ISSN 0031-0204

Transactions and Proceedingsof thePalaeontological Society of Japan
New Series

No.

160

Pa laeo ntologica l Society of J a pan
December 30,

1990

Co-Editors

Hisayoshi Igo, Hiroshi Noda and Kei Mori
Editorial Board

Yoshikazu Hasegawa (Yokohama National University), Itaru Hayami (University of Tokyo),
Hisayoshi Igo (University of Tsukuba), Makoto Kato (Hokkaido University), Itaru Koizumi(Hokkaido University), Yasumochi Matoba (Akita University), Kei Mori (Tohoku University),
Hiroshi Noda (University ofTsukuba), Kazushige Tanabe (University ofTokyo), Tsunemasa Saito(Tohoku University), Kazuhiko Uemura (National Science Museum), Akira Yao (Osaka City University)

Officers for 1989-1990
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The fossil on the cover is Phillipsia ohmorensis Okubo, an Early Carboniferous trilobite
from the Hikoroichi Formation in the Higuchizawa valley, Ofunato City, Iwate Prefecture, northeast Japan (Collected by A. Haga, PAt 5766, X 3.0; after Kobayashi and
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Trans. Proc. Palaeont. Soc. Japan, N.S., No. 160, pp. 609-617,7 Figs., December 30, 1990

907. A NEW SPECIES OF VEPRICARDIUM (BIVALVIA;
MOLLUSCA) FROM THE MIOCENE KATSUTA GROUP IN
OKAYAMA PREFECTURE, SOUTHWEST JAPAN*
EIJI T AGUCHI
982 Nishigata, Niimi City, Okayama Prefecture 718

Abstract. An interesting new cardiid belonging to the genus Vepricardium was
discovered from a mudstone of the Middle Miocene Yoshino Formation of the Katsuta
Group in Okayama Prefecture, southwest Japan. This species, Vepricardium (Vepricardium) okamotoi, sp. nov., is described herein, and its average relative growth is examined.
Judging from the mode of occurrence, lithofacies and associated forms, this species must have
lived in a muddy bottom in the inner sublittoral zone, and is regarded as an indicator of atropical marine environment at that time.
Key words.

Vepricardium, Cardiidae, Katsuta Group, Miocene, Southwest Japan.

the type locality (Figure 1). The Yoshino
Formation around this locality disconformably overlies the Uetsuki Formation and iscomposed of basal conglomerate, tuff andmudstone with intercalations of lignite inascending order. The molluscan fossils including a new cardiid are collected from theuppermost part of the Yoshino Formation asshown in Figure 2.

Introduction
A large number of molluscan specimens
were collected from the Yoshino Formationof the Katsuta Group (Kawai, 1957) at Niida,
Tsuyama City, Okayama Prefecture by T.
Osafune and A. Obayashi. Based on some ofthese molluscs, I have already reported Pernaoyamai, Tellinella osafunei and Nipponarcajaponica as new to science (Taguchi, 1983a,b). On the other hand, a geological investigation around the fossil locality has been
made by me during the past five years.
In this paper, an interesting new cardiid
shell is described together with the discussion
on its average relative growth and paleoecological characteristics.

Description of new species of Vepricardium
Family Cardiidae Lamarck, 1809
Subfamily Cardiinae Lamarck, 1809
Genus Vepricardium Iredale, 1929
Subgenus Vepricardium (s.s.) Iredale, 1929
Vepricardium (Vepricardium) okamotoi
Taguchi, sp. nov.

Fossil locality and geologic setting

Figures 6-1 a - lOb, 7

A new cardiid species occurs in a mudstoneof the Yoshino Formation at Niida, Tsuyama
City, Okayama Prefecture. This site (Lat.
3Y3'5"N, Long. 134°4'1"E) is designated as

Material. - Twenty-three specimens are
examined. Among them, 10 specimens are
selected as the type. Holotype: MFM20015,
Paratypes: MFM20016, MFM20017, MFM20022, MFM20025, MFM20027, MFM20031,*Received November 13, 1989; revised manuscript
accepted October 22, 1990
609

Eiji Taguchi

610

Mimasakaohsaki
(

i

City

i..

r··-··.....,··....

" .. " , :

i

o

1

1==:1

..

(

"\

r··-·

./)

134°Q'l"E

Figure 1.

Fossil locality (X).

MFM20033, MFM20034, MFM20037.
Diagnosis. - Radial ribs numerous, adorned
with many prickles. Dentition composed ofmoderate cardinal and lateral teeth.
Description. - Shell moderate in size, moderately thick, fairly inflated, subquadrate inshape; equivalve, inequilateral, slightly longer than height. Antero-dorsal margin short,obliquely straight, connected well-rounded
anterior margin. Postero-dorsal margin longer than antero-dorsal one, nearly straight,
passing into subquadrate or arched posterior
margin. Ventral margin broadly rounded.
External surface of shell sculptured by concentrics and radials. Concentric lines
smooth in main part but imbricated in anterior and posterior parts. Radial ribs 44 to 52
in number, averaging about 47, provided withmany prickles on posterior ribs, roundtopped in anterior and posterior parts but
flat-topped in the main part. Interstices ofradial ribs shallow, angular in cross section,
wider than ribs in anterior and posterior parts
while narrower in main part. Beaks low,pointed, pro so gyrate, situated near the middleof the shell or a little anteriorly. Umbo
more or less swollen. Lunule cordate and.. ""\ ).<.\osmooth; escutcheon smooth, pointed at
postero-dorsal corner. Dentition composedof cardinals and laterals; anterior cardinal
tooth obliquely straight; posterior one short,vertical; laterals located at the same distancefrom beaks; anterior tooth large, trigonal;
posterior one long, linear, curved. Hinge plate
stout, broadly arched. Inner margin seems
to be crenulated. Muscle scar and pallial
line unknown.
Repository.- The specimens described are
all kept in the collection of Mizunami Fossil
Museum with prefix of MFM.
Comparison.- This new species is closely
related to Regozara fraseri Garrard (1963), a
recent cardiid from Queensland, Australia in
its general feature, but is distinguished therefrom by its larger number of radial ribs andless numbered prickly ribs. This species isalso allied to the recent Vepricardium pulchricostatum Iredale (1929) described from
Sydney, Australia in its outline, but differsfrom the latter in its quadrate, smaller andlower shell with a larger number of radialribs, which have prickles only in the posterior
part. Of fossil species, Vepricardium kyushuense originally reported from the Miyaza-

907.

Miocene Vepricardium

611

Kawai

( 1957)

x
c
o
+-I

ro
E
!....
o

0.
:J

o

!....

U.

tJ

§I 1
~ 2
~3

H

rnmo 4-1°0001 5

o

c

.r:.
til

o

6

w 7

>-

X 8

c

5m

~.~
:J+-I
ro
tll
+-IE
(1)

L

!....

Figure 3. Basic morphology for measurements.
L: Shell length, H: Shell height, T: Shell thickness, a: Angle of antero-dorsal and postero-dorsal
margins.

::>0
U.

BasementrockoFigure 2. Geologic column at Niida , Tsuyama
City . I: Mudstone, 2: Pebble bearing sandy mudsto ne, 3 : Tuff, 4: Lignite, 5 : Pebbly conglomerate,
6: Basement rock , 7: Nodule, 8: Fossils.

ki Group by Shuto (1960) most resembles thisspecies in shel l size and the shape of ribs.
The former , however, is distinguishable fromthe latter by its more round shell with a large
and touching umbo and a smaller number ofradial ribs possessing prickles in both theanterior and posterior parts. Otuk a (1938)
described a cardiid from the Bihoku Group in
Shobara City, Hiroshima Prefecture as Cardium (Bucardium) ogurai . In comparison
with thi s new species, C. (B .) ogurai has themore swollen shell with no prickles on theradial ribs and a sma ller number of ribs i.e.
36- 40 in number.

The specific name of this new species isdedicated to Kazuo Okamoto of Hiroshima
University.
Biometry. - For the purpose of clarifying
the growth pattern of this new species, abiometrical ana lysis is made after the methodsof Hayami (1969) and Nod a (1986). The
basic morphology for measurements is shownin Figure 3. The morphologies of she ll aremeasured and the ratio of shell length to shellheight (L j H) and of she ll thickness to shellheight (T j H) are calculated as shown in
Table 1. Biometric characters such as meanva lue, standard deviation and Pearson's
coefficient variation concerni ng number ofradial ribs, a , Lj H and T j H are a lso calculated. These data are shown in Table 2.
Table 3 shows data of the average relative
growth of this new species. Based on Table
3, the reduce majo r axis is demonstrated in
Figures 4 and 5. Considering the correlation

Eiji Taguchi

612
Table 1.

Measurements of Vepricardium (s.s.) okamotoi, sp. nov.

Registered
No.

Valve

Length(mm)

Height(mm)

Thickness(mm)

No. of
ribs

a

L/H

T/H

MFM20015

Right

30.3

29.9

21.3

47

120

1.01

0.71

2J.l

20.8

15.3

50

117

1.01

0.74

25.4

24.0

17.7

48

119

1.06

0.74

45

119

1.09

0.75

47

120

1.05

0.72

Left

MFM2oo16

Left

MFM20017

Right

MFM2oo18

22.4

24.5

16.7

MFM20019

Right

19.0

18.1

13.1

MFM20020

Left

21.0

20.8

14.4

51

116

1.00

0.69

MFM20021

Right

23.3

22.6

15.8

47

115

1.03

0.70

MFM20022

Left

15.9

15.7

11.9

48

115

1.01

0.76

MFM20023

Right

24.7

24.4

17.0

47

114

1.01

0.70

MFM20024

Right

29.2

28.1

20.9

46

117

1.04

0.74

MFM20025

Right

26.5

25.1

17.7

45

1.06

0.71

MFM20026

Right

19.7

18.8

13.3

45

118
122

1.05

0.71

MFM20027

Right

14.6

111

~6

48

126

1.11

0.73

MFM20028

Right

26.4

26.3

19.0

44

125

1.00

0.72

MFM20029

Right

17.0

16.8

12.1

45

117

1.01

0.72

23.6

23.3

16.5

44

117

1.01

0.71

21.0

47

124

1.05

0.74

Right

MFM20030
MFM20031

Right

29.9

28.4

MFM20032

Left

25.3

23.8

17.9

45

116

1.06

0.75

MFM20033

Left

32.2

28.8

21.4

52

124

1.12

0.74

MFM20034

Left

35.0

34.8

24.7

46

119

1.01

0.71

MFM20035

Right

26.5

25.2

18.0

48

126

1.05

0.71

MFM20036

Left

26.7

25.4

18.5

46

116

1.05

0.73

a ; Angle of antero-dorsal and postero-dorsal margins, L/H; Ratio of shell length to shellheight, T /H; Ratio of shell thickness to shell height.

Biometric characters of Vepricardium(s.s.) okamotoi, sp. nov.

Table 2.

Number ofradial ribs

a

L/H

T/H

22

22

Table 3.

Data showing the average relative growthof Vepricardium (s.s.) okamotoi, sp. nov.

a

f3

fI'

Land H 0.995 1.057 1.3779 1.3603
N

22

22

m

46.8

119.2

1.040

0.724

2.075

3.664

0.034

0.019

4.434

3.074

3.269

2.624

v

N ; Sample size, m; Meam value, s; standard deviation, v; Pearson's coefficient variation.

coefficient and the sample size, the null
hypothesis of "isometry" cannot be rejectedjudging from the table and figure of Hayami
and Matsukuma (1971). That is to say, therelations of shell length versus shell height
and of shell thickness versus shell height

T and H 0.998 0.730

T'N

0.9894 22

1.3603 1.21990.9908 22

a ; Growth ratio, f3; Initial growth index, [,.
Mean of L' (L'=log L), fI'; Mean of H' (H'=log
H), T'; Mean of T' (T' = log T), r; Correlation
coefficient, N; Sample size.

represent to be "isometry", respectively.
Remarks on paleoecology.-A lot of molluscan specimens including Vepricardium(Vepricardium) okamotoi, sp. nov. are
obtained from a mudstone of the Yoshino
Formation at Niida, Tsuyama City. The
identified species composed of 19 pelecypod

907.

Miocene Vepricardium

species and 37 gastropod species are listed inTable 4. All pelecypods except Ostrea sp.
nov. occur with conjoined valves, and gastopods suffer little injury and wear. Thismode of occurrence indicates that the fauna is
autochthonous. This assemblage, which has
been named Tellinella-Perna- VepricardiumVicaryella (Ohe et al., 1986), represents a

L=l . 05 7H 0.995

40

.-

E
E

-

r=0.9894
30

20

...J

10~--------~----~~~~

10

H

(mm)

Figure 4. Relationship between shell length(L) and shell height (H) in Vepricardium (s.s.)okamotoi, sp. nov.

.E30

r=0.9908E-

T=0.730Ho. 998

20

10
9

20

30

H

(mm)

40

Figure 5. Relationship between shell thickness(T) and shell height (H) in Vepricardium (s.s.)okamotoi, sp. nov.

613

Fossil molluscs collected from a mudstone of the Yoshino Formation of the
Katsuta Group at Niida, Tsuyama City.
Number ofSpecific nameindividuals
13
Nipponarca japonica Taguchi
Scapharca abdita (Makiyama)
4
Perna oyamai Taguchi
1110
I
Anomia sp.
Ostrea sp. nov.
96
2
Modiolus (Modiolusia) sp.
4
Cycladicama cumingii kukinagaensis
Hayasaka
I
Eucrassa tella ? sp.
Vepricardium (s.s.) okamotoi, sp. nov.
570
2
Cardilia toyamaensis Tsuda
Tellinella osafunei Taguchi
1556
Gari sp.
I
Psammobia sp. nov.
73
I
Pharella sp.
Trapezium cheonbugensis Y oon
II
T. modiolaeforma Oyama et Saka
Paphia euglypta ohiroi Masuda
3
I
Mactra sp .
4
Clementia japonica Masuda
Calliostoma (Tristichotrochus) myon19
chonensis Hatai et Kotaka
Tristichotrochus sp.
Cantharidus mizunamiensis Itoigawa et
Shibata
Chlorostoma sp.
I
Teinostoma yabei Masuda
I
Turbo (Marmorostoma) minoensis Itoigawa
I
Lunella sp.
35
I
Neritina sp.
I
Littorinopsis miodelicatula Oyama
I
L. sp.
Turritella (s.s.) kiiensis Yokoyama
73
T. sp.
4
Vicaryella bacula (Yokoyama)
V. ishiiana (Yokoyama)387
22
V. notoensis Masuda
24
Terebralia sp. nov.
I
Batillaria toshioi Masuda
3
B. sp. nov .
I
Tateiwaia tateiwai (Makiyama)
5
T. yamanarii (Makiyama)
7
T. sp.
6
Bittium sp.
5
Proclava sp.
2
Calyptraea tubura Otuka
I
Erosaria sp.
48
Euspira meisensis (Makiyama)I
Pygmaeorota sp.
I
Echinophoria (Shichiheia) sp.
I
Bedevina sp.
I
Boreotrophon sp.
2
Nebularia sp.
19
Siphonalia sp. nov.
2
Chrysame sp.
2
Paradrillia sp.
Nipponaphera sp. nov.
14
29
Pugilina (Hemifusus) sazanami (Kanehara)
Reticunassa simizui (Otuka)
I
Zeuxis minoensis Itoigawa
294
Total of individuals
4399
Table 4.

6 14

Eiji Taguchi

5b

b

Sa

907.

Miocene Vepricardium

muddy bottom fauna in the inner sublittoralzone jUdging from the mode of occurrence,lithofacies and faunal constituents mentioned
above.

Vepricardium(Vepricardium)okamotoialso occurs in mudstones of the Yoshino
Formation at Mino and at Tanaka both in
Shoo-cho. Therefore, it is considered that
this new species had adapted to muddy substratum. On the contrary, "Vasticardium "ogurai (Otuka), a representative and widespread Miocene cardiid of Japan, seems to beadapted to a sandy bottom (Otuka, 1938,
Shuto, 1960, Masuda, 1966, Itoigawa andNishikawa, 1976, Itoigawa et al. , 1981 , Nakagawa and Takeyama, 1985, Okamoto et
al ., 1986, Ueda, 1986 etc.).
In the Miocene of Japan , tropical molluscs
are not well-known, hence it is noticeable

Figure 7.

615that some tropical genera are included inJapanese Middle Miocene molluscan fauna(Otuka, 1938, Oyama, 1950, Tsuda, 1959,
Itoigawa, 1960, Itoigawa et al. , 1981 , Matsuoka, 1979, Taguchi, \98\, 1983a). They are as
follows; /sognomon (s.s.), Batissa, Geloina,

Perna, Placuna, Maoricardium, Katelysia,
Novaculina, Apolymetis, Phyloda, Melanoides, Telescopium, Terebralia, Chicoreus(Rhizophorimurex), Labiostrombus, Globularia, Rimel/a, Volema and Pionoconus. The
living species of the genus Vepricardium such
as V. multispinosum, V. sinense and V.
asiaticum are distributed in the lower latitude
area as Taiwan (Formosa) to north Australia(Habe, 1977). Accordingly, Vepricardium(Vepricardium) okamotoi , sp. nov. probably
indicates tropical marine condition in the
Middle Miocene of Japan ranging from 16 toPrickles on posterial ribs of Vepricardium (s.s.) okam%i, sp. nov. (MFM20033)

X 3.

~ Figure 6-la - lOb.
Vepricardium (Vepricardium) okamolOi, sp. nov. la - b, lateral and apicalviews, holotype MFM20015; 2a - b, lateral and apical views, paratype MFM20025; 3a - b, lateral andapical views, paratype MFM20031 ; 4a-b, lateral and apical views, paratype MFM20016 ; Sa - b, lateraland apical views, paratype MFM20027 ; 6a - b, lateral and apical views, paratype MFM20022 ; 7, internalview of hinge area, paratype MFM20037, x 2; 8a - b, lateral and apical views, paratype MFM 20033; 9a b, lateral and apical views, paratype MFM 20017; lOa - lOb, lateral and apical views, paratype MFM20034.
All figures in natural size, unless other wise stated.

Eiji Taguchi

616

abstract)

15 Ma.
Acknowledgments

I am deeply indebted to Prof. Junji Itoigawa of Department of Earth Sciences, Faculty of Science and Prof. Hiroshi Shibata of
Department of Geology, College of General
Education, Nagoya University for their fruitful discussion and critical reading of the typescript. I wish to express my special thanks to
Prof. Kazuo Okamoto of Geological Laboratory, Faculty of School Education, Hiroshima University for his cordinal guidanceand encouragement and to Dr. Akihiko Matsukuma of National Science Museum for his
offering the literatures. My sincere gratitude
is due to Messrs. Tadao Osafune and Atsuyoshi Obayashi who provided me thesignificant specimens, and to Mr. Isao Nishikawa for his permission to study the wellpreserved specimens of "Vasticardium" ogurai collected by him.
References cited
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abstract)- - and Matsukuma A., 1971 : Mensuration of fossils and statistics - Analysis of allometry andvariation -. Ibid., vol. 10, no. 3, p. 135-160.

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abstract)
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Oyama, K., 1950: Studies of fossil molluscan
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Shuto, T., 1960: Cardiids from the Miyazaki Group(Palaeontological study of the Miyazaki GroupVII). Trans. Proc. Palaeont. Soc. Japan, N.S.,
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Taguchi, E., 1981: GeloinajTelescopium bearing
molluscan assemblages from the Katsuta Group,
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Miocene Vepricardium

brackish faunal zonation in the Miocen~ ofJapan. Bull. Mizunami Fossil Mus., no. 8, p. 720, pis. 2-4.
- - , 1983a: New Middle Miocene mollusca fromthe Katsuta Group at Shinden, Tsuyama City,
Okayama Prefecture, southwest Japan. Part 1.
Description of Perna oyamai, sp. nov. and its
paleoecology. Jour. Sci., Hiroshima Univ., Ser.
C, vol. 8, no. 2, p. 95-102, pis. 8-9.
- - , 1983b: New Middle Miocene mollusca fromthe Katsuta Group at Shinden, Tsuyama City,
Okayama Prefecture, southwest Japan. Part 2.

617

Description of Nipponarca japonica and Tellinella osafunei. Bull. Mizunami Fossil Mus., no.
10, p. 23-28, pI. 1.
Tsuda, K., 1959: New Miocene molluscs from theKurosedani Formation in Toyama Prefecture,
Japan. Jour. Fac. Sci., Niigata Univ., Ser. 2,
vol. 3, no. 2, p. 67-110, pis. 1-7.
Ueda, T., 1986: The Miocene Bihoku Group and its
molluscan assemblages in the Shobara district,
Hiroshima Prefecture, west Japan. Earth Science (Chikyu-Kagaku), vol. 40, no. 6, p.437448. (in Japanese with English abstract)

Mino ~!!!T, Niida ~ Hl, Okayama IlUl W, Tanaka Hl9=t, Takakura ~;@", Tsuyama ¥t W,
Toyokuda :a~Hl, Shoo-cho /m:9cIBJ, Yoshino "E'!!!T.

f!!fi¥i B*llUlwJ,!i!;O)9=t~m/mHlII~:lJ' I? 0) Vepricardium O)-~:f'm: f!9"i¥i B*0) IlUlwJ,!i!;/m
HlII~"E'!!!T1I (9=t:M9=t~m) O)tJt!6:lJ'I?, Vepricardium ~::'ffl,\ill;i'7.>~,*i*~,-tfJv:f:r1 :lJ;9fi~~~:f'm, Vepricardium (Vepricardium) okamotoi C L -c~Jfil(: L, -t:-O)3:jZ:lf:;J;f:§x;jij\(;nt.:o*a-~W L t-:.o .:. O):f'mli, gE:!7\:, !6;f:§:to J: lf~ff:f'm:lJ' I?~UWii' 7.>~.L-C:to', ~~O).*.~a-m~i'7.>-m.c~~~n7.>oc., J:$t:li;rtlH*O)iJElit~::.
HlC~~

Trans. Proc. Palaeont. Soc. Japan, N.S., No. 160, pp. 618-630, 5 Figs., December 30, 1990

908. AN INTERESTING PACHYDISCID AMMONITE FROMHOKKAIDO, WITH REMARKS ON RELEVANT TAXA*(STUDIES OF CRETACEOUS AMMONITES FROM HOKKAIDO-LXVII)T A TSURO MATSUMOTO
c/o Department of Earth and Planetary Sciences,
Kyushu University 33, Fukuoka 812

Abstract. A peculiar ammonite recently acquired by Masatoshi Kera from theConiacian rock of the Masago-zawa in the Yubari Mountains, central Hokkaido, is described as a new species. It may represent the earliest species of Eupachydiscus Spath, 1922,
retaining some features which characterize certain species of Tongoboryceras Housa, 1967.
In this connexion Tongoboryceras is redefined so that it may include comprehensively more
species. Also Menabonites Housa, 1967 is reviewed with a proposal to include it in
Pseudojacobites Spath, 1922 in a revised sense. In the available material there is no
significant difference of size, i.e. a microconch versus macroconch relationship, between bior trituberculate species of Pseudojacobites and 'normal' pachydiscid species of Tongoboryceras, although the two genera are closely allied to each other.
Key words.
cus. Coniacian.

