ISSN 0031 - 0204

Transactions and Proceedingsof thePalaeontological Society of Japan
New SeriesNo. 147

Palaeontological Society of Japan

October 30.1987

Hisayoshi IGO and Tsunemasa SAITO

Co-Editors

Officers for 1987-1988
President: Tatsuaki KIMURA
Honorary President: Teiichi KOBA YASH I
Councillors:

Kiyotaka CHINZEI, Takashi HAMADA, Yoshikazu HASEGAWA, Itam HAYAMI,

Hisayoshi lGO, Junji lTOIGAWA, Tadao KAMEl, Tatsuaki KIMURA, Tamio KOTAKA,Kei MORI, Ikuwo OBATA, Tsunemasa SAITO, Yokichi TAKAYANAGI, Kazushige
TANABE, Toshimasa TANAIMembers of Standing Committee: Kiyotaka CHINZEI (Membership), Takashi HAMADA (Foreign Affairs), ltaru HAYAMI (Finance), Hisayoshi lGO (Co-Editor of Transactions),
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The fossil on the cover is Vicarya yokoyamai Takeyama, an Early Middle
Miocene gastropod from the Kurosedani Formation at Kakehata, Yatsuo-cho,
Nei-gun, Toyama Prefecture, central Japan (Collected by T. Kotaka and K.
Ogasawara, lGPS No. 99075, photo by S. Ohtomo and Y. Kikuchi, xO.9).

All communication relating to this journal should be addressed to the

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

Trans. Proc. Palaeont. Soc. Japan, N. S., No. 147, pp. 91-108,7 Figs., October 30,1987

832. CRETACEOUS EOMIODON AND COSTOCYRENA (BIVALVIA)
FROM SOUTHWEST JAPANMASA YUKI TASHIRO
Department of Geology, Faculty of Science, Kochi University, Kochi 780

Abstract. In this paper 4 species of Eomiodon and 8 species and 2 subspecies of Costocyrena (including Costa cyrena oh n ish ii, sp. nov., Costocyrena hojiensis, sp. nov. and Costocyrena otsukai obsoleta, subsp. nov.) belonging to the Family Neomiodontidae are describedfrom the Cretaceous at various localities in southwest Japan.
Geographic distribution of Eomiodon and Costocyrena species seems to change throughthe Cretaceous time in southwest Japan. In the Lower Cretaceous, Eomiodon species restrictedly occur from the southern side of Kurosegawa Tectonic Belt, while all Costocyrella species are
known from the northern side of that belt, Northern Chichibu Belt. In the Upper Cretaceous,
the geographic distribution of the two genera becomes overlap, and they occur together even at
the same localities especially in central Kyushu. This may not mean habitat change of these
bivalves, but seems to support the hypothesis of the Early Cretaceous movement of a large
lateral fault in the Chichibu Belt.

da of Kochi Pref. for their supply of material.
The studied specimens (KSG) are kept in the
Faculty of Science, Kochi University.

Introduction

Many species of Eomiodon and Costocyrena
belonging to the Family Neomiodontidae widely
thrived during the Cretaceous times in Japan.
They occur abundantly from the various stratigraphic horizones characterized by the so-called
brackish water facies, ranging from Hauterivian
to Cenomanian, at many localities in Southwest
Japan.
Eomiodon and Costocyrena species describedin this paper seem to be important for the correlation of the Cretaceous strata in Japan. Changing of the geographic distribution of Eomiodol1
and Co:.,tocyrena species through the Cretaceous
times also involve interesting problems both onpalaeoecology and tectonic developments ofeastern Asia.
I wish to express my sincere thanks to Miss
Takako Ohnishi of Kagawa Pref., Mr. Hideyuki
Yanagisawa of Fukui Pref. and Mr. Seiji Matsu-

Systematic descritpion
Family Neomiodontidae Casey, 1955
Subfamily Eomiodontinae Hayami, 1965
Genus Eomiodoll Cox, 1935

Eomiodon sakawanus (Kobayashi et Suzuki)
Figures 1-7-12

1939. Astarte sakawana Kobayashi et Suzuki, Japan.
Jour. Ceol. Ceogr., vol. 13, nos. 3-4, p. 219, pI.
13, fig. 11 (non pI. l3, figs. 12 and 13).
1973. Eomiodon sakawanus (Kobayashi et Suzuki);Ohta, Bull. Fukuoka Univ. Educ., vol. 22, no. 3,
p. 250, pI. 1, figs. 1-11.
1975. Eomiodon sakawanus (Kobayashi et Suzuki);Hayami, Univ. Mus., Ulliv. Tokyo, Bull., 10, p.
138.
1976. Eomiodon sakawanus (Kobayashi et Suzuki);Ohta, Atlas of Japanese fossils, vol. 44, Mesozoic bivalves (3), figs. 7-9.

*Received September 16, 1986; revised manuscript
accepted July 6, 1987; read June 15, 1985 at Osaka
City University.

91Masayuki TASHIRO

92

Materials:-KSG 3803 and KSG3804,externalmoulds of right valves, from Uchiyama of Aioi,
Tokushima Prefecture. KSG 3805 and KSG
3806, external moulds of right and left valves,from Yonenomoto of Ittku, Kochi City.
Measurements:-(in mm.)
Specimens

LengthHeightThickness

KSG 3803, r. ext. mol.
KSG 3804, r. ext. mol.

13.0
10.0

KSG 3805, r. ext. mol.

14.1
18.0

11.0
9.0
11.5
15.0

2.5
1.5
2.5
2.0

KSG 3806, I. ext. mol.

Remarks:- The holotype was occurred fromthe Kaisekiyama Formation of Kamo, Sakawa in
Kochi Prefecture. Two species, treated in thisstudy (Figures 5-1, II and 12), preserved in theFossil Museum of Sakawa (not registered), werealso collected from the type locality.
This species is characterized by more broadly
spaced concentric ribs on the disk and less inflated valve than other Japanese Eomiodon
species. About 5 concentric ribs are countableon the adult stage. They are narrower than theirinterspaces and roof-shaped on the top.
Occurrence and geological age: - Fine-grainedsandstone of the Nakaizu Formation at Uchiyama of Aioi, Naka-gun in Tokushima Prefecture; Aptian. Very fine-grained sandstone of the
Funadani Formation at Ittku of Kochi City,
Kochi Prefecture; Aptian. Sandy mudstone of
the Kaisekiyama Formation at Kaisekiyama of
Sakawa, Kochi Prefecture. This species is also
known from the upper part of the Yamabu
Formation at Yamabu, Minami-Amabe-gun in
Oita Prefecture; Aptian(?).
Eomiodon matsumotoi Ohta
Figures 1-1-6

1973. Eomiodon matsumotoi Ohta, Bull. Fukuoka
Univ. Educ., vol. 22, no. 3, p. 245, pI. 2, figs. lB.
1975. Eomiodon matsumotoi Ohta; Hayami, Univ.
Mus., Univ. Tokyo, Bull., 10, p. 139.
1976. Eomiodon l1latsul1lotoi Ohta; Ohta, Atlas ofJapanese fossils, vol. 44, Mesozoic bivalves (3),figs. 10-15.
1979. Eomiodon matsul1lotoi Ohta; Katto and Tashiro,
Res. Rep., Kochi Univ., vol. 27, Nat. Sci., pI. 2,

figs. 1-7.
1981. Eomiodon matsumotoi Ohta; Ohta, Bull. Fukuoka Univ. Educ., vol. 31, no. 3, p.103, pI. 7, figs.
1-8.

Materials:-KSG 3807-KSG 3810, externalmoulds of left valves; KSG 3811, external mouldof right valve; all from Ohta of Tanoura, Ashikita-gun in Kumamoto Prefecture. KSG 3812 KSG 3813, external moulds of left valves, from
Uchiyama of Aioi, Naka-gun in Tokushima
Prefecture.
Measurements:-(in mm.)
Specimens

LengthHeightThickness

KSG 3807,1. ext. mol.

23.0

4.0

KSG 3809, I. ext. mol.

29.5
10.5

KSG 3811, r. ext. mol.

22.0

88.0
16.0

3.0

2.0

Remarks: - This species is characterized by thevery fine concentric striae which are developedon the interspaces of the concentric ribs on the
disk. Although this species resembles Eomiodon
sakawanus (Kobayashi et Suzuki) in its roundly
subtrigonal outline of the valve and distinct concentric ribs on the disk, it difers from E. sakawanus in its more inflated valve, numerous andmore or less irregularly spaced concentric ribs,
and fine concentric striae on their in terspaces.
Occurrence and geological age: -Gray siltstoneof the Kawaguchi Formation at Ohta of Tanoura,
Ashikita-gun, Kumamoto Prefecture; Hauterivian.
Fine-grained sandstone of the Shobu Formation
at Uchiyama of Aioi, Naka-gun in Tokushima
Prefecture; Hauterivian. This species had beenreported from the lower member of Doganaro
Formation of the Shimanto Belt in Kochi Prefecture (Katto and Tashiro, 1979) and from thelower part of Yamabu Formation of the Chichibu Belt in Ohita Prefecture (Tashiro, 1985a),both in the Hauterivian in age. This is also known
from the Uminoura Formation in central Kyushu(Ohta and Monji, 1976). The geological age of
the Uminoura Formation is probably the earliest
Cretaceous.
Eomiodon matsubasensis Tamura
Figures 1-13-25

832. Cretaceous Eomiodon and Costocyrena
1977. Eomiodon matsubasensis Tamura, Mem. Fac.
Educ. Kumamoto Univ., no. 26, Nat. Sci., p. 107,
pI. 6, figs. 9-19.
1982. Eomiodon matsubasensis Tamura; Tashiro andMatsuda, Trans. Proc. Palaeont. Soc. Japan, N.S.,
no. 127, p. 410, pI. 65, figs. 14-15.
1985. Eomiodon matsubasensis Tamura; Matsuda, Fossils, no. 39, pI. 2, figs. 9-10.

Materials:-KSG 3814-KSG 3815, externalmoulds of left and right valves, from Higashimachi (Shishijima island) in Kagoshima Prefecture. KSG 3816-KSG 3818, external moulds ofleft and right valves, from Karakizaki (Goshonoura island) in Kumamoto Prefecture. KSG 3819
- KSG 3810, external moulds of left and rightvalves, from Chikaraishi, Kami-mashiki-gun in
Kur-.amoto Prefecture, KSG 3821-KSG 3830,
external moulds of left and right valves, from
Furuyashiki (Goshonoura island) in Kumamoto
Prefecture.
Measurements:- (in mm.)
Specimens
KSG 3816, r. ext. mol.
KSG 3818, r. ext. mol.
KSG 3814, I. ext. mol.
KSG 3823,1. ext. mol.
KSG 3819, I. ext. mol.

Length11.0
4.0

Height
14.0
8.0
11.5
8.0
3.5

KSG 3825, 1. ext. mol.

6.5

6.5

15.0
9.0
13.0

Thickness
4.0
2.0
3.0
2.0
1.0
2.0

Remarks:-Numerous specimens are undoubtedly conspecific with Eomiodon matsubasensis
Tamura (1977) are collected from the Mifune
Group in central Kyushu.
Occurrence and geological age:-Dark gray togreenish gray mudstone of the lower member of
Mifune Group at Chikaraishi, Mashiki-machi of
Shimo-mashiki-gun in Kumamoto Prefecture;
Middle Cenomanian. Very fine-grained sandstoneof the S-I1 Formation of Goshonoura Group at
Tateishi, Higashimachi (Shishijima island) of
Izumi-gun in Kagoshima Prefecture; Lower Cenomanian. Greenish gray mudstone of the Upper(III) Formation of Goshonoura Group at Karakizaki, Goshonoura-machi (Goshonoura island)of Amakusa-gun in Kumamoto Prefecture; Lower
Cenomanian. This species is common in thelower member of the Mifune Group at Magano,
Subayashi and Katashida areas of Shimo-mashiki-

93

gun in Kumamoto Prefecture. This is also known
from the Fukigoshi Formation of the Sotoizumi
Group at Nagase of Odochi, Monobe-mura ofKami-gun in Kochi Prefecture (Lower Cenomanian) (Tashiro and Matsuda, 1982).

Eomiodon? kumamotoensis Tamura
1959. Eomiodon kumamotoensis Tamura, Trans. Proc.
Palaeont. Soc. Japan, N.S., no. 33, p. 115, pI. 12,
figs. 17-18.
1960. Eomiodon kumamotoensis Tamura; Tamura,Mem. Fac. Educ. Kumamoto Univ., vol. 8, Nat.
Sci., p. 240.
1975. Astarte? kumamotoensis (Tamura); Hayami,
Univ. Mus., Univ. Tokyo, Bull., 10, p. 128.
1986. Eomiodon kumamotoensis Tamura; Tashiro andKatto, Res. Rep., Kochi Univ., vol. 34, Nat. Sci.,
pI. I, figs. 15-17.

Material:-KSG 3931, conjoined valves, fromTainokawa of Obama, Susaki City in Kochi
Prefecture.
Remarks:-The typical specimen of thisspecies was described from the Upper Jurassic
Sakamoto Formation of the Torinosu Group at
Sakamoto in Kumamoto Prefecture, by Tamura(1959).
Occurrence and geological age:-Dark greenish
gray mudstone of the basal part of Doganaro
Formation of the Shimanto Belt at about 350 m
west of Tainokawa of Obama, Susaki City in
Kochi Prefecture; Uppermost Jurassic or lowest
Cretaceous.
Genus Costocyrena Hayami, 1965

Costocyrena radiatostriata (Yabe et Nagao)
Figures 2-13 - 22

1926. Cyrena radiatostriate Yabe et Nago, in Yabe,
Nagao and Shimizu, Sci Rep., Tohoku Imp.
Univ., Ser. 2, vol. 9, no. 2, p. 51, pI. 12, figs.
29-35.
1965. Costocyrena radiatostriata (Yabe et Nagao);
Hayami, Mem. Fac. Sci., Kyushu Univ., Ser. D,
Geol., vol. 17, no. 2, p. 73, pI. 19, figs. 1-7.
1975. Costocyrena radiatostriata (Yabc et Nagao);
Hayami, Univ. Mus., Univ. Tokyo, Bull., 10, p.
140.
1976. Costocyrena radiatostriata (Yabe et Nagao);

Masay uki TASHIRO

94

5
3

2

4

30

13

25

29

27
26

32

37
36

832. Cretaceous Eomiodon and Costocyrena
Ohta, Atlas of Japanese fossils, vol. 44, no. 3,
figs. 22-26.
1977. Costocyrena radiatostriata (Yabe et Nagao);
Matsukawa, Jour. Ceol. Soc. Japan, vol. 83, no.
2, pI. 1, fig. 8.
1979. Costocyrena radiatostriata (Yabe et Nagao);
Matsukawa, Ibid., vol. 85, no. 1, pI. 1, figs. 3,4
and 9.
1979. Costocyrena sp. B aff. C. radiatostriata (Yabe et
Nagao); Matsukawa, Ibid., vol. 85, no. 1, pI. 1,
figs. 1-2.
1980. Costocyrena radiatostriata (Yabe et Nagao);
Tashiro et al., in Taira and Tashiro eds. Ceology
and paleontology of the Shimanto Belt, pI. 10,
fig. 18.

95

species to Costocyrena. The present species
undoubtedly belongs to Costocyrena radiatostriata (Yabe et Nagao) by the diagnostic characters of which were well defined by Hayamai(1965).
Occurrence and geological age:-Dark-graymudstone of the lower member of Yunoki Formation of the Monobegawa Group at Todoronotaki of Hibihara (Monobe area), Kami-gun in
Kochi Prefecture; Upper Barremian.

Costocyrena matsumotoi Hayami
Figures 5-1-13

Materials:-KSG 3831-KSG 3835, rightvalves: KSG 3836-KSG 3840, left valves; allfrom Todoronotaki of Hibihara, Monobe-mura,Kami-gun in Kochi Prefecture.
Measurements:-(in mm.)
Specimens
KSG 3836, r. v.
KSG 3837, r. v.
KSG 3838, r. v.
KSG 3834, 1. v.
KSG 3839, r. v.

LengthHeightThickness

9.5
9.5
14.5
10.5
16.5

7.0
7.5
13.5
9.0
12.5

2.5
1.0
3.6
4.5
2.0

Remarks:-This species was described originally from the Sebayashi Formation of Sanchu incentral Japan. Hayami (1965) referred this~1965. Costocyrena matsumotoi Hayami, Mem. Fac.
Sci., Kyushu Univ., Ser. D, Ceol., vol. 17, no. 2,
p. 133, pI. 18, figs. 2-12.
1975. Costocyrena matsumotoi Hayami; Hayami, Univ.
Mus., Univ. Tokyo, Bull., 10, p. 140, pI. 7, figs.
10-11.
1976. Costocyrena matsumotoi Hayami; Ohta, Atlasof Japanese fossils, vol. 44, Mesozoic bivalves,
no. 3, Cr. 26.
1981. Costocyrena matsumotoi Hayami; Ohta, Bull.
Fukuoka Univ. Educ., vol. 31, no. 3, p. 103, pI.
8, figs. 8-12.

Materials:-KSG 3841-KSG 3843, externalmoulds of right valves; KSG 3844-KSG 3853,
external moulds of left valves; all from Jhoguzan

Figures 1-1-6. Eomiodon matsumotoi Ohta, xl
1, KSG 3807; 2, KSG 3811; 3, KSG 3808;4, KSG 3809; 5, KSG 3810; Loc. Ohta of Tanoura, Ashikita-gun,
Kumamoto Pref., 6, KSG 3812; Loc. Mamidani of Nakaizu, Kami-katsu-gun, Tokushima Pref.
7-12.
Eomiodon sakawanus (Kobayashi et Suzuki)
7, KSG 3803; 8, KSG 3804; x1.5, Loc. Uchiyama of Aioi, Naka-gun, Tokushima Pref., 9, KSG 3805; 10, KSG
3806; xl, Loc. about 200 m south of Yonenomoto, Kochi City, Kochi Pref., 11 and 12, x1.5, Loc. Kaisekiyama
of Kamo, Sakawa, Takaoka-gun, Kochi Pref.
13-25. Eomiodon matsubasensis Tamura, x2
13, KSG 3816; 14, KSG 3817; 15, KSG 3818; Loc. Karakizaki, Goshonoura-jima, Amakusa-gun, Kumamoto
Pref., 16, KSG 3814, Loe. Higashimachi, Shishijima, Izumi-gun, Kagoshima Pref., 17, KSG 3821; 18, KSG 3822;
19, KSG 3823; 21, KSG 3824; 22, KSG 3825; 23, KSG 3826; 24, KSG 3829; 25, KSG 3830; Loc. Furuyashiki
of Hongo, Goshonoura-jima, Amakusa-gun, Kumamoto Pref., 20, KSG 3819, Loc. Chikaraishi of Miyanomoto,Kamimashiki-gun, Kumamoto Pref.
26-30. Costocyrena otsukai otsukai (Yabe et Nagao), x2
26, KSG 3910, Loc. Tatsukawa of Katsuura, Kamikatsu-gun, Tokushima Pref., 27, KSG 3907, Loc. Yonenomoto of Ittku, Kochi City, Kochi Pref., 28, KSG 3912; 30, KSG 3905; Loc. Kaganoi of Kuma, Kochi City,
Kochi Pref., 29, KSG 3913, Loc. Kami-Koshigoe, Minami-Amabe-gun, Ohita Pref.
31-37. Costocyrena otsukai obsoleta, subsp. nov., x2
31, KSG 3896, holotype; 32, KSG 3899, paratype; 33, KSG 3900, paratype; 34, KSG 3901, paratype; 35, KSG
3897, paratype; 36, KSG 3902, paratype; 37, KSG 3898, paratype; Loc. Idaira of Inasa, Shizuoka Pref.
All the specimens are gum cast of the external moulds, except for 11 and 12.

Masayuki TASHIRO

96

of Miyaji (type locality of this species by Hayami, 1965), Yatsushiro City in Kumamoto Prefecture.
Measurements:-(in mm.)
Specimens
KSG 3841, r. ext. mol.
KSG 3842, r. ext. mol.
KSG 3843, r. ext. mol.
KSG 3845, I. ext. mol.
KSG 3850, I. ext. mol.
KSG 3852, I. ext. mol.

LengthHeight

20.0
11.0
10.0
14.5
21.0
15.0

16.5
8.5
9.0
11.5
18.0
11.0

Thickness
4.5
2.3
2.0
3.5
4.5
4.0

Remarks:-Many external and internal mouldsof this species are at hand. This specis resemblts
Costocyrena radiatostriata (Yabe et Nagao), in its
subtrigonal outline, but it differs clearly from thelatter by its less numerous and distinct concentric ribs on the disk, and less numerous andstronger radial striae on the disk.
Occurrence and geological age:-Dark graymudstone of the Yatsushiro Formation at
Jhoguzan of Miyaji, Yatsushiro City in Kumamoto Prefecture; upper part of the Lower Albian
by Matsumoto etal. (1981).
Costocyrena minor Ohta
Figures 2-29-33

1981. Costocyrena minor Ohta, Bull Fukuoka Univ.
Educ., vol. 31, no. 3, p. 103, pI. 8, figs. 19-36.

Materials:-KSG 3854-KSG 3856, externalmoulds of right valves; KSG 3857-KSG 3859,
external moulds of left valves; both from Doiban
of Yunoki (Monobe area), Kami-gun, Kochi
Prefecture. KSG 3860-KSG 3862, externalmoulds of left and right valves, from Imaizumi of
Yatsushiro City in Kumamoto Prefecture.
Measurements:-(in mm.)
Specimens
KSG 3857, 1. ext. mol.
KSG 3858, I. ext. mol.
KSG 3854, r. ext. mol.
KSG 3859, I. ext. mol.
KSG 3860, r. ext. mol.
KSG 3862, r. ext. mol.

Length

5.0
6.0
5.5
6.5
6.0
5.0+

Height
4.5
5.5
5.0

5.5
4.8
5.0

Thickness

1.0
1.0
1.0
1.4
1.0
1.2

Remarks:-The specimens from the Monobe
area in Kochi Prefecture, are somewhat larger
than the specimens from the Yatsushiro area inKumamoto Prefecture. Other features between
the specimens from the two areas, are entirely
identical in each others. This species is discriminated from Costocyrena radiatostriata (Yabe et
Nagao), in its very smaller valve, and more distinct concentric ribs on the disk.
Occurrence and geological age:-Dark greenish
gray mudstone of the basal part of Hibihara
Formation at Yunoki of Odochi, Kami-gun in
Kochi Prefecture (Monobe area); Aptian. Dark
gray mudstone of the Miyaji Formation at Imaizumi Yatsushiro City in Kumamoto Prefecture(Yatsushiro area); Aptian(?). This species is also

~ Figures 2-1-12. Costocyrena ohnishii, sp. nov., x2

1, KSG 3884, paratype; 2, KSG 3881, paratype; 3. KSG 3882, paratype; 4, KSG 3885, paratype; 5, KSG
3880, holotype; 6, KSG 3883, paratype; Loc. Tatsukawa of Katsuura, Kamikatsu-gun, Tokushima Pref., 7, KSG
3887, paratype; 8, KSG 3892, paratype; 9, KSG 3893, paratype; 10, KSG 3891, paratype; 11, KSG 3886, paratype; 12, KSG 3888, paratype; Loc. idaira of inasa, Shizuoka Pref.
13-22. Costocyrena radiatostriata (Yabe et Nagao), x2
13, KSG 3831; 14, KSG 3836; 15, KSG 3837; 16, KSG 3838; 17, KSG 3839; 18, KSG 3840; 19, KSG 3832;
20, KSG 3833; 21, KSG 3834; 22, KSG 3835; Loc. Todoronotaki of Yunoki, Odochi area, Kami-gun, Kochi
Pref.
23-28. Costocyrena mifunensis Tamura, x2
23, KSG 3864; 24, KSG 3865; 26, KSG 3866; 27, KSG 3867; 28, KSG 3863; Loc. Karakizaki of Goshonourajim a, Amakusa-gun, Kumamoto Pref., 25, KSG 3868; Loc. Higashimachi of Shishijima, Izumi-gun, KagoshimaPref.
29-33. Costocyrena minor Ohta, x2
29, KSG 3857; 30, KSG 3858; 31, KSG 3854; 32, KSG 3859; 33, KSG 3855; Loc. Doiban of Yunoki, Odochi
area, Kami-gun, Kochi Pref.
All the specimens are gum casts of the external moulds.

832. Cretaceous Eomiodon and Costocyrena

97

1

5
3

11

2
6

8

12

7

13

16

15

14
17

21

20

23
18

22
27
28
26
24

29

30

31

32

33

Masayuki TASHIRO

98

known from the basal part of the Hinagu Formation (Aptian) at Koda of Yatsushiro City in
Kumamoto Prefecture.

Costocyrena mifunensis Tamura
Figures 2-23-28

Costocyrena hojiensis, sp. nov.

1977. Costocyrena mifunensis Tamura, Mem. Fac.
Educ. Kumamoto Uiz iv. , no. 26, Nat. Sci., p.
107, pI. 12, figs. 12-20.
1985. Costocyrena mifunensis Tamura; Matsuda, Fossils, no. 39, pI. 2, fig. 8.

Materials:-KSG 3863-KSG 3867, externalmoulds of right and left valves, from Furuyashiki
of Hongo, Goshonoura island in Kumamoto
Prefecture. KSG 3868, right external mould,
from Higashi-machi, Shishijima island in Kagoshima Prefecture.
Measurements:-(in mm.)
Specimens

LengthHeightThickness

KSG 3863, r. ext. mol.

15.0
11.5
19.0
16.0
11.0
16.0

10.0
7.0
13.0
8.0
8.0
9.5

2.0
3.0
4.0
3.0
2.0
2.0

KSG 3864, r. ext. mol.
KSG 3865, I. ext. mol.
KSG 3866, r. ext. mol.
KSG 3867, I. ext. mol.
KSG 3868, r. ext. mol.

(Shishijima island), Izumi-gun in Kagoshima
Prefecture; Lower Cenomanian. The type specimen (KE2669) by Tamura (1977), was recorded
from the Lower Formation of Mifune Group(Middle Cenomanian), in central Kyushu.

Remarks:-Although the specimens from the
Goshonoura Group, treated in this paper, are defonned, they are undoubtedly identified with
Costocyrena mifunensis Tamura, from the
Mifune Group in central Kyushu, by its strongly
elevated concentric ribs on the disk and broadened area behind the posterior carina. This
species is easily discriminated from other speciesof Costocyrena, e.g., C. radiatostriata (Yabe et
Nagao), C. minor Ohta or C. otsukai (Yabe et
Nagao), in its very strong concentric ribs, lessnumerous but strong radial striae, and broadened
posterior slope (area) behind the posterior carina.
Occurrence and geological age:-Dark graymudstone of the upper formation (III) of Goshonoura Group at Furuyashiki of Hongo, Goshonoura-machi (Goshonoura island), Amakusa-gun inKumamoto Prefecture; Lower Cenomanian. Finegrained sandstone of the SolI (Katasoba) Formation of the Goshonoura Group at Higashi-machi

Figures 3, 5-28-37

Materials:-Holotype, KSG 3869, left externalmould; paratypes, KSG 3870-KSG 3871, rightexternal moulds; paratypes, KSG 3872-KSG
3875, left external moulds; KSG 3877-KSG
3879, internal moulds of left and right valves;
all from Tatsukawa of Katsuura-machi, Tokushima Prefecture.
Diagnosis:-Shell trigonally ovate; umbo
strongly prosogyrous, located at about one
fourth or less from front of valve; surface withnumerous concentric ribs; posterior carina weak.
Description:-Shell moderate in size, trigonally ovate or roundly subtrigonal in outline, weakly inflated, longer than high; umbo small, a little
prominent, strongly prosogyrate for the genus,
located at about one fourth or one fifth fromfront of valve; anterior dorsal margin short,
weakly concave; anterior margin nearly straight,
forming a blunt angle about 110° with broadly
arched ventral margin; posterior margin weakly
convex; posterior dorsal margin long, slightly
convex; posterior carina weak; escutcheon narrow but elongated; lunule very narrow, distinctly

Figure 3. Sketch of the holotype, Costocyrena

hojiensis, sp. nov.

832. Cretaceous Eomiodon and Costocyrena

99

depressed from the disk; surface ornamented
with crowded concentric ribs; ribs roof-shaped,
narrower than their interspaces, number about
20 on adult specimens; hinge of lucinoid, cardinal 2 and 3b large, oblique; cardinal 3a small,subvertical; inner margin smooth.
Measurements:-(in mm.)
Specimens
KSG 3872, I. ext. mol.
KSG 3873, I. ext. mol.
KSG 3869, I. ext. mol.
KSG 3874, I. ext. mol.
KSG 3870, r. ext. mol.
KSG 3875, I. ext. mol.
KSG 3871, r. ext. mol.

Length
12.0
15.0
13.0
13.0
16.0
16.5
17.5

Height
10.0
11.0
9.0
9.5
13.0
12.0
13.0

Thickness
2.0
2.0
3.0
2.0
3.5
3.5
5.0

Observation:-On some specimens of thisspecies very fine and numerous radial striae
appear subinternally on the interspaces of theconcentric ribs on the disk. The posterior carina
is very weak except for umbonal region.
Comparison: - The immature forms of thisspecies are closely similar to the mature forms of
Costocyrena minor Ohta, in having its sub trigonal outline of the valve and remarkable concentric ribs on the disk. This species is probably
related to Costocyrena minor.
Occurrence and geological age:-Fine-grainedsandstone of the basal part of the Hoji Formation of the Monobegawa Group at Tatsukawa of
Katsuura-machi, Kami-katsu-gun in Tokushima
Prefecture; Aptian.
Costocyrena ohnishii, sp. nov.
Figures 2-1-12, 4Materials:-Holotype, KSG 3880, externalmould of left valve; paratypes, KSG 3881-KSG
3883, external moulds of right valves; KSG 3884
-KSG 3885, external moulds of left valves; allfrom Tatsukawa of Katsuura, Tokushima Prefecture. Paratypes, KSG 3886-KSG 3888, external moulds of left valves; KSG 3889-KSG
3895, external moulds of right valves; both from
Idaira of Inasa, ShizuokaPrefecture.
Diagnosis:-Shell trigonally ovate; umbo
strongly prosogyrate, located at about one fourth

Figure 4. Sketch of the hoiotype, Costocyrena
ohnishii, sp. nov.

to two fifths from front of valve; surface ornamented by strongly prominent and crenulated
concentric ribs which are very widely spaced;
posterior carina distinctly angulated.
Description:-Shell moderate in size, trigonally ovate or elliptically sub trigonal in outline,
more or less inflated, slightly longer than high;umbo prominent, strongly prosogyrous for the
genus, located anteriorly at one fourth to two
fifths in shell length; anterior dorsal margin
weakly concave; anterior margin very short,nearly straight, forming nearly a right angle withbroadly arcuated ventral margin; posterior margin short, subvertical, very weakly convex; posterior dorsal margin very long, nearly straightor very weakly arched; posterior carina strongly
angulated, extended nearly straight from umbo
to postero-ventral corner; lunule distinctly separated from the disk, deeply depressed; escutcheon very narrow but elongated; surface ornamented with about 7 strong concentric ribs
which are narrower than their interspaces andvery finely crenulated; hinge with typical Lucinoid; inner margin smooth.
Measurements:-(in mm.)
Specimens
KSG 3884, I. ext. mol.
KSG 3881, r. ext. mol.
KSG 3882, r. ext. mol.
KSG 3885, I. ext. mol.

Length
13.5
15.0
16.0
15.0

Height
10.0
9.5
15.0
14.0

Thickness
2.0
2.0
4.0
4.0

Masayuki TASHIRO100
KSG 3880, I: ext. mol.
KSG 3889, r. ext. mol.
KSG 3890, r. ext. mol.
KSG 3891, r. ext. mol.
KSG 3886, I. ext. mol.
KSG 3892, r. ext. mol.

13.0
11.0
11.5
14.5
10.5
15.0

11.0
8.5
9.0
11.5
7.0
9.0

2.0
2.0
3.0
3.0
3.0
3.0

Observation:- The concentric ribs on the disk
are somewhat variable in strength but are rather
uniform in number. On some specimens, veryfine radial striae which are concerned with thecrenulations on the concentric ribs, appear on
the outsklits of the ribs (see Figure 2-10).
Comparison: - This species resembles Costocyrena otsukai (Yabe et Nagao in Yabe, Nagao
and Shimizu, 1926), from the Shiroi Formationof the Sanchu area in central Japan, in its lessdeveloped radial striae on the disk, but theformer differs from the latter in its strong andless numerous concentric ribs and more or lessprominent umbo.
Occurrence and geological age:-Dark graymudstone of the Tatsukawa Formation at Tatsukawa, Katsuura-gun in Tokushima Prefecture;
Upper Hauterivian. Dark gray shale of the Idaira
Formation at Inasa, Inasa-gun in Shizuoka Prefecture; Barremian(?) or Upper Hauterivian.
Costocyrena otsukai otsukai (Yabe et Nagao)
Figures 1-26-30

1926. Cyrena otsukai Yabe et Nagao, in Yabe, Nagao
and Shimizu, Sci. Rep. Tohoku Imp. Univ., Ser.
2, vol. 9, no. 2, p. 50, pI. 2, figs. 20-24.
1973. Costocyrella otsukai (Yabe et Nagao); Ohta,

Bull. Fukuoka Univ. Educ., vol. 22, no. 3, p. 256,
pI. 3, figs. 1-11.
1973. Costocyrena crellatus Ohta, Ibid., vol. 22, no. 3,
p. 258, pI. 3, fig. 12.
1975. Costocyrena otsukai (Yabe et Nagao); Hayami,
UniJ'. Mus., Univ. Tokyo, Bull., 10, p. 139.
1976. Costocyrena otsukai (Yabe et Nagao); Ohta,
Atlas of Japanese fossils, vol. 44, Mesozoic
bivalves, no. 3, Cr. 26, figs. 16 - 20.
1977. Costocrena otsukai (Yabe et Nagao); Matsukawa,
Jour. Ceol. Soc. Japan, vol. 83, no. 2, pI. 1, figs.
7,10 and 11.
1979. Costocyrena otsukai (Yabe et Nagao); Matsukawa,Ibid., vol. 85, no. 1, pI. 1, figs. 5-6.
1981. Costocyrena otsukai (Yabe et Nago); Ohta, Bull.
Fukuoka Univ. Educ., vol. 31, no. 3, p. 103, pI.
7, figs. 13-34.

Materials:-KSG 3903-KSG 3904, externalmoulds of left and right valves, from Yonenomoto of Ittku, Kochi City in Kochi Prefecture.
KSG 3905-KSG 3908, external moulds of left
and right valves, from Kaganoi of Higashi-kuma,
Kochi City. KSG 3909-KSG 3912, externalmoulds of right and left valves, from Tatsukawa
of Katsuura, Katsuura-gun in Tokushima Prefecture. KSG 3913-KSG 3916, external moulds
of right valves, from Kami-koshigoe, MinamiAmabe-gun in Ohita Prefecture.
Measurements:-(in mm.)
Specimens

LengthHeightThickness

KSG 3906, I. ext. mol.

16.0
17.0
14.0
16.0
18.0
15.5
18.0

12.5
11.5
9.5
11.5
11.0
9.0
13.5

2.5
3.5
2.5
2.0
2.0
2.5
3.0

KSG 3907, r. ext. mol.
KSG 3909, I. ext. mol.
KSG 3910, r. ext. mol.
KSG 3911, r. ext. mol.
KSG 3913, I. ext. mol.
KSG 3912, I. ext. mol.

~ Figures 5-1-13. Costocyrena matsumotoi Hayami, x2

1. KSG 3844; 2, KSG 3845; 3, KSG 3841; 4, KSG 3846; 5, KSG 3842; 6, KSG 3847; 7, KSG 3848; 8, KSG
3843; 9, KSG 3849; 10, KSG 3850; 11, KSG 3851; 12, KSG 3852; 13, KSG 3853; Loc. Jhogusan of Miyaji,
Yatsushiro City, Kumamoto Pref.
14-27. Costocyrena sp. cf C. peikangellsis Hayami, x2
14, KSG 3917; 15, KSG 3920; 18, KSG 3918; 20, KSG 3922; 21, KSG 3923; 22, KSG 3924; 26, KSG 3919; 27,
KSG 3921; Loc. Kasanokawa of Okho, Ryoseki area, Nangoku City, Kochi Pref., 16, KSG 3929; 25, KSG 3928;
17, KSG 3930; 19, KSG 3927; Loc. Todai of Hasc, Kami-ina-gun, Nagano Pref., 23, KSG 3926; Loc. Idaira oflnasa, lnasa-gun, Shizuoka Pref., 24, x3, showing surface ornamentation, Loc. Kasanokawa.
28-37. Costocyrella hojiensis, sp. nov., x2
28, KSG 3876; 29, KSG 3872, paratype; 30, KSG 3871, paratype; 31, KSG 3870, paratype; 32, KSG 3875,
paratype; 33, KSG 3873, paratype; 34, KSG 3869, holotype; 35, KSG 3877, paratype; 36, KSG 3879, paratype;37, KSG 3878, paratype; Loc. Kawanishi of Kami-katsu-gun, Tokushima Pref.
All the specimens are gum casts of the internal and external moulds.

