ISSN 0031 - 0204

Transactions and Proceedingsof thePalaeontological Society of Japan
New SeriesNo. 146

Palaeontological Society of J apan
July 30.1987

Co-Editors

Hisayoshi IGO and Tsunemasa SAITO

Officers for 1987-1988
President: Tatsuaki KIMURA
Honorary President: Teiichi KOBAYASHI
Councillors: Kiyotaka CHINZEI, Takashi HAMADA, Yoshikazu HASEGAWA, Itam HAYAMI,
Hisayoshi IGO, Junji ITOIGAWA, Tadao KAMEl, Tatsuaki KIMURA, Tamio KOTAKA,Kei MORI, Ikuwo OBATA, Tsunemasa SAITO, Yokichi TAKAYANAGI, Kazushige
TANABE, Toshimasa TANAIMembers of Standing Committee: Kiyotaka CHINZEI (Membership), Takashi HAMADA (Foreign Affairs), Itaru HAYAMI (Finance), Hisayoshi IGO (Co-Editor of Transactions),
Ikuwo OBATA (General Affairs), Sumio SAKAGAMI (Co-Editor of Special Paper),Kazushige TANABE (Planning), Yokichi TAKAYANAGI (Editor of "Fossils"), Juichi
YANAGIDA (Co-Editor of Special Paper)
Secretaries: Katsumi ABE (Planning), Takeshi ISHIBASHI (Special Paper), Kunihiro ISHIZAKI("Fossils"), Tomoki KASE (General Affairs and Membership), Hiroshi NODA (Editorof Transactions), Terufumi OHNO (Membership), Tatsuo On (Planning), Kazuhiko
UEMURA (General Affairs), Toshiyuki YAMAGUCHI (Finance)
Auditor: Noriyuki IKEYAThe fossil on the cover is Vicarya yokoyamai Takeyama, an Early Middle
Miocene gastropod from the Kurosedani Formation at Kakehata, Yatsuo-cho,
Nei-gun, Toyama Prefecture, central Japan (Collected by T. Kotaka and K.
Ogasawara, IGPS No. 99075, photo by S. Ohtomo and Y. Kikuchi, xO.9).

All communication relating to this journal should be addressed to the

PALAEONTOLOGICAL SOCIETY OF JAPAN% Business Center for Academic Societies,
Yayoi 2-4-16, Bunkyo-ku, Tokyo 113, Japan

Trans. Proc. Palaeont. Soc. Japan, N, S., No. 146, pp. 35-41,3 Figs., July 30, 1987

828. EARLY PERMIAN CEPHALOPODS FROM
THE MIZUYAGADANI FORMATION, FUKUJI DISTRICT, CENTRAL JAPAN*
SHun NIKO
Department of Earth Science and Astronomy, College of Arts and Sciences,
The University of Tokyo, Komaba, Tokyo 153

andTAMIO NISHIDA
Department of Earth Sciences, Faculty of Education, Saga University, Saga 840

Abstract. Two cephalopod species (Bitaunioceras undulatum Niko and Nishida, sp. nov.
and pseudorthoceratid, gen. et sp. indet.) are described from the Permian Mizuyagadani Formation, Fukuji district, Gifu Prefecture, central Japan. The morphology of the septal necks andorganic deposits of Bitaunioceras undulatum suggest that this genus should be referred to the
Pseudorthoceratidae. Associated microfauna with these cephalopods is dominated by sessile
forms of smaller foraminifers which indicate an Early Permian (Sakmarian) time.

yses of thin sections, which were prepared fromwell-preserved specimens of Bitaunioceras undulatum, have been performed to obtain detailsof the internal structures such as connecting
rings, septal necks and organic deposits. Basedon these morphological features a taxonomic
position of Bitaunioceras is discussed in thisreport.
The illustrated specimens are placed in the repository of the University Museum, the University of Tokyo (UMUT).
The authors wish to thank Dr. T. Hamada of
the University of Tokyo for his valuable suggestions and critical reading of the manuscript.
Thanks are also due to Dr. T. Kobayashi of theJapan Academy for his kindness in reading of themanuscript. We would like to thank Dr. Y. Okimura of Hiroshima University for valuable suggestions and identifications of smaller foraminifers and also Dr. M. Suzuki of Hiroshima University for his kind guidance in the petrographicalstudy.

Introduction

Two species of orthoconic nautiloids, i.e.
Bitaunioceras undulatum Niko and Nishida, sp.
nov. and pseudorthoceratid, gen. et sp. indet. arereported here from the Lower Permian Mizuyagad ani Formation. These cephalopods occur inthe lower reaches of the Mizuyagadani Valley,
which is located some 2 km southwest of Fukuji,
Kamitakara Village, Yoshiki County, Gifu Prefecture (Figure 1). A preliminary report on this occurrence has been published in Japanese (Okimura, Niko and Nishida, 1984).
The genus Bitaunioceras is widely distributedin Permian rocks of Timor (Haniel, 1915), Sicily(Gemmellaro, 1890), Southern Urals (Shim ansky, 1954), Texas (Miller and Youngquist, 1947,
1949), Coahuila, Mexico (Miller and Unklesbay,
1942; King, 1944; Miller, 1944; Miller andYoungquist, 1949) and Japan (this report). Anal*Received September 16, 1986; revised manuscript received June 16, 1987; read October 23,1983 at Kumamoto University; JT AF Contrib. No. XLIV.

35

Shuji NIKO and Tamio NISHIDA

36

Stratigraphy and associated fauna
The Lower Permian Mizuyagadani Formation(Kamei, 1952; Igo, 1956, 1957; Niikawa, 1978,1980) comprises about a 250 m thick sequence
consisting mainly of clastic rocks, which is distributed in some fault blocks" in the Mizuyagadani Valley, Osobudani Valley and along the upper course of the Ichinotani Valley. Most of thesequence consists of gray sandstone and black togreenish gray mudstone interbedded with subordinate amounts of conglomerate and "lenticular" limestone. It rests conformably upon carbonates of the Ichinotani Formation of Carboniferous-Permian age.
The present orthoceratids were collected froma reddish to partly greenish gray tuffaceous mudstone and sandstone in the lower part of theMizuyagadani Formation, being about 20 m
above the base of this formation. The stratigraphic succession at the fossil locality, from the baseupward, consists of: 1) greenish gray calcareous
shale which abounds with fragments of crinoids
and bryozoans (IO m), 2) alternation of graded
bedded sandstone and mudstone (60 m) whichis intercalated with an orthoceratid-bearing bed(5 m), and 3) gray sandstone interbedded withconglomerate (IOO m +). The lowest calcareous
shale contains well-preserved brachiopods andsuch fossil corals as: Sochkineophyllum japonicus Igo and S. j. pauciseptatum Igo, indicativeof Sakmarian age (Igo, 1959).
Associated faunas with orthoceratids include
pelecypods, brachiopods, corals, crinoids andforaminifers. Macrofossils are restricted in diversity and mostly fragmentary, whereas foraminiferal assemblage is diverse and relatively well-preserved, being characterized by dominant sessile
forms belonging to the genus Calcitornella. To
date, the following foraminifers have been
known: Agathammina spp., Calcitornella spp.,
Flectospira sp., Giralianella? sp., Hemigordius
schlumbergi (Howchin), Meandrospira australae(Crespin and Belford), M. meandrina (Crespin
and Belford), Nodosaria irwinensis Howchin, andTrepeilopsis australiensis Crespin. This foraminiferal assemblage bears a close resemblance to thatfrom the Middle Sakmarian Callytharra Formation of West Australia (Crespin, 1958; Waterhouse, 1976).

N

,
\

\

)

('\
\FUKUJI

TAKAYAMA.

)J"
?

-'

,'",r

/
,_.;},.I, ,....., ' '(' '- _ / I
"
It? I
'J

I

I
I

Figure 1.

-

/~-~-

~

o?

o~

.

'

0 '0

("-

o

Map showing the fossil locality in the Fukuji district, Gifu Prefecture.

1Km828. Permian Cephalopods from Fukuji
Systematic paleontology
Superfamily Pseudorthocerataceae
Flower and Caster, 1935
Family Pseudorthoceratidae
Flower and Caster, 1935
Genus Bitaunioceras Shimizu and Obata, 1936

Type species:-Orthoceras bitauniense Haniel,
1915.
Diagnosis:-Slender orthocones with circularcross section and relatively long camerae. Test
surface with a few shallow rounded transverse
constrictions and with many prominent transverse lirae of unequal size. Transverse constrictions representing internal thickenings of thetest. Sutures straight and transverse. Siphuncle
central, small with orthochoanitic to suborthochoanitic necks. Cameral deposits mural, episeptal and hyposeptal, well-developed. Endosiphuncular annuli developed on ventral side.
Discussion: - The genus Bitaunioceras was proposed by Shimizu and Obata (1936) based on
Orthoceras bitauniense Haniel from the Middle
Permian Bitauni beds of Timor. Distinguishingfeatures of this genus are "somewhat irregulartransverse striae and periodic constrictions", but
the structure of siphuncle and organic deposits ofthe type species have not been investigated.
Miller and Youngquist (1949) examined Bitaunioceras coahuilense from the Middle Permianof northern Mexico. They stated that "haveorthochoanitic siphuncles in which the septal
necks are straight and short, and connecting rings
are cylindrical", and put Bitaunioceras in the
Orthoceratidae. However, their figured specimens(pI. 8, figs. 3,4) are so poorly preserved that thebrim of those sepcimens probably disappeared
as a result of diagenetic dissolution and recrystallization.
Ristedt (1968) placed this genus in the family
Orthoceratidae with some reservations.
Examination of the Mizuyagadani specimens
clarified that this genus has orthochoanitic tosuborthochoanitic septal necks, well-developed
endosiphuncular annuli, and cylindrical rings
which are weakly constricted at the septal fora-

37

men. These features suggest that Bitaunioceras
should be referred to the Pseudorthoceratidae
and it was probably derived from the dolorthoceratid ancestor.
The following species have been referred tothis genus:
Bitaunioceras bitauniense (Haniel, 1915)
Artinskian, Timor
B. coahuilense Miller, 1944
Leonardian, Guadalupian, northern
MexicoB. elegantulum (Gemmellaro, 1890)
Sosioian, Sicily
B. gradatum (Gemmellaro, 1890)
ibid.
B. krotowi Dewingthal, 1951
(Shim an sky , 1954)
Sakmarian, Artinskian, Southern Urals
B. oeherti (Gemmellaro, 1890)
Sosioian, Sicily
B. texanum Miller and Youngquist, 1947
Wolfcampian, Texas
B. undulatum Niko and Nishida, sp. nov.
Sakmarian, central Japan (this report)
B. waageni (Gemmellaro, 1890)
Sosioian, Sicily
B. zonatum (Gemmellaro, 1890)
ibid.

Bitaunioceras undulatum
Niko and Nishida, sp. nov.
Figures 2-1-7,3-1-2.

Material:-Holotype, UMUT PM 17973 (Figures 2-5-6); paratypes, UMUT PM 17974 (Figures 3-1-2), UMUT PM 17975 (Figures 2-1-3),
UMUT PM 17976 (Figure 2-4), UMUT PM
17977 (Figure 2-7).
Diagnosis:-Bitaunioceras with small, slenderorthocone, relatively narrow transverse constrictions and long camerae. Siphunc1e central; septal
necks short and orthochoanitic to suborthochoanitic. Cameral and endosiphunclar deposits
well-developed in which episeptal deposits sometimes show mammillary growth.
Description:-Holotype, UMUT PM 17973:
The holotype is a portion of phragmocone, 36

Shuji NIKO and Tamio NISHIDA

38

3

Figures 2-1-7. Bitaunioceras undu/atum , sp. nov. 1- 3. paratype, UMUT PM 17975 , latera l view, x2.
4. paratype, UMUT PM 179 76, latera l view, x2. 5 , 6. ho lotype, UMUT PM 17973. 5 , vertical thin section,ve nter on left, x5.5. 6, en largement of vertica l thin sect ion, venter on right , x 10. 7. para type, UMUT PM
17977, thin cross sect ion, ve nt er o n rig ht , x8.

828. Permian Cephalopods from Fukuji
mm long, embedded in matrix. Cross section of
the shell is circular, expanding from 2.7 mm to
5.7 mm over the length of the fragmented specimen. Internal mold of the shell is marked byrounded transverse constrictions which representinternal thickenings of the test. There are two to
three septa between adjacent constrictions. Spacing of constrictions roughly corresponds to thatof the septa; septa generally join the shell wallnear the portion of constrictions. Camera long;
apically one camera occupies a length approximately equal to the corresponding conch diameter; adorally this figure increases to one and onehalf. Septal curvature moderate, but it becomessteeper near the shell wall. Siphunc1e is central;
septal necks are short and orthochoanitic to suborthochoanitic, joined by thin rings, which are
weakly constricted at the septal foramen. Diameter of the segments increases from 0.47 mm
in the most apical camera to 0.88 mm in themost adoral camera. Cameral deposits are foundthroughout the length of the specimen and almost completely fIll camerae. It can be differentiated into episeptal deposits, which sometimes
show mammillary growth, mural deposits andhyposeptal deposits. Circulus are developed insome camerae. Pseudorthoceroid annuli are developed within the siphunc1e along the ventral
siphunc1e wall. These deposits are originated in
the vicinity of the septal necks, and extend anteriorly along the connecting rings.
Paratype, UMUT PM 17974: This specimen isa portion of phragmocone in a more mature stage
than the holotype. Over a length of about 54 mm
the diameter of paratype increases from 3.9 mm
to 7.0 mm. The character of constrictions and its
internal morphology is roughly identical to thatof the holotype. Apically, about one and onehalf camerae occupy a length equal to the corresponding conch diameter; but adorally thecameral height is nearly equal to the corresponding conch diameter. Cameral deposits are welldeveloped.
Paratype, UMUT PM 17975: This specimen isa part of longiconic orthocone; 39 mm long.
Cross section of the shell is circular, expanding
from 3.7 mm to 6.7 mm over the length of the39

fragmented specimen. Sutures are straight andtransverse. Siphunc1e is circular in cross section
and central.
Paratype, UMUT PM 17976: This is a portionof phragmocone, 35 mm long. Suture are straightand transverse. Conch is slightly depressed, expanding from 5.0 x 4.5 mm to 6.4 x 7.4 mm overthe length of the specimen.
Paratype, UMUT PM 17977: This specimen
represents a transverse thin section of phragmocone. Cross section of the shell is circular,
and about 6 mm in diameter. Cameral deposits
are well-developed; ventrally, calcite of organic
deposits being remarkably dark in color. Siphunc1e is central, partly filled with endosiphuncular deposits of crescentic cross section.
Discussion: - These specimens show a considerable variation in morphology of cameral deposits, particularly the shape and development ofcirculus are variable even in the same specimen.
No surface ornamentation is preserved in the
Mizuyagadani specimens, probably because of
secondary alteration. Bitaunioceras krotowi
Dewingthal (Shimansky, 1954, pI. 7, fIgs. 1-5;
pI. 9, figs. 4-6; pI. 12, fig. 3) has about the same
dimensions with B. undulatum, sp. nov., but its
constriction is more broadly concave and theapical angle of its shell is larger.
Pseudorthoceratid, gen. et sp. indet.
Figures 3-3 -5.

Descriptive remarks:- This figured specimen(UMUT PM 17978) is a small fragment of weakly
annulated orthocone, 26 mm long. Cross sectionof the shell is nearly circular, and has near adoral
diameters of 6.2 mm. Siphunc1e is small, circularand slightly eccentric. Two to three camerae occurring per adoral shell diameter. Septal curvature is weak. Septal necks are not preserved. Connecting rings are sub cylindrical. Cameral deposits
are well-developed throughout the length of thisspecimen. These deposits are differentiated into
episeptal and mural deposits. Pseudorthoceroid
annuli occur around the necks.
Among the late Paleozoic annulated orthocone type cephalopods, this specimen showsShuji N IKO and Tamio N ISHIDA

40

1

4
Figures 3-1,2.
Bitaunioceras undularum, sp. nov. , paratype, UMUT PM 17974. 1, vertical thin section,
vent er on left , x4.1. 2 , e nlarge me nt of vertical thin sect ion , ve nter o n left, x8 .
3-5. Pseudorth oce ratid , ge n. e t sp. indet., UMUT PM 179 78 . 3, vertical thin sec tion , venter o n right ,x7 .5 4, enlarge ment o f verti ca l thin sec tion , venter o n left, x 15.8. 5, cross sect io n about 5 mm from ado ral end
o f th e spec im e n , ve nt e r o n right, x6.2.

828. Permian Cephalopods from Fukuji

41

Permian area northwest of Las Delicias, southwestern Coahuila, Mexico, Part IV, Permiancephalopods. Ibid., 52, p. 71-127, pis. 20-45.
--and Youngquist, W. (1947): Lower Permiancephalopods from the Texas Colorado River valley.
Kansas Univ., Paleont. Contr., Mollusca, Art I, p.
1-15, pis. 1-3.
- - and - - (1949): American Permian nautiloids.
Ceol. Soc. America, Mem., 41, p. 1-128, pis. 159.
--and Unklesbay, A. G. (1942): Permian nautiloids
from western United States. Jour. Paleont., vol.
16,p.719-738,pls.111-117.
Niikawa, I. (1978): Carboniferas and Permian fusulinids
from Fukuji, central Japan. Jour. Fac. Sci., Hokkaido Univ., Ser. 4, vol. 18, no. 4, p. 533-610.
--(1980): Geology and biostratigraphy of the Fukuji
district, Gifu Prefecture, central Japan. Jour. Ceol.
Soc. Japan, vol. 86, no. I, p. 25-36 (in Japanesewith English abstract).
Okimura, Y., Niko, S. and Nishida, T. (1984): Discoveryof michelinoceratinae nautiloids (Orthocerida) andcalcareous imperfolate foraminiferal assemblage
from the Permian Mizuyagadani Formation. Jour.
Ceol. Soc. Japan, vol. 90, no. 3, p. 2d-214 (inJapanese).
Ristedt, H. (1968): Zur Revision der Orthoceratidae.
Akad. Wiss. u. Lit., Abh. math.-nat. KI., no. 4,
p.211-287,pls.I-5.
Shimansky, V. N. (1954): Peyamiye Nautiloidei i
Baktritoidei Sakmarskogo i Artinskogo Yarusov
Yuzhnogo Urala. Akad. Nauk SSSR, Trudy Paleonto In st. , vol. 44, p. 1-156, pis. 1-12 (in Russian).
Shimizu, S. and Obata, T. (1936): Remarks on Hayasaka's Protocycloceras efr. cyclophorum and thePermian and Carboniferous orthoconic nautiloidsof Asia. Jour. Ceol. Soc. Japan, vol. 43, no. 508, p.
11-29 (in Japanese with English summary).
Waterhouse, J. B. (1976): World correlation for Permian
marine faunas. Univ. Queensland Pap., Dept. Ceol.,
vol. 7, p. 1-232.

closest affinities to the genera Cycloceras, Perigrammoceras, and Reticycloceras, but this figured specimen is too inadequately preserved todetermine both its generic and specific assignments.
References
Crespin, I. (1958): Permian Foraminifera of Australia.
Bureau Miner. Res. Ceol. Ceoph., Bull., no. 48, p.
5-207.
Gemmellaro, G. G. (1890): La fauna de calcari con
Fusulina della valle del fiume Sosio nella provincia
di Palermo. Ciorn. Sci. Nasur. ed Econ., vol. 20, p.
37-138, pis. 11-19.
Haniel, C. A. (1915): Die Cephalopoden der Dyas vonTimor. Paleont. von Timor, Lief 3, Abhandl. 6,
p. 1-153, pis. 46-56.
Igo, H. (1956): On the Carboniferous and Permian of
the Fukuji district, Hida Massif, with special reference to the fusuIinid zones of the IchinotaniGroup. Jour. Ceol. Soc. Japan, vol. 62, no. 728,
p. 217 -240 (in Japanese with English abstract).
--(1957): Fusulinids of Fukuji, southeastern part of
the Hida Massif, central Japan. Sci. Rep., Tokyo
Univ. Education, Sec. C, vol. 5, p. 153-246, pis.
1-15.
--(1959): Note on some Permian corals from Fukuji,
Hida Massif, central Japan. Trans. Proc. Palaeollt.
Soc. Japan, N. S., no. 34, p. 79-85, pI. 8.
Kamei, T. (1952): The stratigraphy of Paleozoic rocksof the Fukuji district, southern part of Hida mountainland. (Study on Paleozoic rocks of Hida I).
Jour. Fac. Lib. Art. Sci., Shinshu Univ., vol. 2, p.
43-74.
King, R. E. (1944): Geology and paleontology of thePermian area northwest of Las Delicias, southwestern Coahuia, Mexico, Part I, Geology. Ceol.
Soc. Am.. Spec. Pap., 52, p. 3-33, pis. 1-8.
Miller, A. K. (1944): Geology and paleonotology of theMizuyagadani *~ 'r~. Fukuji ttMt!!. Kamitakara
notani -(7)~.

J:::i:. Yoshiki 'EiJpj(. Osobudani Itiif.i~. Ichi-

IIit*"l}jHliijt!!jt!!n&(7)*~ 'r ~Jmt.P ':'IlEIH L t~......:'.JL.-L *clilJltIl~iilE.~R : IIit-'l'.~1'{Jpl(IlfU:3{:HIi'iijt!!jt!!t.o!((7)......:'./L.-L **~ 'r ~~ J: I) 2 fof(c7)jj(iJiJn.