Lewesiceras. Tongoboryceras. Menabonites. Pseudojacobites. Eupachydis-

Introduction

Notes on some genera of the family
Pachydiscidae Spath, 1922

Masatoshi Kera, a friend of mine in Hokkaido, informed me that he acquired in October 1988 an ammonite which is unfamiliar tohim from a locality in the Yubari Mountainsof central Hokkaido. It was sent to me for apalaeontological study. In this paper I
describe it as a new species of Eupachydiscus.
It shows, however, peculiar characters and isolder than typical species of the genus in the
Santonian and Lower Campanian of Japan.
In connexion with this identification, I
reexamine some of the Turonian and Coniacian species which were described underLewesiceras, Tongoboryceras. Menabonites,
and Pseudojacobites, giving remarks on thesegenera.

I thought that the taxonomy at generic levelof this family was satisfactory. When I described some species from the Turonian andConiacian of Hokkaido (Matsumoto, 1979), I
was sorry to have made no mention of the twogenera established by Housa (1967). In thispaper I should give my remarks on them.
Genus Tongoboryceras Housa, 1967

Type species. - Lewesiceras tongoboryense
Collignon, 1952 (see Collignon, 1955, p.25,
pI. 2, fig. 3; also 1965, p. 33, pI. 428, fig. 1772)by original designation (Housa, 1967, p.41).
Remarks.- This genus has been acknowledged by Wright (1979, p. 316) and Kennedy(1984, p. 34). Beside the type species fromthe Coniacian of Madagascar, T. rhodanicum(Roman et Mazeran) (1913, p. 18, pI. 1, fig. 10'Received November 20. 1989; revised manuscript
accepted September 30, 1990
618

908.

A pachydiscid ammonite

under Pachydiscus) (Wright, 1979, p. 316, pI.
6, fig. 1), from the Upper Turonian of Franceand England, is a well known species of thisgenus.
The species called Lewesiceras satoi Matsumoto (1979, p. 34, text-fig. 3, pI. 5, fig. 1), fromthe Turonian of Hokkaido, is now regarded
as an example of Tongoboryceras, because it
is fundamentally similar to T. rhodanicum.
The former has less depressed whorls, more
numerous and finer ribs and stronger umbilical tubercles as compared with the latter, but
the difference is by no means great, being thatof allied but separate species of the same
genus.
Lewesiceras kawashitai Matsumoto (1979,
p. 32, text-fig. 2; pI. 4, fig. 1), from theConiacian of Hokkaido, should also be transferred to this genus, because its suture is quite
similar to that of T. rhodanicum and T. satoi,
being more complex than that of Lewesiceras.
It represents a subgroup of Tongoboryceras
which has much depressed whorls with rather
coronate or reniform section, narrow but
raised ribs and fairly strong tubercles. Someone may require a subgeneric separation forthis subgroup, but the type species (T. tongoboryense) itself has considerably depressed
whorls. Lewesiceras elmii Collignon (1965,
p. 36, pI. 429, figs. 1777-1779), from theConiacian of Madagascar, shows an intermediate value of BjH between T. tongoboryense
Table 1.
Speciesand T. kawashitai (Table 1), being muchgreater than that of typical species ofLewesiceras. It is probably referred to Tongoboryceras, although Collignon did notdescribe precisely its suture.
In the generic diagnosis of Tongoboryceras,
Housa took account of the weakness ofumbilical tubercles. Such a character may
be observable in some particular species, butsome other species of this genus have tubercles of moderate intensity (e.g. T. rhodanicum
in late growth-stage and T. satoi) and stillothers have prominent tubercles (e.g. T. elmii
and T. kawashitai). Generally the ribs andtubercles may look weak, if an internal mould
alone is dealt with.
On the ground of above observations, I
should properly redefine Tongoboryceras asfollows:
Generic diagnosis of Tongoboryceras.Shell of moderate size, so far as known;
involution moderate; umbilicus of moderate
width to fairly narrow. Whorls more or lessbroader than high, with BjH a little morethan 1.0 to somewhat below 2.0, subrounded
to reniform in section.
Ribs of unequal length and strength.
Major ribs with tubercles of various intensity
at or outside the subrounded umbilical edge,
disposed at fairly wide intervals and some ofthem accompanied with a periodic constriction. One to several minor ribs of unequal

Measurements (in mm) of selected species of Tongoboryceras.

SpecimenT. /ongoboryense, HT*HT**
T. rhodanicum, Wr.**
T. rhodanicum,

T. satoi,
T. sa/oi,
T. kawashitai,
T. elmii,

619

B/H

H/h

MR:VR

38 (.64)

1.41

1.13

75 (1) -19 (,25) 33 (.44) -46 (.60)

1.39

1.43

6.5: 17+a
4: 19
5: 19

0

59 (I)

UH

18 (.31) 27 (.46)

B

94 (1) -29 (.30) 38 (.40) -49 (.52)

1.29

1.41

124 (1)40 (.32) 52 (.42) -61 (.48)

1.17

1.62

5: 20

HT (-180')HT87 (1)

35
30 (.34) 32 (.37)

44.5
58 (.67)

1.27
1.81

1.28

5: 21
7: 22

HT*

67 (1)

20 (.30) 28 (.42)

48 (.73)

1.75

1.47

6: 18

HT

D=diameter, U=width of umbilicus. H=whorl-height, B=whorl-breadth, h=whorl-height 180' prior
to H, MR : VR = number of major ribs: that of ventral ribs in a half whorl; HT = holotype; Wr. =Wright, 1979, pI. 6 fig. I ; * cited from original papers (Collignon, 1955, 1965); ** measured on
photos; no mark = measured on actual specimens by myself.

620

Tatsuro Matsumoto

length intercalated on each interspace of the
major ribs; some of them may branch fromthe latter. Ribs nearly straight or gently
concave or somewhat flexuous on the flank,with more or less forward curve at theventrolateral shoulder, crossing the venterwith gentle or moderate convexity.
Sutures of the pachydiscid pattern, withtrifid Land U2, bifid lateral saddles (ElL, LI
U2 and inside U2), and abruptly descending
auxiliaries. In late growth-stages the elements are fairly deeply and finely incised; thestems of lateral saddles much narrowed andthose of Land U2 deeper than broad andmoderately (but not much) narrowed.
In general the sutures of Tongoboryceras(e.g. Collignon, 1955, pI. 2, fig. 3 for T. tongoboryense; Wright, 1979, pI. 6, fig. 1 for T.
rhodanicum; Matsumoto, 1979, text-figs. 2, 3
for T. kawashitai and T. satoi) are more
complex with narrower elements than those of
typical Lewesiceras (e.g. Wright and Kennedy, 1981, text-fig.12 for L. peramplus;
Matsumoto, 1979, fig. 1 for L. mantelli [='sharpei'] ), but less complex and have lessnarrowed stems of elements than those of
Anapachydiscus (e.g. Yabe and Shimizu,
1921, pI. 9. fig. 2 and pI. 8, fig. 2 for A.fascicostatus) and Pachydiscus in the correct
sense (e.g. Grossouvre, 1894, fig. 80 for P.
neubergicus).
Genera Pseudojacobites Spath, 1922
and Menabonites Housa, 1967

Type species of Pseudojacobites.-Pachydiscus farmeryi Crick, 1910 by original designation (Spath, 1922, p. 121).
Type species of Menabonites. - Pachydiscus anapadensis Kossmat, 1898 by original
designation (Housa, 1967, p.41).
Remarks.-Ps.farmeryi (Crick) (1910, p.
345, pI. 27, figs. I, 2), from the Upper Turonian Chalk Rock of England, has been
amply redescribed by Wright (1979, p.313,
fig. 2; pI. 4, fig. 5; pI. 5, fig. 1 ; pI. 6, figs. 2,3), who regarded Pseudopuzosia marlowensis(Noble, 1911) (p.398, text-figs. 1, 2) as its

Figure 1. Pseudojacobites anapadensis (Kossmat). Lateral (A), rear (8) and frontal (C) views of
the lectotype, GSI. 260. Arrow: last suture. Bar: 10 mm. (T.M. de/in.)

908.

A pachydiscid ammonite

Figure 2. Psuedojacobites rotalinus (Stoliczka).
GSI. 154. Bar: 10 mm. (T.M. delin.)synonym. I once investigated the holotypes
and other examples of the two nominal
species and thought that Pseudopuzosia may
be a smoothing offshoot from Lewesiceras(see Matsumoto, 1979, p.37, 42). Incidentally, Pseudopuzosia sp. reported by Birkelund (1973, p.141, fig. 10; pI. 12, fig. 1)
from Sardal on the west coast of Sweden is, inmy present opinion, Lewesiceras sp., becauseof its broad and minutely indented lobes andsaddles of the suture, less depressed whorl anddistinct tubercles and ribs in the preserved
middle-aged part. It is not an example of
Pseudojacobites in a revised sense. Wright(1979 p.312) has already referred it to L.
woodsi Wright.
Also I examined in the Geological Surveyof India (Calcutta) the two syntypes of Pachydiscus anapadensis Kossmat (1898, p. 90)(= Ammonite peramplus Mantell of Stoliczka, 1865, p. 130, pI. 65, figs. 1, 2), from the
Trichinopoly Group of India, of which thelarger one, GSI 260 (Fig. 1 of this paper) is
here designated as the lectotype. In comparison with them, I examined also the holotype,

621

Lateral (A) and rear (8) views of the holotype,

GSI 154, of Ammonites rotalinus Stoliczka(1864, p.65, pI. 34, fig. 2) (Kossmat, 1898, p.
91, pI. 14, fig. 3 under Pachydiscus) (Fig. 2 ofthis paper). The latter species was the typespecies of Rotalinites Shimizu, 1935, whichshould be a synonym of Pseudojacobites (seeWright and Matsumoto, 1954, p. 124).
The lectotype of P. anapadensis looks fairly well preserved but is incomplete in showing only an earlier part (about 90°) of the
body chamber. In addition to the weak andsmall (i.e. incipient) ventrolateral bulges inthe septate part of the outer whorl, more
distinct ventrolateral nodes appear on theearly part of the body chamber. The venterof this part of the body chamber is not evenly
rounded but has a blunt summit (contrary to
Stoliczka's too much broadened illustration)and the ribs are markedly projected on theventer as those of P. rotalinus. These features suggest that the mid-ventral tubercles
may appear in the late part of the adult bodychamber.
In fact, Lewesiceras masiaposense Collignon, 1952, (see 1955, p.21, pI. 1, fig. 1),

Tatsuro Matsumoto

622
Table 2.

SpeciesSpecimenHT·
P. /armeryi,Wr.
1979 0 •P. /armeryi,
P. masiaposensis, HT· (c)P. masiaposensis, HT* (ic)HT (ic)HT (-160')
P. anapadensis, LT (ic)
P. anapadensis, LT (c)P. rOlalinus,
P. rotalinus,

Measurements (in mm) of selected species of Pseudojacobites.
DU

91.5 (I)-73
96.0 (I)(I)

H

37.5 (.41)
35 (.38)(.36) -28.5 (.39)

-26

B

BjH

Hjh

MR:VR

27.5 (sec.

compr.)

1.5

5: --38 (.52)
47.0 (.49)

1.33

-1.5

5 : 15

1.31

1.5

5: 16

36.0 (.38)

36.0 (.38)

43.0 (.45)

1.19

89.5 (I)74.0 (I)32.5 (.36)

32.5 (.36)

37.0 (.41)

1.14

1.33

8: 12

26.5 (.36)

26.0 (.35)

29.5 (.40)

1.13

1.21

6: 12

93.0 (I)28.5 (.31)

37.0 (.40)

50.0 (.54)

1.35

1.35

5: 20

94.0 (I)29.0 (.31)

37.5 (.40)

54.5 (.58)

1.45

1.36

5: 20

Abbreviated letters as for Table I. - = approximate, ic= intercostal, c=costal• after Crick, 1910 or Collignon, 1955; Wr. 1979=Wright, 1979, pl. 5, fig. I; •• measured on photos; no mark =measured on actual specimen by myself.

which was listed by Housa as a species of
Men abonites, has trituberculate ventral partin the late growth-stage. Some other species
in his list of Menabonites have no or incomplete body chamber.
The whorl is much broader than high in'Men abon ites , anapadensis, but the ratio of
BjH may vary between species. For example, BjH of that species is indeed greater thanthat of Ps. rotalinus but not much different
from that of Ps. farmeryi (see Table 2).
'M.' anapadensis looks to have denser,
more numerous ribs than those of Ps.
rotalinus, but again there is a considerable
extent of variation among species in the rib
density and also in the proportion between
the number of major ribs with umbilicaltubercles and that of all the ribs on the outerpart. This is similar to the situation in various species of Tongoboryceras.
There is no significant difference in thepattern and complexity of sutures between
Menabonites and Pseudojacobites. For
instance, compare the suture of 'M.' anapadensis (Kossmat, 1898, pI. 14, fig. 2) withthat of Ps. rotalinus (op. cit., pI. 14, fig. 3b) or
Ps. farmeryi (see Wright, 1979, text-fig. 2; pI.
4, fig. 5; pI. 5, fig. I).
On the ground of the above observations,
Menabonites Housa, 1967 is not sufficiently
distinct at generic level from Pseudojacobites
Spath, 1922. The latter can be properly

defined so that it includes the species whichwere assigned to Menabonites by previous
authors.
Generic diagnosis of Pseudojacobites.Shell of moderate size, about 100 to 150 mm
in diameter at full-grown stage. Whorls ofmoderate involution, encircling moderately
wide or fairly narrow umbilicus, more or lessbroader than high, and reniform or subrounded in cross-section.
Ribs of unequal length and strength.
Major ribs provided with tubercles at subrounded umbilical border or shifted outward
near the mid-flank. Minor ribs intercalated
or indistinctly branch from the longer ones.
All the ribs curved forward at about therounded ventrolateral shoulder and more orless projected on the venter. Periodic constrictions in front of some major ribs more orless distinct. Sooner or later in ontogenetic
development there appear strong or weakventrolateral tubercles on most of major andsome of minor ribs. In addition to them,single or double mid-ventral tubercles occur
in some species.
Sutures quite similar to those of
Tongoboryceras.
Problem of dimorphism

Even if the generic diagnosis is given foreach of Tongoboryceras and Pseudojacobites

908.

A pachydiscid ammonite

as described above, there remains the problem
of dimorphism about them.
I have already suggested, but not concluded, that in the family Pachydiscidae the'bituberculate' (or 'trituberculate') and 'normal' forms might be considered as representing sexual dimorphism (Matsumoto, 1955, p.
155; 1979, p. 42), because the former is often
smaller than the latter and species of bothforms sometimes have common characters toa certain stage in ontogenetic development.
At that date, however, I was inclined to interpret those small bituberculate genera as
neotenous derivatives of 'normal' pachydiscids. Recently Kennedy (1986, p. 32) has
given a general review on this problem.
When the evidence is enough for the interpretation of sexual dimorphism, he dares toconclude the nomenclatorial sorting (dimorphic pairs regarded as synonyms) and in thecases where uncertainty exists he maintains a
conservative approach. I would agree with
Kennedy in principle, but the judgment
whether the evidence is sufficient or not mayvary between authors.
Now, how should I do about Pseudojacobites and Tongoboryceras? They havegenerally common characters and the maindifference is the presence of ventrolateral (andin some case also ventral) tubercles in theformer.
Some of the species of Tongoboryceras
were established on incompletely preserved
specimens. For instance, the holotype of T.
tongoboryense is wholly septate (see Collignon, 1955, pI. 2, fig. 3) and the diameter of
the adult shell of this species is not known.
Collignon (1955, p.26) mentioned that thisholotype is comparable in size approximately
with the middle aged specimen of T. beantalyense (Collignon). Incidentally, Housa(1967) referred Lewesiceras beantalyense to
his Men abonites , but Collignon did notdescribe the presence of ventrolateral tubercles. The holotype of the latter species was
explained as adult by Collignon (1955, pI. 2,
fig. 2) but is 72 mm in diameter and wholly623

septate. A larger example in his later publication (Collignon, 1965, pI. 427, fig. 1771) is
100 mm in diameter at the end of the preserved part of the body chamber which occupies
a half of the outer whorl. This is nearly thesame size as the holotype of Pseudojacobites
farmeryi and that of P. anapadensis.
As far as the available material is concerned, no significant difference in size isrecognized between Tongoboryceras andPseudojacobites (see Tables 1,2). At specificlevel well comparable couterparts are notfound in the two genera. In other words, it
is difficult to point out any possible candidateof a pair of rrticroconch and macroconch in
the hitherto described species of Pseudojacobites and Tongoboryceras.
Pachydiscoides Spath, 1922, with Sonneralia janeti de Grossouvre, 1894 (see Kennedy,
1984, p. 37, pI. 13, figs. 1-4) as the typespecies, is a small to medium sized but strongly ornamented pachydiscid genus ofConiacian to Santonian ages. Nearly contemporary Tuberodiscoides Collignon, 1966,
with T. termierorum Collignon 1966 (p.31,
pI. 468, figs. 1910-1912) as the type species, isof similar size and allied to Pachydiscoides
but has ventrolateral and siphonal tubercles.
They might be regarded as microconchs but
no counterpart macroconchs are known.
On the ground of the above observations, it
is still difficult to lead a general conclusion as
to the problem of dimorphism in the Pachydiscidae, especially with regard to earlier
members of the family.

Description of a new species
Genus Eupachydiscus Spath, 1922

Type species . - Ammonites isculensis
Redtenbacher, 1873 by original designation(Spath, 1922, p. 124).
Remarks. - A new species described below
is, in my opinion, interesting to the problemof the ancestry of the genus Eupachydiscus.
Spath (1922, p. 124) thought of Nowakites

Tatsuro Matsumoto

624

Spath, 1922 as ancestral to Eupachydiscus,but I regarded it as ancestral to Canadoceras
Spath, 1922 (see Matsumoto, 1979, p.37, fig.
5), although I did not discuss the line ofdescent at specific level. Housa (1967, p. 44)
presumed Lewesiceras plica tum Housa, 1967
as a possible origin of Eupachydiscus, thoughwith a query.
The suture of Eupachydiscus is much more
complex than that of Lewesiceras and closer
to that of Tongoboryceras. With respect tothe shell-form and ornamentation, the young
to middle aged whorls of some species ofEupachydiscus, e.g. E. haradai (Jimbo, 1894)(see Matsumoto, 1954, p. 281, figs. 14-17; pI.
9, figs. 1-3; pI. 10, figs. 1-3), are fairly similar
to the middle to late whorls of certain speciesof Tongoboryceras, such as T. satoi (Matsumoto) (1979, p. 35, fig. 3; pI. 5, fig. 1). An
ammonite rarely found by M. Kera from theConiacian of Hokkaido deserves description
in this respct.

Eupachydiscus keramasatoshii, sp. nov.
Figures 3,4

Holotype.-No.482 of Masatoshi Kera'sCollection, obtained on October 2, 1988 froma nodule loose in the upper reaches of a
stream called the Masago-zawa, a tributary to
the Shuparo, i.e. the upper course of the River
Yubari in the Yubari Mountains, central
Hokkaido. It is to be kept in the Museum ofMikasa City.
Description. - Adult shell slightly exceeding
medium size. Whorl expands with rather
low rate and its degree of involution moderate (i.e. about a half). Umbilicus of moderate width encircled by steep and fairly highwall; umbilical shoulder subrounded, but
for subangular edge of the major ribs in thelate growth-stage.
Whorl of the septate stage fairly depressed,with inflated flanks and broadly rounded
venter. In the adult body chamber, B/H
decreasing to a little below 1.2, with moderately rounded venter.
The exposed part (i.e. inner flank) of thevery early whorls looks smooth. The umbilical bullae begin to appear at the point 2 + 3/
4 whorls adaptically from the preserved end,
i.e. at D = about 20 mm (inferred); very weakin the early half whorl, becoming somewhat
more distinct at the umbilical shoulder in thenext half whorl; altogether 9 to a whorl.
In the next stage, that is from the point 1+
3/4 whorls adaptically from the preserved end
to the early part of the outer whorl (inferred
D=from 40 mm to 80 mm) and can be called
the middle stage, major ribs occur at each 50°
or 60° and are thick, strong, fold like andprovided with prominent tubercles at theumbilical border, foming a gently concave
curve on the flank and a broad convexity
across the venter. Some of them may accompany a constriction. There are several minor
ribs of unequal length on each interspace ofmajor ones. One of them may be longer thanothers and nearly reaches the umbilical border where a weak bulla may be formed; someof shorter ones branch from the longer one
and others are intercalated. All the ribs
gently concave or slightly flexuous on theflank and cross the venter with a gently forward convexity.
In the whorl for about 260° of the adultstage, from the last portion (about 50°) of thephragmocone to the end of the body chamber(which occupies 210°), the major ribs muchstrengthen to nearly rectiradiate bar likeflares, crossing the venter with increasingheight, whereas minor ribs on the interspaceof major ones become fewer, narrower andmore widely separated, crossing the venter
nearly straightly. Constrictions in front ofsome major ribs persist to the early part of the
body chamber. The tubercles at the umbili-~
Figure 3. Eupachydiscus keramasatoshii, sp. nov. Lateral (A), frontal (B) and back (C) views of theholotype, collected by M. Kera from the Masago-zawa. Bar: 10 mm. (Photos by courtesy of Dr. M. Noda)

908.