101832. Cretaceous Eomiodon and Costocyrena

2

8

7

9

10
12
15

11

6

23
20

22

16

14
17

24

27
19
21

30
26

18

28

25

33
31

Masayuki TASHIRO

102

Remarks:-This subspecies is one of the wellknown Early Cretaceous bivalves, representativeof the so-called Ryoseki Fauna in southwest
Japan. The concentric ribs on the disk arevariable from 8 to 15 in number. Very fine radialstriae or crenulations are often observable on the
top or outsklits of the concentric ribs.
The crenulations on the concentric ribs aredescribed as the sub specific characters whichwere discriminated Cos to cyrena otsukai crenatus
Ohta from C. otsukai otsukai by Ohta (l973).
In so far as I can see the distinctions between
them are one of the varieties of C. otsukai otsukai.
Occurrence and geological age:-Fine-grained~'1ndstone or silty mudstone of the upper member of Ryoseki Formation of the Monobegawa
Group, at Yonenomoto of Ittku and Kaganoi of
Higashikuma, both in Kochi City; Hauterivian.
Dark greenish gray mudstone of the upper member of the Ryoseki Formation at about 1600 m
north of Suita, Kami-gun in Kochi Prefecture;
Hauterivian. Greenish gray sandy mudstone of
the Tatsukawa Formation of the Monobegawa
Group at Tatsukawa of Katsuura, Katsuura-gun
in Tokushima Prefecture; Hauterivian. Dark graymudstone of the upper member of Koshigoe
Formation (Haidate II Formation by Tashiro
et al., 1983) at Kami-koshigoe of Honjho,
Minami-Amabe-gun in Ohita Prefecture; Hauterivian. Dark gray mudstone of the Kawaguchi
Formation at Kami-tanoura of Tanoura-machi,
Ashikita-gun in Kumamoto Prefecture. The holotype was recorded from the Shiroi Formation of
the Sanchu area in central Japan. This species isalso known from the Yuasa Formation at Yuasa
in Wakayama Prefecture.
Costocyrena otsukai obsoleta, subsp. nov.
Figures 1-31-37,6

Materials:-Holotype, KSG 3896, externalmould of left valve; paratypes, KSG 3897 - KSG
3898, external moulds of left valves; KSG 3899
- KSG 3902, external moulds of right valves; allfrom Idaira of Inasa, Inasa-gun in Shizuoka Prefecture.

Figure 6. Sketch of the hoiotype, Costocyrena
otsukai obsoleta, subsp. nov.

Diagnosis:-Shell trigonal ovate; umbo prosogyrate, weakly prominent; surface nearly smooth
except for several weak concentric ribs nearumbo; posterior carina distinctly angulated.
Description:-Shell medium in size, trigonallyovate, longer than high, moderately inflated;umbo small, weakly prosogyrate, a little prominent, pointed at two fifths from front of valve;anterior dorsal margin nearly straight; anterior
margin well rounded; ventral margin broadly
arched; posterior margin short, nearly straightor very weakly convex; posterior dorsal marginelongated with about twice length of the anterior
dorsal margin, weakly convex; surface nearlysmooth except for several weak concentric ribs
which are very narrower than their interspaces,
occupied near the umbonal region; posteroventral corner obtusely angulated with nearlyright angle; posterior carina distinctly angulated,
extended from umbo to postero-ventral corner;
escutcheon very narrow but elongated; lunulevery narrow and short; posterior area or slope
rather broad for the genus; hinge identical withthat of Costocyrena otsukai otsukai (Yabe et
Nagao); inner margin smooth; adductor scars
very weakly impressed.
Measurements.-{in mm.)
Specimens
KSG 3896, I. ext. mol.
KSG 3897, I. ext. mol.
KSG 3898, I. ext. mol.
KSG 3899, r. ext. mol.
KSG 3900, r. ext. mol.

Length
16.0
13.0
11.0
18.0
15.5

Height
11.0
11.0
6.5
12.5
10.0

Thickness
4.0
3.5
2.0
3.0
3.5

832. Cretaceous Eomiodon and Costocyrena
KSG 3901, r. ext. mol.

15.0

10.5

3.0

KSG 3902, r. ext. mol.

17.0

9.5

3.5

Observation:-In this new subspecies, theumbonal concentric ribs are variable in number
and strength, and usually occupied about one
third from the umbo in the shell height. The
hinge structure and internal features of the valve
are entirely identical with those of Cos to cyrena
otsukai otsukai (Yabe et Nagao), from the Lower
Cretaceous of southwest Japan (Yabe, Nagao andShimizu, 1926; Hayami, 1965; Ohta, 1973,
1981 ).
Comparison: - This new subspecies differsfrom Costocyrena otsukai otsukai (Yabe et
Nagao), in its nearly smooth external surface attheir adult stage. In their younger stages thissubspecies is, however, difficult to discriminate
from C. otsukai otsukai in the same diagnostic
features. Although this subspecies resembles
Costocyrena ohnishii, sp. nov. in its sub trigonal
outline, the former differs from the latter by its
smooth surface.
Occurrence and geological age:-Dark graymudstone of the Idaira Formation at Idaira of
Inasa, Inasa-gun in Shizuoka Prefecture; Barremian or Hauterivian.
Cos to cyrena sp. cf. C. peikangensis Hayami
Figures 5-14-27

Compared with:1965. Costocyrena peikangensis Hayami, in Matsumoto,Hayami and Hashimoto, Petrol. Ceol. Taiwan, no.
4, p. 12, pI. 2, figs. 5 -6.
1975. Costocyrena peikangensis Hayami; Hayami, Univ.
Mus., Univ. Tokyo, Bull., 10, p. 140.

Materials:-KSG 3917-KSG 3921, externalmoulds of left valves; KSG 3922-KSG 3925,
external moulds of right valves; both from Kasanokawa of Okho, Nangoku City in Kochi Prefecture. KSG 3927 -KSG 3930, external moulds ofright and left valves, from Todai of Hase, Nagano
Prefecture. KSG 3926, external mould of rightvalve, from Idaira of Inasa, Inasa-gun in Shizuoka
Prefecture.
Description:-Shell small, roundly ovate inoutline, slightly longer than high, weakly in-103

flated; umbo small, prosogyrous, weakly prominent, located at about one third from front ofvalve; anterior dorsal margin shori, weakly concave; anterior margin narrowly rounded; ventral
margin broadly arched and gradually changing
into subvertical posterior margin; posterior dorsal
margin long, very weakly convex; surface ornamented with regularly spaced concentric ribs andvery fine numerous radial striae; posterior carina
weak for the genus; escutcheon narrow andlanceolate; lunule very narrow and short, distinctly separated from the disk by angulated
ridge.
Measurements:-(in mm.)
Specimens

LengthHeightKSG 3917, 1. ext. mol.

10.0

8.0

2.0

KSG 3918, 1. ext. mol.

13.0

10.0

KSG 3920, 1. ext. mol.

8.0

KSG 3922, r. ext. mol.

9.0
10.0

6.0
8.5

3.5
1.0

KSG 3923, r. ext. mol.
KSG 3930, 1. ext. mol.

8.5

9.0
7.0

Thickness

1.5
2.0

1.5

Observation:-Abundant specimens, mostly
external and internal moulds, of this species areat hand. This species is characterized by rounded
outline of the valve, and weak posterior carina
for the genus Costocyrena. The concentric ribs
are somewhat variable in number, but countable
to about 15 in some specimens. They are very
narrower than their interspaces and roof-shapedon the top. About 5 on umbonal ones are densely crowded but the other ones are widely spaced.
The radial striae on the disk generally appear on
the interspaces of the concentric ribs and its
number is about 4 in the breadth of 1 mm.
Comparison: - This species is very similar to
Costocyrena peikangensis Hayami (1965) fromthe Lower Cretaceous of Taipei in Taiwan, in
its nearly identical features of the valve. The
umbonal concentric ribs are somewhat more
crowded in this species than in C. peikangensis.
This resembles Costocyrena minor Ohta (1981)
from the Miyaji Formation of central Kyushu
in its small valve and very fine radial striae on thedisk, but the former differs from the latter inthe rounded outline and weak posterior carina.
Occurrence and geological age: - Very finegrained sandstone of the upper part of Monobe

104

Masayuki TASHIRO

Formation of the Monobegawa Group at Hokuryo of Kasanokawa, Ryoseki area, Nangoku City
in Kochi Prefecture. Dark gray siltstone of the
Ogurogawa Formation at Todai of Hase, Kamiina-gun in Nagano Prefecture. Dark gray siltstone
or very fine-grained sandstone of the Idaira Formation at Idaira of Inasa, Inasa-gun in Shizuoka
Prefecture; Lower Barremian and Hauterivian(?).

tion (Kochi), Funadani Formation (Kochi)
and basal part of the Nakaizu Formation(Tokushima) of the Nankai Group in Shikoku.
* Eomiodon matsubasensis Tamura (Lower
Cenomanian to Middle Cenomanian), Fukigoshi Formation (Kochi) of the Sotoizumi
Group in Shikoku; Mifune Group (Kumamoto) and Goshonoura Group (Kumamoto),in central Kyushu.

Distribution of Eomiodon and Costocyrena
I. Eomiodon
The stratigraphical and geographical distributions of all species of Eomiodon from the Cretaceous of Japan are summarized as follows.
* Eomiodon? kumamotoensis Tamura (Uppermost Jurassic or Lowest Cretaceous), Sakamoto Formation (Kumamoto) of the Torinosu Group in Kyushu; basal part of the A
Member of Doganaro Formation (Kochi) of
the Shimanto Terrain in Shikoku.
* Eomiodon matsumotoi Ohta (Lower Hauterivian to Barremian), "Kawaguchi" Formation (Kumamoto) of the Nankai Group(?),
lower part of the Yamabu Formation (Ohita),
Uminoura Formation (Kumamoto) in Kyushu; Shobu Formation (Tokushima) of the
Nankai Group in Shikoku; sandstone of the"Torinosu Group" at south of Birafu (Kochi)
in Shikoku; middle part of the A Member ofDoganaro Formation (Kochi) of the Shimanto
Terrain in Shikoku.
* Eomiodon nipponicus Ohta ("Neocomian":
not treated in this paper), Yoshimo Formation (Yamaguchi) of the Toyonishi Group inwest Honshu.
* Eomiodon hayamii Ohta ("Neocomian": nottreated in this paper), Yoshimo Formation(Yamaguchi) of the Toyonishi Group in west
Honshu.
* Eomiodon sakawanus (Kobayashi et Suzuki)(Aptian), upper part of the Yamabu Formation (Ohita) in Kyushu; Kaisekiyama Forma-

II. Costocyrena
The stratigraphical and geographical distributions of all species of Costocyrena in the Cretaceous of Japan are summarized as follows.
* Costocyrena ominensis (Nakazawa et Murata,
1966) ("Neocomian": not treated in thispaper), Ohshima Formation (Miyagi) of the
Kamihei Group in north Honshu.
* Costocyrena otsukai otsukai (Yabe et Nagao)(Hauterivian) Ryoseki Formation (Kochi) and
Tatsukawa Formation (Tokushima) of theMonobegawa Group in Shikoku; Kawaguchi
Formation (KumaI!loto) and Koshigoe Formation (Ohita) of the Monobegawa Group in
Kyushu; Yuasa Formation (Wakayama), Ogurogawa Formation (Nagano) and Shiroi Formation (Nagano) in central Honshu.
* Costocyrena otsukai obsoleta Tashiro (Lowere?) Barremian), Idaira Formation (Shizuoka)of the Monobegawa Group(?) in central Honshu.
* Costocyrena ohnishii Tashiro (Hauterivian),
Idaira Formation (Shizuoka) of the Monobegawa Group(?) in central Honshu, Tatsukawa
Formation (Tokushima) of the Monobegawa
Group in Shikoku.
* Costocyrena sp. cf. C. peikangensis Hayami(Hauterivian(?) to Lower Barremian), Ogurogawa Formation (Nagano) and Todai Formation (Shizuoka) in central Honshu; Monobe
Formation (Kochi) of the Monobegawa Groupin Shikoku.

---+ Figure 7. Map showing the distribution of EomiC{don and Costocyre~ during Hauterivian to Ceno~ania~
in southwest Japan. C: Costocyrena. E: Eomiodon. E: Uppermost JurassIc or lowest Cretaceous Eom/Odo~.
from the Torinosu and Shimantogawa Groups. Dotted line: Northern border line of the Kurosegawa TectOnIC
Belt.

105

832. Cretaceous Eomiodon and Costocyrena

2.1.

APTIAN
I

/

/
I

3

f

-/-;>~..)

106

Masayuki TASHIRO* Costocyrena radiatostriata (Yabe et Nagao)(Upper Barremian), Yunoki Formation (Kochi) of the Monobegawa Group in Shikoku;
Sebayashi Formation (Nagano) of central
Honshu.
* Costocyrena minor Ohta (Aptian), Miyaji
Formation (Kumamoto), basal part of the
Hinagu Formation (Kumamoto) in Kyushu;
basal member of the Hibihara Formation(Kochi) of the Monobegawa Group in Shikoku.
* Costocyrena hojiensis Tashiro (Aptian), Hoji
Formation (Tokushima) of the Monobegawa
Group in Shikoku.
* Costocyrena matsumotoi Hayami (Albian?),
Yatsushiro Formation of the Monobegawa(?)
Group in Kyushu.
* Costocyrena mifunensis Tamura (Lower Cenomanian to Middle Cenomanian), Mifune
Group (Kumamoto) and Goshonoura Group(Kumamoto) of central Kyushu.
III. Concluding remarks
In the Lower Cretaceous of Japan, the speciesof Eomiodon occur from the uppermost part ofTorinosu Group, Nankai and Shimantogawa
Groups in Southwest Japan (all of which arelocated in the southern side of Kurosegawa
Tectonic Belt), and Toyonishi Group in western
Honshu. On the contrary, Costocyrena species
distribute in the Monobegawa Group which
seems to be located in the northern side of theKurosegawa Tectonic Belt, in southwest Japan,
and Shiroi and Sebayashi Formations of Sanchu
area in central Japan, and Kamihei Group in
northeast Japan. Geographic distribution of
Eomiodon species is in a sharp contrast to thatof Costocyrena species, separated by the Kurosegawa Tectonic Belt, particularly in the Lower
Cretaceous strata of southwest Japan, except
for the Toyonishi Group which is located at
northern side of the Median Tectonic Line.
The Upper Cretaceous species of Eomiodon
and Costocyrena occur together at some localities in central Kyushu: i.e., the Goshonoura andMifune Groups. In these areas, Eomiodon is more
predominant than Costocyrena. In the Fukigoshi

Formation of the Sotoizumi Group in Shikoku,
Eomiodon matsubasensis occurs characteristically but Costocyrena species are entirely lacking.
Temporal change of geographic distributionsof two genera, Eomiodon and Costocyrena,during the Cretaceous time seem to be one of theimportant clues to testify the presence of the
Early Cretaceous lateral fault movement of theKurosegawa Tectonic Belt in the Chichibu
Terrain of Southwest Japan (Tashiro, 1985,
1986).
References
Hayami, I. (1965): Lower Cretaceous marine pelecypods of Japan, Pt. 2, Mem. Fac. Sci., Kyushu
Univ., Ser. D, Ceol., vol. 17, no. 2, p. 221-349, pIs.
27-52.
--(1975): A systematic survey of the Mesozoic
Bivalvia from Japan. Univ. Mus., Univ. Tokyo,
Bull., no. 10, p. 1-249, pIs. 1-10.
Katto, J. and Tashiro, M. (1979): A study on the molluscan faunas of the Shimanto Terrain, southwest
Japan, Pt. 1: On the bivalve fauna of the Doganaro
Formation in Susaki area, Kochi Prefecture. Res.
Rep., Kochi Univ., vol. 27, Nat. Sci., p. 143-150,
pIs. 1-2.
Kobayashi, T. and Suzuki, K. (1939): The brackish
Welden fauna of the Yoshimo beds in Provo Nagato, Japan. Japan Jour. Ceol. Ceogr., vol. 16, nos.
3-4, p. 213-224, pIs. 13-14.
Matsuda, T. (1985): Biostratigraphy of the Cretaceous
Goshonoura Group of Shishijima island, Kagoshima Prefecture. Fossils, no. 39, p. 1-15 (Palaeonto Soc. Japan).
Matsukawa, M. (1977): Cretaceous System in the eastern part of the Sanchu "Graben", Kwanto, Japan.
Jour. Ceol. Soc. Japan, vol. 83, no. 2, p. 115-126,
pIs. 1-2.
--(1979): Some problems on the Cretaceous Shiroi
Formation of the Sanchu "Graben", Kwanto
Mountainous, Japan. Ibid., vol. 85, no. 1, p. 1-9,
pI. 1.
Matsumoto, T., Hayami, I. and Hashimoto, W. (1965):
Some molluscan fossils from the buried Cretaceousof western Taiwan. Petrol. Ceol. Taiwan, no. 4, p.
1-24, pIs. 1-2.
- - , Kanmera, K. and Ohta, Y. (1980): Cephalopod
faunule from the Cretaceous Yatsushiro Formation (Kyushu) and its implications. Trans. Proc.
Palaeollt. Soc. Japan, N. S., no. 118, p. 325-338,
pI. 37.

832. Cretaceous Eomiodon and Costocyrena
Nakazawa, K. and Murata, M. (1966): On the Lower
Cretaceous fossils found near the Omine mine,
Iwate Prefecture, northeast Japan. Mem. Coil.
Sci., Univ. Kyoto, Ser. B, vol. 32, no. 4, p. 303333, pIs. 3-6.
Ohta, Y. (1973): Pelecypod family Neomiodontidae
from the Lower Neocomian of Japan. Bull. Fukuoka Univ. Educ., vol. 22, no. 3, p. 245-273, pIs.
1-4.
--(1976): Atlas of Japanese fossils, vol. 44, Mesozoic bivalves (3), Tsukiji-shokan.
--(1981): Some Lower Cretaceous Corbiculidae and
Neomiodontidae (Bivalvia) from Japan. Bull. Fukuoka Univ. Educ., vol. 31, no. 3, p. 103-134, pIs.
1-8.
--and Monji, N. (1976): On the Lower Cretaceous
Uminoura Formation in Kyushu. Ibid., vol. 26, no.
3,p.117-136.
Tamura, M. (1959): Trigoniidae, Ostreidae, BakevelIiidae, Pteriidae, Cardiidae and Astartidae from theUpper Jurassic Sakamoto Formation in central
Kyushu, Japan. Trans. Proc. Palaeont. Soc. Japan,
N. S., no. 33, p. 23-32, pI. 5.
--(1960): Upper Jurassic pelecypods from the Torinosu Group in Shikoku, Japan. Mem. Fac. Educ.,
Kumamoto Univ., vol. 8, p. 227 -244, pI. 2.
--(1977): Cenomanian bivalves from the Mifune
Group, Japan. Part 2, Ibid., vol. 26, p. 107-144,
pIs. 1-13.
Tashiro, M. (1985a): The bivalve faunas and their bio-107

stratigraphy of the Cretaceous in Japan. Ceol.
Soc. Japan, Mem., no. 26, p. 43-75.
- - (1985b): The Cretaceous System of the Chichibu
Belt in Shikoku - On the Early Cretaceous lateral
fault in the Chichibu Belt -. Fossils, no. 38, p.
23-35 (Palaeont. Soc. Japan).
--(1986): Paleobiogeography and paleoecology of
the Cretaceous System of Southwest Japan. Ibid.,
no. 41, p. 1-16.
--and Katto, J. (1986): Upper Jurassic molluscan
fossils from the Shimanto Belt in Shikoku. Res.
Rep., Kochi Univ., vol. 34, p. 121-127, pI. 1.
- - , Kozai, T., Okamura, M. and Katto, J. (1980): A
biostratigraphical study of the Lower Cretaceous
Formations of Monobe area, Kochi Prefecture,
Japan. Ceol. Paleont. Shimanto Belt, Taira andTashiro eds., Kochi, p. 71-82, pIs. 10-11.
and Matsuda, T. (1982): The bivalve fossils fromthe Cretaceous Fukigoshi Formation of the Monobe area, Shikoku. Trans. Proc. Palaeont. Soc.
Japan, N. S., no. 127, p. 393-418, pIs. 62-65.
- - , Tanaka, H. and Matsuda, T. (2983): The stratigraphy of the Cretaceous System of Haidate-yama
area, Oita Prefecture. Res. Rep., Kochi Univ., vol.
32,Nat. Sci., p. 47-54.
Yabe, H., Nagao, T. and Shimizu, S. (1926): Cretaceous
molluscan from the Sanchu Graben in the Kwanto
mountainland, Japan. Sci Rep., Tohoku Imp.
Univ., Ser. 2, vol. 11, no. 1, p. 27-100, pIs. 3-9.

Aioi .m~, Amakusa ;J(1f., Ashikita ~~t, Chikaraishi j] E, Doganaro :!it '7 ~dl!, Fukigoshi ~~, Furuyashiki tl.l!jUf(, Goshonoura mJ ffl iiIi, Haidate M fj, Hase :Iit:fr, Hibihara El.l:t JJ.i{ ,Higashikuma *~n, Higashimachi *iBJ, Hinagu El ~~, Hongo *~JlIl, Honjho *11:, Idaira {Jt>jZ, Imaizumi <tile Inasa sift., Ittku -'EL Izumi 1±llJ(, Jhoguzan .l1lLlJ, Kaganoi :J.m1U.f:!f:,Kaisekiyama fl-ELlJ, Kami ~~, Kamikatsu .lMi', Kamitanoura .lEBiiIi, Kasanokawa 'if./ )11,
Katashida ~*,EB, Katasoba )t{JtL Katsuura Mi'iiIi, Koda i'i'iiEB, Koshigoe JJ!~, Magano 1I!J!I!f,
Mashiki frii:~, Minami-Amabe -WJrili$, Miyaji 1l!\!!, Monobe Ifo/.}$, Nakaizu 9='{Jtli, Nangoku

m*,00, Obama 'N~, Odochi :kW, Ohta ::k EB, Ryoseki ~E, Sakamoto tlR
Sakawa ft. )11 ,Sebayashi ifJi#, Shimomashiki rfrii:~, Shirai S#, Shishijima lllili=f£, Shobu ~rm, Subayashi~#, Susaki ~~, Tainokawa ~JV )11, Tanoura EBiiIi, Tateishi lIE, Tatsukawa lI)ll, Todai F'Ei', Uchiyama P'.J LlJ, Uminoura 7ili iiIi, Yamabu LlJ $, Yatsushiro /\ tI;;, Yonenomoto j[: ,Yuasa ~i;lG, Yunoki flIl/*.

*

Masayuki TASHIRO

108

i1!ifliiS*S!II!*[!=;f:lc.Fl.Eomiodon C Costocyrena :i1!ifliiS*O)S!II!*[!K.~j£-t~ "i'9:.7.k1=.=;f:lc
Jt" Eomiodon c Costocyrena ~~M I..-t-:*6*, 4 fiO) Eomiodon c 8 fi 2 !ll!fiO) Costocyrena ~~lIU I..- t-: • .:t 0)t;: It Costocyrena ohnishii, sp. nov., Costocyrena hojiensis, sp. nov.,
Costocyrena otsukai obsoleta, subsp. nov. 0) 2 ~fi 1 ~!II!fi;O~~i.n ~.
""f'<mS!II!*-C-ftEomiodon O)filt~i!Ii.liJllm~1fi' J: I) fliifJIUt;:.j£ 1..-, Costocyrenalt.:tO)~~fJlU (~x:*'1fi'~.)~0~0.n~.~'<mS!II!*-C-~. ~*~mm~·mm~WK~0.n~~c<, ~-~.
;0' 0j£ 1..-, Ui U!~-:!6-ftt;:. tJ!1:I:l ~.n~.
O)$~lt, :to.:t 0 < iWJtI]S!II!*[!~*,ll,.t;:.~ '? t-:;:~X:1fi'O)~f.n.~O)~~c • • ~~.~~~cmb.n,.:tO)~~~~~-t~#~O)l~-C-t~~.
ffi~~zTrans. Proc. Palaeont. Soc. Japan, N. S., No. 147, pp. 109-116,3 Figs., October 30,1987

833. THE THIRD ADDITION TO THE SILURIAN TRILOBITE FAUNA OF
YOKOKURA-YAMA, SHIKOKU, JAPANTEIICHI KOBAYASHIThe Japan Academy, Ueno Park, Tokyo

and
TAKASHIHAMADA
Department of Earth Science and Astronomy, College of Arts and Sciences, University of Tokyo

Abstract Seven species of trilobites including two new genera and three new species arehere described from Mt. Yokokura. Metaleiolichas and Paraleiolichas are two new genera, each
represented by a new species. A new species of Japonoscutellum is added to them. Two pygidia
are new to the two known species and one pygidium is so well preserved that it is capable ofemending the existing description. Finally, a free cheek is a new find of a species for its locality.
Thus the previous knowledge of the Yokokura-yama fauna is well advanced with all of these
specimens.

A new collection of trilobites from Mt. Yokokura contains 7 species in 7 genera and 5 families, i.e. the Scutelluidae, Illaenidae, Cheiruridae,
Encrinuridae and Lichidae as follows:
1: Japonscutellum tunidum, sp. nov.
2. Bumastus glomerosus Kobayashi and Hamada,
1974
3. Cerauroides orientalis Kobayashi and Hamada,
1973
4. Encrinurus subtrigonalis Kobayashi and
Hamada, 1985
5. Metaleiolichas tuberculatus, gen. et sp. nov.
6. Paraleiolichas globulus, gen. et. sp. nov.
7. Dicranopeltis tricorn is Kobayashi and Hamada,
1986
Thus the collection contains three new species
and two new genera, namely, Metaleiolichas andParaleiolichas of the Lichidae. Among the known
species pygidia have been unknown of Cerauroides orientalis and Dicranopeltis tricorn is. Of
Bumastus glomerosus the associate pygidium tothe cephalon has been imperfect. Therefore its
description is here emended with a better specimen.
All specimens of the collection were derived
from Gomi limestone quarry except for the free
cheek of Encrinurus subtrigonalis from Sugihara.
This new occurrence confIrms the contention
that the Gomi and Sugihara trilobites horizons
are inseparable.
The authors record here their best thanks to
Dr. Jiro Katto, Professor Emeritus of Kochi
University for presentation of the new collection.
Family Scutelluidae R. and E. Richter, 1955
Genus Japonoscutel!um Pl'ibyl and Van~k, 1971
Japonoscutel!um tumidum, sp. nov.
Figures 3-3a-c

Description:-Pygidium semiparabolic in outline and distinctly vaulted with the top at about
one-fourth from anterior margin and depressednear periphery; axial lobe sub trigonal, one-fifth*Received October 29,1986; Studies on Japanese Trilobites and Associated Fossils-XLVIII.
109

110

Teiichi KOBA YASHI and Takashi HAMADA

as broad as anterior margin; its median part distinctly elevated above lateral parts; median rib
similar to seven lateral ones on each side inbreadth and prominence in anterior, but more
broadened and bifurcate in posterior; all ribs
crossed by concentric lirae; pleural furrows
narrower than ribs near axial lobe, but becoming
much wider near postero-Iateral margin.
Comparison:-This pygidium is tentatively
referred to Japonoscutellum, because it resembles Japonoscutellum japonicum and J. geniculatum in outline and some other aspects. The pygidium is slanting at about one-third from the posterior periphery in J. genicula tum Kobayashi
and Hamada, 1985. Incidentally, the median rib
is bifurcate in this specimen as well as J. japonicum as seen in the pygidia in fig. 5, pI. 4 and fig.
15, pI. 5 (Kobayashi and Hamada, 1974).
Occun-ence:-Limestone, Gomi Quarry, KochL
Family Illaenidae Hawle and Corda, 1849
Genus Bumastus Murchison, 1839
Bumastus glomerosus Kobayashi and Hamada
Figures 1-A, 2-1a-d

1974. Bumastus glomerosus Kobayashi and Hamada
Palaeont. Soc. Japan, Spec. Pap., no. 18, p. 47:
pI. 1, figs. 3 -8, text-fig. 2A.

Pygidium more or less elliptical, but more wellrounded on posterior side than the other, itsratio of length to breadth being 11 to 25; maximum breadth through near one-third of lengthfrom anterior margin where it is most convex·
convexity there corresponding to about a half of
pygidial length; axial lobe limited by distinct
depressions on its lateral sides half as wide as
pygidium.
The pygidium here described is better preserved than the two above cited (1974). The
anterior margin is broadly arcuate, instead ofstraight as previously restored in text-fig. 2A.
This pygidium is simply convex without flattened marginal border as in the previous description. Only very fine striae are discernible near
the margin. Otherwise the test is smooth.
Occun-ence:-Limestone, Gomi Quarry.

Family Cheiruridae Hawle and Corda, 1847
Genus Cerauroides Prantl and Pl'ibyl, 1946
Cerauroides orienta lis Kobayashi and Hamada
Figures 1-C, 2-3

1973. Cerauroides orientalis Kobayashi and Hamada,
Proc. Japan Acad., v. 47, no. 8, p. 547, text-figs.
1-5.
1974. Cerauroides orienta lis Kobayashi and Hamada,
Palaeont. Soc. Japan, Spec. Pap., no. 18, p. 84,
pI. 6, figs., 1-4, text-fig. 6A.

The pygidium is composed of four segments;
axial lobe a little broader than one-third of pygidium, but its relative breadth reducing posteiorly; first pleura very large and produced back intoa long spine; second pleura of moderate size terminating at a minute spine; succeeding two
pleurae fused and embracing posterior part ofaxis; two large posterior spines only a little divergent backwards; test smooth.
Compared to Cerauroides lunshanensis(Grabau, 1924) the first pair of pleural spines
are not so widely divergent and the second pairof spines rudimentary in this species. Otherwise
both of them have the construction very similar
to each other. In the slight divergence of the posterior spines it is nearer to the pygidium of
Ceraurinium intermedium (Kielan, 1955) fromthe Ashgillian of Poland, but the spines are
straight and the posterior margin of the pygidium
is entire in that species.
This pygidium belongs probably to either
Cerauroides orientalis or C. elongatus both ofwhich occur at Gomi quarry where the pygidium
was collected. It is provisionally located in theformer species simply because, it is more common and better known than the latter species. It
is noted here that the hypostoma of Cerauroides
orientalis is closely allied to that of Ceraurinium
intermedium, although the posterior margin issinuated in C. orientalis.
Occun-ence:-Limestone, Gomi Quarry.
Family Encrinuridae Angelin, 1854
Genus Encrinurus Emmrich, 1844
Encrinurus subtrigonalis Kobayashi and Hamada833. Silurian Trilobites of Shikoku

111cFigure 1. Reconstruction of five trilobite species from Yokokura-yama.
A. Bumastus glomerosus Kobayashi and Hamada, 1974, x6; B. Metaleioleichas tuberculatus, gen. et sp. nov.,
x5; C. Cerauroides orienta lis Kobayashi and Hamada, 1973, x3; D. Dicranopeltis tricorn is Kobayashi and
Hamada, 1986, x3; E. Paraleiolichas globulus, gen. et ep. nov., x8.
Figures 3-2a, b
1985. Encrinurus subtrigonalis Kobayashi and Hamada,Trans. Proc. Palaeont. Soc. Japan, N. S., no. 139,
p. 210, pI. 28, figs. 4a-c, pI. 29, figs. 2a-d.

A right free cheek of Encrinurus has an eyeof medium size from which the proparian facial
suture extends to the lateral margin of the cephaIon. It is densely granulate and most granules;

11 2

Teiichi KOBA YASHI and Takashi HAMADA

833. Silurian Trilobites of Shikoku

113

have a central pit. This is the characteristic texture of the cephalon of Encrinurus subtrigonalis.
Therefore this is the new find of this species at
Sugihara.
Occurrence: -Tuffaceous sandy shale; Sugihara.

Generic characteristics are included in thedescription of the monotypic species.

Family Lichinae Hawle and Corda, 1874

Metaleiolichas tuberculatus, sp. nov.

The group of Leiolichas Schmidt, 1885 in the
Lichidae was represented only by Lichas illaenoides Nierzkowsky, 1857 which occurs in theUpper Ordovician in East Baltic region and alsoin North Germany in Ordovician boulders. Its
shield is quite smooth and the furrows are weak,although they are distinct in casts. Later Warburg(1939) described Leiolichas illaenoides from theMacrourus limestone of Oland found in boulders.
The two genera, Metaleiolichas and Paraleiolichas, proposed here best agree with Leiolichas
in the fundamental configuration of the cranidium, but they are different from that genus in
the median lobe much larger, the median, bicomposite and basal lobes each forming a swell, theirboundary furrows all strongly excavated in theirwhole length and the surface densely granulate.
In Leiolichas, on the contrary, the test is smooth,the median lobe relatively narrow, this lobe constitutes the same dome with lateral and basal
lobes and the longitudinal furrows become obsolete near the occipital ring.
These two new genera differ from each otherin the general outline of the cranidum and themode of its division into lobes, as detailed later.
An additional distinction is found in the periphery of the cephalon. It is represented by nontuberculate rim and strong marginal furrow in
Metaleiolichas and by a depressed and tuberculate band on the outer side and the linear furrow

Figures I-B, 3-4a-c

in the inner side in Paraleiolichas.
Genus Metaleiolichas, gen. nov.

An imperfect cranidium having median lobe,
a narrow bicomposite left lobe and a small left
basal lobe which are all outlined clearly by persistent furrows; median lobe strongly convex,
broad and much more expanded in anterior
than posterior; bicomposite lobe narrowing backward, strongly convex, but its top near longitudinal furrow a little below median lobe; basal lobe
fusiform, elongated laterally. Axial furrow, posterior marginal furrow and terminus of OCCipital
furrow are all preserved. Surface ornamented
with tubercles of different sizes except for frontal rim and furrows.
This· cranidium agrees with Leiolichas in thefundamental configuration, but the median lobe
is incomparably developed, longitudinal furrow
persistent in its whole length and the test densely
tuberculate.
Occurrence:-Limestone, Gomi Quarry.
Genus Paraleiolichas, gen. nov.

Paraleiolichas globulus, sp. nov.
Figures l-E, 2-4, 3-1a-b

Cranidium globular; median lobe subcylindrical in middle part, but a little expanded inposterior and remarkably flaring in anterior; bicomposite lobe semiglobular and medium sized;+- Figures 2-1a-d. BUTlUlstus glomerosus Kobayashi and Hamada, 1974, dorsal, anterior, posterior and leftlateral views of a well-preserved pygidium. x6.S PA18089.
.
..
2. Dicranopeltis tricorn is Kobayashi and Hamada, 1986, a dorsal view of an Incomplete pygldlllm. x3.4
PA 18092.

'd'35

3. Cerauroides orientalis Kobayashi and Hamada, 1973, a dorsal view of an incomplete pygl mm. x .

PA 18090.

4. Paraleiolichas globulus, gen. et sp. nov., a posterior view of the holotype caranidium. x6.S PA 18094.
(vide Figures 3-1a, b)

114

Teiichi KOBAYASHI and Takashi HAMADA

833. Silurian Trilobites of Shikoku

basal lobe relatively large and trigonally ovoid;these glabellar lobes and fixed cheek all granulate
and completely separated from one another by
deep furrows; frontal border flat, depressed,
granulate and limited inside by linear furrow.
Compared to Metaliolichas this cranidium islonger in outline, its basal lobe much larger incomparison with the bicomposite lobe. Nevertheless, they have same pattern and quite distinct
from Leiolichas in the development of themedian lobe, persistent glabellar furrrows anddense granulation or tuberculation.
Occurrence:-Limestone, Gomi Quarry.
Genus Dicranopeitis Hawle and Cords, 1974
Dicranopeltis tricomis Kobayashi and Hamada
Figures 1-0, 2-2
1986. Dicranopeltis tricorn is Kobayashi and Hamada,Trans. Proc. Pal. Soc. Japan, N. S., no. 143, p.
458, pI. 92, figs. la-g, text-figs. CI-3.