Hitaun ioee ras undulatum Niko and Nishida,sp.nov.,
pseudorthoce ratid, gen. et sp. indet. ~ ~c,r& L t~ Bitaun ioee ras undulatum (-= ;l2.11:> .:, tL Q septal necks, organic depos i ts (J) Jf~!Th1J'':' Bitaunioee ras ~';j: Pseudorthoceratidae (-= 1';11:>':'tL Q .:: c HfIi tt.:o *~ 'r ~1li1(7)jjfiIE.Ulil:n';j: I,';];j'H1ffl ~ .:Ef* c T Q t;f~>d.· +1f~!ff1L!.hltf.C ~1<1lE
TQ o .::tL':'+~IHr1L91ftn(;j:......:'.JL.-L*ci1trltll (Sakmarian) ~jf,~TQo~.:.:y·il~jiJ· jl§Hlf~1$0

Trans. Proc. Palaeont. Soc. Japan, N. S., No. 146, pp. 42-48, 4 Figs., July 30, 1987

829. TINY AMMONITE WORTHOCERAS FROM HOKKAIDO*(STUDIES OF CRETACEOUS AMMONITES FORM HOKKAIDO-LX)TATSURO MATSUMOTO
c/o Department of Geology, Kyushu University 33, Fukuoka 812

and
KATSUJOH YOKOI
Sakae-machi, Kenbuchi, Hokkaido 098-03

Abstract.
On the basis of several tiny specimens obtained frol11 the mid-Cretaceous(probably Cenomanian) of the Shumarinai area, Hokkaido, by one of us (K. Y.) and Mr. Shunichi Hayashi, we describe a new species under the genus Worthoceras Adkins, 1928. It is similar
to W. rochatianus (d'Orbigny), frol11 the Upper Turonian of France, but is distinct in its small
size (about a half of that species) with fewer and broader whorls in the spirally coiled earlypart and the presence of blunt ventrolateral shoulders on the body-chamber which is broader
in section. Its suture is well shown, resembling that drawn by Collignon (1929) on an example
from the Cenomanian of Madagascar, which may be identical with ours.
In an appendix one of us (T.M.) attempts 'to consider the systematic position of Wortho·
ceras, a highly degenerated ammonite genus of a scaphitoid shape, proposing the family Worthoceratidae nov. It is cryptogenic in our present knowledge but could be presumed as indirectly
related to such a genus as Myloceras of the Labeceratidae.

T. M. for further study. We have communicatedwith each other, resulting in a conclusion thatthey represent a new species of Worthoceras,
which is described below.
The description in this paper not only marks
the first record of Worthoceras in Japan but alsopresents some interesting features which havestimulated one of us (T. M.) to consdier this problematic genus further. The remarks are to begiven in an appendix.
Acknowledgements:-Before going further, wewish to thank Mr. Shunichi Hayashi for his careful search for fossils and his kind supply of valuable specimens for our study. Thanks are also due
to Dr. Masayuki Noda for his friendly help intaking photographs, Miss Yoshimi Tanigawa forher assistance in preparing the typescript and also
to Dr. Jacques Sornay for his kind answer to ourinquiry about the French literature.

Introduction
The genus Worthoceras Adkins, 1928 contains
several, tiny and peculiar ammonite species
which have been reported to occur in the midCretaceous (Albian to Turonian) of Texas, Kansas, Europe, U.S.S.R. and Madagascar.
In the Katsujoh Yokoi Collection (abbreviatedhere to KYC.) there are at least six specimens
which are referable to a species of Worthoceras.
They were obtained by one of us (K. Y.) and also
Mr. Shunichi Hayashi, a friend of ours, from the
mid-Cretaceous (unit My3 of Hashimoto et al.,1965) of the Shumarinai-Soeushinai area, southern part of the Teshio Mountains, northwestern
Hokkaido. After a preliminary investigation by
one of us (K. Y.), these specimens were sent to*Received September 22,1986; read January 31, 1987
at Shizuoka University.

42829. Worthoceras from Hokkaido

43

Palaeontological description
Genus Worthoceras Adkins, 1928-------0Type species: -Macroscaphites platydorsus
Scott, 1924 (by original designation, Adkins,
1928, p. 218).
Remarks:-As for the systematic position ofthis genus see an appendix to this paper (p. 45).

+_oS

.~

B

"0

- c

Worthoceras pacificum sp. nov.
Figures 1-3,4-1-15.

Holotype:-KYC. 706 [GK.H8121],obtainedby K. Yokoi (581007) from the Sakin-zawa of
the Shumarinai area.
Paratypes:-KYC. 721, 722 and 723 in one
and the same nodule from somewhere (verypoint uncertain) in the Shumarinai-Soeushinai
area; H 74 and H 75 obtained from the River
Shumarinai by S. Hayashi who affiliated themwith KYC.
Diagnosis:-Shell very small, with Otoscaphites- or Macroscaphites-like shell-form; normally
about 10-11 mm in length except for a somewhat smaller example (see Table 1). Body-chamber hooked, starting at about the middle of theelongate shaft. Lappets may present at theperistome. Whorl somewhat broader than high;nearly flat or slightly concave on the dorsum androunded on outer parts. Body-chamber provided
with blunt but diagnostic ventrolateral shoulders.
Surface of shell nearly smooth. Fine lirae or
riblets may be seen but are much weakened.
Suture simple, consisting of E, L, U, I; E thelargest; L medium-sized and shallowly tripartite
Table 1. Dimensions in mm.
Specimens

L

W

H

B

B/H

d

KYC.706
KYC.723
H 74
H 75

10.7
11.0
7.2
-11.0

4.8

2.2
2.2
1.8
2.0

2.6
2.6
2.2
2.4

1.2
1.2
1.2
1.2

3.0

-3.2
-4.5

2.5

L=length of entire shell, W=width of hooked bodychamber, H=whorl-height in the posterior part of bodychamber, B=whorl-breadth at the same point as H, d=diameter of planispirally coiled part measured in parallelwith L; -: approximate.

IU;
~
~
l

I

I~

, i\

D
Figure 1. Worthoceras pacificum sp. nov.
Diagrammatic sketch of the holotype, KYC.
706 [=GK. H 8121]. A: lateral view; B, C:
cross-sections at the posterior part of bodychamber and at the late part (s) of phragmocone as indicated by dotted lines; arrow: position of the last septum; scale bar: 1 mm. D:
suture line at s.
(T. M. delin.)in the late growth-stage and V-shaped earlier;saddles between E/L and L/U broad, massive andbipartite; I narrow, pointed and tripartite in thelate growth-stage; saddle between I/U entire evenin the late stage.
Remarks:- The holotype seems to havelappets, but its outer portion is not well preserved. H 74 is somewhat smaller than others,
but it shows the same diagnostic features andoccurred in one and the same nodule with thenormal-sized H 75. It would be regarded as a
micro conch of a dimorphic pair, but its apertural
margin is not known. As its coiled part is also
smaller than others, it may be merely a malform.
Occurrence:-The described specimens were
all in calcareous nodules washed out as boulders
to the River Shumarinai, the Sakin-zawa andother tributaries of the River Uryu, as in manyother collections from the Shumarinai-Soeushinai
area. Among the associated fossils in the same
nodules, there are Stomohamites japonicus
Inoma, Anisoceras hashimotoi Inoma, Scaphites

44

Tatsuro MATSUMOTO and Katsujoh YOKOI

cf. japonicus Inoma etc. On the ground of previous works (Hashimoto et al., 1965; Matsumoto
and Inoma, 1975 and Inoma, 1980) an early
Cenomanian age of the host mudstone (indicatedby them as My3 of the Middle Yezo Group) issuggested, although intermingling with nodules
derived from the Albian strata cannot be denied.
Comparison: - This species is similar to"Macroscaphites" rochatianus (d 'Orbigny, 1850)(see Roman and Mazeran, 1913, p. 9, pI. 4, figs.
1-4; also Wiedmann, 1965, p. 439, pI. 60, figs.
4-6), from the Upper Turonian of the Uchauxbasin, S.E. France, but the former is much smaller, about a half of the latter, with fewer (i.e. 2.5
to 3 as compared with 3.5 to 4) whorls of thesmaller spire and shorter shaft of the succeeding
part. This marked difference in size would exceed the extent of variation in each of the populations in France and Japan, if sufficient numberof specimens were analysed. Examples of M.
rochatianus from Bohemia (Fritsch and Schloenbach, 1872) and Mangyshlak (Marcinowski,1980) are as large as the French specimens. No
suture has been illustrated on these specimens.
Accordingly, it is not certain whether or not M.
rochatianus has the same pattern of suture as
ours. Other criteria are the ventrolateral shoulders on the body-chamber and broader whorls inour species. Fine radial lirae may be discernible
on the surface of spire, as illustrated in one of
the figures by Roman and Mazeran (1913), but
the appearance of such a delicate ornament depends on the state of preservation.
A few specimens from the Cenomanian ofMadagascar described by Collignon (1929, p. 57,
pI. 7, figs. 8-10) ·under M. rochatianus may not
be the named species. They are incomplete but
as small as the phragmocone of our species. The
suture drawn by Collignon (1929, fig. 36) isquite similar to that of W. pacificum, and theMadagascan form can be called Worthoceras cf.
W. pacificum, although its body-chamber should
be searched for to confirm the identity.
On the ground of the small size, Macroscaphites- or Otoscaphites-like shell-form, nearlysmooth surface and simple suture of particularpattern as described above, this new species from

E

.

\I~

II

I'
.1

Figure 2. Worthoceras pacificum sp. nov.
The last second suture-line of KYC. 723.
Dotted line: dorso-lateral shoulder. Scale bar:
0.5 mm.
(T. M. delill.)---,,··0oFigure 3. Worthoceras pacificum sp. nov.
Unusually small form, H 74. Sketch as
in Figure 1.
(T. M. delil1.)

Hokkaido is evidently assigned to Wortlzoceras.
In view of the similarity to our species and also
the type species, M. roclzatianus can be called
W. roclzatianum, although its suture should be
examined on the French material.
Worthoceras platydorsul11 (Scott, 1924) (p.
18, pIs. 5,6; pI. 9, fig. 9) (see Adkins, 1928, p.
219, pI. 12, figs. 1-3), from the Albian (DuckCreek) of Texas, differs from W. pacificum in its
more rapidly enlarging body-chamber of comparatively wider hook in contrast to a tiny spire.
W. wortlzense (Adkins, 1920) (p. 71, pI. 2, figs.
23-26) (also Adkins, 1928, p. 219, pI. 20, fig. 8;
text-fig. 1; Wiedmann, 1965, pI. 59, figs. 6, 7),from the Pawpaw Formation (Albian) of Texas,
shows prorsiradiate, weak ribs and narrower
lobes of the suture.
W. vermiculum (Shumard, 1860) (see Moreman, 1942, p. 214, pI. 34, figs. 1, 2; Wiedmann,
1965, p. 440, pI. 59, fig. 8; pI. 60, figs. 1,2; text-

829.

Worthoceras from Hokkaido

figs. lOe-g), from the Britton Formation (lateCenomanian to early Turonian) of Texas andother regions (e.g. see Marcinowski, 1980), is distinguished from W. pacificum by its somewhat
larger shell, flat-sided and narrower body-chamber ending in wider hook and its peculiar laterallobe (L) modified to show an apparently bifid
aspect.
Owing probably to the degeneration in every
character, the morphological difference between
species of Worthoceras is by no means great, but
the distinction mentioned above is sufficient forestablishing a new species. There is also a difference in the geological age.
Appendix
Further remarks on Worthoceras
By Tatsuro Matsumoto
The fact that d'Orbigny (1850) recognized
this kind of tiny and peculiar ammonite is indeed
wonderful, but its systematic position has notbeen settled for a long time. The assignment of it
to Macroscaphites by authors of early decades inthis century must have been provisional, for they
depended on a superficial similarity in shell-form.
Adkins (1928) adequately introduced a new
genus Wort/wceras and honestly stated its suprageneric position uncertain. The two species fromthe Albian of Texas mentioned above were listed
by Adkins under this genus, but he did not touch
the European species. Subsequently, Moreman(1924) placed Worthoceras in the Scaphitidae(Scaphitinae in his paper), without mentioning
reason, and added to this genus W. vernziculunz
and W. gibbosum Moreman, 1942 from the Eagle
Ford Group of Texas.
More recently Wright (1953) has assigned
Worthoceras to the Otoscaphitinae Wright, 1953of the Scaphitidae, along with Otoscaphites
Wright, 1953, whereas Wiedmann (1965) has
reckoned it as an example of scaphitoid homoeomorphs, rejecting any connexion with Otoscaphites, and referred it to the Ptychoceratinaeof the Turrilitidae of his interpretation at that
date. The reason why Worthoceras should be

45

affiliated with the Ptychoceratinae is not satisfactory to me. I am not, however, so comprehensively acquainted with the scaphitid and scaphitoid ammonites as these two eminent palaeontologists are and have no definite conclusion at the
moment.
I have had a fundamental doubt in grouping
all the Cretaceous heteromorphs into the suborder Ancyloceratina Wiedmann, 1966, which
are said to show in common quadrilobate primary suture (see Matsumoto, 1984, p. 28). I should
evaluate a result of the Russian palaeontologists(e.g Doguzhaeva and Mikhailova, 1981; Mikkailova, 1983) who have investigated the microstructure in early growth-stage as well as the
sutural ontogeny. I would agree with their viewpoint that there are two major phylogenetic
groups in the Cretaceous heteromorphs. One is
the Turrilitaceae which belongs to the suborder
Lytoceratina (or order Lytoceratida by someauthors) and the other the Ancylocerataceae (ina revised sense) which is affiliated with the suborder Ammonitina (or order Ammonitida). The
lateral lobe L is originally bipartite (i.e. Iytocera tic) in the first group and tripartite (i. e.
ammonitic) in the second group, although a latermodification from bipartite to apparent tripartite
or vice versa may sometimes occur. The Scaphitaceae is now settled in the Lytoceratina.
Should the above major grouping be approved,
Worthoceras would be affiliated with the second
group (i.e. Ancylocerataceae) because of its originally tripartite L. [t is, however, cryptogenic in
our present knowledge. Considering the extreme
reduction in size, ornamentation and sutural incision, it would be better to propose an independent family for this peculiar genus. That is thefamily Worthoceratidae nov. What is the closest
relative of this group is not known at present. I
presume, however, that Worthoceras might beindirectly related to such a genus as Myloceras
Spath, 192 5 (see also Whitehouse, 1926) of the
Labeceratidae, which itself is a specialized group
distributed in the Albian shelf sea of the southern continents and debatable in its systematic
position. Anyhow, further study is required tosettle the problem.

46

Tatsuro MATSUMOTO and Katsujoh YOKOI

Figure 4 . Worthoceras pacificum sp. nov.
All figures magnified as follow s; 2, 5, 6, 10 and 12 are about x4 in linear dim ensio n; 8 a nd 13 about x4.5 ; 7 is
abo ut x3.6; ot hers a re about x2.0 to 2.75.1 -2: Ho lotype, GK. H 8121 [=KYC. 706) fro m Sakin-zawa of the
Shumarinai area (K. Yokoi Co li. , 1983-10-7). 3-6 : KY C. 723 from somew here in the Shumarinai-S oeushina i
area (K . Yoko i CoIL). 7 -8: H 74 obtained by S. Hayashi frolll the Riv er Shumarinai, now kept at KYC. Th ere isa seconda ry displacement at th e last septum. 9- 10: H 75, ditto. 11 - 13: KYC. 72 1 from the same nodule as
KYC. 723.14 - 15: KYC. 722 , ditto. Hooked part is distort ed in KYC. 721 and 722.
Phot os by co urtesy of Dr. M. Noda , w ith out w hitening.

829. Worthoceras from Hokkaido
References cited
Adkins, W. S. (1920): The Weno and Pawpaw formations of the Texas Comanchean. Univ. Texas Bull.,no. 1856 (1918), p. 3-172 (incl. pis. 1-11).
- - (1928): Handbook of Texas Cretaceous fossils.
Ibid., no. 2838, p. 1-303, pis. 1-37.
Collignon, M. (1928-29): Les cephalopodes du Cenomanien pyriteux de Diego-Suarez. Ann. Paleont.,
vol. 17 (1928), p. 137-160 [1-24]. pis. 15-19[1-5], vol. 18 (1929), p. 1-56 [25-79], pis. 1-2[6-7].
Doguzhaeva, L. and Mikhailova, I. (1981): The genus
Luppovia and the phylogeny of Cretaceous heteromorphic ammonoids. Lethaia, vol. IS, p. 55-65.
Fritsch, A. and Schloenbach, U. (1872): Cephalopoden
der bohmischen Kreideformation, 51 p., 16 pis.,
Prag.
Hashimoto, W., Nagao, S. and Kanno, S. (1965): Soeushinai. Expl. Text. Ceol. Map Japan, scale 1:
50,000, 92 p., map. Hokkaido Developm. Agency,
Sapporo (in Japanese with English resume).
Inoma, A. (1980): Mid-Cretaceous ammonites from the
Shumarinai-Soeushinai area, Hokkaido. Part II. In
Igo, H. and Noda, H. (eds.): Professor Saburo Kanno Memorial Volume, p. 167-183, pis. 21-22,
Univ. Tsukuba.
Marcinowski, R. (1980): Cenomanian ammonites from
German Democratic Republic, Poland and Soviet
Union. Acta Ceol. Polonica, vol. 30, p. 215-325,
pis. 1-20.
Matsumoto, T. (1984): Some ammonites from theCampanian (Upper Cretaceous) of northern Hokkaido. Part I. Palaeont. Soc. Japan, Spec. Pap., no.
27, p. 5-32, pis. 1-9.
--and Inoma, A. (1975); Mid-Cretaceous ammonites
from the Shumarinai-Soeushinai area, Hokkaido.

47

Part I. Mem. Fac. Sci., Kyushu Univ., Ser. D, Ceol.,
vol. 23, no. 2, p. 263-293, pis. 38-42.
Mikhailova, I. A. (1983): Systematics and phylogeny ofMesozoic Ammonoidea, 280 pp. (in Russian).
Acad. Sci. USSR, Moscow.
Moreman, W. L. (1942): Paleontology of the Eagle
Ford Group of north and central Texas. Jour.
Paleont., vol. 16, p. 192-220, pis. 31-34.
Orbigny, A., d' (1850): Prodrome de Pateontologie
stratigraphique universelle des animaux mollusqueset rayonnes., vol. 2, 428 pp., Paris.
Roman, F. and Mazeran, P. (1913): Monographie
paleontologique de la faune du Turonien dubassin d'Uchaux et de ses dependances. Arch. Mus.
Hist. Nat. Lyon, vol. 12, p. 1-137, pis. 1-11.
Scott, G. (1924): Some gerontic ammonites of the Duck
Creek Formation. Texas Chr. Vniv. Quart., vol. 1,
p.5-31.
Spath, L. F. (1925): On Upper Albian Ammonoidea
from Portuguese east Africa, with an appendix on
Upper Cretaceous ammonites from Maputoland.
Ann. Transvaal Mus., vol. 11, p. 179-200, pis. 2837.
Whitehouse, F. W. (1926): The Cretaceous Ammonidea
of eastern Australia. Mem. Queensland Mus., vol.
8, pt. 3, p. 195-242, pis. 34-41.
Wiedmann, J. (1965): Origin, limits, and systematic
position of Scaphites. Palaeont., vol. 8, p. 397453, pis. 53-60.
--(1966): Stammesgeschichte und Sytem der posttriadeschen Ammonoideen. Ein Oberblick (2. Teil).
N. Jb. Ceol. Palaont. A biz. , vol. 127, p. 13-81,
pis. 3-6.
Wright, C. W. (1953): Notes on Cretaceous ammonites.
I. Scaphitidae. Ann. Mag. Nat. Hist., Ser. 12, vol.
6, p. 473-476.

Kenbuchi \liiJiNM, Sakae-machi ,*Plf, Sakin-zawa fi'J.<r.:il!, Shumarinai *~~JI*J, Soellshinai i{';'I"II~,Teshio ~j:1£, Uryu F:MTi'i:.

P.S. Reply of Dr. Jacques So may to Matsumoto's inquiry about the date of Worthoceras rochatianum(d'Orbigny) (in letter of Sept. 1, 1986): Scaphites
rochatianus is stated as n. sp. by d'Orbigny in a list offossils in the last chapter concluding the volume "Paleontologie Fran~aise, Ammonites Cretaces" publishedin 1847. But, there, it is a nomen nudum without description nor illustration. TIle first valid description isin his "Prodrome" vol. 2, 1850 (p. 147, no. 35). Certainly authors should have explained in their synonymies that the first citation in 1847 was a nomen nudum.