A pachydiscid ammonite

625

Tatsuro Matsumoto

626...... ,----, "
II'

'"

"""""
,

\

"
"

\

",

II

\\

\\

\

I

'

, I)

I

:

/,

r"" '"

,
I

.I

,r

,

\

I

'-......, "

'\ \

)1
II

/1
,

,"/

,'~

' ...... ----_ ...... ... ,,/Figure 4. Eupachydiscus keramasatoshii, sp.
Whorl-section of the ho!otype. Bar: 10 mm.
(T.M. de/in.)nov.

cal edge of major ribs are prominent andbullate.
Lobes and saddles of the suture in the late
growth-stage are deeper or higher than broad,with narrowed stems and branches of lateralsaddles, by deep and fine incisions.
Dimensions.-See Table 3.
Observations. - This specimen is nearlycomplete in showing the body chamber up to
the peristome, provided that the minor rib infront of the strongly flared, last major ribs isregarded as an apertural flange. On thisassumption the body chamber is 210°. The
shell diameter is 127 mm at the preserved end(i.e. presumed peristome) and 135 mm at thelast major rib. Conventionally I define thesize of ammonite with diameter from 75 mm

to 125 mm as moderate (see Matsumoto, 1954,
p. 246; 1988, p. 4). This ammonite slightly
exceeds the defined moderate size, being near
the lowest limit of the next size, i.e. fairly
large (0 over 125 mm up to 250 mm).
This specimen is embedded and fused withthe rock matrix on its right side for a taphonomical reason, but the venter of its outerwhorl is fairly well, if not completely, exposed. Therefore the whorl-breadth (B) is
calculated from its measured half.
The specimen is covered with altered shelly
layers for the major part, except for the summits of some ribs, peaks of tubercles and otherminor portions. For this reason the majorribs and tubercles may generally look pronounced, as compared with the case of internal mould, whereas the suture is hardly traced
as a continuous line but observable here andthere.
The ornamentation in the adult whorl ischaracteristic. Of the six major ribs, the firsttwo are fold like and essentially similar to but
somewhat stronger than those of the preceding stage, weakly concave forward on theflank and very gently convex on the venter;the last three on the later half of the bodychamber are much elevated and can be called
flares which are almost vertical on the rearside and steeply inclined to the anterior; thethird one shows a transitional feature fromthe fold like earlier ones to the bar like later
ones. There is no minor rib on the interspace between the last two major ribs, except
for very feeble lirae; there are only two
minor ribs in the next preceding broad interspace. Several minor ribs on still earlier
three major interspaces are somewhat irregular in length, breadth, spacing and curvature(see Figure 3). In the gross the irregularities
may express transitional features from theminor ribbing of the middle growth stage tothat of the late part of the adult stage.
Comparison and discussion.- This specimen is similar in the characters of its middle
growth-stage to the holotype and subsequently illustrated specimens of Tongoboryceras

A pachydiscid ammonite

908.
Table 3.

Measuremests (in mm) of E. keramasatoshii and selected examples of Eupachydiscus.

SpeciesSpeciment>lHT, Last rib (c)

135

(I)

47 (.35)

HT, Last -10' (ic)

124

(I)

46 (.37)

HT, Last -90' (ic)115.5 (1)100 (I)

~

~

:i!
I:l
I:l

HT, Last -180' (c);:,-HT, Last -190' (ic)HT, Last -270' (c)

'"

~

:::::

627

D

H

B

49

(.38) 5842(.34) 4939 (.34)41.5 (.36) 49

33 (.33)42U(.42) 53

MR:VR

B/H

H/h

(.43)

1.18

1.26

4: 13

(.39)

1.17

1.17

4: 14

(.42)

1.18

1.19

(.53)

3: 16
4: 18

37

47

1.26
1.27

34

44

1.29

(.40)

0.93

1.45

7: 18

1.15

1.20

6: 14

1.09

1.19
1.29

7: 17
6: 15

1.40

6: 16

1.45

7: II

E. isculensis,

HP (c)

185(15

50 (.27)80(.43) 74

E. isculensis,
E. haradai,
E. haradai,
E. haradai,
E. teshioensis,

Imm.*

78

20 (.26)

36

(.46)

LT

120

(I)
(I)

32 (.27)

48

T.M.

198

(I)

51 (.26)

80

Usher

WI

23 (.23)

44

HT

252

(I)
(I)

(.40) 55 (.46)(.40) 87 (.44)(.44) 50.5 (.50)

67 (.27) 108(.43) 123

(.49)

1.15
1.14

E. roederi,

HT (ic)*150(I)47 (.31)(.41 ) 74

(.49)

1.21

61

3: 18
4:-

7: 21

28

Abbreviated letters or symbols as for Tables 1,2. LT = lectotype; Imm. = Immel et al., 1982, pI. 8, fig.
2*; T.M.=Matsumoto, 1954, pI. 24, fig. 2; Usher=Usher, 1952, pI. 14.

rhodanicum from the Upper Turonian ofFrance and England (ioc. cit.), but the majorribs are coarser, disposed at wider intervals
and provided with stronger umbilical tubercles in the former than in the latter. In otherwords, the difference in the coarseness or
intensity between major and minor ribs in the
middle aged whorl of this species is greaterthan that in the middle to late whorl of T.
rhodanicum. As regards T. rhodanicum, thefull length of the adult body chamber is notpreserved in the hitherto described specimens.
In the outer whorl of a fine example from the
Chalk Rock (Wright, 1979, pI. 6, fig. I) only
the beginning of the body chamber is preserved. The ribs seem to strengthen graduallyfrom the late part of the phragmocone, andthe sudden appearance of prominent majorribs and the contrasted reduction of minor
ribs as seen on the body chamber ofM. Kera's
specimen do not likely occur in that species.
In the typical species of Eupachydiscus,
such as E. isculensis and E. haradai, themajor tuberculate ribs and minor intercalated
or branching ribs are both strengthen gradually and fold like instead of bar like. E.
haradai, with which Pachydiscus perplicatus
Whiteaves, 1903 (see Usher, 1952) is a syno-

nym (see Matsumoto, 1959, p. 33), may be oneof the best studied species of this genus. It
shows the ontogenetic changes from a muchdepressed, reniform young whorl with fine
and weak ornaments, via middle aged whorlwith moderate characters, to the lessdepressed, more rounded whorl with strong
ornaments of typical Eupachydiscus type,which may be called the adolescent or earlysubstage of the adult stage. In the whorl ofstill later stage strong, nearly rectiradiate
major ribs predominate, with few or no intercalated minor ones. This is exemplified by
the outer whorl (though incomplete) of GK.
H3405 (Matsumoto, 1954, pI. 9, fig. I), whereas the lectotype of E. haradai is wholly
septate. Anyhow, the adult shell of thatspecies is much larger than the Kera's specimen and its major ribs are thick and fold like
instead of bar like flared ones of the latter.
Incidentally, the specimens from theConiacian and Lower Santonian of Austria
described under E. isculensis are all small or
medium-sized (Herm et al., 1979; Immel etal., 1982), although they preserve the bodychamber at least partly. They are fairly similar to such species as T. satoi mentioned
above.

Tatsuro Matsumoto

628

Eupachydiscus roedereri (Collignon)(1938, p. 12, pI. 2, fig. 3; pI. 3, fig. 1 underCanadoceras; 1970, p.26, pI. 617, fig. 2302
under Hoepenites), from the Campanian ofMadagascar, has widely spaced, rather rectiradiate, bar-like major ribs, but this kind of
ribbing begins to develop from the earlier
growth-stage and persists for longer period
and the mode of spacing is more regular thanthe bar-like ribs of the M. Kera's specimen.
To sum up, M. Kera's specimen is so distinctive that a new species is established on it,
although it is solitary. This species retains
some characters which resemble those of certain species of Tongoboryceras but it does
show new characters, such as prominent
tubercles from middle growth stage andstrong major ribs on the adult body chamberwith decreasing BjH, which allow me to refer........ - .......

_. .-""
I

-

"N'"

....
t;i

r

N43"10'1000 m.

Figure 5. Map of the Masago-zawa (MZ), a
tributary to the River Shuparo (SP), indicating theammonite locality (Y5512) with a small solid circle.
Chain: the water shed with a peak of 695 m at themark of solid triangle. For the north western partsee fig. 86 in Matsumoto, 1988.

it to Eupachydiscus.
Occurrence.- The holotype was obtainedby M. Kera loose at loco Y5512 in the upper
reaches of the Masago-zawa, a branch of theRiver Shuparo (Figure 5). The stream runs
with some meandering along a V shaped
valley roughly in parallel to the trend of thestrata of mudstone with some interbeds ofsandstone. Inoceramus uwajimensis Yehara
occurs abundantly in several layers andnumerous nodules in the mudstone. Also
Didymotis akamatsui (Yehara) is found at a
nearby locality (Y5507) and Y. Kawashitaobtained a gigantic macroconch of Mesopuzosia yubarensis (limbo) at loco Y5518.
The described ammonite is certainly ofConiacian age, being an oldest example of
Eupachydiscus.
Acknowledgements. - I very much appreciate Mr. Masatoshi Kera's generosity to provide the ammonite of his collection for thisstudy. He kindly helped me, together withhis brother Mr. Yasuji Kera, in a field workin the upper reaches of the Masago-zawa.
Mr. Yoshitaro Kawashita, Dr. Seiichi Toshimitsu and Dr. Masayuki N oda also did
another field work with me in the same area,
although I failed to find more specimens of
the present species. Miss Akiko Murakami
assisted me in preparing the typescript.
References cited
Birkelund, T., 1973: A note on Pseudopuzosia from
Sardal. Bull. Geol. Soc. Denmark, vol. 22, p.
141-142, pI. 12.
Collignon, M. 1938: Ammonites Campaniennes et
Maestrichtiennes de l'Ouest et du Sud deMadagascar. Ann. Geol. Servo Mines, Madagascar, vol. 9, p. 1-65, pis. 1-9.
- - , 1952: Ammonites neocretacees du Menabe(Madagascar), II-Les Pachydiscidae. Trav. Bur.
Geol. Madagascar, Tananarive, vol. 41, 114 p.,
33 pis.
- - , 1955: Ditto (reprinted). Ann. Geol. Servo
Mines, Madagscar, vol. 21, 98 p., 28 pis.
- - , 1965: Atlas des fossiles caracteristique deMadagascar (Ammonites), fasc. 13 (Coniacien),908.

A pachydiscid ammonite

88 p., pIs. 414-454.
- - , 1966: Ditto, fasc. 14 (Santonien), 134 p., pIs.
455-513.
- - , 1970: Ditto, fasc.16 (Campanien moyen etsupi!rieur), 82 p., pIs. 607-639.
Crick, G.C., 1910: Note on two cephalopods fromthe Chalk of Lincolnshire. Geol. Mag., London, [5] vol. 7, p. 345-348, pI. 27.
Grossouvre, A. de, 1894: Recherches sur la Craie
supi!rieur. 2, Pali!ontologie. Les Ammonites
de la Craie supi!rieur. Mem. Serv. Carte Geol.
det. France, Paris (1893), 264 p., 39 pis.
Herm, D., Kauffman, E.G. and Wiedmann, J., 1979:
The age and depositional environment of the"Gosau" Group (Coniacian-Santonian), Brandenberg/Tirol, Austria. Mitt. Bayer. Staatsslg.
Palciont. Hist. Geol., vol. 19, p. 27-92, pis. 5-11.
Housa, V., 1967: Lewesiceras Spath (Pachydiscidae,
Ammonoidea) from the Turonian of Bohemia.
Sb. Geol. VM., Paleont., Praha, P-9, p.7-50,
pIs. 1-8.
Immel, H., Klinger, H.C. and Wiedmann, J., 1982:
Die Cephalopoden des Unteren Santon der
Gosau von Brandenberg Tirol, Osterreich.
Zitteliana, vol. 8, p. 3-32, pis. I-II.
Jimbo, K., 1894: Beitriige zur Kenntniss der Fauna
der Kreideformation von Hokkaido. Geol.
Palaeont. Abhandl. [N.F.], vol. 2, p.149-194,
pIs. 17-25.
Kennedy, W.J., 1984: Systematic palaeontology andstratigraphic distribuion of the ammonite faunasof the French Coniacian. Spec. Pap. Palaeont.,
London, no. 31, 160 p. (incl. 33 pis.).
- - , 1986: Campanian and Maastrichtian ammonites from northern Aquitaine, France. Ibid.,
no. 36, 145 p. (incl. 23 pIs.).
Kossmat, F., 1898: Untersuchungen Uber die
SUdindische Kreideformation. Dritter Teil,
Beitr. PalCiont. Geol. Ost.-Ung.,vol. II, p. 39-152,
pIs. 14-19.
Matsumoto, T., 1954: Selected Cretaceous leadingammonites in Hokkaido and Saghalien. In
Matsumoto, T. (ed.): The Cretaceous System in
the Japanese Islands p. 243- 313, pIs. 1-20 (1736). Japan Soc. Prom. Sci., Tokyo (for 1953).
- - , 1955: The bituberculate pachydiscids from
Hokkaido and Saghalien. Mem. Fac. Sci.,
Kyushu Univ., Ser. D, vol. 5, no. 3, p. 153-184,
pIs. 9-23.
- - , 1959: Upper Cretaceous ammonites of California, Part 2. Ibid., Ser. D, Spec. Vol., I, 172 p.,
41 pIs.
- - , 1979: Notes on Lewesiceras and Nowakites(pachydiscid ammonites) from the Cretaceous of
Hokkaido. Trans. Proc. Palaeont. Soc. Japan,

629

N.S., no. 113, p. 30-44, pis. 4-7.
- - , 1988: A monograph of the Puzosiidae (Ammonoidea) from the Cretaceous of Hokkaido.
Palaeont. Soc. Japan, Special Papers., no. 30,
179 p., 88 figs.
Noble, A.H., 1911: On a new species of Desmoceras
from the Chalk Rock of Buckinghamshire.
GeoL Mag., London, [5] vol. 8, p.398-400.
Redtenbacher, A., 1873: Die Cephalopoden Fauna
der Gosauschichten in den nord-osterlichen
Alpen. Abhandl. Geol. Reichsanst., vol. 5, p.
91-149, pIs. 166-171.
Roman, F. and Mazeran, P., 1913: Monographie
pali!ontologique de la faune du Turonien dubassin d'Uchaux et des ses di!pendances. Arch.
Mus. Hist. Nat. Lyon, vol. 12, no. 2, p. 1-137, pIs.
I-I I.
Shimizu, S., 1935: The Upper Cretaceous cephalopods of Japan, Part I. Jour. Shanghai
Sci. Inst., [2], vol. I, p. 159-226.
Spath, L.F., 1922: On the Senonian ammonite faunaof Pondoland. Trans. Roy. Soc. S. Afr., vol.
10, p. 113-147, pis. 5-9.
Stoliczka, F., 1864-65: The fossil Cephalopoda ofsouthern India. Ammonitidae with revision of
the Nautilidae etc. Mem. Geol. Surv. India,
Palaeont. Indica, vol. 3, nos. 2-5, p. 57-106, pis.
32-54 (1864); nos. 6-9, p.107-154, pis. 55-80(1865).
Usher, J.L., 1952: Ammonite faunas of the Upper
Cretaceous of Vancouver Island, British Columbia. Geol. Surv. Canada, Bull., 21, 182 p.,31
pIs., I map.
Whiteaves, J.F., 1903: On some additional fossils
from the Vancouver Cretaceous, with a revised
list of species therefrom. GeoL Surv. Canada,
Mesozoic Fossils, vol. I, pt. 5, p. 309-409, pis. 4051.
Wright, C.W., 1979: The ammonites of the English
Chalk Rock (Upper Turonian). Bull. Brit. Mus.
Nat. Hist. (Geol.), vol. 31, no. 4, p. 281-332 (incl.
pIs. 1-7).
- - and Kennedy, W.J., 1981 : The Ammonoidea of
the Plenus Marls and the Middle Chalk.
Monogr. Palaeontogr. Soc., London, 148 p., 32
pIs. (Publ. no. 560, part of vol. 134 for 1980).
- - and Matsumoto, T., 1954: Some doubtful
Cretaceous ammonite genera from Japan and
Saghalien. Mem. Fac. Sci. Kyushu Univ., Ser.
D, vol. 4, no. 2, p. 107-134, pIs. 7-8.
Yabe, H. and Shimizu, S., 1921: Notes on some
Cretaceous ammonites from Japan and California. Sci. Rep. Tohoku Imp. Univ., 2nd Ser.,vol. 5, p. 53-59, pIs. 8-9.

Tatsuro Matsumoto

630

Fukuoka mJlIT], Hokkaido ~t#a~, Masago-zawa
Shuparo -/.,. '/ . . ~ p. Yubari !;r~.

Ji?tPlR, Mikasa=~,~t#a~£ . . ~ ':I :f-T -I A!' f4O)~,*ib G 7 :/ ~ T l' r tJ: i? lH::.~:ilji,ftt;:.,,:>I,'-C 0)F.Jj' ~ :Pachydiscidae O)ji, v ""lvO):5H~Ht i t':5Ei' L- -C 1" tJ: 1,'0 Lewesiceras ft~~**-O)~~~iJ~$1iiJ.t < ~U~iJ~ml,' ~ 0) t;:.JlR5E-t G ~ ~ o q:t;f!jl!tt;:.$Iii~ < ~U~iJ;l* 1" ~ 0) ft Tongoboryceras t;:.}\.ht.:1]iJ;J: 1,'0 17UJ! L. satoi, L. kawashitai ft~~t;:.;§-to F.Jj'ji,ftO)~:l.nH;:.if
1" T. ji,0) ~O)5E~a-*,T[jl(JE L- t.:o liSJji,t;:.ibLG iJ~I£*~:JtIjt;:.7i-{)lUO)~, ftt;:. J: '? -C ft ~i? t;:.7i-OOq:t:9ct;:'~~iJ;ib G ~ 0) ft, Menabonites i t.:a Pseudojacobites ~ h -C I, 'ko M.
ji,O)F.Jj'ji,fta-~WL-, Ps. t;:. M. a-~~L-t.:fi'J~-e Ps. O):jl}5E~a-~P~ L-t.:o *f4tU"I,,-C

t.:

c.

