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Transactions and Proceedingsof thePalaeontological Society of Japan

New SeriesNo. 179

September 30, 1995

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Trans. Proc. Palaeont. Soc. Japan, N.S., No. 179, pp.157-168, 5 Figs., September 30, 1995

~ Some new species of freshwater bivalves from the
Mio-Pliocene Churia Group, west-central Nepal
KA TSUMI TAKAYASU1, DAMAY ANTI D. GURUNG2 and KEIJI MATSUOKA3
1Research Center for Coastal Lagoon Environments, Shimane University, Matsue, 690 Japan
2Department of Geology, Shimane University, Matsue, 690 Japan
3Toyohashi Museum of Natural History, Toyohashi, 441-31 Japan
Received 3 March 1995; Revised manuscript accepted 21 July 1995
Abstract. Systematic study of the Mio-Pliocene freshwater molluscan fossil fauna from the Churia
Group of Nepal has revealed many new species. In this first publication of the study, the bivalves aredescribed. The new species of bivalves are Lamellidens arungensis, Lamellidens longiformis,
Indonaia churia, Indonaia narayani, Indonaia jimuriensis, Indonaia tenella, Parreysia binaiensis,
Parreysia zigzagicostata and Physunio chitwanensis.
Key words: Siwaliks, Churia Group, freshwater molluscs, Mio-Pliocene, Nepal

Introduction

The Middle Miocene to Pleistocene Churia Group (Tokuoka et al., 1986) of Nepal, equivalent to the Siwaliks ofIndia and Pakistan, is well exposed in the southernmost
foothills of the Himalayas. Sediments of this Group
contain abundant fossil flora and fauna, among whichmolluscs make up an important group. In spite of many
reports about the abundance of molluscan fossils, there
are no detailed studies, and their taxonomy, distribution
and diversity are poorly understood.
Comparatively more work related to the taxonomy ofmolluscs from the Siwaliks has been carried out in India,
Burma and Pakistan (Vredenburg and Prashad, 1921;
Annandale, 1924; Prashad, 1927, 1930; Vokes, 1935,
1936; Bhatia and Mathur, 1973; Bhatia,1974). Althoughseveral paleontological studies have been carried out in
the Nepal Siwaliks, all have emphasized the vertebrate
fauna (Munthe et al., 1983; Corvinus, 1988; West et al.,1991) with little work related to molluscs (West et al., 1975 ;Takayasu, 1988,1992). The present systematic study is
being carried out for the first time in the Nepal Siwaliks inorder to understand the distribution and paleoecology of
the Late Tertiary freshwater fauna.
The Churia Group was deposited contemporaneouslywith uplift of the Himalayas. It is regarded as a fluvial
deposit, up to 6,000 m thick, which was deposited without
any major break. In these sediments most molluscan
fossils are preserved in situ, contrary to terrestrial fossils,
which are commonly preserved far from their habitat.
Therefore, molluscs should be better indicators of aquatic
ecological conditions prevailing at the time. Similarly, ifchanges in the type and distribution of molluscs in timeand space can be evaluated ecological variations due tochanges in climate as well as topography during the riseof the Himalayas can also be gauged. Apart fromcontrolling the climate of the Eurasian Continent, theHimalayas, at present, are a major biogeographic barrier.
Its role as a paleobiogeographic barrier can also be
determined by studying the presence or absence ofdifferent elements in the molluscan assemblage. In thiscontext, a detailed study of molluscan fossils can play animportant role.
In order to investigate these problems, a basic study ofidentifying and describing fossil molluscs is being carriedout. Most molluscs are recognized to be new species.
In this paper, new species of bivalves are described withan outline of geology and fossil localities. In the next
paper, gastropods will be described with a discussion ofmolluscan distribution.
Acknowledgments

We would like to thank Prof. K. Kizaki of Tribhuvan
University (Professor Emeritus of The University of Ryukyus) and Prof. T. Tokuoka of Shimane University, whoprovided much needed field data and encouragement forthis study. We also thank Dr. J. Itoigawa (Professor
Emeritus of Nagoya University) and Prof. I. Kobayashi of
Niigata University, for their guidance and advice. We aremuch obliged to the Central Department of Geology,
Tribhuvan University, for their assistance and support.
We are particularly indebted to Mr. R.D. White, Collection Manager, Division of Invertebrate Paleontology,

158

Katsumi Takayasu et al.

Peabody Museum of Natural History, Yale University, wholoaned the museum specimens for study. We are very
grateful to Dr. K. Ayyasami, Geological Survey of India,
Indian Museum, Calcutta, who made available themuseum specimens for comparative study.
Geological Setting and Fossil Localities
Molluscs discussed in this study were collected fromfossil localities (F11 to F23) reported by Tokuoka et al.
(1986) and two additional localities (F24 and F25), fromwest-central Nepal (Figure 1). As the lithostratigraphy
and magnetostratigraphy of the area (Figure 2) have been
established by Tokuoka et al. (1986), their nomenclature isadopted here.
In the studied area (Figure 1), which covers the Arung
Khola and Binai Khola valleys, the Churia Group is confined by the Main Boundary Thrust to the north and by the
Frontal Churia Thrust to the south. The Central Churia
Thrust within this group separates it into a North and aSouth Belt. The strata in the North Belt are steeply
inclined toward the north, whereas in the South Belt thebeds are less steeply inclined. All the beds have ageneral east-west strike. Lithostratigraphically the Churia Group is divided into the Arung Khola, Binai Khola,
Chitwan and Deorali Formations, in ascending order. As
a whole the Churia Group shows a coarsening-upward
sequence, attaining a thickness of up to 6,000 m.
The Middle Miocene to early Late Miocene Arung
Khola Formation is composed mainly of irregular alternating beds of fine-grained sandstone and siltstone withintercalations of variegated and coal black mudstone. It
is subdivided into a lower (AI), middle (Am) and upper (Au)members. The Late Miocene to Early Pliocene Binai
Khola Formation is dominated by thick-bedded sandstone
and thin-bedded alternating beds of sandstone and siltstone with intercalations of pepper-and-salt sandstone.
It is subdivided into a lower (BI), middle (Bm) and upper(Bu) member. The Chitwan Formation, of Late Pliocene
to Early Pleistocene age, is composed predominantly ofgravel beds with subordinate sand and silt layers. The
uppermost Deorali Formation, of Late Pleistocene age,consists of poorly sorted boulder-conglomerate beds.
The North Belt contains strata up to the middle memberof the Binai Khola Formation, whereas in the South Belt
strata from the upper member of the Arung Khola Formation onward are distributed.
Most fossil occurrences are concentrated between theupper member of the Arung Khola Formation and the
middle member of the Binai Khola Formation. In thestudied area molluscan fossils are distributed at 15 sites(from F-11 to F-25) and are grouped into five stratigraphic
horizons, F (Au), F (BI-1), F (BI-2), F (Bm-1) and F (Bm-2)(Figure 2). From the data so far collected the molluscan
fossils are found to occur around 9.0 Ma, at F (Au) horizon,
about the middle part of the upper member of the Arung
Khola Formation. Above the topmost horizon F (Bm-2)(upper part of the middle member of the Binai Khola
Formation) freshwater molluscan fossils are uncommon.

