Bull. Tohoku Univ. Museum, No. 16, pp.1‒ 4, 2017
© by The Tohoku University Museum

Early Devonian orthocerid cephalopods from theKamianama Formation, Fukui Prefecture, Central JapanShuji Niko
Department of Environmental Studies, Faculty of Integrated Arts and Sciences, Hiroshima University, Higashihiroshima, 7398521, Japan
Abstract: Four species of orthocerid cephalopods, including Fukujiceras kamiyai, Spyroceras
fukujiense, Mitorthoceras? sp. and Buchanoceras sp., are described from the Kuzuryu Lake-Ise
River area, Fukui Prefecture, Central Japan. They occur from the Lochkovian (early Early Devonian)
shale of the Oisedani Member, the Kamianama Formation. This assemblage indicates strong affinity
to that of the Takaharagawa Member in the Fukuji Formation, Gifu Prefecture. The Fukujiceras
Fauna is newly defined for the Kamianama and Fukuji cephalopod assemblages

Introduction
The Kamianama Formation (Fujimoto, 1953; Kurihara,2003; Niko and Senzai, 2010) of the Kuzuryu Lake-Ise
River area, Fukui Prefecture, Central Japan contains thediverse Devonian marine faunas. Here the author discusses
orthocerid cephalopods heretofore undescribed in thefaunas except for those reported preliminary by Hamadaand Itoiwaga (1983), Tokai Kaseki Kenkyukai (1995) andKamiya and Niko (1997). The material was collected from anoutcrop (= locality KU-1 in Niko and Senzai, 2006) of black
calcareous shale along the Kamaharadani Valley. Niko andSenzai (2010) divided the Kamianama Formation into theLochkovian (early Early Devonian) to Emsian (late EarlyDevonian) Oisedani Member and the Emsian to probablyEifelian (early Middle Devonian) Hakubado Member.
Stratigraphic position of the cephalopod bearing shale lies inthe Lochkovian part of the Oisedani Member.
Abbreviations used for repositories are as follows. IGPS:
Institute of Geology and Paleontology, Faculty of Science,
Tohoku University, Sendai, HMNH: Hida Museum of NaturalHistory, Fukuji, Takayama, and UMUT: the University
Museum, University of Tokyo, Tokyo.

Faunal discussion
The present cephalopod assemblage contains Fukujiceras
kamiyai Niko, 1996, Spyroceras fukujiense Niko, 1996,
Mitorthoceras? sp., and Buchanoceras sp. With theexception of Mitorthoceras? sp., they are common with thoseof the assemblage documented by Niko (1990, 1991, 1993,1996, 1998a, b, 2006) and Niko and Nishida (2003a, b) fromthe Takaharagawa Member of the Fukuji Formation in Gifu

Prefecture. In the generic level, Fukujiceras is an endemic
genus in the Hida Gaien Belt including the Kamianama andFukuji formations. On the basis of their strong faunal affinity
and geologic settings, the Fukujiceras Fauna is newly
defined for these assemblages. This fauna may developedin a non-tropic water condition around northeastern marginof North China (Niko, 1998a).

Systematic paleontology
Order Orthocerida Kuhn, 1940
Superfamily Pseudorthoceratoidea Flower and Caster,1935Family Pseudorthoceratidae Flower and Caster, 1935
Subfamily Pseudorthoceratinae Flower and Caster, 1935
Genus Fukujiceras Niko, 1996
Type species.—Fukujiceras kamiyai Niko, 1996;
Lochkovian (lower Lower Devonian) in Gifu Prefecture,
Central Japan.
Fukujiceras kamiyai Niko, 1996
Figures 1.1‒1.3, 1.8, 1.9
Conularia sp. (cf. C. mitchelli Fletcher, 1938). Murata, 1977,
p. 38, 39, figs. 2‒4.
Conularia sp., Tanaka, Ono and Murata, 1977, figs. 3A‒3C.
Fukujiceras kamiyai Niko, 1996, p. 348, 350, figs. 2.1‒2.13;
Niko, 2006, fig. 2.8.2-6.
Fukujiceras cf. kamiyai; Kamiya and Niko, 1997, p. 83, 85,figs. 1.1‒1.3.
Description.—Three deformed specimens of incomplete
phragmocones are available for study; they are orthoconic
longicones with moderate conch expansion; the largest

2Shuji Niko

specimen attains 164 mm in length; surface ornamentationconsists of flat topped transverse lirae that frequently formshallow to linguiform salients; adjoining lirae separated bynarrow striae. Sutures directly transverse.
Material examined.—IGPS coll. No. 111736, 111737. Aspecimen, T. Kamiya’s personal collection, is also examined.
Type species.—Holotype, UMUT PM 19111. Paratypes,UMUT PM 19112‒19119, 19143.
Discussion.—Fukujiceras kamiyai is easily recognizedby its characteristic surface ornamentation. This species iswell described and illustrated by Niko (1996) on the basis of
the types from the Lochkovian shale of the Takaharagawa
Member, Fukuji Formation.
Murata (1977) and Tanaka et al. (1977) described a single
fragmentary shell of Conularia from the Kamianama Formation.
Although this specimen is inadequate for identification, itexhibits identical lirae and salient with those of Fukujiceras
kamiyai. There is a high possibility that “the first Devonian
conulariid in Japan” in their papers is misidentification.
Dimple-like borings caused by bioerosion are recognized on theshell surface of this species and Mitorthoceras? sp. (this report).

like surface ornamentation in juvenile shell.