Tatsuro MATSUMOTO and Katsujoh YOKOI

48~tifl~jUi!€C')/H\'17 /' 'E -)-1 J-:z, [9;'J-[-1 (7"7 /' :z*),Wo rthoce ras: ::. C')~Ij:+1\'i-C",,*tI'V >J: ifYI!J: ~ ff-TiJ<, ~t*T ot-tt'J j!)!;, ?1'-J/:z 7) il--C')8iJE,*iJ'G 5 H(iJ'~ Gn -C".Qo -<f1!!l~tm;gF:f:i

1¥tll!;*~'1H"J!t!lMC') My 3 fff,Jlil (t.= ,,;~Iv -t J?.:=.7 /' ~fff,) iJ' G jil't# Utf:lt-!:\iJ't** Lt.=t~2f>: 6
f[l;jiJ'n;JJiJiC') 1 t.fl-C", tet~C') c"C')t.J\ c {; m~1j ~ tL.Q::' c iJ'hiJ' ') t.=o 9=' -C" W. rochatiarum (d'Orbigny) (fL" T;L-O.:=.7/,i!€) C W. vermiculum (Shamard) (Tot-tt:z Britton Jlili!€) 1:'ij(fL:J,
T.Q iJ', of h G .J: t) ~[.:>H'i -C", scaphitoid 1f;C')~,n~ffl; {; fl\llYt.=fff,5t {; ;f!HtB~[:$rJJ.t < (H < B),
tu~ (f¥:lkffl'C')9='fH)p/fo) IHl-mIJff!I-C"j4iH'i iJ'~I~ t), 7f-fmlj: A, 'iJ', J1;JmUllDlj::ijZlT-C''d.· < -C J1;J I:
fl:j'( < l.'HI'XiJ'ji,.Q 0 J1;Jillilj:~JL.tIl.iJ·Y L < 11'\:.,'0 ~{-t-¥JjUj:I'&C')iffi t) "'C'? '1"//7. 7) Jl--C')-t J ?.:=.7 /' i!€C')1:j!:l.Qo 7\J~At;l'l2f>:C')\\1L1f*'C')jP.IJillil:Ij:"7"-":'~ J- G L,' {;C')~~,,9').Qo ¢'1Tt,f( Worthoceras
pac ificum Un-t L -C rtci£ Lt.= :i.\::ijZ;$!K -C"IH1J,9')-C C')i!€!B~cJ.'kl'ji,.Q
t1:2f>:iiflf, , ff!!#ffi:f};j(
0

0

1i£~.

Worthnceras 1:",)"-CC')i.~j£: *~C'),**,t:7Hiil".C')f.il:ii','ftltl:IHn~!lliiJ'ji, t) iR:7lifL-C,·7'j:"0 (iIJ~&1§- Adkins(l928) 1j:~nJJ c Lt.=o Wright(l953) Ij: Scaphitidas 1:J..n Otoscaphites Uf,;1~C Lt.=iJ', Wiedmann(l965) lj:i&i'iclj:Jw.IMjj,f:-c"fL:J.-c~F7'j:.Q scaphitoids C')Hj§lj
C L, Ptychoce ra tinae (Turr il itidae) I: -J"lf I/~ ~ -tt t.= ,']ilIi.j;cC') ~ 1\\ If,'i 7 /' 'E -)- 1 ~ ~ Ancyloceratina 'lP:§I:-jfiT.Q Wiednann(l966) C')'iHii~iJ'-<fB1'f1Jt.:"iJ'~r.M'ji,.Qo #:!tflJAAC')'J1C')jWH[llflli@ c ~-g.*Jj[iJ· G Mikhailova( 1983) iJ'illI. < .J: -) I:, Lytoceratina.ill'. § I: J....Q Turrilitaceaec Ammonitinai!Ii.§I:J...tL.Q"-":i!< Ancylocerataceae C') 2 *'*if.Jt~ilE.,9')t.="o 'd.'j;Scaphitaceae Ij: Lytoceratina "'C'ji,.Q Worthoceras ~;f.LIH&i'i (Ammonitina) C h7'j:TiJ\
T"-":-C C') .','1: "'C'iIHtiJ'~ L " ~#§*'d.' 1'lMR 'd.'C') -C", Worthoce ra tidae ~ -iRoUIol L t.=" of C') @:t~C') ~im\'j:*~'f. (cryptogenic) -C-ji,.QiJ', Labeceratidae C') MylocerasC').J: -) 'd.' {;C')I:rB9:tt8~7'j:lmf*iJ';h .Q iJ' {;miL 'd.',' ~T.Q I: "l-i&C')'jE aJJiJ',Q'~ -C-;h .Q
t~2f>:iiflr\
0

0

0

0

0

Trans. Proc. Palaeont. Soc. Japan, N. S., No. 146, pp. 49-76,12 Figs., July 30, 1987

830. PLEISTOCENE OSTRACODA FROM THE ATSUMI PENINSULA,CENTRALJAPAN*
MICHIKO YAJIMATokyo Seitoku Gakuen, Toshima, Kita·ku, Tokyo

Abstract. Pleistocene Ostracoda occur abundantly in an excellent state of preservationfrom the Akazawa Silt Member and the Takamatsu Shell Sand of the Toshima Sand Member,
both of the Tahara Formation exposed along the Pacific coast of the Atsumi Peninsula, central
Japan. The ostracod assemblage found in the Akazawa Silt Member consists of embayment
dwellers with a low species diversity. This assemblage is mixed with Zostera sand dwellers in thelower and middle parts of the Akazawa Silt Member. Ostracods are scanty in its upper part. The
Takamatsu Shell Sand contains in its lower half a silty-bottom dweller assemblage with a low
species diversity and in its upper half a mixture of offshore-sand, nearshore-sand and mud
dweller assemblages with a very high species diversity. Ostracods are represented by 101 species
belonging to 55 genera. Among them there proposed are one new genus, eight new species and
14 species in open nomenclature.

Okada, personal communication, 1983). But theexact age of these strata is ambiguous because of
the absence of a good age-indicator for assigningthem to the subdivision of the Pleistocene.
Correlating terrace deposits along the Pacific
Coast of the Honshu Island is most helpful indetermining the age of the Tahara Formation. An
early Pleistocene age has been assigned to the
Atsumi Group (Tsuchi, 1960).
The description of five new molluscan species
from the Akazawa area by Yokoyama (1926)
was the beginning of paleontological studies of
the Atsumi area. He believed that the age of theformation is Pliocene based upon these molluscs.
Oinomikado (1933) distinguished Ostrea Bed andCorbicula Bed in the Akazawa Silt Member and
Batil/aria Bed, Dosinia Bed, Mya Bed, and Tonna
Bed in ascending order in the Takamatsu Shell
Sand. He concluded that the age of the formation is Pleistocene and that these molluscs belong
to the Kuroshio (warm current) fauna. Hayasaka's (1961, 1962) work on the geology and paleontology of the Atsumi Peninsula was the mostextensive in terms of the area covered and ofgiving a superb observation of sedimentary struc-

Introduction
Pleistocene strata, over 80 m thick, crop out
along the Pacific coast of the Atsumi Peninsula,central Japan. They extend for about 50 km
from Hamana-ko Lake (east end) to the Irako
Cape (west end) (Figure 1). The strata dip very
gently westward. Coastal cliff exposures enable
us to trace lateral change of sedimentary facies
over several kilometers. The Pleistocene strata(the Atsumi Group of Figure 2) directly overlie
the so-called Chichibu System (Paleozoic blocksof various size embedded in Mesozoic sediments)
and can be divided into the Tahara and Toyohashi Formations in ascending order. Abundantfossils of molluscs, ostracods and barnacles arewell preserved in the Akazawa Silt Member andthe the Takamatsu Shell Sand of the Toshima
Sand Member, both of the Tahara Formation
which are exposed in the Akazawa, Takamatsu,
and Akabane areas (Figure 1).
Nannofossils indicate a Pleistocene age (N.
*Received October 4, 1986; revised manuscript received
May 11, 1987.

49

Michiko YAJIMA

50

DA

.8
o

5

138·

40·+

10km

ATSUMI BAY

TAKAMATSUAKAZAWA

Figure 1. Index map and the studied area. A: Atsumi Group, B: the so-called Chichibu System (Paleozoic to Mesozoic).

tures. Kuroda's (1966, 1967) work on plantleaves provided additional knowledge on glacial
and interglacial climatic changes of land area. A
recent study by Honda (1975 MS) presented agood summary of the stratigraphy. Althoughopinions differ slightly among various authors
with regard to stratigraphic assignment of terrace
deposits, the overall stratigraphy of the Atsumi
Group was established already by Kuroda andHonda. Furthermore, most of the molluscan
fossils from the peninsula have also been described by Hayasaka (1961). However, ostracodsof the Atsumi Group have not yet been describedin spite of their abundant occurrence and excel-

lent state of preservation. This study gives a full
picture of warm-water ostracods that lived in anear-shore area influenced directly or indirectlyby the Kuroshio Current flowing along the Pacific coast during the Pleistocene.
I am much indebted to Drs. Tetsuro Hanai
and !taru Hayami of the University of Tokyo,
Dr. Noriyuki Ikeya of Shizuoka University, Dr.
Kiyotaka Chinzei of the University of Kyoto,and Dr. Toshiyuki Yamaguchi of Chiba University and to Mr. Hiromi Honda of JAPEX for theiradvice during my field as well as laboratory
work. Dr. Paul Frydl read and improved themanuscript, and I am thankful for his assistance.

830. Pleistocene Ostracoda from A tsumi
MEMBER
J: Z

a..
::>
0

a:

(J)

0

0

::=;

< ~
J: <

)0-

0
I-

a:

T

SAND

u.

TERASAWA S.
TON AMI GRAVEL

~

en

....
«

z

< 0
a: ~
< <
J: ::=;
< a:

I-

~E

SUGIYAMA

0::>

W ....

0

~

~

51

0
u.

TOSHIMA SAND

I

0

UiliiilliY:UH.·::::·::.·::::>.:·:::.:·:·:::::::-:HH::::,·HH·::::::::::::'::::.::.:'.5--':":::-:./:::":'::'::":,:::TAKAMATSU"::::}~~~:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::HIGASHIKANBEIt)~AKAZAWA SILT
It)

o

Skm

AKAZAWAIKOBE GRAVEL

eli

Figure 2. Stratigraphic units and schematic stratigraphic sequence. A: silt to clay, B: sand, C: gravel,
D: cross lamination, E: molluscan shells, T: thickness in meters.

Field observation
The following observations on lithofacies andmolluscan biofacies clarify the environmental setting of the fossil ostracod assemblages.
1. Akazawa Silt Member
The Akazawa Silt Member is distributed from
Shiroshita eastward to Hamana-ko Lake (Figures
1 and 3). Deposition begins with a cobble layer
about 50 cm thick, which is characterized by flat
pebbles and cobbles of limestone and chert. The
boundary between the basal Ikobe Member andthe Akazawa Silt Member is not exposed. The
Ostrea Bed reported by Oinomikado (1933) andHayasaka (1960) from Akazawa is now coveredby coastal sand deposits.
The Akazawa Silt Member grades upwardfrom the pebble-cobble bed to a micaceous, finesandy silt bed. The bed is 2 meters thick and contains besides pebbles and granules, aggregationsof Corbicula japonica Prime. The bed probably
corresponds to the Corbicula Bed of Oinomikado(1933). Associated molluscs are authochthonous,
preserved in living position. Mya arenaria Linnaeus with their long-axis arranged vertically areoften distributed at uniform intervals on one

bedding plane, whereas Dosinia angulosa Phillippi occurs sporadically. Abundant, partiallyinterconnected burrows about 30 cm in length,
penetrate nearly vertically into the bed. Sincemodern Corbicula japonica lives in lagoons,estuaries, and other brackish water environments,
these Corbicula shells were probably transported
together with pebbles from a brackish water
environment to the shallow sandy silt bottom
inhabited by Mya arenaria.
The upper part of the lower half of the Akazawa Silt Member consists of a sandy silt dominated by Dosillia angulosa. Raeta pulchera. Mya
arenaria. and Corbicula japonica which occurs
in an appreciably amount. Most of these molluscs
appear to have been transported only for a shortdistance.
The upper part of the Akazawa Silt Member
consists of a thick silt or clay layer of about 10
m in thickness. Raeta pulchella and Dosinia
angulosa occur in a massive bluish gray micaceous silt with plant fragments. A laterally continuous, 10 cm thick pinky white tuffaceousband is present in the lower 1 or 2 meter level ofthe silt.
The Akazawa Silt Member consists of trans-Michiko YAJIMA

52

gressive deposits in its lower half and of stabilized embayment sediments in its upper half.
2. Takamatsu Shell Sand in the Toshima Sand
Member
The Toshima Sand Member consists in generalof shallow water sand. Well-developed cross lamination observable in the Higashikanbe area suggests deltaic deposition (Figure 2). The distribution of silty sediment is restricted to the Takamatsu and Ura areas. In the Takamatsu area, alenticular body of silt of about 10m in thickness
and containing abundant molluscan fossils is
traceable for more than 1 km along the coastal
cliffs (Figure 4). Hayasaka (1961, 1962) named
this sediment body the Takamatsu Shell Sand.
Oinomikado (I933) distinguished four shell bedsin this unit. The lowest Batillaria Bed is no longer
exposed.
The lower Dosinia Bed, 1.2 m thick, consistsof a silt with abundant burrows and is characterized by autochthonous assemblages of Dosinia
angulosa and Barnea japonica. The silt is piercedby abundant, near-vertical branched burrows,
reaching 2 cm in diameter and 30 cm in length.

The middle Mya Bed, 20 cm thick, consists ofa sand and is packed densely with molluscs mostly transported from nearby areas. Mya arenaria
dominates and some of the specimens still keep
their living position.
The upper Tonna Bed, 2m to 6m thick, consists of a bluish gray micaceous silt with abundant molluscs and barnacles scattered throughout
the bed. The fossil assemblage is dominated by
Tonna luteostoma, Fulvia mutica, Solen grandis,
and Balanus rosa. Although no appreciable verticalor horizontal variation in the number of
species present exists, Solen grandis dominates
the middle part and Tonna luteostoma andFulvia mutica are most abundant in the upper
part rather than the lower part of the Tonna Bed.
Analysis of sedimentary facies and molluscan
and barnacle fossil assemblages suggests thatearly deposition of the Takamatsu Shell Sand
took place in an embayment. Later, the embayment became open towards the off-shore andopen coastal water deposition prevailed.

----D.l

.,

.,

PI

2425
15 17
26272850om
16 181920212223 0L..-'-....L..--'--.L..-J

2930

bdADB~C!Y:YIDWE0F

Figure 3. Stratigraphic succession at Akazawa. Large numerals represent locality numbers.
Small numerals represent sample numbers. A: silt to clay, B: sandy silt, C: sand with gravel, D:
tuff layer, E: ostracod sampling position, F: ostracods absent.

53

830. Pleistocene Ostracoda from A tsumi

.1

1

.~3
i

1
§

A

2
~
~

B

56

3 4

m

c

o

-7

8
200m

~2

•

"'!'.'

IE

12

911 '1 12 I 14
10

13

Figure 4. Stratigraphic succession at Takamatsu. Schematic figure shows outcrop of the Takamatsu
Shell Sand in the Toshima Sand Member. Large numerals represent locality numbers and small numerals represent sample numbers. A: silt; Dosinio Bed, B: sand, Tonna Bed, C: ostracod sampling horizon. Ostracod samples
on the line between A silt and B sand are taken from the Mya Bed of about 200m thick.

Ostracod fauna
Ostracods occur in the Akazawa Silt Member
and in the Takamatsu Shell Sand of the Toshima
Sand Member. Sediments containing ostracods
are all mud-rich. The Terasawa Sandy Silt Member of the Toyohashi Formation is also high in
mud content, but no ostracods have so far beenrecorded from the formation.
Sampling was designed in such a way as toelucidate horizontal and vertical changes of ostracod assemblages in the sediment. The following
four assemblages were distinguished:
A: Bicornucythere bisanensis-Aurila subconvexa assemblage in the lower Akazawa Silt Member (Corbicula Bed)
B: Bicornllcythere bisanensis assemblage inthe upper Akazawa Silt Member (Dosinia Bed)
C: Bicornllcythere bisanensi-Neomonoceratina microreticlilate assemblage in the lower
Takamatsu Shell Sand (Dosinia Bed)
D: Pistocythereis bradyformis-Bythocythere

ishizakii assemblage in the middle and upper
Takamatsu Shell Sand (Mya Bed and Tonna Bed)
A: Bicornllcythere bisanensi-Allrila sllbcOllvexa assemblage
Samples obtained from the lower Corbicliia
Bed exposed along the cliff from locs. 16 to 30
were examined (Figure 3). No ostracods were
found in samples from locs. 16, 17,29, and 30.
In general, ostracods are common in samples
1801, 1902, 2003, 2101, 2303, 2402, 2603,
2605, and 2801 except for sample 2605 (Table1). Rareness of ostracods in sample 2605 seems
to be a result of poor preservation state. No appreciable lateral change of combination of
species is detectable throughout. This assemblage
is characterized by the dominant occurrence of amud dweller Bicornllcythere bisanensis and by a
low species diversity. A Zostera sand dweller,
Aurila sllbconvexa is abundant and represented
exclusively by adult specimens. The number ofindividuals of A. subco/1vexa exceeds that of B.
bisanensis in sample 1801, and equals B. bisa-

Michiko YAJIMA

54

Table 1.

Ostracoda from the Akazawa Silt. Sample number consists of four digits. The first two digits indicate
the sampling locality, and the next two digits indicate the sample number in a descending samplingorder.

~r
Species

1801 1902 2003 2101 2303 2402 2603 2605 2606 2801

Pontocythere japollica (Hanai)
Parakrithella pseudadollta (Hanai)
3
Neomolloceratina miaoreticulate Kingma
Spillileberis quadriaculeata (Brady)
22
Trachyleberis scabroculleata (Brady)
122
T. sp.
Australimoosella tomo/wae (Ishizaki)
Bicorllucythere bisanellsis (Okubo)
70
Aurila subcollvexa (Kajiyama)
138
Loxoconcha tosaellsis Ishizaki
8
Cytheromorpha acupullctata (Brady)
13
total number of individuals
total number of species
weight of sample (in gram)

2501 2701

2

2
55
9
7

37
38
8
42

2

84

9
2

2

10

22

56
46

7
9

12
3

28 12418 117

2

28

55
13

3
4

28

85
3

2

268 143 143 113
5
4
8
7
10
10
80
40

nensis in samples 1902,2101,2303,2603, and2605. Because all the species other than A. subconvexa are represented by both adult and immature specimens, selective transport of carapaces is the most likely cause of the occurrenceof only adult carapaces of A. subconvexa. The
Zostera zone was probably located near a site of
mud deposition. Associated species consist of
mud dwellers, such as Spinileberis quadriaculeata(common), Cytheromorpha acupunctata (rare),and Neomonocaratina microreticulate (only insample 2003), sandy mud dwellers, such as
Trachyleberis scabrocuneata and T. sp. (rare),and sand dwellers, such as Loxoconcha tosaensis, Pontocythere japonica, and Parakrithella
pseudadonta (very rare).
Bicornucythere bisanensis and perhaps othermud dwellers are likely to be autochthonous,
and other species are derived form nearby sites.
In spite of the abundant occurrence of brackish
water Corb icu la, no brackish water ostracods
have so far been found in the Akazawa Silt Member.
B. Bicornucythere bisanensis assemblage
A massive silt bed characterized by the occurrence of Dosinia angulosa and Raeta pulchella is
exposed from loco 15 eastwards to Hamana-ko

10

18
3
80

25
3
80

68 251
3
3
80 80

4

2
20

96
3
80

31
3
80

95
4
80

Lake (Figure 3). Ostracods occur rarely in samples 2501 and 2701 (Table 1). No ostracods were
found in samples 1501, 1502, 1901, 2301,
2401, 2601, and 2602. In general, ostracods arevery rare in this silt bed. The only species foundin abundance is Bicornucythere bisanensis. Species diversity is low. Other mud dwellers, Spinileberis quadriaculeata and Cytheromorpha acupunctata, occur very rarely. Other extremely rare
species include Trachyleberis scabrocuneata
derived from sandy mud bottom and Loxoconcha tosaensis from sand bottom of nearby
areas.
Ostracod fauna endorses my field observations
that the emb"ayment become stabilized during deposition of the upper part of the Akazawa Silt
Member.
C. Bicornucythere bisanensis-Neomonoceratina microreticulate assemblage
Ostracods occur commonly form the Dosinia
Bed of the Takamatsu Shell Sand extending overa distance of 700 m from loco 1 to loco 14 along
the sea cliff (Figure 4 and Table 2). Species diversity of the assemblage is low except for samples
0302, 0402, 0803, and 1112. Among samples
yielding high species diversity assemblages, samples 0302 and 0402 are a shell sand picked from

830. Pleistocene Ostracoda from Atsumi
Table 2.

Ostracoda from the Takamatsu Dosinia Bed.