This species was instituted with a cephalon
resembling Dicranopeitis scabra, but having a
median spine issuing from the top of the glabella
besides a pair of long genal spines. The pygidium
now at hand is such a fragmentary specimen inwhich only the axial part is preserved. It is, however, astonishing that it coincided with the pygidium of D. scabra so nicely as shown in textfig. 4.
The axial lobe of this pygidium consists of
two axial rings which are very short (sag.) andwell defined by deep ring furrows, the third axial
ring which is so large that two rings can be fused
and the long terminal piece which is graduallytapering back without any lateral expansion as
seen in D. scabra. The third pleura is divided into
two bands by an interpleural furrow as seen on
the left side of the terminal piece. On the other115side, there is the posterior band of the third
pleura. All of them are, however, exfoliated inposterior where the doublure of similar breadth
as that of D. scabra is exposed. In tracing terracelines it is recognizable that the third pleura isending at a short spine. The most important distinction of this pygidium from D. scabra lies in
the possession of a stout spine as shown by its
scar on the third axial ring. Like the cephalon ofthis species fine granules are distributed densely
on the surface.
Occurrence:-Limestone, Gomi Quarry.
References
Grabau, A. W. (1924): Stratigraphy of China, Part 1,
Palcozoic and Supplement. 538 pp., 6 pis.
- - (1925): Summary of the fauna from the Sintan
shale. Bull. Ceol. Surv. China, no. 7.
Kielan, Z. (1955): A ncw trilobite of the genus Ceraurus
and the significance of cephalic spines in the ontogeny and phylogeny of trilobites. Acta Ceol. PoL,
v. 5, (2), p. 215-240.
- - (1959): Upper Ordovician Trilobites from Poland
and some related forms from Bohemia and Scandinavia. Palaeont. Pol., no. 11, 198 pp., 36 pis.
Kobayashi, T. and Hamada, T. (1973): Brief notes on
Silurian trilobites from Mt. Yokokura, Shikoku
Island. Proc. Japan A cad. , v. 49, no. 7, p. 540-544.
--and - - (1974): Silurina Trilobites of Japan incomparison with Asian, Pacific and other faunas.
Palaeont. Soc. Japan, Spec. Pap., no. 18, 155 pp.,12 pis.
and - - (1985): Additional Silurian trilobites to
the Yokokura-yama fauna from Shikoku, Japan.
Trans. Proc. Pali1eont. Soc. Japan, N. S., no. 139,
p. 206-217, pis. 28-30.
and - - (1986): Thc second addition to the
Silurian Trilobites Fauna of Yokokura-yama,
Shikoku, Japan. Ibid., no. 143, p. 447-462, pis.
90-92.
Phleger, F. B. Jr. (1936): Lichian trilobites. Jour. Paleont., v. 10, p. 593-615, figs. 1-83.
--(1937): Further notes on thc Lichadacea. Ibid., v.

~ Figures 3-1a, b.
Paraleiolichas globuills, gen. ct sp. nov., dorsal and frontal views of the holotype crani'dium. x6.5 PA 18094. (vide Figure 2-4).
2a, b. Encrinurus subtrigol1alis Kobayashi and Hamada, 1985, a free cheek (inner mOUld). x3.5 PA 18091.
3a-c. Japonoscutellum tunidum, sp. nov., dorsal, left lateral and posterior views of hte holotype pygidium.
x3.3 PA 18088.
4a-c. Metaleiolichas tllberculatlls, gen. et sp. nov., frontal, dorsal and left lateral views of the holotype
cranidium. x6.6 PA 18093.

Teiichi KOBA YASHI and Takashi HAMADA

116

11, p. 253-256.
-(1937): New Lichadacea in the collection of theMuseum of Practical Zoology. Harvard Univ. Mus.
Compo Zool. Bull., v. 80, p. 415-425, pIs. 1-2.
Plibyl A., Vanek, J. and Pek, I. (1985): Phylogeny andtaxonomy of Family Cheiruridae (Trilobita). Acta
Univ. Aoakckiana Olomucensis, Rac. Rerum Natur.
Geogr.-Geol., 24, v. 83, p. 107-193 (8 pIs.).

Schmidt, Fr. (1885): Revision der Ostaltischen Silurien
Trilobiten, Abt. 2, Acidaspiden und Lichiden.
Mem [,Acad. Imp. de Sci. St.-petersbourg, VIle,
Ser. Tom. 31, no. 1,127 pp., 6 pIs.
Warburg, E. (1939): The Swedish Ordovician and Lower
Silurian Lichidae. KungL Sevenska Veten.-Akad.
Handl., 3 Ser, Bd. K7, no. r, 162 pp., 14 pIs.

~oo~*w~~~e~~~W~~.3~~:*~~K~5W7~K~~~7~~E~L~~~o-t~ ? ~~::. 2 fi~ Metaleiolichas, Paraleiolichas iJ~~ IJ, ~t::.fi~~::.£--::)\"~ \" ~o -t~ff!!t::. 1
fi~iJ~~~o ~~~ 4 ~JfI~::.~~tlRiJ~fit.:t::.~U-? t.: ~ ~ 2~, ~tlR~~ff'&Rrt.ct.:6bt::'JlUD~Bc~~fftnE~~ ~ ~,-t L ~£::!tl!.!: L ~fi L\" ~ OJt.c CiJt~ IJ, foJ.tL ~ iJtfi%IJ!~#1.m L ~\"~o'J':fHi-, ~EE~±Trans. Proc. Palaeont. Soc. Japan, N. S., No. 147, pp. 117-130,5 Figs., October 30,1987

834. EARLY CARBONIFEROUS EOSTAFFELLA (PRIMITIVE FUSULINACEA)FROM THE ICHINOTANI FORMATION, FUKUJI DISTRICT, CENTRAL JAPAN*
SHUn NIKO
Department of Earth Science and Astronomy, College of Arts and Sciences,
The University of Tokyo, Komaba, Tokyo 153

Abstract. The lower part of the Ichinotani Formation at Fukuji, Gifu Prefecture, central
Japan contains a very rich assemblage of foraminifers. Eostaffella (primitive fusulinacea) is
described here to provide a basis for the precise biostratigraphic su bdivision and age-determination of the lower Ichinotani Formation. The eostaffelloids consist of eight species including
three new species, i.e., Eostaffella excavata, E. igoi and E. subulba. This assemblage permits
recognition of Igo's Eostaffella kanmerai zone ranging from latest Visean to early Serpukhovian(Namurian A) in age.

Introduction
Eight species of eostaffelloid fusulinaceans
are described in this paper from the lower partof the Ichinotani Formation in the Fukuji district, Gifu Prefecture, central Japan. The Ichinotani Formation is exposed mainly in the Ichinotani Valley, Mizuboradani Valley and lower
course of the Mizuyagadani Valley in a series of
NEE-SWW trending small faulted blocks, andcomprises about 350 m thick of predominatingly
carbonate rocks of late Early Carboniferous to
Early Permian in age.
Material for systematic study was collectedfrom two localities as listed below and shown in
Figure 1.
Locality A: Middle course of the Ichinotani
Valley.
Locality B: On the mountain slope facing
south of the same valley.
The continuous outcrops at the locality A allow
to measure a complete columnar section and to
determine the occurrence-boundary of many
fossils, although in the locality B outcrops are

1km
CONTOUR
INTER VA L 50M

Figure 1.
*Received October 30, 1986; reviscd manuscript accepted Septembcr 18, 1987.
117

Map showing the fossil localities.

Shuji NJKO

118

2m

~NS61

o

~

o

"'-- NS48" ' - NS 19

-

~NS54

s ma II fa u l t -l-

L NS40" ' - NS46"'--NS18"'--NS41
~

oq:
I-

-

~

~NS35

:::l

"'---- N 5 42""--- T2 5

"

I-

o

~

"'-- NS 12

v

v

v

"'-- NS43"'--NS 10

122~:J--- fa u I t - - -

~1

m

~2

l:o~T
I6
0'·
0

~3

D

4

S

.~ .

v

v

v

7

~NS10 8Figure 2. Columnar section s sho wing th e lithology and stratigraphic po sition s o f samples
at locality A, th e middle course o f th e Ic hinota ni Valley. 1: thic k-bedd ed lim estone ; 2 : thinbedded lim estone; 3 : thin alternating bed s of lim estone a nd shale ; 4 : shal e; 5 : lim es tone withchert concre tion s; 6 : conglom erate ; 7: d yke rock ; 8 : sample number and locatio n,

834. Eostaffella from the Jchinotani Formation
poor due to thick vegetation. The other purposeof this article is to analyze stratigraphic distribution of foraminifera for a basis of biostratigraphic subdivision and precise correlation with thefaunal successions in the standard areas of Upperand Lower Carboniferous boundary in West
Europe and U.S.S.R.
Accounts of the foraminiferal successions of
this formation have been presented by Igo (1956,
1957), Niikawa (1978, 1980), Igo and Adachi(1981a), Igo, Adachi and Igo (1984), Adachi(1985) and Niko (1985, 1986). Further, lithostratigraphically, Igo and Adachi (1981a) and
Adachi (1985) divided the Ichinotani Formation
into three members, 61 Unit-beds. The primitive
fusulinacean assemblage of the present study isrelated with the lowest Unit 1 ofIgo and Adachi's
scheme, and thus it falls within the lowermost
fusulinacean zone of Eostaffella kanmerai zone,
which probably ranges from latest Visean toearly Serpukhovian (Namurian A) in age (Niko,
1986).
At the type section (locality A) Unit 1 of thisformation is 9.5 m thick, and is composed of a(basal?) conglomerate bed of 1.5 m thick being
succeeded by a thin bedded black to dark-graylimestone (6.3 m) and further by an alternationof limestone and thin shale (1.7 m). The (basal?)

119conglomerate is characterized by the predominance of ill-sorted and sub angular volcanic fragments of acidic composition (Niko et al., 1984).
Most of the carbonates of Unit 1 is made up ofskeletal grains, peloids, and with extra clast(acidic volcanic fragments), and are predominatingly packstone and wackestone with minor
amounts of grainstone and lime mudstone.
Besides the rich assemblage of foraminifers,
these limestones contain many corals including
Kueichouphyllum, Dibunophyllum, Heterocaninia, Neokoninckophyllum, Siphonodendronand others (Kato, 1959; Igo and Adachi, 1981betc.), and such other fossils as productid brachiopods (Tazawa and Kato, 1986), bryozoans (Sakagami, 1960), trilobites, crinoids and ostracods.
Specimens used in this study are stored in thefollowing institutions:
IGUT Institute of Geoscience, The University of Tsukuba.
UMUT University Museum, The University ofTokyo.
Systematic paleontology
Family Eostaffellidae Mamet in Mamet,
Mikhailov and Mortelmans, 1970
Genus Eostaffella Rauzer-Chernousova, 1948

Table 1. Occurrences of Eostaffella in the Ichinotani Formation. The stratigraphic positions of samples are shown in
Figure 2, except for samples from "float blocks" (*) of limestone.
Locality B

Locality A
Sample No.

Taxon

Eostaffella excavata

- --

-"<t
Ul Ul

N

N
"<t
Ul

co

"<t
Ul

x x x x x x

E. igoi\DM\Dx x x x x

- - -... ...'"

x

U

Cl

*

U

Cl

x

x
x

x

x

x

?

*

x

x

x
x
x

~

x

x

E. cf. postmosquensis

E. sp.

\D~

E. mosquensis

E. tenebrosa\Dx

E. kanmerai

E. subulba-** * *'" *0'" 0"<t "<tco "<t - *r- J::t:: *'""<t ...
'"
J::t::
J::t:: J::t:: J::t::Ul '"Ul Ul Ul Ul Ul Ul '"NUl Ul r- Ul Ul UlUZ Z Z E-< Z Z Z Z Z Z Z Z Z Z E-< Z Z Z < < Cl

OM

x

x
x

x

ShujiNIKO

120

Type species:-Staffella (Eostaffella) parastruvei Rauzer-Chernou sova, 1948.
Eostaffella excavata Niko , sp. nov.
Figures 3-A- H

Material studied:-Holotype , UMUT PF 18013(sample NS 40 , Figure 3-A); para types UMUT PF
18014 (sample NS 40, Figure 3·B), 18015 (sample NS 42, Figure 3-F), 18016 (sample T2 5,
Figure 3-C), 18017 (sample T2 5, Figure 3-E),
18018 (sample T2 5, Figure 3-D), 18019 (sample
NS 41 , Figure 3-H), 18020 (sample T2 5, Figure3-G). In addition to the holotype and paratypes,
some other specimens were studied. All the speci·
mens were obtained from loc. A.
Diagnosis: - Small Eostaffella with discoidal
test , broadly umbilicate on both sides, androunded periphery in the last volution. Coiling
plectogyroid in juvenarium, becoming planispiralin outer volutions. Septa long, slightly curved.

Description :- Test is small , discoidal, withbroadly umbilicate on both sides. Periphery is
bluntly pointed in the inner volutions but thelast volution of the mature specimens has arounded periphery. The holotype (Figure 3-A)
contains 5 volutions that is 0.l95 mm in lengthand 0.46 mm in width; form .ratio is 0.42. Radius
vectors of the third to fifth volutions of the holotype are 0.08, 0.l5 , and 0 .26 mm , respectively .
The initial 1 to 1 1/2 volutions are skew at nearly
90 degrees to the remaining essentially planispiral
whorls. The last volu tion is partially evolute.
Proloculus is nearly constant in size in the examined specimens, being 0 .017 to 0.019 mm in
its inside diameter. Wall , approximately 0 .008
mm thick in the outer volutions, consists of atectum , and lower and upper tectoria. Septa are
long, slightly curved , and inclined forward.
Septal counts of the seco nd to forth volutionsof a paratype (Figure 3-H) are 9 , 11 , and 12,
respectively . Tunnel is low and narrow. Asym-

Figure 3. A - H, Eostaffella excavata, sp. nov. A, axial section of the holotyp e, UMUT PF 18013. B,
tangential section of a paratype, UMUT PF 18014 . C, axia l section of a paratype, UMUT PF 18016. D, axial
section of a paratype, UMUT PF 18018. E, axial section of a paratype, UMUT PF 18017. F, axial sectio n of apara typ e, UMUT PF 18015. G, neary sagitta l sect ion of a paratype, UMUT PF 18020. H, sagittal section of aparatype, UMUT PF 18035 . I-K, Eostaffella cf. postmosquensis Kireeva. I, axial section, UMUT PF 18035. J ,slightly diagonal sectio n, UMUT PF 18036. K, axial section, UMUT PF 18037. All specimens XI00.

834. Eostaffella from the Ichinotani Formation
metrical chomata are present in the outer volutions. Aperture is low and basal.
Remarks:-This new species belongs to Eostaffella of the group E. pseudostruvei that consistsof the following species:
pseudostruvei (Rauzer-Chernousova andBeljaev, 1936)
p. var. angusta Kireeva, 1951
p. var. chomatifera Kireeva, 1951
p. var. elegantissima Manukalova, Il'ina andSerezhikova, 1969
p. var. losovskensis Manukalova, Il'ina andSerezhikova, 1969
excavata Niko (this report)
Eostaffella excavata is most closely allied toE. pseudostruvei var. angusta Kireeva from thelower Bashkirian of the Donetz Basin and Russian Platform of U.S.S.R. in essential features,
but the former is different from the latter inhaving smaller proloculus. The present species
somewhat resembles E. pseudostruvei var.
chomatifera Kireeva, but E. excavata differs in
its smaller size and by its weaker chomata, andmore round·ed periphery in the last volution.
Evolute coiling of the last volution suggests
an assignment of this species to other genera,
especially Millerella and Zellerina. However, thisform differs from Millerella by its plectogyroid
coiling in juvenarium and less numerous septal
counts; and from Zellerina by its bluntly pointed
periphery in the inner volutions and well differentiated spirotheca.

Eostaffella igoi Niko, sp. nov.
Figures 4-A-E

Material studied:-Holotype, UMUT PF 18021(sample T2 5, Figure 4-b); paratypes, UMUT PF
18022 (sample T2 5, Figure 4-A), 18023 (sample
T2 5, Figure 4-D), 18024 (sample T2 5, Figure4-C), 18025 (sample T2 5, Figure 4-E). In addition to the holotype and paratypes, some otherspecimens were studied. All specimens from loco
A except for two ill-oriented specimens thatwere obtained from loco B.
Diagnosis:-Large Eostaffella with discoidal tolenticular test, pointed periphery and nearly121

straight to slightly concave lateral slopes. Coiling more or less planispiral. Spirotheca relatively
thick. Septa short and straight. Chomata welldeveloped.
Description:-Test of Eostaffella igoi, sp. nov.
is larger for the genus, and discoidal to lenticularshape with umbilicate on both sides. Umbilicus
is relatively well-developed in the last volution.
Periphery is pointed in axial section and lateralslopes are nearly straight to slightly concave.
Mature specimens of 5 1/2 volutions are 0.36 to
0.38 mm in length and 0.65 to approximately
0.73 mm in width, giving form ratios of approximately 0.52. Radius vectors of the first to fifth
volutions of the holotype (Figure 4-C) are 0.04,
0.08,0.12,0.20, and 0.32, respectively. Proloculus is approximately 0.030 mm in inside diameter. Coiling is more or less planispiral. Septa
are short, straight and usually inclined forward.
Septal sutures are slightly depressed in the outer
volutions. Septal counts of the first to fifth volutions of a paratype (Figure 4-E) are 5,9,10,13,
and 14, respectively. Wall is calcareous, microgranular and approximately 0.010 to 0.013 mm
thick in the outer volutions. It is differentiatedinto thin tectum, and lower and upper tectoria.
Supplemental deposits, in form of an asymmetrical chomata, are well-developed in the outer
volutions. Tunnel is relatively high and narrow.
Aperture is low, basal and simple.
Remarks:-Eostaffella igoi somewhat resembles E. kanmerai (I go) from the Ichinotani Formation and E. oregonensis Sada and Danner fromthe Late Mississippian (Chesterian) Coffee Creek
Formation of central Oregon. E. kanmerai, however, has a smaller shell and lower form ratio,
and its coiling is somewhat irregular. E. oregonensis has a lower form ratio, weaker chomata,and deeper umbilical depression. In the generalshape of E. columbiana Sada and Danner from
British Columbia somewhat resembles examined
specimens which nevertheless have smaller numbers of shorter septa. Illustrated specimens ofE. columbiana suggest the presence of diaphanotheca. There would be some possibility that
this species might belong to a genus Pseudoendo-

thyra.

122

ShujiNIKO

834. Eostaffella from the Ichinotani Formation
Eostaffella kanmerai (Igo)
Figures 4·H-J
Millerella kanmerai Igo, 1957, p. 175-177, pI. 1, figs.
20-26, pI. 2, fig. 14.
Eostaffella kanmerai (Igo): Sada, 1964, p. 230-231, pI.
21, figs. 8,16-17; Sada, 1967, p. 144-145, pI. 12,
figs. 1-10; Sada, 1969, p. l20-121, pI. 12, figs. 112, 13?, pl. 13, figS. 1-2; Reitlinger, 1973, p. 62,
pI. 10, figS. 18-19, pI. 11, figs. 5-6; Sada andDanner, 1974, p. 259-261, pI. 37, figs. 1-3,5,1819; Sada, 1975, p. 35-36, pl. 8, figs. 1-5; Niikawa,
1978, p. 538, pI. 1, figs. 11-12; Sada, 1980, p. 6869, pI. 1, figs. 1-5, 11-13; Rich, 1980, p. 40-41,
pI. 18, figs. 6, 8-12, 14?; Sada, Nomura and Oho,
1984, p. 390-391, pI. 75, figs. 1-8.
Eostaffella cr. kanmerai (lgo): Massa and Vachard,
1979, pi. 6, fig. 5.

Material studied:-Four specimens (UMUT PF
18026, sample NS 18, Figure 4-H; 18027, sample
NS 54, Figure 4-1; and two unfigured specimens)
are referred to this species.
Remarks:-Here no description of this species
is given, because none of the well-oriented andcomplete materials were recovered during thepresent study even they came from the type
locality.
The combination of morphological features ofthis species suggest a relationship to the following species; Eostaffella igoi Niko (this report),
E. infulaeformis Ganelina, E. oregonensis Sada
and Danner, E. pseudostruvei (Rauzer-Chernousova and Beljaev), E. toriyamai Ozawa, but E.
kanmerai is recognized by its somewhat irregularcoiling of volutions and weak chomata.
Igo's holotype (1957, pI. 1, fig. 20) is reillustrated in this report in order to show its
complete morphology.
Eostaffella mosquensis Vissarionova, 1948
Figures 5-D, F, G, H?

123

Eostaffella mosquensis Vissarionova, 1948, p. 222, pI.
14, figs. 4-6; Ganelina, 1951, p. 188-189, pI. 2,
figs. 1-2; Brazhnikova et al., 1956, pi. 15, figs. 911; Golubtsov, 1957, p. 165-166, pI. 9, figs. 20-21;
Durkina, 1959, p. 196-197, pI. 20, fig. 10; Bogush
and Iuferev, 1962, p. 172, pI. 6, fig. 26; Rozovskaia,
1963, p. 93-94, pI. 16, figs. 16-17,pl.I7,figs. I5; Manukalova-Grebeniuk, Il'ina and Serezhnikova,
1969, p. 25, pI. 9, figs. 9-12; Malakhova, 1972, p.
40, pi. 7, figs. 1-3; Ivanova, 1973a, pI. 7, fig. 6; Wu,
Chang and Ching, 1974, pl. 4, fig. 10; Ozawa, 1976,
p. 121-122, pI. 22, figs. 1-15, 16?, 17-19; Niikawa, 1978, p. 538, pI. 1, figs. 5-7, 15; Rich, 1980,
p. 41, pI. 18, figs. 13, 15-16, 20, 25; Matsusue,
1986, pI. 6, figs. 1-2.
Eostaffella mosquensis mosquensis Vissarionova:
Vachard, 1977, pI. 5, fig. 23.
Eostaffella mosquensis acuta Rauzer-Chernousova, 1948,
p. 236-237, pI. 14, fig. 5; Ganelina, 1951, p. 190191, pi. 2, figs. 3-4; Brazhnikova et al., 1956, pI.
15, figs. 5-7; Golubtsov, 1957, p. 166-167, pI. 9,
figs. 22- 25; Vachard, 1977, pI. 5, fig. 22.
Eostaffella acuta Rauzer-Chernousova: Armstrong andMarnet, 1977, p. 85.

Material studied:-Specimens induding four
axial sections (UMUT PF 18032, sample NSR 5,
Figure 5-G; 18033, sample DC 19, Figure 5-D;
18034, sample NSR 5, Figure 5-F; and one unfigured specimen), one tangential section, andone sagittal section (UMUT PF 18070, sample
NSR 5, Figure 5-H) of questionable assignment
to this species were examined. All specimens
were obtained from loco A except for UMUT PF
18033 from loco B.
Description: -Test is moderately large for the
genus, involute, and umbilicate on both sides.
Periphery is rounded to bluntly pointed in axial
section, and lateral slopes are broadly convex.
Mature specimens contain 5 1/2 volutions thatare 0.32 to 0.37 mm in length and 0.56 to 0.62mm in width. Form ratio ranges from 0.58 to
0.60. Radius vectors of the first to sixth (5 1/2)
volutions of the typical specimen (Figure 5-G)+- Figure 4. A-E, Eostaffella igoi, sp. nov. A, diagonal section of a paratype, UMU~ PF 18022. B, incomplete axial section of the holotype, UMUT PF 18021. C, axial section of a paratype (Immature), UMUT PF
18024. D, axial section of a paratype (immature), UMUT PF 18023. E, sa~ittal se~tion of a paratype, UMUT ~F
18025. F. G, Eostaffella tenebrosa Vissarionova. F, axial (slightly tangential) sec.hon, UMUT PF 18040. G, ax~alsection, UMUT PF 18038.. H-J, Eostaffella kanmerai (lgo). H, diagonal sechon, UMUT P~ 18026. ~, aXial(slightly tangential) section of the holotype, IGUT 20369 (reillustration of Igo, 1957, pI. 1, fig. 20). J, I~com. I sec t'iOn, UMUT PF 18027.K
sp. , axial section, UMUT PF 18041. All specimens, Eostafj'l'ellaJ'plete tangenha
X100.

124

Shuji NIKO

834. Eostaffella from the !chinotani Formation
are 0.02(?), 0.06,0.10,0.16, 0.25, and 0.32, respectively. The initial 1 to 1 1/2 volutions are
skew at approximately 40 degrees to the remaining essentially planispiral volutions. Proloculus is0.024 to 0.033 mm in inside diameter. Chamberincreases in height uniformly throughout thegrowth. Wall consists of a thin tectum, and lower
and upper tectoria; it is 0.010 to 0.014 mm thickin the final volution. Tunnel is low and narrow
except for the ultimate volution which is wider
than the penultimate one. Weak, slightly asymmetrical chomata are present in the outer 2 or 3
volutions, its both (tunnel side and polewardside) sides are relatively gentle, occasionally extending to poles.
Remarks:-This species has considerably wide
variation in the shape of periphery in the outer
volutions. However, in the immature stage thesize and skewness of coiling of examined specimens are nearly equal. Specimen having
pointed periphery (Figure 5-D) could be classified as Eostaffella mosquensis acuta RauzerChernousova, but Rozovskaia (1963) has shownthat E. mosquensis acuta is synonymous with E.
mosquensis. Her classification is followed in thispaper.
This species has been recorded from theUpper Visean (Alexinsky to Michailovsky horizons) of the Russian Platform and Urals, fromthe Lower Serpukhovian (C~) of the Donetz
Basin, from the Upper Visean (V 3b-V 3C) of West
Europe, and from the Upper Chesterian (Zone18) of North America.

Eostaffella cf. postmosquensis Kireeva, 1951
Figures 3-I-K

Compare:Eostaffella postmosquensis Kireeva, 1951, p. 48-49, pI.
1, figs. 1-2; Bogush and Iuferev, 1962, p. 178-179,

125

pI. 7, fig. 3; Brazhinikova et al., 1967, pI. 21, fig. 7;
Manukalova-Grebeniuk, lI'ina and Serezhikova
1969, p. 25-26, pI. 6, figs. 9-11; Watanabe, 1973:
p. 377-378, pI. 51, figs. 9-14; Ivanova, 1973a, pI.
2, figs. 5-7, pI. 4, figs. 11-12; Reitlinger, 1973, p.
62, pI. 10, figs. 1-2; Matsusue, 1986, pI. 6, fig. 8.
E. postmosquensis postmosquensis Kireeva: Grozdilova
and Lebedeva, 1954, p. 114-115, pI. 14, fig. 9.
E. ex. gr. postmosquensis Kireeva: Ivanova, 1973a, pI.
30, fig. 17.

Material studied:-Description is based on two
axial sections (UMUT PF 18035, sample NS 31,
Figure 3-1; 18037, sample NSR 5, Figure 3-K)
and one slightly diagonal section (UMUT PF
18036, sample NSR 5, Figure 3-1). All specimens
were obtained from loco A.
Description:-Test is small for the genus,
deeply umbilicate on both sides. Periphery isrounded in axial section through all growth stageof the shell. Lateral slopes are broadly convex.
Mature specimens contain 4 1/2 volutions thatare 0.17 to 0.22 mm in length and 0.35 to 0.37
mm in width. Form ratio ranges from 0.50 to
0.59. The initial 1 to 2 volutions are skew to theremaining essentially planispiral volutions. The
last volution is partially evolute. Proloculus isapproximately 0.020 mm in inside diameter. Wallin the earlier volutions appears three layered
because of an upper tectorium produced by secondary deposits on the chamber floors. Chomata
are weak and sometimes absent. Tunnel is very
low and narrow.
Remarks:-Eostaffella postmosquensis was
originally described by Kireeva in RauzerChernousova et al. (1951) from the Vereisky andKashirsky horizons (Lower Moscovian) of theRussian Platform and later this species was
identified from the Upper Serpukhovian (Zapaltubinsky horizon) of the Donetz Basin. The
Kireeva's types generally have much smaller shellat corresponding volutions. However, so far as
the general shell shape (rounded periphery, deep+- Figure 5. A-C, E?, Eostaffella subulba, sp. nov. A, tangential section of thc holotype, UMUT PF
18028. B, tangential section of a paratype, UMUT PF 18029. C, oblique section of a paratypc, UMUT PF 18030.
E, incomplete diagonal section of questionably assignment to this species, UMUT PF 18031. D, F, G, H?, Eosta[fella mosquensis Vissarionova. D, axial section, UMUT PF 18033. F, axial section, UMUT PF 18034. G, axial
section, UMUT PF 18032. H, sagittal section of questionably assignment to this species, UMUT PF 18070. I,
Eostaffella tenebrosa Vissarionova, sagittal (slightly diagonal) section, UMUT PF 18039. All specimens XI00.

ShujiNIKO

126

umbilication on both sides) and weaker chomata
are concerned examined specimens well agreewith the type specimens.
This species resembles Eostaffella cooperi(Zeller) from the Kinkaid Limestone of Illinois,
but it differs in having smaller proloculus andwell-developed umbilical depressions.
The internal morphology of this species
exemplifies very close relationship to Eostaffella
and Zellerina, but I have assigned the materials
to Eostaffella because they have well-differentiated spirotheca.
Eostaffella subulba Niko, sp. nov.
Figures 5-A-C, E?

Material studied:-Holotype, UMUT PF 18028(sample NS 61, Figure 5-A); paratypes, UMUT
PF 18029 (sample NSR 6, Figure 5-B), 18030(sample NS 61, Figure 5-C), and a specimen ofquestionable assignment to this species 18031(sample NS 10, Figure 5-E) were examined. All
specimens were obtained from loco A.
Diagnosis.-Large Eostaffella with discoidal toelliptical test, rounded periphery and rapid expansion of the last volution. Septa short andstraight. Chomata well-developed.
Description : -Test is large for the genus, discoidal to elliptical and umbilicate on both sides.
Periphery is rounded in axial section and lateralslopes are broadly convex. The holotype (Figure5-A) contains at leat 5 volutions that is 0.38 mm
in length and 0.71 mm in width. Form ratios of
the outer 4 volutions of the holotype are approximately 0.53, 0.56, 0.54, and 0.54, respectively. A paratype (Figure 5-B) contains at least
4 volutions is 0.33 mm in length and 0.65 mm inwidth, giving form ratio 0.51. The largest specimen (Figure 5-C) attains to 0.90 mm in width.
Septa are short and straight except for the last
three ones, which are relatively long and faintly
curved. Septal counts of the last two volutions ofa paratype (Figure 5-C) are 14 and 13. Wallappears three layered because of an upper tectorium produced by the secondary deposits on thechamber floors; in the last volution the wallconsists of tectum and lower tectorium. Thick-ness of spirotheca of the last volution of theholotype is approximately 0.015 mm. Asymmetrical chomata are well-developed in the outer
volutions. Tunnel is .low and narrow, but in thelast volution it becomes wider rapidly than in the
penultimate volution. Aperture is very low, basal
and slit like.
Remarks:-Eostaffella subulba somewhat resembles E. hohsienica Chang from the Hochow
Limestone of Anhui Province, China, but thisnew species differs from the latter in having
loosely coiled shell, weaker chomata and fewer
septa at corresponding volutions. E. endothyroidea described by Chang (1962) from the
Hochow Limestone and E. mosquensis havesmaller shell than E. subulba.
Unfortunately, it is impossible to determine
the proloculus size and characters of the juvenarium volutions of this form owing to ill-orientation.
Eostaffella tenebrosa Vissarionova
Figures 4-F, G, 5-1
Eostaffella ikensis tenebrosa Vissarionova, 1948, p.
220-221, pI. 13, figs. 11-13; Ganelina, 1951, p.
182-183, pI. 1, figs. 2-3; Grozdilova and Lebedeva,
1954, p. 124, pI. 13, fig. 18; Brazhnikova et aZ.,
1956, pI. 16, fig. 6; Durkina, 1959, p. 199-200, pI.
20, figs. 21-22; Rozovskaia, 1963, p. 98, pI. 18,
figs. 1-2; Manukalova-Greboniuk, I1'ina and Serezhnikova, 1969, p. 32-33, pI. 9, figs. 13-14; Malakhova, 1973, pI. 6, fig. 5; Ivanova, 1973a, pl. 17, fig.
2, pI. 24, figs. 1-3, pI. 30, fig. 14; Sosnina andNikitina, 1976, pI. 9, fig. 29.
Eostaffella cf. ikensis tenebrosa Vissarionova: Chang,
1962, p. 437-438, pI. 1, figs. 14-15.
Eostaffella tenebrosa Vissarionova: Bogush and luferev,
1962, p. 174, pI. 11, fig. 29.

Material studied:-Specimens including two
axial sections (UMUT PF 18038, sample T2 5,
Figure 4-G; 18040, sample NS 40, Figure 4-F),
three oblique sections, and one sagittal section(UMUT PF 18039, sample T2 5, Figure 5-1) werestudied. All sepcimens were obtained from loco
A.
Description: -Test is lenticular to rhomboidal
with arched poles. Outer periphery is pointed inaxial section, and lateral slopes are nearly straight834. Eostaffella from the Ichinotani Formation
to slightly concave. Mature specimens contain
5 1/2 to 6 volutions that are 0.31 to 0.36 mm inlength, and 0.57 to 0.77 mm in width. Formratio ranges from 0.52 to 0.55. In a typical specimen (Figure 4-F) radius vectors of the second tosix volutions are 0.04,0.08,0.15,0.25, and 0.37mm, respectively. Proloculus is approximately
0.021 to 0.025 mm in inside diameter. The initial
1 to 1 1/2 volutions are plectogyrally coiled, but
the rest are planispiral. Septa are short, straightand slightly inclined forward. Septal counts ofthe third to fifth volutions of a specimen (Figure5-1) are 10, 14, and 16, respectively. Outer periphery of septal sutures is smooth. Wall is calcareous, microgranular and 0.008 to 0.009 mm
thick in the penultimate volution; it is differentiated into a thin tectum and tectoria. Tunnel
is low and narrow in the inner five volutions, butrather broad in the last volution. Asymmetricalchomata are well-developed through shell except
for the juvenarium. Tunnel sides of chomata
are steep, but poleward slopes are very gentle
and extending to poles.
Remarks:-Eostaffella tenebrosa was originally described by Vissarionova as a variety of E.
ikensis, and was reported from the Michailovsky(Late Visean) to Steshevsky horizons (Middle
Serpukhovian) of the Donetz Basin, Russian
Platform, Urals, and Sikhote Alin. The Vissarionova's original types have a more pointed periphery and tightly coiled than examined specimens.
However, it is identical in the general shell shape,and short and straight septa.
Eostaffella tenebrosa has about the same
dimensions with E. ikensis and E. enormis. But
E. ikensis has a more rounded periphery in theouter volutions, and E. enormis has a larger shelland well-developed chomata.

Eostaffella sp.
Figure 4-K

Material studied:-Description is based on
only one specimen (UMUT PF 18041, sample
NSR 1) from loco A.
Descriptive remarks: - This differs from otherspecimens of the genus in its rapid expansion of127

the last volution, hence this may represent a new
species. Test is moderately large for the genus,
involute with slightly umbilicate on both sides.
Periphery is pointed in the outer three volutions
and more or less rounded in the last volution.
The specimen contains 5 volutions that is 0.33
mm in length and 0.66 mm in width, giving form
ratio 0.50. The initial volution is skewed at angleof about 48 degrees to the remaining essentiallyplanispiral volutions. The last volution inflates
more rapidly than the inner volutions. Proloculus
is approximately 0.025 mm in inside diameter.
Wall consists of a tectum, and lower and upper
tectoria. Low asymmetrical chomta occur in theouter volutions. Tunnel is relatively high andwide in the last volution.
Acknowledgments
I thank Dr. Y. Okimura of Hiroshima University for his valuable suggestions and criticallyreviewing the manuscript. This paper is benefited
substantially from the constructive criticism andadvice of Dr. T. Hamada of The University ofTokyo. Dr. H. Igo of The University of Tsukuba
helped me by supplying type specimen for thisstudy. I would like to thank Dr. K. Sada of Hiroshima University and Dr. K. Ishii of Kobe University for their providing the informaitons.
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Annual Meeting at Yamagata, p. 236 (in Japanese).

834. Eostaffella from the Ichinotani Formation
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and Permian Taishaku Limestone in West Japan,
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- - (1969): Microfossils of the lowest part of the
Taishaku Limestone (Ibid., no. 4). Ibid., no. 75, p.
119-129, pis. 12-13.

129--(1975): Early Pennsylvanian fusulinacea from theOmi Limestone in Japan. Mem Fac. Integr. Arts
and Sci, Hiroshima Univ., vol. 1, p. 31-39, pI. 1.
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54, no. 1, p. 65-70, pI. 1.
--and Danner, W. R. (1973): Late Lower Carboniferous Eostaffella and Hexaphyllia from central
Oregon, U.S.A. Trans. Proc. Palaeont. Soc. Japan,
N. S., no. 91, p. 151-160, pis. 23-24.
- - and - - (1974): Early and Middle Pennsylvanian
fusulinids from southern British Columbia, Canada
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p. 249-265, pis. 35-37.
- - , Nomura, K. and Oho, Y. (1984): Primitive fusulinacea from Dangyokei of Taishaku (Studies of thestratigraphy and the microfossil faunas of the
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pI. 75.
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Japan. Japan Jour. Geol. Geogr., vol. 31, p. 9-11,
pI. 2.
Sosnina, M. I. and Nikitina, A. P. (1976): Kamennougol'nye foraminifery Primorya. Vses. NanchnoIssled. Geol.Inst. (VSEGEl) Trudy, N. S., vol. 247,
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Geol. SeI., no. 19, p. 216-226, pis. 13-14 (inRussian).
Watanabe, K. (1973): Profusulinella assemblage in theOmi Limestone, Niigata Prefecture, central Japan(Studies of Carboniferous Fusuliancean of Omi,
part 1). Trans. Proc. Palaeont. Soc. Japan, N. S.,
no. 92, p. 371-394, pis. 51-53.
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Sinica, no. 6, p. 72-87, 8 pis. (in Chinese).

