,straight, needle-like axial spine and fourslightly curved basal spines arising from the
spicule center. The apical spine has sometimes
an apical verticil of three short and thin spinules, whereas the basal spines have generally
a verticil of three or four spinules. The lengthsof spinules vary from very short to moderately

Olenekian (Early Triassic) in northeastern Vietnam

289

Fig. 204. 1–3, Parentactinia nakatsugawaensis Sashida, 1983. 1, TGU 8902, from NT01-07. 2, TGU 9115, fromNT01-05. 3, TGU 9211, from NT01-05. 4–7, Pentactinocarpus? aff. acanthicus Dumitrica, 1978. 4, TGU
8618, from KC02-10. 5, TGU 9112, from NT01-05. 6, TGU 8614, from KC02-10. 7, TGU 8806, from KC0210. Scale bars = 50 μm (1–3), 100 μm (4–7).

290

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 205. Triassothamnus verticillatus (Dumitrica, 1978). 1, TGU 8802, from KC02-10. 2, TGU 8803, from
KC02-10. 3, TGU 8615, from KC02-10. 4, TGU 8906, from NT01-07. 5, TGU 9011, from NT01-05. Scalebars = 100 μm.

Olenekian (Early Triassic) in northeastern Vietnam

long. As already suggested by Dumitrica(1982), we recognized also two morphotypes
within the species, one without an apical verticil (Fig. 205.5) and the other with an apicalverticil consisting of three spinules (Fig.
205.1–205.4).
Occurrence: Described specimens fromNT01-05, NT01-07 and KC02-10 within theNovispathodus pingdingshanensis Zone represented by the Xenoceltites variocostatus beds
(Upper Smithian = upper Lower Olenekian) in
the Bac Thuy Formation, northeastern Vietnam. This species rarely occurs in the lower
Fassanian (lowest Ladinian) at Recoaro, northern Italy (Dumitrica 1978, 1982).
Family Entactiniidae Riedel, 1967
Genus Entactinosphaera Foreman, 1963
Type species: Entactinosphaera esostrongyla Foreman, 1963.
Entactinosphaera sp. indet.

291

Order Nassellaria Ehrenberg, 1875
Family Archaeosemantidae Kozur andMostler, 1981, emend De Wever et al., 2001
Genus Tandarnia Dumitrica, 1982, emend
Dumitrica, 2004
Type species: Tandarnia recoarense Dumitrica, 1982.
Remarks: The genus Tandarnia is a Triassic spiculate genus with spicules very similarin arrangement to those of the entactinarian
Parentactinia Dumitrica, 1978, but bearing no
latticed shell as in Parentactinia. They are
therefore easily distinguished by their generalshape and, if possible, preserved ornamentation. Furthermore, the genus Tandarnia has
typical disposition of spines as nassellarians;
i.e., it has two homologous spines of apicaland ventral, that are commonly longer than theother four lateral basal spines, and the arrangement is verticil, which is a system of branches
disposed around the same point from the spicule center.

Fig. 206.1–206.2

Material examined: Two specimens, TGU
9103, 9110, from NT01-05.
Remarks: The test consists of two thin
spherical shells interconnected through seemly
six, three-bladed radial beams prolonged outside cortical shell into long and gently tapering three-bladed radial spines. Radial beams
and spines not disposed in the three isometricaxes. The wall of both shells perforated bysmall, polygonally-framed pores. Due to thepoor preservation we could not see if inside
the inner shell there is another shell or a spicule.
Occurrence: Described specimens fromNT01-05 within the Novispathodus pingdingshanensis Zone represented by the Xenoceltites variocostatus beds (Upper Smithian = upper Lower Olenekian) in the Bac Thuy
Formation, northeastern Vietnam.

Tandarnia recoarensis Dumitrica, 1982
Fig. 206.3–206.5
Tandarnia recoarense Dumitrica, 1982, p. 415, pl. 3, figs.
6–10; Goričan and Buser, 1990, p. 159, pl. 7, fig. 4.
Tandarnia recoaroense Dumitrica, 1982. Kozur et al.,1996b, p. 219, pl. 11, figs. 1, 2, 4–7.
Tandarnia recoarensis Dumitrica, 1982. Sugiyama, 1997,
p. 187, fig. 48.10; Dumitrica, 2004, p. 221, pl. 5, fig.
3, pl. 10, figs. 4–6.