Molluscan fossils are generally found in dark gray to
black mudstone and silty sandstone. Some specimens
are deformed but most of the bivalves have conjoined
valves suggesting little or no transportation. Within afining-upward sequence formed by a meandering river
system, molluscan fossil horizons occur at two specificlevels: at the transitional part from the lower coarsegrained unit to the llPper fine-grained unit, and at theuppermost part of the upper fine-grained unit. Most of
the fossil horizons lie at the latter level with only F-12
occurring at the former level (Takayasu, 1992). One fossil
locality, F-21, consists of two layers of mud blocks intercalated in a thick-bedded sandstone. According toTokuoka et al. (1986), these fossil-bearing blocks havebeen derived from the underlying fossil bed. Most of thefossil localities contain a rich fauna, with varying states ofpreservation. Molluscan fossils are found with fish pharyngeal teeth, fish scales, crocodile teeth, bone fragments
and charophyte gyrogonites.
All the specimens described here are deposited at the
Toyohashi Museum of Natural History, Toyohashi, 441-31
Japan.
Systematic paleontology
Class Bivalvia
Family Unionidae Fleming, 1828
Genus Lamellidens Simpson, 1900
Type species.-Unio marginalis Lamarck, 1819. Recent,
East India.
Geologic range.-Miocene to Recent.
Remarks.-The genus has elongated elliptical shell andpointed behind. Anterior end is narrow and posterior end
broad with posterior dorsal wing. Umbonal part is covered with curved radiating ridges which may be slightly
zigzag-shaped or almost concentric, fading out gradually.
Dentition is composed of compressed, elongatedpseudocardinal and long posterior lamellar teeth.
The genus Lamellidens was established for widelydistributed species of Unionidae in India and Burma.
Many representative species of this genus of the Indian
subcontinent are well documented in Preston (1915).
Fossil species of this genus have been reported from the
Siwaliks of Pakistan (Vokes, 1935, 1936), India and Burma(Prashad, 1921,1927,1930; Annandale, 1924).
Lamellidens arungensis n. sp.
Figures 3-1-4Type loca/ity.-The left bank of the west to east flowing
Arung Khola (F-11 in Figure 1), about 700 m west of theconfluence with the Murali Khola. Lower member of the
Binai Khola Formation.
Description.-Shell moderately large for the genus,
subrhomboidal in outline and moderately elongated.
Valves subinflated and a little thick. Umbo only slightly

991.

Freshwater bivalves from Mia-Pliocene of Nepal

159

27"32'~ River Depositst"~'w.1 Deorali Fonnation
1~:w\;::1 Chitwan Formation:=~~~ BBU"} Binai Khola~ B~ " Formation~[]]] ~:} Arung~hola
FonnatlOn"

V77?I.
ICLLLJ AI

UIlIIIIIll Midland Supergroup•

Fossil Locality

Figure 1. Generalized geological map of the Arung-Binai Khola area, west-central Nepal (after Tokuoka
et al., 1986), with molluscan fossil localities.

Katsumi Takayasu et al.

160

Ma Polarity
Chron

West-central Nepal
D

Boulder conglomerates, ill-sorted

C

Cobble conglomerates, well-sorted

1----+------- ---- --- ----- ---- -- -- -- -- ---- ---- --I--~+-;;J

Pebble conglomerates and sandstone..:l mAlternating beds of sandstone andmudstone conglomeratic in the North
Belt. (Ss » Ms)

r:.::

o <
=:

g
~ <

~

,-...

~

....:l~..

-----------------------------------------u~~ F(Bm -2)---[F13, F18, F19, F20, F21,

F24, F25]~ F(Bm -1)----[F16]~ F(BI -2) -----[F14, F17]

Alternating beds of sandstone andmudstone. (Ss > Ms)=~ F(Bl-l) -----[Fll, F12, F15, F22]-<
~ I--+--+--j.-ltemailiigbeds-of"sandstone-iliici---- ~ F(Au) -------[F23]00umudstone. (Ss>Ms); Mudstone rarely
variegated
Alternating beds of mudstone andsandstone. (Ss=Ms); Sandstone partly
calcareous and mudstone variegated.

Alternating beds of sandstone andmudstone. (Ss<Ms); Mudstonevariegated.

Figure 2. Stratigraphie position of fossil horizons with magnetostratigraphy and chronology of the ArungSinai Khola area correlated with the Potwar Plateau of Pakistan (after Takayasu, 1988).

raised, broadly rounded and situated at anterior third of
the shell. Dorsal margin nearly straight and long. Anterior margin regularly and somewhat narrowly rounded.
Ventral margin widely rounded and rather long. Posterior
margin truncated above the medial line. Posterior ridge
indistinct and not extending to the ventral margin. Posterior wing long and narrow. Ligament placed posterior to
the beak, quite long and protruding. Shell surface withconcentric growth lines. Hinge only partially observed in
the paratype 2, a left valve, two long lamellar teeth, upper
one more prominent.

lidens lewisi Vokes (1936) from the Upper Siwalik ofPakistan in that the former is smaller is size and has more
broadly rounded ventral margin. It can be distinguishedfrom Lamellidens jammuensis Prashad (1921), Upper
Siwalik Beds, Jammu, in having a less inflated shell,smaller posterior wing and more narrowly rounded anterior
margin.
Etymology.- The name is taken from the river, Arung
Khola, which flows by the type locality.
Stratigraphic range.-Lower to middle member of the
Binai Khola Formation.
Localities.-F-11, F-12, F-16 and F-17.

Measurements (in mm).-*

TMNH
coil. cat. no. Length Height Depth Valve02027 (Holotype)
83.4
48.2
11.8/2 Both (slightly compressed)
02028 (Paratype 1)
70.0
40.8
Left (slightly compressed)
02029 (Paratype 2)
70.0
42.0
Left
02030 (Paratype 3)
67.6
33.3
Right (incomplete)Abbreviation for Toyohashi Museum of Natural History, Toyohashi, Japan.

*

Comparison.- The present species differs from Lamel-

Lamellidens /ongiformis n. sp.
Figures 3-5-7Type locality.- The right bank of the Narayani River,
500 m south of the confluence with the Binai Khola (F-21
in Figure 1). Middle member of the Binai Khola Forma-

991.

Freshwater bivalves from Mio- Pliocene of Nepal

16 1

Figure 3. 1- 4. Lamellidens arungensis n. sp.1 : holotype, TMNH02027, 2: paratype 1, TMNH02028, 3 :paratype 2, TMNH02029, 4 : paratype 3, TMNH02030. 5- 7. Lamellidens /ongiformis n. sp. 5 : holotype,
TMNH02031 , 6 : paratype 1, TMNH02032, 7 : paratype 2, TMNH02033. All figures are natural size.

tion .
Description .-Shell moderately large, much elongatedin outline and very inequilateral. Anterior end narrower
than posterior end. Valves thick and quite inflated, more
so along the medial part. Umbo small, low, inconspicuous and very anteriorly placed, at anterior fifth of thevalve. Dorsal margin straight and very long. Anterior
margin narrowly rounded and short. Ventral margin very
long and gently curved to nearly straight. Posterior
margin incompletely preserved in the holotype, but asobserved in the paratype 2, narrowly rounded at themedial part, almost straight above it and forming a broad

angle with the straight dorsal margin. Posterior ridge welldeveloped, high, long and round - topped, separated fromthe posterior wing by a distinct groove. Posterior winglong and narrow. Shell surface covered with concentric
growth lines as observed in the paratype 2. Internal
structure and hinge not observed.
Measurements (in mm).TMNH coil. cat no.
02031 (Holotype)02032 (Paratype 1)02033 (Paratype 2)

Length
90.0 +
91.0 +
52.0

Height40.2 +
37.0
20.0

Depth
22.2 + / 2
21.0 + / 2
16.9/ 2

Valve
Both
Both
Both

Katsumi Takayasu et al.

162

Comparison.-Owing to its rather elongated shape,
Lamellidens longiformis is quite distinct from most of theother Lamellidens species except L. subparal/elus.
Vokes (1935) from the Lower Siwalik of Pakistan. The
present species possesses a longer posterior wing, moreanteriorly placed umbo, and narrower anterior end and issmaller in size than L. subparal/elus.
Etymology.-It is named for its characteristic long shell
shape.
Stratigraphic range.-Middle member of the Binai Khola
Formation.
LocaJities.-F-16 and F-21.