ShujiNIKO

130

Ichinotani -/~. Fukuji :ffiitl!!. Mizuboradani 7j(11".1~. Mizuyagadani *~..,.~. Hochow 5!'llj·I'i.
Anhui *~.

:ffiitl!!:l1!!~- / ~~iI' ~ 0)15 .l!R*ciliIWl Eostaf fella CW-~{jEt:J 7 ?:' !J j-JD : i!lt.$.JJi!, tr:!~UIL1:~t-.t:ffii
tl!!tI!!~O)- / ~~r$iI' ~ It~&tJ:1HL~11::15~>a:-~I±li' ~ • .!fIB]. 3 ~~ CEostaffella

excavata. E. igoi. E. subulba) >a:-~t; 8 ~0)W-~{jEt:J7?:'!J j-J{ CEostaffella) ">a:-~~ff:~Et:J5t*O)t.:l5bO)£~Et:JT·-.? C l- -c~tn.. t.:. :::. 0)7;(!J j-11::15~lt. igo (1956) ~.::. J: ~ Eostaffella~'7 /iliIWl-C-;!;~ C
kanmerai zone ~'::'~l5b ~:h. :to)~fI;;lt ~ -It 7 /J1i\:~Wlil'~~}!.-7·- ~~~~:h~.

*-~~.~

Trans. Proc. Palaeont. Soc. Japan, N. S., No. 147, pp. 131-145,5 Figs., October 30,1987

835. ON THE SILURIAN TRILOBITE FAUNULE OF HITOEGANE
NEAR FUKUJI IN THE HIDA PLATEAU, JAPAN*
TEIICHI KOBAY Asm
The Japan Academj, Ueno Park, Tokyo

and
TAKASm HAMADA
Department of Earth Science and Astronomy, College of Arts and Science, University of Tokyo

Abstract. A new collection from Hitoegane adjacently north of Fukuji, Gifu Prefecture
contains more than nine species of trilobites in the Scutelluidae, Illaenidae (?), Proetidae,
Cheiruridae and Encrinuridae, including four new species, namely Kbsovopeltis hidensis,
Proetus (Coniproetus) tenuiceps, P. (Coniproetus?) subconicus and Cheirurus hitoeganensis.
This faunule is late or middle Ludlovian in age and shows affinities to the East Australian faunathrough the Yokokura-yama, Shikoku and the Bohemian fauna through the trilobites of theMongolian geosyncline. Encrinurus cf. similis found at Hakubado, Fukui Prefecture is about
the same age.

cf. similis. Hitoegane and Hakubado are two
Silurian fossil localities in the Hida plateau which
are located respectively in the eastern and western parts of the plateau with a distance of about
90 km between them. The geology of these localities are so highly complicated that the relation of these Silurian rocks to the older andyounger Paleozoic formations is not yet clarified.
A new trilobite collection of Hitoegane contained mostly in limestones, but Encrinurus cf.
kitakamiensis whose mother rock is green tuffaceous shale casts a question on the age of Scutellum (?) sp. indet. The authors reported it as a
Silurian trilobite (1965), but later a Devonian
one (I 977). Now it becomes more probably a
Silurina trilobite in looking the similarity of its
mother rock with that of Encrinurus cf. kitakamiensis. As the result of restudy on this specimen it is called here Decoroscutellum (?) sp.
indet.
The Hitoegane trilobites in the new collection are the following forms in the Scutel-

The Favosites fauna of Ichinotani at Fukuji,
Kamitakara Village, Yoshiki County, Gifu Prefecture which has once been considered Silurian(Kamei, 1949) was later transferred to the
Devonian (Kobayashi and Igo, 1956) and still
later the Fukuji Formation was determined to bewithin the range from Gedinnian to Eifelian(Igo et al., 1975; Kobayashi and Hamada, 1977;
Igo and Adachi, 1981). Prior to this a few pygidia were found in limestone boulders at Hitoegane hill about 1500 m to the north-northeastof Fukuji. They were found to be a new speciesof Encrinurus as denominated Encrinurus
fimbriatus by the authors (1974). Thus the
Silurian limestone was proven to exist at Hitoegane in the Fukuji area.
Ohno, Okazaki and Hirano (1977) on theother hand discovered Encrinurus at Hakubado,
Izumi Village, Ohno County, Fukui Prefecture.
The authors are of opinion that it is Encrinurus*Received November 7, 1986; Studies on Japanese
Trirobites and Associated Fossils-IL.

131

132

Teiichi KOBA YASHI and Takashi HAMADA

luidae, Illaenidae (?), Proetidae, Cheiruridae andEncrinuridae.
Kosovopeltis hidensis, sp. nov.
Kosovopeltis hidensis f. striatus, fonna. nov.
Illaenid (?) gen. et. sp. indet.
Proetus (Coniproetus) tenuiceps, sp. nov.
Proetus (Coniproetus?) subconicus, sp. nov.
Cheirurus hitoeganensis, sp. nov.
Cheirurid, gen. et sp. indet. (Hypostoma)Sphaerexochus sp. indet.
Encrinurus fimbriatus Kobayashi and Hamada
Encrinurus cf. kitakamiensis Sugiyama
All of these trilobites are contained in limestone except for Encrinurus cf. kitakamiensis.
In the Kitakami mountains, North Japan E. kitakamiensis horizon lies immediately above themiddle Ludlovian limestone containing Schedohalysites kitakamiensi$ (Hamada, 1961). Therefore the superadjacent trilobite horizon must belate Ludlovian, if not Pridolian in age. Decoroscutellum as a genus ranges from Wenlockian
to Lower Devonian, although it thrived in the
Ludlovian. The generic reference of the pygidiumin question is provisional. Therefore the exact
age of Decoroscutellum (?) sp. indet. in schalstein is indeterminable.
Among the trilobites in the limestone ofHitoegane there is none spcifically identifiablewith any species from Yokokura-yama or otherlocality in Japan. Kosovopeltis, Proetus, Sphaerexochus and Encrinurus are common genera
between the Hitoegane and Yokokura-yama
faunas, but Proetus (Coniproetus) is unknown
from Yokokura-yama.Kosovopeltis Snajdr, 1958
is a Silurian scutelluid genus flourished in the
Ludlovian (Kopanina to Lochkov beds) in
Bohemia (Emsian) and a species is known fromthe Urals (Snajdr, 1960). Among the Japanese
trilobites K. hidensis is allied to K. angusticostatus of the Yokokura-yama fauna. Proetus(Coniproetus) as a genus is distributed in Europe
and North Africa in the range from Silurian(lower Budnanian) to Devonian (Emsian)(Alberti, 1969). Cheirurus hitoeganensis is closely allied to Cheirurus insignis Beyrich from theupper Wenlockian (Liten high) in Bohemia(Horny and Bastl, 1970). Encrinurus fimbriatus

was primarily founded on some pygidia from
Hitoegane. The new collection contains not only
pygidia but also cranidia. This species is allied
to not only E. subtrigonalis and E. yokokurensis
from Mt. Yokokura in Japan but also E. sinicus
Kuo from near Kirin, Northeast China (Kuo,
1962). Judging from these facts the Hitoegane
limestone faunule is Ludlovian and probably
middle or late Ludlovian in age.
Thus there are three trilobite horizons in the
Hitoegane area. The tuffaceous shale containing
Encrinurus cf. kitakamiensis is probably upper
Ludlovian. Judging from the lithological similarity the Decoroscutellum (?) bearing schalstein
may be about the same age. The trilobite faunulein the limestone of Hitoegane is judged to belower-middle Ludolovian. The Hitoegane trilobites as a whole suggest the faunal connection to
the fauna of eastern Australia through the Yokokura-yama fauna on one side and on the otherside to the Central European fauna through theUrals. This biogeographic suggestion is in supportof the trilobite pygidia from Hakubado, as theylook very similar to Encrinurus similis from
Gomi quarry on Mt. Yokokura.
Description of trilobites ofthe Hitoegane Faunule
Beside some known species and indetenninable fonns four new dpecies are here included asfollows:
Kosovopeltis hidensis, sp. nov.
Kosovopeltis hidensis fonna striatus, fonnanov.
Proetus (Coniproetus) tenuiceps, sp. nov.
Proetus (Coniproetus?) subconicus, sp. nov.
Cheirurus hitoeganensis, sp. nov.
The hypostoma is known of Encrinurus
fimbriatus. On this occasion Encrinurus cf.
similis from Hakubado is also described. Somenotes are supplemented on the Genus Proetus,
Subgenus Proetus (Coniproetus) and Genus

Encrinurus.

835. Silurian Trilobites of Hida
Family Scutelluidae R. and E. Richter, 1955
Genus Kosovopeltis Snajdr, 1945

Kosovopeltis hidensis Kobayashi and Hamada,sp. nov.
Figures I-Ia-c, 2, 3-7

Description:-Cranidium broad and gently inflated. Glabella expanded in anterior more than
twice its breadth in posterior, somewhat contracted at posterior lateral furrows and slightly
depressed behind frontal rim; anterior andmiddle lateral furrows transversal, disconnectedfrom lateral margin and the latter half as wide as
the former; posterior lateral furrow shown by
roundly sub quadrate depression incised fromlateral margin; median smooth zone as wide as
posterior lateral furrow; middle lateral lobe narrow (sag.); anterior lateral lobe a little wider
than two others; occipital furrow transversal;
neck ring narrowing laterally; its posterior
margin arcuate; axial furrow deep. Fixed cheekdepressed, moderate i~ breadth; eyes large,
opposed at posterior lateral furrows and expanded postero-Iaterally; eye-ridge present; alae
small, semicircular, opposed at galbellar constriction. Frontal rim separated from glabella by narrow furrow, broadly arcuate, distinctly elevatedand extending beyond eyes; frontal marginal
furrow becoming deeper on lateral sides; anteriorfacial sutures widely divergent from eyes, but
bent back at marginal rim. Doublure vertical.
Very fine transversal striae densely distributed
nearly whole cranidium.
Observation:-An associated pygidium is nearly flat except for the axial lobe whose outline
is triangular and a little elevated above the levelof the pleural field. This lobe is simply flattopped, non-trilobate and decorated with finetransversal striae. The axial furrow is nearlystraight and shallow but fairly wide. The postaxial rib is somewhat broadened in posterior.
Seven pleural ribs on its lateral side look moreor less convex antero-Iaterally. All of these ribs
are crossed by sharp ridges on the top. The
pleural furrows are narrow and profound.
Comparison: - Though the pygidium is im-133

perfect, its outline may be semi-elliptical. It
agrees with the above cranidium in the low convexity and the mode of striation on the axial
lobe. Its obsolete trilobation is very distinctive
among scutelluids. It is somewhat similar to
Kosovopeltis angusticostatus from Mt. Yokokura, but the ribs are narrower than furrows andornamented with fine crenulation.
In Kosovopeltis nebula Campbell, 1967 from
Oklahoma the trilobation of the axial lobe is
obsolete in anterior, but a pair of longitudinalfurrows are distinct in posteiror.
Finally, Bronteus partschi Barrande by Weber,1951 in fig. 13, pI. 2 is a similar pygidium inobsolete trilobation of the axial lobe and infine crenulation of the ribs and the pleuralfurrows stronger in the Kazakhstan form. The
pygidium is probably longer and the axial lobe
relatively smaller in that species.
Occurrence:-Limestone, Hitoegane. An imperfect thoracic segment having lirae like thecephalon is contained in the collection.

Kosovopteris hidensis forma striatum
Kobayashi and Hamada, forma nov.
Figure 1-3

This cranidium agrees best with Kosovopeltis
hidensis in most aspects, but the test is morestrongly striated and the striation becomes very
irregular in posterior. The frontal marginal
furrow is rudimentary, the anterior outline moreconvex forward and the middle lateral furrow
indicated by a very small but deep pit. The fixedcheek is much more convex in this form, if compared with the preceding.
Occurrence:-Limestone, Hitoegane.
Genus Decoroscutellum Snajdr, 1958

Decoroscutellum (?) sp. indet.
1965. Scutellum (?) sp. indet. Kobayashi and Hamada,Trans. Proc. Pal. Soc. Japan, N. S., no. 58, p. 78,
pI. 7, figs. 4a-b, text-fig. 2
1977. Scutellum (?) sp. indet. Kobayashi and Hamada,
Palaeont. Soc. Japan, Spec. Pap., no. 20, p. 80,
pI. 1, figs. 4a-b.

134

Teiichi KOBA YA SHf and Takashi HAMADA

835. Silurian Trilobites of Hida
An imperfect pygidium of a scutelluid whoseanterior margin is broad and straight. Its triangular axial lobe is trilobate and the median lobe
swelling upward in posterior, possibly forming a
median tubercle. The post-axial median rib ismuch broader than lateral ribs in anterior, somewhat narrowing back and then broadened backward. Whether it is bifurcate or not is indeterminable. Among seven pairs of lateral ribs thesecond and third ones are distinctly bent withconvexity on the antero-lateral side. The fourthand sixth ribs are somewhat arcuate toward the
opposite side in the distal half. Thus the lateralribs are more or less sigmoidal. All ribs are flatand separated from one another by much narrower furrows. The lateral posterior margins are
unknown, but it is known that the doublure extends about an outer half of the pleural field.
The pygidium is presumably subpentagonalin outline. In the distinct trilobation of the axial
lobe, the posterior tubercle (?) of its median lobe
and the more or less sigmoidal pleural ribs, thispygidium agrees with Decoroscutellum (Decoroscutellum) haidingeri (Barrande) from the
Kopanina beds in figs. 1-3, pI. 6 in Snajdr(1960). In this pygidium, however, the pleuralfurrows are considerably narrower than in
Barrande's species. The furrows are, however,very narrow in D. (Decoroscutellum) lepidum
lepidum BoU(~ek) from the Lochkov beds in fig.
4, pI. 7, Snajdr (1960). The median rib is wellbifurcate in Bou~ek's species, whereas thebifurcation occurs only in the terminal part inBarrande's species. Thus it is probable that thispygidium belongs to an unknown species ofDecoroscutellum.

135

Occurrence:- The specimen is contained inschalstein of Hitoegane. It was once considereda Devonian Scutellum, but its age would be late
Silurian, judging from the otter Hitoegane trilobites.
Family Proetidae Salter, 1864
Subfamily Proetinae Salter, 1864
Genus Proetus Steininger, 1831
As stated already in 1977 (pp. 132,180), theclassification of the Proetidae and Proetacea is asubject of most discussion. Many questions arealso attached to the subgeneric division of genus
Proetus. Proetus (Coniproetus) is, however, acceptable as a good subgenus, although a question
still remains as to the synonymy of Bohemiproetus with Coniproetus.
Subgenus Coniproetus Alberti, 1966

Diagnosis:-Glabella coniform; lateral glabellar
furrows not incised; short (sag.) preglabellar fieldcommonly developed; lateral occipital lobes welldefined; eye platform typically absent; long genal
spines in most species; pygidial border welldeveloped; band of parallel terrace lines aroundpygidial margin; exoskeleton smooth, or with
granular sculpture.
Type-species:-Proetus glandiferus Novak,
1890
Remarks: -This subgenus was primarilyfounded on Proetus condensus Pfibyl, 1965. According to Owens (1973), however, its typespecies must be Proetus gladiferus Novak, 1890,
because both of them belong to an identical~ Figures l-la-c, 2.
Kosovopeltis hidensis Kobayashi and Hamada, sp. nov. A dorsal (a), frontal (b) andright lateral (c) views of the holotype cranidum. x4.2, PA 18095.2. A dorsal view of an incomplete pygidum.
x1.6, PA 18096.
3. Kosovopeltis hidensis forma striatum Kobayashi and Hamada, forma nov. A dorsal view of an incomplete cranidium. xL 7, PA 18097.
4a-d. Proetus (Coniproetus) tenuiceps Kobayashi and Hamada, sp. nov. A dorsal (a), left lateral (b),frontal (c) and posterior (d) views of the holotype cranidium. x5.3, PA 18098. (Vide Figures 2-la, b also).
Sa-d. Proetus (Coniproetus?) subconicus Kobayashi and Hamada, sp. nov. Dorsal (a, b), left lateral (c)and frontal (d) views of an incomplete cranidium. a: x8.2, b, c, d: x7.1, PA 18099.
6a, b. Illaenid (?) gen. et sp. indet. A dorsal (a) and posterior (b) views of an ill-preserved pygidium showing the slanting margin which is covered by striation on the undersurface of doublure. x3.7, PA 18113.

136

Teiichi KOBA YASHI and Takashi HAMADA

species. Furthermore Proetus (Bohemiproetus)
Pillet, 1969 is synonymous with Proetus (Coniproetus) because Proetus bohemicus Hawle andCorda, the type-species of the former, is not so
different from P. glandiferus as they can be separated subgenerically. Thus the above quoted diagnosis was given by Owens.
Distribution:-According to Alberti (1969)
this subgenus is distributed from Silurian (lower
Budnanian) to Devonian (Emsian) in EuropeAfrica. As noted by the authors (1974, 1977), its
trans-Eurasiatic distribution through the Mongolian geosyncline is shown by the occurrences ofProetus bohemicus in the Lower Devonian ofTurkestan (Weber, 1932) as well as Proetus(Coniproetus) fukujiensis from the Lower-Middle
Devonian of Fukuji, Japan. Preoetus (Coniproetus) subconicus here described proves further that such an extensive distribution of thesubgenus was started already in the late Silurianage.
Proetus (Coniproetus) tenuiceps
Kobayashi and Hamada, sp. nov.
Figures 1-4a-d, 3-1a-b

Description:-Glabella longiconic, well convex, almost straight laterally and abruptly rounded in front; lateral furrows obsolete; occipital
furrow profound and transversal; occipital ringvery short sagittaly, well arcuate on posteriorside, depressed below glabella, provided with a
median tubercle and a pair of small lateral lobes
indicated by a pair of notches; palpebral lobe
fairly long and located far posteiorly; fixedcheek narrow; frontal border convex, well developed, separated from glabella by marginal furrow; preglabellar field almost nullified between

frontal and dorsal furrows; facial sutures slightly divergent from eyes as far as parallels throughlateral eye-limits and then curved inward; testsmooth.
Observation: -The median tubercle is seen on
the exfoliate part of the test. The occipital lobes
are indicated by short oblique notches from theoccipital furrow into the occipital ring. The
dorsal furrow is separated from the narrow frontal marginal furrow by a space i.e. the preglabellar field, narrower than these furrows. Some parallel striae are seen on the frontal border.
Comparison : -This species can be distinguished from not only Proetus (Coniproetus)
glandiferus Novak, but also the Devonian species
from North Africa (Alberti, 1969) and theArmorican massif, France (Pillet, 1972) in thelongiconic glabella. In the general aspect of the
cranidium it resembles Proetus (Longiproetus)
pseudotenuis (Pillet), an Armorican species closely, but the median tubercles absent on the neckring and the marginal border is flat or concave
in Proetus (Longiproetus). Ludlovian Proetus
obconicus Lindstrom which Owens (1973)
referred to Proetus (Lacunoproetus) Yolkin,1966 and also Wenlockian P. (L.) confusus
Owens, 1973 have the cranidium and glabellasimilar to this species in outline and convexity,
but the lateral furrows are completely effaced on
the glabella and the eyes larger and located moreposteriorly in this species. Proetus (Bohemicus)
magnicervicu/us from Mt. Yokokura agrees withthis species nicely, but the glabellar outline isquite different. Judging the essential characteristics of the cranidium this form is considered
best to place in Proetus (Coniproetus).
Occurrence:-Limestone, Hitoegane.

~ Figures 2-1a, b.
Sphaerexochus sp. indet. A dorsal (a) and right lateral (b) views of an ill-preserved
cranidium showing a distinct basal lobe and a neck ring. xl.8, PA 18103.
2a, b. Cheirurid, gen. et sp. indet. (hypostome). A ventral (a) and left lateral (b) views of an incomplete
hypostoma showing the general outline. xl.9, PA 18102.
.
3a-c. Cheirurus hitoeganensis Kobayashi and Hamada, sp. nov. A dorsal (a), left lateral (b) and posterior(c) views of an incomplete pygidum. x3.4, PA 181Ol.
4a-c,5a-d. Encrinurus fimbriatus Kobayashi and Hamada, 1974. A dorsal (a), frontal (b) and left lateral(c) views of a cranidium showing hte general outline with rounded genal angle. xl.8, PA 18104. 5a-d. Anotherspecimen of cranidum. xl.7, PA 18105.

835. Silurian Trilobites of Hida

1a

1b

137

138

Teiich; KOBA YASHI and Takashi HAMADA
Proetus (Coniproetus?) subconicus
Kobayashi and Hamada, sp. nov.

Cheirurus hitoeganensis Kobayashi and Hamada,sp. nov.

Figures 1-5a-d

Figures 2-3a-c

Description: -Cranidium nearly as long as
broad and moderately inflated. Glabella conical,
rounded in front, gently rising toward its center;occipital ring well developed and provided witha pair of lateral lobes; occipital and dorsal furrows profound. Fixed cheek narrow; palpebral
lobe large, semicircular, provided with narroweye-band and opposed in posterior of glabella.
Frontal border well convex, thick and separated
from glabella by narrow marginal furrow; anterior fIxed cheek expanded laterally, as long as
frontal border and divided into two parts by aweak crest. Facial sutures running forward diagonally from two sides of eyes. Test smooth.
Observation and Comparison:-An imperfectcheek having a low crest parallel to the cheekmargin and distinct depression along its innerside belongs probably to this species. The cephaIon of this species resembles Proetus (Coniproetus) tenuiceps in the conical glabella andabsence of the preglabellar fIeld, although theglabellar outline tapers more slowly and broadly
rounded in front in that species. The low creston the cheek is the most important distinction
from Proetlls (Coniproetus).
Occurrence:-Limestone; Hitoegane.

Description:-Pygidium exclusive of spines
sub triangular; axial lobe composed of three rings
and a terminal piece; pleural part of anterior twosegments divided into two short ridges by diagonal interpleural furrow for a short distance tilllateral spine issues; third segment also bisected
but into narrower ridges; three pairs of equallylong spines extending laterally and posteriorly
with convexity on antero-Iateral side; terminal
pieces ill-developed; posterior margin between
third spines simply convex backward. Test apparently smooth.
Comparison: -This pygidium best agrees withCheirurus insignis Beyrich, but the terminal pieceof the axial lobe is ill-defIned and the posterior
margin not produced as in C. insignis. Dideropanon has three pairs of lateral spines on thepygidium, but only the anterior two pairs areelongated. In Cheirurus on the other hand has
three pairs of spines all long like in this species.
The axial lobe consists of three rings and a terminal piece which the last is protruded behindin the typical species of Cheirurus. The pygidiumof Contracheirurus errator Lane, 1984 is similar
to this pygidium in possession of three pairs oflong lateral spines and the entire post-axial
margin. The terminal piece of the axial lobe is,however, clearly defined and the lateral spines
become shorter posteriorly in that species.

Family Cheiruridae, Salter, 1864
Genus Cheirurus Beyrich, 1845

~ Figures 3-1a, b.
Proetus (Coniproetus) tenuiceps Kobayashi and Hamada, sp. nov. A dorsal (a) andlateral (b) views of an incomplete free cheek. x6.0, PA 18098.
2a-c, 3a-e, 4a-d. Encrinunls fimbriatus Kobayashi and Hamada, 1974. 2a-c. A dorsal (a), right lateral(b) and posterior (c) views of a large pygidium. xl.9, PA 18106. 3a-c. A dorsal (a), posterior (b) and rightlateral views of another pygidium. x2.1, PA 18107. 4a-d. A dorsal (a), posterior (b), right (c) and left lateralviews of another small pygidium. x2.1, PA 18108.
5. Trilobita, gen. et sp. indet. A fragmentary free cheek showing a long genal spine and the surface tuberculation. x3.6, PA 18114.
6. Encrinurns cf. kitakamiensis Sugiyama, 1941. A dorsal view of somewhat flattened pygidum preservedin shale. x3.1, PA 1811!.
7. Kosovopeltis hidensis Kobayashi and Hamada? A dorsal view of a fragmentary thoracic segment. x!.9,
PA 18115.
Sa-d. Encrinurus cf. similis Kobayashi and Hamada, 1974. A dorsal (a), left lateral (b) and posterior (c)views of an imperfect pygidum (a latex replica) obtained from a small exposure nearby the Hakubado, Fukui
Prefecture. x2.1, PA 18112.

835. Silurian Trilobites of Hida

139

140

Teiichi KOBA YASHI and Takashi HAMADA
Occu"ence:-Limestone; Hitoegane.

Occu"ence: -Limestone, Hitoegane.

Cheirurid, gen. et sp. indet., Hypostoma

Family Encrinuridae Angelin, 1854

Figures 2-2a-b

Genus Encrinurus Emmerich, 1844

A fairly large hypostoma, much longer thanbroad, well rounded and auriculate in anterior;lateral margins gradually tapering back behindsmall anterior wings and truncated by transversal posterior margin; main body long, oval andseparated from posteior part by deep, short andoblique depressions on lateral parts; lateral border moderate in breadth and depressed. Test withfine granules.
This hypostoma measures 17 mm in lengthand 8.6 mm in breadth. It is not so well preserved that its outline is traceable exactly. Its
general aspect, however, suggests its reference to
the Cheiruridae (Prantl and Ptibyl, 1947, Lane,
1971, Ramsk6ld, 1982). It looks similar to thehypostoma of Cheirurus insignis Beyrich, 1840.
Compared to the cranidium and pygidium it isconsiderably larger. Its reference to that species
is hesitated by its coarse granulation.
Occurrence:-Limestone, Hitoegane.

Encrinurus is well represented in Japan byvarious pygidia from many localities among
which ten species can be distinguished withreference to the segmentation, relative breadthof the axial lobe, presence or absence of thesmooth median band or/and median tubercles
on the lobe and so forth. Cephala are not so common, but three kinds were found in Mt. Yokokura collection. Because they are detached,
their combination is inevitably a play of presumption.
Hitoegane collection contains not only two
pygidia but also a cephalon of Encrinurus fimbriatus all in the same kind of limestone, besidea pygidium of Encrinurus aff. kitakamiensis in ashaly rock. Encrinurus cf. similis occurs at Hakubado in limestone.

Subfamily Sphaerexochinae Oepik, 1937

Encrinurus /imbriatus Kobayashi and Hamada,
1974
Figures 2-4a-c, 5a-d, 3-2a-c, 3a-c, 4a-d,
4-1a-e, 2a-e, 5.

Genus Sphaerexochus Beyrich, 1985

Figures 2-1a-b

1974. Encrinurus fimbriatus Kobayashi and Hamada,Pal. Soc. Japan, Spec. Pap., no. 18, p. 107, pI. 11,
figs. 10-11, text-fig. 7H.

An imperfect cranidium of Sphaerexochus
whose occipital and pre-occipital furrows are verybroad and fairly deep. They are confluent toeach other to isolate the basal lobe. The twoother lateral furrows are unpreserved or completely effaced in front of the pre-occipital furrow. The basal lobe of moderate size looks
roundly subquadrate. The cheeks and all otherparts are unknown. Therefore its comparison
with Sphaerexochus hiratai or any other species
cannot be made.

This species was primarily founded on pygidia
which are sub triangular, but its anterior margin
is well arcuate near lateral extremities, andstrongly convex, arching down on the lateral andposterior sides, but the adaxial pleural part isnearly flat; axial lobe narrow, long, conical, regularly tapering back, gently convex, a little elevated above the pleural lobes and abruptly bent
down near posterior end, terminating at bluntend inside the posterior margin for a short distance, and divided into numerous rings. Pleural

Sphaerexochus sp. indet.

~ Figures 4-1a-e, 2a-e.
Encrinurus fimbriatus Kobayashi and Hamada, 1974. Two casts of hypostom at ashowing the general outline and the rough musclature. 1a-e, x5.0, PA 18109, 18110. This specimen was foundin association with a pygidium of Encrinurus fimbriatus that is shown in Figures 3-4a-d, 2a-e, x5.7, PA 18108.

835. Silurian Trilobites of Hida

1e

141

142

Teiichi KOBA YASHI and Takashi HAMADA

lobes are divided into 10 to 11 ribs by profoundpleural furrows, the most anterior one of which
is very narrow.
The axial lobe is about one-fourth as wide as
the pygidium. Some 20 axial rings are countableon its main part. In adding incountable posterior
ones on the terminal bent part, they probably
attain 30 in total. The median smooth band isabsent, but some rings are depressed mesially.
Median tubercles are very sparse. The pleural ribs
are somewhat expanded at their lateral termini.
The new collection contains four pygidia.
A small one which is better preserved than theothers shows the mode of segmentation clearly.
The details of the axial rings, pleural ribs andfurrows are better shown in this than the holotype pygidium. The small specimen in Figures
24a-c is 15 mm long, 14 mm wide, and 5.3 mm
high and its axial lobe is 5 mm wide at the anterior end. The respective dimensions are 21.7 mm,
17.3 mm, 9 mm and 8.3 mm in a large pygidium.
The proportional differences between the two
pygidia chiefly depend upon the convexity. The
former pygidium is compressed laterally, whereas
the latter is depressed longitudinally so muchthat the posterior bent becomes vertical.
This species resembles Encrinurus sub trigonaZis and E. similis in the subtriangular outline
and strong convexity of the pygidium. These
Yokokura-yama pygidia, however, have muchbroader axial lobes and pleural ribs in smaller
number. They are 9 to 10 in this species but 7 to
8 in that species. The tuberculation is well developed on the pleural ribs, particularly in Encrinurus subtrigonaZis, but the ribs are non-tuberculate
in this species.
Encrinurus sinicus Kuo, 1960, from Northeast China has 25 axial rings some of which bear
median tubercles. His fig. 5, pI. 1 and fig. 7, pI. 2
show that the axial rings are interrupted by amedian smooth band. Pleural ribs are said eightin number, but the pygidium in his fig. 6, pI. 1
has 9 or possibly 10 ribs. The axial lobe is as.
narrow as one-fifth the pygidium. The lobe isevidently much narrower than in this species.
Two imperfect cephala from Hitoegane which
are roundly sub triangular in outline and strongly

convex are considered to belong probably to thisspecies. The glabella is well inflated, arching
down in anterior and densely tuberculate. Fivepairs of tubercles are aligned along the lateral
margins, middle three of which are more prominent than two others; smaller tubercles irregularly distributed in the inner part. The occipitalmargin is unpreserved. Axial furrows are welldeveloped. Cheeks are largely destroyed. The
right cheek is a little displaced from the glabella
in a cranidium in Figure 5. The eye-scar ofmoderate size is seen on its posterior part. The
genal angle is rounded; genal spine absent.
Among the three kinds of Encrinurus-cephalaso far known from Japan it is most similar to E.
yokokurensis from which, however, it differs in
the mode of tuberculation. It agrees better with
Encrinurus sinicus, from Northeast China inpossession of five pairs of tubercles on theglabella along axial furrows, middle three of
which are more developed than two others. In
this species two rows of tubercles counted fromthe posterior side are composed of four tubercles
as in E. sinicus. The tuberculation in further
anterior is complicate and their arrangement
disagrees with E. sinicus. In that species theoccipital lobe is much wider than the glabellarbase. Of E. sinicus it is said that "genal angles
incomplete apparently terminating in spines."
This cephalon resembles alos Encrinuruskongshaensis Reed, 1906, from Burma, but "thefifth (basal) pair (of tubercles) is smaller and its
members are connected together by a weak ridge
across the glabella." This aspect is quite distinctive for this Burmese species from this species,
other Japanese species and also E. sinicus.
Hypostoma of Encrinurus /imbriatus: The
hypostoma of this species is rhomboidal, a little
longer than broad and more or less protruded
laterally as well as posteriorly. The central bodyis suboval, but its posterior outline is expanded
backward in the median part. In the middle partof the body there are some five pairs of depressions on the two sides of the axial elevation
which in turn is pitted and forms a beak-likeprojection as far as the antero-median extremityof the hypostoma.

835. Silurian Trilobites of Hida

143

distinct from all others.
Occurrence:-Limestone; Hitoegane. Two granulate free cheeks with long genal spines in thecollection which may belong to this species as
there is no other granulate cranidium.
Encrinurus cf. kitakamiensis Sugiyama, 1941
Figures 3-6

Figure 5. Reconstruction of hypostoma
of Encrinurus fimbriatus. x4.

Observation: - The Hitoegane collection contains two hypostomata one of which (a) in Figure 4-1 is found with a pygidium of this species
in Figures 34a-b. It agrees with the other hypostoma (b) in essential characteristics of Encrinurus and there is no other species of thegenus in the limestone of Hitoegane. Therefore,
it is certain that the hypostoma (a) belongs to
Encrinurus fimbriatus. Its difference from theother (b) may be no more than sub specific value
and in part a matter of preservation.
The hypostoma (a) shows the general outline
and convexity better than the other except for
the anterior part which is broken. The latterhypostoma (b) reveals unusual lateral depressions
in about five pairs in the middle part, but they
are obsolete in the former.
Comparison: -It is certain that this hypostoma belongs to the same group with those of
Encrinurus and Bolizoma. Truncated by the transvers frontal margin it is pentagonal in Coronocephalus and Senticulus of the Coronocephalinae Zhang, 1983. In its general outline and theanterior projection of the axial part of the central body, particularly it resembles the hypostoma of Bolizoma variolaris (Brongniart) (Tripp
et al., 1977). In this species, however, the projection takes a narrow beak-shape and the axial
fold is provided with lateral depressions on its
two sides in the main part of the centralloby. In
these characteristics this hypostoma is quite

1941. cf. Encrinurus (Coronocephalus) kitakamiensis
Sugiyama, Proc. Imp. A cad. , v. 17, p. 108-109,
figs. 1-2.
1959. cf. Coronocephalus kitakamiensis; Hamada,Japan. J. Ceol. Ceogr., v. 30, p. 84-85, pI. 6,
figs. 19-20.
1974. cf. Encrinurus Kitakamiensis; Kobayashi and
Hamada, Pal. Soc. Japan, Spec. Pap., no. 18, p.
105-106, pI. 19, figs. 19-20, pI. 11, fig. 12,
text-fig. 7F.

This pygidium is sub trigonal in outline withsomewhat arcuate anterior margin; axial lobe
about one-fourth as wide as pygidium and divided into about 27 rings; median tubercles
present on a few anterior rings, but mediansmooth band is absent. Pleural ribs 10 to 11 in
number; axial and pleural furrows well developed; interpleural furrows present on some anterior ribs.
In E. fimbriatus median tubercles are moredeveloped, axial rings depressed in median part,
although they do not form a median longitudinalsmooth band, and interpleural furrows areabsent.
This pygidium is closely allied to Encrinuruskitakamiensis in the outlines of the pygidium andaxial lobe, numerous axial rings, number of
pleural ribs and the presence of interpleuralfurrows. They were obscure in Sugiyama's paper(1941), but later they were clearly shown withhis holotype specimen by Hamada (1959) andKobayashi, and Hamada (I 974). It has neither
median tubercles nor a median smooth band.
Interpleural furrows are on the other hand distinct in some anterior pleural ribs in that species
as in this pygidium. The axial lobe looks, however, somewhat narrower in that species.
Occurrence:-Shaly rock, Hitoegane.

Teiichi KOBA YASHI and Takashi HAMADA

144

Encrinurus cf. similis Kobayashi and Hamada,
1985
Figures 3-8a-d

1977. Encrinurus sp. Ono, Okazaki and Hirao, Chigaku-kenkyu, v. 28, nos. 4-6, p. 188-190.

The pygidium in the above cited paper is quitedistinct from all pygidia from Hitoegane in the
broader axial lobe with the distinct median band.
It is sub trigonal and moderately inflated. The
axial lobe is almost one-third as wide as pygidium
and divided into more than 20 rings, and in the
middle-posterior part they are interrupted by
the median smooth band. A few median tubercles are present. The pleural lobe is divided into
about 10 non-tuberculate ribs by deep and· wide
pleural furrows, both bent back near lateral margin.
This pygidium is most similar to Encrinurussimilis but less inflated and possesses a few more
pleural ribs. Encrinurus ishii is another similar
species which differs from it by minute tuberculation of the pleural ribs. In E. tosensis themedian band is well developed, but mediantubercles are absent.
A pygidium in Figure 3-8 which was collectedfrom the same locality has also a broad axial
lobe and median tubercles on some axial rings.
These two pygidia belong to an identical speciesof Encrinurus closely allied to Encrinurus similis
from the Yokokura limestone, but distinct fromthe two species of Hitoegane. Therefore it isprobable that the ages of the Hitoegane and
Hakubado faunas are different, although time
displacement may be not large.
Occu"ence:-Limestone, Hakubado, Fukui.