Material examined: Three specimens,
TGU 8613, 8709, 8713, from KC02-10.
Remarks: Tandarnia recoarensis resembles the entactinarian species of Parentactinia
nakatsugawaensis Sashida, 1983. However, T.
recoarensis differs from P. nakatsugawaensis
in having two homologous apical and verticalspines, and four lateral upward-curved basal
spines, and the arrangement of the all spines isverticil with three or four simple spinules. In
addition, T. recoarensis has many shortbranching intricately crossed spinules.
Occurrence: Described specimens from

292

Shigeta, Komatsu, Maekawa and Dang (eds.)

Fig. 206. 1–2, Entactinosphaera sp. indet. 1, TGU 9103, from NT01-05. 2, TGU 9110, from NT01-05. 3–5,
Tandarnia recoarensis Dumitrica, 1982. 3, TGU 8709, from KC02-10. 4, TGU 8613, from KC02-10. 5, TGU
8713, from KC02-10. Scale bars = 100 μm.

Olenekian (Early Triassic) in northeastern Vietnam

293

Fig. 207. Paroertlispongus spinorientalis Takahashi, sp. nov. 1, TGU 8809, holotype, from KC02-10. 2, TGU
8631, from KC02-10. 3, TGU 8914, from NT01-07. 4, TGU 8811, from KC02-10. 5–6, TGU 8708, from
KC02-10. Scale bars = 100 μm (1–3, 5), 50 μm (4, 6).

294

Shigeta, Komatsu, Maekawa and Dang (eds.)

KC02-10 within the Novispathodus pingdingshanensis Zone represented by the Xenoceltites variocostatus beds (Upper Smithian = upper Lower Olenekian) in the Bac Thuy
Formation, northeastern Vietnam. This species
occurs in the upper Illyrian (= uppermost Anisian) to lower Fassanian (lowest Ladinian) at
Recoaro, northern Italy (Dumitrica, 1982,
2004), the Slovenian Carbonate Platform, Slovenia (Goričan and Buser, 1990), and the
Loibl Formation, Austria (Kozur et al.,1996b). It also occurs in lower Anisian chert
beds of central Japan (Sugiyama, 1997).
Order Spumellaria Ehrenberg, 1875, emend
De Wever et al., 2001
Family Oertlispongidae Kozur and Mostler, 1980
emend Kozur and Mostler, 1981
Genus Paroertlispongus Kozur and Mostler, 1981
Type species: Paroertlispongus multispinosus Kozur and Mostler, 1981.
Remarks: We use this genus in the wider
sense used already by Feng et al. (2006) who
included in it species with many spines.
Paroertlispongus spinorientalis
Takahashi, sp. nov.
Fig. 207

Material examined: Holotype, TGU 8809
(Fig. 207.1), from KC02-10. Five specimens,
TGU 8502, 8631, 8708, 8811, 8815, from
KC02-10, three specimens, TGU 9009, 9012,
9119, from NT01-05, and one specimen, TGU
8914, from NT01-07.
Diagnosis: Five to seven concentric spherical shells, consisting of an irregular, loose
spongy framework with numerous thorns andnine long, slender, cylindrical spines. A threedimensionally patterned framework of spongy
tissues developed on each shell except in the
innermost one.
Etymology: The Latin adjectives spinosus(thorny) and Orientalis (Oriental) indicate its
morphology and the occurrence in the eastern
Asia.