Genus Indonaia Prashad, 1918
Type species.-Unio caeruleus Lea, 1831. Recent,West Bengal, India.
Geologic range.-Miocene to Recent.
Remarks.- The genus is characterized by ovate andslightly elongated shell with thin but relatively solid
valves. The umbonal area and a part or all of the shell ismarked by narrow and fine zigzag sculpture. Pseudocardinals are short and stout, and posterior lateral teeth arelamelliform.
The genus Indonaia was established by Prashad (1918)
for Indian species previously grouped with the genus
Nodularia Conrad (1853) after examining the soft parts andthe glochidium structure. In the Treatise on Invertebrate
Paleontology, Haas (1969) treated the genus Indonaia as asynonym of Radiatula Simpson (1900), a subgenus of
Parreysia Conrad (1853). Further, Subba Rao (1989) has
also followed Haas (1969) mentioning the main differences
between Parreysia s.s. and Radiatula, the former having aswollen ventral margin and the latter an almost straightone. However, the type species of Radiatula, Unio
crispisulcatus, has a rather swollen ventral margin like thatof Parreysia s.s. On the other hand, the type species ofIndonaia, U. caerulea, has a longer and nearly straight
ventral margin, which more resembles the present new
species. Therefore, Indonaia is kept as an independent
genus in the present report. It is also used in the samemanner by Brandt (1974) for Thai species. Fossil speciesof this genus are recorded from Pakistan (Vokes, 1935,
1936), India (Prashad, 1927; Bhatia and Mathur, 1973) andBurma (Vredenburg and Prashad, 1921 ; Annandale, 1924).

Indonaia churia n. sp.
Figures 4-1-3Type locaJity.-The right bank of the Narayani River
about 500 m south of the confluence with the Binai Khola(F-21 in Figure 1). Middle member of the Binai Khola
Formation.
Description.-Shell moderately large, elongated oval inshape with subtruncated posterior end. Valves moderately thick and rather inflated. Umbo prominent,
rounded, anteriorly directed and situated at one third the
distance from anterior end. Dorsal margin slightly

curved. Anterior margin short and regularly rounded.
Ventral margin long and gently curved. Posterior margin
narrowly rounded and somewhat truncated. Posteriorridge bluntly rounded. Posterior slope narrow and a little
convexed. Shell surface marked only with concentric
growth lines. Hinge partially exposed (in holotype, a rightvalve) but slightly eroded; hinge slender with a small,short pseudocardinal and a long, gently curved lamellar
tooth. Adductor muscle scars are observed in the core of
the paratypes. Anterior one oval in outline, deeply impressed and posterior one similar in outline but larger andshallower. Pallial line fairly impressed and without sinus.
Inner ventral margin smooth.
Measurements (in mm).TMNH coli. cat. no.
02034 (Holotype)02035 (Paratype 1)02036 (Paratype 2)

Length Height Depth
40.6+ 25.4+
8.1+
41.0
29.0
14.0/244.7 + 30.5+ 14.0/2

Valve
Right
Both (incomplete)
Both (incomplete)Comparison.-Indonaia churia has a more anteriorly
placed and less prominent umbo than Indonaia prashadi
Vokes (1936) from the Lower Siwalik of Pakistan. The
present species can be distinguished from Indonaia mittali
Prashad (1927) of the Upper Siwalik, Jammu, Kashmir as
the former possesses a less prominent umbo and shorter
anterior end. It also differs from Indonaia glyptica
Vredenburg and Prashad (1921) from the Miocene Irrawaddy Series, Burma, in having a less rounded ventral marginand smaller umbo.
Etymology.-It is named after the low mountain range,
the Churia.
Stratigraphic range.-Middle member of the Binai Khola
Formation.
LocaJities.-F-21 and F-24.

Indonaia narayani n. sp.
Figures 4-4-7Type LocaJity.-Right bank of the Narayani River, about
500 m south of the confluence with the Binai Khola (F-21
in Figure 1). Middle member of the Binai Khola Formation.
Description.-Shell moderately large and ovate trigonalin outline. Valves fairly thick and inflated. Umbo prominent, anteriorly directed, rounded and placed very anteriorly, at one fourth of the shell length. Dorsal margin
rather arched with maximum curvature just behind theumbo. Anterior margin short and regularly rounded.
Ventral margin long and very gently arched. Posterior
margin sharply curved. Posterior ridge distinct and nearlystraight. Posterior slope narrow and convexed. ligament small, lenticular in shape and placed just behind theumbo. Surface of the shell bearing fine concentric
growth lines with zigzag sculpture limited on the umbonal
area. The dentition can not be observed in the holotype
but is well exposed in the paratype 1 (left valve). Hinge
plate slender and long with short interdentum. Anterior
pseudocardinal consists of two short and sharp ridges;

991.

Freshwater bivalves from Mio- Pliocene of Nepal

1

163

2

I
I

,,
\

\

,,

,

'- ....

"- ....

_-

5a

9

14

11a
Figure 4. 1- 3 . Indonaia churia n. sp.1 : holotype, TMNH02034, 2 : paratype 1, TMNH02035, 3 : paratype2, TMNH02036. 4 - 7 . Indonaia narayani n. sp. 4: holotype, TMNH02037, 5 : paratype 1, TMNH02038 ; 5a,outer surface of left valve, 5b, inner view of left valve, 6 : paratype 2, TMNH02039, 7: paratype 3, TMNH02040.
8 - 11. Indonaia jimuriensis n. sp. 8 : holotype, TMNH02041, 9 : paratype 3, TMNH02044, 10: paratype 1,
TMNH02042 ; 10a, outer view of left valve, 10b, inner view of left valve, 11 : paratype 2, TMNH02043 ; 11a, outerview of right valve, 11b, inner view of right valve. 12- 14. Indonaia ten ella n. sp. 12 : holotype, TMNH02047, 13 :paratype 1, TMNH02048, 14 : paratype 2, TMNH02049. All figures are natural size.

Katsumi Takayasu et a/.

164anterior one larger and posterior placed just below thebeak. Posterior lamellar laterals two, long, bladelike(lower one is more prominent). Anterior adductor scar
deeply impressed and oval in shape whereas posterior
one larger and shallower. Pallial line faintly impressedand entire.

Measurements (in mm).TMNH coil. cat. no.
02037 (Holotype)02038 (Paratype 1)02039 (Paratype 2)02040 (Paratype 3)

Length Height Depth Valve
33.3
32.9
12.0/2 Both52.3+ 32.0+ 12.7 + Left (incomplete)
31.6
24.9
Right
8.0
36.0
26.0+
Left (incomplete)Comparison.- The present species has a more protruding posterior end and more anteriorly placed umbo thanthe preceding species, Indonaia churia. In shape andsize Indonaia narayani is somewhat similar to Indonaia
glyptica Vredenburg and Prashad (1921) from the Miocene
Irrawaddy Series, Surma, but the former has a less prominent umbo and less rounded ventral margin. It has asmaller umbo situated more anteriorly with a much archeddorsal margin compared to Indonaia mittali Prashad (1927)
from the Upper Siwalik, Jammu, Kashmir.
Etymology.- The new species is named after the majorriver of Nepal, the Narayani, as its type locality lies along
its bank.
Stratigraphic range.-Middle member of the Sinai Khola
Formation.
Localities.-F-18, F-21 and F-24.
Indonaia jimuriensis n. sp.

Figures 4-8-11

Type locality.-About 1.3 km northwest of Dumkibas, atthe left bank of the Jimuri Khola (F-19 in Figure 1). Middle
member of the Sinai Khola Formation.
Oescription.-Shell moderately large, about 38.0 mm insize, elongated oval in outline. Valves moderately thick,not very solid and slightly inflated. Umbo rounded, small
situated anteriorly at one third of the shell length. Dorsal
margin broadly arched. Anterior margin rounded and alittle high. Ventral margin long and gently curved.
Posterior margin short and narrowly rounded. Posteriorridge not prominent but rounded and extending to theposterior end. Posterior slope narrow and slightly convex. Surface of the shell smooth with fine concentric
growth lines only. Umbonal cavity shallow. Dentition
exposed in paratype 1 and paratype 2. Hinge plate
slender. Pseudocardinals short and compact; one in theright valve and two in the left valve. Posterior lamellar
laterals are long and smooth; one in the right valve andtwo in the left valve (lower one more prominent). Anterior
adductor muscle scar deeply impressed and oval inshape; posterior one shallower, larger and round in
shape. Pallial line faintly impressed and entire. Inner
ventral margin smooth.