References
Alberti, G. K. B. (1969): Trilobiten des jiingeren Siluriums sowie des Unter- und Mitteldevons. 1. Abh.
Senckenberg. Naturw. Gesell., 520, 692 pp. (52pis.).
Campbell, K. S. W. (1967): Henryhouse Trilobites.
Okla. Geol. Surv. Bull., 115,46 pp., 19 pis.
Chatterton, E. D. E. and Campbell, K. S. W. (1980):
Silurina trilobites from near Canberra and somerelated forms from the Vasa basin. Palaeontogr.,

Abt. A, v. 167 (3), p. 77-119, 16 pis.
--and Perry, D. G. (1984): Silurian Cheirurid trilobites from the Mackenzie mountains (Northwestern Canada). Ibid., Abt. A, v. 184, p. 1-78, 35 pis.
Hamada, T. (1959): Gotlandian sr.elly fauna fromSouthwest Japan. (1) Coronocephalus kobayashii,a new species from the Kuraoka district, Kyushu.
Japan. Jour. Geol. Geogr., v. 30, p. 71-88.
- - (1961): The Middle Palaeozoic group of Japan andits bearing on her geological history. Jour. Coli.
Sci., Univ. Tokyo, Ser. 2, v. 13, pt. 1, p. 1- 79.
Horny, R. and Bast!, F. (1970): Type specimens of fossils in the National Museum Pragu, vol. I, Trilobita.
354 pp., 20 pis., 4 tables.
Igo, H. and Adachi, S. (1981): Study on the Paleozoic
rocks in the Fukuji district, Kamitakara village,
Yoshiki county, Gifu Prefecture. Present status
and unsolved problems. Jour. Geogr. (Tokyo),v. 90, no. 5 (845), p. 34-43 (336-345).
Kamei, T. (1949): On the Got!andian formation in
Hida. Jour. Geol. Soc. Japan, v. 55, p. 648-649.
Kobayashi, T. (1985): Division of the Silurian System
and Procedure of Subcomission of Silurian Stratigraphy at Present. Fossils, no. 39, p. 43-45.
- - and Hamada, T. (1965): An occurrence of a new
Scutellum in the Silurian of Shikoku Island. Trans.
Proc. Pal. Soc. Japan, N. 8., no. 58, p. 74-81, pI.
7.
- - and - - (1974): Silurian trilobites of Japan incomparison with Asian, Pacific and other faunas.
Palaeollt. Soc. Japan, Spec. Pap., no. 18, 155 pp.,12 pis.
- - and - - (1977): Devonian trilobites of Japan incomparison with Asia, Pacific and other faunas.
Ibid., no. 20, 202 pp., 13 pis.
--and - - (1985): On the Silurian Trilobites andCephalopods of Mt. Yokokura, Shikoku, Japan.
Proc. Japan. A cad., v. 61-B, no. 6, p. 345-347.
- - and Igo, H. (1956):·' On the occurrence of Crotalocephalus, Devonian trilobites in Hida, West Japan.
Japan. Jour. Geol. Geogr., v. 27, p. 143-155, pI.
10.
Kuo Hong-tsun (1962): Some Silurian trilobites from
Er-tao-quo Group of Jilian. Acta Pal. Sinica, v. 10,
no. 3, p. 377-381, 2 pis.
Lane, P. D. (1971): British Cheiruridae (Tribolita).
Palaeolltogr. Soc. Monogr., p. 1-95, pis. 1-16.
--(1984): Silurian trilobite from Hall Land andNyeboe Land, western North Greenland. Rapp.
GrrJnlands geol. Unders., 121, p. 53-57,4 pis.
Ohno, T., Okazaki, Y. and Hirano, K. (1977): Discovery of a Silurian trilobite at Izumi Village,
Fukui Prefecture. Chigaku Kenkyu, v. 28, nos.
4-6, p. 185-19l.
Owens, R. M. (1973): British Ordovisian and Silurian
Proetidae (Trilobita). Palaeontogr. Soc., Monogr.,
98 pp., 15 pis.

835. Silurian Trilobites of Hida
Pillet, J. (1972): Les Trilobites du Devonien inferieur
et du Devonien moyen du Sud·Est du Massif
armoricain. Soc. d'etudes sci. de l'Anjou, mem.,no. 1, 307 pp., 64 pis.
Prant!, F. and Pribyl, A. (1947): Classification of someBohemian Cheiruridae (Trilobitae). Sbor. Narod.
Mus. v. Praze, v. 3-B, no. 1, Geol. et Pal., no. 1,44
pp.,6 pis.
Pribyl, A., Vanek, J. and Pek, I. (1985): Phylogeny andtaxonomy of Family Cheiruridae (Trilobita). Acta
Univ. Palck. Olom. Fac. Rerum Natur. Geogr.·
Geol., 24, v. 83, p. 107-1918 pis.
Ramsold, L. (1983): Silurian cheirurid trilobites from
Totland. Palaeont., v. 26, pt. 1, p. 175-210, pis.
19 28.
Snajdr, M. (1960): A study of the family Scutelluidae(Trilobita). Rozpravy Ustr. list. geol. Svazek, 26,
264 pp., 36 pis.
Sugiyama, T. (1941): A new find of Encrinurus from145

Japan. Proc. Imp. A cad. , v. 17, p. 106-109.
Tripp, R. P. (1957): The Trilobite Encrinurus multiseg·
mentatus (Portlock) and allied Middle and Upper
Ordovician species. Palaeontology, v. 1, pt. 1, p.
60-72, pI. 11-12.
--(1962): The Silurian trilobite Encrinurus punctatus
Wahlenberg) and allied species. Ibid., v. 5, pt. 3,
p. 466, 477, pis. 65-68.
--(1977): The Silurian trilobite Encrinurus variolarisand allied species with notes on Frammia. /bid.,
v. 20, pt. 4, p. 847 -867, pis. 113-175.
Weber, V. N. (1932): Trilobites of the Turkestan. Mem.
Comm. Geol. N. S., 178, 157 pp., 4 pis.
--(1951): Upper Silurian Trilobites of USSR. Trudi
VSEGEI, History of Geology, 71 pp., 6 pis.
Zhang-Lu-jin (1983): On the Subfamily Coronocephalinae (Trilobita). Palaeontologia Cathaysana, no. 1,
p. 195-258.

~!g/!j@jLl¥-l1)nljj1!!.j[[m-:ll[ 'T i'.!iP1I1);E;Wl*c-=o:~;g~ : ~.$.J!f!:a.j~Ui~J::.~Hmj:1!!.it!!:nI1)-:ll[ 'T i'.!iP111) -=o:~;gi:f:t~;: Scutelluidae, Illaenidae, Proetidae, Cheiruridae, Encrinuridae ~;:Ji.i'i,-t ~ 8 ~t).J::.I1)~
Ji.i'i,ilt~;l: h -c ~,-c, .f: 11) t.c iI>~;: Kosovopeltis hidensis, Proetus (Coniproetus) tenuiceps, P.
(Coniproetus ?) subconicus, Cheirurus hitoeganensis 11) 4 ~ ~ ilt ~ ;l: h -C ~, -C, Encrinurus
fimbriatus hypostomata ~ ~ ~ ;:11) 7 >I" - T -Ii Ludlovian -c.f:I1):.fiEJ(;fii:f:t 11) ~ 11) li.f: 11) i:f:tf&
JtIl-c;·~~o ;l: t=., ~EJ(f!;tJl:;fiP111) Encrinurus d. kitakamiensis li[lfJf&JtIlijl(li Pridolian -C;', :!!l!~~EJ(;fiP111) Decoroscutellum (?) sp. indet. ~2.cj[[~,~f\;;11) ~ 11)-C;'~0? .f: L -C-:ll[ 'T i'.!i-=o:~;g~tt~~cL-C-:n-ctt~*w-=o:~;g~~a~-c*ffl • • ~l1)c,.:n-ctt~~it!!~.~a~-C;it'" ~ 711) ~ 11) C l1)"?t.cil t IJ iltWtIrb I?h~o mttJ!f!:*!l!fli~fD:iJH111) :fLliJi~i'IJl~t* B .~il"JP111)
Encrinurus d. similis ~ ;:hchU:f[lfJ~f\;;I1)~I1)-C~~o'J':f*J!i:-' iM8~±00Trans. Proc. Palaeont. Soc. Japan, N. S., No. 147, pp.146-164, 8 Figs., October 30, 1987

836. SOME INOCERAMIDS (BIVALVIA) FROM THE
CENOMANIAN (CRETACEOUS) OF JAPAN - II
THREE SPECIES FROM HOKKAIDO, WELL KNOWN ABROAD
BUT HITHERTO UNDESCRIBED IN JAPANTATSURO MATSUMOTO
c/o Department of Geology, Kyushu University 33, Fukuoka 812

AKITOASAI
Division of Geology, Department of Mineral Resources, Schoolof Science & Engineering, Waseda University, Tokyo 160
andHIROMICHI HIRANO
Institute of Earth Science, School of Education, Waseda University, Tokyo 160

Abstract. In our recent acquisitions from the Obira and northerly adjoining Kotanbetsu
areas and also from the Oyubari area of Hokkaido there are following three species, which are
well known abroad but hitherto undescribed in Japan: (1) Inoceramus tenuis Mantell; This isfairly common in the lower and middle parts of the Cenomanian in the Obira and adjacentareas. Our forms are mostly smaller than but otherwise similar to the holotype from England.
(2) Inoceramus gradilis Pergament; A fine example, with both valves preserved, was obtained
from the Middle Cenomanian bed with Calycoceras sp. of newboldi group in the Kotanbetsu
area. Ten other specimens came from Member Mh (upper part of the Cenomanian) of the Obiraarea. This species was originally reported from the Koryak Range of the USSR and its distribution is now extended to Hokkaido. (3) Inoceramus virgatus Schliiter; This species is so variable
that we include in it "/. scalprum Bohm" as a synonym, giving a revised diagnosis. Examples
from Hokkaido occur in the middle to uppermost part of Member Mf of the Obira area, probably referable to the lower Middle Cenomanian; also in the Lower Cenomanian of the Oyubariarea.

works in the southern part of the Oyubari area,
central Hokkaido, and the northeastern part of
the Obira area, northwestern Hokkaido.
The results of these field works have been reported preliminarily in Japanese by Hirano et al.
(1981) and by Sekine et al. (1985) respectively,
showing fossil localities in route maps. The
official geological maps of the scale 1 :50,000 are
available for the two areas: i.e., Nagao et al.
(1954) for the Oyubari quadrangle, Tsushima etal. (1958) for the Tappu (pronounced Tap) andIgi et al. (1958) for the Horokanai quadrangles,

Introduction
The main purpose of this series of papers was
written at the beginning of Part I (Matsumoto
and Noda, 1986). Succeeding to the four species
described in Part I, three species from the Cenomanian of Hokkaido are described in Part II.
They are mainly based on the recent acquisitions by the Waseda University team of thestudents conducted by Hirano through fieldReceived July 6,1987.
146

836. Cenomanian Inoceramids from Japan - II
the latter two of which cover the main part of
the Obira area. The Cretaceous stratigraphy of
the Obira area was described in detail by Tanaka(1963), whose lithostratigraphic sUbdivision isstill available and cited in this paper. There isanother work by Tanabe et al. (1977), withwhom Matsumoto and Hirano cooperated.
Meanwhile, one of us (T.M.) was invited to
Waseda University to study some of the col1ections there. Furthermore, selected specimens
which T.M. examined at Kyushu University and
Hokkaido University have been added to thematerial of this study. Their localities are in the
Obira and Oyubari areas and also in the easternpart of the Kotanbetsu (Kotambets) area, i.e., in
the official geological map of the Soeushinai
quadrangle (Hashimoto et al., 1(58) northerly
adjacent to the Obira area. The fossil localitiesof the Kotambets area are precisely shown ina route map and stratigraphic column by Matsumoto and Okada (1973, text-figs. 7,8).
While the Cretaceous researches are continued
in Japan, one of us (A.A.) fol1ows the predecessors in the palaeontology and biostratigraphy of
the inoceramids. Some of Asai's col1ections fromthe northeastern part of the Obira area are added
to the material of this study. Also selected specimens of K. Tanaka's col1ections from the Obiraarea have been examined by one of us (T.M.).
The repositories of the described or mentioned specimens are as fol1ows with abbreviationin parentheses:
British Museum (Natural History) London(BM)
Geological Col1ections, Kyushu University,
Fukuoka (GK)
Geological and Mineralogical Col1ections,
Hokkaido University, Sapporo (GMH)
Geological Museum, Geological Survey ofJapan, Tsukuba (GSJ)
Sedgwick Museum, Cambridge (SM)
Palaeontological Col1ections, School of Education, Waseda University, Tokyo (WE)
The locality numbers have the prefix Y for the
Oyubari area, succeeding tf) those in Matsumoto(1942), Hirano et al. (1977) etc.; the prefix T(derived from Tappu) for the Obira area in the147

field works of Waseda University and the prefix
R (derived from Rumoi district) for the Obiraand adjacent areas in the field works conductedby Matsumoto. The prefix T has been used by
Matsumoto since 1942 for the localities of the
Saku-Abeshinai and contiguous areas in thenorthern Teshio Mountains. These T-numbers of
Matsumoto appeared in Part I but are not citedin this part. Therefore there would be no confusion with the T-numbers of Waseda University.
K. Tanaka's (1963) localities in the Obira area
have prefix NH.
As to the subdivision of the CenomanianStage, we fol1ow Kennedy (1986 in Reyment
and Bengtson) for the definition of the Lower,
Middle and Upper Cenomanian. The three substages have been defined on the ammonite zones
in the type area (Sarthe in the Paris Basin) andcan be extended to southern England and also tosoutheastern France. In certain sequences inJapan the correlatives of these substages are wel1
recognized and in such cases the terms Lower,
Middle and Upper Cenomanian are used in thispaper. When the correlation is not so definitive,these terms are avoided and we may write, forinstance, the lower part of the Cenomanian andso on. Even in the former cases, it is difficult to
set precisely the positions of the stage or substage boundaries in our sequences. Althoughsome species of the Inoceramidae may be usefulfor that problem, we do not intend to discuss theboundaries in this paper.
As to the abbreviated letters or symbols in
the measurements, we follow those used in Part
I. To avoid confusion we write in this paper BV,
LV and RV for both valves, left valve and rightvalve. For brevity we may write int.m., ext.m.,comp.int.m., etc. for the internal mould, externalmould, composite internal mould and so on.
The symbol ~ at the beginning of the measured
value means approximate or restored.
Systematic descriptions
Genus Inoceramus Sowerby, 1814

Type species: -Inoceramus cuvierii Sowerby,
1814.

Tatsuro MATSUMOTO, Akito ASAI and Hiromichi HIRANO

148

Remarks:- Genus Inoceramus has been used
in a broad sense, but currently Mytiloides Brongniart, 1822, Sphenoceramus B6hm, 1915 andBirostrina J. Sowerby, 1821 are excluded fromit as independent genera. There are still a numberof subgenera which are affiliated to the genus
Inoceramus and how to treat them may be a
problem. Such species as /. lamarcki Parkinson,/. hobetsensis Nagao et Matsumoto, /. iburiensis
Nagao et Matsumoto and /. teshioensis Nagao etMatsumoto, all of Turonian age, are examples of/. (Inoceramus) in a strict sense.
For the Cenomanian species, however, little
has been accomplished as to their taxonomy atgeneric or sub generic level, aside from thenomenclatorially invalid or doubtful ones proposed by Heinz (1932, etc.). For instance, /.
crippsi Mantell is a celebrated Cenomanianspecies, but according to Kauffman (personalcommunication to T.M. in a field excursion to a
Cenomanian locality in England, 1981) thisspecies may represent a genus independent of
Inoceramus.
As we have not comprehensively studied
numerous species from the Cenomanian ofEurope and other oversea regions, we have to use
Inoceramus in a fairly broad sense for the descriptions of species in this paper.

Inoceramus tenuis Mantell, 1822
Figures 1 - 3

1822. Inoceramus tenuis Mantell, p. 132.
1911. Inoceramus tenuis Mantell; Woods, p. 271, textfigs. 31-32 (non pI. 48, fig. 1).
1928. Inoceramus tenuis Mantell; Heinz, p. 60, pI. 4,
fig. 2.
1959. Inoceramus tenuis Mantell; Dietze, p. 858, pI. 1,

figs. 3-4.
1966. Inoceramus tenuis Mantell; Pergament, p. 44,
pI. 23, figS. 3-4;pl. 24, figs. 1-4.
1967. Inoceramus tenuis Mantell; Trager, p. 33, pl. 1,
fig. 8.
1982. Inoceramus tenuis Mantell; Keller, p. 59, pl. 2,
fig. 2.

Holotype:-BM. No. 5890 (figured by Woods,
1911, text-figs. 31-32), from the Chalk Marl ofHamsey, which one of us (T.M.) once examined
at British Museum (Nat. Hist.).
Material:-WE. P014T (Figs. I-la-e) (int.m.
of BV, with inner shell layer partly preserved)
collected by A. Takagi, H. Sekine, K. Hattori and
H. Hirano at loco T5201a83, the Kanajiri-zawa;
WE. POll T (comp. int.m. of LV: Figs. 1-2a-c,
and compo int.m. of deficient RV: Fig. 1-3) and
WE. P012T (Figs. 1-4a-b) (int.m. of LV, partlywith inner shell layer) collected by A. Asai at
loco T6238b84 of the Jiro-zawa; all Member Mf(defined by Tanaka, 1963) of the Obira area.
WE. P019T (Figs. 2-3a-c) (int.m. of BV) and fiveothers (1BV, 3LV and 1RV) collected by A. Asaiat loco T5222b84 of the Kanajiri-zawa, Member
Me (or possibly Md), Obira area. One of us (T.M.)
examined also K. Tanaka's Collections from the
Obira area, now kept in the Museum of theGeological Survey of Japan, with register numbers GSJ.F8215 (LV) from loco NH210 and
GSJ.F8216 (BV, int. and ext.m.) from loco
NH617, upper reaches of the River Obirashibe'
GSJ .F8217 (LV and immature RV) from loc:
~H419, Kaba-no-sawa and GSJ.F8218 (3 LV,
Immature BV and RV) from loco NH554 all in
nodules of limonitic tint, upper part of Member
Mf which contains Calycoceras orientale Matsumoto, Saito et Fukada.
GK.HlO083 (Figs. 2-1a c) (comp. int.m. of~ Figure 1.
Inoceramus tenuis Mantell
Page 148
1.a-e: WE. P014T (BV) from loco T5201a83, upper part of Member Mf, Obira area (Coll. A. Takagi and others)'
nght ~ateral (a), left lateral (b, c), anterior (d), and umbonal (e) views; 1c x2, others x1.5. Scale bar = 10 mm:
2a- C •• WE. P~llT (LV) from loco T6238b84, Member Mf, Obira area (Coll. A. Asai); lateral (a) anterior (b) andpostenor (c) VIews; x l . '3: WE. POllT (RV, deficient int.m. of the same individual as above LV) from loco T6238b84 (Coll. A. Asai)'xO. 9. Scale bar = 10 mm.
'
4a-b: WE. P012T (LV~ from loco T6238b84 (Coll. A. Asai); lateral (a) and anterior (b) views; xl.
5.; ~. P013Y (~V, With damaged apex of beak) from loco 2YC7045a79, Member M2, Oyubari area (Coll. R.
~onta); lateral view; xl.
photos by courtesy of Dr. M. Noda, except Ie, 2c by A. Asai.

836. Cenomanian Inoceramids from Japan - 11149

Tatsuro MATSUMOTO. Akita ASAI and Hiram ich i HIRANO

150

lb

/

,
\
\
\
\

"-

"-

2a' . . . .

836. Cenomanian Inoceramids from Japan - II
LV) and GK.HI0165 (Figs. 2-2a-c) (BV, compo
int.m.) collected by T. Matsumoto and H. Okada
at loc. RlOO, 800 m west of the Kiritachi Pass(see Matsumoto and Okada, 1973), from nodulesof limonitic tint in a mud~tone member whichcontains Calycoceras of the newboldi group.
WE.POI3Y (Fig. 1-5) (LV, lacking the apex ofbeak, int.m. partly with test) collected by R.
Morita at loc. 2YC7045a79, Kaneo-betsu, Member M2 of the Oyubari area (see Hirano et al.,1981 ).
Diagnosis :-Shell rather small, inequivalve andobliquely sub oval in outline, with the axis of
growth nearly straight or gently concave forward.
Left valve moderately convex, with prominentand incurved umbo; right valve gently convex.
Postero-dorsal part compressed. H larger than L,
as examplified by the holotype in which L/H =0.69 (LV) and 0.72 (RV); hinge line varied inlength from 1/2 to 2/3 in slL.
Anterior marginal part straight and nearly
perpendicular to the plane of valve, but anterodorsal part somewhat excavated; ventral margin
asymmetrically rounded, becoming more convex
with growth; posterior margin gently arcuate inpassing from the ventral margin and then becoming nearly straight, forming an obtuse angle

151

with the hinge-line.
Surface ornamented with fine concentric lirae
or rings, but incipient major concentric undulations may appear in some individuals.

Measurements:-See Table 1.
Observation:- The holotype from the Chalk
Marl of Hamsey, a classic locality in Sussex,
England (see Wright and Kennedy, 1984, p. 9), is
well preserved and the description by Woods(1911, p. 271) is clear. Its dimensions, whichwere omitted by Woods and measured by one ofus (T.M.), are shown in this paper (Table 1). The
length of the hinge line in the holotype is actually shorter than what Woods mentioned: "about
two-thirds of the height of the shell". The hingeline in some specimens from Hokkaido is nearly
two-thirds of the length of the shell. The ratio
sll seems to vary with growth as well as between
individuals.
SM.B42106 from the "Red Limestone" near
Louth, England, which was illustrated by Woods(1911, pI. 18, fig. 1) under I. tenuis, is not in
our opinion the named species, because it has a
sub rounded-sub quadrate outline, more evenly
rounded ventral margin, longer hinge line andTable 1. Measurements of selected specimens of I. tenuis.
Specimen
Holotype

Val.
LV
RV
WE.POIIT LV
RV
WE.POI3Y LV
WE.POI4T LV
RV
GK.HI0083 LV
GK.HI0165 LV

h
97.0
87.5
-50
33.0
36.0
29.3
57.0

H
L L/H bl/h
b/hs/1
.78 103.0 71.0 .69 34.0 .35.87 99.0 71.0 .72 25.0 .29 35.0 .46- -61.5 -41 .67 -17-37 .74 -51.5 -35 .68 -12 .24 -19 .51
25.5 .77 39.0 28.0 .72 -11 .33 -18 .71
26.7 .74 42.0 28.0 .67 12.0 .33 17.2 .64
24.5 .83 38.0 26.0 .68 9.3 .32 16.5 .67
44.0 .77 62.5 43.0 .69 27.3 .48 28.2 .69-86 -58 .67 - 30
I

76.0
76.0

s!L

ex

{3

'Y

0

140°

54°

-140°

55°

130°
130°
130°

54°
54°
57°

60°
.49 100°- -90°.54 -90°
.64
.67
.67
.63

54°

60°
90°
57°

~ Figure 2.
Inoceramus tenuis Mantell
Page 148
la- c: GK. HI0083 (LV, compo int.m.) from loco RIOO, 800 m west of the Kiritachi Pass on Highway 239 fromSoeushinai to Kotanbetsu (Coli. T. Matsumoto and H. Okada); lateral (a), anterior (b) and dorsal (c) views; xl.
2a- c: GK. H10165 (BV, int.m. with deficient apex of beak) from loc. RIOO (same as above); left (a) and right(b) lateral and posterior (c) views; xl.
3a- c: WE. PO 19T (BV, int.m.) from loc. T5222b84, Kanajiri-zawa, Member Me (possibly Md), Obira area (Coli.
A. Asai); x1.2. Scale bar = 10 mm.
Photos by courtesy of Dr. M. Noda.

152

TatsLlro MATSUMOTO, Akita ASAI and Hiramichi HIRANO

denser lirae on the shell surface as compared withthe holotype and other examples.
The specimens from Hokkaido are mostly
smaller than the holotype and their concentricrings are proportionally finer. Those from Germany (Trager, 1967; Keller , 1982) and thePacific side of the USSR (Pergament, 1966) arealso more or less smaller than the holotype. In
other words, the holotype from England may

represent a specially well grown individual.
GH.H10165 (Fig. 2-2) in our material is exceptionally large , being closer in size to theholotype . Its concentric lirae or rings are ascoarse as those of the holotype , and moreoverit has incipient concentric major undulations .
One of the specimens illustrated by Pergament(1966 , pI. 24 , fig. 3) is similar to GK.HI0165 inthese respects.

Figure 3_ Inoceramus tenuis Mantell
Page 148
A number of specimens embedded in a nodule from the upper part of Member
Mf at loco T5201 a83 (Coil. A. Takagi and others) (see also Fig. 1-1). Scale bar= 10 mm. Photo by courtesy of Dr. M. Noda.

-+ Figure 4. Inoceramus gradilis Pergament
Page 155
1a-d : GK. HI0163 from loco R100 on Highway 239 (Coli. T. Matsumoto and H. Okada); left (a) and right (b)lateral, posterior (c) and anterior (d) views of BV.
2a, b : WE. P008T from loco T50 17e83, Kanajiri-zawa (Coli. A. Takagi and others) ; LV, RV and another RV(?)
embedded with overlapping, in two views (a, b).
3a- c: WE. P016T from loco T6051h84, on the main course of the River Obirashibe (Coil. S. Ago and others) ;two lateral (a, b) and anterior (c) views of LV. 1,2 are natural size ; 3 slightly enlarged. Scale bar = 10 mm.
Photos by courtesy of Dr. M. Noda, without whitening.

836. Cenomanian Inoceramids from Japan - II

153

154

Tatsuro MATSUMOTO, Akita ASAI and Hiramichi HIRANO

2b836. Cenomanian Inoceramids from Japan - II
Comparison:-As Woods (1911, P. 272) has
already stated, this species resembles Birostrina
concentrica (Perkinson) but has less prominent
umbo of the left valve, higher value ofl/h or L/H
and less prominent concentric rings. Kauffman(1978, p. iv-4) foretells briefly that there aretransitional forms between I tenuis and "theBirostrina concentrica lineage", but places I
tenuis in the subgenus I (Inoceramus) instead ofBirostrina. I (Inoceramus) should have lessincurved and less prominent umbo of the left
valve, longer hinge line with broader posterodorsal flattened wing-like area and more distinctly developed major ribs, as compared with
Birostrina. In these respects this species is nota typical member of I (Inoceramus). It may
be situated at a transitional position between
Birostrina and Inoceramus, or it may be rather
closer to typical species of Birostrina than to thatof I (Inoceramus).
For the time being, we follow Kauffman torefer this species to Inoceramus, awaiting theissue of the Kauffman's descriptions of the
Cenomanian inoceramid species from Englandin further details.
Birostrina nipponica (Nagao et Matsumoto,1939) in a revised sense (see Pergament, 1966,
p. 32) has a narrower and more incurved umboof the left valve than the left umbo of I tenuis.
It has a smaller value of L/H and shorter hingeline than those of the latter. Its axis of growth issomewhat sinuous. In some of previously published papers I tenuis and certain other species
were misidentified with I nipponicus and a restudy of the so-called I nipponicus is necessary.
Occurrence:-According to Kauffman (1978),who studied the British inoceramids with theframework of the ammonite zonation by Kennedy (1971), I tenuis occurs characteristically~ISSin the Zone of Neostringoceras carcitanense(lower part of the Lower Cenomanian) andranges upward to the Zone of Turrilites acutus(middle part of the Middle Cenomanian). Keller(1982) records the range of I tenuis as Lower
Cenomanian to lower Middle Cenomanian in
the sequence of Germany.
On the basis of the specimens examined byus, the range of I. tenuis is from Member Me (orpossibly upper Md) to Member Mf (of Tanaka,1963) in the sequence of the Obira area. This
is in harmony with the range in England andGermany, but the most characteristic occurrence
is in the upper part of Mf. The GK specimens ofloco RIOO on the Soeushinai - Kotanbetsu route(Highway 239) came from the fossiliferous zone
with Calycoceras of newboldi group, which issomewhat higher than upper Mf of the Obiraarea. This zone may be referred to upper part of
the Middle Cenomanian, whereas N. carcitanense
was obtained at loco R81 of the same route well
below loco RIOO (see Matsumoto and Okada,
1973,figs.7,8).
The material from the Oyubari area is insufficient to tell the range and abundance of thisspecies. A single available specimen came from
Member M2 (Hirano et al., 1981), which is probably referred to the lower part of Cenomanian.

Inoceramus gradilis Pergament, 1966
Figures 4, S
1940. Inoceramus corpulentus McLearn var. a; Warren
and Stelck, p. 148, pI. 4, figs. 4-6.
1966. Inoceramus gradilis Pergament, p. 49, pI. 29, figs.
2-S;pl. 31,f"Jgs.1-2;pl. 32, fig. 1.

Holotype:- The specimen designated by Pergament (1966, p. 49, pI. 32, fig. 1) (no. 8-3580-74
in the text and no. 8-3580-75 in the explanation

Figure 5. Inoceramus gradilis Pergament
Page 155
la, b: WE. P01ST (LV) from loco TS017e83, Kanajiri-zawa (ColI. A. Takagi and others); lateral (a) and posterior(b) views.
2a, b: WE. P007T (LV) from loco TS016a83 (Coli. A. Takagi and others); lateral (a) and anterior (b) views, x1.2.
3a, b: WE. P017T (BV) from loco TS017e83 (Coli. A. Takagi and others); left (a) and right (b) lateral views.
4a-d: WE. P018T (BV) from loco TS019m83 (Coli. A. Takagi and others); left (a) and right (b) lateral, anterior(c) and umbonal (d) views.
All figures natural size, except 2a, b. Scale bar = 10 mm. Photos by courtesy of Dr. M. Noda.

Tatsuro MATSUMOTO, Akito ASAI and Hiromichi HIRANO

156

of plate, of which the latter may be misprinted),from the Cenomanian on the bay of Ugol'naya
at the north end of the Koryak Mountains.
Material:-·At least twelve specimens from
Hokkaido, some of which consist of slightly displaced left and right valves of the same individual. GK. HI0163 (Fig. 4-1) (BV, int.m., with test
remaining in the hinge and antero-dorsal part,of which RV somewhat displaced towards theventer and its last portion is not preserved) collected by T. M. with H. Okada in 1967 from loco
RlOO, 800 m west of the Kiritachi Pass on Highway 239 between Soeushinai and Kotanbetsu;
WE. P007T (Fig. 5-2) (LV, int.m., with test remaining in the anterior marginal part) from loco
T5016a83; WE. P008Ta, b, c (Fig. 4-2) (LV andtwo RV, int.m., with weathered test attaching on
the umbonal part of a and b, and anterior part ofa and antero-vental portion of b); WE. P015T(Fig. 5-1) (LV, int.m., with weathered test on
the umbonal and anterior marginal parts); WE.
P017T (Fig. 5-3) (LV, int.m., somewhat damaged
at the beak and in the antero-ventra-l part; also
young part ofRV, int.m., with test on the umbonal part) from loco T5017e83; WE. P018T (Fig.
5-4) (LV, int.m., with test on a portion of theumbonal part and RV of the same individual,
int.m., with test on the postero-dorsal portion)from loco T5019m83; all of the above seven collected by a field-work team of A. Takagi, H.

Sekine, K. Hattori and H. Hirano from theoutcrops of Member Mh on the Kanajiri-zawa, atributary to the River Obirashibe, Obira area
(Tappu quadrangle); WE. P016T (Fig. 4-3) (LV,with inner shell layer remaining on the majorpart) collected by S. Ago, Y. Tanaka and A.
Matsuzawa at loco T6051 h84 from the outcropof Member Mh on the main course of the River
Obirashibe, Tappu quadrangle, Obira area.
Diagnosis (translated from Pergament, 1966
with some revision):-Shell small to mediumsized, markedly inequivalve, inequilateral andhigher than long (H > L); left valve highly convex with incurved umbo, showing stepwisechanges of convexity from the beak to theventral margin with accompanied constrictions;right valve less convex than the left but constricted at periodic intervals.
Fine concentric lirae or rings on the young
part up to the first constriction; fairly crowded
concentric subcostae and/or ribs in the middle
stage; major concentric ribs develop in the late
growth-stage; sometimes ribs may be bifurcatedor intercalated, giving rise to somewhat irregular
aspect in ribbing.

Measurements:-See Table 2.
Observation:- The specimens from Hokkaido
listed above (in Material) show clearly the diag-

Table 2. Measurements of selected specimens of I. gradilis.
SpecimenVal.
GK.H10163 LV
RV
WE.P008Ta LV
b RV
WE.POI5T LV
WE.POI6T LV

22.8
31.0

16.0
21.0

WE.POI7T(sec. def.)

33.2
23.0

25.0
16.0

22.6
21.8

h=33.417.0 47.0
17.0 37.5

HI
-24
23.6

Ll
22.0
20.4

H2
45.0
39.7
50.5
41.0
37.4
49.0

L2
30.3
34.2
28.0
27.5
24.5

-11

~33.5

14.0

-75

-35

bl
15.5

b2
-22

12.5

17.5
-12

sl

s2 Ll/HI L2/H2 bI/Ll b2/L2 s2/L2
23.0 .91.69 .70.73 .75.86.86(sec. comp.)

.70
.68

-20

.65
>.68

.69
.67

~.60

(3 = 50 0

WE.POI8T

LV
RV
LV
RV

19.5

.75
-10

1=26.037.4 -1230.5

HI, Ll, bl, sl : measured at the fIrst constriction
H2, etc.
: measured at the second constriction

.47

.70

13.6
l/h=.78
.75
.79
.78
.81

.52
ex= -90 0.70836. Cenomanian Inoceramids from Japan - IInostic characters of L gradilis. GK. HIOl63 (Figs.
4-la-d) is very good in showing the left andright valves of one and the same individual andalso a part of the hinge plate and thus supplements the holotype from the Koryak.
Our specimens are small or medium-sized likethe holotype and certain other examples illustrated by Pergament (1966, pI. 28, figs. 2-5; pI. 32,
fig. 1) but we have not yet obtained somewhat
larger forms like those of Pergament (1966,
pI. 31, figs. 1-2)
The axis of growth extends obliquely to thepostero-ventral extremity in reference to thehinge line, which is often concealed in the left
valve by the inflated and incurved umbonal
part but can be seen inside the left valve of GK.
H10163 as well as on the dorsal margin of rightvalve.
The abrupt change in the convexity from thebeak to the ventral margin with accompanied
constriction occurs in the left valve at least
twice during the growth. We can recognize thecorresponding constrictions on the right valve,
although sometimes they may not be so wellmarked as those on the left valve. The dimensions at the 1st and 2nd constrictions are shownwith HI, L! etc. and H2, L2 etc. (see Table 2).
Because of the umbonal convexity or inflation,
the ratio bIlL! is fairly large (0.65-0.70).
Comparison :-Inoceramus corpulentus McLearn (1926, p. 123, pI. 21, figs. 5-7) from the
Smoky River Formation of Alberta, Canada ishigher than long and much convex along the axisof growth, and has nearly vertical, high anterior
marginal part. The plaster cast of its holotype,
kindly sent by Dr. J. A. Jeletzky from theGeological Survey of Canada to Kyushu University (GK. H9624), shows that it is evenly convex
and does not show such abrupt changes as thosein L gradilis. It is ornamented with fine concentric lirae (nearly smooth on the intm.) in theyoung stage, then weak concentric subcostae andweak to moderate concentric ribs combined withconcentric rings in the late stage. Despite its
small size there is a postero-dorsal flattened area.
It is described as nearly equivalve. We agree with
McLearn in regarding L corpulentus as allied to157

I. apicalis Woods, 1912. These two species are
Turonian in age.
Taking all the above facts into consideration,
we regard the similarity of L gradilis to L corpulentus as superficial. There is no phylogenetic
affinity between them.
The form described under L corpulentus var. a
by Warren and Stelck (1940, p. 148, pI. 4, figs.
5-6; 4?) from the Dunvegan Formation (Cenomanian) of Alberta, Canada looks very similar tothe left valve of L gradilis, although it is smaller
than any of the specimens as described above.
Occurrence:-A well preserved (BV) exampleof this species was obtained from the outcrop of
mudstone at loco RI00 immediately after theconstruction of Highway 239. At the same locality L tenuis and Calycoceras aff. e. asiaticum, i.e.
e. of the newboldi group, were obtained among
others. Hence the age of this mudstone is Middle
Cenomanian.
This species has been obtained not infrequently at the four localities in the Obira area,
i.e. locs. T5016a83, T5017e83, T5019m83 andT6051h84 ofSekine etal. (1985), from the mudstone of Member Mh of Tanaka (1963), which
is probably referred to the upper part of the
Cenomanian. The occurrence of both valves, with
only slight displacement is noteworthy.