~
Species

0101 0201 0301

Cytherelloidea 1Il1Hll'ehi/wi Ishizaki
Neollesidea hallaii, n. sp.
Aglaiocypris nippolliea Okubo
Pontoeythere japoniea (Hanai)
P. miurensis (Hanai)

Cythere omotenipponica I-lanai
Hanaiborchella triangularis (Hanai)
Neomonoceratina microreticu/ate Kingma
Spinileberis quadriaculeata (Brady)S. /uruyaensis Ishizaki and Kalo
Traehyleberis scabrocuneata (Brady)
T. sp.
Pistoeythereis brady/ormis (Ishizaki)
Bicornucythere bisanensis (Okubo)
Australimoosella tOl1lokoae (Ishizaki)
Aurila subconvexa (Kajiyama)A. uranouchiensis Ishizaki
Robustaurila ishizahi (Okubo)
Cornucoquimba tosaellsis (Ishizaki)
Coquimba ishizakii Yajima
Bythocythere ishizakii, n. sp.
B. maisakensis Ikeya and Hanai
Cytherura ? miii (Ishizaki)
Hemicytherura cUlleata Hanai
H. tricarillata Hanai

030~

0401

040~

o~o~

0703 OS03 0920 1112
1

140~

3101

2
5

3
1
4
6

P. subjaponiea (Hanai)
Parakrithella pseudadollta (Hanai)
MUllseyella japoniea (Hanai)
Callistocythere reticulata Hanai
C. rugos%rma Hanai

16

1

3
4

2

8

2

2
2

1

9

51
1

1
1

5

1

1

2

33
2

1 58
1
2
3

14 108
4
1
2
3

75

204

1
37 118

2
1

6
1
1

4
1
16
2

7
3

3
7
5
20

2
1
6
41 153 117 155

2
74
2

49 85
2

1
1

1
3

6
4

1

1
3

1

1
4

3

1

1

2
1
1

1
7
1

2

1
2

12
1

3
1
2
1
2
1
8
3
38 83 131

3
1

3

Semicytherura 11liurensis (Hanai)
Cytheropteron 1Ichioi Hanai
Paracytheridea bosoensis Yajima
Loxoconcha optima Ishizaki
L. uranouchiensis Ishizaki

1

1
2

1

1
1

2
2
1

Miia uranouchiellsis Ishizaki
Nipponocythere biearillata (Brady)
X estolebeis hanaii Ishizaki
X. setouchiensis Okubo
Paradoxostoma conveXU11l Okubo

1
2

2
6

1

I
1
3

3

1
1

2

1

I
1
1

1

Sclel'ochilus 1Ilu/wishimensis Okubo
Cytherois? asamushiensis Ishizaki
C. zosterae Schornikov
Cytheroma ? sp.
Paradoxostoma sp.

1
1
2

1

3
1

3
1
1

1

1
1
1

Cobanocythere pu/eilra, n. sp.
Hanaicythere ni/Jponica, n. gen. et n. sp.
total number of individuals
total number of species
weight of sample (in gram)

55

'I
1
1

114
5
80

2 275 78 27:) 108
2 10 159 22
80 40 80 20 80

54 232 207 2·16 115 159
6 26 156
5 23
80 20 40 10 80 20

65
10
80

56

Michiko YAJIMA

the inside of burrows. Shallow water mud dwellers, Bicornuchthere bisanensis and Neomonoceratina microreticulate, dominate the assemblage of low species diversity. Other mud bottom
dwellers, Spinileberis quadriaculeata and S. furuyaensis, are rare and Cytheromorpha acupullctata
has not yet been found. Rare species transported
from nearby environments, probably after death,
include sandy silt dwellers (Trachyleberis scabrocUlleata and Pistocythereis bradyfom1is), Zostera
sand dwellers (Loxoconcha optima, L. urallouchiensis, Aurila subcollvexa and A. uranouchiensis), and sand bottom dwellers (Pontocythere
spp., Callistocythere reticulata and Cythereomotenipponica). Very fragile, thin carapaces ofintertidal species (Xestoleberis spp., Paradoxostoma spp., Cytherois sp., and Paracytheromasp.) occur rarely but they are well preserved.
Species composition seems uniform throughout
the Dosinia Bed of the Takamatsu Shell Sand.
A bed equivalent to the Dosillia Bed is also
exposed in the Ura area on the northern coastof the Atsumi Peninsula (loc. 31). Sediments
there consist of a bluish gray micaceous sandy
silt, characterized by autochthonous Mya arenaria. The ostracod assemblage (sample 3101) isalso dominated by Bicornucythere bisanensis
and Neomonoceratilla microreticulate.
D. Pistocythereis bradyformis-Bythocythere
ishizakii assemblage
Ostracods of a very high species diversity occur in the Mya Bed and Tonna Bed of the Takamatsu Shell Sand (Figure 4 and Tables 3,4). The
assemblage is dominated by a sandy silt dweller,
Pistocythereis bradyfom1is and is admixed withspecies from many different habitats as follows(cf. Hanai et al., 1977):
Tide pool dwellers: Xestoleberis hanaii, X.
setouchiensis, X. sagamiensis, Paradoxostoma
elongatum, P. setosum, Cytherois zosterae, andSclerochilus mukaishimellsis.
Zostera sand dwellers: Loxoconcha optima, L.
tosaensis, L. uranouchiensis, Aurila subconvexa,
A. uranouchiensis, Robustaurila assimilis, and R.
ishizakii.
Shallow water sand dwellers: Pontocythere
japollica, P. miurensis, P. subjaponica, Callisto-

cythere reticulata, and Cythere omotenipponica.
Shallow water sandy silt dwellers: Pistocythereis bradyfom1is (dominant), Trachyleberis
scabrocuneata, T. sp., and Acanthocythereis?
Iliitsumai.
Shallow water mud dwellers: Bicornucythere
bisanensis, Neomonoceratina microreticulate andSpinileberis quadriaculeata.
A species group of Anchistrocheles is newly
described. Similar species were reported fromsubtropical, relatively deep water of the IndoPacific Oceans (Maddocks, 1969). Translucent,fragile carapaces of Paradoxostoma and Cytherois
occur abundantly in an excelent state of preservation.
At loco 11, samples were taken at verticalintervals of 50 cm to detect any vertical change
in species composition. The following verticalchanges were observed: In the Mya Bed, Pistocythereis bradyformis, Bicornucythere bisanellsis,
and Neomonoceratina microreticulate dominate;
Pis tocy th ere is bradyformis and Bythocythere
ishizakii dominate in the lower part of the Tonna
Bed; Pistocythereis bradyfom1is and Loxoconcha
optima dominate the middle part; and Pontocythere subjaponica, P. miurensis, and P. japonica dominate the upper part. The vertical change
in species composition results from a gradual increase of off-shore species in the assemblage.
A comparison of ostracod assemblage of the
Takamatsu Shell Sand with those of F and G
Members of the Kioroshi Fonnation, 80so Peninsula (Yajima, 1978), allows us to make the following two preliminary deductions concerning
environments of ostracods living at the time ofdeposition of each bed.
1. The Dosinia Bed of the Takamatsu Shell
Sand and F Member of the Kioroshi Formation
both contain Bicornucythere bisanensis. However, the difference of associated species, Neomonoceratina microreticulate in the Takamatsu
Shell Sand and Spinileberis quadriaculeata andCytheromorpha acupunctata in F Member of theKioroshi Formation is indicative of a slight difference of environment. The former is interpreted to be a little closer to the bay mouth thanthe latter (cf. Ikeya and Hanai, 1982).

Table 3.

Ostracoda from the Takamatsu Mya and Tonna Beds I. Species obtained from more than 10 samples are shown. Total number of individuals
and total number of species of this table arc the sum total of Tables 3 and 4.

~rSpecies
Cytherelloidea /Ilunechikai Ishizaki
Neonesidea hallaii, n. sp.
Anchistrocheles yamaguchii, n, sp.
Propontocypris sp.
Neocytherideis aoi Yajima

0501 0601 0602 0701 0702 0801 0802 0901 1001 1002 1003 HOI 1102 1103 1104 1105 H06 1107 llOS ll09 IllO Illl 1201 1202 1203 1301 1401

2
15
4
1

7
2
1

Pontocythere japonico (Hanai)
P. miurensis (Hanai)
P. Sllbjaponica (Hanai)
Munsevella japonica (Hanai)
Callis{ocythere reticulata I-lanai

16
8
12
1
9

6
6
4
1
13

Cythere omotenipponica Hanai
Neomonoceratina microreticulate Kingma
Trachyleberis scabrocuneata (Brady)
T. sp.
. ?..
Acanthocytherels. nlltslimal. (I s h'Iza k')
I,

4
5

3
4
8

19
1

Sinoleberis tosaensis (lshizaki)
Pistocvt hereis brady/ormis (lshizaki)
Biconillc\'there bisanensis (Okubo)
Australiillooselle toma/wae (Ishizaki)
Aurila subconl'exa (Kajiya1l1a)

3
26
5
2
2

1
31
16

4

1

A. uranouchiensis Ishizaki
Robustaurila ishiza/lii (Okubo)
COrllucoquimba tosaensis (Ishizaki)
Caquilllba ishiza/lii Yaji1l1a
Bytlwcythere ishizakii, n. sp.

4

3

6

5
59
2
3
3
4
5
3
1
2

11

4

7

4

4

3

4
11
2

5

7
2
1
4
14

3
2
3

2

1
13

I
9

B. maisakel1sis Ikeya and Hanai
Pseudocythere frydli Yaji1l1a
Hemic\'therura cllneata Hanai
Semicvtherura miurensis (Hanai)
Parac),theridea bosoellsis Yaji1l1a

3

2
1
3
3

1
I
1

Loxoconcha optima Ishizaki
L. uranollchiensis Ishizaki
Nipponocythere bicarillata (Brady)
XestOieberis hanaii Ishizaki
X. setollchiensis Okubo

6
6

1
3

2

5

1
1

:{

Paradoxoslollla eiongatlllll Okubo
Cvtherois zosterae Schornikov
Cytheroma? hanaii Yajima
Paracytherolila sp.

4
6
2
2

1

1
5

total number of individuals
total number of species
weight of sample (in gram)

10
5
5

3
1
3
2
9

5

1

1
8
20

\0
5
7

1
30
12
1
1

4

5

5
8
4
1
7

4
2

5
11
1
2
1

8

5
9 31
15 11
1
1
4

2
21

2

2
12
2
3
1

-1

8

35
8

5
11

19
1
.)
J

3
3

2
23
2
12

3
2
2
10

1
9
7
13

1
2
3

2
19

2

6

2
2

3

2
7

1
:l
I
I
7

1
2
1
3
1

1

.;

I"
.)

6
2

1·1
3
1
5
2

3
3
1

1
2
1

8
6

1

1

5
7
2
H

5

4

2
2

7
6
9
I
8

S

1

2
4

13
6
7
1
6

20
13
I

5

6
11

.,
')

9

2
12
]0
2
8

2
:l
20

1\
2
1
I
16

'J

6

2

I
1
1
3

2
:3
7

8

16
1

5

16

6

'J

1
1

4

2
1

Ii

2

I

1

2

J

2

I

J

7

4

13

10
1

5
2
1
15

J

2

2

239 152 151 191 190 191 177 189 235
49 47 28 42 '10 42 35 12 11
15 80 80 25 10 20 20 20 25

.5
2

9
3
9
2
8

35
32
29
2
8

13
13
13

I
4
2
3

1
2

3
]3
2
6
3
I
3

7

1

3
2

8

1
12

1

1
1

1

3
6
3
4

8
5
5

7

10
10
6

8
5
8
1
11

5

4

6

2
1

2
2
2
19
5

1
4
2
8
5

2
4
1

5
1

11

4
10

1
7
5
13
1

11

4
10

1
37
2

7
3

2
40
6
1
2

1
28
5
3

3

4

2

4

7

2

5

17
6
1

1
16

2
2

8

2
3

2
8

6

17

1
2
9

1
6

12
6
14
2
6

2
2

4
2
2

3
8

21
12
22

5
17
6
3
5

8

1
9
2

2

3
12

4

7
6
1

1
20
1
4
11

2 10

1
2

2
10

17
14
14
1
2

4

1
1

1
1

10
20
1
2

2

:~

'j

2
5

1
3
7

3
2
10

16
5
1
4
3

9

25

4

2

2
20

4
1
6
7

1
9
1

1
11

2
4

1

1
2

7

6
11
11

5
3
5

19
29
13

14
8
20

7
10
6
1

15
16
16

10

11

8

4

7

4

2

4

2
2
2
3
6

1
2

2

1
4
8
3
11

1
2

2
5

4

5

15
3
1
6

27
12

7
2

28
9
1
3

3

3

2
:l
2
1
17

3

1
1
19

1
3
10

2
1
15

2
14

5
I
10

18
2
2
6
4

15

2

5

8

1

1
1
1

1
1

3

5
3

2

4

1

1

18 25 25
4
2
4
1
2
3
5
1
3
4
1

18

13
4
1
5
3

9
4

11
2

9

8
1

6
3

5
:l
1
7
2

2

2

3

2
1
2

8
6

1
1
1

1
4

4
1
3

1

3
I

1

1
1

2
3

4

3
2

4
7
3

1
1
8
1

4
2
2

49
2
3
5
9
6

1
1

11

3
1
3

~

3

4
4

4

2

10

14

5
1·1

8
3
2

3
2
7

10
2
2
7
4

2
3
1
2

2
8
11

22
6
2
2

5

2

2

2

3
1

1

2
1

3

I

1

3

4

'"

~

8

'f
o
3i

A

;;;
::::

g.

3
6

2

3

'"~

l:}

6
5

17
10
1

1

~

(;;.

1
2
25 28
2
3
5
2
8

30
6
2
2
1

1

~

::::>

a

12
1

1

:{

2
4

7
9

8
14
1
1
3

5

:{

5

32

3

10

2
3

1
2
1
2

5
2
17
3
4
4

:{

1

1

2
7

4

5
16
1

1
6
8
6

86 116 251 211 197 249 221 155 155 173 164 156 136 211 234 170 258 163
26 33 35 43 43 45 H 36 36 42 38 34 30 46 42 35 49 35
40 40 40 10 20 20 40 40 80 20 80 80 80
5 20 20 20 10

...,
V>

Michiko YAflMA

58
Table 4.

Ostracoda from the Takamatsu Mya and Tonna Beds 2. Species occurred in fewer than 10 samples arelisted. The list is arranged in three columns from left to right: species name, number of total individuals, and sample number and number of individuals from each sample in parenthes.
Species name

No. oftotal
indiv.'

Sample number and mumber of individuals.
hIn parent eses

Anchistrocheles hondai. n. sp.
Paracypris sp.
Aglaiocypris nipponiea Okubo. 1980

2 0501 (1), 1104(1)6 1105(1),1109(1),1201(2),1301(2)10 0701(1),0702(1),0801(1),1102(2),1105(1),1106(1),1108(1),1401(2)Argilloeeia lunata Frydl. 1982

1301(1)
5 0802(1),1101(2),1108(1),1110(1)4 0701(1),0702(1),1103(1),1104(1)8 0501(2),1103(2),1201(2),1301(2)Pontoeythere minuta Ikeya and Hanai, 1982
Parakrithella pseudadonta (Hanai, 1959)
Eueythere yugao Yajima. 1982
Callistoeythe;'e c!(!'a Hanai, 1957
C. hayamensis Hanai, 1957
C. hotaru Yajima. 1982
C. japonica Hanai, 1957

C. nipponica Hanai. 1957
C. pumila Hanai, 1957
C. rugosa Hanai. 1957
C. subjaponica Hanai, 1957
C. undata Hanai, 1957
C. undulatijaeialis Hanai, 1957
C. sp.
Sehizoeytherc kishinouyei (Kajiyama, 1913)
Hanaiborchella miurensis (Hanai, 1970)
H. triangularis (Hanai, 1970)
Spinileberis quadriaeuleata (Brady, 1880)
Aetinoeythereis kisarazuensis Yajima, 1978
Aurila hataii Ishizaki, 1968
Pseudaurila japoniea (lshizaki, 1968)
Robustaurila assimilis (Kajiyama, 1913)
Ambostracon ikeyai Yajima, 1978
Cornucoquimba rugosa Ikeya and Hanai, 1982
Coquimba poga Hu, 1986
Bythoeythere alata, n. sp.

2 1001(1),1101(1)8 1101(2),1102(3),1104(3)1104(1)
4 0701(1),1001(2),1111(1)2 1105 (1),1201 (1)2 1102(1),1108(1)2 0601(2)1 1202 (1)3 1104 (1),1107 (2)2 1104 (1),1401 (1)4 1104(1),1108(1),1110(1),1201(1)8 0501(1),0801(1),0802(1),1101(1),1105(2),1202(1),1203(1)
5 OG01 (1),0901 (1),1001 (1),1003(1),1301 (1)7 0801(1),0901(1),1002(1),1104(1),1108(1),1109(1),1202(1)
7 0501(1),0901(1),1002(1),1103(1),1108(1),1111(1),1301 (1)0802 (1)12 0601(1),1001(1),1002(1),1103(3),1107(1),1201(2),1203 (3)3 0501(1),1102(1),1106(1)17 0601(1),0702(1),0801(1),0901(1),1106(2),1107(2),1108(1),11101(3),1202(1),1401(4)1 0701 (1)18 1003(2),1101(1),1102(2),1103(1),1104(4),1105(2),1201(3),1202(1),1301(2)15 0501(1),1101(2),1103(1),1105(1),1202(4),1203(6)8 0501(1),0701(1),0801(1),1102(2),1106(1),1310(2)9 0501(1),0702(1),0802(1),1003(1),1102(1),1103(1),1201 (1),1202(2)B. angulata, n. sp.
6 0801(1),1102(1),1104(1),1105(1),1108(1),1201(1)Pseudoeythere sp. 1
6 0901 (1) , 1103 (1), 1104 (1), 1201 (2), 1203 (1)P. sp. 21301 (1)
Eueytherura utsusemi Yajima, 1982
0601 (1)Hemieytherura triearinata Hanai, 1957
13 0501(5),1201(8)Semieytherura henryhowei Hanai and Ikeya, 1977 8 0501(1),1104(1),1108(1), 1201(L), 1202(1), 1401(2)S. tetragona (Hanai, 1957)
9 0601(1),0701(1),0901(2),1001(1),1101(1),1103(1),1107 (1), 1301 (1)Bythoeeratina hanaii Ishizaki, 1968

830. Pleistocene Ostracoda from A tsumi
Table 4.
S. wakamurasaki Yajima, 1982
S. sp.

S. sp. 2
Cytheropteron miurense Hanai, 1957

C. uchioi Hanai, 1957
Paracytheridea sp.
Loxoconcha japonica Ishizaki, 1968
L. kattoi Ishizaki, 1986

Continued
10 0801 (1),0901 (1),1001 (1),1104 (2),1107 (1),1202 (4)9 0501 (3),0602 (1),0702 (1),1107 (1),1108 (1),1202 (1),1301 (1)2 0901 (2)3 1101(1),1201(1),1203(1)1
3
1
2

L. tosaensis Ishizaki, 1968

L. viva Ishizaki, 1968
Loxocorniculum mutsuense Ishizaki, 1971
Cy theromorpha acupunctata (Brady, 1880)
Miia uranouchiensis Ishizaki, 1968
Xestoleberis sagamiensis Kajiyama, 1913

0802 (1)0901(1),1110(1),1201(1)1001 (1)1108(1),1301(1)0701(1)1105 (1)0603(1),0801(1),1103(2),1106(1),1107(1),1109(1),1201(1),1202(1),1301(2)1 1002(1)19 0801 (4), 0802 (1), 1001 (4), 1103 (1), 1105(3), 1106 (2),1107(1),1201(1),1301(2)6 0501(1),1001(1),1105(1),1111(1),1203(2)11

P. sp.

1102 (1)
4 0501(1),0602(1),1105(1),1401(1)1 1109 (1)Cytherois nakanoumiensis Ishizaki, 1969
Paracytherois tosaensis Ishizaki, 1968

2 1001(2)3 0901(2), 1202(1)Sclerochilus mukaishimensis Okubo, 1977

2 1107(1),1203(1)S. sp.

11090)
4 0501(1),0701(1),1104(1),1401(1)Paradoxostoma rhomboideum Okubo, 1977
P. setosum Okubo, 1977

Xiphichilus sp.
Cytheroma ? sp.
Cobanocythere ? pulchra, n. sp.
Hanaicythere nipponica, n. gen. et n. sp.

2. The Tonna Bed and Mya Bed of the Takamatsu Shell Sand and G Member of the Kioroshi
Formation have certain species of Pontocythere,
Loxoconcha and Aurila in common. However,among the associated species, Pistocythereis
bradyfomlis and Bythocythere maisakensis dominate the Takamatsu Shell Sand, whereas Hemicytherura tricarinata and Callistocythere alata
dominate G Member of the Kioroshi Formation.
In addition to this difference of associatedspecies, the occurrence of a relatively deep-water
species of Cytherelloidea munechikai and IndoPacific tropical water species of Anchistrocheles
suggests that the assemblage in the Takamatsu
Shell Sand inhabited deeper and warmer waters
than that of G Member.

59

4 0501(3),1102(1)8 0501(3),0901(2),1102(1),1108(1),1301(1)11 0501(1),0601(1),0701(1),1108(1),1201(3),1401(4)Systematic paleontology
New species, species in open nomenclature,and some species with remarks if necessary, aredescribed. In the case of species in open nomenc1ature, only remarks are given and description isomitted because of the lack of sufficient numberof specimens to describe.
All the types and illustrated specimens are deposited in the collection of the University Museum, University of Tokyo (UMUT). Specimen
numbers are prefixed with CA which stands for
the Cenozoic Arthoropoda.
The following abbreviations are used in thesystematic section:
Sp: specimens measured (LV, RV, C, A-I -Michiko Y ADMA60

A-5, for left valve, right valve, carapace,instar of adult minus one stage - minus
five stage)
Sa: sample number
Me: measurements (L, H, W, for length, height,
width)
N:
number of observations
X: arithmetic mean (mm)Sd: standard deviation (mm)V:coefficient of variability
OR: observed range (mm)Hinge lophodont. Muscle scars consisting of threehorizontal rows of eight zigzag scars. The posterior scar of the upper row, long and overhung on
anterior one. Two very small scars being anterior
to central muscle scars.
Normal pores numerous and simple. Radialpore canals some, simple and short along posterior margin. No eye tubercles on outer surface.
Dimensions:-Measurements of some pooled
specimens of the Takamatsu Tonna Bed are as
follows.