Measurements (in mm).TMNH coil. cat. no.
02041 (Holotype)02042 (Paratype 1)02043 (Paratype 2)02044 (Paratype 3)
02045
02046

Length Height
38.2+ 27.5+
35.9+ 23.7
37.8+ 21.0+
26.9+ 22.8
38.4+ 25.7+
37.2
25.8

Depth
11.7/2
8.3
8.0

6.6

Valve
Both (slightly compressed)
Left (slightly deformed)
Right (slightly deformed)
Left
Both (crushed)
Left

Comparison.-Due to its less prominent and broadly
rounded umbo, Indonaia jimuriensis can be distinguishedfrom most of the other species of Indonaia. The present
species, however, is slightly similar in outline to Parreysia
latouchei Vredenburg and Prashad (1921) from the
Miocene Irrawaddy Series of Surma but the former has no
zigzag sculpture and the umbo is more rounded.
Etymology.-It is named after the River Jimuri Khola,flowing near its type locality.
Stratigraphic range.-Middle member of the Sinai Khola
Formation.
Locality.-F-19.
Indonaia tenella n. sp.

Figures 4-12-14

Type locaJity.-South of Dumkibas (F20 in Figure 1),along the Kedi Khola, about 800 m upstream from theconfluence with the Sinai Khola. Middle member of the
Sinai Khola Formation.
Oescription.-Shell small in size, rounded trapezoidal inshape. Valves rather this and a little inflated. Umboslightly raised, inconspicuous, rounded and situated atanterior third of the shell. Dorsal margin long and nearlystraight. Anterior margin short and narrowly rounded.
Ventral margin long and broadly rounded. Posterior
margin truncated. Posterior ridge moderately prominent,
rounded and terminates at posterior margin forming anangulation just below the medial line. Posterior wing
wide and flat. The umbonal area as well as half the disk
area sculptured with fine zigzag lines and rest of the shellsurface covered with irregular concentric growth lines.
The internal structures as well as the dentition can not be
observed.
Measurements (in mm).TMNH coil. cat, no.
02047 (Holotype)02048 (Paratype 1)02049 (Paratype 2)

Length
30.8+
30.4+
21.6

Height
19.3+
19.0
12.2

Depth
5.0+
5.0+

Valve
Right
Right
Right

Comparison.-Indonaia teneIJa is somewhat similar toIndonaia hasnotensis Vokes (1935) from the Middle
Siwalik of Pakistan in shell outline and surface sculpture
but the former is much smaller in size and has a thinnershell with a more straight dorsal margin. The present
new species is also similar to Parreysia (Radiatula) lima
(Subba Rao, 1989, p.190, figures 528-531), a Recent
species of northeast India, in size and surface sculpture,
but the former has a less rounded posterior end, narrower
anterior margin and more rounded ventral margin.
Etymology.-It is named so as it means 'quite delicate'991.

Freshwater bivalves from Mio-Pliocene of Nepal

in Latin.
Stratigraphic range.-Middle member of the Binai Khola
Formation.
Localities.-F-20 and F-25.
Genus Parreysia Conrad, 1853

Type species.-Unio multidentatus Philippi. Recent,India.
Geologic range.-Miocene to Recent.
Remarks.- The genus is characterized by a heavy,
inflated and rounded subrhomboidal shell with radial
zigzag sculpture on the umbo or on the whole of the disk.
Pseudocardinals are irregular, heavy and striated. Lateral teeth are lamelliform, short and two in each valve.
In the Treatise on Invertebrate Paleontology Haas (1969)
subdivided this genus into two subgenera, Parreysia s.s.
and Radiatula Simpson (1900) for the South Asian species.
As already mentioned the type species of the subgenus
Radiatula is much similar to Parreysia s.s. and therefore
the genus Parreysia is not further subdivided in this paper.
Many fossil species of this genus have been reported fromthe Siwaliks of Pakistan (Vokes, 1935, 1936), India (Prashad, 1927) and Burma (Vredenburg and Prashad, 1921).
Parreysia binaiensis n. sp.

Figures 5-1-5Type locality.-About 700 m west of the confluence of
the west-east flowing Arung Khola and the north-south
flowing Murali Khola (F-11 in Figure 1). Lower member ofthe Binai Khola Formation (B1).
Oescription.-Shell moderately large for the genus,
subtrigonal in shape with rather thick and inflated valves.
Umbo large, inflated and situated subcentrally toward
anterior side. Dorsal margin arched. Anterior margin
regularly rounded. Ventral margin short and moderately
curved. Posterior margin short, nearly straight andsubtruncated. Posterior ridge prominent, sharply rounded
and diagonally extends from umbo to posteroventral
angulation. Posterior slope a little wide and flat.
Ligamental groove shallow and extends from beak to
small angulation in the posterodorsal margin. Umbonal
area with zigzag sculpture and remaining area covered
with irregular concentric growth lines. Umbonal cavity
moderately deep. Hinge plate thick; anterior and posterior teeth set nearly at right angle with flat, short interdentum. Dentition moderately heavy; pseudocardinals
irregularly serrated, strong, two in the left valve (anterior
one is parallel to the dorsal margin and larger) and one in
the right; laterals relatively short, straight and two in both
valves (upper one larger and lower one composed of few
short, inclined ridges). Anterior adductor muscle scar
deeply impressed and oval in shape with small andshallow pedal protractor muscle scar just below it.
Posterior adductor muscle scar oval in shape, shallower
and larger with pit-like pedal retractor muscle scar above.
Pallial line faintly impressed without sinus. Inner ventral

165

margin smooth without crenulation.

Measurements (in mm).TMNH coli. cat. no.
02050 (Holotype)02051 (Paratype 1)02052 (Paratype 2)02053 (Paratype 3)02054 (Paratype 4)
02055
02056
02057

Length Height39.85 33.9
35.1
32.5
38.0
32.9
24.2+ 21.6
20.7 + 19.0
41.4+ 38.5
28.6 + 28 +26.6+ 20.5

Depth
11.7
12.2
19.5/2
12.5/2
6.8+
12.8
9.2
11.8

Valve
Left
Right
Both
Both (incomplete)
Left
Left
Left
Left

Comparison.- The present species shows some similarity in surface sculpture and umbo position to Parreysia
detterai Vokes (1936) from the Upper Siwalik Series,
Pakistan, but the latter is more triangular in shape with avery arched hinge plate and almost vertical posteriorridge. It differs from Parreysia tatrotensis Vokes (1935),
also from the Upper Siwalik Series, in having a lesselongated shape and no posterior wing. The new
species is distinct in its trigonal outline, inflated umbo andstrong hinge plate from all the species of the Recent
Parreysia group from India and Burma illustrated by Subba
Rao (1989).
Etymology.- The new fossil species is named after theRiver Binai Khola after which the formation containing theabove described fossil is also named.
Stratigraphic range.-Lower member of the Binai Khola
Formation.
Localities.-F-11 and F-12.
Parreysia zigzagicostata n. sp.

Figures 5-6-10

Type locality.-About 700 m west of the confluence of
the Arung Khola and the Murali Khola (F-12 in Figure 1).
Lower member of the Binai Khola Formation.
Oescription.-Shell moderately large in size androunded trigonal in shape. Valves inflated and moderately thick. Umbo subcentral, toward anterior half, prominent and narrowly rounded. Dorsal margin broadly
rounded. Anterior margin regularly rounded. Ventral
margin short and gently rounded. Posterior marginsUbtruncated. Posterior ridge prominent with wide andslightly concave posterior slope. Ligamental groove
narrow and faintly impressed, extending from the beak to
the angulation in the posterodorsal margin. Shell surface
strongly sculptured with radial zigzag ridges from umbonal
area to more than half of the disk area and the lower part
covered with concentric growth lines. Umbonal cavity
shallow and broadly rounded. Dentition well developedwith strong hinge plate separated by a little long interdentum. Pseudocardinals irregularly serrated, moderately strong, two in the left valve (upper-anterior one mostdeveloped and ridgelike) and one in the right; laterals
short but strong, curved, two in both valves (upper one
more prominent and bladelike; lower one weakly developed diagonal ridges). Anterior adductor muscle scar
oval in shape, deeply impressed with shallow pedal

Katsumi Takayasu et al.