Inoceramus virgatus SchlUter, 1877
Figures 6-8
1836. Inoceramus lamarcki Sowerby; Go}dfuss, p. 114,
pI. 111, fig. 2.
1842. Inoceramus laevigatus Leymerie, p. 9, pI. 10,
fig. 4.
1877. Inoceramus virgatus Schliiter, p. 257.
1911. Inoceramus etheridgei Woods, p. 278, pI. 49,
figs. 2-4.
1914. Inoceramus scalprom Bohm, p. 599.
1959. Inoceramus scalprom Btihm, Moskvin, p. 142,
pI. 1, fig. 4.
1966. Inoceramus scalprom Btihn, Pergament, p. 46,
pI. 25, figs. 1-4.
1967. Inoceramus virgatusSchliiter;Trtiger,p.29,pI.1,
figs. 1-7.
1978. Inoceramus virgatus Schliiter; Somay, p. 510,
pI. 2, fig. 4.
1978. Inoceramus virgatus scalprom Bohm; Somay,
p. 509, pI. 2, figs. 2,5.

158

Tatsuro MATSUMOTO, Akito ASA I and Hiromichi HIRANO

1982 . Inoceramus virgatus virgatus Schliiter; Keller,
p. 51 , pI. 1, fig . l.
1982. Inoceramus virgatus scalprum Bohm; Keller,
p. 54 , pI. 1, fig. 2.
1985. In oceramus virgatus virgatus SchlUter; Kaplan,
Keller and Wiedmann, pI. 8 , figs. 3,4 .

Types :- The holotype of 1. virgatus Schluter,1877 is the specimen illu strated by Goldfuss(J 836 , pI. Ill , fig. 2) from Lower Saxony ofGermany. None of us has examined the original
specimen and we depend on a photograph by
Sornay (1978 , pI. 2 , fig . 4). The holotype of 1.
scalprum Bbhm , 1914 is one of the sy ntypes of
1. etheridgei Woods (1911 , p. 278 , pI. 49 , fig. 3)(SM. B297) from the Totternhoe Stone (Zone ofHolaster subglobosus) of Burwell , England. It
is a left valve , whereas the topotype (anothersyntype) illustrated by Woods (1911 , pI. 49 ,fig . 4) is a right valve. One of us (T . M.) once
studied them at Sedgwick Museum , Cambridge .
Material:-WE. POOST (Fig. 6) (comp.int.m.
of BV, with test attached in a portion) and WE.
POO6T (Fig. 7 -2) (int.m. of RV , with test remain ing in the postero-dorsal part) from Member Mf
at loc o TS112e83, the Korinto (Corinth)-zawa ,a branch of the Kanajiri-zawa ; WE . P003T (Fig .
8-1) (comp. int.m. of RV) from the uppermost
part of Member Mf at loco TSOSla83 and WE .

Figure 6. Inoceramus virgatus SchlUter
Page 157
a-d: WE. P005T (BV) from locoT5112e83, Korinto-zawa, the uppermost part of Member Mf, Obira area (ColI.
A. Takagi and others); lateral view of deficient LV (a) with oblique view of RV, lateral view of RV (b), anteriorview of LV (c), anterior view of RV (d) with umbonal part of LV; All figures natural size . Scale bar = 10 mm.
Photos by courtesy of Dr. M. Noda.

836. Cenomanian Inoceramids from Japan - II

Figure 7. Inoceramus virgatus Schliiter
Page 157la- b: WE. P004T (BV) from lac. T5051c83 , the uppermost part of Member Mf, Kanajiri-zawa, Obira area (Coil.
A. Takagi and others); a x I, b x 1.2.
2: WE. P006T (RV) from loco T5112e83 , Korinto-zawa, the uppermost part of Member Mf, Obira area (Coll. A.
Takagi and others) ; xO.8.
3: WE . POIOT (LV) and 4 : WE. P009T (RV), both from lo co T623 8b84, Jiro-zawa, Member Mf, Obira area (Coll.
A. Asai); x l.
Scale bar = 10 mm . Photos by co urtesy of Dr. M. Noda.

159

160

Tatsuro MATSUMOTO, Akito ASAI and Hiromichi HIRANO

P004T (Fig. 7-1) (comp. inLm. of RV, with
inner shell layer partly attached) from the same
horizon at loco T5051c83; all the four collectedby A. Takagi, H. Sekine, K. Hattori and H.
Hirano. WE. P009T (Fig. 7-4) (comp.inLm. of
RV) and WE. PO lOT (Fig. 7-3) (comp. inLm. ofLV) collected by A. Asai at loco T6238b84, the
Jiro-zawa, a branch of the River Obirashibe. All
the above occurred in the Obira area. GMH. 7247
(Fig. 8-2) (LV, comp.inLm., with test on anterior
marginal part) from near the contact withserpentine in the upper reaches of the Hakkinzawa, Oyubari area.
Diagnosis:-Shell slightly inequivalve, somewhat inequilateral, gently to moderately convex
in the main part of the valve and compressed in
the postero-dorsal part; the left valve slightly
more convex than the right; umbones terminal,
and the left umbo slightly curved inward andforward.
Outline of shell broadly sub oval or sub circular;
height being somewhat greater or nearly as greatas length. Hinge line of moderate length on the
average, forming an angle of 55° to 65° with theaxis of growth, which is nearly straight in theyoung stage or throughout growth but may
sometimes be curved gradually forward or backward in the late stage. Antero-dorsal part nearly
perpendicular to the plane of the valves, sometimes concave near the umbo; anterior margin
nearly straight; ventral margin fairly convex ornearly semi-circular, passing to gently arcuate
posterior margin which forms an obtuse angle
with the hinge line.

Surface of shell ornamented with very fineand dense concentric lirae and faintly perceptible
major concentric undulations, sometimes withsub costae or weak ribs on the summits of theundulations. Delicate radial lines or striae often
discernible on the internal mould, being probably
impressions of the internal structure.

Measurements:-See Table 3.
Observation:-This species is fairly variable
and we agree with Sornay (1978) who haspointed out that L scalprum Bohm, 1914 (= L
etheridgei Woods, 1911) is not separable from L
virgatus Schluter as an independent species.
Sornay interpreted them as geographical subspecies, because the former is dominant in Englandand France and the latter is so in Germany. Keller(1982) followed Sornay in the sub specific nomenclature, L virgatus virgatus and L virgatus
scalprum, but examples of the two forms occur
abundantly in the same area of Germany. According to him the two "subspecies" are worldwide in the Lower Cenomanian and lower partof the Middle Cenomanian. The coexistence ofthe two subspecies in the same age of the sameprovince with similar abundance is biologicallypeculiar. Should the two forms show constantly
the differences as tabulated by Keller (1982,
p. 57, table 1), it would be better to separate
them as distinct species.
We have examined the specimens from
Hokkaido and also illustrations of the specimensfrom oversea areas, with the result that thisTable 3. Measurements of selected specimens of I. virgatus.
Specimen
WE.P003T
WE.P004T
WE.P005T

WE.P006T
WE.P009T
WE.P010T
GMH.7247
SM.B297

Val.
h
I/h
-42
RV -48.88
LV -26-22.85
RV -26-24.92
LV 33.0 28.5 .86
RV 54.8 43.2 .79
RV 92.0
77.0 .84(distorted)
RV(distorted)
RV(distorted)
LV
LV 75.0 70.0 .93
LV 58.2 51.4 .88

H

L

-54
-41
-28
-24
-30.5 -26
40.0
28.4
56.5
43.4
99.0
78.0
-96
-80
-50
-32
-44
-41.5
87.0
72.0
55.0
59.0

L/H
.76
.86
.85

.71
.77
.79
.83
.64
.94
.83
.93

b

10.0
5.0
14.0
13.5

-17

b/h

.38
.19
.25

.29

sll

s/L

a

i3

'Y

-28
.67
-17
.77
-17.5 .73
21.0.74
23.7 .55
37.0 .48
38.0
23.5
27.5
50.0 .71
-27
.53

.68

-900

65 0

-90 0

-

1300
123 0
123 0

60 0
55 0
55 0

1050
105 0

-

1400
1300

65 0
63 0

-100 0
105 0
1100

77 0
900

1200
~130°

55 0
-70 0

.71
.67
.74
.55
.47
.47
.73
.66
.69
.49

836. Cenomanian Inoceramids from Japan - II
species is so variable that it is not always subdivided into two forms. In other words , "I.
virgatus scalpntm" is merely one of varieties. For
example , WE. P009T is higher than long (H > L)
but its axis of growth is concave to the anterior.
WE . POIOT, among many others, from the same
locality as WE. P009T , is as high as long (H = L)
but its axis of growth is somewhat convex to the161anterior. As Somay has stated , the mode ofpreservation , such as the presence or absence ofthe test or the effect of secondary deformation,
may give apparently different aspects. Therefore ,we should continue to examine more examples.
In this paper we call this species 1. virgatus in acomprehensive concept.
The examined specimens from Hokkaido andPage 157
Figure 8. Inoceramus vi!-gatus Schliiter
1: WE. POO3T (RV) from lac. T5051a83, same as for Fig. 7-1; x i.
,
2 : GMH. 7247 from the Hakkin-zawa near the contact with serpentinite , Oyubari area; x 1. Scale bar = 10 mm .
Photos by courtesy of Dr. M. Nod a.

162

Tatsuro MATSUMOTO, Akito ASAI and Hiromichi HIRANO

the hitherto illustrated ones from Europe, Central
Asia and the Pacific province of the USSR are
mostly medium sized. GMH. 7247 from the
Oyubari area is much larger than them, butessentially similar to them in other characters. It
is provisionally included in this species, but wereserve a possibility that it could be an allied but
different species.
Comparison:- The affinity of this species isproblematic. In the outline and gentle convexityof the valve, this species is somewhat similar to
1. atlanticus (Heinz, 1936), but the latter has regular concentric ribs in addition to the dense andfine lirae, as seen in the lectotype, BM. Ll038(= I. crippsi var. reachensis Woods, 1911, pI. 49,
fig. 1), and also Gueranger's specimen (Somay,
1978, pI. 1, fig. 4). 1. anglicus Woods, 1911
(p. 264, pI. 45, figs. 8-10, text-fig. 29) from theUpper Albian and basal Cenomanian of England,
Germany and various regions of the world, is alsosimilar to 1. atlanticus and 1. virgatus in shellform, but has fairly crowded, narrow but distinct
and regular concentric ribs. Only on the shellsurface of its young stage the dense and fine lirae
are discernible.
The group represented by these species (andprobably also 1. crippsi Mantell, 1822) is not
the subgenus l. (Inoceramus) of the strict sense.
In this paper it is provisionally referred to
Inoceramus of a broad sense. The shell and hinge
structure have yet to be investigated carefully.
OCCU17'ence:- According to Keller (1982), thisspecies ranges from the upper Lower Cenomanianto the middle of Middle Cenomanian and is
distributed world-wide.
In Hokkaido the examined specimens fromthe Obira area range stratigraphically from the
middle to the uppermost part of Member Mf of
Tanaka (1963). This is probably within therange concluded by Keller, because Turrilites
acutus Passy occurs in the overlying Member Mg.
The large specimen from the Hakkin-zawa of the
Oyubari area may have come somewhere in thesequence from the Lower Cenomanian Sharpeiceras bearing bed to the Middle Cenomanian bed
with Cunningtoniceras sp.

Summary
As a summary the species described in thispaper are listed below with indication of theirknown age and area in Japan.
Inoceramus tenuis Mantell, common in the
Middle Cenomanian of the Obira and adjacentareas and begin to appear in the Lower Cenomanian of the Obira and Oyubari areas.
Inoceramus gradilis Pergament, not infrequentin the Middle and Upper Cenomanian of the
Obira and adjacent areas.
Inoceramus virgatus SchlUter, not infrequent
in a zone from the Middle to uppermost part ofMember Mf in the sequence of the Obira area.
This is lower than the Tu"ilites acutus bearing
Member Mg and probably referable to the lower
Middle Cenomanian; also doubtfully in theLower or Middle Cenomanian of the Oyubari
area.
These three species have been well known
world-widely, but this is the first describedrecord in Japan. We would expect more examples
to be obtained from various areas in Japan, sothat their systematic positions and stratigraphic
occurrences may be made clearer.
Acknowledgements
We wish to thank Messrs. A. Takagi, H. Sekine,
K. Hattori, S. Ago, Y. Tanaka, R. Morita and A.
Matsuzawa for their kind supply of the specimens for this study which they obtained throughthe field works conducted by one of us (H. H.)
when they were students of Waseda; also Dr.
Hakuyu Okada for his kind help in the fieldwork with one of us (T. M.). Thanks are extended to Professor Makoto Kato and Dr. Nachio
Minoura of Hokkaido University and Drs. Nobukazu Kanbe, Keisaku Tanaka (formerly) andToru Sakamoto of the Geological Survey ofJapan who generously let one of us (T. M.) investigate freely the inoceramid specimens kept in
the respective institutions; also to Mr. D. Phillipsof the British Museum (Natural History) andMr. A. G. Brighton of the Sedgwick Museum fortheir kind assistance to one of us (T. M.) for the836. Cenomanian Inoceramids from Japan - IIstudy of relevant specimens.
Dr. Jost Wiedmann of the University ofTiibingen, Dr. J. A. Jeletzky of the Geological
Survey of Canada and Professor Kiyotaka Chinzei
and Dr. Terufumi Ohno of the University of
Kyoto have kindly supplied us with the xerox
copies of some references which were inaccessible to us.
We are much obliged to Dr. Masayuki Noda
for his friendly help in taking photographs of thedescribed specimens as well as for fruitful discussions.
References
B6hm, J. (1914): Zusammenstellung der Inoceramen der
Kreideformation (Nachtrag). Jb. kgl. preuss. geol.
Landesanst., vol. 35, no. 3, p. 595-599.
Dietze, H. (1959): Die Inoceramen von Oberau in
Sachsen, Obercenoman bis Unterturon. Geologie,
vol. 8, no. 8, p. 856-883.
Goldfuss, A. (1836): Petrefakta Germaniae. pt. 2,
p. 106-118, pis. 108-115, DUsseldorf.
Hashimoto, W., Nagao, ~. and Kanno, S. (1958): Explanatory text of the Geol. Map of Japan, Soeushinai sheet, Scale 1:50000. Hokkaido Develop.
Agency. (J).
Heinz, R. (1928): tiber die Oberkreide-Inoceramen SUdAmerikas und ihre Beziehungen zu denen Europas
und anderer Gebiete. (Beitrage zur Kenntnis deroberkretazischen Inoceramen V.) Mitteil. Mineral. Geol. Staatsinst. Hamburg, vol. 10, p. 42-97,3 pis.
--(1932): Aus der neuen Systematik der Inoceramen.
(Beitrage zur Kenntnis der Inoceramen XVI.) Ibid.,
vol. 13, p. 1-26.
--(1936): Inocenimidos de Alicante, Valencia yBaleares (lnoceramen 15). Bol. Soc. Esp. Hist. Nat.,
vol. 36, no. 2, p. 91-99, 1 pI.
Hirano, H., Matsumoto, T. and Tanabe, K. (1977): MidCretaceous stratigraphy of the Oyubari area, central
Hokkaido. Palaeont. Soc. Japan, Spec. Pap., no. 21,
p.1-10.
- - , Ando, H., Hirakawa, M., Morita, R. and Ishikawa,T. (1981): Biostratigraphic study of the Cretaceous
System in the Oyubari area, Hokkaido Part 2.
Gakujutsu Kenkyu, School of Education, Waseda
Univ., Ser. Bioi. & Geol., vol. 30, p. 33-45 (J).
Igi, S., Tanaka, K., Hata, M. and Sato, H. (1958): Explanatory text of the Geol. Map of Japan, Horokanai sheet, Scale 1 :50000. Geol. Surv. Japan (J).
Kaplan, U., Keller, S. and Wiedmann, J. (1985): Ammoniten- und Inoceramen-Gliederung des norddeutschen Cenoman. In Kollman, H. A. (ed.);163

Beitrage zur stratigraphie und Palaontologie dermittleren Kreide, Zentral-Europe. Osterr. Akad.
Wiss., Schriftenreihe d. Erdwiss. Komm., vol. 7,(for 1984), p. 307-347,8 pIs.
Kauffman, E. G. (1978): British Middle Cretaceous
inoceramid biostratigraphy. Ann. Mus. d'Hist. Nat.
Nice, vol. 4, (for 1976), p. iv-1-iv-12.
Keller, S. (1981): Die Oberkreide der Sack-Mulde bei
Alfeld (Cenoman-Unter-Coniac). Lithologie, Biostratigraphie und Inoceramen. Geol. Jahrb., Reihe
A, Heft 64, p. 3-171, pis. 1-8.
Kennedy, W. J. (1971): Cenomanian ammonites fromsouthern England. Spec. Pap. Palaeont., no. 8, 133
p., 64 pIs.
- - (1986): Ammonite biostratigraphy of the Albian tobasal Santonian. In Reyment, R. A. and Bengtson,
P. (compil.): Events of the Mid-Cretaceous. Final
Report on results obtained by IGCP Project No. 58,
1974-1985, Appendix I. p. 129-144, pIs. 1-21,
Pergamon Press, Oxford.
Leymerie, A. (1842): Sur Ie terrain cretacee du departement de l'Aube, Part II. Mem. Soc. geol. France,
vol. 5, 34 p., 17 pIs.
Mantell, G. (1822): Fossils of the South Downs; or illustrations of the geology of Sussex. 320 p., 42 pIs.,
London.
Matsumoto, T. (1942): Fundamentals in the Cretaceous
stratigraphy of Japan, Part I. Mem. Fac. Sci.,
Kyushu Imp. Univ., Ser. D., vol. 1, p. 130-280.
--and Noda, M. (1986): Some inoceramids (Bivalvia)
from the Cenomanian (Cretaceous) of Japan - 1.
New or little known four species from Hokkaido
and Kyushu. Trans. Proc. Palaeont. Soc. Japan,
N. S., no. 143, p. 409-421, pIs. 81-85.
- - and Okada,H. (1973): Saku Formation of the Yezo
geosyncline. Sci. Repts., Dept. Geol., Kyushu Univ.,
vol. 11, no. 2, p. 275-309 (J).
McLearn, F. H. (1926): New species from the Coloradoan of Lower Smoky and Lower Peace Rivers,
Alberta. Geol. Surv. Canada, Bull., vol. 42, p. 117126, pIs. 20-23.
Moskvin, M. M. (1954): Atlas verchnemolovo; faunyserernogo Kavkaza i Kryma. 130 p., 23 pIs.,
Moscow (R).
Nagao, S., Osanai, H. and Sako, S. (1954): Explanatory
text of the Geol. Map of Japan, Oyubari sheet,
Scale 1 :50000. Hokkaido Develop. Agency. (J).
Nagao, T. and Matsumoto, T. (1939): A monograph of
the Cretaceous Inoceramus of Japan. Part I. Jour.
Fac. Sci., Hokkaido Imp. Univ., Ser. 4, vol. 4,
p. 241-299, pIs. 23-34.
Pergament, M. A. (1966): Zonal stratigraphy andInoceramus of the lowermost Upper Cretaceous of
the Pacific coast of the USSR. Trans. A cad. Sci.
USSR, Geol. Inst., vol. 149,83 p., 36 pIs. (R).
Schliiter, C. (1877): Kreide-Bivalven. Zur Gattung

Tatsuro MATSUMOTO, Akito ASAI and Hiromichi HIRANO

164

Inoceramus. Pali1ontographica, vol. 24, p. 249288, pIs. 36-39, Stiittgart.
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Fossils, Palaeont. Soc. Japan, no. 38, p. I-IS (J).
Sornay, J. (1978): Precissions paleontologiques etstratigraphiques sur divers Inocerames Cenomaniens
et, en particulier, sur ceux de la Sarthe figures par
E. Gueranger en 1867. Geobios, vol. 11, no. 4, p.
SOS-SIS, 2 pIs.
Tanabe, K., Hirano, H., Matsumoto, T. and Miyata, Y.
(1977): Stratigraphy of the Upper Cretaceous
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3, p. 181-202 (J).
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Biostratigraphie der Inoceramen des Cenomans bis

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Warren, P. S. and Stelck, C. R. (1940): Cenomanian andTuronian faunas in the Pouce Coupe district,
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1-4.
Woods, H. (1911): A monograph of the Cretaceous
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4S-S0.
--(1912): Ditto, vol. 2, part. 8, Ibid. for 1911, p.
28S-340, pIs. Sl-S4.
Wright, C. W. and Kennedy, W. J. (1984): A monographof the Ammonoidea of the Lower Chalk. Part 1.
Ibid., p. 1-126, pIs. 1-40, (Pub. No. S67, part ofvol. 137 for 1983).
(R): in Russian. (J): in Japanese with English abstract.

Abeshinai 'tCf.=E;p;j, Hakkin-zawa B~iR, Horokanai ~bnp;J. Jiro-zawa lXJl~iR, Kaba-no-sawa :fJ/~ / iR, Kanajiri-zawa ~miR, Kaneo-betsu ~.I'f!5]U, Kiritachi fJli., Korinto (Corinth)-zawa ::r !! :,/I- iR, Kotanbetsu (Kotambets) i;fJ-5]U, Obira Ij'f, Obirashibe ,j'f~, Oyubari :k6'51, Rumoi~lijf, Saku fti:~, Soeushinai jf.;lj:.p;j, Tappu (Tap) ~:ffl, Teshio :;R.I;\!.

*~B.*~/7=7:'/~.~/~5A~-D . • ~~1<~~h*~~~*~~~~~k3~ : ~t.~.O)~*~c£-:) ~lXO) 3 ~~~G)(!i . 1ZIjf- Lt.:. (.E!. L~:g~cltJ1>iJUnoceramus ~I'~
8':J~cre?

(1) Inoceramus tenuis Mantell. tc;b;lJ'~~, ;f411b~c}j£tft,:/HI!lO)*g~M, Ii'lJ'L'F9tUWHDiJ~~ 7.:> t.:vt"('ffrt~cjlfl,'iJ~, ,ijl(;~~M~cli'lJ'L.'F9:1*:II!9f*:iJ;~~ .fe~-r7.:>:: ciJ~~7.:>.
Birostrina concentrica ~c1J;J.7.:> iJ~, tc~lJHflliJ~m <, p;j::iJf:BlIIliJ~~~ < , ~*.lJliJ~~~~ <~'W$iJ~
OOlit~C3f:!!HI::-r 7.:>. 'j'f, i;fJ-5]U!1!!J;gl(c :k6'51!1!!J;gl(0)~ /7 = 7 :'/"F$~<P$~C. L, .~~O)
JlFf8':J.1±l c w.\I~-r 7.:>.
(2) I. gradilis PergamentJj,~<p~, tc;b~ L ;IJ'~~ ; tc~lt?ili ~ I) J: '? '"( ,ijl(;~flB~c~H 'J5!:

<

<

<

<

<

~8':J~c~~ L, -t:-:: ~C tfhiJ~~7.:>. ;b~lt~ I) J: I) iJ;(g;I,'iJ~%JJ;t Lt.: tfhlt~7.:>. ~O)~mu
ItJ5!:~8':J~C(i)~1v Effrt, (1i)1i'lJ'L.'F9:1*:O)~~/j'HD, (iii)OOlitt.J:HDO).fe~ c ~(I:: L, )ttt· ~A.iJt~ I)~~;IJ'~IB!u~~7.:>. ;b~ltI. reduncus Pergament ciJ,t.J:'J1J;J.'"(I,'7.:>. i;fJ-5]Uc /j'fO).p$· J:$~ /7= 7 :'/~c.-r7.:>.

I. virgatus SchlUter.tt*5]U~JUt.~c t!:h '"(I, ,t.: I. scalprum Bohm ~1i'lJ-~p;j0) 1 ~Jr:
c L, qj(lE~aLt.:. tc;b*~~~, ~ltf:!!!~cjlfl,'iJt, tc~lt~~?ilii IJ, ~~~~*.lJl~j,'L..
~*- '"(1,'7.:>. *F9MiJ'::k~O)*g~M~, H c LI;l:t;tt:f~~iJ', I.' <l?iJ'H> L ; ~~I;l:~ <, ,ijl(;~flBI;l:::h~55'~65' ~iil:!*.lJl:l*:~c~ I), ~WJ~cilrJJZ.I;l:r~::iJtc[!:!]O)~7.:> l,'IIIl*.lJl~td-:: c ~ ~7.:>.
~~iIfftCIi'lJ'L.'F9:1*:O)*JIIWtdk*.lJl c ~ 7.:> I, '1I!9f*: (}jj]O)ilii~~~It) iJ~~7.:>. :: O)II!9f*:iJ~ ~ ~ c!li <t.J:
hi! I. at/anticus Heinz tcjlf <t.J: 7.:>. ~p;jiIfftc1&M:I*:O)~*.lJliJ~~to I) ~1Ib ~h7.:>. 'j'f!tl!J;gl( Mf(3)0)<P$~.J:$K.L,:k6'51K~*~0).ft~~IJ,.~~0)~/7=7:'/"FB~<p$O).1±lc~~-r7.:>.

a*~D'~*OOA'fH£~

Trans. Proc. Palaeont. Soc. Japan, N. S., No. 147, pp. 165-179,8 Figs., October 30,1987

837. ONTOGENETIC SHELL VARIATION AND STREAMLINING
OF SOME CRETACEOUS AMMONITES*
KAZUSHIGE TANABE and YASUNARI SHIGETA
Geological Institute, University of Tokyo, Tokyo 113, Japan

Abstract. Comparative shell shape analysis of some Cretaceous ammonites has provided
significant differences in the ontogenetic pattern and variation of geometric coiling parameters.
The differences are especially conspicuous in the distance of venter from coiling axis (D), relative whorl thickness (S) and flank position (F), all of which are key factors for consideringhydrodynamic efficiency of the shells. In every species, the ranges of variation of the geometricparameters tend to decrease with age. At the same growth stage, intraspecific variation ofparameters Sand D is largest in the heavily ornamented morphotypes (Acanthocerataceae)
and heteromorphs (Scaphitaceae), intermediate in fine-ribbed platycones (Lytocerataceae),
and smallest in the weakly ribbed, highly streamlined involute-compressed morphotypes(Hypophylloceras, Placenticeras and most Desmocerataceae). This evidence strongly suggests awide variety of adaptive designs of the shells related to the mode of life of ammonites.

Hydrodynamic efficiency of shell shape in fossil
ectocochiliates has recently been discussed by
Ward (1980) and Chamberlain (1981). Thesepapers rely on generic level analysis of certain
simple shell shape parameters over various
taxonomic groups. Intra- and interspecific variation of shell shape has also been examined
extensively in the Upper Paleozoic Agoniatitida
and Goniatitida (Kullmann and Kant, 1970,
1972; Kant, 1977; Kant and Scheuch, 1973,
1980; Saunders and Swan, 1984) and Mesozoic
Ammonitida (Westermann, 1966; Bayer and
McGhee, 1984; Ward, 1980, 1986), but the
ontogenetic variation of shell geometry has little
investigated in the Cretaceous ammonites. This
paper presents quantitative data on the ontogenetic change and variation of shell shape in somelate Cretaceous ammonite species, and discusses
their adaptive significance for streamlining.

In trod uction
The paleoecology of ammonites has long been
discussed from various viewpoints. Althoughopinions on life habits are still divided as towhether ammonites were bottom dweUing or
nektoplanktonic, many authors have accepted
the idea that most normally coiled ammonites
had a certain degree of swimming ability. This
interpretation is largely based upon indirect
paleontologic evidence such as comparative
anatomy (Mutvei, 1964; Mutvei and Reyment,
1973; Jordan, 1968; Stiirmer, 1970; Lehmann,1976) and similarity in fundamental shell morphology to living Nautilus (Trueman, 1941).
Quantification of hydrodynamic properties of
ectocochiliate cephalopod shells has been madeexperimentally using actual specimens (Schmidt,
1930; Kummel and Lloyd, 1955) and scalemodels (Chamberlain, 1976, 1981; Chamberlain
and Westermann, 1976). The experiments demonstrated that the variation in shell geometrycaused significant variation in drag coefficients.

Material and methods

Material- Twenty Cretaceous ammonite species listed in Table 1 were treated in this study.
Most species are represented by several individuals which were preserved in single calcareous*Received July 23, 1987; read February 2, 1985 atUniversity of Tokyo.

165

166

Kazushige TANABE and Yasunari SHIGETA

Table 1. List of material. Samples with prefix R are from the Cenomanian-5antonian of the Obira area, northwestern
Hokkaido (see Tanabe et ai., 1977, figs. 4-11 for localities and ages). The localities and ages of the remaining
samples are as follows. M135 and PM3007: Upper Turonian of the Manji area, central Hokkaido (see Tanabe
et ai., 1978, fig. 1 for localities), S221lp and S3006: Lower Campanian at Matsumoto's (1942, pi. 12) loco
T281, middle course of Abeshinai River, Saku area, northern central Hokkaido, Hb-lO: from river gravel inthe upper course of Nakafutamata River, Haboro area, northwestern Hokkaido (derived from the Coniacian).

Major taxonomy
Phylloceratina
Phyllocerataceae
Lytoceratina
Lytocerataceae

Sample & locality

Species(Spath)R4018 (N= 5) , Obira(Jimbo)Yabe
Gaudryceras denseplicatum (Jimbo)

R4020 (N= 6), Obi ra
S3006 (N=I7), Saku
R4020 (N= 5), Obi ra

Hypophylloceras subramosum

Tetragonites glabrus

Tetragonites popetensis

Ancyloceratina
Scaphitaceae

Scaphites planus(Yabe)

Otoscaphites puerculus

Ammonitina
Desmocerataceae

Desmoceras japonicum(Yabe)

Tragodesmoceroides subcostatus
Damesites damesi

Hoplitaceae
Nautilida
Nautilaceae

MatsumotoMatsumoto(Jimbo)Damesites semicostatus Matsumoto
Damesites sugata (Forbes)
Desmophyllites diphylloides (Forbes)
Neopuzosia ishikawai (Jimbo)
Subprionocyclus bravaisianus (d'Orbigny)
Subprionocyclus neptuni (Geinitz)
Reesidites minimus (Hayasaka & Fukada)
Yubariceras yubarense Matsumoto, Saito & Fukada
Yubariceras japonicum Matsumoto, Saito & Fukada
Placenticeras intercalare Meek
Damesites ainuanus

Acanthocerataceae

R2110 (N= 4), ObiraR2110 (N= 7), Obira(Jimbo)Nautilus pompilius

Linne

nodules embedded in the Upper Cretaceous
deposits of Hokkaido, Japan. The localities andages of the samples examined are summarized
in the explanation of Table 1. Specimens of
Scaphites planus and Otoscaphites puerculus
were studied biometrically by Tanabe (1977),
and measurements by him are cited in this paper.
In addition to these ammonites, single matureshells of Placenticeras intercalare, Yubariceras
yubarense, Y. japonicum (see Table 1 for locality

R3013 (N= II) , ObiraR4001 (N=18), Obi ra
R4582 (N=12) , Obi ra
R470Ip(N=11) , ObiraR2672 (N=I7), Obi ra
Hb-IO (N= 8), Haboro
S221Ip(N= 6) , Saku
RI 01 p (N= 6), ObiraR4017 (N= 6), ObiraPM3007(N=14), Manji
MI35 (N=13) , Manji
R6020 (N= I), ObiraR4020 (N= I) , Obira
USGS loc. no.8036(N= I), Montana
Off Suva, Fiji Is.
(N= 9)

records), and nine Nautilus pompilius Linne(captured from the Suva area of FiJ'i', Tanabe ,1985) were used for morphologic comparison.
Specimens of the two scaphitids andN. pompilius
are stored at Kyushu and Kagoshima Universities
respectively. All other specimens are kept atUniversity Museum, University of Tokyo withregistered numbers beginning UMUT.
Methods-Most specimens were cut andpolished along the median plane, and then cut

837. Ammonite Shell Variation and Streamlining
perpendicular along the maximum diameter ofthe protoconch (X-Y plane in Figure 1). The
cross sections were etched with 1% acetic acidfor ten minutes, and acetate peels were preparedby pressing a sheet of triacetylcellulose mm(25 11m in thickness) onto the section flooded
with acetone. Shell diameter, radius vector ofventer, radius vector of umbilicus, whorl h~ight,
whorl breadth and inner whorl height were
measured at intervals of one half whorl on thepeeled cross section using a profile projector(NIKON V16) attached to a digital micrometer(accuracy 111m) (Figure 1). The measurement
data were transferred directly to a personal computer through an interface, and the four geometric parameters developed by Raup (1966, 1967)
and Chamberlain (1976); i.e. the whorl expansion rate (W), the distance of venter from coilingaxis (D), the relative whorl thickness (S), and theflank position (F) were calculated at intervals of
one half whorl for each specimen (Figure 1).
Other important aspects of shell morphology,

MEDIAN SECTION

x

167

such as the "strength" and density of external
SCUlpture (ribs, tubercles and a keel) were notanalyzed quantitatively, but considered in themorphotypic classification.
Morphotypic variation
Although the Cretaceous ammonites examinedvary in coiling, whorl shape, and surface ornament, they possess characteristic features of shellmorphology. They are roughly classified into thefollowing morphotypes: (1) narrowly umblicate
and compressed with fine ribs (Hypophylloceras,
Desmoceras, Tragodesmoceroides, Desmophyllites, Placenticeras) or with fine ribs and aprominent keel (Damesites), (2) moderately
umbilicate platy cone with dense fine ribs (Tetragonites and Gaudryceras), (3) widely umblicate
and compressed with strong ribs, tubercles(Yubariceras) and also with a keel (Subprionocyclus and Reesidites), and (4) planispirally coiled
heteromorph (Scaphites and Otoscaphites). Selected examples of these ammonites are shown in
Figure 2.

CROSS SECTION (HALF)

x

Geometric analysisy

GEOMETRIC PARAMETERS:yw=(b/C)2. D =g/b. S=d/e. F=fla

Figure 1. Basic morphology and measurementsof an ammonite shell in median and cross sections. a,shell diameter; b & c, radius vector of venter; d, whorlheight; e, whorl breadth; g, radius vector of umbilicus;
f, inner whorl height. Based on these measurements,
four geometric parameters, W (whorl expansion rate), D(distance of venter from coiling axis), S (relative whorl
thickness), and F (flank position) were calculated atintervals of half whorl. Read S = eld for S = dIe.

Ontogenetic variation-Ontogenetic changesof geometric parameters were examined in seventeen Cretaceous ammonite species. Changes ofsample means of parameters W, D, Sand F versus
whorl number for each species are shown in
Figures 3- 6 respectively. In every species,
parameter W regularly fluctuates between 1. 5
and 2.5 at intervals of one whorl in the first
three whorls. This is largely due to the abruptchange in allometric growth of whorl radius at
the primary constriction near the end of the first
whorl. After the third whorl most species have W
parameters of about 2.0, but in the scaphitids W
exceeds 3.5 in the loosely coiled adult stage(Figure 3). D parameters of Hypophylloceras
subramosum and most desmoceratids decrease
with age in the first three whorls, and after thethird whorl remain almost constant (ca. 0.1)
(Figure 4). In Neopuzosia ishikawai (Desmocerataceae) D is also small in the second and third

168

Kazushige TANABE and Yasunari SHIGETA

837. Ammonite Shell Variation and Streamliningr Hypophyltoc.,.s ,ubremo.um

13 Desmophylllle. dlphyllolde.

2 retr.ganlts. gl.bTU.
14

J refragonlt •• pOpete"s/s

Neopuzosl. Ishikawa'

15· Subprlonocyc/us bra~lI/slllnus

4 Gaudryce,.s dens.plle.tum
5 Scaphltes pla"us

169

16

Subprlonocyclus nap'unlt\, ,17 Reesldlt.s mlnlmu,

3.5........... ..:,\
ADULT
STAGE

6 Otoseephlls. puercu/us

7 De,moce,.s Japon/cum

8 rragodesmoceroldes sUbeosl.tus
9 Oemsslt.s a/nusnus
10 Dameslt.s damesl

It Damesltes sam/cost.tus

12 Damesltes sugat.

-

3.0

~

W
I-

«

ex::

z

0

2.5

(f)

Z

«

a.

X
W
....J

a:: 2.00I~

o PHYLLOCERATACEAE
6LYTOCERATACEAE

1.5<>SCAPHITACEAEo DESMOCERATACEAEOACANTHOCERATACEAE

1.0

1.5

2

2.5

3

3.5

WHORL NUMBER
Figure 3. Ontogenetic change of the parameter W in relation to whorl number for seventeen ammonite
species. Sample mean at each stage is plotted for every species. The regular fluctuation of W parameters in the
flrst two whorls is due to the abrupt change in growth of whorl diameter at the primary constriction.