c.

~~~7i-.K~ibG~O)a.DO)~O)J:~~~O)~~~~<, ~~~ha-~~=~c.m~-tG~M;59i< tJ:'?-CI,'Go L-iJ'L- T., Ps. jjIij~O)~~t;:'ft*~~O)~iJ;tJ:<, :%j".rr;;ftO)"Iff
17U ~ ~~t.: i? tJ:1, '0

T. rhodanicum ~ T. satoi 0)1£*~f§10)q:t. ~~ft Eupachydiscus haradai tJ:C:O)~·c.

q:t~ ibLG iJ;, ~~0)JV(;~liIHt*~-eiJ''':>~~iJ;59i{r. L-, ~~**- ~f,Utt;:.tJ: Go ~~m~
JEfljiJ~~t#a~!;r~O)Ji~YlRO) '::1 .::. 7 -/7:/(1. uwajimensis *)iJ' i?Wtdffi!.ft 7-.,. P .::. 7:/ 1:$£0) T. rhodanicum iJ'i?O)7.tJij:a-;t!!5E-e~, JV(;~~iJ;.."f:-hfic.·*~-etJ: <, iJ''':>~,~VJ:%Jl:a-7.f--tO)-e, ~ft E. keramasatoshii
L--C~1tL-t.:oto*j!~~c.

Trans. Proc. Palaeont. Soc. Japan, N.S., No. 160, pp. 631-640,4 Figs., December 30, 1990

909.

EARLY LIFE HISTORY OF TWO MIDDLE PLEISTOCENE
SPECIES OF LIMOPSIS (ARCOIDA: BIVALVIA)*
KAZUSHIGE TANABE
Geological Institute, University of Tokyo, Tokyo 113

Abstract. Early life history of two species of Limopsis, L. (Crenulilimopsis) oblonga(A. Adams) and L. (Limopsis) azumana Yokoyama is discussed on the basis of wellpreserved Middle Pleistocene juvenile specimens from the southwestern Kanto region, central
Japan. L. (C.) oblonga has a relatively large prodissoconch I (Pd I)(ca. 180}lm in length)
and a well-marked prodissoconch II (Pd II), suggesting lecithotrophic development with ashort pelagic stage. L. (L.) azumana, in contrast, probably underwent direct development
or ovoviviparity because of its unusually large prodissoconch (ca. 400}lm in length) without
Pd II stage. The two species exhibit a similar pattern in hinge development: the hinge inthe full-grown prodissoconchs is made of a long, uninterrupted series of Iigamental pits
(provinculum), and anterior and posterior cardinal teeth appear at the early dissoconch
stage, increasing their number as the shell grows. Predominance of minute shells at thefossil locality strongly suggests an extremely high juvenile mortality in the two species.
Key words.
Kanto Region.

Bivalvia, Limopsis, Early life history, Pleistocene, Ninomiya Group,

luscan larval shell morphology in paleobiological research, investigation on fossil
bivalves is quite limited (LaBarbera, 1974;
Lutz and Jablonski, 1978; Tanabe andZushi, 1988; Palmer, 1989), owing much to
the rare occurrence of juvenile specimens
including prodissoconchs in many fossil
bivalve assemblages.
In this paper, I describe the mode of occurrence and the morphological features of wellpreserved juvenile shells of two species ofLimopsis, L. (Crenulilimopsis) oblonga (A.
Adams) and L. (Limopsis) azumana Y 0koyama from the Middle Pleistocene
Ninomiya Group in southwestern Kanto
region, and discuss their implications forearly life history.

Introduction
The shells of bivalve molluscs consist of
two different portions, prodissoconch anddissoconch (Werner, 1939; Rees, 1950; Ockelmann, 1965). The prodissoconch is secreted before metamorphosis, and is clearly distinguished from the subsequent dissoconch by
the abrupt change in surface ornamentation at
the prodissoconch-dissoconch boundary (Jablonski and Lutz, 1980, 1983). Ontogenetic
studies of modern bivalve species by culture
methods have shown that the prodissoconchand early dissoconch provide considerable
information on the early life history of theorganisms (e.g. Thorson, 1936; Yoshida,
1953; Loosanoff and Davis, 1963; Chanley,
1965, 1966, 1969, 1970; LaBarbera and Chanley, 1970, 1971).
In spite of the potential usefulness of mol-

Materials and methods

Materials. - Middle Pleistocene marine
deposits of the Ninomiya Group (Otuka,"Received November 28, 1989; revised manuscript
accepted September 4, 1990
631

Kazushige Tanabe

632

INDEX MAP

SAGAMI

Figure 1.

BAY

Map of Ninomiya area, showing the fossil locality (X).

1929) are distributed in the Ohiso Hill area,
southwestern Kanto region. The middle
part of the group (Lower Shimoda Formation; Mori and Osada, 1979) yields abundantmolluscan fossils, and the molluscan assemblages of the formation were compared with
the Middle Pleistocene Naganuma fauna in
Yokohama area by previous authors (Yokoyama, 1926; Otuka, 1929; Mori and Osada,1979).
Juvenile shells of L. (Crenulilimopsis) obtonga and L. (Limopsis) azumana utilized
were collected from the fine sand beds in theupper part of the formation exposed at Mushikubo, about 2.5 km northeast from JR Ninomiya Station, together with many middle- tolarge-sized specimens (Figure I ; same locality as Loc. II of Mori and Osada, 1979).

Figured specimens are stored at University
Museum, University of Tokyo (UMUT).
Incidentally, L. (L.) azumana is an extinct
species, established by Yokoyama (1910) forsmall, oblique, and inequilateral specimens
with a smooth inner margin from the early
Pleistocene Koshiba Formation in Yokohama City. These features are commonly
observed in the examined material from the
Ninomiya Group. Later authors attributed
the subgeneric and generic positions of thisspecies to L. (Nipponolimopsis) (Habe, 1951 ;Taki and Oyama, 1953; Oyama, 1973) or
Nipponolimopsis Habe, 1951 (Habe, 1973), but
the diagnostic characters of Habe's (1951)
Nipponolimopsis, especially incised inner margin and surface ornamentation consisting ofconcentric and radial ribs, are not present in909.

Early life history of Limopsis

the type specimens of L. azumana (UMUT
CM 26402, 26403), although fine radial liraecrossed by concentric ribs faintly occur inboth the type and the Mushikubo specimens.
I treat the generic and subgeneric positions of
this species as Limopsis (Limopsis) by reasonof the smooth inner margin and the absenceof prominent radial ornamentation.
Methods.-A block of fossil-bearing sandsof 2,000 cm 3 in volume (20x lOx 10 cm) wascollected from the locality. A small amountof sands (35 cm 3 ) was removed from the bulk
sediment sample. After having dried anddispersed the sand particles, juvenile shells ofbivalves were picked up carefully with a finebrush from sediments scattered on a laboratory dish under a binocular microscope.
The remaining sediment sample was wetsieved through a 500 pm diagonal meshscreen, and fossil molluscs were removed fromresidues under a binocular microscope.
Juvenile shells of L. (C.) oblonga and L. (L.)
azumana were identified by successively correlating the large individuals with smaller
ones on the basis of overall morphology, sizeand hinge structure at the prodissoconch andearly dissoconch stages. Total number ofjuvenile shells for each species in the bulk
sediments was calculated from the number ina unit sediment (35 cm 3 ). Besides the above
two species, Glycymeris rotunda (Dunker)
occurs abundantly at the fossil locality.
Juvenile shells of this species are more or lesssimilar in the prodissoconch morphology andhinge structure to those of L. (C.) oblonga,
but are distinguished from the latter by possessing a more rounded, equilateral shell
outline. Other bivalve species from thelocality (e.g. Nemocardium samarangae,
Paphia naganumana, Solen gran dis, Macoma tokyoensis) are quite rare in occurrence,and their juvenile shells are easily distinguished from those of the two limopsids inhaving different hinge structure.
Selected juvenile shells of the two species
were coated with platinum using an ion
coater, and their external morphology and633

hinge structure were examined by means of ascanning electron microscope (Hitachi, model
S-430). Juvenile shell growth in the Bivalvia is divided into three ecologically andmorphologically well-defined stages, i.e.
prodissoconch I (= initial shell secreted by
the shell gland and mantle epithelium during
the stage developing from the non-shelledtrochophore stage for species with larval stageor during the embryonic stage for species
without larval stage), prodissoconch II (=theshell deposited by the mantle edge during thepelagic stage), and dissoconch (=the shellformed after metamorphosis) (Werner, 1939;
Rees, 1950; Ockelmann, 1965; Carriker andPalmer, 1979; Jablonski and Lutz, 1980,1983). I recognized these stages in the twolimopsids on the basis of definition by Ockelmann (1965) and Jablonski and Lutz (1980).
Juvenile shell morphology

Limopsis (Crenulilimopsis) oblonga. - As in
the other species with a larval stage, theprodissoconch of this species is divided into
prodissoconch I and prodissoconGh II (Figure2-A). The prodissoconch I is characterized
by the D-shaped outline, coarse and punctatesurface without growth lines, more or lessprojected umbonal region, and the rather
long and straight hinge line (Figures 2-A, B).
Its length ranges from 170 pm to 200 pm i,nthe present material.
The prodissoconch II is well developed,
measuring at about 200 pm in height. The
surface ornament consists of fine and dense
concentric growth lines and fine radial striations (Figures 2-B, C). The prodissoconch
II-dissoconch boundary is clearly distinguished by the abrupt expansion of concentric growth lines and coarsening of surface
texture (Figure 2-C). The above features in
the prodissoconch stage of the Middle Pleistocene form are essentially identical withthose of the Upper Pliocene one described by
Tanabe and Zushi (1988). ;.
Hinge development in the prodissoconch

634

Kazushige Tanabe

909.

Early life history of Limopsis

stage is uncertain, because no true prodissoconchs were found in the present material.
Early dissoconchs of approximately 0.5 mm
length possess a well-marked cardinal toothon both anterior and posterior edges of thehinge (Figures 2-D, E). Judging from thisfact, the hinge in the prodissoconch stage
probably consists only of a series of primitive
ligament pits (provinculum), as in the larvaeof other Pteriomorphia (Rees, 1950; Le Pennec, 1976, 1980; Siddall, 1978; Lutz and
Hidu, 1979). Juvenile shells of approximately 1 mm length have two anterior and posterior cardinal teeth, increasing their number as
the shell grows (Figure 2-F).
The inner ventral margin is smooth in theshells of about 0.6 mm length, but it is distinctly crenulated in the shells larger than 1
mm length (Figure 2- F).
Limopsis (Limopsis) azumana. - This
species possesses an unusually large prodissoconch I ranging from 400 pm to 450 pm inlength. It has a D-shaped outline with abroadly rounded ventral margin and a longand straight hinge line (Figures 3-A, D).
The mid-portion is markedly inflated with anelliptical flat crest, from which many radialstriations extend marginally (Figure 3-B).
Prodissoconch I is followed by dissoconch
without prodissoconch II stage. The prodissoconch I-dissoconch boundary is clearlymarked by the presence of a conspicuous
constriction (arrows in Figures 3-A, C).
The dissoconch is ornamented with many
concentric growth bands (Figures 3-A, C).
At the prodissoconch I stage dentition isabsent. The hinge apparatus (provinculum)of the fully grown prodissoconch (ca. 450 pm .
length) is long and straight (ca. 330 pm
length), and consists of a series of ligamental

635

pits (Figure 3-D). Cardinal teeth appear on
the anterior and posterior edges of the hingeat the early dissoconch stage (ca. 0.8 mm inlength; Figure 3-E). Dissoconchs of 1.2
mm in length have two anterior and posteriorcardinal teeth (Figure 3-F).
The inner shell margin is smooth throughout the whole stage of ontogeny.

Mode of occurrence
Juvenile shells of Limopsis (Crenulilimopsis) oblonga and L. (Limopsis) azumana fromMushikubo locality are found in a good stateof preservation, retaining detailed shell features. Similar evidence is also recognized in
the large-sized specimens of the two species
from the same locality. For example, thesample of L. (C.) oblonga larger than 4 mm
in shell length in the sand block of 2,000 cm 3consists of 73 articulated valves and 274
disarticulated valves (141 right and 133 left
valves). Both articulated and disarticulated
specimens of this species show no trace ofabrasion on their shell surface, and furthermore, most specimens retain an organic ligament. Based on these lines of evidence, I
regard the samples of the two limopsids fromthe fossil locality as virtually autochthonous,
and empty shells have been accumulated overa period of time as a normal fossil population. The size frequency distribution of L.
(L.) azumana from the fossil locality is characterized by a strongly right-skewed, negatively sloping distribution pattern, showing thepredominance of small individuals (Figure4). The numerical ratio of the minute shells
less than 1 mm length to the total specimens
reaches 95.5% (3885/4068).
The sample of L. (C.) oblonga consists of+--- Figure 2. Scanning electron micrographs of juvenile shells of Limopsis (Crenulilimopsis) ohlonga (A.
Adams) from the Middle Pleistocene Lower Shimoda Formation at Mushikubo, Ninomiya Town, Kanagawa
Prefecture. Outer (A-C) and inner (D-F) views. A. Articulated valves (UMUT RMI8880-1). pdI:
prodissoconch I, pdll: prodissoconch II, d: dissoconch. B. Part of A, showing the prodissoconch 1prodissoconch II boundary (arrow). C. Part of A, showing the prodissoconch I1-dissoconch boundary(arrow). D. Right valve (UMUT RMI8880-2), E. Left valve (UMUT RMI8880-3), F. Left valve (UMUT
RMI8880-4). Scale bars indicate 100 pm for A, D-F and 10 pm for B-C.

636

Kazushige Tanabe

909.

Early life history of Limopsis

L. (Crenulilimopsis)

637

L. (Limopsls) azumana

oblonga3900

N=46402000

N=4068

en
..J

<
~
o
> 1500
o
Z

-

3800

=:;:,:
1000

200

500

100

u.

o

a:

w
III
~
~

Z

00 1 2 3 4 5 6 7 8 9 101112131415

0 1 2 3 4 5 6 7 8 9 10 1112

SHELL HEIGHT (mm)Figure 4. Size-frequency histograms of the shells of Limopsis (Crenulilimopsis) oblonga and Limopsis(Limopsis) azumana in a unit sediment sample (2,000 cm3 in volume) from the fossil locality.

two clearly defined groups. The smallergroup is represented by juvenile specimens
less than 5 mm in length, showing the stepwise decrease in the frequency of occurrencewith increasing shell size. This groupoccupies 97.2% for the numerical ratio to thetotal number of individuals (4512/4640).
The larger group forms a broad and fairly
symmetrical cluster with a peak at 10-11 mm.
Similar abundant occurrence of juvenile
shells is commonly recognized in many primary death bivalve assemblages in modern

environments (e.g. Powell et al., 1984; Cummins et al., 1986).

Discussion

Developmental types. - The relationshipbetween juvenile shell features and developmental types has been investigated in many
Recent bivalve species from observation ofearly shell morphogenesis by culture methods(Thorson, 1936, 1946; Yoshida, 1953; Ockelmann, 1965; Sastry, 1965; Chanley, 1965,+- Figure 3. Scanning electron micrographs of juvenile shells of Limopsis (Limopsis) azumana Y 0koyama from the Middle Pleistocene Lower Shimoda Formation at Mushikubo, Ninomiya Town, Kanagawa
Prefecture. Outer (A-C) and inner (D-F) views of disarticulated valves. A. Early dissoconch (UMUT
RMI8881-1), B. Early dissoconch (UMUT RMI8881-2), C. Enlarged view of early dissoconch (UMUT
RMI8881-3), D. Full-grown prodissoconch with a straight hinge (provinculum) (UMUT RM 18881-4), E.
Early dissoconch (right valve) with a pair of cardinal teeth (UMUT RMI8881-5), F. Early dissoconch (leftvalve) with two pairs of cardinal teeth (UMUT RMI8881-6). Scale bars in all figures indicate 100 j.lm.

638

Kazushige Tanabe

1966, 1969; Chanley and Chanley, 1970;
LaBarbera and Chanley, 1970, 1971; Chanley and Andrews, 1971, among others).
Ockelmann (1965) and Jablonski and Lutz
(1980) documented some criteria to distinguish the developmental type of a given
species from prodissoconch features. Basedon the criteria by these authors, let us consider the developmental type of the twolimopsids examined.
Limopsis (Crenulilimopsis) oblonga is anextant species known from lower sublittoral
to upper bathyal zones off southwest Japan(Habe, 1977), but its early life history isvirtually unknown because of the difficulty inrearing larvae in the laboratory. The Middle
Pleistocene form of this species examined hasa relatively large prodissoconch I, whose
dimensions are comparable with those of
Recent species with a short lecithotrophic
larval stage (Ockelmann, 1965). This fact
and the presence of a well-developed prodissoconch II stage seem to suggest that the
Middle Pleistocene form of this species probably underwent lecithotrophic developmentwith a short, non-feeding larval stage. The
same interpretation was presented by Tanabe
and Zushi (1988) for the Upper Plioceneform.
In contrast to L. (C.) oblonga, Limopsis(L.) azumana has an unusually large prodissoconch without prodissoconch II stage.
This feature is common in many Recent
bivalves without a pelagic stage. Therefore,
I regard the developmental type of this species
as direct development or ovoviviparity. A
considerable number of marine bivalve
species have been known to undergo direct
development in association with broodprotection (Ockelmann, 1965). It remains
uncertain whether L. (L.) azumana developed with brood-protection or not, becauseof the absence of reliable criteria from prodissoconch morphology on this problem. As
described before, the mid-portion of prodissoconch I in L. (L.) azumana exhibits anelliptical flat crest and radiating striations

from its margin. The overall morphology isquite similar to that in the primary shells of
conchiferan molluscs (Bandel, 1982). In
Recent bivalves known to us, the primaryshell consists of a single organic conch withoval outline (Waller, 1981; Bandel, 1988).
The organic primary shell is secreted by theinterior rudiment of the mantle (shell gland)
during the pre-veliger stage, followed bydeposition of the bivalved calcified shellbeneath it (Bandel, 1988). Secretion of anoval to spherical organic primary shell by theinterior shell gland prior to a mineralizedshell has been confirmed in other molluscangroups (e.g. "cicatrix" in nautiloid cephalopods; Arnold et al., 1987), and this suggests
a similarity in basic morphogeneric programamong conchiferan molluscs (Bandel, 1982,
1988).
Juvenile mortality. - Although early shell
growth rate in bivalves greatly depends on
many eivironmental factors such as ambient
water temperature and food supply, previous
studies on bivalve early shell growth in thelaboratory have shown that most species
attain 1 mm in shell length within 10-50 days
after metamorphosis (Yoshida, 1964). Thisevidence seems to suggest that the small-sizedshells in the fossil assemblages of the two
species of Limopsis died immediately after
settlement and added to the death assemblages.
Studies of molluscan living populations
and death assemblages in modern environments have shown that a considerable numberof juvenile empty shells is inputted in thedeath assemblage by natural mortality of
newly settled spat (Powell et al., 1984;
Shimoyama, 1985; Cummins et al., 1986).
From comparative analysis of living populations and death assemblages of the thirteen
bivalve species on the Texas coast by monthly
sampling, Cummins et al. (1986) realizedthat the longest half-lives in any of these
species are less than one year. In consequence, the expected size-frequency distribution of the primary death assemblage is char-909.

Early life history of Limopsis

acterized by the predominance of empty shellsof small, newly settled spat. Nevertheless,juvenile shells including prodissoconchs are
seldom found in many fossil assemblages, as aresult of their selective destruction and dissolution during the taphonomical process.
The Middle Pleistocene samples of L. (C.)
oblonga and L. (L.) azumana examined are,in this respect, quite unusual examples which
preserve the properties of the original death
assemblages.
The size-frequency distributions of the samples examined apparently suggest a muchhigher mortality rate in the juvenile stage
than in the middle- to later-growth stages inthe two species, especially in L. (L.) azumana. It is strongly postulated from thisstudy that the two limopsids examined had
equally high juvenile mortality, although
they underwent different developmental histories.
Acknowledgments.-I thank Itaru Hayami,
Klaus Bandel and Richard A. Lutz for stimulative discussion on molluscan larval ecology,
and Toshiaki Osada and Tadashi Tokumoto
for their kind assistance in collecting fossil
samples. Neil H. Landman read the firstdraft of the manuscript critically. This work
was supported by the Grant-in-Aid from theJapanese Ministry of Education, Science andCulture (No.63540622 for 1988-1989; No.
01460062 for 1989).

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639

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of Marine Biology, Vol. I, p. 1-136, Academic
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Dan. Fisk. Havunders., vol. 4, p. 1-523.
Waller, T.R., 1981: Functional morphology anddevelopment of veliger larvae of the European
oyster, Ostrea edulis Linne. Smithsonian Contr.
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Werner, B., 1939: tiber die Entwicklung und
Artunterscheidung von Muschellarven des Nordseeplanktons, unter besonderer Beruchsichtigung
der Schalenentwicklung. Zoo!. Jahrb. Abt.
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Yokoyama, M., 1910: On species of Limopsis foundin the Neogene of Koshiba. Jour. Geol. Soc.
Tokyo, vol. 17, p. 1-5, pI. 9.
- - , 1926: Neogene shells from Kozuke and otherprovinces. Jour. Fac. Sci., Imp. Univ. Tokyo,
Sec. II, vol. I, p.229-233, pI. 29.
Yoshida, H., 1953: Studies on larvae and youngshells of industrial bivalves in Japan. Jour.
Shimonoseki ColI. Fish, vol. 3, p. 1-106. (inJapanese)- , 1964: Seedling of Shell-jish. 221 p. Hokuryu-kan Book Co., Tokyo. (in Japanese)

Koshiba 'Hf~, Mushikubo .!It,~, Naganuma :IltlB, Ninomiya =.1r, Shimoda rlE.
<Ptm~~1!!: Limopsis ,\1i,=.f.jc9l. 2 fiQ)fJJM~m~: Limopsis ~=.f.jcJ'l 2 fI, L. (Crenulilimopsis) oblonga:to J: v: L. (L.) azumana Q)fJJM~m~~::."?~,-C, f!I!~JI'Yf.:=1rIllT.!It,~Q)<pttm~~*1t=1rl!fF<Ptmg[Q)i*ffO) J: ~'X!J9l.j!\t:*~ c ~::.~~ L. t.::~*, -t- .h.:f.h~m~a~ml,@::it9E~t L. ft!J~9il~mlQ)9E:itl*~iJ~j'ltiE~.ht.::o ~ I?~::', 1tEg[:!tB~::.:to~7.>{tEm9l.

<O)g[:/7I:o)~~iJ' I?,~1?.h7.>ojifijfl c t ~m1.Jn.A.Q)fJJMf&IlM'"(· ~b.!b-C~~'7EL$~~'? -C ~,t.:: c;,lf
mtm-~

Trans. Proc. Palaeont. Soc. Japan, N.S., No. 160, pp. 641-662,5 Figs., December 30, 1990

910. PLIOCENE-PLEISTOCENE MOLLUSCAN ASSOCIATIONSIN NORTH-CENTRAL JAPAN AND THEIRRELATIONSHIP TO ENVIRONMENTS*
SEIICHIRO MATSUI
Department of Earth Sciences, Faculty of Education,
Utsunomiya University, Utsunomiya, 321

Abstract Seven major groups of molluscan associations are recognized in theJapanese cold water molluscan faunas ranging over about 5 million years from latest
Miocene to Pleistocene. Each of the groups is composed of local associations which aresimilar not only in species or genus composition but also in environmental preference to one
another, and accordingly are in ecologically parallel relationships with one another. The
distribution ofthe association groups was controlled primarily by water depth and grain sizeof bottom sediments. Each of the fossil association groups has analogous living communities comparable in their composition and habitat around Japan. Among these sevengroups the Acila-Turritella Association Group is the most prevalent and is the fossil representative of the lower sublittoral community. The Delectopec/en and Nuculana Association
Groups are interpreted as deeper dwellers. The Anadara and Macoma-Mya Association