Subclass OSTRACODA Latreille, 1806
Order PODOCOPIDA Sars, 1866
Superfamily BAIRDIACEA Sars, 1888

Sp
LV

N

Sa
0601

Genus Neonesidea Maddocks, 1969

L

0.850
0.466
0.857
0.430
0.784
0.415
0.555
0.321
0.707
0.398
0.538-0.550
0.278-0.294
0.364-0.369
0.200-0.205

L

RV

H

RV(A-l)L
H

L

LV(A-2)

Neonesidea hanaii, n. sp.
Figures 5-1-2, ll-la, b, 2a, b.

OR

H

Family Bairdiidae Sars, 1888
Subfamily Bairdiinae Sars, 1888

MeH

LV(A-l)

L

0501

H

Types:-Holotype, a left valve, UMUT-CA
17979 (Figures II-la, b; Figures 5-1; L 0.745, H
0.413), from sample 1103, Takamatsu Tonna
Bed. Illustrated specimens, a right valve, UMUTCA 17980 (Figures 11-2a, b; Figure 5-2; L 0.707,
H 0.371) from sample 0802, Takamatsu Mya
Bed.
Diagnosis:-Neonesidea with slender outline
and muscle scars consisting of upper two, middle
four, and lower two scars. Posterior scar in upper
row long.
Description:-A trapezoidal carapace withbroadly rounded anteroventral margin in left
valve, and obliquely rounded with narrow dentate frill in right valve. Posterior margin moreacutely projected than anterior margin. Dorsal
margin generally rounded in left valve, and convexed in right valve. Ventral margin a little sinuated at middle in left valve and at anterior thirdin right valve. Left valve overlapping right valve.
Surface smooth.
Marginal infold broad along anteroventral andposteroventral margins. Vestibule broad along
anteroventral and posteroventral margins also.

RV(A-2)2

L
H

LV(A-3)

2

L
H

Remarks:-As to the genus Neonesidea, only
two species, N. oligodentata (Kajiyama, 1913)
and N. mutsuensis (Ishizaki, 1971) have hitherto
been reported although there are many different
forms of Neonesidea in Recent and fossil sediments in Japan. One species in open nomenclature, Bairdia sp. was reported from the Setonaikai (Recent) by Okubo (1975). N. hanaii, n. sp.
is similar to Bairdia sp. in lateral outline and carapace size, but B. sp. was described so briefly that
I could not identify N. hanaii with B. sp.
Occurrence:-Common in the TakamatsuMya
and Tonna Beds.
Subfamily Bythocypridinae Maddocks, 1969
Genus Anchistrocheles Brady and Norman, 1889
Anchistrocheles hondai, n. sp.
Figures 5-6, 11-5a, b.

61830. Pleistocene Ostracoda from Atsumi
Types:-Holotype, a right valve, UMUT-CA
17981 (Figures 5-6; Figures 11-5a, b; L 0.652,
H 0.350), from sample 0501, Takamatsu Tonna
Bed.
Diagnosis :-Anchistrocheles with three spines
along anterior margin and seven small spines
along posterior margin. Surface generally pittedwith large punctations.
Description:-Carapace small, flat and trapezoidal. Anterodorsal margin broadly rounded.
Anteroventral angle narrow with three spines.
Posterodorsal margin truncated. Posteroventral
margin broadly and obliquely rounded withseven small spines. Dorsal margin straight and alittle bent toward anterior. Ventral margin deeply sinuated at anterior third, but generally parallel to dorsal margin. Surface pitted with manylarge punctations.
Anterior inner margin running obliquely toward ventral inner margin. Vestibule broad anteroventrally and narrow posteroventrally. Lineof concrescence parallel to anterior and posteroventral outer margins. Hingement lophodont.
Muscle scars consisting of three rows of fourlarge ones. Anterior one of four muscle scars
longitudinal and posterior one vertical.
------_._--.. .

..
~.
•c::::f::?
. '•... ~~:'.E8..

,-'·-0"•.,0 \s:::, •c::;. - .~\•...•.....

.-

"

aD ..

Ii: ...

,'"

5
Figure 5. Internal views. Left row (odd number): left valves; right row (even number): rightvalves. x84. 1.2. Neonesidea hanaii, n. sp. I, holotype, CA 17979, sample 1103, Takamatsu Tonna Bed.
2, CA 17980, sample 0802, Takamatsu Mya Bed. 3, 4. Anchistrocheles yamaguchii. n. sp. 3, holotype,
CA 17982.4, CA 17983, sample 0602, Takamatsu Mya Bed. 5. Bythocythere angulata, n. sp., holotype,
CA 17996, sample 1105, Takamatsu Tonna Bed. 6. Anchistrocheles hondai, n. sp., holotype, CA 17981,
sample 0501, Takamatsu Tonna Bed.

Michiko YAllMA

62

Radial pore canals a few and straight. Normal
pores simple. No eye tubercles.
Dimensions:-See Types and Occurrences.
Remarks :-This species is similar to Anchistrocheles antemacella Maddocks, 1969 from New
Zealand in lateral outline and muscle scar pattern, but differs largely in armorment along theanteroventral and posteroventral margins. The
marginal infold of A. hondai is narrower thanthat of A. antemacella. A. hondai is similar to
Bairdia sp. aff. angulata Brady, 1870 from Australia reported by McKenzie (1974) in lateraloutline and surface ornamentation, but A. hondai
is flatter than B. sp. aff. angulata.
Occurrence:- There are only two specimens.
One is the holotype and the other is a juvenile
broken right valve (L 0.434, H 0.229) from sample 114, Takamatsu TOl1na Bed.

tributed. Radial pore canals obscure in most
specimens, but in a few specimens, short, straightand evenly spaced along anteroventral margin.
No eye tubercles.
Dimensiol1s:-Measurements of specimensfrom sample 0602, Takamatsu Mya Bed, aregiven below.
Sp

LV

N Me

2

L
H

RV

X

Sd

0.750
0.373

L
H

L

C

H

LV(A-1)

5

RV(A-1)

6

Anchistrocheles yamaguchii, n. sp.

W
L 0.692
H 0.344
L 0.7110.353
L 0.570
H 0.297
L 0.583
H 0.294
L 0.511
H 0.272
L

H

Figures 5-3, 4, 11-3a, b, 4a, b.

LV(A-2)

4

Types:-Holotype, a left valve, UMUT-CA
17982 (Figures 11-4a, b; Figure 5-3; L 0.743, H
0.376), from sample 0602, Takamatsu Mya Bed.
lllustrated specimens, a broken right valve,
UMUT-CA 17983 (Figures 11-3a, b; Figure 5-4;
L 0.735, H 0.371), from the same sample asholotype.
Diagnosis:-A large Anchistrocheles withsmooth surface. Anterior and posteroventral
vestibules deep. Line of concrescence parallel toanterior and posteroventral margins.
Description:-Carapace large, box-shaped andflat. Anterior margin broadly rounded. Posterior
margin straight and oblique at dorsal third andobliquely rounded at ventral part. Dorsal margin
a little arch-shaped. An terior cardinal angle indistinct. Ventral margin parallel to dorsal marginand sinuated at anterior third. Posterior cardinalangle a little distinct. Surface smooth.
Anterior and posteroventral inner margins
parallel to outer margin. Anterior and posteroventral vestibules broad. Hingemen t lophodontwith crenulated median element in left valve.
Muscle scars consisting of four large scars.
Normal pores simple, many, and evenly dis-

RV(A-2)

3

LV(A-3)

2

RV(A-3)H

LV(A-4)L
H

RV(A-4)LH

LV(A-5)LH

RV(A-5)

L
H

0.011
0.010
0.021
0.009

V

OR

0.743-0.756
0.369-0.376
0.735
0.371
0.760
0.367
0.217
0.681-0.712
0.338-0.362
0.159 0.681-0.712
0.028 0.338-0.362
0.037 0.550-0.591
0.030 0.290-0.309
0.579-0.587
0.292 -0.297
0.488-0.533
0.266-0.278
0.536
0.266
0.386
0.217
0.362
0.198
0.290
0.169
0.302
0.181

Remarks:-This species is similar to Anchistrocheles brady; Scott, 1905 reported form Nosy Be
by Maddocks, 1969 in lateral outline and muscle
scar pattern but anteroventral and posterior vestibules are not distinct in A. yamaguchii.
Occurrence:-Abundant in sample 0602, Takamatsu Mya Bed. Rare in all Takamatsu Shell Beds.
Superfamily CYPRIDACEA Baird, 1845
Family Paracyprididae Sars, 1923

830. Pleistocene Ostracoda from A tsumi
Genus Paracypris Sars, 1866

Paracypris? sp.

63

them.
Occurrence:- Very rare in Takamatsu Mya
and Tonna Beds.

Figures 6-2, 3.

Illustrated specimens:-A left valve, UMUTCA 17984 (Figure 6-2; L 0.588, H 0.242), fromsample 1203, Takamatsu Mya Bed, and a rightvalve, UMUT-CA 17985 (Figure 6-3; L 0.485, H
0.227), from sample 1109, Takamatsu Tonna
Bed.
Remarks: - This species is similar to Paracypris
sp. described by Yajima (1982, p. 183, 185, pI.
15, fig. 6, text-fig. 13-1) in lateral outline and in
the shape of inner margin, but this species isshort and small with a more arched ventral margin. Five adductor muscle scars are observed.
Two illustrated specimens are different in size,
but marginal infolds are developed in each of

Genus Aglaiocypris Sylvester-Bradley, 1946

Aglaiocypris? nipponica Okubo, 1980
Figure 6-1.

Aglaiocypris nipponica Okubo, 1980, p. 17 -20, pI. I,
figs. e, f, text-fig.!'

Illustrated specimen:-A left valve, UMUT-CA
17986 (Figure 6-1; L 0.555, H 0.227), from sample 1106, Takamatsu Tonlla Bed.
Remarks: -Adductor scars composed of six
small oval scars in a circular arrangement are observed. Two anteroventral scars are located horizontally and two posteroventral scars are vertically.

3

5
Figure 6. Inner views. x93. 1. Aglaiocypris? nipponica Okubo, 1980, a left valve, CA 17986,
sample 1106, Takamatsu TOlllza Bed. 2, 3. Paracypris? sp. 2, a left valve, CA 17984 (sample 1203, Takamatsu Mya Bed). 3, a right valve, CA 17985 (sample 11 09, Takamatsu Tonna Bed). 4,5. Coquimba pogaHu, 1986.4, a left falve, CA 17991. 5, aright valve, CA 17990 (sample 1203, Takamatsu Mya Bed).

Michiko YAJIMA

64

Occwrence:-Rare in Takamatsu Mya andTonna Beds.
Family Pontocyprididae G. W. Muller, 1894
Genus Propontocypris Sylvester-Bradley, 1947

Propontocypris sp.
Propontocypris (Propontocypris) sp., Yajima, 1982, p.
183, pI. 15, figs. 1,2,5.

Remarks:-All individuals are juveniles.
Occurrence:-Common
fromTakamatsu
Dosinia, Mya, and Tonna Beds.
Superfamily CYTHERACEA Baird, 1850
Family Leptocytheridae Hanai, 1957
Genus Callis to cy there Ruggieri, 1953

Callis to cy there sp.
Callistocythere sp., Ikeya and Hanai, 1982, p. 45,46, pI.
5, figs. 7a, b, 8,9;Yajima, 1982,p.I92,pl.ll,figs.
8,9.

Occurrence:- Very rare in Takamatsu Mya
and TOlllla Beds.
Family Trachyleberididae Sylvester-Bradley,
1948

Coquimba sp., Hanai, Ikeya and Ishizaki in Hanai et aI.,
1977, p. 48.
Coquimba ishizakii Yajima, 1978, p. 397, pI. 49, figs.
4a~c, text-figs. 7-3a, b; Frydl, 1982, tables 1,2; Hu,
1982, p. 194, pI. 3, figs. 24, 28, 29; Hu, 1983, p.
152, pI. 1, figs. 21,27, text-figs. 2; Hu, 1984, pI. 2,
fig. 23; Hu, 1986, p. 121, pI. 3, figs. 4,5,7, 8, 10~
12, 15.

Illustrated specimens:-A right male valve,
UMUT-CA 17988 (Figure 12-2; L 0.531, H
0.252), from sample 0702, Takamatsu Mya Bed.
A right female valve, UMUT-CA 17989 (Figure
12-3; L 0.535, H 0.262), sample 1105, Takamatsu Tonna Bed.
Remarks:-Although C. ishizakii was reported
from the Holocene and Pleistocene sediments inJapan and Taiwan, there is no description ofsexual dimorphism. In the Takamatsu Shell Sand,
there are many specimens of C. ishizakii, andsexual dimorphism is observed. Female is shorterand higher than male. The specimens illustrated
by Yajima (I 978) are probably male.
It is worthwhile to describe that some falseradial pore canals are developed along anterior
margin, in considering the evolution of Co quimbinae in Japan.
Occurrence:-Rare in Takamatsu Dosinia Bed
and common in Mya and Tonna Beds.

Genus Trachyleberis Brady, 1898

Coquimba poga Hu, 1986

Trachyleberis sp.

Figures 6-4, 5, 11-8a~c, 9a, b.

Trachyleberis sp., Yajima, 1978, p. 398, 399, pI.49,figs.
la, b; Ikeya and Hanai, 1982, p. 48, pI. 4, figs. 8a, b;
Frydl, 1982, table 1; Yajima, 1982, p. 195, 196.

Illustrated specimens:-A right valve, UMUTCa 17990 (Figures 11-9a, b; Figure 6-5; L 0.604,
H 0.315) and a left valve, UMUT-CA 17991 (Figures 11-8a-c; Figure 6-4; L 0.591, H 0.334)
from sample 1203, Takamatsu Mya Bed.
Remarks:-This species resembles Coquimba
ishizakii Yajima, 1978 in lateral outline, distinct
subcentral tubercle, and posteroventral projection, but differs in its smooth surface and in having a large tubercle on postroventral margin. The
carapace size of this species is larger than that of
Coquimba ishizakii. Japanese specimens are alittle smaller than the specimens from the Tungshiao Formation of Taiwan.
Occurrence:-Rare in Takamatsu Mya andTonna Beds.

Occurrence: -Common in Takamatsu Tonna
Bed. Rare in Takamatsu Mya and Dosinia Beds
and Akazawa Silt Member.
Family Hemicytheridae Puri, 1953
Subfamily Coquimbinae Ohmert, 1968
Genus Coquimba Ohmert, 1968

Coquimba ishizakii Yajima, 1978
Figures 12-2, 3.

"Hermanites" sp. A, Ishizaki, 1968, p. 41, pI. 6, fig. 13.

830. Pleistocene Ostracoda from Atsumi

65

1

2

• 0

• :-.'.

"

o·~ ' .
0:.

3
- -:-. •0..... ,\

\ '. '... '.B.!:f ~
\.

/, \

. ' ~"""'\,p.

Figure 7. Inner views. xl 00. 1, 2. Pseudocythere sp. 1. 1, a left valve, CA 17998 (sample
1103, Takamatsu Tonna Bed). 2, a left valve, CA 17999 (sample 1104, Takamatsu Tonna Bed). 3.
Pseudocythere sp. 2, a left valve, CA 18000 (sample l301, Takamatsu Tonna Bed). 4. Bythocythere alata, n. sp., holotype, a right valve, CA 17992 (sample 1102, Takamatsu Tonna Bed). 5, 6.
Bythocythere ishizakii, n. sp. 5, holotype, a left valve, CA 17994. 6, a right valve, CA 17995(both sample 0501, Takamatsu Tonna Bed).

Family Bythocytheridae Sars, 1926
Subfamily Bythocytherinae Sars, 1926
Genus Bythocythere Sars, 1866

Bythocythere alata, n. sp.
Figures 74,11-10, 12-7a-c.

Types:-Holotype, a right valve, UMUT-CA
17992 (Figures 12-7a-c; Figure 74; L 0.517, H0244), from sample 1102, Takamatsu Tonna
Bed_ Illustrated specimen, a right valve, UMUTCA 17993 (Figure 11-10; L 0.522, H 0.253)
from sample 0701, Takamatsu Tonna Bed.
Diagnosis:-A small Bythocythere with weak
dorsal keel and flattened ventral alae startingfrom anteroventral corner, pOinting posteroven-tral corner, and running toward posterodorsal
caudal process, and with weak ridges along ventral margin.
Description:-Carapace small in lateral view.
Anterior margin broadly rounded. Dorsal margin
straight with weak ridges along its posterior two
thirds. Posterior caudal process distinct at dorsal
third, and flattened. Ventral margin straight andparallel to dorsal margin. Ventral alae startingfrom anteroventral corner, pointing at posteroventral corner, and running toward posterodorsal
caudal process, with weak ridges on the tip andthree longitudinal ridges on dorsal side. Three
weak ridges running along posteroventral ridge_
Anteroventral sulcus weak_ Median sulcus not so
distinct in lateral view.

Michiko YAJIMA

66

Marginal infold broad anteroventrally andposteroventrally. Radial pore canals some, straightat anterior and posterior sides. Normal pores simple. Eye tubercle not so distinct. Hinge straightlophodont. Muscle scars consisting of a roundfrontal scar and a vertical row of five small roundscars on inner wall of median sulcus.
Dimensions:-Measurements of pooled specimens are given below:
Sp

Sa

RV(A-l)

0501

N

Me
L

H
RV

0701

L

H
RV

1102

LV

1106

2

L

H
L

H
LV

1301

L

H

OR

0.447
0.217
0.522
0.253
0.517
0.234-0.244
0.512
0.249
0.527
0.244

Remarks:-This species is similar to By thocythere ishizakii, n. sp. in lateral outline, but isdifferent in the shape of ventrolateral alae.
OccUlTellce:-Rare in Takamatsu TOl1na Bed.
Bythocythere ishizakii, n. sp.
Figures 7-5, 6, 11-11, 12-8a, b, 9a, b.

Types:-Holotype, a left valve, UMUT-CA
17994 (Figure 11-11, Figures 12-9a, b; Figure
7-5; L 0.636, H 0.315), from sample 0501, Takamatsu Tonlla Bed. Illustrated specimens, a rightvalve, UMUT-CA 17995 (Figures 12-8a, b; Figure 7-6; L 0.623, H 0.331), from the same sample as holotype.
Diagnosis:-Bythocythere with punctated surface with weak ridges on ventral side of lateralalae.
Description:-Carapace subrhomboidal in lateral view. Anterior margin broadly rounded, dorsal margin straight. Posterior caudal process
locating above middle of posterior margin, triangular and flat. Posteroventral margin very broadly and obliquely rounded. Ventral margin straightand parallel to dorsal margin.

Surface evenly pitted. Weak ridges runningparallel to posteroventral margin and ventral sideof ventral alae. Anterodorsal ridge distinct andparallel to dorsal margin in left valve. Posterodorsal ridge also distinct and parallel to posteroventral margin. Anterior margin having weak ridges.
Median sulcus not so distinct in lateral view. Anterior half of median sulcus covered with weak
reticulations.
Marginal infold moderate along anteroventral
and posterior margins. Vestibule indistinct. Radial pore canals short, straight, and evenly arranged. Normal pores simple. Hinge straight typeof lophodont. Muscle scars consisting of a vertical row of five adductor scars on inner wall of
median sulcus in arched shape and a round frontal scar. A large scar above adductor scars and asmall round scar below frontal scar observed.
Dimensiolls:-Measurements of specimensfrom sample 0501, Takamatsu TOlllla Bed are
given below.
N Me

Sp

5

RV

L

H

3

LV

L

H
LV(A-l)

2

L

H

X

0.613
0.317
0.627
0.330
0.492
0.257

Sd

OR

V

0.007 0.012
0.011 0.036

0.603-0.623
0.302-0.331
0.616-0.633
0.330
0.488-0.495
0.256-0.258

Remarks:-Bythocythere ishizakii is similar to
B. maisakellsis Ikeya and Hanai, 1982 in lateraloutline and carapace surface, but median sulcusof B. ishizakii is not so deep as B. maisakensis.
The surface of B. ishizakii is smooth and has no
distinct ridges. B. ishizakii is larger than B. maisakensis. B. ishikaii is similar to Bythocythere sp.
A Ishizaki, 1968 in lateral surface, but mediansulcus is not so well developed.
Occurrellce:-Rare in Takamatsu Dosinia Bed
and common in Takamatsu Mya Bed and Tonna
Bed.
Genus Bythoceratina Hornibrook, 1952

Bythoceratina angulata, n. sp.
Figures 5-5, 11-6a, b, 7a-c.

830. Pleistocene Ostracoda from Atsumi
Bythoceratina sp., Yajima, 1982, p. 216, pI. 13, fig. 16.

Types:-Holotype, a left valve, UMUT-CA
17996 (Figure 11-7a-c; Figure 5-5; L 0.712, H
0.340), from sample 1105, Takamatsu Tonna
Bed. Illustrated specimens, a right valve, UMUTCA 17997 (Figures 11-6a, b; L 0.681, H 0.387),
from sample 0801, Takamatsu Tonna Bed.
Diagnosis:-Bythoceratina with distinct lateralalae and anterodorsal lobe. A lateral alae startingfrom anteroventral area, running posteroventrallywith distinct keel, and then turning to posterodorsal area with reticulation. Anterodorsal lobe
with reticulation at anterodorsal slope.
Description:-In lateral view, anterior margin
broadly and obliquely rounded. Dorsal margin
straight with distinct dorsal ridge starting at anterior third, running a little dorsalward andsquarely shouldering. Ventral margin obs~uredby lateral alae, but nearly parallel to dorsal margin. Posterior caudal process distinct at dorsal
part with weak reticulation. Anterior lobe, withreticulation at anterodorsal slope. Median sulcus
distinct. Lateral alae starting at mid-height toanteroventral area, running posteroventrally with
distinct keel, and then turning posterodorsal
direction, forming angular tip of wing, and ending at posterior caudal process with reticulation.
Surface evenly punctated.
Marginal infold broad along anterior and posterior margins. Vestibule deep along anterior andposterior margins. Radial pore canals, several,
short, and straight. Normal pores simple. Hinge
straight type of lophodont. Muscle scars consisting of a frontal scar and a vertical row of five adductor scars on the inner wall of median sulcus.
Dimensions:-Measurements of pooled specimens are given below.
Sp
RV

Sa
0801

N

Me

OR

L

0.681
0.387
0.647
0.319
0.712
0.340

H

RV

1102

L
H

LV (holotype)

1l0S

L
H

67

Remarks:-In 1982, I discussed this species toresemble Bythoceratina sp. (originally Monoceratina sp. A, Key [Keij], 1953) in lateral outline and surface ornamentation. But in By thoceratina sp., two straight ridges run obliquely inanterodorsal area and the anterior marginal ridge
is very distinct.
Occurrence:-Rare in Takamatsu Tonna Bed.
GenusPseudocythere Sars, 1865
Pseudocythere sp. 1
Figures 7-1,2.