+- Figure 2. Wide variation of shell shape and surface ornament observed in selected Cretaceous ammonites.
Lateral (A) and ventral (B) views are shown for each species. For locations see Table 1. lA-B. Yubariceras japonicum Matsumoto, Saito & Fukada (UMUT MM 18213; XO.2). 2A-B. Subprionocyclus bravaisianus (d'Orbigny)(UMUT MM 18209; XO.8). 3A-B. Otoscaphites puerculus (Jimbo) (Kyushu Univ. specimen, GK. H 5753;
X1.6). 4A-B. Gaudryceras denseplicatum (Jimbo) (UMUT MM 18200; XO.3). 5A-B. Damesites semicostatus
Matsumoto (UMUT MM 18205; XO.8). 6A-B. Hypophylloceras subramosum (Spath) (UMUT MM 18197;
XO.8). 7A-B. Placenticeras intercalare Meek (UMUT MM 18214; XO.26).

Kazushige TANABE and Yasunari SHIGETA

170

whorls but then increases abruptly. D parametersof other species are almost constant throughout
growth (ca. 0.3-0.5) and larger than in Hypophylloceras and most desmoceratids at the same
I Hypoph.,lIoc.t.s subnmosum
2

0.6

re,ragonlfes g/abrus

growth stage. Two scaphitids possess extremely
large D parameters in the adult stage. In every
species examined, parameter S tends to decrease
with age (Figure 5). At the same stage, it is
II Oame.sltes sam/cost.,us
12 Dam.slles sugat.

J T.".gonlles poparens/s

IJ Oesmophrllltes dlph'liloides.. Geud''1Ce'8S dens.pllcarum,. NeoPuzosJ. Ishllu,wal

5 SC8phlles planus

15 Subprlonocyclus brett./s/enus

6 Otosceph"es pU.feu/us

16

7 Desmoceras lap on/cum

17 Re.s/dltes m/nlmus

6 ADULT

STAGE

Sub,ulonocyc/us neplunl

8 Tragodesmoceroldes subcost.lus
9 Dames/les.'nuanus

0.5

ADULT
STAGE

(/)

x

« 0.4

(!)

Z
...J

o

()

~

o

0.3

0:

u.

0:
W
I-

Z
W

>

0.2

U.

o

w
()

z

«

l-

(/)
C

0.1

o PHYLLOCERATACEAE~LYTOCERATACEAEOSCAPHITACEAEoo

DESMOCERATACEAE
ACANTHOCERATACEAE

D~~--~----~--~----~--~----~4-----L----5~

1.5

2
2.5
3
3.5
WHORL NUMBER

4.5

Figure 4. Ontogenetic change of the parameter D in relation to whorl number forseventeen ammonite species. Sample mean at each stage is plotted for every species. In thethird to fIfth whorls, D parameters of the Phyllocerataceae and most Desmocerataceae aremuch smaller than those of other superfamilies.

837. Ammonite Shell Variation and Streamlining

smallest in the species of the Phyllocerataceae
and the Acanthocerataceae, intermediate in the
Desmocerataceae, and largest in the Lytocerataceae and the Scaphitaceae. Ontogenetic changeof parameter F also varies greatly among the
2.0

1 H'IPophyllocer.s .ubramosum

11 Oame./r •• • em/co.,.tu.

12 Dameslte. luga'.

r.,r.gonlta. pope'ens/s

13 Oesmophyillt •• dlphyllo/de.

4 Geudryce,e. dens.pllcarum

14 Neopuzosl. Ishlkawal

5 Seep"".s planus
6 Oro.cepll,r •• puerculu.

16

Subprlonocyclus fte."tunlmoc.,., lapon/cum

17

R.e.'dUes mlnlmu.

7 O ••

1.8

species examined (Figure 6). It increases rapidly
with age in Hypophylloceras or slowly in Tetragonites, Gaudryceras and Reesidites. F parametersof most desmoceratids are relatively large (ca.
0.30) and remain almost constant during onto-

2 ru,.gonlte. glabrus
3

1.9

15 subprlonocycJus br.".'s/anus

8 Tragode.mocerolde. subcos,.tus
9 Dame.It..

./nuenu.

10 Demeslt.s demesl

1.7

1.6
1.5

1.4
(J)
(J)

UJ

Z

1.3

~

()

I

12

I...J

a:

o

1.1

I

3:

1.0

UJ

>

l-

0.9

e:(

...J
UJ

a:

O)HYLLOCERATACEAE

0.8

6.L YTOCERAT ACEAEOSCAPHITACEAE

0.7
0.6

171

()OESMOCERATACEAEo

ACANTHOCERATACEAE·

O.5L-J---~1.~5----2~--~2~.5----~3--~3~.5~--~4--~4~.5~--~5~
WHORL NUMBER
Figure s. Ontogenetic change of the parameter S in relation to whorl
number for seventeen ammonite species. Sample mean at each stage is plottedfor every species. In every species S decreases with age, but the interspecificvariation at the same whorl stage is fairly large.

Kazushige TANABE and Yasunari SHIGETA

172

geny. The only exception is Neopuzosia ishikawaiwith F gradually decreasing.
Intra- and interspecific variation-Shell shapevariation in the species examined is summarized

0.45

2

r.'r.von"as {l1.btus

in two sets of S-D and W-F diagrams at different
growth stages (Figures 7-8). In every species,
intraspecific variation of geometric parameters
is larger in the early stage than in the later stage.

7 Oe5moc.,eS lap on/cum

15 Subprlonocyclus br.".'s'.nus

8 rragodesmoc.f'olde. subcost.tus 16 Subpr/onocyc/cJ$ ne,,'u"'

3 Tetr.VonUes poperens/s

9 Oemeslle. .Inuenus

10 Oames't •• demesl
II Oameslte. semlcos'.'us

0.40
0.35

OPHYLLOCERATACEAE

12 Oam.,"a, ,.ge,e

LJ.LYTOCERATACEAE

13 O.,mophyll"., dlphylloldu

OSCAPHITACEAEo DESMOCERATACEAEo

ACANTHOCERA TACEAE

0.30.......
lJ..

z

o
t-

~ 0.25
a..

~

z

~

....J 0.20
lJ..

0.15

0.10 '---'---_--L_ _L-_...L-_--L_ _L - _ - - L _ - - ' -_ _..l.4
5
4.5
2
2.5
3
3.5
1.5

WHORL NUMBER
Figure 6. Ontogenetic change of the parameter F in relation to whorl number forseventeen ammonite species. Sample mean at each stage is plotted for every species. Wideinterspecific variation can be observed among the species examined at the same whorl stage.

837. Ammonite Shell Variation and Streamlining
I Hrpophrlloce,e. subremosumo PHYllOCEAAYACeAe
0,5173
11 Dam."' •• •• mlcost.,us

2 Te"8gon"8. gl.btus

t i l YTOCERATA.CEAE

3 Terrago,," •• poperens's

13 Desmopll,,,,, . . dlphrllo'duo

4 Geudlre., •• dens.pllce'um'4 Neopuzo.'. ,.h'leew8'

SCAPHIT ACEAE

o oeSMOCERATACEAE

5a

6 arose_phU •• puefculus

16 Subprlonocrc/"s naptunlo

7 D •• moee,•• laponlCl/m

17 R••• ldlt •• mlnlmus

en

B Tregodasmocerold •• subcosr.,us

ACANTHOCERA T ACEAE

15 $ubP,'onoc,cI"s br.".'.'anus

SeephU •• pl.trus

XO.'

«

Cl

z

..J

o
o

u.

::; 0,3

o

0,'

Z

a:

u.

a:

IU

....

I--

0

I--

0
"-

Z

....
en

w 0.7

0,3

>

u.

o

'"
«

IU

u.

Z

"

..J

o
Z
«
.... 0,1
en
Ci

0,2

°07'5-----!---~I:';,5---~;-------:2:':,5-0~'~5----~-------~I,~'5-----~--------2~,'5

RELATIVE WHORL THICKNESS (S)WHORL EXPANSION RATE (W)

Figure 7. Variation of the geometric parameters at the end of the lust whorl in seventeen ammonite
species. Sample mean and two standard deviations (horizontal and vertical lines) are indicated for each species.
The two figures indicate similarity in juvenile shell morphology among the Cretaceous ammonites.

The species examined do not show significant
differences in juvenile shell morphology (Figure7). In contrast, they show a large interspecificvariation in the later growth stage (Figure 8).
The coefficients of variation of parameters Sand
D at the fourth whorl stage are usually largest in
the Acanthocerataceae and Scaphitaceae, intermediate in the Lytocerataceae, and smallest in
the Phyllocerataceae and Desmocerataceae, atleast for the samples examined (Table 2). Geometric parameters of adult Placenticeras intercalare and Hypophylloceras subramosum arevery similar to those of Nautilus pompilius(Figure 8).
Discussion
This study demonstrates that the shells of
Cretaceous ammonite species examined differ
in coiling at all ontogenetic stages. Coefficientsof variation of parameters at a given growthstage also vary greatly among these species (Table2). Interspecific difference in the sample mean isespecially conspicuous for parameters S, D and
F. Based on these observations we consider themorphologic adaptations of the high variation inshell geometry. Truly remarkable intraspecificvariability has been recognized in many nearshore-type Acanthocerataceae and Hoplitaceae,
such as in species of Acanthoceras (Kennedy andHancock, 1970), Collignoniceras (Kennedy et al.,1980), Pseudotissotia and Wrightoceras (Hirano,1983), and Neogastroplites (Reeside and Cobban,1960). In contrast, shell shape variation is muchsmaller in the offshore-type ammonites investigated such as Gaudryceras (Hirano, 1975, 1978)
and Tetragonites (Y. Shigeta's unpublished data).
Two major adaptive strategies have been con~sidered for the function of ammonite external
shell morphology: (l) protective (defensive) inthick-shelled whorls with spines or prominentribs preventing shell breakage by predators

Kazushige TANABE and Yasunari SHIGETA

174

t Hypophrlloce,.s .ubramo.um

6 oro.cap/dt •• puereulus

2 T.rragonlta. ,,'abrus

7 D•• mocer •• /aponlcum

11 Dama,lt •• sem/co,'.'u.
'2 Oameslr.s sug.,.

3 TerragonUe. poparansls

8 Tregoda,moc.rold •• subcost.rus 13 D•• moph''''t •• dlphyllolda.

4 Geud,yce,a. dans.plle.fum

9 Dam ••', • • • Inuanu.

5 Seaph" •• pl• ."us10 Oameslte. dame.1

14 Neopuzos/.

15 Subprlonocyclus bra".','anu,

0.5

D.S

0'

D.~

c(

+

(!)

Z
...J

o

o

::;

0.3

o

a:
u.

!r-

u::

rr-

0

z

I~

w

Yub.,/cer •• 'apon/cum

20

PI.centlcer••21

Nautilus pomplllu,,",.,e.'.,.

,I

0---- -Ii·I"

0..

Z
W

'<:

~

0.2

>
u.

o

w

o
z

~

0.3

<Il

I-

Yuber/e., •• yuba,en ••

+
I

I-

a:

18
19

~+

a
x

,,"'lrawa'

16 Subprlonocyclu. neptunl

17 R•• "dlt •• mlnlmu.

>0:1

0.1

<Il

T

a

o .______ L_
o

D.S

1
ti\l
l!L!

_ _ _ _- ' -_ _ _ _ _

D. 2

...J
U.

1

--+-

D. 1

0

PItYllOCERATACEAE

I::;

lYTOCERATACEAE

0

SCAPHITACEAEo DESMDCERATACEAE
0 ACANTHOCERATACEAE)":. HOPlITACEAE~IL---

1.5

RELATIVE WHORL THICKNESS (S)

o
1.5

2.5

3.5

WHORL EXPANSION RATE (W)

Figure 8. Variation of the geometric parameters at the middle of the fifth whorl in seventeen ammonite
species. Data of adult shells of three ammonite species (nos. 18-20) and Nautilus pompilius are also indicatedfor comparison. Sample mean and two standard deviations (horizontal and vertical lines) are indicated for eachspecies. Intraspecific variation of parameters S and D is especially small in the Phyllocerataceae and the Desmocerataceae. Hypophylloceras (no. 1), Placenticeras (no. 20) and modern Nautilus (no. 21) possess similargeometric parameters.

(Westermann, 1971; Ward, 1980) and (2) hydromechanical for increasing swimming ability(Chamberlain, 1976, 1981; Chamberlain andWestermann, 1976). These two strategies arelargely exclusive because hydromecanica1 efficiency decreases as the external ornament becomes more prominent (Kummel and Lloyd,
1955; Chamberlain and Westermann, 1976;
Chamberlain, 1981). Quantitative analysis of therelations between shell geometry and drag coefficients in the ectocochiliate cephalopod shells
has been done by Chamberlain (1976, 1981). He

used cephalopod scale models with round-whorl
sections (S = 1) and smooth surfaces, and measured drag coefficients acting on the shells at
various water velocities. For aquatic animals thedrag force acting on a swimming body can beapproximated by the following equation.

where D F is drag force, p is fluid density, V isswimming velocity, A is equivalent to a body size
(shell size in this case), and CD is the drag coef-

175

837. Ammonite Shell Variation and Streamlining

Table 2. Coefficients of variation of the geometric parameters at the middle of ruth whorl in the seventeen ammonites
and Nautilus pompilius.

Species

Geometric parameters
W

S

D

F

4.79

5.00

7.44

5,19

5.04
4.48
1.53

4.17
5.00
3.73

7.10
7.37
7.33

6.17
5.13
5.98

15.34
8.03

8.18
4.31

15.59
9.88

12.45
10.14

Desmoceras japonicum
Tragodesmoceroides subcostatus
Damesites ainuanus
Damesites damesi
Damesites semicostatus
Damesites sugata
Desmophyllites diphylloides
Neopuzosia ishikawai

4.57
6.20
4.18
9.36
5.73
7.53
3.65
3.36

2.45
3.05
5.98
3,.57
3.37
6.95
3.12
5.42

8.21
7.76
8.67
5.72
7.18
7.62
4.38
9.99

9.89
8.68
8.45
4.28
7.55
3.33
5.94
6.60

Subprionocyclus bravaisianus
Subprionocyclus neptuni
Reesidites minimus

13.66
9.56
7.97

23.40
13.85
12.31

8.33
8.68
7.12

8.78
10.85
11. 58

Nautilus pompilius

4.01

3.87

18.62*

6.91

Phyllocerataceae
Hypophylloceras

subramosu~

Lytocerataceae
Tetragonites glabrus
Tetragonites popetensis
Gaudryceras denseplicatum

Scaphitaceae
Scaphites planus
Otoscaphites puerculus

Desmocerataceae

Acanthocerataceae

Nautilaceae* Umblicus is covered by callus.
ficient (Chamberlain, 1976). If we consider thatthe fluid density of seawater and shell size areconstant, the above equation is rewritten as
follows.

Assuming that DF is constant, V increases as CD
decreases. Thus, CD is an index of a shell'shydrodynamic efficiency (Chamberlain, 1976).
Chamberlain (1976, 1981) has demonstrated
experimentally that at the same shell size CDvaries greatly with geometry. CD decreases as
either W, D or S decrease. S causes the mostpronounced changes in CD, and the degree ofshell compression should be a key factor incephalopod adaptive design. The effect of F on
CD was not demonstrated, but Chamberlain(1980) suggested that within a suite of low S
shells, lower drag coefficients will occur when W
and D are low, and F is high.
Hydromechanically efficient cephalopod shells
are high-shouldered, involute shells (Chamberlain,1981). Our adult shells of Hypophylloceras subramosum (W = 2.8, S = 0.6, D = 0.1, F = 0.4;
Figures 2-6A-B) and Placenticeras intercalare (W= 2.7, S =O.S,D =0.1, F =0.5; Figures 2-7 A-B)
are closely allied to this morphotype. The shell
shape rather resembles that of N. pompilius,
whose drag coefficient (in 30° attitude) is 0.48
(Chamberlain, 1976), and a similar or smaller
drag coefficient is indicated for the adult stage.

176

Kazushige TANABE and Yasunari SHIGETA

Seven desmoceratines also have relatively low D
and high F, but their S parameters are large (ca.
1.0), at least for the fourth and fifth whorls.
In the adult stage (six whorls; 100 mm shell
diameter) the whorls of Damesites semicostatus
are narrowly umblicate and strongly compressed(low S) with a prominent keel (see Figures
2-SA-B). This implies that the shell of thisspecies tends to be well streamlined. Shells of thethree lytocerataceans (Figures 2-4A-B) may
be compared with the model no. 26 of Chamberlain (1976, table 1). The shells of the threecollignoniceratids, Subprionocyclus bravaisianus,
S. neptuni and Reesidites minimus, are fairly
compressed (S = 0.6-0.7 at fourth to fifth
whorls), but D is large. These Turonian collignoniceratids are very closely interrelated, andpossibly belong to a single clade (Matsumoto,
1965; Reyment, 1975, 1982;Obataetal., 1979).
The oldest species, the middle Turonian Subprionocyclus bravaisianus (Figures 2-2A-B), haslarger D and S than the latest, the late Turonian
R. minimus. The middle to late Turonian S.
neptuni has intermediate values. In correspondence to this, surface ornament (tubercles andribs) tends to weaken from S. bravaisianus to
R. minimus. As Obata et al. (1979) have briefly
mentioned, these trends of shell form and ornamentation can be interpreted as adaptation toincreasing hydromechanical efficiency. Two
species of Yubariceras possess robust depressedshells, with a pair of five rows of tubercles(Figures 2-lA-B). The large S (ca. 1.1) and small
F (ca. 0.2) parameters and the coarse ornamentation suggest that both species were poor swimmers. The coiling parameters in the immature
stage of scaphitids are similar to those of normally coiled species, but possess extremely large
parameters W (ca. 4.0) and D (ca. O.S) at maturity (Figures 2-3A-B). Their shell type corresponds to Chamberlain's (1976, Table 1) model
no. 29, whose drag coefficient is 0.81. Theselines of evidence suggest that the scaphitids
changed their way of life dUring ontogeny. In
all probability, they abandoned an active modeof life at maturity (Tanabe, 1977).
In conclusion, the results of this study indi-cate a wide variety of hydromechanical adaptations among Cretaceous ammonites confirming
the conclusion of previous authors (e.g. Raupand Chamberlain, 1967; Ward, 1980, 1983;
Chamberlain, 1981; Saunders and Swan, 1984)
based on WeD analysis of many ammonites andnautiloids. According to Chamberlain's WeD
contour maps (1981, figs. 18-19), the range ofthe morphologic variation of the Ammonoidea
is much wider than that of the Nautiloidea.
Furthermore, the range of geometric variation in
the Mesozoic Ammonoidea is wider than in the
Paleozoic, and the main adaptive peak shifts
larger D values. In our material, the Wand D
values of the seven desmoceratines, Hypophylloceras subramosum, and the well-streamlined
Placenticeras intercalare all plot near the adaptive
peaks of the post-Jurassic Nautilida and the
Paleozoic Ammonoidea in the diagrams of
Chamberlain (1981, figs. 18-19). Wand D dataof the other species resemble those of the common Jurassic-Cretaceous ammonites (Ward, 1980,
figs. 3-4; Chamberlain, 1981, fig. 19). Coarsely
ornamented planispiral ammonites with robust
ribs, spines and tubercles became very common
in the early Cretaceous, and during the middle tolate Cretaceous the number of heteromorph andstrongly ornate species comprised more than SO%
of the total species (Ward, 1981, 1983, 1986).
Most of these morphotypes had larger D and S
parameters than streamlined shells (Figure 2;
Ward, 1980). Ward (1981) speculated that theincrease of coarsely ornamented species in the
Cretaceous was a defensive adaptation againstshell-crushing predators. In the Upper Cretaceousof Hokkaido, occurrences of coarsely ornatedammonites such as acanthoceratids and collignoniceratids are restricted to the nearshore,coarse-grained lithofacies (Tanabe, 1979). Complete preservation of the aperture and clusteredoccurrences at a single locality supports the autochthonous origin of these fossil assemblages(Tanabe et al., 1978; Tanabe, 1979). This supports the predation interpretation. We believethat most heavily ornamented ammonites werepoor swimmers, and that their possible mode oflife was mobile benthic or nektobenthic. Con-

837. Ammonite Shell Variation and Streamlining
cerning the paleoecology of heteromorphs,
opinions remain divided; some believe that they
were planktonic (Trueman, 1941; Ward, 1976,
1979; Ward and Westermann, 1977), other thatthey were benthic (Scott, 1940; Ziegler, 1967;
Tanabe et al., 1981). The former interpretation
is based mainly on the hydrostatic properties ofthe shells, and the latter on field occurrence. The
mode of coilings and ornamentation in the
Cretaceous heteromorphs are, however, quite
variable, and a single mode of life may not haveapplied to all groups. Heteromorphs with weakly
ornamented and straight shells (e.g. Baculites)
probably could swim, while the presence of different coiling modes during ontogeny in somenostoceratids (e.g. Eubostrychoceras and Madagascarites) suggest the loss of swimming ability,
even if they were neutrally buoyant (personalcommunication with T. Okamoto). Further dataon comparative morphology, anatomy and fieldoccurrence are needed to clarify the above problem.
Acknowledgments
We thank John Chamberlain Jr. and Bruce
Saunders for critical reading of the first draft,Peter Ward, Gerd Westermann and Roger Herwitt
for helpful discussions. We also appreciate Shozo
Hayasaka and James Welch for providing shellsof Nautilus and Placenticeras for this study. This
work was supported by a Grant-in-Aid for
Scientific Research from the Japanese Government (no. 61480028 in 1986-1987).
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177

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Kennedy, W. J. and Hancock, J. M. (1970): Ammonitesof the genus Acanthoceras from the Cenomanianof Rouen, France. Palaeontology, vol. 13, p. 462490, pIs. 88-97.
- - , Wright, C. W. and Hancock, J. M. (1980): Collignoniceratid ammonites from the Mid-Turonian ofEngland and northern France. Ibid., vol. 23,
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Kullmann, J. and Kant, J. (1970): Wachstums-Xnderungen in der Ontogenese palaozoischer Ammonoideen.
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- - and - - (1972): Absolutes und relatives Wachstum bei Ammonoideen. Ibid., vol. 5, p. 129-146.
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--(1965): A monograph of the Collignoniceratidae
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178

Kazushige TANABE and Yasunari SHIGETA

logy, vol. 16, p. 623-636.
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--(1979): Palaeoecological analysis of ammonoid
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- - (1985): Record of trapping experiment. p. 10-17.
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the habitat of Nautilus pompilius in the environs ofViti Lebu, Fiji. Kagoshima Univ. Res. Center for S.
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- - , Hirano, H., Matsumoto, T. and Miyata, Y. (1977):
Stratigraphy of the Upper Cretaceous deposits in
the Obira area, northwestern Hokkaido. Sci. Rep.
Dept. Geol. Kyushu Univ., vol. 12, p. 181-202(in Japanese with English abstract).
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the Manji area, central Hokkaido. Bull. Natn. Sci.
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S., no. 124, p. 215-234, pIs. 35-38.
Trueman, A. E. (1941): The ammonite body-chamber,with special reference to the buoyancy and modeof life of the living ammonites. Q. J. Geol. Soc.
Lond., vol. 96, p. 339-383.
Ward, P. D. (1976): Upper Cretaceous ammonites(Santonian-Campanian) from Orcas Island, Washington. J. Paleont., vol. 22, p. 609-630, pI. 1.
--(1979): Functional morphology of Cretaceous
helically-coiled ammonite shells. Paleobiology, vol.
5, p. 415-422.
--(1980): Comparative shell shape distributions inJurassic-Cretaceous ammonites and JurassicTertiary nautiloids. Ibid., vol. 6, p. 32-43.
- - (1981): Shell sculpture as a defensive adaptation inammonoids. Ibid., vol. 7, p. 96-100.
--(1983): The extinction of the ammonites. Sci.
Amer., vol. 249, p. 136-147.
--(1986): Cretaceous ammonite shell shapes. Malacologia, vol. 27, p. 3-28.
- - and Westermann, G. E. G. (1977): First occurrence,systematics, and functional morphology of
Nipponites (Cretaceous Lytoceratina) from theAmericas. J. Paleont., vol. 51, p. 367-372, pI. 3.
Westermann, G. E. G. (1966): Covariation and taxonomy of the Jurassic ammonite Sonninia adicra(Waagen). N. Jb. Geol. Paliiont. Abh., vol. 4, p.
389-412.
--(1971): Form, structure and function of shell andsiphuncle in coiled Mesozoic ammonoids. Life Sci.
Contr., Royal Ontario Mus., no. 78, p. 1-39.
Ziegler, B. (1967): Ammoniten-Okologie am Beispiel
des Oberjura. Geol. Rundschau, vol. 56, p. 439464.

837. Ammonite Shell Variation and Streamlining

B!IE*c 7 :/ -'f: T l' r ~~O)pJ(;~~;:ff? m1:ifj~t~ t i:itE~)l'};* : ~tW)gP.10)13tWl B!IE*c 7:/ -'f: T l'r 17~0).['llfJ*~ ffl~'-C, RlI:~~;:ff? m1:ifj/~ ';7.>1 - 31 O)~ft ~ J;tf,l~W Lt-::o ~~-;j Lt-::/~ '7.>1-311';1:, Raup~;:J:-?-Cmp~~ht-::~:\ij)Mi*(W), ~:\i~~* (D), ~:\iO)i\1Ii~~;:M-tG$i0)J;t (S), fJI~iIiiO);ffiMB%rli: (F) 0)4"?"('~Go ::'hi?O)?t:>, D, S:loJ:rfFli, XlJJtIl~;:li~
rl3,-e*~tJ:~'iJ~, RlI::llH;:ff-?-C*~ <~tJ:G J:? ~;:tJ:Go RlI:~JtIl~;:li, ~iIii~Uf!iO)z U'7 -1 p-!! '7 /'~f4~T /, -'f: -!! '7 /'~f40)~-eli S ~ nli/j' ~ <, iJ>"?.f:h i? O)~P'J~~:I: t Ij' ~ ~ '0 ~~;:, ~iIii\lUf!i0)~U'7 t;:/ r -!!'7/'~f4~~-m-~0)/,t;7 -1 T/'f4O)~"('li, S, Dli*~ <,.:thi?O)~P'J~~:l:li*~~'o tt*O)lmf4i:~~O)*6*"('li, S, Dlilm~3l1J*~;:*~ <~-3:- L, .f:hi?O)lj' ~ ~,:ljZm~O)Mli/j, ~ ~ 'mt.Jfifi~~~"?::' c iJ~:hiJ>-? -C~ 'Go -h5SiHilj~JliHi, lm~
3l1J*~;:li "? l' T /,"(. tlm11t~~;:M-t GIiOmI t L -c)l'};*(t-J"(' ~ -? t-:: t:;,lf;:t i? h Go tJJ: 0)::' t iJ'i?, B!lEe7:/-'f:T1'rMK.~i?hGm1:ifjO)*~~~~~,~.~~~.~tM$Lk~$ifj~~&:I!!k: L -C~'G tJt~~hGo.fjjJJ$-RlI: . ~ffimRll:

179

Trans. Proc. Palaeont. Soc. Japan, N. S., No. 147, pp. 180-194,12 Figs., October 30,1987

838. LIFE HABIT AND RELATIVE GROWm OF
SOME LAQUEID BRACHIOPODS FROM JAPANKAZUYOSHI ENDO
Geological Institute, Faculty of Science, University of Tokyo, Tokyo 113, Japan

Abstract. Japanese Cenozoic laqueid brachiopods generally show two allometric trends.
One is the ontogenetic increase in valve convexity versus valve length, and the other is the
ontogenetic decrease in valve width versus valve length. To examine the causation of thesemorphologic changes, the general morphology, life habit, and allometric relationships of somemetric characters were investigated in the Recent samples of Laqueus rubellus (Sowerby). The
following are three explanations for the relative increase of shell convexity: 1) efficient secretion of shell material, 2) strengthening the shells, and 3) providing larger space for adult gonad.
Among them, the third explanation seems most appropriate at least in L. rubellus, because of adiphasic allometric relationship between valve convexity and valve length: while valve convexity
is positively allometric to valve length in adults, they are isometrically related in juveniles.

hitherto proposed. Raup and Stanley (1978)
suggested that the allometry in E. wattsi may
be size-related, though how size relates to thechange of the shape was not mentioned. McGhee(1980) interpreted the ontogenetic increase invalve convexity in many biconvex brachiopods as
obtaining maximum internal volume by minimum shell surface area. Maximum internal shell
volume is favorable to house intricated lophoph ore , whereas minimum shell surface area isadvantageous because it costs least metabolicenergy to secrete shells.
Here, I propose several explanations for the
allometric changes observed in the living brachiopod, L. rubellus. I suggest that these explanations
may also apply to some cases of allometric
growth in fossil brachiopods.
The following abbreviations are used in thisstudy for the metric characters and the statisticalvalues. L: length of the ventral valve, W: width of
the shell, T: thickness of the articulated valves,
F: diameter of the foramen, Wt: shell weight,
Lm: length of the median septum, S1: surface
area of the lophophore, A: surface area of theshell, V: inner volume of the shell, 0:: regression

Introduction
In many cases, post-Paleozoic brachiopods
have simple elliptical outlines and show allometric growth during ontogeny. Brachiopod shells
often show significant. deviation from ideal
logarithmic spirals (Rudwick, 1959; McGhee,
1980). McGhee (1980) examined 324 generaof four orders of articulate brachiopods, andshowed that well over a half of them changes
their whorl expansion rates during ontogeny.
An overwhelming trend is the relative increaseof valve convexity with growth.
Brachiopods change the form of the commissure during ontogeny as well as their generalshape. For example, Raup and Stanley (1978)
cited relative growth in a Carboniferous brachiopod, Ectochorisites wattsi, which alters the commissure form ontogenetically from the shape thatis wider than long to the shape that is longer thanwide.
Causation of the allometry in the brachiopods
is not decisive, but some interpretations were
Received' July 30, 1987; read January 31, 1987 at
Shizuoka University.

180838. Relative Growth of Laqueid Brachiopods

coefficient, slope of allometry, K: statisticalvalue for discrimination of allometry (Hayami
and Matsukuma, 1971).
General morphology of laqueid species
The articulate superfamily Terebratellacea,
characterized by having long-looped brllchidium,are classified into several families by differentmode of development of the loop. Hatai (1965)
defined Laqueidae, one of the terebratellaceanfamilies, as possessing loops with interconnecting
bands which unite ascending and decending
branches. Laqueidae was redefined by Richardson(1975) as "Loop passing through axial, annular,
and haptoid phases to a bilacunar loop pattern;bilacunar pattern may be the adult loop patternor be followed either by bilateral and laterovertical phases or by trabecular and teloform phases."
Adult morphology of Laqueus rubellus
Figures 1-1-3 show an adult shell of L.
rubellus. Figure 2 shows gross morphology,
measurements, and internal morphology of thedorsal valve of adult L. rubellus. The shell is
so thin (less than 0.5 mm) and translucent except
for the cardinalia that the gonad can be seen
through the shell. The shell is mostly yellowish
red, with deeper tinges at concentric lines. Theintervals of the growth lines become denser near
the margin. An adult L. rubellus has a bilateralbrachidium (Figure 2).
The gonad sticks on the inner surface of both
ventral and dorsal valves, being lapped in membranes. The males and females can be easily distinguished by binocular observation of the
gonads. Two types of texture are observed, one
is the aggregated small particles, the other is alump of smooth appearance. SEM observationof gonads confirms that the former and the latterare of females and males respectively (Figure 3).
The egg is about 70 Ilm in diameter, whereas thehead of the sperm is about 1 Ilm in diameter.
Sexual dimorphism was not observed at least
for the gross morphology and size of the shells.

181

Juvenile morphology of Laqueus rubellus
The juvenile shell is distinguished from theadult shell by the poorly developed gonad andsmaller size. The figured specimen (Figures 1-46, L = 11.95 mm) is certainly juvenile because it
has no gonads.
The shell morphology of the juveniles isdifferent from that of the adults. Lateral sides
and anterior margin in dorsal view are broadly
rounded and forming almost circular outline.
The valves are nearly equally convex, but both
valves are compressed or less convex comparedto that of the adults. Although the absoluteforamen size is smaller than that of the adults,
relative foramen size to the shell length is larger
than that of the adults. The shell is always freshand it is so thin that the lophophore and othersoft parts are seen through from the exterior.
The loop pattern in the specimens of ca.
10 mm in shell length is already bilateral. The
earlier loop development phase, namely bilacunar, is observed in the specimens of 7 mm long.
The still earlier phase, namely haptoid, is observed in the specimens less than 4 mm in length.
The phase in lophophore pattern of the figured
specimen (UMUT RB18186b) is already plectolophous. In the specimens with a bilacunar loop
pattern, the lophophore is plectolophous, while
it is zygolophous in the specimens with a haptoid
loop pattern.
Morphologic features of other species
Eight laqueid species treated here showrather similar biconvex form of smooth shellsurface (Figure 1). Every species, except for
Laqueus blanfordi and L. quadratus, thicken theposterior part of the shell during growth. The
adult individual of L. blanfordi has a pedicle aslong as the length of the shell. However, in Pictothyris picta and P. sp., the pedicle is so short thatin most case the shell is attached directly to thesubstrate. The foramen of Kikaithyris hanzawai
is so minute that the pedicle may have been
atrophied in the adult phase (Table 1).

182

Kazuyoshi ENDO

838. Relative Growth of Laqueid Brachiopods

c

B

A

183

POS TERIOR

Figure 2. Gross morphology , measurements andinternal morphology of the dorsal valve of Laqueus
rubellus. A: dorsal v.iew; B: right lateral view; C: internalview of the dorsal valve showing the bilateral loop andthe configuration of the lophophore (half ommitted).
L: length of the ventral valve; W: width of the ventralor the dorsal valve; T: thickness of the articulated valves;
Lm: length of the median septum ; 1: crura; 2: cruralprocess; 3: median septum; 4: connecting band; S: interconnecting band; 6: transverse band; 7: descending
branch; 8: ascending branch.

Figure 3. SEM photographs of the gonad of L.
rubellus [Sample Rk (104), April 8, 1986]. 1, Ova,
UMUT RB18186c, scale bar indicates 100J,lm ; 2, Sperm ,UMUT RB1 8186d, scale bar indicates 10 J,lm.

Life habit of laqueid species
Ecology of Laqueus rubellus
Hatai (1940) compiled the data on the Recent
brachiopods collected by the cruises of R/VTable 1. Some adult morphologic characters in eight laqueid species examined.

SPECIESSAMPLE

Laqueus rubellus

Jz(L), Rkl. blanfordi

Ot

L. quadratus

Na, Hil. sp.1

Ts (L)

l. sp .2

Sw

Pictothyris picta

Jz(p), Rk(P)P. sp.

Ts(P)Kikaithyris 'hanzawai

Wa

LOOP
PATTERNWEIGH PEDICLE
DOWN•
bilaterallatero vertical

•
•
•
•

MINUTEMAX.
FORAMEN L(mm)medium

29.55

long

28.35

medium21.75

medium

21.45-

21. 10

short

31.75

short

18.40

•• -

•

40.20

~ Figure 1.
Overall shell morphology of eight laqueid brachiopods. (All figures x l , scale bar indicates
1 cm.) 1-3, Laqueus rubel/us (Sowerby), adult specimen, off Jyogashima, Sagami Bay, Sample Rk (82) , UMUT
RB18186 a; 4-6, L. rubel/us, juvenile specimen, off Jyogashima, Sagami Bay, Sample Rk (17), UMUT RB1 8186b;
7-9, L. blanfordi (Dunker), Otsuchi Bay , Sample Ot (2), UMUT RB18188a; 10-12 , L. quadratus Yabe and Hatai,
off Hinomisaki, Kii Channel, Sample Hi, UMUT RB18190a; l3-1S,L. sp. 1, off Tsukumi, Bungo Channel, Sample Ts (L), UMUT RB18191a; 16-18, L. sp. 2, Sawane Formation, Sado Island, Sample Sw, UMUT CB18192a;
19-21, Pietothyns pieta (Dillwyn), off Jyogashima, Sagami Bay, Sample Rk (P), UMUT RB18194 a; 22-24, P.
sp., off Tsukumi, Bungo Channel, Sample Ts (P), UMUT RB1819Sa; 2S-27, Kikaithyris hanzawai (Yabe), Wan
Formation, Kikai Island, Sample Wa , UMUT CB18196a.