Subfamily Spyroceratinae Shimizu and Obata, 1935
Genus Spyroceras Hyatt, 1884
Type species.—Orthoceras crotalum Hall, 1861; Middle
Devonian of New York, North America.

Subfamily Cayutoceratinae Flower, 1939
Genus Buchanoceras Teichert and Glenister, 1952
Type species.—Buchanoceras graviventrum Teichert andGlenister, 1952; Lower Devonian in Victoria, Australia.

Spyroceras fukujiense Niko, 1996
Figures 1.4, 1.5

Buchanoceras sp.
Figures 1.6, 1.10

Metaspyroceras insignis Niko, 1991. Field Selection 20,Fossils (Tokai Kaseki Kenkyukai), 1995, p. 49.
Spyroceras fukujiense Niko, 1996, p. 350, 352, figs. 3.3‒3.11,
4.1‒4.5; Niko, 2006, fig. 2.8.2-3.

[?] Michelinoceras hidense Kobayashi, 1958. Hamada andDescription.—A weakly deformed specimen of incomplete
phragmocone is available for study; it is annulated longicone
with gradual conch expansion and 51 mm in length; annulationstransverse, low; surface ornamentation consists of longitudinalribs and coarse lirae. Sutures straight, slightly oblique.
Material examined.—IGPS coll. No. 111738.
Type species.—Holotype, UMUT PM 18505. Paratypes,UMUT PM 18506, 19507, 18512‒18515, 18516, 18517,19145‒19151, HMNH-N098.
Discussion.—Previous records of Spyroceras fukujiense
have been restricted in the Lochkovian shale of theTakaharagawa Member, Fukuji Formation. Metaspyroceras
insignis is easily distinguished from this species by its lattice-Genus Mitorthoceras Gordon, 1960
Type species.—Mitorthoceras perfilosum Gordon,
1960; Chesterian (Upper Mississippian; upper Lower
Carboniferous) in Arkansas, North America.
Mitorthoceras? sp.
Figure 1.7
Description.—A strongly deformed specimen is availablefor study; it is longiconic orthocone with very gradual conch
expansion, and 29 mm in length; surface ornamentationconsists of fine transverse lirae.
Material examined.—IGPS coll. No. 111739.
Discussion.—Because this poorly preserved specimen
indicates synapomorphies found with the generic type,
Mitorthoceras perfilosum Gordon (1960, p. 136, 137, pl. 27,figs. 1‒4, 8; Niko and Mapes, 2015, p. 54, 56, figs. 2.1‒2.11),
including general conch shape and ornamentation, it isquestionably placed in Mitorthoceras.

Itoigawa, 1983, p. 15.
Buchanoceras sp., Niko, 1996, p. 358, 359, figs. 8.1‒8.4.

Description.—A weakly deformed specimen of incomplete
phragmocone is available for study; it is longiconic orthocone
measuring 48 mm in length; conch expansion very gradual;
conch surface lacks distinct ornamentation. Sutures directlytransverse; camerae relatively short; siphuncle consists ofcyrtochoanitic septal necks and expanded connecting rings.
Cameral deposits occur at episeptal-mural and hyposeptal
positions; annulosiphonate endosiphuncular deposits arewell developed, but not fusing.
Material examined.—IGPS coll. No. 111740.
Discussion.—The specimen is conspecific with those fromthe Lochkovian shale of the Takaharagawa Member, Fukuji
Formation and probably represent a new species. However, theirpreservations are not adequate for detailed systematic treatment.

→Figure 1. 1‒3, 8, 9. Fukujiceras kamiyai Niko, 1996: 1, 2, IGPS coll. No. 111736, side view and partial enlargements
to show details of surface ornamentation, note borings caused by bioerosion; 3, side view of Kamiya’s specimen, noteborings on the shell surface; 8, 9, IGPS coll. No. 111737, partial enlargements to show details of surface ornamentation. 4,5. Spyroceras fukujiense Niko, 1996, IGPS coll. No. 111738, side view and partial enlargements to show details of surface
ornamentation. 6, 10. Buchanoceras sp., IGPS coll. No. 111740, ventral view and dorsoventral thin section, arrow indicates
septal neck. 7. Mitorthoceras? sp., IGPS coll. No. 111739, side view, note borings on the shell surface. Scale bar is 15 mm inFigures 1.1, 1.4, 1. 6; 3 mm in Figures 1.2, 1.5, 1.8‒1.10; 30 mm in Figure 1.3; 10 mm in Figure 1.7.

Devonian cephalopods from Fukui

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Shuji Niko

Acknowledgements
I am indebted for the loan of a relatively well-preserved
specimen of Fukujiceras kamiyai to Mr. Toshiaki Kamiya.
Messrs. Akiyasu Watanabe, Yoshihito Senzai and Teruo Onokindly assisted in field works in the Kuzuryu Lake-Ise River
area. Thanks also go to an anonymous reviewer for helpfulcomments on an early version of the manuscript.

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