166

protractor muscle scar just below it. Posterior one larger
but shallower with pit-like pedal retractor muscle scar justabove. Pallial line faintly impressed and entire. Inner
margin smooth without crenulation.

Measurements (in mm).TMNH coil. cat. no.
02058 (Holotype)02059 (Paratype 1)02060 (Paratype 2)02061 (Paratype 3)02062 (Paratype 4)

Length
30.6+
29.0+
23.5
21.3
27.7+

Height
25.9+
22.1+
17.4
17.0
20+

Depth
8.3
9.2
10.0/2
11.4/2
10.1

Valve
Right
Left
Both
Both
Right

Comparison. -Parreysia zigzagicostata is characterized
by its broadly rounded hinge plate, less prominent umboand strong zigzag sculpture. The preceding species
Parreysia binaiensis is distinguished from the present
species in having a more arched hinge plate, muchrounded, raised umbo and zigzag sculpture limited to theumbonal area. The new species is also more elongatedthan Parreysia detterai Vokes (1936) from the Upper
Siwalik of Pakistan and the dorsal margin in the latter isvery arched. Unio edwini described by Gupta (1930) from
the Miocene Irrawaddy Beds of Burma, has a shell sculpture like Parreysia zigzagcostata but in the former the ribs
are coarser and persistent down to several shell layers.
In shell outline the present species is similar to the Recent
Burmese species Parreysia bhamoensis (Subba Rao, 1989,
p. 177, figures 446-447) but the latter has faintly marked
zigzag sculpture and lamellar pseudocardinals and islarger in size.
Etymology.-It is named after its characteristic shellsurface sculpture.
Stratigraphic range.-Lower member of the Binai Khola
Formation.
Localities.-F-ll and F-12.

to the gesus Physunio, but due to poor preservation of thespecimens a more exact assignment cannot be made atpresent. This is the first report of fossil Physunio fromSouth Asia. The genus is considered an Indo-Chineseelement; its westernmost extension is up to Assam,
northeast India at present but it is mainly distributed in
Cambodia, Vietnam and Thailand (Annandale, 1918).
Therefore, the present finding indicates a much wider
western extension during Pliocene time.

Physunio chitwanensis n. sp.
Figures 5-11-14

Type Locality.-Right bank of the Narayani River, 500 m
south of the confluence with the Binai Khola (F-21 in
Figure 1). Middle member of the Binai Khola Formation.
Description.-Shell moderately large in size. Roundedrhomboidal in outline with anterior end narrower thanposterior. Valves moderately thick and not much inflated. Umbo, low, inconspicuous, anteriorly directed, situated at about one fourth the distance from anterior end.
Dorsal margin nearly straight and slightly long. Anterior
margin short and regularly rounded. Ventral margin
anteriorly short and arched, posteriorly long and nearlystraight. Posterior margin long and truncated with bluntly
produced basal part. Posterior ridge faintly developed,
posterior slope wide and slightly concave. Posterior
wing well developed, high and subtrigonal in outline.
Surface of the shell marked with concentric growth lines
as observed in paratype 1. Hinge and the internal structures of the shell not observed but in paratype 2 (rightvalve), one long well developed posterior lateral parallel tothe dorsal margin observed.
Measurements (in mm).-

Genus Physunio Simpson, 1900

Type species.-Unio gravidus Lea, 1856=Unio superbus Lea, 1843. Recent, South East Asia.
Geologic range.-Pliocene to Recent.
Remarks.- The genus is characterized by thin, rhomboidal or obovate shell with more or less high posterior
wing and produced posterior base. Umbo is anteriorly
placed and sculptured with zigzag folds. Hinge consistsof elongated pseudocardinal and short lamellar laterals.
This genus is divided into three subgenera, Physunios.s., Lens and Velunio in the Treatise on Invertebrate
Paleontology. From its ovate-rhomboidal outline andhigh wing, the present fossil species doubtlessly belongs

TMNH coil. cat. no.
02063 (Holotype)02064 (Paratype 1)02065 (Paratype 2)02066 (Paratype 3)

Length
82.9+
46.8
80.8
65.0+

Height
62.8
31.8
57.5+
52.3+

Depth
6.0
16.0/2
20.7/2

Valve
Right
Left
Both (little compressed)
Both (incomplete)Comparison.-Owing to its distinctive shell outline withhigh posterior wing it is placed in the genus Physunio.
The present species is somewhat similar to the Recent
Burmese species Physunio micropteroides Annandale(1918) in having a low umbo and a subtrigonal wing, but theformer is larger in size and less elongated.
Etymology.-It is named after the valley of Chitwan, partof which is the study area.
Stratigraphic range.-Middle member of the Binai Khola
Formation.

Figure 5. 1-5. Parreysia binaiensis n. sp.1: holotype, TMNH02050; 1a, outer view, 1b, inner view, 2: paratype 1,
TMNH02051 ; 2a, outer view, 2b, inner view, 3: paratype 2, TMNH02052; 3a, outer view of the right valve, 3b, dorsal
view, 3c, posterior view, 4: paratype 3, TMNH02053, 5: paratype 4, TMNH02054. 6-10. Parreysia zigzagicostata n.
sp. 6: holotype, TMNH02058; 6a, inner view of right valve, 6b, outer view of right valve, 7: paratype 1, TMNH02059;
7a, inner view of left valve, 7b, outer view of left valve, 8: paratype 4, TMNH02062, 9: paratype 2, TMNH02060, 10 :paratype 3, TMNH02061. 11-14. Physunio chitwanensis n. sp. 11: holotype, TMNH02063, 12: paratype 1, TMNH02064,
13: paratype 3, TMNH02066, 14: paratype 2, TMNH02065. All figures are natural size.

991 .

Freshwater bivalves from Mio- Pliocene of Nepal

167

9

7b

\

\

\
\

\
\

\
\

\

I

...

--- --

13

Katsumi Takayasu et al.

168
Localities.-F-20 and F-21.

References cited
Annandale, N., 1918: Aquatic molluscs of the Inle lakeand connected waters. Records of the IndianMuseum, vol. 14, p.103-183, pis. 10-19.
Annandale, N., 1924: Fossil molluscs from the Oil-Measures of the Dawna Hills, Tenasserim. Records ofthe Geological Survey of India, vol. 55, p. 97-101, pis.
6-7.
Bhatia, S.B., 1974: Some Pleistocene molluscs from
Kashmir, India. Himalayan Geology, vol. 4, p.371393.
Bhatia, S.B. and Mathur, AK, 1973: Some upper Siwalik
and Late Pleistocene molluscs from Panjab.
Himalayan Gelogogy, vol. 3, p. 24-58.
Brandt, RAM., 1974: The non-marine aquatic Molluscaof Thailand. Archiv fur Molluskenkunde, Bd. 105, p.
1-423, pis. 1-30.
Conrad, T.A., 1853: Synopsis of the family of Naiades ofNorth America; with notes and a table of some of thegenera and subgenera. Proceedings of the National
Academy of Science, Philadelphia, vol. 6, p. 243-269.
Corvin us, G., 1988: The Mio-Plio-Pleistocene litho- andbiostratigraphy of the Surai Khola Siwaliks in WestNepal: First results. C.R. Academie des SCiences,
Paris,t. 306, Serie2, p.1471-1477.
Gupta, B.B., 1930: Two new species of Unio. Records ofthe Geological Survey of India, vol. 63, p.210-213, pI.
5.
Haas, F., 1969: Bivalvia, Unionacea. In, Moore, R.C. ed.,Treatise on Invertebrate Paleontology. Part N. Mollusca 6, vol. 1, p. N411-N470. Geological Society ofAmerica, New York.
Munthe, J., Dongol, B., Hutchison, J.H., Kean, W.F.,
Munthe, K. and West, R.M., 1983: New fossil discoveries from the Miocene of Nepal include a hominoid.
Nature, vol. 303, p.331-333.
Prashad, B., 1918: Studies on the anatomy of Indianmollusca. Records of the Indian Museum, vol. 15, p.
143-148.
Prashad, B., 1921: On a new fossil Unionid from the Intertrappen beds of peninsular India. Records of theGeological Survey of India, vol. 51, p.368-370, pI. 12.
Prashad, B., 1927: On some fossil Indian Unionidae.
Rocords of the Geological Survey of India, vol. 60, p.