Groups represent shallow marine environments, comparable with sandy and muddy upper
sublittoral faunas, respectively. Occurrence of the Thyasira Association Group may berelated to a reducing environment. The Chlamys Association Group occupied coarsegrained sand bottoms of the lower sublittoral or upper bathyal zone.
Key words. Cold water marine molluscs, faunal association, North-Central Japan,
parallelism, Pliocene-Pleistocene.

among stratigraphically or geographicallyisolated faunas and a basis for understanding
community evolution (Chinzei and Iwasaki,
1967; Chinzei, 1984; Walker and Laporte,
1970; Boucot, 1975, 1981).
The ecologically parallel relationship has
been recognized among the faunas of threedifferent ages in the Japanese Neogene, namely early Middle Miocene, Middle Miocene
and Pliocene (Chinzei and Iwasaki, 1967;
Chinzei, 1978). In muddy tidal flat sediments, for example, there appear associationsof the Crassostrea bank in all of the threeages. These parallel associations may betreated as an association group which corresponds to the muddy tidal flat environment.
Four major association groups representing

Introduction

Ecologically analogous faunal associations, which are similar to each other intaxonomic composition and environmental
preference, are found among local benthic
faunas of different ages and different areas(e.g., Chinzei and Iwasaki, 1967; Walker
and Laporte, 1970; Hickman, 1984). This
relationship seen among fossil associations iscomparable with the ecological parallelism(Thorson, 1957) recognized among biogeographically isolated communities in the Recent
marine bottoms. The relationship provides
the framework for ecological comparison·Received December 26, 1989; revised manuscript
accepted October 22, 1990
641

642

Seiichiro Matsui

the tidal flat to subtidal shallow environments are known in the shallow marine sediments of the Japanese Neogene (Chinzei andIwasaki, 1967).
In the Neogene off-shore faunas, however,such a relationship of associations has notbeen sufficiently described. The aims of thispaper are to recognize ecological parallel
relationships among the latest Miocene toPleistocene molluscan faunas, probably ranging from upper sublittoral to upper bathyalenvironments, in the cold water region ofJapan, and to discuss relationships between
these association groups and environments.
Also, the fossil associations are comparedwith the living molluscan faunas around
Japan. I previously recognized six molluscan associations and discussed their habitat
preferences in the Pliocene-lower Pleistocene
sedimentary basin in the Gojome-Oga Area,
Northeast Honshu (Matsui, 1985a, b). In thepresent study, molluscan associations of other
Neogene basins in Northeast Japan arecompared with those of the Gojome-Oga
Area with respect to taxonomic compositionand environmental preference. The result
will give us the bases to discuss historical andbiogeographic changes in the molluscan
faunas (Matsui, in prep.).

ed environments. The Omma-Manganji
Fauna appears in the uppermost Miocene tolower Pleistocene formations, and is distributed mainly in the coastal area of the Japan Sea.
It is composed of deep off-shore to shallow
subtidal dwellers (Kaseno and Matsuura,
1965; Chinzei, 1973; Ogasawara, 1977).
The Tatsunokuchi Fauna is known from the
Pliocene distributed in the Pacific coast of
Northeastern Honshu, and is of an embayment environment (Chinzei and Iwasaki,1967). It contains forms congeneric to, butdifferent in species level from those of theOmma-Manganji Fauna, with forms characteristic to the fauna as represented by Fortipecten. The Takikawa-Honbetsu Fauna,
which is restricted to the Pliocene of Hokkaido, is composed of both off-shore andshallow sea elements, including Fortipecten(Uozumi, 1962).
Composition of these molluscan faunas,
stratigraphy and lithology are summarized
here for six areas (Gojome-Oga; Tsubata;Omma; Sado; Hamada; Ishikari-Numata)with supplementary data from other areas(Himi; Nishiyama; Northern Uonuma;
Taihei; Futatsui; Higashimeya; Daishaka;Molluscan associations and theirgeologic setting
The uppermost Miocene to lower Pleistocene marine strata distributed in Hokkaido,
Northeast Honshu and the Japan Sea coastal
area of Central Honshu are composed ofvarious siliciclastic sediments and containabundant molluscan fossils of cold water
nature. Three molluscan faunas, namely theOmma-Manganji, Tatsunokuchi and Takikawa-Honbetsu Faunas, have been distinguished in these strata on the basis of thedifference of species composition (Otuka,
1939; Chinzei, 1963, 1978). They are different from each other in geographic and stratigraphic distributions and in their reconstruct-·~r~p
Figure 1. Map of the Japanese Islands andshowing the locations of the late Miocene-early
Pleistocene sequences concerned in this study.

910.

Plio-Pleistocene molluscan associations

Kamiiso; Setana; Sannohe; Sendai) (Figure 1). Details of these faunas were described elsewhere (Matsui, 1985a, b, c, 1988).
The Pliocene and Pleistocene strata in theseareas include various sedimentary types andcontain well preserved molluscan fossils.
Data for the supplementary areas are basedon publications, and samplings made bymyself.
The strata containing these molluscan
faunas generally represent regressive sequence
from off-shore muddy facies to near-shore
sandy sediments upward. Molluscan fossils
are abundant in coarser-grained facies of thelater stage of the regression. Because thesefossiliferous sediments appear as separate
sedimentary basins, different lithostratigraphic classifications have been established foreach basin, and interbasinal correlations areinevitable prior to discuss distributions ofmolluscan faunas in time and space. Age
assignments of the sequences studied are principally based on published biostratigraphy ofplanktonic microfossils, in some cases combined with magnetostratigraphic records.
For areas of no published age data, the ages
are inferred from planktonic microfossils
obtained during the present study.
The term "assemblage" used here is defined
as a set of molluscs found from a bed within
20 to 100 cm thick in one small exposure.
Molluscs larger than 2 mm were extracted
from about 2 to 10 kg bulk-rock sample
obtained from the bed, and were identified.
The whole set of the molluscs are treated as
an assemblage. In the Ishikari-Numata section, where exposures are nearly parallel tothe bedding planes, molluscs in an exposure
surface of 1 m2 were collected to represent anassemblage.
Consistent and recurrent association of
species is recognized among the assemblages
in each area. Because most of the molluscs
are considered to be autochthonous as discussed below, these faunal associations recog. nized may be regarded to represent a part of apast benthic community in the sense of Peter-643

sen (1918, 1924).
Honda (1978) and Shimamoto (1984) proposed more split molluscan associations thanthose of Matsui (1985a, b) in the Gojome-Oga
Area. It is, however, difficult to recognize acausal relationship between these split associations and environmental factors inferredfrom sedimentary facies. Moreover, splittingof associations makes inter-areal comparisonsof associations difficult, because local or accidental variations of the species compositions
are more likely to be overemphasized.
Preservation of original community composition in fossil associations largely depends
on degree of post-mortem transportation andmixing of the living assemblages. The strata
enclosing the fossil faunas are composed ofvarious sedimentary facies, but are dominatedwith siltstone or fine-grained sandstone, inwhich many well-preserved molluscs arefound. Shells show wide range in size, andmany microscopic immature shells are found,particularly in the muddy sediments. Deepburrowing bivalves such as Mya and Thyasira
are usually preserved at the living position,
while shells of non- or short-siphonate shallow burrowers are found as separated valves
and randomly oriented. The shells of theseshallow burrowers, however, are rarely abraded or broken. The difference in preservation
between deep and shallow burrowers seems
quite reasonable because the shells of theshallow burrowers are easily reworked anddislocated by the current or activities of burrowing organisms (Matsui, 1985a).
Fine-grained sediments occasionally intercalate aggregated shell beds, in which shells
are more or less abraded and sometimes fragmented. These abraded fossils seem to havebeen transported after death. Ogasawara(1977) distinguished five molluscan associations in the sand-dominated Omma Formation of the Omma area in Kanazawa. These
five associations seem rather complex inspecies composition, partly due to postmortem transportation and mixing of species
originated from different communities. In

644

Seiichiro Matsui

this study, such transported assemblages are
excluded from the faunal analysis.

Brief descriptions of local associations
Gojome-Oga Area, Akita Prefecture
Modes of occurrence and composition of
the fossil molluscan fauna in the Gojome-Oga
Area were described by Matsui (1985a, b).
The fauna was regarded as the Pliocene to
Early Pleistocene (Matsui, 1981, 1985a).
Sato et al. (1988), however, showed that thewhole of the sequence containing the molluscan fossils should be assigned to the Pliocene
on the basis of calcareous nannofossil andplanktonic foraminiferal assemblages.
The fossil molluscs appear in various sedimentary facies ranging from deep turbidite toshallow fine-grained sand facies. Six molluscan associations are recognized among thefossil fauna.
The Delectopecten Association ( = Palliolum Association of Matsui, 1985a) composed only of Delectopecten peckhami(Gabb) is restricted to deep turbidite facies.
The Nuculana Association is characterized
by nuculanid bivalves with buccinid andturrid gastropods. It appears mainly in silty
facies. The Thyasira bisecta Association is
low in diversity, predominated by Thyasirabisecta (Conrad). It is found from bothsandy and silty facies.
The Acila-Turritella Association is thecommonest among the molluscan associationsin the area, characterized by Acila nakazimai
Otuka, Turritella saishuensis Yokoyama,
Macoma calcarea (Gmelin), Clinocardium
chikagawaense Kotaka, Mya cunei/ormis(Bohm) and Glycymeris derelicta (Yokoyama). It is found mainly in sandy silt
facies.
The Macoma tokyoensis Association isdominated with Macoma tokyoensis Makiyama. The Protothaca Association contains
thick-shelled bivalves such as Protothacaadamsi (Reeve) and Anadara amicula(Yokoyama). The last two associations

appear in fine-grained sand facies representing the shallowest environment in the area.
Tsubata Area, Ishikawa Prefecture
The Acila nakazimai-Turritella saishuensis
Association is recognized in the section of 30
m thick, belonging to the Tsubata Siltstone of
the Himi Formation (Sumi, 1978). The section is assigned to the uppermost Pliocene or
lowest Pliocene on the basis of calcareous
nannofossils (T. Takayama, personal communication). The section is composed of siltstone in the lower part and grades upward
into sandy siltstone. The sand content rises
from 30-35% to 50-65% upward. The sediments are intensively bioturbated and containwell preserved molluscan fossils. This association is dominated by Acila nakazimai andTurritella saishuensis, accompanied withClinocardium chikagawaense in the siltstone
and with more diverse molluscs such as
Limopsis sp. A and Cyclocardia cf. crebricostata (Krause) in sandy siltstone.
Omma Area, Ishikawa Prefecture
Molluscan fossils were examined in thesection of about 200 m thick along the Saigawa River in Kanazawa City, where thelower Pleistocene Omma Sandstone of theHimi Formation is exposed (Hasegawa, 1979;
Takayama et al., 1988). This section ismainly composed of well-sorted fine-grainedsandstone, which is rather muddy and finer
grained in the middle part. The sandstone ispoor in current-generated sedimentary structures and abundantly contains mud tubes andmud pellets created by burrowing organisms.
Molluscan fossils usually occur sporadically, but several crowded shell beds are also
found in the section. The shells showing the
sporadic occurrence are well preserved and do
not seem to have been transported from their
original habitats.
The following four associations are recognized among these autochthonous molluscan
fossils. The lithofacies are similar to eachother, fine-grained sandstone, but each ofthese associations shows a characteristic
species composition and occupies a distinct

910.

Plio-Pleistocene molluscan associations

stratigraphic position in the section.
Acila insignis-Turritella saishuensis Association: This association usually occurs as
moderately diverse assemblages in the middle
part of the section. It is characterized byabundant and ubiquitous occurrence of Acila
insignis (Gould), Turritella saishuensis, associated with Lunatia pi/a (Pilsbry), Searlesia japonica Yokoyama, Huxleyia sulcata
A. Adams, Yoldia notabilis Yokoyama,
Felaniella usta (Gould), Cyclocardia ferruginea (Clessin), Clinocardium fastosum (Yokoyama) and Pandora pulchella Yokoyama.
Some others such as Ringicula doliaris
Gould, Mizuhopecten tokyoensis, and Macoma tokyoensis are also numerically abundant but they also appear commonly in otherassociations described below. At an assemblage in the muddy middle part of the section,
Acila insignis is substituted by congeneric A.
divaricata (Hinds). Nucula niponica Smith,
Cycladicama cumingii (Hanley) and
Nemocardium samarangae (Makiyama)
exclusively appear in this assemblage in addition to Turritella saishuensis and Cyclocardia
ferruginea.
Kitamura and Kondo (in press) recognizedin the middle part of the Omma section, cyclicchanges of molluscan composition and occurrence, which are induced primarily by glacioeustatic sea level change. One cycle begins
with a densely crowded bed of molluscan
shells composed of upper sublittoral cold
water species, and changes upward to autochthonous shells of transgressive lower sublittoral faunas which are usually warm water
nature. The Acila insignis- Turritella saishuensis Association corresponds with the lower
sublittoral associations of Kitamura andKondo (in press).
Scapharca pseudosubcrenata Association:
This association is highly diverse and appears
in a 4 m-thick interval at the uppermost partof the section. Two large bivalve species of
Scapharca, S. aff. ommaensis (Otuka) and S.
pseudosubcrenata (Ogasawara), are characteristic in the association, though they are not645

numerous. Smaller species such as Reticunassa sp., Oliva mustelina Lamarck, Pillucina yamakawai (Yokoyama), and Veremolpa minuta (Yokoyama) also characterize
the association and occur abundantly. Someothers such as Mitrella lischkei (Smith), Ringicula doliaris Gould, Saccella confusa (Hanley), and Pecten alMcans (Schroter) are alsoabundant but they also appear in the Acila
insignis- Turritella saishuensis Association.
Scapharca ommaensis Association: This
association is characterized by abundant
Scapharca ommaensis (Otuka). Conjoined
individuals of the species are accompaniedwith a smaller number of well-preserved,
separated shells of Mizuhopecten tokyoensis(Tokunaga) and M. yokoyamae (Masuda).
Scapharca ommaensis is very akin to S. aff.
ommaensis, which characterizes the S.
pseudosubcrenata Association. But the present association is different from the preceding
one in the species composition other than
Scapharca and in having lower species diversity. The association occurs at a lower horizon of the section, stratigraphically about 100
m below the S. pseudosubcrenata Association.
Anadara amicula Association: This association is characterized by abundant Anadara
amicula and Clinocardium sp., associatedwith Turritella saishuensis, Striodentalium
rhabdotum (Pilsbry) and isolated immatureshells of two pectinid species, Mizuhopecten
yokoyamae and M. tokyoensis. This association occupies the lowest horizon of the section, about 40 m below the Scapharca ommaensis Association.
Sado Area, Niigata Prefecture
Two lower Pleistocene fossil localities were
examined in Sado Island.
Nuculana Association: This association isobserved in sparsely bedded, dark-greenishgray coarse-grained siltstone of the Shichiba
Formation (Utashiro et al., 1977) at a large
seaside exposure of Shichiba. It is mainlycomposed of two deposit-feeding bivalves of
Nuculana robai (Kuroda) and Portlandia

646

Seiichiro Matsuitoyamaensis (Kuroda) associated with
Axinopsida subquadrata (A. Adams) and
Siphonodentalium sp. The shells are sporadically dispersed in the siltstone, and minuteunidentified gastropods and bivalves areabundant.
Transported assemblages: Three assemblages from calcareous medium- to coarsegrained sandstone belonging to the Kaidate
Formation (Utashiro et al., 1977) at Kaidate
seem to have been experienced post-mortem
transportation and accumulation, for theshells are crowded and many of them areabraded and broken. They are characterized
by abundance of the pectinid species such as
Chlamys cosibensis (Yokoyama). Glycymeris
sp. and some other epifaunal or shallow
burrowing bivalves are also common.
Although these assemblages were transported
after death, they are similar to some nontransported assemblages in coarse sediments
as discussed later. They probably preserve apart of their original composition of the living community.
Hamada Area, Aomori Prefecture
The section belonging to the Hamada
Formation (Yamaguchi, 1970; Kanazawa
and Yamaguchi, 1988) exposed along the
Chikagawa River, north of Hamada is examined, supplemented by exposures along theMaekawa River. This section is composedof tuffaceous, calcareous, medium- to coarsegrained sandstone in the lower part, andfine-grained sandstone and massive siltstone
in the upper part. The section is assigned
presumably to the lower Pleistocene on thebasis of planktonic foraminifers (H. Kitazato,
personal communication). Well-preserved
molluscs of eight assemblages are grouped
into the following two associations.
Acila-Macoma Association: This association appears both in the siltstone and finegrained sandstone of the upper part of thesection. Acila nakazimai, Macoma calcarea
and Clinocardium chikagawaense are dominant. The assemblages in the silty part areassociated with Mya cuneiformis, Portlandia

sp. and Thyasira bisecta. The assemblages
in the fine-grained sandstone contain morediverse species, among which Turritella saishuensis, Nuculana yokoyamai Kuroda andCyclocardia Jerruginea are numerous.
Chlamys Association: Some pectinid
species such as Chlamys cosibensis, C. islandica (Miiller), Yabepecten tokunagai (Yokoyama) and Polynemamussium alaskense(Dall) are characteristic of this association.
Cyclocardia Jerruginea, Tridonta alaskensis(Dall) and some others are commonly foundin this association, but they also appear in the
Acila-Macoma Association. This association occurs in the lower calcareous mediumto coarse-grained sandstone.
Ishikari-Numata Area, Hokkaido
The molluscan associations in this area
were described elsewhere (Matsui, 1988). A
brief summary of the associations is asfollows.
The Pliocene Horokaoshirarika Formation(Kobayashi et al., 1969) is exposed along the/ Horonitachibetsu River, northwest of Ishikari-Numata.
Anadara Association: This association ischaracterized by abundant Anadara amicula
associated with Clinocardium sp., Protothacaadamsi and Felaniella usta. Fortipecten takahashii (Yokoyama) and Macoma calcarea
are also numerous. This association mainly
appears in the upper sandstone part of thesection.
Acila nakazimai-Turritella Jortilirata Association: This association is characterized by
Acila nakazimai and Turritella Jortilirata
Sowerby associated with Lucinoma acutilineata (Conrad), Cyclocardia sp. and Mya
cuneiformis. Fortipecten takahashii and
Macoma calcarea are abundant but not characteristic of the association. This association appears in the lower alternation part ofthe section.

Table 1.

Association GroupArea
De/ectopecten peckhami
Lunatia pallida
Fusitriton oregonensis
Buccinum cf. rossicum
Mohnia cf. yanamii
Neptunea Intersculpta
Antiplanes sanctiioanis
Nuculana robai
Portlandia toyamaensis
Buccinum spp.
Propebe/a candida
Portlandia hirosakiensis
Cryptonatica clausa
Neptunea spp.
Turrite/la nipponica
Nuculana yokoyamai
Yoldia thraciaeformis
Clinocardium chikagawaense
Macoma calcarea
Acila nakazimai
Cyclocardia ferrufJinea
Llmopsis tokaiens/s
Turrite/la fortilirata
Limopsis sp.A
Acila insignis
Fortipecten takahashii
Mya cuneiformis
Turrite/la saishuensis
Macoma tokyoensis
Glycymeris yessoensis
Anadara amicula
Scapha rca ommaensis
Scapha rca pseudosubcrenata
Scapharca aft.ommaensis
Dosinia tomikawensis
Mercenaria stimpsoniProtothaca adamsi
Clinocardium sp.
Mya japonica
Lucinoma annulata
Lucinoma acutilineata
Thyasira bisecta
Chlamys cosibensis
Chlamys is/andica
Po/ynemamussium a/askense
Yabepecten tokunagai

Representative species of the seven association groups.

D

NtDJana

Acila-Turritella

Anadara

MM

Th

Ch

GO

SO GO FUTS OMGO FU HA IS

GO FU GO IS OM OM OM

SE

GO

HA

•

0
0
0

••

•
•
0

0
0
0
0
0

0
0

••

'0

•
•

0

•

0

••
0

0
0

•
•

•

0

0

•
•

•

0

•

0

0

0
0

•
•

0
0
0

•

•

•

•
•
•

0

I

•

n>
t:;.
S
,..,

•

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•
0

•• •••
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•

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""tl

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....

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::3
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Association groups: D= Delec/opec/en; MM = Macoma-Mya; Th= Thyasira; Ch= Chlamys. Area: FU = Futatsui ; GO = GojomeOga; HA = Hamada ; IS=Ishikari-Numata; OM=Omma; SD=Sado; SE=Sendai; TS=Tsubata. Symbols indicate relative abundance ( • < 0 <.).

0
0
0

•
'"
....,
~

648

Seiiehiro Matsui

Types of molluscan associations and theirrelationship with environments

The fifteen recurrent molluscan associations described above are recognized primarily on the basis of taxonomic composition.
Each of them is found in a particular sediment type and in the particular stratigraphic
and geographic positions of the sedimentarybasin. The lithofacies in which molluscs
were found range from siltstone to coarsegrained sandstone.
These fifteen local associations are grouped
into seven types of associations, here called
the association groups, on the basis of similarity in the species or genus composition. For
example, the local Nueulana Associations in
the Gojome-Oga and Sado and the
Nueulana-Turritella nipponiea Association in
the Futatsui are abundant in Nueulana robai
and other nuculanid bivalves with buccinid
gastropods. These three local associations
are grouped into one association group, theNueulana Association Group. Seven association groups are recognized in the samemanner in the areas studied: namely Deleetopecten, Nueulana, Acila-Turritella, Anadara,
Mya-Maeoma, Thyasira and Chlamys Association Groups. The local assoclatlOns
belonging to an association group are foundfrom the same sediment type in the same
stratigraphic and geographic positions of thedifferent sedimentary basins, and hence theseassociations seem closely related to a particular environment, regardless of age and biogeographic province of individual associations.
In this sense, the local associations included