Illustrated specimens:-A left valve, UMUTCA 17998 (Figure 7-1; L 0.446, H 0.223), fromsample 1103, Takamatsu Tonna Bed, and a left
valve, UMUT-CA 17999 (Figure 7-2; L 0.385, H
0.188), from sample 1104, Takamatsu Tonna
Bed.
Remarks: - This species is similar to Pseudocythere similis Miiller, 1908 described by Schornikov (1982) in lateral outline, but the po.steroventral marginal infold of this species is morestrongly developed.
Occurrence:-Very rare in Takamatsu Tonna
Bed.
Pseudocythere sp. 2
Figure 7-3.

Illustrated specimen:-A left valve, UMUT-CA
18000 (Figure 7-3; L 0.411, H 0.232) from sample 1301, Takamatsu Tonna Bed.
Remarks:-This species is very similar to
Pseudocythere sp. 1 of this paper in lateral outline but has 10 to 12 horizontal ridges. The
species is also similar to Pseudocythere sp. 1 described by Whatley and Downing (I982) from
the Middle Miocene of Victoria, Australia in having the lateral parallel ribs extending from theanterior to posterior margins, but is distinguishedin having no weak vertical ribs in anterior part.
Occurrence:- Very rare in Takamatsu Tonna
Bed.
Family Cytheruridae G. W. Miiller, 1894
Subfamily Cytherurinae G. W. Miiller, 1894

Michiko YAJIMA

68

Genus Semicytherura Wagner, 1957

Semicytherura sp. 1
Figures 12-10, 11.

Illustrated specimens:-A left juvenile valve
UMUT-CA 18001 (Figure 12-11; L 0.368, H
0.146), from sample 0702, Takamatsu Mya Bed,and also a left juvenile valve, UMUT·CA 18002(Figure 12-10; L 0.354, H 0.145), from sample
0602, Takamatsu Mya Bed.
Remarks:-Comparing two specimens, differ·ence of secondary surface ornamentation at thecentral part is noted, one being smooth, and theother punctate.
Occurrence:- Very rare in Takamats Tonna
and Mya Beds.
Semicytherura sp. 2
Figure 12-6.

Illustrated specimen:-A left valve, UMUT·CA
18003 (Figure 12-6; L 0.333, H 0.164) fromsample 0901, Takamatsu Tonna Bed.
Remarks:- This species is similar to Semicytherura miurensis (Hanai, 1957) in lateral outline
but smaller size and a median horizontal ridge
characterize the Atsumi specimens.
Occurrence:- Very rare in Takamatsu TOllna
Bed.

those specimens from the Atsumi area are all ofjuvenile form.
Occurrence:-Very rare in Takamatsu Tonna
Bed.
Family Paradoxostomatidae
Brady and Norman, 1889
Subfamily Paradoxostomatinae
Brady and Norman, 1889

GenusParadoxostoma Fisher, 1855
Paradoxostoma setosum Okubo, 1977
Figure 9-2.
Paradoxostoma setosum Okubo, 1977, p. 127-129,
figs. 4f-h, 19a-h.

Illustrated specimen:-A right valve, UMUTCA 18005 (Figure 9-2; L 0.500, H 0.277), sample 1105, Takamatsu Tonna Bed.
Remarks:-The illustrated specimen is very
similar to the Recent specimen described by
Okubo (1977) from the Setonaikai, except for
the height of carapace. This specimen is a little
higher.
Occurrence:- Very rare in Takamatsu Mya
and Tonna Beds.
Paradoxostoma sp.
Figure 8-1.

Family Paracytherideidae Puri, 1957

GenusParacytheridea G. W. MUller, 1894
Paracytheridea sp.
Figures 12-12a, b.

Illustrated specimens:-A juvenile left valve,
UMUT CA 18004 (Figures 12-12a, b; L 0.552, H
0.252), from sample 1110, Takamatsu TOllna
Bed.
Remarks:- The ventral alae of this species arevery protrudent with tubercle at posteroventral
side of caudal projection. This species closely resembles Paracytheridea polyspinosa Hu andCheng, 1977 described by Hu (1986, pI. 16, figs.
9, 10) in outline and surface ornamentation, but
species identification is waived simply because

Paradoxostoma sp. 2, Frydl, 1982, p. 136, text-fig. 32c.

Illustrated specimen:-A left valve, UMUT-CA
18006 (Figure 8-1; L 0.819, H 0.277), sample
1109, Takamatsu Tonna Bed.
Remarks:- The illustrated specimen has more
numerous radial pore canals along the posterior
and ventral margins than the specimen illustrated
by Frydl (1982).
Occurrence:-Only one illustrated specimen.
Genus Sclerochilus Sars, 1866

Sclerochilus sp.
Figure 9-1.
Sclerochilus sp. I, Yajima, 1982, p. 226, pI. 15, fig. 10,

830. Pleistocene Ostracoda from Atsumi

Figure 8. Inner views. x75. 1. Paradoxostoma sp., a left valve, CA 18008 (sample 1109,
Takamatsu Tonna Bed). 2. Xiphichilus sp., aleft valve, CA 18008 (sample 0701, Takamatsu
Tonna Bed).
text-fig. 17-5.

69(1982) has four adductor scars. The triangularlateral outline and straight ventral margin of thisspecimen may represent a new genus.
Recently, Schornikov (1982) proposed a new
genus Convexochilus to include triangular Sclerachilus species, assigning the Antarctic species
Sclerochilus meridionalis G. W. Milller, 1908 as
the type species. The present species is very similar to Sclerochilus meridionalis in general shape,and may be included into the genus Convexochilus. However, this species is small in size anddifferent slightly in its muscle scar patterns.
Convexochilus is so far known only from around
Antarctic sea.
Occurrence:-Very rare in Takamatsu Tonna
Bed.
Genus Xiphichilus Brady, 1870

Illustrated specimen:-A right valve, UMUTCA 18007 (Figure 9-1; L 0.431, H 0.254), sample 1109, Takamatsu Tonna Bed.
Remarks:-One available specimen has fivelarge adductor scars attached to one another toform a circle, and inclined towards posterior,although Sclerochilus sp. 1 reported by Yajima~.

1

Xiphichilus sp.
Figure 8-2.

Illustrated specimen:-A left valve, UMUT-CA
18008 (Figure 8-2; L 0.946, H 0.281), from sample 0701, Takamatsu Tonna Bed.
Remarks:- This is the first report of Xiphichilus from Japan. This species is rather short inlength among the genus Xiphichilus.
Occurrence:-Very rare in Takamatsu Tonna
Bed.
Family Cytheromatidae Elofson, 1939
Subfamily Cytheromatinae Elofson, 1939
Genus Cytheroma G. W. MUller, 1894

Cytheroma? sp.
Cytheroma? sp., Ikeya and Hanai, 1982, p. 58,59, pI. 6,
fig. 1-4, text-fig. 20.

Occurrence:-Very rare in Takamatsu Dosinia
and Tonna Beds.
GenusParacytheroma Juday, 1907
Figure 9. Innver views. xl 00. 1. Sclerochilus sp., a right valve, CA 18007 (sample
1109, Takamatsu Tonna Bed). 2.Paradoxostoma
setosum Okubo, 1977, a right valve, CA 18005(sample 1105, Takamatsu Tonna Bed).

Paracytheroma sp.
Paracytheroma sp., Yajima, 1982, p. 226,227, pI. 15,
figs. 3,4,7,8,13, text-figs. 17-3,4.

Michiko YAJIMA

70

Occurrence:-Rare in Takamatsu Dosinia andTonna Beds.
Family Microcytheridae Klie, 1938
Genus Cobanocythere Hartmann, 1959

Cobanocythere? pulchra, n. sp.

~.'

..

~
}/ I )'---_J

1

Figures 10-2, 3, 12-Sa-c.

Types:-Holotype, a left valve, UMUT-CA
18009 (Figures 12-5a-c; Figure 10-3; L 0.479, H
0.201), from sample 0501, Takamatsu Tonna
Bed. Illustrated specimen, a right valve, UMUTCA 18010 (Figure 10-2; L 0.458, H 0.154), fromsample 1112, Takamatsu Dosinia Bed.
Diagnosis:-Cobanocythere with a shallow
hollow at anteromedian part of ventrolateralalae.
Description:-Carapace small, trapezoidal inlateral outline. Dorsal hinge margin straight. Anterior margin narrowly rounded at ventral part.
Anterior and posterior cardinal angles distinct.
Posterior margin narrowly and obliquely rounded
like anterior margin. Ventral margin sinuated at
posterior third. Ventrolateral margin prominently projected out laterally. Ventral flat broad. Surface smooth with some scattered punctations.

Figure 10. Inner views. xl 00. 1. Hal1ai·
cythere l1ippol1ica n. gen. et n. sp., holotype, aleft valve, CA 18001 (sample 118, Takamatsu
TOl1l1a Bed). 2, 3. Cobal1ocythere? pu1chr4, n.
sp. 2, a left valve, CA 18010 (sample 1112,
Takamatsu Dosil1ia Bed). 3, holotype, a rightvalve, CA 18009 (sample OS 1, Takamatsu
TOlllla Bed).

~ Figure 11. la, b, 2a, b. Neollesidea hal/a ii, n. sp.
la. Lateral view of left valve (holotype, CA 17979, sample 1103, Takamatsu TOl/lla Bed). x60. lb. Inner view ofright valve (CA 17979). x60. 2a. Lateral view of right valve (CA 17980, sample 0802, Takamatsu Mya Bed). x60.
2b. Inner view of right valve (CA 17980). x60.
3a, b, 4a, b. A I1chistrocheles yamaguchii, n. sp.
3a. Lateral view of right valve (CA 17983, sample 0602, Takamatsu Mya Bed). x6S. 3b. Inner view of right valve(CA 17983). x6S. 4a. Lateral view of left valve (holotype, CA 17982, sample 0602, Takamatsu Mya Bed). x6S.
4b. Inner view of left valve (CA 17982). x6S.
Sa, b. Allchistrocheles hOlldai, n. sp.
Sa. Lateral view of right valve (holotype, CA 17981, sample OSOI, Takamatsu TOlll1a Bed). x70. Sb. Inner viewof right falve (CA 17981). x70.
6a, b, 7a-e. Bythocythere allglllata, n. sp.
6a, b. Stereo pair of lateral view of right valve (CA 17997, sample 0801, Takamatsu TOllna Bed). x6S. 7a, b.
Stereo pair of lateral view of left valve (holotype, CA 17996, sample 110S, Takamatsu TOlllla Bed). x6S. 7e.
Inner view of left valve (eA 17996). x6S.
8a-e, 9a, b. Coqllimba poga Hu, 1986
8a, b. Stereo pair of lateral view of left valve (CA 17991, sample 1203, Takamatsu TOllna Bed). x78. 8e, Inner
view of left valve (CA 17991). x78. 9a, b. Stereo pair of lateral view of right valve (CA 17990, sample 1203,
Takamatsu TOl1lla Bed). x78.
10. Bythocythere alata, n. sp.
Inner view of right valve (CA 17993, sample 0701, Takamatsu TOl1lla Bed). x80.
11. Bythocythere ishizakii, n. sp.
Inner view of left valve (holotype, CA 17994, sample OSOI, Takamatsu TOlll1a Bed). x6S.

830. Pleistocene Ostracoda from A tsumi

71Michiko YAHMA

72

Shallow small depression at anteromedian part ofventral alae.
Marginal infold broad anteriorly and posteriorly. Anterior and posterior inner margins nearlystraight and vertical to ventral margin. Ventral
inner margin running parallel to outer margin.
Vestibule not distinct. Anterior radial pore canals
short, two pseudoradial canals, and five fingerlike ventral canals. Posterior radial pore canals
several, short, straight and finger type at ventral
part. Normal pores simple. Eye tubercles obscured.
Muscle scars consisting of two frontal scars
and a row of four adductor scars. Hinge lophodont with distinct short bar as median element inright valve.
Dimensions:-Measurements of pooled specimens are given below.
Sp
RV

Sa

N

0501

2

Me

OR

L

0.469-0.472
0.162-0.201
0.362
0.133
0.362
0.145
0.446
0.162

H

RV(A-l)0901

L
H

RV(A-1)

1102

L
H

RV

1108

L
H

LV

1301

L
H

LV

1112

L
H

0.460
0.154
0.458
0.154

Remarks:- This species resembles Cobanocythere? japonica Schornikov, 1975 in lateraloutline, marginal infold and radial pore canals,
but Cobanocythere? japonica has three adductor
scars and transversal elevation in inner view.
Occurrence:-Very rare in Takamatsu Dosinia
and Tonna Beds.
Genus Hanaicythere, n. gen.

Type species:-Hanaicythere nipponica, n. sp.
Diagnosis:-Small trapezoidal carapace with
distinct frill-like ventrolateral alae. Ventrolateralalae, ventrally flattened, starting from anteroventral corner, running parallel to dorsal marginand ending at posteroventral corner. Surface
smooth. A shallow median sulcus on lateral sideof ventrolateral alae.
Anteroventral, posteroventral and ventral marginal infold broad. Normal pore canals simple.
Radial pore canals a few and straight. Eye tubercles obscured. Hinge lophodont with distinct bar
as median element. Muscle scars consisting of a

~ Figure 12. la, b, 4a, b. Hanaicythere nipponica, n. gen. et n. sp.
la, b. Stereo pair of lateral view of left valve (CA 18012, sample 1201, Takamatsu Tonna Bed). xIOO. 4a, b.
Stereo pair of dorsal view of right valve (holotype, CA 18011, smple 1108, Takamatsu Tonna Bed). xl 00.
2,3. Coquimba ishizakii Yajima, 1978
2. Lateral view of right male valve (CA 17988, sample 0702, Takamatsu Mya Bed). x78. 3. Lateral view of rightfemale valve (CA 17989, sample 1105, Takamatsu Tonna Bed). x78.
Sa-c. Cobanocythere? pulchra, n. sp.
Sa, b. Stereo pair of lateral view of right valve (holotype, CA 18009, sample 0501, Takamatsu Tonna Bed). x78.
5c. Inner view of right valve (CA 18009). x100.
6. Semicytherura sp. 2
Lateral view of left valve (CA 18003, sample 0901, Takamatsu Tonna Bed). x 140.
7a-c. Bythocythere alata, n. sp.
7a, b. Stereo pair of lateral view of right valve (holotype, CA 17992, sample 1102, Takamatsu Tonna Bed). x83.
7c. Inner view of right valve (CA 17992). x83.
8a, b, 9a, b. Bythocythere ishizakii, n. sp.
8a, b. Stereo pair of lateral view of right valve (CA 17995, sample 0501, Takamatsu Tonna Bed). x68. 9a, b.
Stereo pair of lateral view of left valve (holotype, CA 17994, sample 0501, Takamatsu Tonna Bed). x68.
10,11. Semicytherura sp. 1
10. Lateral view of left juvenile valve (CA 18002, sample 0602, Takamatsu Mya Bed). x140. 11. Lateral view ofleft juvenile valve (CA 18001, sample 0702, Takamatsu Mya Bed). x140.
12a, b. Paracytheridea sp.
Stereo pair of lateral view of left juvenile valve (CA 18004, sample 1110, Takamatsu Tonna Bed). x83.

830. Pleistocene Ostracoda from Atsumi

73

Michiko Y AlIMA

74

frontal scar and four adductor scars.
Remarks:-This genus resembles Cobanocythere Hartmann, 1959 in lateral outline and innerview, but the ventral alae of this genus are very
distinct and are shaped like a" frill.

Hanaicythere nipponica, n. sp.

Sp

Sa

RV

0601

LV

0701

LV (holotype)

1108

LV

1201

RV

1401

N

Figures 10-1, 12-1a, b, 4a, b.

Types:-Holotype, a right valve, UMUT-CA
18011 (Figures 124a, b; Figure 10-1; L 0.473, H
0.131), from sample 118, Takamatsu Tonna Bed.
Illustrated specimens, a left valve, UMUT-CA
18012 (Figure 12-1a, b; L 0.483, H 0.145, W
0.193), from sample 1201, Takamatsu Tonna
Bed.
Diagnosis:-See diagnosis of the genus Hanaicythere.
Description:-Carapace small, fragile, andtranslucent. In dorsal view, carapace egg-shaped
because of broadly rounded ventrolateral alae.
Body cavity narrow. In lateral view, carapace
trapezoidal. Anterior margin straight and oblique
at dorsal part, and obliquely and narrowly rounded at ventral part. Dorsal margin straight. Ventral
contact margin obscured by ventrolateral alae.
Margin of ventrolateral alae projected laterallywith two layers of prominent frills. A shallow
hollow on the middle part of ventrolateral alae
having two weak longitudinal ridges.
Ventral marginal infold broad. Anterior andposterior inner margins running vertically down
to ventral margin. Anteroventral list folding innerward before contacting to anteroventral corner. Marginal infold broad anterirorly and posteriorly. Radial pore canals several, short, andstraight dorsally, but like finger-like ventrally.
Opening of radial pore canals setting on each projection of ventrolateral frill. Normal pores simple.
For hinge and muscle scars see diagnosis of
the genus.
Dimensions:-Measurements of pooled specimens are given below.

LV

OR

L
H
L
H
W

0.465
0.133
0.367
0.145
0.169
0.473
0.13.1
0.483
0.145

L
H
L
H
W
L
H
W
L
H
W
L
H

RV (broken)

W
L
H
W

LV (A-I)

LV

Me

1402

L
H
W

0.193
0.471
0.145
0.193
0.410
0.121
0.193
0.410
0.109
0.181
0.302
0.097
0.145
0.507
0.121
0.193

Remarks:- This species resembles Platymicrocythere tokiokai Schornikov, 1975 in anterior
inner view but differs in ventrolateral alae.
Occurrence:-Very rare in Takamatsu Dosinia
and Tonna Beds.
References cited
Frydl, P. (1982): Holocene ostracods in the southern
Boso Peninsula. In T. Hanai ed. Studies on Japanese Ostracoda. Univ. Mus., Univ. Tokyo, Bull.,(20): 61-140.
Hanai, T. (1957): Studies on the Ostracoda from Japan,
III. Subfamilies Cytherurinae G. W. MUller (emend.
G. O. Sars, 1952) and Cytheropterinae n. subfam.
J. Fac. Sci., Univ. Tokyo, Sec. 2, 11 (1): 11-36.
-(1961): Studies on the Ostracoda from Japan:
Hingement.Ibid., 13 (2): 345-377.
- - , Ikeya, N., Ishizaki, K., Sekiguchi, Y. and Yajima,
M. (1977): Checklist of Ostracoda from Japan andits adjacent seas. Univ. Mus., Univ. Tokyo, Bull.,(12): 1-118.
Hartmann, G. (1959): Zur Kenntnis der lotischen

830. Pleistocene Ostracoda from Atsumi
Lebensbereiche der pazifischen Kiiste von El
Salvador unter besondere Beriicksichtigung seiner
Ostracoden fauna. (III. Beitrag zur Fauna EISalvador). Kieller Meeresforsch., 15 (2): 187-24l.
Hayasaka, S. (1960): Large-sized oysters from the Japanese Pleistocene and their paleontological implications. Tohoku Univ., Sci. Rept., 2nd Ser. Spec.
Vol., (4): 356-370.
- - (1961): The geology and paleontology of thc Atsumi Peninsula, Aichi Prefccture, Japan. Ibid., 33(1): 1-103.
--(1962): Summary of the geology and paleontologyof the Atsumi Peninsula, Aichi Prefecture. Ibid.,
Spec. Vol., (5): 195-217.
Honda, H. (1975 MS): The molluscan fossil assemblages
in the Atsumi Peninsula, Aichi Prefecture, central
Japan. Grad. Thesis of the University of Tokyo, 32p.
Hu, Chung-Hung (1982): Studies on ostracod faunas
from the Hengchun Limestone (Pleistocene),
Hengchung area, southern Taiwan. Quat. J. Taiwan
Museum, (35): 171-195.
- - (1983): Ostracods from the Maanshan Mudstone,
Hengchun Peninsula, southern Taiwan. Petro Geol.
Taiwan, (19): 149-178.
--(1984): New fossil ostracod faunas from Hengchun
Peninsula, southern Taiwan. Taiwan Mus. Quat. J.,
31 (1): 65-130.
- - (1986): The ostracods from the Tungshiao Formation (pleistocene), west coast of Miaoli district,Taiwan . .!. Taiwan Mus., 39 (I): 99-174.
Ikeya, N. and Hanai, T. (1982): Ecology of Recent
ostracods in the Hamana-ko region, the Pacificcoast of Japan. In T. Hanai ed. Studies on Japanese Ostracoda. Univ. Mus., Univ. Tokyo, Bull.,(20),15-59.
Ishizaki, K. (1968): Ostracodes from Uranouchi Bay,
Kochi Prefecture, Japan. Tohoku Univ., Sci. Rept.,
2nd Ser., 40 (1): 1-45.
--(1971): Ostracodes from Aomori Bay, Aomori
Prefecture, northeast Honshu, Japan. Ibid., 43 (I):59-97.
Kajiyama, E. (1913): The Ostracoda of Misaki, Part 3.
Zool. Mag (Dobutsugaku-zasshi) , 25: 1-16 (inJapanese).
Key [Keij 1, A. J. (1953): Preliminary note on the Recent Ostracoda of the Snellius Expedition. Proc. K.
Ned. Akad. Wet., Ser. B, 56 (2): 155-168.
Kuroda, K. (1966): Plant remains from the lower andmiddle parts of the Pleistocene A tsumi Group in
the Atsumi Peninsula, central Japan. Quat. Res.,75