Description: Test composed of five toseven shells and nine long, slender radial
spines. Spines straight and cylindrical withuniform length and shape. Innermost shell
composed of a lattice with loose polygonal
meshes. All other shells have a meshwork similar to that of the innermost shell; however, athree-dimensionally patterned framework ofspongy tissues is developed on each shell except in the innermost shell. Surface of the outermost shell has an irregular, loose spongy
framework and numerous thorns or cylindricalshort by-spines.
Measurements (7 specimens): Diameter ofshell 149–171 μm (mean = 158.6 μm); length ofspines 148–154 μm (mean = 151.1 μm).
Remarks: The inner shell structure of thespecies was not possible to see because of thelooseness and complexity of the shell meshwork. The general outline of the test of our
specimens resembles those of the genus Paroertlispongus. This species resembles somemulti-spiny species illustrated by Feng et al.
(2006) from the latest Permian of South China.
Occurrence: Described specimens from
NT0-05, NT01-07 and KC02-10 within theNovispathodus pingdingshanensis Zone represented by the Xenoceltites variocostatus beds
(Upper Smithian = upper Lower Olenekian) in
the Bac Thuy Formation, northeastern Vietnam.
Concluding Remarks(by Y. Shigeta, T. Komatsu, T. Maekawa
and H. T. Dang)
Our Japanese-Vietnamese Joint field investigation has described in detail the stratigraphy and faunal succession of the Lower Triassic in northeastern Vietnam. These studies
have not only resulted in the reconstruction ofdepositional environments and the establishment of a biostratigraphic framework, but theyalso have contributed significantly to a better
understanding of the global environmental
change and dynamics of the biotic recovery

Olenekian (Early Triassic) in northeastern Vietnam

following the Permian-Triassic mass extinction. However, a considerable amount of work
remains to be accomplished. Planned studies
include stable isotope stratigraphy, magnetostratigraphy, biomarker analysis, spore analysis and the study of fish and shark teeth.
Therefore, the future efforts of the joint research team will result in even greater contributions and will significantly broaden our
knowledge of the Early Triassic.

Acknowledgements
We are very grateful to all personnel of theVietnam Institute of Geosciences and Mineral
Resources (Hanoi) for their kind help and cooperation throughout the field survey. Y.
Shigeta is indebted to the following institutions for kindly providing him the opportunity
to examine type and comparative specimens of
Early Triassic ammonoids: Institute and Museum of Paleontology, University of Zurich (Zurich), Department of Palaeontology, University of Vienna (Vienna), Geological Survey ofAustria (Vienna), Museum of Natural Historyof Vienna (Vienna), Goldfuss Museum (Steinmann Institute), Bonn University (Bonn),
Geological Survey of India (Kolkata), Geologic Museum, Bao Tang Dia Chat (Hanoi), Nanjing Institute of Geology and Palaeontology(Nanjing), Central Research Geological Prospecting Museum (St. Petersburg), Paleontological Institute (Moscow), Far Eastern Geological Institute (Vladivostok), and Geological
Survey of Canada (Ottawa). Thanks are extended to J. F. Jenks (Utah) for his helpful suggestions and improvement of the English text.
This study was financially supported by
grants-in-aid from the Japanese Ministry of
Education, Culture, Sports, Science, and Technology (no. 20740300), Japan Society for Promotion of Science (no. 25400500) and JSPSVAST Joint Research Program to T. Komatsu,
grants of the National Museum of Nature andScience in 2010–2012 to Y. Shigeta, a grant-in