in one association group are in an ecologicalparallel relationship, though Thorson (1957)
originally used "ecological parallelism"
confined to contemporaneous communities
which are biogeographically isolated.
Relationships between the associations andenvironments have been discussed in the
Futatsui and Gojome-Oga, where five of theseassociation groups are recognized (Chinzei,
1973; Matsui, 1985a). Sediment type andwater depth were concluded to be the essential factors governing the distribution of theassociations in the areas. The similar relationships between molluscan associations andlithofacies are observed in other latest Miocene to early Pleistocene basins in Northeast
Japan, though geographic and stratigraphic
distributions of the associations in thesebasins have not been fully described. The
association groups are comparable with living molluscan faunas of the continental
shelves and slopes around Japan in composition and in relationship with environment.
The association groups and their living
analogues can be utilized for comparison
among faunas within a certain habitat but indifferent ages and different biogeographic
provinces, because of its consistency in environmental relationship as well as taxonomic
composition.
The characters in the species compositionof the seven groups and their relation toenvironments are summarized as follows andillustrated in Table 1 and Figures 2-6.
Deleetopeeten Association Group
This group is typically found in mudstoneof the turbidite sequence in the Gojome-Oga
as the Deleetopecten Association, which iscomposed exclusively of Delectopecten peekhami. The association may have occupied
the deepest environment among the associations found. The siliceous mudstone of the
Funakawa Formation in the Gojome-Oga
probably represents more off-shore facies, but
is barren of molluscs.
This small and thin pectinid species commonly occurs as monospecific assemblage in
the Miocene-early Pleistocene offshore
muddy sediments in Northeast Japan (Utashiro, 1957). This association group represents the deepest biofacies in the area studied.
Delectopecten peckhami is an extinct species.
Similar thin-shelled pectinid species, however, commonly appear in present-day continental slopes. Deleetopecten macroeheirieola
Habe and many other species of fragile
pectinid are found from muddy bottom of 500

910.

Plio-Pleistocene molluscan associations

649

Associa t ion Group

Figure 2. Major faunal elements of the Nueu/ana Associat ion Group. 1, Nueu/ana robai (Kuroda), Sado Area, Shichiba Formation , X I ; 2, Port/andia toyamaensis (Kuroda ), Sado Area, Shichiba
Form at io n, X I ; 3, Lunatia pallida (8roderip and Sowerby), Sado Area, Shichiba Formation, x l ; 4,
Buecinum sp. , Taihei Area, Tentokuji Formation, X I ; 5, Mohnia cf. y anamii (Yokoyam a) , GojomeOga Area, Wakimoto Formation , X l ; 6, Antip/anes sanetiioannis (Smith), Goj o me-Oga Area, W a kimoto
Formation, X I ; 7, Neptunea interseu/pta (Sowerby) , Taihei Area, Tentokuji Formation , x O.9.

to 2,000 m deep in the Pacific coastal areas ofJapan (Okutani, 1962).
Nucu/ana Association Group (Figure 2)
This type of association is represe nted by
the Nucu/ana Association of the Sado and
Gojome-Oga and the Nucu/ana- Turrite!lanipponica Association of the Futatsui , appearing in muddy facies. This is dominatedby sma ll deposit-feeding nucul a nid andnuculid bivalves and carnivorou s or saprophagous gastropods. Among them , Nuculana robai is the most common and widely

di stributed species. Other nuculanid s a nd
nuculids such as Portlandia toyamaensis, P.
hirosakiensis lwai , Saccella onoyamai(Otuka) and Acila nakazimai are loca ll y
ab undan t. The gastropods are represe nted
by many buccinid, turrid and naticid species,
among which Mohnia yanamii (Yokoyam a),
Antiplanes sanctiioannis (Smith) , Propebela
candida (Yokoyama) and Lunatia pallida(Broderip a nd Sowerby) are common , occasiona ll y associated with Neptunea interscu/pta (S owerby) , Buccinum cf. rossicum

650

Seiichiro Matsui

Acila - Turritella Associa t ion Group910.

Plio-Pleistocene molluscan associations

Dall, B. tsubai Kuroda and cymatiid Fusitrito
oregonensis (Redfield). Some bivalves suchas Limopsis tokaiensis, M acoma calcarea andThyasira bisecta occasionally appear in theassociations.
Fossil assemblages comparable to theseassociations have been reported rather rarely,
probably owing to very low density of individuals in the sediments. Many nuculanid
species were found in muddy facies of the
Nishiyama Formation in the Northern
Uonuma (ltoigawa, 1958). Four assemblages from the late Miocene Shitazaki Siltstone and Kamassawa Alternation in the
Sannohe contain Nuculana robai and N.
pernula (MUller) (Chinzei, 1979). A nuculanid and buccinid fauna is found from siltstone and sandy siltstone of the Pliocene
Tentokuji Formation in the Taihei Area, thefauna composed of Nuculana robai, Neptunea intersculpta, Buccinum spp. and Fulgoraria prevostiana (Matsui, 1977 MS).
This association group is known in the
Gojome-Oga basin from deep and muddy
environments but shallower than the
Delectopecten Association (Matsui, 1985a).
Living molluscan faunas analogous to the
Nuculana Association Group are found in
the muddy upper bathyal zone. A low diversity bathyal fauna comparable in species composition with the fossil Nuculana Association Group was found from two silty stationsof about 200 m deep off the Oga Peninsula(Takayasu and Yunohara, 1977). Thisfauna is dominated by small deposit-feedersof Nuculana pernula, N. robai and Yoldia
amygdalea (Valenciennes). In the area off
Kushiro, deposit feeding bivalves of Malletiaaff. takaii (Okutani) and Nuculana cf.
sagamiensis Okutani appear on silt bottom

651

deeper than 900 m (Matsui, 1985c).
A diverse molluscan fauna is living in
muddy continental slope of 200-1,500 m deepin Sagami Bay under the influence of thelower temperature "intermediate water"
beneath the warm Kuroshio water (Horikoshi, 1957; Okutani, 1968). This living faunacontains many genera common to the fossil
Nuculana Association Group, such as
Nuculana, Limopsis and Neptunea, though
they are different in species level. In addition to these, the living upper bathyal fauna isrich in genera but rare or absent in thefossil Nuculana Association. For example,
cuspidariid bivalves and trochid gastropods
are very rare in the fossils.
Acila-Turritella Association Group (Figure
3)This is the commonest type of associationsin the Omma-Manganji and TakikawaHonbetsu Faunas. The Acila-Turritella Association in the Gojome-Oga is typical of thisgroup. The local associations included inthis group are present in all the basins
examined, and appear in sandy siltstone or
fine-grained sandstone. The characteristic
common constituents of these associations are
species of Acila (A. nakazimai, A. insignis, A.
divaricata) and Turritella (T. saishuensis, T.
jortilirata, T. jortilirata habei Kotaka).
They are commonly associated with Macoma
calcarea, Clinocardium chikagawaense,
Cyclocardia jerruginea, Mya cunei/ormis,
Glycymeris derelicta and some others.
Among these species of Acila, an extinct A.
nakazimai is most prevalent and widely distributed. Acila divaricata is rather rare.
This species is associated with Acila nakazimai in the Kamiiso (Sakagami et al., 1966).
The Omma section contains both A. insignis~ Figure 3. Major faunal elements of the Acila-Turritella Association Group. 1, Acila insignis(Gould), Omma Area, Omma Sandstone; 2, Acila nakazimai Otuka, Gojome-Oga Area, Sasaoka Formation; 3, 4, Turritella saishuensis Yokoyama, (3, typical specimen; 4, habei type specimen. See text for
further explanation), Hamada Area, Hamada Formation; 5, Yoldia thraciaeformis (Storer), Tsubata Area,
Tsubata Siltstone; 6, Cyclocardia ferruginea (Clessin), Futatsui Area, Sasaoka Formation; 7, Clinocardium chikagawaense Kotaka, Hamada Area, Hamada Formation; 8, Macoma calcarea (Gmelin), Hamada
Area, Hamada Formation; 9, Mya cunei/ormis (Bohm), Gojome-Oga Area, Sasaoka Formation; 10,
Limopsis tokaiensis Yokoyama, Futatsui Area, Sasaoka Formation. All in natural size.

65 2

Seiichiro Matsui

910.

Plio-Pleistocene molluscan associations

and A. divaricata, which do not coexist witheach other, as noted before.
Species of Turritella also differ in places.
The three species of Turritella rarely exist
with one another in a local association, andshow different stratigraphic and geographic
distributions. Turritella saishuensis isrestricted to the Pliocene-early Pleistocene
Japan Sea side of Honshu. Turritella jortilirata appears in the Pliocene TakikawaHonbetsu Fauna of central Hokkaido. Turritella in the lower Pleistocene of southwestern Hokkaido was assigned to a subspecies ofT. jortilirata (T. f habei) (Kotaka, 1959;
Kanno, 1962; Sakagami et al., 1966). In
the transitional area between the realms of T.
saishuensis and T. f habei at the northernend of Honshu, there are populations intermediate between these two species. The
population of Turri/ella in some assemblagesof the Hamada Formation includes both ofsaishuensis and habei type specimens in
respect to spiral ornamentation (Figures 3-3,4), as well as intermediate forms between the
two types in the same assemblage. Similarintermediate populations were reported fromsandy siltstone of the Higashimeya Formation in the Higashimeya (Iwai, 1965). The
name of saishuensis is tentatively applied tothese populations.
Other constituent species of the associations are in some extent different from area toarea. The difference is partly due to difference in lithology or stratigraphic horizon andpartly to difference in geographic position of
the sections. Cyclocardia spp., Mya
cuneiformis and Macoma calcarea are foundcommonly in the sand-dominated Omma,
Futatsui and Ishikari-Numata sections and insandy parts of other sections. Clinocardium
chikagawaense, Yoldia thraciaejormis (Stor-

653er), Portlandia hirosakiensis are prevalent in
the muddy sections of the Tsubata, GojomeOga and Hamada. Limopsis is represented
by L. tokaiensis Yokoyama in the sandy
section of the Futatsui, while by L. sp. A(an akin form of L. tokaiensis) in the muddy
Tsubata section.
The species common to this associationgroup are found in siltstone and fine-grainedsandstone of the Haizume Formation in the
Northern Uonuma (Itoigawa, 1958). Threeassemblages from fine-grained sandstone of
the late Miocene Kamassawa Alternation in
the Sannohe (Chinzei, 1959) are dominatedby the representative species or their close
relatives of this association group such as
Cyclocardia ochiaiensis (Chinzei) (akin to C.
jerruginea), Clinocardium iwatense Chinzei(very similar to C. chikagawaense), Macoma
calcarea and Glycymeris derelicta, and also
contain a few species common to the
Nuculana Association Group.
In the regressive sequences of the Futatsui,
Gojome-Oga and Northern Uonuma, theassociations included in this group appear insandy silt facies or fine-grained sand facies,
and occupy stratigraphic levels upper thanthose of the Nuculana Association Group(Itoigawa, 1958; Chinzei, 1973; Matsui,
1985a). This suggests that the Acila-Turritella Association Group was the dweller
shallower than the Nuculana Association
Group. In the Futatsui and Gojome-Oga,
the Turritella-Limopsis-Acila and AcilaTurritella Associations are found in the areas
presumably nearer to the coast than those of
the Nuculana-Turritella nipponica andNuculana Associations (Chinzei, 1973; Matsui, 1985a). This supports the above inference.
Many of the main constituent species of the~ Figure 4. Major faunal elements of the Anadara Association Group.
1, Anadara amicufa (Yokoyama), Ishikari-Numata, Horokaoshirarika Formation; 2, Scapharca afT. ommaensis (Otuka), Omma
Area, Omma Sandstone; 3, Macoma tokyoensis Makiyama, Omma Area, Omma Sandstone; 4, Mercenaria
stimpsoni (Gould), Gojome-Oga Area, Sasaoka Formation; 5, Protothaca adamsi (Reeve), Gojome-Oga
Area, Sasaoka Formation; 6, Gfycymeris yessoensis (Sowerby), Omma Area, Omma Sandstone; 7, Fefanieffa usta (Gould), Omma Area, Omma Sandstone. All in natural size.

654

Seiichiro Matsui

Thyasira Association Group910.

Plio-Pleistocene molluscan associations

Acila-Turritella Association Group have been
extinct. However, congeneric species ofthese extinct forms are living lower sublittoralzone.
The lower sublittoral fauna off Kushiro ineastern Hokkaido (Matsui, 1985c) is predominated by cold water species. Macoma
calcarea and Turritella Jortilirata of thisfauna are the species common to the fossil
Acila-Turritella Association. Clinocardium
cilia tum (Fabricius) living in this fauna isclosely related with Clinocardium chikagawaense in the fossil association.
The muddy lower shelf fauna of about 40
to 200 m deep in Sagami Bay is composed ofbivalves of Glycymeris rotunda, Venus
Joveolata Sowerby, Acila divaricata, Angulus
vestalioides (Yokoyama) and various gastropod species (Horikoshi, 1957). The fauna
is living in the warm water. Among them,G. rotunda and A. divaricata appear in thefossil Acila-Turritella Association in the
Omma.
Anadara Association Group (Figure 4)
Local associations included in this groupare found in fine-grained sandstone. They
are characterized by common occurrences of
Anadara amicula or Scapharca spp., associated with large suspension-feeding bivalves of Dosinia tomikawensis Takagi, Mercenaria stimpsoni (Gould), Protothacaadamsi and deep-burrowing Macoma tokyoensis. Turritella saishuensis and Macoma
calcarea are also found in these associations.
The Protothaca Association of the Gojome-Oga and the Anadara Association of the
Ishikari-Numata are representatives of thisgroup of associations. Anadara amicula,
Mercenaria stimpsoni, Protothaca adamsi
and Macoma calcarea are common in these
two associations, and the association in
the Ishikari-Numata accompanied with For-655

tipecten takahashii.
The Macoma tokyoensis Association of the
Gojome-Oga and the Turritella saishuensisMacoma tokyoensis-Mercenaria Associationof the Futatsui are dominated by Macoma
tokyoensis and Turritella saishuensis, containing Anadara and Mercenaria as subordinate elements.
Two associations characterized not by
Anadara but Scapharca species appear in theOmma. The Scapharca pseudosubcrenata
Association contains S. pseudosubcrenata, S.
aff. ommaensis and Macoma tokyoensis, notassociated with other large suspensionfeeding bivalves. The Scapharca ommaensis Association is known from only one locality of the same area. At this locality S.
ommaensis is very abundant and represents a
distinct molluscan association.
The Pseudamiantis-Anadara Associationin the Pliocene Sendai basin is dominated by
Pseudamiantis sendaicus (Nomura), Anadara tatunokutiensis (Nomura and Hatai),
Dosinia tatunokutiensis (Nomura) and Fortipecten takahashii, found in poorly-sorted,
medium- to coarse-grained sandstone (Chinzei and Iwasaki, 1967). The similar association found from poorly-sorted, fine- tocoarse-grained sandstone, in the Pliocene
Sannohe basin (Chinzei, 1961), is composedof Anadara tatunokutiensis nagawensis
Chinzei, Dosinia tomikawensis, Mercenaria
stimpsoni, Fortipecten kenyoshiensis (Chinzei)
and some others. These two associations
represent this association group in the Tatsunokuchi Fauna.
The Anadara Association Group represents the shallowest environment among
others. This is found from the sandy sediments of the last stage of regressive marine
sequences in the Futatsui and Gojome-Oga(Chinzei, 1973; Matsui, 1985a). The Ana-

~ Figure 5. Major faunal elements of the Thyasira and Chlamys Association Groups. 1, Thyasirabisecta (Conrad), Taihei Area, Tentokuji Formation; 2, Lucinoma acutilineata (Conrad), Taihei Area,
Tentokuji Formation; 3, Tridonta alaskensis (Dall), Hamada Area, Hamada Formation; 4, Chlamys
cosibensis (Yokoyama), Hamada Area, Hamada Formation; 5, Yabepecten tokunagai (Yokoyama),
Hamada Area, Hamada Formation. All in natural size.

656

Seiichiro Matsui

dara Association in the Ishikari-N umata
occurs at the top horizon of marine sediments, dominated with sand and covered with
peat-bearing non-marine sediments. The
Pseudamiantis-Anadara Association in the
Sendai basin is found in a marginal sandy
area of the basin (Chinzei and Iwasaki, 1967).
The Anadara Association Group is analogous to the living upper sublittoral fauna ofsandy substrata shallower than about 40 m
(Chinzei and Iwasaki, 1967). The living
fauna contains many species common to thefossil associations. Large and thick-shelledsuspension-feeding bivalves of Dosinia japonica (Reeve), Protothaca adamsi and Mercenaria stimpsoni are commonly found in theupper sublittoral fauna of Sendai Bay(Masuda et al., 1983). Scapharca broughtonU (Schrenck) and S. subcrenata (Lischke)are living representatives of Anadarinae inthe place of Anadara amicula of the fossil
associations.
The cold water fauna of the upper sublittoral zone off Kushiro is found from rocky orfine- to coarse-grained sandy bottom shallower than 30 m deep. Common species ofthis fauna are Clinocardium nuttallii (Conrad), Protothaca adamsi, Mercenaria stimpsoni, Glycymeris yessoensis (Sowerby),
Macoma calcarea and Felaniella usta (Matsui, 1985c; Habe, 1955). These species areaccompanied by large buccinid whelks suchas Buccinum middendorffi Verkruzen and
Neptunea arthritica (Bernardi).
The sandy fauna of the upper sublittoralzone in Sagami Bay (Horikoshi, 1957) contains species congeneric to those in the fossil
Anadara Association Group, such as
Glycymeris albolineata (Lischke) and Dosinia
japonica (Reeve). This living fauna, however, lacks cold water species such as Protothaca adamsi and Mercenaria stimpsoni.
Species of Anadarinae of this fauna is Scapharca satowi (Dunker).
Macoma-Mya Association Group
The Macoma-Mya Association, whichappears in the central silty part of the Sendai

basin, may represent another associationgroup lived in the shallow muddy bottom
adjoining to the sandy habitat of the Anadara Association. This association is composed of Macoma tokyoensis, Mya japonica
Jay and Lucinoma annulata (Reeve), which
sporadically occur in the dark-gray massive
silt (Chinzei and Iwasaki, 1967).
Living fauna comparable with the fossil
Macoma-Mya Association is found in theupper sublittoral zone of muddy bottoms(Chinzei and Iwasaki, 1967).
Thyasira Association Group (Figure 5)
This is typically found in the Gojome-Oga
and Taihei Areas as the Thyasira bisecta
Association (Matsui, 1977 MS, 1985a). This
association is peculiar in species composition
and mode of occurrence as described by
Matsui (l985a) in detail. The association ismainly composed of lucinacean bivalves,
Thyasira bisecta with less abundant Lucinoma acutilineata, occasionally accompaniedwith Acharax tokunagai (Yokoyama), Acilanakazimai and some others as rare components. The two dominant species are usuallyfound conjoined in standing position. Since
this association often occurs stratigraphicallyclose to the Nuculana Association and sometimes to the Acila-Turritella Association in
the Gojome-Oga and Taihei, the Thyasira
Association had a depth preference similar to
the Nuculana Association and presumably
extended up to a deeper part of the habitat of
the Acila-Turritella Association. The
Thyasira Association, however, has wider
tolerance for sediment types than the
Nuculana Association. It occurs in muddy,
sandy and pebbly sediments (Matsui, 1985a).
In the Futatsui, Thyasira occurs in the muddy
and sandy associations as a rare element, but
no assemblage composed dominantly ofThyasira and Lucinoma has been known(Chinzei, 1973). This weak relationshipbetween the Thyasira Association and sediment type exhibits a contrast with theconfinement of the other association groups
to the particular sediment types.

910.

Plio-Pleistocene molluscan associations

Lucinacean bivalves including the genera
Thyasira and Lucinoma as well as solemyidbivalves have symbiotic sulfide oxidizing
bacteria in their gills (e.g., Reid and Brand,1986). The nutritional dependence on thesymbiotic bacteria and other anatomical features (Allen, 1958) indicate that these bivalvesadapt to oxygen-deficient, sulfide-rich sediments, which are not suitable for other ordinary benthic animals. The distribution of
the Thyasira Association may be controlled
mainly by the reducing environments rather
than grain size of sediments or hydrodynamic
condition.
Thyasira bisecta is known from the upper
bathyal zone around Japan (Kanno, 1971).
The species is very rarely collected from thepresent sea bottoms in spite of the ubiquitous
occurrence of the fossils, probably owing to
the deep-burrowing habit.
Chlamys Association Group (Figure 5)
This is represented by the Chlamys Association of the Hamada. As noted in thedescription of the Hamada Area, some
pectinid species and other epifaunal or
shallow-burrowing bivalves characterize thisassociatIOn. Some assemblages from granule-bearing sandstone and siltstone in the
Pliocene-Pleistocene Daishaka Formation of
the Daishaka are rich in the species of theChlamys Association such as Chlamys spp.,
Polynemamussium alaskense, Cyclocardia
ferruginea and Tridonta alaskensis (Tabuki,1983).
Some representative species of the Chlamys
Association such as Cyclocardia ferruginea
and Polynemamussium alaskense appear in
the sandy assemblage of the Acila-Macoma
Association in the Hamada. Similar intermediate assemblages between the Chlamys
and Acila-Turritella Association Groups havebeen found in the Daishaka (Tabuki, 1983).
The Chlamys Association Group occasionally contains the characteristic constituents of
the Nuculana Association Group such as
Neptunea spp. and Nuculana robai. Thesesuggest that the Chlamys Association Group657

is preferred water depth similar to, but coarser
substrate than the Acila-Turritella Association Group and presumably extended to deep,
but coarse-grained sand bottoms adjoining to
the muddy habitat of the Nuculana Association Group.
The transported assemblages of the Sado
Area contain many characteristic species of
the Chlamys Association such as Chlamys
cosibensis and Yabepecten tokunagai. Other
constituents of the assemblages are small
gastropods and byssally attaching epifaunal
bivalves, which prefer coarse-grained bottoms. This implies that these transported
assemblages rarely include elements derived
from other biotopes. Such transported
assemblages dominated by pectinid bivalves
are common in the Pliocene-lower Pleistocene in Northeast Japan; for example, theHaizume Formation in the Nishiyama (Kanehara, 1950) and the Simazaki Shell Bed in theHimi (Otuka, 1935).
The living coarse-grained bottom faunas in
the lower sublittoral and upper bathyal zones
are different from the muddy bottom faunasof the same zones, composed mainly ofChlamys and other epifaunal species, comparable to the fossil Chlamys Association
Group. Cryptopecten vesiculosus (Dunker),
Neopycnodonte musashiana (Yokoyama),
Xenophora pallidula (Reeve) are common on
the sandy to gravelly lower shelf of Sagami
Bay (Horikoshi, 1957). Chlamys islandica
and other epifaunal animals such asbryozoans are living in the lower shelf off
Kushiro on medium-grained sandy bottom
with boulders (Matsui, 1985c). The upper
bathyal fauna is mainly composed ofChlamys isla n dica, Polynemamussium a laskense, various species of buccinid and turrid