308-312, pI. 25.
Prashad, B., 1930: On some undescribed freshwatermolluscs from various parts of India and Burma.
Records of the Geological Survey of India, vol. 63, p.
428-433, pI. 19.
Preston, H.B., 1915: The fauna of British India including
Ceylon and Burma, Mollusca (Freshwater Gastropoda
and Pelecypoda). p.I-XI+1-244, Taylor and Francis,
London.
Simpson, C.T., 1900: Synopsis of the najades or pearly
freshwater mussels. Proceedings of the UnitedStates National Museum, vol. 22, p.501-1075.
Subba Rao, N.V., 1989: Handbook freshwater molluscs ofIndia. 288 p., 642 figs., Zoological Survey of India,
Calcutta.
Takayasu, K., 1988: Freshwater molluscan fossils fromthe Churia (Siwalik) Group and the rising Himalayas.
In, Kizaki, K. ed., Himalayan Upheaval, p. 81-93, Tsukiji Shokan Inc., Tokyo. (in Japanese)
Takayasu, K., 1992: Paleoenvironmental aspects of the
freshwater molluscs from the Siwalik Group in theArung Khola Area, West Central Nepal. Bulletin of
the Department of Geology, Tribhuvan University,
Kathmandu, Nepal, vol. 2, no. 1, Proceedings of the
Symposium on "Geodynamics of the Nepal Himalaya",p.107-115.
Tokuoka, T., Takayasu, K., Yoshida, M. and Hisatomi, K.,
1986: The Churia (Siwalik) Group of the Arung KholaArea, West Central Nepal. Memoirs of the Faculty of
Science, Shimane University, vol. 20, p.135-21O.
Vokes, H.F., 1935: Unionidae of the Siwalik Series.
Memoirs of the Connecticut Academy, vol. 9, p. 3748, pI. 3.
Vokes, H.F., 1936: Siwalik Unionidae from the collectionof the second Yale North India Expedition. Contribution from the Paleontological Laboratory, Peabody
Museum, Yale University, vol. 8, p.133-141, pI. 10.
Vredenburg, E. and Prashad, B., 1921: Unionidae from the
Miocene of Burma. Records of the Geological Survey of India, vol. 61, p.371-374, pI. 12.
West, R.M., Munthe, J., Lukacs, J.R. and Shrestha, T.B.,
1975: Fossil mollusca from the Siwalik of Eastern
Nepal. Current Science, vol. 44, no. 14, p. 497 -498.
West, R.M., Hutchison, J.H. and Munthe, J., 1991:
Miocene vertebrates from the Siwalik Group, Western
Nepal. Journal of Vertebrate Paleontology, vol. 11,
no. 1, p.108-129.

Trans. Proc. Palaeont. Soc. Japan, N.S., No. 179, pp. 169-174, 2 Figs., September 30, 1995

1992 I Organic components in enameloid of extant andfossil shark teeth
TAROU M. KISO
Paleobiological Laboratory, Geological Institute, Faculty of Science, the University of Tokyo, Tokyo, 113 Japan
Received 6 March 1995; Revised manuscript accepted 18 May 1995
Abstract. Structure and texture of a Pliocene shark tooth have been investigated using histochemical methods and scanning electron microscopy and compared with an extant related species.
As a result it was revealed that the fossil shark tooth contained organic components comparable tothose of the living species, and that collagens and non-collagen proteinaceous molecules in the fossil
enameloid had a characteristic distribution pattern virtually identical to the living counterparts. Thisevidence suggests that fossil shark teeth contain useful information by which to investigate theevolution of developmental regimes of various vertebrate teeth.
Key words: Fossil shark, enameloid, organic components
Introduction
The sequential processes of dental development havebeen revealed by biochemical approaches, and recently
studies on the genetic basis of odontogenesis have been
initiated using molecular biological techniques. Detailed
mechanisms of odontogenesis have been histologicallyresearched since Hertwig (1874). Observations with TEM
of elasmobranch tooth germ have been performed (Sasagawa, 1989; Prostak and Skobe, 1988; Goto, 1978a), anddevelopmental processes of odontogenesis have been
elucidated increasingly at the gene level in mammalian
tooth (Gilbert, 1991). As the dental developmental system
is obviously a product of evolution, investigations from theviewpoint of evolutionary biology, including those on
extinct organisms, should help in the understanding of themechanisms of odontogenesis.
Hard tissues, for example, shells, bones, and teeth, arethe common constituents of fossil records. To know the
relationships between the genetic mechanisms and theresulting structures of mineralized tissues would greatly
help the understanding of extinct fossil organisms.
Previous works on fossil hard tissues focused on themorphological and mineralogical properties of hard tissues, while biochemical and molecular biologicalapproaches on biomineralization have been performed alittle on molluscan shell (de Jong et al., 1974; Weiner etal., 1976; Weiner et al., 1979) and vertebrate teeth (Glimcher et al., 1990). Vertebrates are suitable for this kind ofresearch because of a great accumulation of biochemical
and molecular biological data on extant species.
Among the vertebrates, elasmobranchs are thought tooccupy an important position in the evolution of vertebrate

hard tissues, because of the characteristic structures ofchondrichthyan hard tissues (Prostak and Skobe, 1988).
Body surfaces of an Ordovician heterostracan, Astraspis,
were covered with dermal armor which had a tooth-likestructure, consisting of an enameloid layer, a dentin-likelayer, and a bone-like basement (Halstead, 1974). Goto
(1988) pointed out that the structure constructed withthese three layers is the basic structure in vertebrate hardtissues, which is recognized in selachian scales andteeth. The outer layer of fish tooth is referred to as
enameloid (Poole, 1967), since involvement of mesenchymal participation is suggested in amelogenesis infishes. This unusual phenomenon of the mesenchymal
participation in amelogenesis also makes selachians
intriguing for the study of dental development and evolution.
In this study, both extant and fossil shark teeth were
investigated using histochemical methods. Collagen,non-collagenous proteins, and carbohydrates were
stained in situ in thin sections of enameloid to compare
the structures observed in living and fossil samples.
Observations were also made under scanning electron
microscopy.
Materials and Methods
Extant and fossil shark samples: A specimen of Lamna
ditropis (Family Lamnidae: 1.5 m in total body length) was
obtained in a commercial landing at Kesennuma port,
northeastern Japan. The upper and lower jaws weredetached and immediately thereafter frozen at the port
and stored at - 20'C. An isolated tooth identified as
Carcharocles megalodon belonging to the same family (9170