5 (2): 49-58.
--(1967): Plant remains from the upper part of the
Pleistocenc Group in the Atsumi Peninsula, central
Japan. Ibid., 6 (2): 57-62.
Maddocks,. R. F. (1969): Revision of Recent Bairdiidae(Ostracoda). U. S. Natl. Mus. Bull., (295): 1-126.
McKenzie, K. G. (1974): Cenozoic Ostracoda of southcastern A ustralia with the description of Hanaiceratina new genus. Geoscience and Man, 6: 153182.
Oinomikado, T. (1933): The Quaternary deposits of theAtsumi Peninsula. Chikyu, 30 (3): 163-173 (inJapancse).
Okubo, I. (1975): Bairdia oligodentata Kajiyama, 1913
and Bairdia sp., in the Inland Sea, Japan (Ostracoda). Res. Bul/., Okayama Shujitsu Junior Coil.,(5): 93-100.
--(1977): Fourteen species of thc genus ParadoxostOl1ta Fischer, 1855, in the Inland Sea, Japan(Ostracoda). Publ. Seto Mar. Bioi. Lab., 24 (1-3):
99-131.
- - (1980): Three new spccies of the Family Candonidac (Ostracoda) from the Inland Sea of Japan.
Proc. Japan. Soc. Syst. Zool., (18): 17-26.
Schornikov, E. I. (1975): Ostracoda fauna of the intertidal zone in the vicinity of thc Seto Marine Biological Laboratory. Publ. Seto Mar. BioI. Lab.,22 (1-4): 1-30.
- - (1982): Ostracoda Bythocytheridae in antarctic
and subantarctic watcr with rcmarks about ontogcny of tribc Sc1crochilini. In A. I. Kafanov(ed.) Fauna and distribution of Crustacea in Notal
and antarctic water: 4-39 (in Russian).
Tsuchi, R. (1960): Problems of the Quaternary historyof the Atsumi Peninsula and its adjancy in the
Tokai Region. Quat. Res., I (6): 193-211 (Japanese with English abstract).
Whatley, R. and Downing, S. (1983): Middle Miocene
Ostracoda from Victoria, Australia. Rev. Esp.
Micropaleontol., 15 (3): 347-407.
Yajima, M. (1978): Quaternary Ostracoda from Kisarazu near Tokyo. Trans. Proc. Palaeont. Soc.
Japan,N. S., (112): 371-409.
(1982): Latc Pleistocene Ostracoda from "the Boso
Peninsula, central Japan. In T. Hanai ed. Studies
on Japanese Ostracoda. Ulliv. Mus., Univ. Tokyo,
Bull., (20): 141-227.
Yokoyama, M. (1926): Fossil shells from the Atsumi
Peninsula, Mikawa. J. Fac. Sci., Imp. Ulliv. Tokyo,
Sec. 2, 1: 369-375.

Michiko Y AHMA

76

'l'iiF> B *i~~~I;;'ilt~~i!tfl-Jf;!h : B*(/)'I'*iiF>il:l1~~&i;(/)*:qzi$J¥I: is--o -c, ~~Mt.i;<jI*IC
L -C iM tl:', T J." T ffl\(/)$iJ~ ~ It-- I- iiF>~ c, <P ff[\(/) ~ &i;li'JffF>~ I: -a- itL J., V /' A;j-k(/)i'.'.'i~liH'l ~ It-I- I: I;j:, {JIHf (/) ft " ti {t:fi iJ'khll: -a- itL -C 1? I), frJF;!h L ~ iltT J., ,ih;iK~It--l-iiF>~liTiiF>lml:~'i:-~<-a-h.,

ZLJ."

Corbiculajaponica'i:-~iltL, t*~'L~<~G

1r-Jf;!hli!Jl.1:.P;Ji'~i]~m.u:Tt.· Bicornucythere bisanensis'i:- ~iltL,/-<-f:tliil:Tt- Aurila subconvexa iJ'i L I).:.,c -r""J." jj\;iJ~~It--I-l}F>1l'l(/)l:.iill(i 20 m (/):tl!;;[k~It--1- - fli±-C",
Uosinia angulosa C Raeta pulchella iJ'Ym~:iJ'G §'f:.(/)ilt;[k'i:-~L, 1r-Jf;!hli Bicornucythe re b isan e nS is (/) h. iJ' y:ltl:ilt tI:lT J." $i)-( ~ It-- I- iiF>Ji!l (/):lltfi'l ail (/)!.l'UQli, fjjJ,pJj-iJ' G(/) i1~ A 'i:- -a-V [1;] i~iJt.l1!:iJ' G,

il~A(/) j..''d:' ''P25E Lt.: [1;]~i~11!: i: -Ij.' --0 t.:':' c 'i:-~T,

i;b I) 'i:-~!1I;li'JiiF>Jl!!(/)li'J-r-I~U ht.:+~ 'd: v/' A;[k(/) < IJ:
iT Dosinia angulosa (/)El1:.TJ.,i~, *.1: Mya arenaria 'i:-3::f*I:TJ.,~ < (/) ~ (/)i~A 'i:- {, t.: G L t.: Jl!!, :c- L -rJOC1&1: j..' Li* < -Ij.' I) Tonna luteostoma 1t;;(/)TV/i'J;Wl>
It--I- iJ'Ill~;kl:~'d:--o-C"J." fl-Jf;!hli Dosinia angulosa (/)El1:.-t J., Jill: lii~l1!:l: -tt.. BicornuC ythe re bisanens is - Neomonoce ratina mic ro re ticula te -r"{-f;'*: ~ h J., ft(/) ~m'I'I:(/)f!1, 'MJt,i'.'.'i~li'J,'~~ It.-I-Ii@:~ 1 kmilrWt(/),

h.1::lltf~lLt.: L(/)""(",

iJ'Th., Myaarenaria~ Tonna luteostoma 'i:-~iltTJ.,Jl!!-C··lift(/)~m'I'I:(/)i'.'.'i", li'J;i~I1!:I:T

V Pistocythereis bradyformis-Bythocythere ishizakiiM~I:~itLt.:, Mya arenaria MJt,
I: Pf -) fl-Jf; !h(/)M~ i: Tonna lu teos to ma MUH: Pf -) 1r-Jf; !hM* i: T'li &iJ'Sfj ~T'li -Ij."',1 ~~ Hanaicythere{Microcytheridae} !: 8~tJli.'i:-~cJl&Lt.:, Anchistrocheles i: Xiphich ilus ~Ii B * -c-l&M(/)¥fl.15--r-;h J."*&i;i11! rTrans. Proc. Palaeont. Soc. Japan, N. S., No. 146, pp. 77 -87,4 Figs., July 30, 1987

831. TETRACENTRON LEAVES FROM THE NEOGENE OF JAPAN*
KIMIHIKO OZAKI
Department of Geology, Faculty of Education, Yokohama National University,
Tokiwadai, Hodogaya-ku, Yokohama 240

Abstract. Hovenia masuzalVaensis from the late Miocene Masuzawa Formation of northeastern Honshu, Japan is re-examined and recognized to be entirely identical with Tetracelltronibei Suzuki from the late Miocene Kabutoiwa (upper Motojuku) /-ormation of central Honshu,
Japan. These two species arc re-classified as TetracentronlllaslizalVaense (Murai), n. comb. I discovered leaves that are referred to the genus Tetracelltron from the late Pliocene A tagi Formation of central Honshu. Species belonging to the genus Tetracelllron changed their habitat; subtropical forest till the Eocene, the lower zone of cool-temperate forest during the latc Miocene,
and cool-temperate forest in the late Pliocene. They arc presently growing in the warm-temperate forest of China and the Himalayas.

plex" and divided them into six taxa. Wolfe(1977) was the first one to discriminate theTetraeentron leaves from the Paleogene "CereidiphyllulIl aretieum complex" of Alaska. He listed
in the synonymy of this species, seven species ofPopulus, three species of Cercidiphyllulll, four
species of Zizyphys, two species of Troehodendroides, and one species of Cheallothus. Tanai(1981) also identified the Tetraeel1tron leaves
among the so-called "Cereidiphyllum" -like leaves
from the Paleogene of Japan. The recognition of
the Tetracentron leaves in these Paleogene floras
has led to the re-examination of many Tertiaryleaves which had been reported as Cereidiphyltum or under other names. I discovered Tetracentroll leaves from the late Pliocene Atagi Formation in central Japan; these leaves are probably the youngest fossil record of this taxon in
the world.
The purposes of this paper are mainly to reinvestigate Tetraeentron leaves from the Neogeneof Japan and to discuss the brief history of thistaxon.

Introduction
The genus Tetraeentron Oliver belonging to
the Tetracentraceae of Engler's Magnoliales or
Cronquist's Trochodendrales is a well known vesselles angiosperm. The distribution of the only
extant species is restricted to a region extending
from Nepal to western China as shown in Figure
1. However, it seems that Tetraeentron was not
an uncommon plant in the past throughout theworld, especially during Paleogene times. Many
Paleogene fossil leaves bearing a leaf architecture
similar to that of the modern Cercidiphyllulll
have been reported by many authors under various taxon names such as Cere idiphyllu m, Popu-lus, Troehodendroides, Grewia, Paliun/s, Zyziphus, and Ceanothus. Many of these fossil leaves,together with other distinctive seed and fruit fossils, were compiled into Cereidiphyllum aretieumby Brown (1939, 1962). But studies on thisspecies by Chandler (196 I) and Wolfe (J 966) revealed that fossils assigned to this species are ofdiverse taxonomic origin. Hickey (1977) called
these leaves the "Cercidiphyllum aretieum com-

Characteristics of the Tetracentron leaves*Received October 23, 1986; revised manuscript received June 11,1987.

As already mentioned, it is difficult to sepa77

Kimihiko OZAKI

78

.:~

(

,~
(y~8 ""
r~l/~~/~.
~>,r,,~~)'< .,,,'
~,9/

6 '~1
:::7

-

~.'1

.

"0',...

.'

2

~.
JO

,I 'C.-.p•

Cretaceous
Eocene14 .18"Miocene.~.
~(... Pl iocene.
@ Distribution of the extant sDecies\'(after Hara an~" Kanai, 1964)•

The broken symbol indicates
uncertain fossils

Figure 1. Distribution of Tetracentron and related fossils. References to those numbers appended to symbol marks are given in the text.

rate accurately those pre-Neogene toothed Cercidiphyllum-like leaves into individual species
based on their gross characters only. These preNeogene fossil leaves show a wide range of variation in their foliar shape and marginal and venation characters. Their morphological characteristics, differing from those of the Tetracentron
leaves, were dicussed by Iljinskaja (1972), Wolfe(1977), and Tanai (1981).
The defmition of the Tetracentron leaves
given by Iljinskaja (1972) is; thick petiole,wedge-shaped base, primary veins which originate
from petiole, and the existence of two series ofloops between the margin and the primary vein's
loops.
Wolfe (1977) stated the distinction of leavesof Tetracentron from those of the Cercidiphyllum as follows, the leaves of Tetracentron are
typically more elongated than those of Cercidiphyllum, the teeth of Tetracentron are typicallylarger and more equal-sided than those of Cercidiphyllum, and perhaps the most significant of
all is that in Tetracentron veins connect theglandular region of the tooth to the adjacentsinuses.
Tanai (1981) considered that the leaves of
Tetracentron are distinguished from those of

Cercidiphyllum mainly by: (1) large marginal
glands, (2) a pair of prominent veins converging
toward the tooth apex from the sinuses, and (3)Tetracentron leaves having a tendency to show a
flexuous looping of the secondary venins.
I think that the Neogene Tetracelltroll leaves
are also distinguishable from the similar-shaped
leaves by the marginal teeth and the venation
characters around the teeth in the same manneras their Paleogene equivalents, but the Neogene
Tetracentron leaves are rather easily distinguishable from their similar leaves based on the grosscharacters only. They are characterized by closely arranged five primary veins, a caudate apex,
marginal teeth which are slenderly triangular andhave a large gland on the terminal, and a cordatebase of which the both adaxial sides slightly
curve adaxially lacking the marginal teeth.

Description
Family Tetracentraceae
Genus Tetracentron Oliver
Tetracentron masuzawaense (Murai), nov. comb.
Figures 2-1-3, 3-3, 4-1,3,5.

831. Neogene Tetracentron Leaves of Japan
Hovenia masuzawaensis Murai, 1963, vol. 16, no. 2, p.
46-47, pI. 18, fig. 4, text-fig. 6.
Tetracentron ibei Suzuki, 1967, vol. 43, no. 6, p. 527530.
Populus balsamifera Linn., Yagi, 1931, vol. 43, no. 507,
pI. 2,fig. 1.

Type:-Holotype, IAGI coli. Cat. no. 61089,
Minamihata-gawa, Ma4, Shizukuishi-machi, Iwate-gun, Iwate Prefecture, Japan. (Masuzawa Formation, late Miocene).
Emended description:-Leaves cordate; lengthof 5.8 to approximately 13.5 cm (average 10.0cm) and width of 4.5 to approximately 9 cm
(average 6.3 cm); width/length ratio ranging from
0.52 to about 0.77 (average 0.64); apex caudateacuminate, length from the upper turning pointof the marginal curvature to the terminal of theapex measuring from 1.5 to 2.5 cm; base shallowly to deeply cordate; adaxial sides of the baselacking teeth, weakly curved adaxially, making
an angle of from 15° to 135° by each side; margin regularly serrated with slenderly triangularteeth; teeth upcurved, separated by acute sinuses,
and marked by round glands being located at thetermination of a vein on the tooth apex; thebasal side of the teeth convex, occasionallyacuminate, rarely straight, while the upper side
being concave, rarely straight; petiole thick,length of 1.5 to 3.0 cm, width of 2 to 3 mm,nearly straight or weakly curved, sometimes
bending at the blade, gradually thickening toward the proximal end.
Venation perfect basal acrodromous with fiveto rarely seven primary veins; distal part of primaries brochidodromous except for the midvein,
originating from the petiole, middle three veinsnearly equal in thickness, the other pairs weaker
than the middle three; distal part of primaries as
thick as the secondary veins. Midvein stout, nearly straight.
Admedial lateral primaries making an angle offrom 40° to 58° with each other, average value
being 48.7°; reaching nearly four-fifth of thelength from the base of the primary veins to theupper turning point of the marginal curvature;
course weakly upcurved, slightly recurved to the
mid vein or nearly straight in the proximal part79

on some leaves, extending approximately parallelto the midvein with slightly zig-zag course by
sending off or joining with the secondary veins in
the distal part; distal end bifurcating widely, theadaxial branch joining with a branch of the firststout secondaries from the rnidvein and making
an angular loop, the straight abaxial branch bifurcating and making angular loops with adjacentsecondaries.
Exmedial lateral primary veins making an angle of from 105° to 130° with each other, average value being 121.8°; extending approximately
straight or slightly upcurved with zig-zag course
and reaching one-third to two-fifth of the leaf
length; distal end bifurcating widely, the adaxial
branch joining with a branch of the basal secondaries from the inner lateral primaries and making
an angular loop, the straight abaxial branch bifurcating and making angular loops with adjacentsecondaries. One alternate pair of secondaryveins arise at angles of between 30° and 50° .fromthe midvein, the angle wider than those of theadmedial lateral primaries, upcurved, forked at
the distal end and joining with adjacent branchesof the lateral primaries or upper weak secondaries; weak secondaries in the apex forming elongated net along the rnidvein; about six abaxial
secondaries from the inner lateral primaries extending nearly parallel to the outer lateral primaries, bifurcating at its distal end and making
angular loops with the adjacents; from near thebase of the outer lateral primaries one pair ofstout secondaries extending to the basal side,forking or sending off a stout tertiary vein on theway and making angular loops, this pair in somelarge leaves changing to a weak primary vein
originating from the petiole.
Tertiary vein thin but distinct, angle of tertiary departure from the lower order veins ranging
from 45° to 75°, average being 60°; some of thetertiaries originating on the midvein being thicker
than the average; in intercostal area, orthogonal
reticulate to weakly percurrent; in marginal area,
flanking secondary loops by pentagonal to polygonal loops and one vein from the corner of theloops extending to the teeth apex. Quaternaryveins in intercostal area making polygonal meshes

80

Kimihiko OZAKI

Figure 2. Tetracentron masuzawaense from the Masuzawa Formation in northeastern Honshu, Japan andthe extant related species. 1. Venation of the holotype of Tetracentron masuzawaense (Murai) after Murai, X
0.8. 2. Upper marginal features of the holotype, X2. 3. Fine venation of the holotype, X8. 4. Venation of theextant Hovenia tomentel/a Nakai, X8. YNUPB slide no. 263. 5. Venation of the extant Tetracentron sinense
Oliver, X8. HUPB slide no. 1285. 6. Venation of the extant Tetracentron sinense Oliver vaT. himaiense Hara et
Kanai, X8. YNUPB slide no. 788.

831. Neogene Tetracentron Leaves of Japan
about 0.7 to 1 mm across, around the marginal
teeth running from the both upper and basalsides of the teeth and joining the teeth's midveinat the middle of or below the glands. Ultimate
veinlets mainly twice-branching.
Discussion: - The type specimen of "Hovenia"
masuzawaensis has following characters; closely
arranged five primary veins, slenderly triangularand incurved marginal teeth which have glands at
the terminal, a pair of veins that converge toward
tooth apex from near the sinuses, and a large
areolation which has commonly twice-branchedultimate veinlets. These features indicate that
this fossil represents a sepcies of the genus Tetracentron. As shown in Figure 2-4, leaves of
the genus Hoveina have a depressed gland at each
tooth apex and have a very small, irregular areolation intruded by a simple to once-branchedultimate veinlets.
The slenderly triangular marginal teeth set thisspecies apart from the Paleogene species, Tetracentron pip ero ides (Lesquereux) Wolfe. The
leaves of this fossil species differ from those of81

the extant Tetracentron sinense Oliver in having
the sharp marginal teeth and from the Tetracentron sinense Oliver var. himaiense Hara et
Kanai in having the large marginal teeth as shownin Figure 3.
Occurrence:-Late Miocene Masuzawa Formation of Iwate Prefecture, and late Miocene upper
Motojuku (Kabutoiwa) Formation of Gunma
and Nagano Prefectures, Japan.
Depository: - YNUG 31088-3110 I.

Tetracentron sp.
Figures 4-2, 4.

Description:-Leaves cordate, about 10 to 12
cm long and 6 to approximately 7 cm wide; apex
caudate-acuminate; base cordate; margin serrated
with slenderly triangular teeth except on thebasal adaxial sides; venation perfect basal acrodromous with five primary veins; primaries making an angle of about 20° with each other at thebase, course of the upper part of midvein slightly
sinuous; lateral primaries extending nearly

Figure 3. Marginal features of the extant Tetracentron and Tetracentron masuzawaense (Mura~) (allX4). 1. Tetracentron sinense Oliver var. himalense Hara et Kanai, YNUPB slide no. 788. 2. Tetracentron smense
Oliver, NSM Paleobot. Ref. Slide 1069. 3. Tetracentron masuzawaense (Murai), YNUG 31097.