gastropods (Matsui, 1985c). Polynemamussium alaskense is abundantly found on thesteepest part of the upper slope between 150
to 200 m deep just below the shelf edge.

Seiichiro Matsui

658

BOTTOM

CHARACTER
coarsefine

Macoma-Mya

:::t

I-

Ao

1&1

Q
1&1

>
le

"""

1&1

a.:

1l0li0ii0i1 .... -c.

-Thyasira --.......

CI)
CI)"
Figure 6. Schematic summary of relation between the association groups and environments expressed in terms of relative water depth and bottom character.

Summary
Late Cenozoic cold water molluscan associations in Japan are grouped into the sevenassociation groups. The associations
belonging to one of these groups are similar
to each other not only in species or genus
composition but also in environmental preference, though their occurrences are scatteredover the interval of approximately 5 million
years. The associations are in ecologicallyparallel relationships with each other. The
distribution of the association groups is concluded to have been controlled mainly bywater depth and bottom character (Figure 6).
There are comparable living benthic molluscan associations around Japan ranging fromthe bathyal to upper sublittoral zones. The
following is characteristics of the associationgroups.
(I) The Delectopecten Association Groupis monospecific, composed of Delectopecten
peckhami. This is found in the deepest
muddy environment. Comparable thinshelled pectinid fauna is known from thebathyal zone.
(2) The Nuculana Association Group isdominated by nuculanid bivalves and carnivorous gastropods such as buccinid species.
This group occupies a deep muddy environment but shallower than that of the Delectopecten Association Group. Similar living
nuculanid and buccinid faunas are commonly
found in the muddy upper bathyal zone.
(3) The Acila-Turritella Association
Group is the commonest type of associations
among the latest Miocene to early Pleistocene
faunas in Northeast Japan. Various suspension- and deposit-feeding bivalves such as
Clinocardium, Macoma and Mya besides
some species of Acila and Turritella prevail in
the group. This group appears in silty and910.

Plio-Pleistocene molluscan associations

fine-grained sandy sediments representing anenvironment shallower than that of the
Nuculana Association Group. The faunas
on silty and sandy bottoms of the lower
sublittoral zone are comparable with thisgroup.
(4) The Anadara Association Groupappears in the shallowest sandy environment,
composed of Anadara, Scapharca and otherlarge suspension-feeding bivalves. Sandy
molluscan faunas of the upper sublittoralzone are the living analogue of this group.
(5) The Macoma-Mya Association
Group was a dweller on shallow muddy
bottoms adjoining the sandy environment of
the Anadara Association Group.
(6) The Thyasira Association Group iscomposed of Thyasira bisecta and Lucinoma
acutilineata. This group had a broad tolerance to substrate types but might be restricted
to a reducing environment. This had adepth preference similar to the Nuculana
Association Group.
(7) The Chlamys Association Group iscomposed of epifaunal and shallowburrowing bivalves. This occupied coarse
sand bottoms adjoining to the finer bottoms
inhabited by the Acila- Turritella andNuculana Association Groups.
These association groups show geographic
and historic changes of composition in
species level, though the genus compositions
have remained unchanged. The geographic
replacement of species within the same genus
is exemplified by Turritella in the AcilaTurritella Association Group. This difference may be due to biogeographic provincialism. The Anadarinae of the Anadara Association Group is occupied by Anadara
amicula from the Pliocene through earlier
Early Pleistocene, whereas replaced withsome species of Scapharca in the late Early
Pleistocene Omma fauna. The historicchanges of the cold water faunas during the
Pliocene and Pleistocene will be discussed inanother article (Matsui, in prep.).

659

Acknowledgments

I am grateful to Professors K. Chinzei(Kyoto University) and I. Hayami (Universityof Tokyo), and Emeritus Professor T. Hanai(University of Tokyo) for their advice andencouragement. This paper is based on a partof the dissertation written under their guidance. Dr. H. Kitazato (Shizuoka University)and Professor T. Takayama (Kanazawa University) kindly identified microfossils andgave interpretation of the age assignment of
the strata. Much appreciated help andadvice in the field were provided by Drs. T.
Yamaguchi (Chiba University), R. Tabuki(Ryukyu University), T. Ito (University ofTokyo) and Mr. I. Hosoda. Mr. A. Kitamura(Kanazawa University) kindly gave information on stratigraphy of the Omma section.
Reviews by K. Chinzei significantly improved
the quality of the final manuscript. This
study was financially supported by the
Grant-in-Aid for Scientific Research from the
Ministry of Education, Science and Culture(grant 58740382, grant 61740457).
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sedimentary basin-. Jour. Japan. Assooc. Petrol. Technol., vol. 53, no. I, p. 9-27. (in Japanesewith English abstract)
Takayasu, T. and Yunohara, N., 1977: Distributionof Recent molluscan shells off Oga Peninsula,
Akita Prefecture, Japan. In, Takayasu, T., ed.,Professor Kazuo Huzioka Memorial Volume,
Akita, p. 385-400. (in Japanese with English

abstract)
Thorson, G., 1957: Bottom communities (sublittoralor shallow shelf). In, Hedgpeth, J.W., ed.,Treatise on marine ecology and paleoecology I,
Geol. Soc. A mer., Mem., no. 67, p.461-534.
Uozumi, S., 1962: Neogene molluscan faunas in
Hokkaido. Part I. Sequence and distribution of
fauna. Jour. Fac. Sci. Hokkaido Un iv, Ser. IV,
vol. II, no. 3, p. 507-544.
Utashiro, T., 1957: On some Palliolum peckhami inJapan - Studies on Japanese Palliolum peckhami,
Part II. Mem. Takada Branch, Fac. Educ.,
Niigata Univ., no. 1, p. 161-174, pIs. 1-4. (inJapanese with English abstract)- - , Kuroda, K., Kobayashi, T., Nishikawa, M.,
Hasegawa, Y., Fujita, T. and Watanabe, H.,
1977: Tertiary stratigraphy and diatoms at the
Sawada area, Sado Island, Niigata Prefecture,
Japan. Publ. from the Sado Museum, no. 7, p.
45-62, pis. 1-4. (in Japanese with English

abstract)
Walker, K. R. and Laporte, L. F., 1970: Congruent
fossil communities from Ordovician and
Devonian carbonates of New York. Jour.
Paleont., vol. 44, no. 5, p. 928-944.
Yamaguchi, T., 1970: The Neogene of the northeastern part of the Shimokita Peninsula, Northeast
Honshu, Japan - On the stratigraphic relation of
the Tomari, the Gamanosawa and the"Sunagomata" Formations-. Jour. Geol Soc.
Japan, vol. 76, no.4, p.185-197. (in Japanesewith English abstract)=- *.

Chikagawa JlI)[ I. Daishaka~~. Futatsui'Y
Gojome Ii:!lilt §. Hamada ~ B3,
Higashimeya JIU3~, Himi 7.1<~, Ishikari-Numata :o~mB3, Kaidate j"j,.ll., Kamiiso J:.~.

Seiichiro Matsui

662

Kushiro ~II~. Maekawa iltrJII. Nishiyama i1.§il.l. Oga ~I.l. Omma *~. Sado {tj:~. Sagami;f§~. Sannohe
Sendai 1t11-Ei'. Setana ifJiWl. Shichiba ftlli. Taihei *3f. Tsubata J!I!:~. Uonuma ~jg •:=.p.

.:p~t$ B*O)ffm- ~mi!t.F!.Mft~:&lf-t-0)~!'1U: 0)1*lf*: B*O).:pmi!t*:MiJ' i?~m
i!ttc:&..s;*9 500 711f.rl3'0)*VlE*.F!.Mfb4o/J~.:ptc 7 '0O)ft~O)?' Iv - 7'iJ~~.lO i?nko -t- n-F nO)?' Iv - 7'z.~Rlt-t Gjfu~ft~f;t:to1LHcfl i t.:f;t~mRlto).lj. t.c i?f~~ C0)1*lf* ~Mi!:L 1..., :to1LHc~~Et:J3frrO)I*lf*tc~ Go ~~O)?, Iv - 7'O):5t;ffH;t±:tc*i~IU: llfttcm~~nGo ik,~ni?O)ft~o)?'~-~K~~-tG.~O)ft~~B*.m • • K~.lOi?
nG o 7 '00)?' Iv-7'O)t.ciJ'''l: Acila-Turritella ft~iJ~JI~~J.liiEt:J"l:, .~O)r$~l'lMl'fft~tcJ:ttl~ nG o Delectopecten ft~ C Nuculana ft~f;t ~ n J: 9 i'5!11\,,~~tc~.lO i? n Go
Anadara ft~ C Macoma-Mya ft~f;t~.~~z.f\;~ 1..., -t- n-F nJ::$~.*O)1i'Yll c i'JE
llft~ tcJ:ttl ~ n Go Thyasira ft~ f;tji:J[; Et:J t.c ~~ c t.!i If '0 \" -c \" t.: c ~ ;:t i? n Go
Chlamys ft~f;tr$~.*:&lf J::$i!Wii'5!11.*O)m*-lL1i'Yllz.f\;;~-t Go
mJiS~-tl~

Trans. Proc. Palaeont. Soc. Japan, N.S., No. 160, pp. 663-673, 7 Figs., December 30, 1990

911.

A NEW GENUS OF THE TREMATOPHORATE MILIOLIDS(FABULARIIDAE) FROM THE EOCENE SETOGAWAGROUP, SOUTHWEST JAPAN*
KUNITERU MATSUMARU
Department of Geology, Faculty of Education,
Saitama University, Urawa 338

Abstract. This paper deals with the description and illustration of a new genus of thetrematophorate miliolids (Fabulariidae), Neolacazopsis osozawai, n. gen., n. sp., from thebasaltic and calcareous sandstone of the Eocene Setogawa Group, at Ashikubo-Okugumi,
Shizuoka City and at Hasama, Okabe-Cho, both of Shizuoka Prefecture, Japan.
Key words.

Neo/acazopsis osozawai, Eocene, Setogawa Group, Shizuoka Prefecture.

benthic and planktic foraminifers, calcareous
algae, bryozoan, molluscs, echinoids andothers.
According to the recent stratigraphical andtectonical studies of Osozawa (1988), the areaof the two fossil localities is constituted of the
Eocene to lower Miocene Setogawa Group,
which consists of pelagic, hemipelagic, andterrigenous sediments with volcanic intercalations. The basaltic and calcareous sandstoneof the stratigraphic sequence of the Setogawa
Group includes fragments of basalt and limestone. On the whole, Osozawa (op. cit.)
considered the Setogawa Group to be an
accretionary complex on the basis of theoccurrences of pelagic sediments on land,
repeated stratigraphic sequence caused byreverse faulting and asymmetric folding.
Sugiyama and Shimokawa (1981) considered
the fossil-bearing limestone to be a special
lithology of biosparite in the uppermost partof the Takisawa Formation, Setogawa
Group. Formerly, Ishii and Makino (1946)
found Discocyclina from the limestone of the
Setogawa Series and regarded to be of theDanian to Upper Eocene. Recently, Ibaraki(1984) regarded the limestones of the Setog-

Introduction

In 1989, Soichi Osozawa, Institute of Geology and Paleontology, Tohoku University,
discovered two new localities of larger foraminifer bearing-limestone at AshikuboOkugumi, northwest of Shizuoka City andHasama, northwest of Okabe-cho, both of
Shizuoka Prefecture, and kindly sent the fossil materials to the author for study (FigureI). Afterwards, the author visited Osozawa's
fossil localities with author's working groupin order to gather a number of fossil materials
and to get the stratigraphical information.
At Ashikubo-Okugumi locality, the fossilbearing limestone samples were taken as arolling stone of boulder sized limestone conglomerates from the Setogawa Group. Samples at Hasama locality were taken directlyfrom the basaltic and calcareous sandstone
exposure of the Setogawa Group. Both samples from the two localities treated in thispaper were studied in detail and they were thesame limestone, which contains the trematophorate miliolids (Fabulariidae), other"Received February 9, 1990; revised manuscript
accepted October 27, 1990
663

Kuniteru Matsumaru

664

Japan

~~--+----;~-3~

1360

1380

1400

34'55'43'-'------'"......
13815'15/1

ob'======d'5______..10Km'

I

Surugo Boy

Figure I. Map showing the fossil locality of the studied area, Shizuoka Prefecture. Vertical lines
represent the distribution of the Setogawa Group. S.r.f.: Sasayama reverse fault, J.r.f.: Jyumaiyama
reverse fault, I.r.f.: Itoigawa-Shizuoka reverse fault.

awa Group to be assigned to the Middle toLate Eocene (Blow's Zone of Pl2 to P16)
based on planktic foraminifers. As can beseen in Figure 4-1, it is obvious that the ageof the fossil-bearing limestone is younger
than the Middle Eocene based on the presence of Triloculina, ranging from the Middle
Eocene to Holocene (Loeblich and Tappan,
1988).
The purpose of this paper is to make thefirst description and discussion of the new
type forms of the trematophorate miliolids inJapan, and to propose a new genus name
Neolacazopsis for new type ones, taking
Neolacazopsis osozawai, n. gen., n. sp., as thetype species.

Systematic description
Superfamily Alveolinacea Ehrenberg, 1839
Family Fabulariidae Ehrenberg, 1839
Genus Neolacazopsis Matsumaru, n. gen.
Type

species. - Neolacazopsis

osozawai---+ Figure 2. Neolacazopsis osozawai Matsumaru, n. gen., n. sp. All figures X 15, except X 50 of 2b ;Locality 2. la-b, 2a, lateral views of parts of specimens; Ie, 2b, horizontal views, showing the external
shape and arrangement of chamberlets; Id, Inside of la, showing the arrangement of epidermal chambers
and their chamberlets.

911.

A new genus Neolacazopsis from Japan

665

666

Kuniteru Matsumaru

Figure 3. Neolacazopsis osozawai Matsumaru , n. gen., n. sp. Equatorial section of a microsphericspecimen , holotype, Saitama University, Coli. no. 8804, X 10; Locality I.
~
Figure 4. Neolacazopsis osozawai Matsumaru, n. gen. , n. sp. All figures X 20, except X 40 of Ib;
Locality I. I, 3, Equatorial sections of both megalospheric specimen (I) and microspheric one (3); Ib,
Enlarged twice la, showing the large proloculus, which includes Triloculina cf. subvalvularis Parr, followedby chambers in biloculine arrangement. Paratype, Saitama University, ColI. no. 8805 ; 2, Oblique sectionof a megalospheric specimen.

911.

A new genus Neolacazopsis from Japan

667

Kuniteru Matsumaru

668

Matsumaru, n. sp.
Diagnosis.-Test large, elongate ovate inoutline; large proloculus followed by chambers in biloculine arrangement in megalospheric form, microspheric test with quinqueloculine at first stage, then triloculine tobiloculine, adult of both generations hascompletely enveloping biloculine chambers
added alternately from pole to pole, thenfollowed by enveloping epidermal chambers;
biloculine and epidermal chambers subdivided into arcuate to turtle-neck bottle-like form
chamberlets by longitudinal and transverse
interseptal partitions and pillars among congregations of previous both partitions; wallcalcareous, porcellaneous, with thick andfinely to coarsely alveolar inner layer, outerlayer thin and finely to coarsely perforate,bilamellar; aperture terminal, with a trematophore-like elongate arcuate shape bearing numerous irregular openings separated byanastomosing denticulations or cribrate.
Comparison. - The present genus resembles
Lacazopsis H. Douville 1930, but is distinguished from the latter by having calcareousand porcellaneous wall of test, andtrematophore-like aperture. Lacazopsis wasclassified as one of the genus in the Subfamily
Fabulariinae Ehrenberg, 1839, of Family
Miliolidae Ehrenberg, 1839 by Loeblich andTappan (1964), but they (1988) rejected Lacazopsis as one of the genus taxa erroneously
regarded as foraminifers, because of a taxonof an encrusting cheilostome bryozoan.
Neolacazopsis also resembles Lacazina
Munier-Chalmas, 1882, but is distinguishedfrom the latter by having an elongate arcuate
shape aperture and trematophore, and byhaving alveolar wall in early stage in microspheric form.
Neolacazopsis osozawai Matsumaru, n. sp.
Figures 2-7

Type material. - Holotype, equatorial section of microspheric specimen, Saitama Uni-

versity ColI. no. 8804 (Figures 3, 4-3). Paratype, equatorial section of megalosphericspecimen, Saitama University ColI. no. 8805
(Figures 4-la- b).
Description. - The microspheric specimens(Figures 3, 4-3, 5, 6, 7) are large elongate
ovate test with diameter of 17 to 35 mm, andthickness of 13 to 20 mm. The megalospheric specimens (Figures 4-1-2) are small ovate
test with more than 4 mm in diameter andmore than 2.2 mm in thickness in some broken specimens. Surface bears widely reticulation, which represents the surface expressionof the chamberlet sutures of test walls. The
diameter of chamberlet on surface is 100 to
200 Jlm. The first stage of quinqueloculine
chambers in microspheric form has outer
diameters of 560 to 580 Jlm. The second
stage of triloculine chambers, which embrace
the quinqueloculine, has outer diameters of
750 to 1150 Jlm. The large megalosphericproloculus is subspherical, with inner diameters of 376 X 306 Jl m. The early chambers ofboth microspheric and megalospheric forms
are followed by arcuate to elongate arcuate
biloculine chambers added alternately frompole to pole of test, and by elongate arcuate
epidermal chambers. The main biloculine
chambers in microspheric form in transverse
section are with radial diameters of 370 to 380
Jlm and tangential diameters of 1.2 to 2 mmnear the triloculine chambers to radial diameters of 270 to 300 Jlm and tangential diameterof 8 to 10 mm near the peripheral part of test.
Biloculine and epidermal chambers are subdivided into arcuate to turtle-neck bottle-likeform chamberlets by longitudinal and transverse interseptal partitions and pillars. Typical chamberlets with dimension of 170 X 357,
204 X 408, 238 X 408, 306 X 300 , 510 X 272 and544 X 272 Jl m in inner radial and tangential
diameters. The wall calcareous and porcel1aneous, thick and finely to coarsely alveolar
inner layer, outer layer thin and finely tocoarsely perforate bilamellar, measuring
thickness of 100 to 238 Jlm near the center to
60 to 100 Jlm near the periphery. The aper-

91 I.

A new genus Neolacazopsis from Japan

Figure 5. Neolacazopsis osozawai Matsumaru, n. gen ., n. sp. Tangential section of a microsphericspecimen, showi ng the trematophorate aperture (arrow) and completely enveloping biloculine and epidermal chambers, X 15 ; Loca lity 2.

669

670

Kunileru Matsumaru

Figure 6. Neolacazopsis osozalVai Matsum aru , n. ge n., n. sp. Tra nsverse secti o n of a mi cros phericspecime n, show in g a rc uate to turtl e-nec k bo tt le-like fo rm cha mberl ets, X 15 ; Loca lity I.

911.

A new genus Neolacazopsis from Japan

Figure 7. Neolacazopsis osozawai Matsumaru , n. gen ., n. sp. la, Enlarged of Figure 6 X 48,
show ing chambers near centre in triloculine arrangement in a microspheric ge neration, and showing the
wa ll with coarsely alveolar inner layer ; lb, En larged Figure 6 X 24, showing chambers from triloculine
to biloculine arrangement, added from pole to pole.

671

Kuniteru Matsumaru

672

ture at the base of the preceding chamber intangential section consisting of trematophorewith irregular openings (Figure 5).
Locality. - Locality I is a tributary river ofthe Ashikubo River, at the opposite side of
Ashikubo-Okugumi, Shizuoka City (35"3'38"
N. Lat., 138'19'43"E. Long.) and locality 2 isa tributary river (Kamiiri-sawa) of the Asahina River at the opposite side of Hasama,
Okabe-cho, Shida-Gun (34'55' 43"N. Lat.,138'15'15"E. Long.), both ofShizuoka Prefecture (Figure I).
Stratigraphical horizon. - Basaltic and calcareous sandstone, Setogawa Group or Takisawa Formation, Setogawa Group.
Geological age.-Middle to Late Eocene.
Remarks.-Neolacazopsis osozawai, n. sp.
resembles Lacazopsis termieri H. Douville,
1930 from the Upper Cretaceous (Senonian)in Morocco, northwest Africa, but is distinguished from the latter by having calcareousand porcellaneous wall of test, turtle-neckbottle-like chamberlets, alveolar inner walland trematophore-like aperture. The present
new species differs from Lacazina compressa(d'Orbigny) var. galloprovincialis MunierChalmas and Schlumberger, 1885 from theSenonian, Martigues, France in having
turtle-neck bottle-like chamberlets and alveolar inner wall instead of arcuate chamberlets
and imperforate inner wall.
Acknowledgment

The appreciation is due to Dr. Soichi Osozawa, Institute of Geology and Paleontology,
Faculty of Science, Tohoku University, for
his kind offering the fossil materials. Deep
appreciations are due to Professor Sumio
Sakagami, Department of Geology, Facultyof Science, Chiba University, and Mr.
Naotomo Kaneko, Institute of Geology andPaleontology, Faculty of Science, Tohoku

University, for their kind discussion of a
Cheilostome bryozoan. Thanks are due to
Mr. Hirokazu Asano, Department of Geology, Faculty of Education, Saitama University, for his kind making up of thin sections.
References
Douville, H., 1930: Une Miliolidee geante duSenonien du Maroc Lacazopsis termieri. Soc.
glol. France, Bull., Ser. 4, vol. 29, nos. 3-5(1929), p.245 -250, pI. 21.
Ehrenberg, C. G., 1839: Uber die Bildung derKreidefelsen und des Kreidemergels durch unsichtbare Organismen. Physik. Abhand. Konig.
Akad. Wissensch. Berlin, 1838 (1840: separate
1839), p. 59-147.
Ibaraki, M., 1984: Middle-Late Eocene planktonic
foraminiferal faunas from limestones of the
Setogawa Group, central Japan. Trans. Proc.
Palaeont. Soc. Japan, N.S., no. 135, p.401-414,
pis. 77-79.
Ishii, M. and Makino, T., 1946: On the Discocyclina
from the Setogawa Series. Jour. Geol. Soc.
Japan, vol. 52, no. 610-612, p.610-612. (inJapanese)
Loeblich, A. R. and Tappan, H., 1964: Sarcodina,chiefly "Thecamoebians" and Foraminiferida.
p. CI-C900. In, Moore, R. c., ed., Treatise on
Invertebrate Paleontology. Protista 2, vols. 1-2,
Univ. Kansas Press and Geol. Soc. America,
Colorado.
- - , 1988: Foraminiferal genera and their classification. 970 p, 847 pIs. Van Nostrand Reinhold Co. Inc., New York.
Munier-Chalmas, E., 1882: Un genre nouveau deforaminiferes Senoniens. Soc. glo/. France,
Bull., Ser. 3, vol. 10 (1881-82), p.470-471.
- - and Schlumberger, c., 1885: Note sur lesMiliolidees trematophorees. Ibid., vol. 13(1884-85), p. 273-323, pIs. 13-15.
Osozawa, S., 1988: Accretionary process of the Tertiary Setogawa and Mikasa Groups, southwest
Japan. Jour. Geol., vol. 9, p. 199-208.
Sugiyama, Y. and Shimokawa, K., 1981 : A paleogeographic study of the Paleogene Setogawa Group,
Shizuoka Prefecture, central Japan. Jour. Geol.
Soc. Japan, vol. 87, no. 7, p. 439-456. (inJapanese with English abstract)

911.

A new genus Neolacazopsis from Japan

Ashikubo-Okugumi JE~i*!!IUII, Hasama :g:H3::Fa', Okabe-Cho 1lliI$1IlJ, Setogawa ifjp)ll,
Takisawa iltiR, Kamiiri-Sawa fItlAiR, Asahina ~Jt~, Shida-Gun $:;t:ms.

ifJip )11!iftii' G~ Trematophorate miliolids (Fubulariidae M) ~ I !i1i'&: ~1lliI1)jl,~llliIm~tg§~JE~i*~m:to.J: rflRJl)jl,;tr::;tmlllil$1IlJ3f.lt£Fa'~fItlAiR~ifJipJll!ift:1'.:iit!B~EWZ~-li')!BiI' G, ~!i1i'i!t~-:f&:M~ trematophorate miliolids (Fubuloriidae M) ~ I !i1i'& ~96~ 1.....,~tJ(; 1..... t.:o -t.nf1.~iRtt-~iI· G*7i1f~~mt~~~t.:~i*iI· G, Neolacazopsis osozawaicMatsumaru, n. gen., n. sp. 1'fa"15 1..... t.:o .: ~!i1i'&:m:fmf1. Lacazopsis & (H. Douville, 1930):to.J: rf Lacazina & (Munier-Chalmas, 1882) t.:.;Q:1J;J. 1....., ~H!IIt.:.Jt~~W 1..... t.:o 101LOOWil

673

674

SYSTEMATIC INDEX(New Series No. 153-No. 160)
PALAEOZOOLOGY

Protozoa
Page
Hori, Rie: Lower Jurassic radiolarian zones of southwest Japan ................ 562
Matsumaru, Kuniteru: A new genus of the miogypsinid foraminifer from southwest
Japan .............................................................. 535
Matsumaru, Kuniteru: A new genus of the trematophorate miliolids (Fabulariidae)
from the Eocene Setogawa Group, Southwest Japan .................... 663
Matsumaru, Kuniteru and Kimura, Koshi: Larger foraminifera from the Eocene
Shimizu and Miocene Misaki Formations in Tosa Shimizu City, Kochi
Prefecture, Japan .................................................... 255
Matsumaru, Kuniteru and Sakai, Harutaka: Nummulites and Assilina from Tansenarea, Palpa district, the Nepal Lesser Himalayas ........................ 68
Matsuoka, Hiromi: New method to evaluate dissolution of CaCOa in the deep-sea
sediments .......................................................... 430
Nagai, Hiromi and Mizutani, Shinjiro: Jurassic Eucyrtidiellum (Radiolaria) .... 587
Nishi, Hiroshi; Yokota, Satoshi and Saito, Tsunemasa: An Early Cretaceous (early
Middle Albian) planktonic foraminiferal fauna from the Hinagu Formationof Northern Kyushu, Japan ......................................... .