295

aid from the Japan Society for Promotion of
Science (no. 24540501) to G. Tanaka, and theFulbright Commission to A. Kaim.
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Early Cretaceous marine and brackish-water Gastropoda from Japan. By Tomoki Kase, 199 pp., 31 pls.,
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A taxonomic study on the subfamily Herminiinae of Japan (Lepidoptera, Noctuidae). By Mamoru
Owada, 208 pp., 1987.
Small mammal fossils and correlation of continental deposits, Safford and Duncan Basins, Arizona,
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Late Miocene floras in northeast Honshu, Japan. By Kazuhiko Uemura, 174 pp., 11 pls., 1988.
A revisional study of the spider family Thomisidae (Arachnida, Araneae) of Japan. By Hirotsugu Ono,
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The taxonomic study of Japanese dictyostelid cellular slime molds. By Hiromitsu Hagiwara, 131 pp.,
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Rodent and lagomorph families of Asian origins and diversification: Proceedings of Workshop WC-2
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Annoted checklist of the inshore fishes of the Ogasawara Islands. By John E. Randall, Hitoshi Ida,
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Polychaetous annelids from Sagami Bay and Sagami Sea collected by the Emperor Showa of Japan anddeposited at the Showa Memorial Institute, National Science Museum, Tokyo. Families Polynoidae andAcoetidae. By Minoru Imajima, 131 pp., 1997.
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Onuphidae (Annelida, Polychaeta) from Japan, excluding the genus Onuphis. By Minoru Imajima, 115
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Description of a new species of Anhangueridae (Pterodactyloidea) with comments on the pterosaur
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Revision of scydmaenid beetles of the genus Syndicus Motschulsky (Coleoptera, Scydmaenidae). By
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Leaf-rolling Sawflies of the Pamphilius vafer complex (Hymenoptera, Pamphiliidae). By Akihiko Shinohara, 116 pp., 2005.
Types of Japanese Bird. By Hiroyuki Morioka, Edward C. Dickinson, Takashi Hiraoka, Desmond Allen
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Checklist of Japanese lichens and allied fungi. By Syo Kurokawa and Hiroyuki Kashiwadani, 157 pp.,
2006.
Proceedings of the Seventh and Eighth Symposia on Collection Building and Natural History Studies in
Asia and the Pacific Rim. Edited by Yukimitsu Tomida, Tsunemi Kubodera, Shinobu Akiyama andTaiju Kitayama, 294 pp., 2006.
Anatomy of a Japanese Tomistomine Crocodylian, Toyotamaphimeia Machikanensis (Kamei et Ma­
tsumoto, 1965), from the Middle Pleistocene of Osaka Prefecture: The Reassessment of its Phylogenetic Status within Crocodylia. By Yoshitsugu Kobayashi, Yukimitsu Tomida, Tadao Kamei and Taro
Eguchi, 121 pp., 2006.
A systematic study of the genus Siriella (Crustacea: Mysida) from the Pacific and Indian oceans, withdescriptions of fifteen new species. Edited by Masaaki Murano and Kouki Fukuoka, 173 pp., 2008.
Chromosome atlas of flowering plants in Japan. Edited by Tsunehiko Nishikawa, 706 pp., 2008.
The Lower Triassic System in the Abrek Bay area, South Primorye, Russia. Edited by Yasunari Shigeta,
Yuri D. Zakharov, Haruyoshi Maeda and Alexander M. Popov, 218 pp., 2009.
Deep-sea Fauna and Pollutants off Pacific Coast of Northern Japan. Edited by Toshihiko Fujita, 755 pp.,
2009.
Joint Haeckel and Ehrenberg Project: Reexamination of the Haeckel and Ehrenberg Mircofossil Collections as a Historical and Scientific Legacy. Edited by Yoshihiro Tanimura and Yoshiaki Aita, 106 pp.,2009.
Middle and Late Miocene Marie Bivalvua from the Northeern Kanto Region, Central Japan. Edited by
Yukito Kurihara, 87 pp., 2010.
Chemical Compositions of Electrum Grains in Ore and Placer Deposits in the Japanese Islands. By Kazumi
Yokoyama, Shogo Takeuchi, Izumi Nakai, Yukiyasu Tsutsumi, Takashi Sano, Masako Shigeoka, Ritsuro
Miyawaki and Satoshi Matsubara, 80 pp., 2011.
Digeneans (Trematoda) Parasitic in Freshwater Fishes (Osteichthyes) of the Lake Biwa Basin in Shiga
Prefecture, Centeral Honshu, Japan. By Takeshi Shimazu, Misako Urabe and Mark J. Grygier, 105 pp.,2011.
Deep-sea Fauna of the sea of Japan. Edited by Toshihiko Fujita, 291 pp., 2014.

All inquiries concerning the Monographs should be addressed to:
Library
National Museum of Nature and Science
4-1-1 Amakubo, Tsukuba, Ibaraki 305-0005 Japan(* out of print)