Tarou M. Kiso

cm in crown height) was collected from the Pliocene
deposits (about 3 m.y.a.) at Iwaibukuro, Chiba, central
Japan, and has been preserved dry in the University
Museum of the University of Tokyo. The dentin anddental base are lacking in this specimen ; the space ofdentin is filled with tuffaceous sandy sediments instead.
The enameloid, on the other hand, is well preserved, witha smooth outer surface comparable to that of living
sharks. The specimen has a grayish appearance due tosecondary pyrite, which occurs as cubic particles incracks. However, EPMA element analysis showed thatthe fossil material preserved fluorapatite (content of F was
about 4%) as in living shark teeth. The thickness of theenameloid measured about 1 mm for the fossil specimen
and 200,um for the living ones.
Scanning electron microscopy: Teeth of the living
shark and a resin - embedded tooth portion of the fossil
shark were cut in longitudinal and labio- lingual directions,and the sectioned surfaces were polished using gradedpowders (No. 6000 carborundum powder, Iwamoto MineralCo., Tokyo). After removal of powders with an ultrasoniccleanser, the polished surfaces were etched with 0.1 N
HCI for one minute, washed with distilled water, air dried
for a few days to dehydrate, and then coated with Pt- Pdalloy prior to scanning electron microscopy (S - 2400S ;Hitachi).
Histochemical preparations: Teeth of the living shark
were cut tangentially and thin - sectioned (100,um groundsections). All specimens of both living and fossil teeth
enameloid were embedded in Bond E (epoxy resin,
produced by Konishi Co., Osaka, Japan) and sectioned(100,um ground sections) almost parallel to the outersurface for observation of non-collagenous material in awide view. As a negative control one of the sections of
the fossil tooth was soaked in a solution of sodium
hypochlorite (10%, v/ v) for several days before the following fixation procedures to destroy organic components.
All thin sections of both the living and fossil samples wereincubated in a neutralized formalin solution (10%, v/ v) atroom temperature overnight to fix the organic components. They were washed with distilled water, etchedwith an aqueous solution of EDT A (0.5 M, pH 8.0) for 6hours, and then fixed with neutralized formalin (10%, v/ v)
once more and washed with distilled water.
Independent from the preparations for thin sectioning,
enameloid tissues were physically isolated from a jaw of
the extant shark, and separation from dentin was performed with mechanical and chemical procedures under an
optical microscope. The isolated enameloid tissues
were placed in neutralized formalin (10%, v/ v) and completely demineralized by decalcification in 1 N HCI for one
week. After washing with distilled water, they were fixedwith neutralized formalin (10%, v/ v), followed by washingwith distilled water. Complete demineralization of a
portion of the fossil tooth left only powder residues, anddid not permit any histochemical analyses.
Collagens and other proteins in the thin sections of both
extant and fossil specimens were stained with Collagen
Stain Kit solution A (Collagen Kenkyu Kai, Kiyose, Tokyo)that includes Sirius red F3BA for collagen staining andFast green FCE for non- collagenous protein (Lopez deLeon and Rojkind , 1985), and carbohydrates stained with
the PAS method using Schiff's reagent. The HCI
demineralized enameloid of living samples was also
stained with Collagen Stain Kit solution A. After staining
the collagen for one hour, samples were incubated in
distilled water at room temperature overnight to thoroughly
remove excess reagents.
Results
Scanning electron microscopy

Bundles of needle- like material (apatite minerals) aredistributed in the enameloid of the extant shark, and they
are arranged longitudinally and parallel to the enameloid
surface (Figure 1a). Sawada (1960) and Kitamura (1960)
referred to this structure as filament- like. Sheet- like
amorphous material arranged vertical to the enameloid
surface and covering the bundles was recognized under
the SEM . The amorphous material obviously was resis-

Figure 1. Scanning electron micrographs of living andfossil shark tooth enameloid. The etched surface ofenameloid from living shark (L. ditropis) (a) and fossil shark(C. mega/odon) (b). Bottom to top in each micrographcorresponds to the direction toward the tooth surface.
Scale bars = 10 ,u m.

992.

Organic components in enameloid of shark teeth

Figure 2. Optical micrographs of thin sections and HCI - demineralized sample of shark teeth enameloid
stained with Collagen Stain Kit except for (e) and (f), which were stained by PAS method. (a) Thin section ofliving shark tooth enameloid . (b) HCI - demineralized enameloid of living shark tooth, this section is parallel tothe plane of enameloid - dentin junction. (c) Thin section of fossil shark tooth enameloid . (d) Thin section offossil shark tooth enameloid with bleach treatment. Collagen and non - collagen proteins are stained red andgreen, respectively. (e) living shark and (f) fossil shark tooth enameloid stained by PAS method. Polysaccharides are stained red . Right to left direction in the left panel (e) corresponds to the direction toward thetooth surface. The fossil shark enameloid (f) was cut parallel to the tooth surface. The left side of photographs of (c), (d), and (f) is to the top of tooth. en : enameloid, de: dentin. Scale bars = 100 jlm.

171

172

Tarou M. Kiso

tant to acid etching. Reif (1973) recognized this material
in SEM observation of a Heterodontus tooth and referred
to it as organic fibrils. Goto (1978a) described a similar
amorphous material observed within shark teeth as collagenous fibers, referred to as Korff's fibrils in a toothgerm.
In the fossil specimen, the arrangement of the bundlesof a needle-like material had a similar appearance to thatobserved in the extant sample (Figure 1b). In the fossil
sample, bundles arranged vertically to the enameloid
surface and the Korff's fibril-like amorphous material wereobserved.

Histochemistry
In thin sections of the extant shark stained by thecollagen staining method (Lopez de Leon and Rojkind,1985), non-collagen proteinaceous parts and collagenous
parts are stained green and red, respectively (Figure 2a).
As mentioned above, living shark enameloid contains
collagenous material known as Korff's fibrils, but thecollagens in the thin section did not exhibit a clear shape,
showing instead a continuously spread pattern in theenameloid tissue (Figure 2a). Non - collagen proteinaceous material displayed a heterogeneous appearance and showed an irregular distribution pattern in thinsection (Figure 2a).
Extant shark enameloid, which was completely
demineralized in 1 N HCI and stained by the same collagen staining method, was indicated by regularly arranged green spots (Figure 2b). In this sample, collagenfibers also showed a regular pattern, with the fibers
crossing each other (Figure 2b).
The fossil sample contains collagenous and non-collagen proteinaceous components, as demonstrated by
optical microscopy of the thin section stained by thecollagen staining method (Figure 2c). Collagens appear
in a heterogeneous distribution pattern (Figure 2c). In
thin sections of the fossil sample, non-collagenproteinaceous components exhibit a spotted pattern, withthe green spots irregularly arranged. In the case of fossilmaterials, it is sometimes experienced that inorganic
materials, possibly minerals produced by diagenesis, arestained green by the staining kit used in this study. In
the negative control which was bleached before fixation,
the green spots were not observed (Figure 2d). The
green spots shown in Figure 2c, therefore, are not inorganic but proteinaceous in nature.
Carbohydrate staining of the thin sections using the
PAS method demonstrated that carbohydrates, possibly
polysaccharides, occur in both living and fossil shark
enameloid (Figures 2e, 2f). The carbohydrates in thefossil tooth had a somewhat different distribution patternfrom that of the living sample. In the former, carbohydrates were often recognized at the boundary of themineral bundles, while in the latter, they showed a patched distribution pattern regardless of the mineral bundles.

Discussion
Recently, it has been revealed that non-collagenous
proteins play an important role in amelogenesis. Termine
et al. (1980) clarified, using biochemical analyses, that
non-COllagenous proteins, proline-rich amelogenin andacidic enamelin exist in bovine enamel. Subsequently,
cDNA sequences of the amelogenin precursor genes ofvarious mammals were determined (Snead et al., 1987;
Shimokawa et al., 1988). Fincham et al. (1991) argued, on
the basis of the determined amelogenin sequences that
post-secretory processing cleaves amelogenin precursors
in several steps to control the rates of mineralization
during odontogenesis. Compared to amelogenin,
enamelin is poorly characterized by molecular biologicalmethods. This may partly be due to the fact that theenamelin content in mammalian enamel is considerably
lower than that of amelogenin (Termine et al., 1980).
Selachians may provide an advantage in the study ofenamel in, because it is suggested that enamelin-likeprotein is the predominant component of the non-collagenous enameloid proteins (Herold et al., 1988; Kemp,
1985; Slavkin et al., 1983a). But non-collagenous matrix
proteins of fish enameloid have not been characterized on
the level of DNA sequence yet and are confusing for thefollowing reasons. Antibodies prepared against mammalian enamel in and amelogenin have detected enamel
proteins in situ in shark teeth, cyclostome horny cap, andbony fish teeth (Herold et al., 1980). Slavkin et al. (1983a)
demonstrated using electrophoresis that shark teeth andhagfish caps contained a proteinaceous component that
had a molecular weight comparable to enamelin.
Amelogenin too was detected in amelogenesis of selachian tooth with polyclonal antibody against murine
amelogenin (Slavkin et aI, 1983b). However, Herold et al.
(1988) and Ishiyama et al. (1994) claimed by immunohistochemical methods that there existed not amelogenin but
only enamelin in fish enameloid matrix. According toanatomical study with TEM enameloid matrix proteins
were secreted by odontoblasts in spite of ameloblastic
secretion of mammalian enamel in and amelogenin(Sasagawa and Akai, 1992). Prostak and Skobe (1988) by
TEM observation recognized a non-collagenous fiber
unique to elasmobranch tooth, "Giant fiber", secreted byodontoblasts in the developing enameloid matrix. It isalso supposed that the giant fiber is a product of ameloblastic secretion as enamelin (Kemp, 1985).
Non-collagenous proteins had a heterogeneous patched distribution in living shark enameloid (Figure 2a),while the completely demineralized enameloid (Figure 2b)
had a pattern of regularly arranged green spots. This
result poses a problem in differently prepared samples.
The difference of the observed structures between thesample completely demineralized with HCI and the thinsections etched with EDTA is also the case for collagens.
Figure 2b shows a regularly knitted structure of collagenfibers, but the thin section of the same living materialindicates an irregular structure of collagens. These
differences are attributed to differences in the degree of992.