Nomura, Ritsuo: Late Middle Miocene foraminifera from the Matsue Formation,
Shimane Prefecture .................................................. 459

Mollusca
Chiba, Satoshi: Taxonomy and morphologic diversity of Mandarina (Pulmonata)in the Bonin Islands ................................................ 218
Ehiro, Masayuki and Takizawa, Fuminori: Foordiceras and Domatoceras(nautiloid cephalopods) from the Upper Permian Toyoma Formation, southern Kitakami Massif, northeast Japan .................................. 212
Hirano, Hiromichi; Okamoto, Takashi and Hattori, Khoji: Evolution of some
Late Cretaceous desmoceratine ammonoids ............................ 382
Kanno, Saburo; Amano, Kazutaka and Ban, Hiromitsu: Calyptogena(Calyptogena) pacifica DaB (Bivalvia) from the Neogene System in the Joetsu
674

675

district, Niigata Prefecture
25
Kozai, Takeshi: A study of Corbula and Nipponicorbula (Bivalvia) from the36
Cretaceous of Japan
Matsui, Seiichiro: Pliocene-Pleistocene molluscan associations in north-central
Japan and their relationship to environments
641
Matsumoto, Tatsuro: Some inoceramids (Bivalvia) from the Cenomanian(Cretaceous) of Japan - Vo A world-wide species Inoceramus pictus Sowerby from Japan
12
Matsumoto, Tatsuro: An interesting pachydiscid ammonite from Hokkaido, withremarks on relevant taxa (Studies of Cretaceous ammonites from Hokkaido LXVII)
618
Matsumoto, Tatsuro and Asai, Akito: Cenomanian (Cretaceous) inoceramids(Bivalvia) from Hokkaido and Sakhalin I. Birostrina nipponica (Nagao et
178
Matsumoto)Matsumoto, Tatsuro; Nemoto, Mamoru and Suzuki, Chisato: Gigantic ammonites
366
from the Cretaceous Futaba Group of Fukushima Prefecture
Matsumoto, Tatsuro; Toshimitsu, Seiichi and Kawashita, Y oshitaro: On
Hauericeras de Grossouvre, 1894, a Cretaceous ammonite genus
439
Niko, Shuji: A new Devonian cephalopod from the Nakazato Formation of thesouthern Kitakami Mountains
291
Niko, Shuji: Early Carboniferous (Visean) cephalopods from the Hikoroichi
Formation, southern Kitakami Mountains
54
Niko, Shuji; Hamada, Takashi and Yasui, Toshio: Silurian Orthocerataceae(Mollusca: Cephalopoda) from the Yokokurayama Formation, Kurosegawa
Terrane59
Noda, Masayuki and Toshimitsu, Seiichi: Notes on a Cretaceous bivalve Inoceramus (Platyceramus) mantelli de Mercey from Japan
485
Okamoto, Takashi: Comparative morphology of Nipponites and Eubostrychoceras(Cretaceous notoceratids)
117
Sasaki, Osamu: Parameters for description of the shell form of the genus Anadara(Mollusca; Bivalvia)
513
Shigeta, Yasunari: Systematics of the ammonite genus Tetragonaites from theUpper Cretaceous of Hokkaido
319
Shuto, Tsugio: Gemmuloborsonia, a new genus of the family Turridae (Gastropoda)
48
from the Plio-Pleistocene Cabatuan Formation, Northwest Luzon
Taguchi, Eiji: A new species of Vepricardium (Bivalvia; Mollusca) from the609
Miocene Katsuta Group in Okayama Prefecture, Southwest Japan
Takagi, Toshio: Taxonomic and paleozoogeographic significance of Cenozoic
hunch-back like venerids, Part 1. Gigantocallista, geno novo (Mollusca:
Bivalvia), a new endemic venerid genus from the Pliocene of Sendai Bay,
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676

Miyagi Prefecture, northeastern Japan .................................. 541
Tanabe, Kazushige: Early life history of two Middle Pleistocene species of Limopsis(Arcoida: Bivalvia) ................................................. 631
Yang, Seong-Young: On the genus Plicatounio (Cretaceous non-marine Bivalvia)
from Korea ........................................................

77

Arthropoda

Irizuki, Toshiaki: Fossil ostracode assemblages from the Pliocene Sasaoka Formation, Akita City, Japan - with reference to sedimentological aspects - ... 296
Kaneko, Atsushi: A new trilobite genus Rhinophacops . . . . . . . . . . . . . . . . . . . . . . .. 360

Brachiopoda

Kazuyoshi, Endo: Growth and life mode of a Pleistocene brachiopod, Kikaithyris
hanzawai (Yabe) ................................................... 286

Echinoderma taOji, Tatsuo: Miocene Isocrinidae (stalked crinoids) from Japan and their biogeographic implication .................................................... 412
Oji, Tatsuo: Dimorphism and geographic distribution of two phenotypes of a west
Atlantic stalked crinoid Endoxocrinus parrae (Gervais). . . . . . . . . . . . . . . . .. 603

Conodonta

Igo, Hisaharu: Mixed conodont elements from Hachiman Town, Mino Terrane,
central Japan ....................................................... 270

Reptilia

Nakaya, Hideo: Upper Cretaceous elasmosaurid (Reptilia, Plesiosauria) from
Hobetsu, Hokkaido, northern Japan ..................................

96

Mammalia

Kawamura, Yoshinari and Iida, Kazuaki: An early Middle Pleistocene muridrodent molar from the Kobiwako Group, Japan ........................ 159

677

Palaeobotany
Kimura, Tatsuaki and Kim, Bong-Kyum: New taxa in the Late Triassic Daedong
Flora, South Korea, Part 2 ........................................... 141
Koizumi, Itaru and Yanagisawa, Yukio: Evolutionary change in diatom morphol347
ogy - An example from Nitzschia fossilis to Pseudoeunotia doliolus Kojima, Natsuhiko: Dinoflagellate cyst analysis of Holocene sediments from Lake
Hamana in central Japan ............................................ 197
Tanimura, Yoshihiro: Denticulopsis praehyalina, sp. nov.: An early Middle
Miocene pennate diatom from Dogo, Oki Islands, southwest Japan ....... 169

678

INDEX OF GENEEA AND SDECIES
Notes: Words listed are names of genus and species-groups which are described,
discussed or illustrated in the articles in Transactions Proceedings of PalaeontologicalSociety of Japan, New Series, No. 153 to No. 160. Words in bold-type are names of newly
proposed taxa.

Adnatoceras onimarense ................ 557, fig. 2
Ammonoia cf. beccarii ................. .469, fig. 10
Anthroplyopsis decurrens . ............... 142, fig. 12
Apodemus argenteus .................... 163, fig. 5
Assilina ...................................... 74
Assilina papillata ........................ 75, fig. 5
AsterocyC/ina stella .................. 259, figs. 3, 4

Eucyrtidiellum .............................. 593
Eucyrtidiellum disparile ................ 594, fig. 3
Eucyrtidiellum semifactum .............. 595, fig. 3
Eucyrtidiellum ptyctum .................. 595, fig. 3
Eucyrtidiellum pustulatum ............... 597, fig. 3
Eucyrtidiellum unumaense ............... 597, fig. 4
Eucyrtidiellum sp. f ..................... 597, fig. 4Eupachydiscus .............................. 623
Eupachydiscus keramasatoshii ........ 624, figs. 3, 4

B

F

Birostrina nipponica .............. 179, figs. 1-28, 32
Birostrina aff. nipponica ............ 192, figs. 29-31
Bolivina sp. A ......................... .469, fig. 10
Buccella frigida .................... 469, figs. 10, 11
Buccella cf. kuromatsunaiensis ......... .470, fig. 10
Buliminella elegantissima ............... .470, fig. 9

Foordiceras cf. F. wynnei ................ 213, fig. 2
Forresteria .................................. 378
Forresteria (Forresteria) alluaudi ........ 379, fig. 10

AC

Calyptogena (s.s.) pacifica . ........... 29, figs. 3, 4, 7
Corbula (s.l.) imamurae .................. 43, fig. 4
Corbula (Bicorbula) pyriforma ............ 37, fig. 4
Corbula (Bicorbula) ushibukensis .......... 39, fig. 4
Corbula (Eoursiviras) matsumotoi ......... .42, fig. 3
Cribrostomoides sp. . ........................ .470
Cycadocarpidium sp. cf. C. asaense ...... 149, fig. 15
Cycadocarpidium sp. cf. C. nagatoense .. 150, fig. 16
Cycadocarpidium sp. A ................ 151, fig. 17
DDenticulopsis praehyalina ............ 172, figs. 3, 4
Dinoflagellate cyst? type A .............. 209, fig. 6
Dinoflagellate cyst? type D .............. 209, fig. 6
Dinoflagellate cyst? type E .............. 210, fig. 6
Discocyclina sella . ....................... 264, fig. 5
Dolorthoceras (?) sp. . ................... 558, fig. 2
Domatoceras ogatsuense ................. 214, fig. 2
Drepanosamites sp. A .................. 145, fig. 11
E
Elasmosauridae gen. et sp. indet ....... 98, figs. 2, 10
Elphidium izumoense ............. .472, figs. 9, 11
Elphidium matsuense .............. 473, figs. 9, 11
Elphidium petforatum .............. 474, figs. 9, 11G

Geisonocerella nakazatoensis ............ 291, fig. 1
Geisonoceratid, gen. et sp. indet ........... 66, fig. 2
Gemmuloborsonia ............................. 48
Gemmuloborsonia coronifera .............. 52, fig. 3
Gemmuloborsonia jierstinei ............ 49, figs. 1, 2
Gigantocallista .............................. 542
Gigantocallista sendaica .............. 545, figs. 6, 7
Globigerinelloides barri .................... 5, fig. 3
H

Hedbergella delrioensis .................... 6, fig. 3
Hedbergella planispira .................... 6, fig. 3
Hedbergella trocoidea .................... 7, fig. 1

Inoceramus pictus ............................ 13
Inoceramus pictus minus ............ 16, figs. 1-10
Inoceramus (Platyceramus) mantelli . .487, figs. 2-11
Isocrinus sp ............................. 425, fig. 6
Isselicrinus .................................. 426
lsselicrinus sp. . ........................ .427, fig. 6
K

Kopaninoceras ................................ 61
Kopaninoceras kobayashii ................ 61, fig. 2
M

Mandarina .................................. 227

679

Mandarina aureola . ............. 239, figs. 5, 11, 15
Mandarina chichijimana ........ 231, figs. 5, 6, 8, 15
Mandarina exoptata .............. 242, figs. 11,15
Mandarina hahajimana ............ 241, figs. 11, 15
Mandarina hayamii .............. 243, figs. 11, 15
Mandarina hirasei .............. 234, figs. 5, 6, 8, 15
Mandarina io ...................... 235, figs. 8, 15
Mandarina luhuana ................ 235, figs. 9, 15
Mandarina mandarina .......... 229, figs. 5, 6, 8, 15
Mandarina nola ................... . 231, figs. 8, 15
Mandarina polita .............. 240, figs. 5, 11, 15
Mandarina suenoae .............. 242, figs. 5, 11, 15
Mandarina titan ................... . 237, figs. 9,15
Mandarina sp. . ....................... 244, fig. 11
Menabonites ................................ 620
Mesopuzosia yubarensis .................. 367, fig. 1
Mooreoceras kinnoi .................... 556, fig. 1
Murrayinella yakumoensis ............. 472, fig. 10
N

Neocycloceras (?) sp. . ................... 556, fig. 1
Neogondolella bisecta .................. 280, fig. 7
Neogondolella changxingensis ............ 280, fig. 5
Neogondolella intermedia ................ 281, fig. 5
Neogondolella polygrathiformis depressa .. 280, fig. 7
Neogondolella polygrathiformis magna .. 281, fig. 6
Neogondolella sp. A .................... 283, fig. 5
Neogondolella sp. B .................... 283, fig. 5
Neogondolella sp. C .................... 283, fig. 5
Neogondolella sp. D .................... 283, fig. 5
Neolacazopsis ................................ 664
Neolaca'1.opsis oso'1.awai .............. 668, figs. 2-7
Nephrolepidina praejaponica ............ 265, fig. 6
Nipponicorbula mashikensis. . ............. 45, fig. 3
Nipponicorbula mifunensis ................ 44, fig. 3
Nitzschia fossilis .................... 357, figs. 7,9
Nummulites beaumonti ................... 70, fig. 5oOrbitoclypeus kimurai ............... 260, figs. 3, 5
Orbitoclypeus sp. . ....................... 264, fig. 5pPlatyceramus ............................... .487
Plectina sp. . .......................... .471, fig. 9
Plicatounio .................................. 81
Plicatounio .................................. 82
Plicatounio (Plicatounio) naktongensis .. 82, figs. 3, 4

Plicatounio (Plicatounio) okjuni .......... 87, fig. 5
Plicatounio (Plicatounio) yooni .......... 88, fig. 6
Plicatounio (P.) sp. cr. P. (P.) yooni ...... 93, fig. 7
Podozamites ex gr. schenki .............. 146, fig. 13
Podozamites sp. A .................... 148, fig. 14
Protokionoceras .............................. 63
Protokionoceras fessicancellatum ........ 64, figs. 2, 3
Protoperidinium ........................ 209, fig. 6
Pseudoeunotia doliolus ................ 357, figs. 7, 8
Pseudojacobites .............................. 620
Pseudononion japonicum ................ 470, fig. 9
Pterophyllum cheondaeriense .......... 141, fig. 10
Q

Quingueloculina cr. fukushimaensis ...... 471, fig. 10

RRhinophacops ................................ 360
Rhinophacops schizoloma ................ 361, fig. 2
Rosalina bradyi ...................... 471, fig. 10
SSelenopemphix hamadaensis............ 208, fig. 5

T

Taeniopteris cheondaeriensis ............ 151, fig. 18
Taeniopteris mungyeongensis ............ 153, fig. 19
Tania ...................................... 535
Tania inokoshiensis .................... 536, fig. 1
Teliocrinus .................................. 421
Teliocrinus springeri .................. 423, figs. 4, 6
Tetragonites glabrus .................... 334, fig. 11
Tetragonites minimus .............. 336, figs. 11, 13
Tetragonites terminus .............. 338, figs. 11, 13
Ticinella primula .......................... 7, fig. 3
Tongoboryceras .............................. 618
Tragodesmoceroides .......................... 394
Tragodesmoceroides matsumotoi ., ....... 394, fig. 11
Trichohyalus sp. . ..................... 471, fig. 10
UUvigerina cf. akitaensis ................. .471, fig. 9
V

Vepricardium (Vepricardium) okamotoi................................ 609, figs. 6, 7

Transactions and Proceedingsof thePalaeontological Society of Japan
New SeriesNos. \53 - \60\989- \990

Palaeontological Society of Japan

The heading in Japanese commemorates the handwriting of Prof. Matajiro YOKOYAMA,
father of Japanese palaeontology, who was a professor of stratigraphy and palaeontology at
the Geological Institute, Imperial University of Tokyo.
The fossil on the cover is Phillipsia ohmorensis Okubo, an Early Carboniferous trilobite
from the Hikoroichi Formation in the Higuchizawa valley, Ofuna to City, Iwate Prefecture,northeast Japan (Collected by A. Haga, PAt 5766, X 3.0; after Kobayashi and Hamada,
1980, pI. 6, fig. 4).

CONTENTS

Number 153 (published April 30, 1989)
Transactions
Article870.

Page

Figures

1-11

1-4

Hiroshi Nishi, Satoshi Yokota and Tsunemasa Saito: An Early
Cretaceous (early Middle Albian) planktonic foraminiferal
fauna from the Hinagu Formation of Northern Kyushu, Japan........................................................
871.

Tatsuro Matsumoto: Some inoceramids (Bivalvia) from the
Cenomanian (Cretaceous) of Japan - V. A world-wide
species Inoceramus pictus Sowerby from Japan ............ 12-24
872. Saburo Kanno, Kazutaka Amano and Hiromitsu Ban:
Calyptogena (Calyptogena) pacifica Dall (Bivalvia) from the
Neogene System in the Joetsu district, Niigata Prefecture .... 25-35
873. Takeshi Kozai: A study of Corbula and Nipponicorbula(Bivalvia) from the Cretaceous of Japan ................... 36-47
874. Tsugio Shuto: Gemmuloborsonia, a new genus of the family
Turridae (Gastropoda) from the Plio-Pleistocene Cabatuan
Formation, Northwest Luzon ............................ 48-54
Proceedings ...................................... 55-58

1-10

1-7
1-4

1-3

Number 154 (published June 30, 1989)
Transactions
875.

Shuji Niko, Takashi Hamada and Toshio Yasui: Silurian
Orthocerataceae (Mollusca: Cephalopoda) from the Y okokurayam a Formation, Kurosegawa Terrane .................... 59-67
876. Kuniteru Matsumaru and Harutaka Sakai: Nummulites andAssilina from Tansen area, Palpa district, the Nepal Lesser
Himalayas.............................................. 68-76
877. Seong-Young Yang: On the genus Plicatounio (Cretaceous
non-marine Bivalvia) from Korea ........................ 77-95
878. Hideo Nakaya: Upper Cretaceous elasmosaurid (Reptilia,
Plesiosauria) from Hobetsu, Hokkaido, northern Japan. . . ... 96-116
879. Takashi Okamoto: Comparative morphology of Nipponites
and Eubostrychoceras (Cretaceous notoceratids) ............ 117-139

1-3

1-2
1-7
1-14
1-15

11

Number 155 (published September 30, 1989)
Transactions
880.
881.

882.

883.

884.
885.

886.

Tatsuaki Kimura and Bong-Kyum Kim: New taxa in the Late
Triassic Daedong Flora, South Korea, Part 2 .............. 141-158 10-19
Yoshinari Kawamura and Kazuaki !ida: An early Middle
Pleistocene murid rodent molar from the Kobiwako Group,Japan .................................................. 159-168
1-6
Yoshihiro Tanimura: Denticu/opsis praehyalina, sp. nov.: Anearly Middle Miocene pennate diatom from Dogo, Oki Islands,
1-4
southwest Japan ........................................ 169-177
Tatsuro Matsumoto and Akito Asai: Cenomanian (Cretaceous) inoceramids (Bivalvia) from Hokkaido and Sakhalin I.
Birostrina nipponica (Nagao et Matsumoto) ................ 178-196
1-32
Natsuhiko Kojima: Dinoflagellate cyst analysis of Holocene
197-2111-7
sediments from Lake Hamana in central Japan
Masayuki Ehiro and Fuminori Takizawa: Foordiceras andDomatoceras (nautiloid cephalopods) from the Upper Permian
Toyoma Formation, southern Kitakami Massif, northeast Japan........................................................ 212-217
1-2
Satoshi Chiba: Taxonomy and morphologic diversity of Mandarina (Pulmonata) in the Bonin Islands .................. 218-251
1-18
Proceedings ...................................... 252-254

Number 156 (published December 30, 1989)
Transactions
887.

Kuniteru Matsumaru and Koshi Kimura: Larger foraminiferafrom the Eocene Shimizu and Miocene Misaki Formations in
Tosa Shimizu City, Kochi Prefecture, Japan ................ 255-269
888. Hisaharu Igo: Mixed conodont elements from Hachiman
Town, Mino Terrane, central Japan ....................... 270-285
889. Kazuyoshi Endo: Growth and life mode of a Pleistocene
brachiopod, Kikaithyris hanzawai (Yabe) ................. 286-290
890. Shuji Niko: A new Devonian cephalopod from the Nakazato
Formation of the southern Kitakami Mountains ............ 291-295
891. Toshiaki Irizuki: Fossil ostracode assemblages from the
Pliocene Sasaoka Formation, Akita City, Japan - with reference to sedimentological aspects- ........................ 296-318
892. Yasunari Shigeta: Systematics of the ammonite genus

1-6
1-7
1-4

1-15

iii

Tetragonaites from the Upper Cretaceous of Hokkaido ...... 319-342
Proceedings ...................................... 343-345

1-13

Number 157 (published April 30, 1990)
Transactions
893.

894.
895.

896.
897.

23.

Itaru Koizumi and Yukio Yanagisawa: Evolutionary change
in diatom morphology - An example from Nitzschia fossilis to
Pseudoeunotia doliolus - ................................ 347-359
Atsushi Kaneko: A new trilobite genus Rhinophacops ...... 360-365
Tatsuro Matsumoto, Mamoru Nemoto and Chisato Suzuki:
Gigantic ammonites from the Cretaceous Futaba Group of
Fuk ushima Prefecture ................................... 366-381
Hiromichi Hirano, Takashi Okamoto and Khoji Hattori:
Evol ution of some Late Cretaceous desmoceratine ammonoids 382-411
Tatsuo Oji: Miocene Isocrinidae (stalked crinoids) from Japanand thir biogeographic implication ........................ 412-429
Short notes
Hiromi Matsuoka: New method to evaluate dissolution of
CaCOa in the deep-sea sediments . . . . . . . . . . . . . . . . . . . . . . .. 430-434
Proceedings .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 435-438

1-9
1-2

1-10
1-17
1-6

1-3

Number 158 (published June 30, 1990)
Transactions
898.

Tatsuro Matsumoto, Seiichi Toshimitsu and Yoshitaro Kawashita: On Hauericeras de Grossouvre, 1894, a Cretaceousammonite genus ........................................ 439-458
899. Ritsuo Nomura: Late Middle Miocene foraminifera from the
Matsue Formation, Shimane Prefecture .................... 459-484
900. Masayuki Noda and Seiichi Toshimitsu: Notes on a
Cretaceous bivalve Inoceramus (Platyceramus) mantelli deMercey from Japan ...................................... 485-512
901. Osamu Sasaki: Parameters for description of the shell form of
the genus Anadara (Mollusca; Bivalvia) .................. 513-534
902. Kuniteru Matsumaru: A new genus of the miogypsinid foraminifer from southwest Japan .......................... 535-539

1-8
1-11

1-16
1-16

iv

Number 159 (published September 30, 1990)
Transactions
903.

Toshio Takagi: Taxonomic and paleozoogeographic significance of Cenozoic hunch-back like venerids Part 1. Gigantocallista gen. nov. (Mollusca: Bivalvia), a new endemic venerid
genus from the Pliocene of Sendai Bay, Miyagi Prefecture,northeastern Japan ...................................... 541-553
904. Shuji Niko: Early Carboniferous (Visean) cephalopods fromthe Hikoroichi Formation, southern Kitakami Mountains .... 554-561
905. Rie Hori: Lower Jurassic radiolarian zones of southwest Japan
562-586906.

24.

Hiromi Nagai and Shinjiro Mizutani: Jurassic Eucyrtidiellum(Radiolaria) ............................................ 587-602
Short notes
Tatsuo Oji: Dimorphism and geographic distribution of two
phenotypes of a west Atlantic stalked crinoid Endoxocrinus
parrae (Gervais) ........................................ 603-606
Proceedings ...................................... 607-608

1-7
1-3
1-9
1-4

1-3

Number 160 (published December 30, 1990)
T ransacti 0 ns
907.

908.

909.
910.
911.

Eiji Taguchi: A new species of Vepricardium (Bivalvia; Mollusca) from the Miocene Katsuta Group in Okayama Prefecture,
Southwest Japan ........................................ 609-617
Tatsuro Matsumoto: An interesting pachydiscid ammonite
from Hokkaido, with remarks on relevant taxa (Studies ofCretaceous ammonites from Hokkaido-LXVII) ............ 618-630
Kazushige Tanabe: Early life history of two Middle Pleistocene species of Limopsis (Arcoida: Bivalvia) ............ 631-640
Seiichiro Matsui: Pliocene-Pleistocene molluscan associations
in north-central Japan and their relationship to environments 641-662
Kuniteru Matsumaru: A new genus of the trematophorate
miliolids (Fabulariidae) from the Eocene Setogawa Group,
Southwest Japan ........................................ 663-673
Systematic Index .................................. 674-677
Index of Genera and Species. . . . . . . . . . . . . . . . . . . . . . .. 678-679

1-7

1-5
1-4
1-5

1-7

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Transactions and Proceedings of the PalaeontologicalSociety of Japan

December 30, 1990

New Series No. 160

CONTENTS
TRANSACTIONS
907. Eiji Taguchi: A new species of Vepricardium (Bivalvia; Mollusca) from the908.

Miocene Katsuta Group in Okayama Prefecture, Southwest Japan. . ....... 609
Tatsuro Matsumoto: An interesting pachydiscid ammonite from Hokkaido,
with remarks on relevant taxa (Studies of Cretaceous ammonites from Hokkaido-LXVII) ....................................................... 618

909.

Kazushige Tanabe: Early life history of two Middle Pleistocene species ofLimopsis (Arcoida: Bivalvia). . ........................................ 631
910.
911.

Seiichiro Matsui: Pliocene-Pleistocene molluscan associations in northcentral Japan and their relationship to environments. . ................... 641
Kuniteru Matsumaru: A new genus of the trematophorate miliolids (Fabulari-idae) from the Eocene Setogawa Group, Southwest Japan ................. 663
SYSTEMA TIC INDEX .................................................... 674
INDEX OF GENERA AND SPECIES ...................................... 678