Kazuyoshi ENDO184

Soyo I. His collections from 81 stations showthat Laqueus rubellus is found from 30 m water
depth to depths in excess of 499 meters. Most
specimens were collected on sand or gravelbottoms and bottom temperatures range from
2.0°C to 23°C
= 15-20°C). Though Hatai(1940) failed to describe whether the individuals
were living or not, the major habitats of L.
rubellus became clear: sandy or coarser substrata on the continental shelves and the uppermost part of slope under the influence of warm
ocean currents.
Living specimens of L. rubellus and Pictothyris
picta were repeatedly dredged by R/V Rinkaiof the Misaki Marine Biological Station of the
University of Tokyo in various seasons at thedepths of 85-90 m from sandy bottoms near theedge of the continental shelf of eastern Sagami
Bay, about 2 km west of the western end of
Jyogashima-Islet. A total of 780 individuals of
L. rubellus were collected and 35 of P. picta in
17 samples.
Most of the living individuals of L. rubellus
were dredged with the pedicle attached topebbles or shell fragments. Some rock fragments
were incrusted both by individuals of L. rubellus
and P. picta. The diameter of the substrate particles falls in the range of 5-15 mm. During
growth the substrate for these brachiopods becomes relatively small, and it would be insufficient to support the whole shell. In addition, theshell weight shows an allometric increase during
growth mainly due to the thickening of theposterior part of the shell (Figure 4). Therefore,
the adult individuals of L. rubellus from Sagami
Bay must be free-lying on the sea bottom.
Many brachiopods are known to reorient towater currents (LaBarbera, 1977,1978; Richardson, 1981 b). Juvenile form of L. rubellus may
have the ability to reorient to water current because of the relatively stable attachment, while
the adults may not have this ability because of
their relatively small-sized substrates.
The feeding and the excretion of faeces occur
through filtering system of the lophophore(Rudwick, 1970). Adult individuals of L. rubellus
from Sagami Bay were kept in aquaria with continuous circulation of fresh seawater for two

ex

10

_1

A
10

B

N= 21
r =0.996

N = 32a,= 3.154

a,=3.393

r = 0.991......

.....

3

o

3

•

0.1

0.1

0.01 ~"",,"---'-.L..-L--I..-.J'-_ _- - L _ - - , _ - I 0.01 '-----'-----L---4.---L--J..-L-L-_ _ _- ' - _ - - . .
30
4
10
20
30 40
3
20
10

L(mm)

L(mm)

Figure 4. Double logarithmic plots and regression line with the reduced major axis of shell length (L) vs.
shell weight (Wt). A: Kikaithyris hanzawai (Sample Wa); B: Laqueus rubellus [Sample Rk (80)]. Shell section
along the plane of symmetry is also shown in each figure. Scale bar indicates 1 em. This figure shows positive
allometry of Wt to L owing to the differential thickening of the posterior part of the shell.

185

838. Relative Growth of Laqueid Brachiopods
days. All the individuals gaped slightly (the angleof gape is about 5_10°), and fully extend thefilaments of the lophophore, which trembled
weakly. They qUickly closed the valves periodically without any stimulation at intervals of
several minutes, and after a while, they gradually
opened the valves. When touched, they quickly
closed the valves.
To observe the filtering system more in detail,the valves of L. rubellus were separated after
two days' rearing in aquaria. The individuals
were still alive after the separation of two valves.
The observed movement of the filaments wascontrary to expectations. Each filament of thelophophore moved somewhat individually andflexibly, though the movement of one filament
accompanies the movement of the neighboring
filament. The mode of movement resembles the
motion of the tentacles of a sea anemone. The
expected conformation of filaments, that thefilaments fully extended with the tips of themalong the commissure, was also observed, but thisstate did not last for more than one minute.
When stimulated by a needle, all the filaments
were observed to recoil. These unexpectedmotions may be partly due to the separation of
the valves, but it suggests the ability of the filaments to move flexibly. Similar movements ofthe filaments in separated valves in other terebratellacean species were reported by Thayer(1986) who suggested that the movements area mechanism of rejecting nonfood particles.
As listed below, numerous living individualsof L. rubellus were collected in various seasons
from almost same station: (J) May 25 and 26,
1978, (2) October 4 and 5,1979, (3) March 11,
1982, (4) July 27, 1982, (5) Aug. 3, 1983,(6) July 10, 1985, (7) April 8, 1986, and (8)April 28 and 30, 1987.
Every sample includes adult specimens withboth moderately and poorly developed gonads.
There is no seasonality of maximum gonad
development, so the time of reproduction is still
unknown.
Mode of life of other species

Laqueus rubellus possesses a secondarily free-lying life habit. Individuals of Pictothyris picta
from the same stations of Sagami Bar [Sample
Rk (P)] also attached themselves to small unstable particles. Such free-lying mode of life has
not been described in extant articulate brachiopods except for Richardson (1981a). Permanent
attachment to hard stable substrate seems morecommon in extant articulate brachiopods.
Individuals of Pictothyris sp. [Sample Ts (P)]attach themselves to pebbles of moderate size
ranging three to five times as large as the adultshells. This relative size of adhering material
suggests an intermediate mode of life between
free-lYing and permanently attached. Specimensof Laqueus blanfordi (Sample Ot) were collected
in a fishing net with the individuals attached to atangled rope of about 1. 5 cm in diameter. From
this mode of occurrence, an attached life isstrongly suggested for this species, although
the type of substrate may be very different indifferent samples.
Kikaithyris hanzawai (Sample Wa), a PlioPleistocene fossil species from Ryukyu Islands
and Formosa, shows the characteristic shellmorphology suggesting a reclining mode of life.
The shell of K. hanzawai is fairly large. The
dorsal view is shouldered in comparison with L.

Al.rubellus N=Jl

E
E

3

oP.pieta

N=JO• K. hanzawai N = JJ

LL

2

OL---~----~--~----~~

o

10

20

30

40
L(mm)

Figure 5. Scatter plots of FversusL in L. rubellus[Sample Rk (80)), Pictothyris picta [Sample Rk (P)),
and Kikaithyris hanzawai (Sample Wa). The margin of
the foramen of L. rubellus and P. picta is resorbed andthe diameter becomes large with growth. However, in
K. hanzawai, the margin of the foramen is scarcely
resorbed.

Kazuyoshi ENDO

186

rubellus (Figure 1-25). It has a strongly incurved
beak (Figure 1-26) and a foramen which isunusually minute for its large shell (Figure 5,
Figure 1-25). The shell is thin (less than 0.5 mm)except for the thick posterior part of the shell.
The weight of the shell is positively allometric tothe cube of length owing to the differential
thickening of the shell in posterior region (Figure4). These morphologic features indicate a freelying mode of life in this species; the pedicle ofK. hanzawai must have been degenerated withgrowth, because the size of the foramen determines the diameter of the pedicle. Moreover,the incurved beak is unfavorable to hold apedicle because it points to the dorsal valve(Figure 1-26). Judging from the similar outline
to L. rubel/us in the early stage, K. hanzawai
probably changes the mode of life from an attached life habit to a completely free-lying one
without a functioning pedicle during ontogeny.
In modern seas only one species, Neothyris
lentieularis, is certainly free-lYing without
pedicle attachment (Rudwick, 1970; Richardson,
1981a).
Laqueus quadratus (Sample Hi) does notpossess thickening of the posterior part of theshell. In a strong bottom current, a free-lYing
state of such light shells would be unstable anddisadvantageous. Therefore, attached mode oflife is suggested for this species as in L. blanfordi.
Individuals of Laqueus sp.1 [Sample Ts (L)] andLaqueus sp.2 (Sample Sw) thicken their posterior
part of the shells. This character, however, does
not necessarily mean a free-lying mode of life
because the equivocal species Pietothyris sp.
[Sample Ts (P)] exhibits similar features.

Relative growth
The shell form of Laqueus rubellus changes
during ontogeny from a circular outline in dorsal
view to an elongate oval. The shell also becomes
more strongly convex in the adult stage. In orderto quantify this allometric change, bivariate
analyses of Land W as well as Land T were
performed.
The bivariate analysis assumes a simple powerfunction between Land W, and Land T. The
regression line was calculated using the reduced
major axis method (Imbrie, 1956), in which theslope (a) of allometry in a log-log plot (regression
coefficient) is given as:

a=~

Sx '

where Sx and Sy are the standard deviations ofx and y, respectively. The regression coefficientsare tested against the null hypothesis,----s;-

Ho : a = 1, K = a- 1

(Hayami an dMatsukuma, 1971),
where K has a normal distribution, and Sa is
the standard error of the regression coefficient.
Discrimination between isometry and allometry is arbitrarily defined at the confidence
level of 95% (Hay ami and Matsukuma, 1971):
The value of Kover 1.96 means the y-variable
is positively allometric to the x-variable; andnegatively allometric when K < -1.96; if thevalue of K is between 1.96 and -1.96, the null
hypothesis (isometry) cannot be rejected.
Figure 6 shows an example of bivariate
analysis on the L-W relation and the L-T relation.
The reduced major axes on double logarithmic
scatter diagrams indicate that W is negatively
allometric to L, and that T is positively allometric to L.
Figure 7 shows another example of bivariate
analysis on the L-W and L-T relationships. In
this sample, the males and the females are analyzed separately. In both males and females,
W grows significantly negative allometric to L,
and T grows positive allometric to L. The difference of regression coefficients is not significant between the males and the females at 95%
confidence level.
Table 2 lists the results of the average relative
growth analyses of T vs. L and of W vs. L on 8
samples of 7 species. Double logarithmic scatter
diagrams for P. pieta and K. hanzawai are shownin Figure 8 and Figure 9 respectively.
In all species examined, T shows a more orless positive allometry to L. Except for L.

187

838. Relative Growth of Laqueid Brachiopods

BA_ 30 . . - - - - - - - - - - - - - - , _ 3 0 , - - - - - - - - - - - - - - - ,
E
E
3

E
E

N = 32-N = 32
r = 0,989
T = 0.351 L1.120

1-20

r = 0.989

20

W= 1.535 L0.789

.

~

. -'

10

10

............'--'-............------'-----'--..L....J
10
20
30 4!J

2~--'--"""'--

20

10

30

3

L(mm)

L(mm)

Figure 6. Double logarithmic allometric relationship between Land W (A) and between Land T (B) in
L. rubellus [Sample Rk (80)]. Regression line with the reduced major axis is indicated in the this figure.

4!J

A

20

eMALE

E
E

3

30

B
eMALE

N=26
'=0.935«= 0.770

N= 26,= 0.980<1= 1.355

E
E

OFEMALEOFEMALEI-

N= 21,= 0.896'" = 0.825

20

N=21
'=0.931<1=1.317

10

20

30
L(mm)

40

20

30
40
L (mm)

Figure 7. Double logarithmic allometric relationship between Land W (A) and between Land T (B) in
L. rubellus [Sample Rk (13)]. Males and females are separately treated. Regression line with the reduced major
axis is indicated in this figure.

Kazuyoshi ENDO

188

Table 2. Allometric relationship between Land W and between L and T in eight samples of seven species. N:
number of individuals; a: regression coefficient, slope of reduced major axis in the double logarithmic
scatter diagram; (1: standard error of a; r: correlation coefficient; K: statistical value for discriminationof allometry (Hayami and Matsukuma, 1971).

L- W

L - T
(f
r
K
ex
47 0.786 0.043 0.926 - 4.96 1.345 0.049 0.968 7.04

speciessampleLaqueus rubellus

Rk(13)

L. rubellus

Rk(8o) 32 0.789 0.021 0.989 -10.18 1.120 0.030 0.988 4.02

L. blanfordiOt(1,2) 27 1.004 0.014 0.997

L. sp. 1Ts(U46 0.801 0.059 0.864 - 3.34 1.496 0.102 0.887 4.86

L. sp. 2

Sw

44 0.923 0.025 0.984 - 2.87 1.176 0.036 0.979 4.84

Pietothyris pieta

Rk(P)36 0.824 0.033 0.971

P.sp.

Ts(P)

43 0.867 0.024 0.983 - 5.44 1.178 0.033 0.983 5.39

Kikaithyris hanzawaiWa

33 0.940 0.013 0.997 - 7.05 1.091 0.014 0.996 5.51

40

N

OC

r

0-

A

20

E
E

N = 36E
E330

r =0.971

I-K

0.30 1.206 0.015 0.998 13.76- 5.34 1.229 0.047 0.973 4.85

8
N =36

r = 0.973

W= 1.413 L0.B24

T = 0.238 L,·229

I. .

.7

!~

20

/'

10

.

.'

6

20

30

40

Umm)

5

10

20

30

40

Umm)

Figure 8. Double logarithmic allometric relationship between Land W (A) and between Land T (B) in
Pietothyris pieta [Sample Rk (P)). Regression line with the reduced major axis is indicated in this figure.

838. Relative Growth of Laqueid Brachiopods

BA

50~----------------------~

~40
3 30

50~------------------------

"E40

N=33

E

r=0.997

W= 1.095 LO. 940

20/;:: 30/189

20

N = 33r = 0.996..

T = 0.380 LtOB9

/

10

10

•
10

20

40 50

30

Umm)

10

20

30

40 50

l(mm)

Figure 9. Double logarithmic allometric relationship between Land W (A) and between Land T (B) in
Kikaithyris hanzawai (Sample Wa). Regression line with the reduced major axis is indicated in this fIgure.

blanfordi, the slope of allometry for W vs. L is
negatively allometric, and this indicates thedecrease in the ratio WIL with growth.

Interpretation of ontogenetic increase invalve convexity
Raup and Stanley (1978) stated that "ontogenetic change in shape accompanies two othersorts of change; i.e. change in mode of lifeand change in size." The change of shell shapewith the change in mode of life is examined as
the cause of ontogenetic increase in valve convexity. The mode of life in many living articulatebrachiopods has been assumed to be rather
monotonous; except for the larval stage, theypermanently attached to hard substrate, feedingon the suspension matter through the lophophore.
In such an attached species, significant change
in mode of life may not occur. However, someinstances of secondary free-lying mode of life areobserved in modern articulate species by Richardson (1981 a, 1981 b). Free-lYing species sometimes retain attached nature to fragments ofshells and pebbles, all of which are smaller in size
than the animal, as is the case with L. rubellus
from Sagami Bay.
In such free-lying species, the post-larval
juveniles must attach themselves to some objects.
The attached object may become unnecessary as
living animals grow larger. It is at present unclear
how the above change in mode of life relates tc
the change in valve convexity or in commissureform. One possible explanation is hydrodynamic
stability of the shell. Possibly, free-lYing brachiopods are selected for hydrodynamic stability.
Allometric increase in valve weight, as alreadystated, may have a role for this purpose. However, Alexander (1984) finds that hydrodynamic
stability is highest in dorsal-ventrally compressedand concavo-convex species. Thus, allometric
growth in laqueid brachiopods may not be produced by selection for hydrodynamic stability.
Ontogenetic increase in valve convexity wasobserved in alliaqueid species from Japan including both the attached and free-lying species. For
example, L. blanford; attached rope shows positive allometry of T relative to L. The shift fromthe attached to the free-lying does not explain

190

Kazuyoshi ENDO

the change in shell form.
I believe that most allometric growth can be
explained by size increase. McGhee (1980)
assumed that the metabolic requirement of abrachiopod is a function of volume of the soft
tissues and that the capacity of the lophophore
to meet these requirements is a function of its
fIlamental area, as expressed by the relative increase in the surface area of the lophophore.
Therefore, the inner volume of the shell increases
in ontogeny to house the allometrically growing
lophophore. The economics of shell secretion
dictates that a spherical surface is most efficient
to attain the greatest inner volume. Because of
the accretionary growth of two coiling tubes inarticulation, truely spherical form is not attainable. Therefore, brachiopods grow allometricallyto increase shell convexity during ontogeny bydecreasing the whorl expansion rate.
Surface area of the lophophore (81), the innervolume of the shell (V), and the surface area ofthe shell (A) were measured to analyze the areavolume relationship discussed by McGhee (1980).
All measurements were made on the sample Rk(80) of L. rubellus.
The surface area of the lophophore was calculated through the following procedure. The
excised lophophore was cut into pieces andphotographed at fixed magnification. The printed fragments were cut out along the margins,
and the cut pieces of the printing paper were
weighed. Lastly the weight was converted into
the area. The inner volume was estimated byfilling both valves with #800 carborundum andthe weight of the carborundum was converted
into inner volume. The surface area of the shell
was calculated on an assumption that an ellipsoid
approximates the outline of L. nt.bellus.
Because the length of the median septum(Lm, see Figure 2) roughly represents a linear
dimension of the soft tissues and because the soft
tissues occupy the space between the anterior
and posterior edges of the median septum near
the hinge line, these three measurements (81, A,V) were compared to Lm. Lm was measured
under the profIle projector with a digital micrometer.

Table 3 shows the results of regression analyses on the relationship among 81, A, V and
Lm. 81 does not increase as the cube of Lm(O! = 0.748), but it is positively allometric tothe square of Lm at 95% confidence level.
As is expected, the approximate surface area ofthe shell decreases with growth, relative to alinear dimension of the soft tissues (Figure 10).
Since the surface area of the shell is two dimensional, the level of isometry in the relation
between Lm 2 and A is at O! = 1. The actual
growth of A to Lm 2 indicates negative allometry(O! = 0.935). In spite of the ontogenetic change
in the shell form, V increases isometrically
Table 3. Results of bivariate analyses on Sl.
A. VandLm. [SampleRk (80)). For
abbreviations see explanation in
Table 2.

y N ~Lm~SI 32 1.123
Lm3- SI 32 0.748
Lm2- A 32 0.935
Lm 3- V 24 0.986
x

r

0.962
0.962
0.985
0.982

K
2.26
-6.97
-2.27
-0.36

~~---------------------,

40

N=32
r = 0.985

-l)
E

N

.s20
«

10

A=5.250 (Lm2)0935

4

10

200

Figure 10. Double logarithmic allometric relationship between the square of Lm and A in L. rubellus[Sample Rk (80)). Regression line with the reduced
major axis is indicated in this figure.

191

838. Relative Growth of Laqueid Brachiopods

relative to Lm 3 • The plot of Lm 3 against V
shows a regression coefficient of 0.986 andindicates near isometry.
The results obtained seem to consistent withthe hypothesis of McG!lee (1980) as a whole.
The surface area of the lophophore ontogenetically increases over the square of the length,
while the surface area of the shell ontogenetically decreases below it. However, contrary to
expectations, the surface area of the lophophore
does not increase as much as the cube of thelength of the body. The inner volume of theshell increases nearly isometrically versus the
cube of the length of the soft part. These facts
indicate that the capacity to meet the metabolic
requirement may not be a function of the filamental area of the lophophore, but a functionof the inner volume of the shell, which thelophophore effectively occupies.
Another possible size-related explanation isthat brachiopods become more convex to increase mechanical strength of the valves. The
test of adult laqueid brachiopods is thin except
for the cardinalial (posterior) part. The test
thickness does not increase as the shell grows.
This indicates the gradual decrease of the relative
strength of the shell with growth, and, therefore,
the reinforcement by shell form is considered tobe required. The predator of the brachiopods is
unknown, but non-fatal injuries in some specimens of L. rubellus from Sagami Bay suggest
crabs are possible predators. The inflated form
may be advantageous for avoiding shell crushingcrabs.
The highly allometric growth of brachiopod·
valve inflation may also be explained by enlargement of the gonad during growth. As to L.
rubellus, the gonad develops in the individuals
whose shell length is larger than about 15 mm(the smallest adult individual ever measured is14.75 mm and the largest juvenile is 21.30 mm
in shell length). The weight of the gonad in an
adult individual of L. rubellus attains more than
25% of the whole soft tissue weight (Table 4).
In order to test this hypothesis, the allometric
growth of gonad vs. shell size in juveniles andthe adults of L. rubellus was analyzed separately

Table 4. Dried weight of each soft tissue in three specimens of L. rubellus [Sample Rk (100)).

-----

SPl:CIMENBODY PARTS

WT.

%

WT.

11.94 25.9 16.68

33.1

13.50 30.2

MANTlE & PERIOSTRACUM

9.11 19.8 14.08

28.0

8.19

PEDICLE & MUSClE

10.08 21.9

8.17

16.2 11.64 26.0

DIGESTIVE SYSTEM

7.03 15.3

3.89

7.7

3.40

LOPHOPHORE

7.87

17.1

7.53

15.0

7.97 17.8

TOTAL

46.03 100.0 50.35 100.0 44.70 99.9

GONAD

WT.

3

2

1
%

%

18.3
7.6

x10-3 gusing specimens in the three samples Rk (13),
Rk (17), and Rk (80).
Figure ll-A indicates that T and L are positively allometric in adults, but are isometricallyrelated in juveniles. The regression coefficient of
the adults is 1.342, the K-value against the null
hypothesis of O! = 1 is 11.29. On the other hand,in the juveniles the regression coefficient value is0.987 (K = -0.53).
The K-value against the null hypothesis ofhomogeneity of regression coefficients between
juveniles and the adults is -9.09. The regression
coefficients between mature and immaturesamples are different at the 95% level, and therelationship between Land T is considered to bediphasic allometry. T increases isometrically to
L during the early growth stage, and T increases
positively allometric ally to L after initiation of
gonad development. The co-ordinates of theturning (or "critical") point are calculated as
L = 17.9 and T = 8.3 in mm. The close agreement
between these measurements and the size at
which gonad development begins strongly supports my suggestion that shell convexity increases to house the enlarged gonad. As to the
L-W relation, no significant difference in regression coefficient between the juvenile and theadult was detected (Figure II-B).

Conclusion
A common allometric trend is detected among
examined laqueid brachiopods. The trend is two-

192

Kazuyoshi ENDO

A

B

30

30
L.. rub.lluB

L. rubellus

o juvenUe

20

20

=

N
21
r = 0.1193

E• adultE=128
r =0.1167

E
~

E

N

~

10

10
o juvenile
N

= 21
=

r
0.989
• adultN=128

r = 0.928

3~~~~~--------~--~--~~

5

10

20

30

40 50

L(mm)

5

10

20

30

40 50

L(mm)

Figure 11. "Diphasic allometry" in the relationship between L and T (A), and "monophasic allometry"in the relationship between Land W (B). Sample Rk (13, 17,80) of L. rubellus.

fold; one is relative increase of valve convexity to
the length of the shell (L-T relation), and theother is relative decrease of valve width to thelength of the shell (L- W relation).
Four different explanations may be possible
about the L-T relation:(1) to obtain hydrodynamic stability in thefree-lying stage of life,(2) to economize the secretion of shellmaterial,(3) to strengthen valves, and(4) to host the well developed gonad.
Of these explanations, (1) is invalid because
it does not explain the allometry in some permanently attached species, and because compressed shells are inferred to be more stable to
the water current. Among the remaining three
explanations, (4) is most convincing at least in
the case of L. rubellus because of the apparent"diphasic" allometric relation between Land
T. No plaUSible explanation for the L-W relationis still obtained. It requires a further study.

Acknowledgements
I would like to thank Prof. I. Hayami (University of Tokyo), Associate Prof. K. Tanabe(University of Tokyo) and Mr. R. Norris (Harvard
University) for many helpful suggestions during
the course of this study, and for critical readingof the manuscript. I am grateful to AssociateProf. S. Ohta [Ocean Research Institute (O.R.I.),
University of Tokyo] for allowing me to join in
the sampling cruise by R/V Yayoi and for providing the samples stored in O.R.I. I wish to
thank the staff of the Misaki Marine Biological
Station, University of Tokyo, for affording me
an opportunity to collect and observe the living
specimens of L. rubellus. I am much indebted to
Mr. E. Tsuchida (O.R.I.), Dr. T. Oji (Universityof Tokyo), and Dr. Y. Kondo (University of
Kyoto) for providing the samples. Many thanks
are due to the staff members and graduate
students of the Paleobiological Laboratory of
the University of Tokyo for valuable discussions.

838. Relative Growth of Laqueid Brachiopods
References
Alexander, R. R. 1984. Comparative hydrodynamic
stability of brachiopod shells on current-scoured
arenaceous substrates. Lethaia, 17, 17-32.
Endo, K. 1986. Mode of occurrence and significance of
the warm-water fauna in the Sawane Formation,
Sado Island. Jour. Geol. Soc. Japan, 92 (1),77-80.
(in Japanese)
Hatai, K. 1940. The Cenozoic Brachiopoda from Japan.
Sci. Rep. Tohoku Imp. Univ., 2nd Ser., 20, 1-413,
pIs. 1-12.
--1965. Cenozoic Terebratellacea. In, Moore, R. C.
ed., Treatise on Invertebrate Paleontology, Part H.
Geo!. Soc. America and Univ. Kansas Press, 845p.
Hayami, I. and Matsukuma, A. 1971. Mensuration offossils and statistics - Analysis of allometry andvariation-. Sci. Rep. Kyushu Univ., (Geol.), 10 (3),135-160. (in Japanese)
Imbrie, J. 1956. Biometrical methods in the study of
invertebrate fossils. Bull. A mer. Mu~. Nat. H{st.,108 (2),211-252.
LaBarbera, M. 1977. Brachiopod orientation to water
movement 1. Theory, laboratory behavior, andfield reorientations. Paleobiology, 3, 270 -28 7.
--1978. Brachiopod orientation to water movement
functional morphology. Lethaia, 11, 67 -79.
McGhee, G. R., Jr. 1980. Shell form in the biconvex
articulate Brachiopoda: a geometric analysis.
Paleobiology, 6 (1),57-76.
Raup, D. M. and Stanley, S. M. 1978. Principles of
paleontology, 2nd ed. 481p. W. H. Freeman andCompany, San Francisco.
Richardson, J. R. 1975. Loop development and theclassification of Terebratellacean brachiopods.
Palaeontology, 18,285-314, p!. 44.
--1981a. Brachiopods in mud; resolution of adilemma. Science, 211 (4487), 1161-1163.
--1981b. Brachiopods and pedic1es. Paleobiology, 7(1),87-95.
Rudwick, M. J. S. 1959. The growth and form of brachiopod shells. Geol. Mag., 96, 1-24.
--1970. Living and fossil brachiopods. 199 p. Hutchinson Univ. Library, London.
Thayer, C. W. 1986. Are brachiopods better than bivalves? Mechanisms of turbidity tolerance andtheir interaction with feeding in articulates. Paleo·
biology, 12 (2), 161-174.
Tokuhashi, S. and Endo, H. 1984. Geology of theAnesaki District. Quadrangle Series, scale 1:50,000,
130 p. Geo!. Surv. Japan. (in Japanese)
Appendix
The following samples belonging to eight species ofthree genera were examined in this study. Their loca-

193

lities are roughly shown in Figure 12. All specimens
utilized are stored at the University Museum of the
University of Tokyo with registered numbers with prefix UMUT.
1. Laqueus rubellus (Sowerby) Figures 1-1-6
Fossil sample Jz (L) [N = 2] [UMUT CB18185]
Locality: Yamadakubo, Ichihara City, Chiba Prefecture (loc. 3).
Lithology and horizon: muddy medium grained
sand of the Jizodo Formation of the ShimosaGroup.
Age: Late Pleistocene.
Collector: Y. Kondo.
Remarks: Same locality as loco no. 132 of Tokuhashi and Endo (1984).
Recent sample Rk (13, 17,80,82, 100, 104) [N =184] [UMUT RBI8186].
Locality: eastern part of Sagami Bay, about 2 km
west of the Jogashima Islet (loc. 7) (35°7.9'N,
139° 35.1 'E, 80-90 m).
Status: living.
Bottom substrates: coarse grained sand with

,;
0

+

3d'+
121f

130"

0

J.o

+

1311''-$fe 5
e FOSSIL SAMPLE
28"+

Io RECENT SAMPLE+

Figure 12. Map showing the localities of fossil andRecent samples studied in this paper. Fossil localities;
1: Sawane Formation at Sawada Town; 2: Na-arai
Formation at Nagasakibana; 3: Jizodo Formation at
Yamadakubo; 4: Jizodo Formation at Atebi; 5: Wan
Formation at Kamikatetsu. Localities of Recent samples;
6: Mouth of Otsuchi Bay; 7: Off Jyogashima Islet; 8:
Off Hinomisaki; 9: Off Tsukumi.

194

Kazuyoshi ENDO

pebbles and shell fragments.
Collector: I. Hayami et al. (R/V Rinkai).
2. Laqueus blanfordi (Dunker) Figures 1-7-9
Recent sample at (1) IN = 18] IUMUT RBI8187].
Locality: Mouth of Otsuchi Bay (loc. 6).
Status: living.
Collector: K. Endo.
Recent sample at (2) IN = 9] IUMUT RBI8188].
Locality: Mouth of Otsuchi Bay (loc. 6).
Status: dead.
Collector: E. Tsuchida.
3. Laqueus quadratus Yabe and Hatai Figures 1-10-12
Fossil sampleNa IN = 16] IUMUTCBI8189].
Locality: eastern coast of Nagasakibana, Tokawa,
Choshi City, Chiba Prefecture (loc. 2).
Lithology and Horizon: tuffaceous matrix ofconglomerate of the Na-arai F ormation of the
Inubo Group.
Age: Pliocene.
Collector: K. Endo.
Recent sample Hi IN = 13] IUMUT RBI8190].
Locality: off Hinomisaki (loc. 8) (248 m), off
Etsuzaki (165-240 m, 215-297 m), off Mugi
(248 m), off Tanabe (264 m), Kii Channel.
Status: dead.
Collector: E. Tsuchida.
4. Laqueus sp. 1 Figures 1-13-15
Recent sample Ts(L) IN =46] IUMUTRBI8191].
Locality: off Tsukumi, Bungo Channel (loc. 9)(33°2.2'N, 132°5.4'E, 72-76 m).
Status: living and dead.
Bottom substrates: coarse grained sand withpebbles.
Collector: I. Hayami et al. (R/V Tansei).
Remarks: st. 31 of the cruise KT-84-12.
5. Laqueus sp. 2 Figures 1-16-18
Fossil sample SW IN = 44] IUMUT CBI8192].
Locality: Kaitate, Sawada Town, Sado Island,
Niigata Prefecture (loc. 1).
Lithology and Horizon: coarse grained sand ofB*£5'z~~M~~~.~~.tm~

the lower Sawane Formation.
Age: Pleistocene.
Collector: K. Endo.
Remarks: Precise locality is loco no. 2 of Endo
(1986).
6. Pietothyris pieta (Dillwyn) figures 1-19-21
Fossil sample Jz (P) IN = 10] IUMUTCBI8193].
Locality: Atebi, Kisarazu City, Chiba Prefecture(loc.4).
Lithology and Horizon: medium grained sand of
the Jizodo Formation of the Shimosa Group.
Age: Late Pleistocene.
Collector: K. Endo.
Recent sample Rk (P)[ N = 36] IUMUT RB 18194].
Locality: eastern part of Sagami Bay, about 2 km
west of the Jogashima Islet (loc. 7) (35°7.9'N,
139° 35.1 'E, 80-90 m).
Status: living.
Bottom substrates: coarse grained sand withpebbles and shell fragments.
Collector: I. Hayami et al. (R/V Rinkai).
7. Pietothyris sp. Figures 1-22-24
Recent sample Ts (P) IN = 43] IUMUT RBI8195].
Locality: off Tsukumi, Bungo Channel (loc. 9)(33°2.2'N, 132°5.4'E, 72-76 m).
Status: living.
Bottom substrates: coarse grained sand withpebbles.
Collector: I. Hayami et al. (R/V Tansei).
Remarks: st. 31 of the cruise KT-84-12.
8. Kikaithyris hanzawai (Yabe) Figures 1-25-27
Fossil sample Wa IN = 33] IUMUT CBI8196].
Locality: road-cut about 500 m north of Kamikatetsu, Kikai Island, Kagoshima Prefecture(loc.5).
Lithology and Horizon: coral sand of the Wan
Formation of the Ryukyu Group.
Age: Late Pleistocene.
Collector: I. Hayami.

•• :B*£M~~5'z~~M~~~.tt,M~~~~':':}.;~'-Cm~• • ~.:. 2 '?~m[tl]~jf--t, ~.~.:.~-t;g~~.s, < G~~m~~!f!l.t]Q t~.~.:.~-t;g ~.j~m~~~t}'-r: ~;g, .: h G ~~ • • ~L\j{IZSI~%l;g t::.bb~.:.:m~ Laqueus rubellus(Sowerby) ~:±:~.:.ffl~'-C, ~., ~.:}';.l: lf~~ • • I.:.~:il-t;g~, < ,?;Q'~~:I:~m~ • • ~Wi\1.r{.t::., ~~.s,< G~~m~~!f!l*~l!I!.rEt L-C, (1)~.11{~*-!fA=~tt~, (2)~!Ml~~!f!l*, N.,'U'((3)~M~J/X.Kfi~~- ~~lil{Jf:~ 3 '?~imJJJltMf;:t Gh;g, L. rubellus I':'~ L -CIt, .~~.:.:}.;~ '-C~~.s, < G~;Q~~.I.:.~L -c1il• • ~jf--t~I':'~L, ~M~~ ~ t::.t.J:~'*b~~':':},;~'-Clt, ~~.s,< G~c~.~~f*lt~ • • ~jf--t.: i::.7J'G, ':hG~? '!;,(3)~imJJJlil~)ji~~j;JJ-r·~;g,

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New members approved by the Council Meeting held on June 19, 1987.
Ordimary Members:Zhou, Baochun; Matsubara, Akiko; Ikejiri, Hiroyuki; Okura, Masatoshi; Hachiya, Kiichiro;Ohe, Fumio; Okamoto, Masanori; Kaneko, Naomoto; Takai Yuji; Jochi, Kotohiro; Ota,
Yasuhiro; Kiyokawa, Shoichi; Nagai, Hiromi; Kobayashi, Mariko; Ogata, Masashi; Kohno,
Naoki; Koizumi, Akihiro; Isaji, Shinji; Satoh, Atsushi; Uematsu, Tomosaburo.
Deceased Member:
Kuroda, Tokubei (Honorary Member).
Withdrawing Members:
Takamura, Kazuko; Sasakawa, Seiichi; Ookura, Mitsuko; Nakagawa, Hideki; Yasuhara, Naoki(Ordinary Mmebers), Nichu Sekiyu Kaihatsu (patoron).

IPA(7) World Direcfory of Paleontologists ,;:~Jiij~~~ff;~1t';l:. <k--.:.- ~(7)mM:~:J t:'- L.
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INTERNATIONAL PALAEONTOLOGICAL ASSOCIATIONWorld Directory of Paleontologists
QUESTIONNAIRE (please print or type responses using roman alphabet)
Family name or surname (we will be unable to print diacritical marks):

Individual name or !irst name in full and middle initial:

Address (institution, if any, street number or post oflice box, city, state/province, country and postal code):

Business phone number, including city or state area code:

Principal areas of study (either systematics, i.e. Brachiopoda; or topical, i.e. evolution). Please answer (A) or(B); or (A) and (B):(A) Maximum of 2 specializations on fossil groups, with stratigraphic range and geographical area of interest (ifpossible, list higher taxonomic categories, i.e. phylum or division, class, or order):(1)1 _ _ _ _ _ _ __Range: _ _ _ _ _ _ _ _ _ __ Area: _ _ _ _ _ _ _ _ _ __(2) _ _ _ _ _ _ __Range: _ _ _ _ _ _ _ _ _ __ Area: _ _ _ _ _ _ _ _ _ __(B) Topical approaches (cladistics, functional morphology, biostratigraphy, ecology, evolution, etc.). Limit is 10
words or less:Example of entry:
GRANT, RICHARD E., NATURAL HISTORY BLDG. E-207, SMITHSONIAN INSTITUTION, WASHINGTON,
D.C. 20560, USA. (202) 357-2211/2405. BRACHIOPODA: PERM., W. U.S., TETHYS. BIOSTR., ECOL., FUNCT.
MORPH.
Please complete and return this questionnaire by Dec. 31,1988 to: Rex Doescher, NBB E-207, Smithsonian Institution, Wash.,
D.C. 20560, USA. This questionnaire may be copied for secondary circulation.

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Errata for No. 146

p.42 and back cover, 829. MATSUMOTO and YOKOI; title read (Studies ofCretaceous Ammonite from Hokkaido-LXI) for -LX.

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.ffi 0 3 - 9 9 1 - 3 7 5 4 )Transactions and Proceedings of the PalaeontologicalSociety of Japan

New Series No. 147

October 30, 1987

CONTENTS
TRANSACTIONS
832. TASHIRO, Masayuki: CretaceousEomiodon and Costocyrena (Bivalvia) from southwest Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
833. KOBAYASHI, Teiichi and HAMADA, Takashi: The third addition to the Silurian
trilobite fauna ofYokokura-yama, Shikoku, Japan . . . . . . . . . . . . . . . . . . . . . . . 109
834. NIKO, Shuji: Early Carboniferous Eostaffella (primitive Fusulinacea) from the
Ichinotani Formation, Fukuji district, central Japan . . . . . . . . . . . . . . . . . . . . . . 117
835. KOBAYASHI, Teiichi and HAMADA, Takashi: On the Silurian trilobite faunule ofHitoegane near Fukuji in the Hida Plateau, Japan . . . . . . . . . . . . . . . . . . . . . . . . 131
836. MATSUMOTO, Tatsuro, ASAI, Akito and HIRANO, Hiromichi: Some inoceramids(Bivalvia) from the Cenomanian (Cretaceous) of Japan-II. Three species from Hokkaido, well known abroad but hitherto undescribed in Japan . . . . . . . . . . . . . . . . . . 146
837. TANABE, Kazushige and SHIGETA, Yasunari: Ontogenetic shell variation and streamlining of some Cretaceous ammonites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
838. ENDO, Kazuyoshi: Life habit and relative growth of some laqueid brachiopods
from Japan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
PROCEEDINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195