Kimihiko OZAKI

82

straight, but weakly turned abaxially in the basal
part and weakly upcurved in the distal part; apair of secondary veins arising from the upper
part of the midvein at angles of from 35° to 45°,slightly upcurved near the base and extending
nearly straight or weakly curving up and making
a loop with inner lateral primaries at the end;
some secondaries originating at an angle of from
35° to 45° from the inner lateral primaries toabaxially course nearly straight or slightly upcurved, distal end not well preserved but making
loops with the adjacent secondaries; higher orderveins not preserved.
Discussion : -The cordate foliar shape, caudate-acuminate apex, cordate base, narrowly arranged five primary veins, and serrulate margin
with triangular teeth are characteristic featuresthat mostly ally these fossils to the genus Tetracentron. These fossil leaves are closely comparable with those of Tetracentron masuzawaense(Murai), n. comb. in having the slenderly triangular marginal teeth. However, owing to a lackof the fine venation, a definite identificationmust be reserved.
Occurrence:-Late Pliocene lower Atagi Formation, Atagi, Shirotori-machi, Gujo-gun, Gifu
Prefecture, central Japan.
Depository:-YNUG 31376-31382.
Tetracentraceae fossils from JapanThe oldest fossil species belonging to the
Tetracentraceae is Tetracentronites japonicus
Nishida from the Aptian in Choshi, Chiba Prefecture (Nishida, 1962). He stated that although it isa secondary wood, its characteristics are close to
those of the extant Tetracentron sinense Oliver.
Tanai (1981) distinguished Tetracentron piperoides (Lesquereux) Wolfe from the Cercidiphyllum-like leaves in the Eocene Ikushunbetsu Formation of Hokkaido and in the Minato Formation of Iwate Prefecture on the basis of detailed~

comparative analyses of leaf characters with acleared leaf of the extant species.
From the Eocene Nameiri Formation of Iwate
Prefecture, northeastern Honshu, a fragmentaryleaf was figured as Cercidiphyllum sp. (n. sp.?)by Murai (1977). It seems to belong to the genus
Tetracentron as judged from its sharp marginal
teeth.
From the late early Miocene Mizunami Group
in central Honshu, Ina (1981) figured a single
leaf as Tetracentron sp. However, its foliar shape,
venation characters and marginal teeth indicatethat this specimen should be referred to thegenus Populus.
Suzuki (1967) described Tetracentron ibei
Suzuki from the late Miocene upper Motojuku(Kabutoiwa) Formation of Gunma Prefecture,
central Honshu.
Hovenia masuzawaensis Murai was describedon the basis of a single leaf from the late Miocene
Masuzawa Formation of Iwate Prefecture in
northeastern Honshu by Murai (1963). It has narrowly arranged five primary veins, acute marginal
teeth, and large-sized ultimate networks (Figures
2-1-3). These characters, however, coincide withthose of Tetracentron and are closely comparable
to those of Tetracentron ibei Suzuki except for
its large foliar size. Though fragmentary, someleaves of Tetracentron ibei Suzuki which areslightly larger than those of the Hovenia masuzawaensis Murai are found at the original localityof the Tetracentroll ibei Suzuki. Therefore, these
two species are considered to belong to the same
species.
In the Minoshirotori flora reported by Matsuo(1968) from the Atagi Formation in northern
Gifu Prefecture, central Honshu, I discovered
several distinctive leaves at the Atagi locality. Althougl1 their fine venation is not preserved, thoseleaves show a characteristic feature of Tetracentron; the cordate foliar shape, the acuminate
apex, the densely arranged five primary veins andFigure 4. 1, 3, 5. Tetracentroll masuzawaellse (Murai) Ozaki n. comb. from the south of Mt. Arafune,Kama-gun, Gunma Prefecture, Kabutoiwa (upper Motojuku) Formation: 1; YNUG 1094, X1.5. 3; YNUG
31092, Xl. 5; YNUG 31096, X4. 2,4. Tetracentroll sp. Xl from Atagi, Shirotori-machi, Gujo-gun, Gifu Prefecture, Atagi Formation. 2; YNUG 31377. 4; YNUG 31376. 6. Tetracentroll sinellse Oliver, NSM Paleobot. Ref.
Slide 1069, X4. 7. Cercidiphyllumjaponicum Sicb. et Zucco YNUPB slide no. 70, X4.

831. Neogene Tetracentron Leaves of Japan83

Kimihiko OZAKI

84

the closely arranged slenderly triangular marginal
teeth. The Minoshirotori flora is predominatedby Fagus sp. cf. F. crenata Blume, which is accompanied by such species as Quercus sp. cf. Q.
mongolica Fischer var. grosseserrata (Blume)
Rehd. et Wils., Betula sp. cf. B. grossa Sieb. et
Zucc., Tilia sp. cf. T. japonica Simonkai, Acersp. cf. A. mono Maxim., and others.
These Tetracentron leaves from the Minoshirotori flora are considered to represent the
youngest fossil record of this taxon in the world
at present.
Tetracentraceae fossils in the world
Iljinskaja (1972) described two oldest speciesof Tetracentron of Albian age based on leaves;
one from the Kizilchenskaya Formation in theWest Kazakh district and another from the BourKemjuska Formation in the Kolyma district in
USSR. Tetracentron vachramevianum Iljinskaja
was described based on a small leaf, only about
2.5 cm in width and nearly the same in length.
This leaf is similar to the extant one in the morphology including the basal shape, features ofthe marginal teeth, and the primary veins which
extend from the petiole. However, further detailed study should be done before this leaf could
be assigned to the extant genus. The leaves ofanother species, T. potomacense (Ward) Iljinskaja
are also small ones. Judging from thier leaf characters, this form is hardly assignable to the genus
Tetracentron. The type specimen described as"Populus potomacensis" by Ward was reported
from the Potomac Group of the eastern UnitedStates. Hickey and Doyle (1977) considered thisPotomach specimen to be classified as "Populus"
potomacensis Ward. Kryshtofovich (in Kryshtofovich and Baikovskaja, 1966) described Tetracentron amurense Kryshtofovich from the uppermost Cretaceous in the Bureya basin of the Amur
district, East Asia. Based on the photographs(Kryshtofovich, 1966, pI. 17, fig. 1; pI. 18, fig. 2)
which exhibit a characteristic morphology of theleaves, including the basal shape, features of thebasal primary veins, and the marginal venation,these leaves seem to differ from those of the ex-tant Tetracelltron. Among the Paleogene Cercidiphyllum-Iike leaves known from the western
United States, Wolfe (1977) first discriminatedthe Tetracentron leaves as T. piperoides (Lesquereux) Wolfe. Andreanszky (1959) reported Tetracentron hungaricum Andreanszky form the Miocene of Hungary. These leaves show features different from those of Tetracentron, especially inthe undulate or crenate margin. Iljinskaja (1968)
included it in the genus Cercidiphyllum.
Some homoxylous woods of Mesozoic andTertiary ages were reported under such names as
Homoxylon aviasii Boureau, H. neocaledonicum
Boureau, and H. australe Boureau from the Jurassic and Triassic of New Caledonia; H. ugaminum
Jarmolenko and H. uralense Jarmolenko fromthe Jurassic and Cretaceous of central Asia in
USSR; Tetracentronites hartzi Mathiesen fromthe Eocene of Greenland; T. hungaricum Gregus
from the Miocene of Hungary; and Pataloxylon
scalarifom1e Sahni from the Tertiary of near
Brisbane in Australia. However, Nishida (1962)
mentioned that it is not certain whether these
Mesozoic homoxylous woods belong to angiosperm or Bennettitales, and morphological characteristics of Tetracentronites hartzi Mathiesen
are close to the wood of living Trochodendron.
Conclusion
Fossils which really belong to Tetracentroll
have been known mainly from western North
America and Japan (Figure 1).
In North America, Tetracentron has been recorded from the Palaeocene to Eocene. Wolfe(1977) suggested that Tetracentron was a member of the lowland tropical or paratropical forest
during Eocene time in the western United States.
It would not invade into the highland forest in
the late Eocene, and was unable to adapt itself
to the warm-temperate forest in the Oligocene.
It diminished in Noth America due to deteriorating climates at the end of Eocene.
In Japan, Tetracentron seems to have grownin a warm lowland area during the Aptian. In
the Eocene it lived in the lowland forest undersubtropical to warm-temperate climates as in831. Neogene Tetracentron Leaves of Japan
North America. From early to middle Miocene
time, temperate to cool-temperate Aniai-typefloras and warm-temperate to subtropical Daijirna-type floras are considered to have flourishedaround the Japanese Islands (Tan ai, 1961; Huzioka, 1964). There have been many records ofthese floras, but no Tetracentron fossils havebeen found in them. It seems that Tetracentron
was strongly affected by the deterioiating climateof the latest Eocene giving rise to a temporary
extinction from the Japanese area. Otherwise,
it seems hardly possible that their leaves werecounted under other species names such as
Cercidiphyllul1l or Populus.
In the late Miocene, Tetracentron grewin the lower zone of a cool-temperate forest
around inland lakes in northeastern and central
Honshu. As evidenced by the composition of the
Minoshirotori flora in central Japan, the genus
must have survived at least until the late Pliocene
under a cool-temperate condition in Japan.
The extant species is growing in a warm-temperate, mixed mesophyte forest of China and theHimalayas.
Acknowledgments
I wish to express my sincere appreciation to
Dr. Toshirnasa Tanai, former Professor of Hokkaido University, for his continuous guidance
relating to theoretical problems and his encouragement during the course of this study. I am
also indebted to Professor Makoto Shima, Yokohama National University, for critical reading of
the manuscript. I extend my cordial thanks to
Dr. Hiroo Kanai and Dr. Kazuhiko Uemura, bothof National Science Museum, and Professor
Hideaki Oba, the University of Tokyo, for providing the present author with many facilities
to investigate the extant species in their herbaria.
Thanks are also due to Dr. Jack A. Wolfe, U.S.
Geological Survey who kindly taught me the ageof those formations in the United States.
References
Andreanszky, G. (1959): Die flora der Sarmatischen
Stufe in Ungarn. Akad. Kaido Budapest, p. 61-62.

85

Andrews, H. N. (1970): Index of generic names of fossil
plants, 1820-1965. U. S. Ceol. Surv. Bull., 1300,
p. 1-354.
Brown, R. W. (1935): Miocene leaves, fruits, and seeds
from Idaho, Oregon, and Washington. Jour. Paleont., vol. 9, p. 572-587.
--(1939): Fossil leaves, fruits, and seeds of Cercidiphyl/um. ibid., vol. 13, p. 51-56.
- - (1962): Paleocene flora of the Rocky Mountains
and Great Plains. U.S. Ceol. Surv. Prof Paper,
375, p.l-l10.
Chandler, M. E. 1. (1961): The lower Tertiary floras ofsouthern England I. Trustees British Mus. (Nat.
Hist.), London, p. 1-354.
Hara, H. and Kanai, H. (1964): The discovery of Tetracentron in East Nepal. Jour. Jap. Bot., vol. 39(7),p.193-195.
Hichey, L. 1. (1977): Stratigraphy and paleobotany of
the Golden Valley Formation (Early Tertiary) of
Western North Dakota. Ceol. Soc. America, Mem.,
150, p. 1-181, pis. 1-55.
- - and Doyle, 1. A. (1977): Early Cretaceous fossil
evidence for Angiosperm evolu tion. Bot. Rev.,
vol. 43, p. 3-104.
Huzioka, K. (1964): The Aniai flora of Akita Prefecture, and the Aniai-type floras in Honshu, Japan.
Jour. Min. Coll.. Akita Univ., Ser. A. vol. 3, p. 1105.
Iljinskaja, I. A. (1968): Neogene flora of the Transcarpathian region of the USSR. Nauka, Moscow,
p. 63-64 (in Russian).
- - (1972): Correction of the volume of the genus
Trochodendroides and new fossil species of Cocculus. Bot. Jour., vol. 57(1), p. 17-30 (in Russian).
Ina, H. (1981): Miocene fossils of the Mizunami Group,
central Japan. Monog. Mizunami Fossil Mus., no. 2,
pI. 4, fig. 5 (in Japanese).
Kryshtofovicn, A. N. and Baikovskaja, N. T. (1966):
Selection from the works of Kryshtofovich 3.
Nauka, Leningrad, p. 281-283 (in Russian).
LaMotte, R. S. (1952): Catalogue of the Cenozoic
plants of North America through 1952. Ceol. Soc.
America, Mem .. 51, p. 1-381.
Matuo, H. (1968): A study on Neogene plants in the
inner side of central Honshu, Japan. II. On the
Minoshirotori flora (Pliocene) of the Paleovolcanolake Deposits. A nna/. Sci. Kanazawa Univ., vol. 5,
p.29-77.
Murai, S. (1963): Geology and paleobotany of the
Shizukuishi basin, Iwate Prefecture, Japan (PartII-2). Rep. Tech., [wate Univ., vol. 16, p. 46-47,
pI. 18, text-fig. 6.
(1977): Fossil flora from the Iwate Clay Mine in
Kogawa, Iwaizumi-machi, Iwate Prefecture. Professor Kazuo Huzioka Mem. Vol., p. 315-324, pI.

Kimihiko OZAKI

86

1-3 (in Japanese).
Nishida, M. (1962): On some petrified plants from theCretaceous of Choshi, Chiba Prefecture. Japan.
Jour. Bot., vol. 18(1), p. 87-104.
Suzuki, K. (1967): Discovery of Tetracentron leaves
from the Neogene in Japan. Proc. Jap. Acad., vol.
43, p. 526-530.
Tanai, T. (1961): Neogene floral change in Japan. Jour.
Fac. Sci., Hokkaido Univ., Ser. IV, vol. 11, p.
119-398.
--(1981): The revision of the so-called "Cercidiphyllum" leaves from the Paleogene of North Japan.
Ibid., vol. 19, p. 451-484.
Wolfe, J. A. (1966): Tertiary plants from the Cook Inlet
region, Alaska. U.S. Geol. Surv., Prof Pap., 398-b,
p.I-31.
- - (1977): Paleogene floras from the Gulf of Alaska
region. Ibid., 997, p. 1-108.
Yagi, T. (1931): Relation of the geology of Arafune
volcano with the flora found at Kabutoiwa. Jour.
Geogr., vol. 43, no. 507, p. 268-283 (in Japanese).

Appendix
List of the species reported as Tetracentraceae or identified to be Tetracentron. (The numbers in the double
parentheses correspond to those of Figure 1).

Tetracentronites japonica Nishida; Nishida (1962), p.
92-95, pI. 7 -8; Choshi, Chiba Prefecture, Japan;
Toriakeura Formation, Aptian «(1)).
Tetracentron ibei Suzuki; Suzuki (1967), p. 526-530,
Motojuku, Gunma Prefecture, Japan; Kabutoiwa(Motojuku) Formation, late Miocene «2».
Tetracentron potomacense? (Ward) Iljinskaja; Iljinskaja(1972), p. 21-22, Zyryanka, Yakutsukaya ASSR,
USSR; Kour-Kemjuska Formation, Albian «3)).
Tetracentron vachrameevianum Iljinskaja; Iljinskaja(1972), p. 21-22, Karachtau, Kazakhstan SSR,
USSR; Kizilchenskaja Formation, middle Albian«4)).
Tetracentron amurense Kryshtofovich; Kryshtofovich
and Baikovskaja (1966), p. 281-283, pI. 17, fig. 1,
pI. 18, fig. 2; Tsagajan, Amur Prov., USSR; Danii
Tjukanskaja Formation, Maastrichtian «5».
Tetracentron hungaricum Andreanszky; Andreanszky(1959), p. 61-62; Ungarun, Hungary; Sarmatian.
Tetracentron sp., Ina (1981), pI. 4, fig. 5; Mizunami,
Gifu Prefecture, Japan; Akeyo Formation, early Miocene.
Hovenia masuzawaensis Murai; Murai (1963), p. 46-47,
pI. 18, fig. 4, text-fig. 6; Masuzawa, Shizukuishi,
Iwate Prefecture, Japan; Masuzawa Formation late'
Miocene «6».
Cercidiphyllum sp., Murai (1977), pI. 3, fig. 2; Kogawa,Iwaizumi-machi, Iwate Prefecture, Japan; Nameiri
Formation, Eocene «7)).

Tetracentron piperoides (Lesquereux) Wolfe; Wolfe(1977), p. 61-62, pI. 5, fig. 4, pI. 22, fig. 3, pI.
28, fig. 7; near Yakataga, Alaska, U.S.A.; Kushtaka
Formation, late Eocene «8)); Kulthieth Formation, early Eocene «9»; Tanai (1981), p. 462464, pI. 2, figs. 7,8, pI. 4, fig. 3, pI. 6, figs. 2,7;
Kuriyama and Shimizusawa, Sorachi district, Hokkaido, Japan; Ikushunbetsu Formation, late Eocene ((10»; Minato and Ube, Kuji, Iwate Prefecture, Japan; Minato Formation, late Eocene «(11».
Tetracelltron sp. Atagi, Shiratori-machi, Gifu Prefecture, Japan; Atagi Formation, late Pliocene «22)).
(The following specimens cited as synonymy of Tetracelltron piperoides by Wolfe (1977) are known from
U.S.A.)
Ceanothus idalzoensis Brown; Brown (1935), p. 581, pI.
69, fig. 8; G. W. Oliver coal mine, Salmon, Idaho;
Eocene «(12».
Cercidiphyllum crenatum Brown non Grewia crenata
Unger; Brown (1935), p. 575, pI. 68, figs. 1,6;
Republic, Washington; Eocene «(13».
Cercidiphyllum elongatum Brown; Brown (1939), p.
494, pI. 55, figs. 1, 2, 7, pI. 56, fig. 9; You Bet,
Nevada, Calif.; lone Formation, Eocene «(14):pI. 55, fig. 7; Steel's Crossing, Renton, Seattle,
Washington; Eocene «(15»: pI. 55, fig. 9; G. W.
Oliver coal mine, Salmon, Idaho; Eocene «(12»:MacGinitie (1941), p. 112-113, pI. 12, fig. 4, pI.
13, fig. 4, pI. 14, figs. 1, 2; around Nevada City,
Nevada, Calif.; lone Formation, Eocene «(14)):Becker (1961), p. 66, pI. 10, fig. 8, pI. 19, figs. 15; Upper Ruby River Basin, Montana; Tertiary
fossiliferous shales, Eocene «(16».
Populus daphnogenoides Ward; Populus galndulifera
a.n. Heer; Populus speciosa a.n. Ward; Populus
xantholithensis Knowlton; Knowlton (1899), U.S.
Geol. Surv. Mon., 32, p. 694-695, pI. 84, figs. 13; pI. 85, figs. 1,2; Elk Creek, Yellowstone National Park, Wyoming; "Early acid breccia" Eocene«(17».
'
Populus richardsonii a.n. Heer; Lesquereus (1878),
U.S. Geol. Surv. Terr. Rept., 7, p. 177, pI. 22, figs.
10-12; Elko, Nevada; Eocene «(18».
Populus rotundifolia a.n. Newbery; Dawson (1895),
Royal Soc. Canada Trans., 2nd Ser., 1(4), p. 147,
text-fig. 10; Burrard Inlet, Vancouver, B.C.; Eocene «(19)).
Populus smilacifolia a.n. Newbery; Jennings (1920), p.
409, pI. 26, fig. 4; White River, Missoula, Montana;
Eocene «20».
Trochodendroides arctica Berry non Populus arctica
Heer; Berry (1926), Canada Geol. Surv. Bull.,vol. 42, p. 103, pI. 13, figs. 1-4; Kitsalano, Vancouver; Eocene: Newhuykulston Creek; Eocene.
Trochodendroides zaddachi Sanborn non Populus zaddachi Heer; Sanborn (1935), p. 16, pI. 3, fig. 2;

831. Neogene Tetracentron Leaves of Japan
Comstock, Douglas Co., Oregon; Comstock Formation, Eocene ((21)).
Zizyphus cali/ornica Knowlton and Cockerell (1919),
U.S. Ceol. Surv. Bull., 696, p. 659.
Zizyphus microphyllus Lesquereux; Lesquereux (1878),
Harvard Coll. Mus. Compo Zool. Mem., vol. 6(2),Akeyo IVlttt, Arafune
Gunma

m;.

iiP1!"

iii~;j.

Atagi I:") ~1~1. Chiba

p. 28, pI. 8, fig. 9; Chalk Bluffs, Nevada Co., Calif.;
lone Formation, Eocene ((14).
Zizyphus piperoides Lesquereux; Lesquereux (1878),
ibid. pI. 8, figs. 10, 11; Chalk Bluffs, Nevada Co.,
Calif.; lone Formation, Eocene ((14)).

T-JIIO.

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IIokkaido ~tiiltju. Ikushunbetsu ~li:ffjJl]. Iwaizumi -fil~. Iwate'feE.

Kabutoiwa

Kanra-guntl';~~m;.

87

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machi 'li'TiIIlT. Sorachi'iiffi. Toriakeura l"iIlJlifli. Ube 'YifJ:.
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88
New members approved by the council meeting on June 18, 1987.
ZHOU Baochun, MATSUBARA Akiko, IKEJIRI Hiroyuki, OKURA Masatoshi, HACHIY A Kiichiro,
OHE Fumio, OKAMOTO Masanori, KANEKO Naotomo, TAKAI Yuji, JYOCHI Kotohiro, OTA Yasuhiro, KIYOKAWA Shoichi, NAGAI Hiromi, KOBAYASHI Mariko, OGATA Masashi, KHONO Naoki,
KOIZUMI Akihiro, ISAlI Shinji, SATO Atsushi, UEMATSU Tomosaburo.
Deceased member
KURODA Tokubei (Honorary Member)
Seceding member
TAKAMURA Kazuko, SASAGAWA Ryoichi, OKURA Mitsuko, NAKAI Hideki, YASUHARA Naoki(Ordinary Members)
Nicchu Petroleum Exploration Co. (Patron Member)

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Transactions and Proceedings of the PalaeontologicalSociety of Japan

New Series No. 146

July 30, 1987

CONTENTS
TRANSACTIONS
828. NIKO , Shuji and NISHIDA, Tamio: Early Permian cephalopods from the Mizuyagadani Formation, Fukuji distric t , central Japan . . . . . . . . . . . . . . . . . . . . . . . . . . 35
829 . MATSUMOTO, Tatsuro and YOKOI, Katsujoh:

Tiny ammonite Worthoceras from

Hokkaido (Studies of Cretaceous ammonites from Hokkaido- LX) .... . . . . . . . . 42830. YAJIMA, Michiko: Pleistocene ostracoda from the Atsumi Peninsula, central Japan . . 49

·83l. OZAKI , Kimihiko: Tetracentron leaves from the Neogene of Japan . . . . . . . . . .. . 77,
PROCEEDINGS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 88