Organic components in enameloid of shark teeth

demineralization and in cutting directions.
It is likely that the green stained non-collagenous
proteins in the living shark enameloid represent enamelinlike protein, because the enamelin-like protein is known
as the predominant component of the non-collagenous
enamel proteins in selachians (Heroid et al., 1988; Kemp,
1985; Slavkin et al., 1983a). Optical micrography of thefossil sample in thin section also reveals a spotted distribution of the non-collagenous proteins (Figure 2c). It issuggested that this proteinaceous material is homologous
to the 'enamelin-like' protein observed in the living sample, because they have the same distribution pattern.
From SEM observations, it was revealed that theenameloid of fossil shark does not differ from that of living
shark in the arrangement of the amorphous materials.
Amorphous material in the living sample can be identified
as Korff's fibers (Figure 1a) in a tooth germ. Garant (1970)
recognized collagen fibers between palisade aggregations of apatite mineral in a developing enameloid on thebasis of TEM observation. It is supposed that this amorphous material is identified as the interpalisade collagenfiber. The amorphous materials in the fossil sample,
therefore, have the texture of the collagenous Korff's
fibers. They were recognized at the boundaries of bundles (Figure 1b). The distribution pattern of these materials is clearly distinguished from that of the non-collagenproteinaceous materials observed in Figure 2. Thin sections stained by PAS method indicate that polysaccharides exist at the boundaries of bundles (Figure 2f). It is,therefore, likely that the amorphous materials in the fossil
sample represent polysaccharides, although it may also
be possible that they represent collagens, since collagens
were detected histochemically in the fossil thin section(Figure 2c).
According to previous researches on both fossil andextant materials with biochemical and histochemical
techniques Samata (1988) and Glimcher et al. (1990) reported non-collagenous enamel proteins preserved in toothof a Pliocene (3 m. y. a.) elephant and a Cretaceous (105m. y. a.) crocodile and analyzed their amino acid composition. Concerning lower vertebrates, on the basis of staining results Isaacs et al. (1963) postulated that Paleozoic
primitive vertebrate fossils preserve collagen and polysaccharides in dentin. Iwata and Uozumi (1970) showed
TEM photographs of morphologically degraded collagenin Pliocene lamnid shark teeth. Goto (1978b) detected
non-collagenous protein on the basis of amino acidcomposition of the extract from Miocene shark enameloid.
This study provided new data that showed preservation ofcollagen, non-collagenous proteins, and polysaccharides
in situ in fossil teeth.
As the non-collagen proteins are suspected to beenamelin-like proteins, in situ immunohistochemical
research with antibodies may be the logical next step toconfirm the results obtained in this study. Based on
histochemical observations, together with further biochemical characterizations of constituent proteins, thestudies on fossil enameloid may provide important information in clarifying mechanisms of odontogenesis and173

evolution of animal hard tissues.
Acknowledgments

I am grateful to Drs. K. Tanabe, T.Oji, and K. Endo for
critical reading of the manuscript, to Dr. I. Hayami and Dr.
Taniuchi for encouragement during research, and to Dr.
Goto for discussion. The specimens of extant shark
were provided by Oshima Fishery Co. Ltd. (1-3-18,
Benten-cho, Kesennuma, Miyagi Prefecture, Japan).
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63-64.
Fincham, A.G., Hu, Y., Lau, E.C., Slavkin, H.C. and Snead,
M. L., 1991: Amelogenin post-secretory processing
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Garant, P.R., 1970: An electron microscopic study of thecrystal-matrix relationship in the teeth of the dogfish
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Gilbert, S.F., 1991: Developmental Biology (3rd edition). p.
586-587. Sinauer Associates, Massachusetts.
Glimcher, M.J., Cohen-Solal, L., Kossiva, D. and de Ricqles, A., 1990: Biochemical analyses of fossil enameland dentin. Paleobiology, vol. 16, no. 2, p.219-232.
Goto, M., 1978a: Histogenic studies on the teeth of leopard shark (Triakis scyl/ia). Journal of StomatologicalSociety of Japan, vol. 45, p.527-584.
Goto, M., 1978b: Histological and biochemical studies on
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Dental Journal, vol. 4, p.85-104.
Goto, M., 1988: Development of dermal tooth and jaw
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Halstead, L.B., 1974: Vertebrate Hard Tissues. p.58-60.

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207, p.1357-1358.
Herold, R., Rosenbloom, J. and Granovsky, M., 1988:
Phylogenetic distribution of enamel proteins: Immunohistochemical localization with monoclonal
antibodies indicates the evolutionary appearance ofenamel ins prior amelogenins. Calcified Tissue International, vol. 45, p. 88-94.
Hertwig, 0., 1874: Ueber Bau und Entwickelung derPlacoidschuppen und der Zahne der Selachier.
Jenaische Zeitschrift fUr Naturwissenschaft, vol. 8, p.
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Issacs, W.A., Little, K., Currey, J.D. and Tarlo, L.B.H., 1963 :Collagen and a cellulose-like substance in fossil
dentin and bone. Nature, vol. 197, p.192.
Ishiyama, M., Inage, T., Shimokawa, H. and Yoshie, S.,
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Tarou M. Kiso

proteins in dental matrix of certain fishes. Bulletinde /'Institute Oceanographique, Monaco; n° special
14,. vol. 1, p.175-182.
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Kemp, N.E., 1985: Ameloblastic secretion and calcification of the enamel layer in shark teeth. Journal ofMorphology, vol. 184, p. 215-230.
Kitamura, M., 1960: Optical and electron microscopy of
the teeth of Isuropsis glauca (Muller and Henle).
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2375-2388.
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Woo, S.L.C. and Slavkin, H.C., 1985: DNA sequence
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Trans. Proc. Palaeont. Soc. Japan, N.S., No. 179, pp. 175-183, 3 Figs., September 30, 1995

Early to Middle Miocene molluscan fossils from the
Megami and Ebie limestones in Shizuoka Prefecture andtheir implications for the formation of a Miocene
coral-algal reef within the Japanese faunal realm
TOMOWO OZAWA\ KEISUKE INOUE l and SUSUMU TOMIDA 2[Department of Earth and Planetary Sciences, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-01 Japan
2Chukyo Gakuin University, Nakatsugawa, Gifu, 509-91 Japan
Received 15 May 1995; Revised manuscript accepted 15 August 1995
Abstract. Eight fossil molluscan species, including Cryptopecten yanagawaensis (Nomura andZinbo) and Turbo (Marmarostoma) mekamiensis Nishiwada, are described on the basis of material
obtained from the late Early to early Middle Miocene Megami and Ebie limestones in the Sagara
district, Shizuoka Prefecture, Japan. Cryptopecten yanagawaensis has been recorded from late
Early to early Middle Miocene formations in Japan. The occurrence of this species indicates that thereef limestones in the Megami Formation were formed within the Japanese faunal realm in Miocenetime.
In this paper some comments are made on the origin and sedimentary environments of thelimestones in the Megami Formation.
Key words: Molluscan fossils, Miocene, coral-algal reef, Megami and Ebie Limestones, Japan
Introduction

A number ofallochthonous reef limestone blocks, ranging in diameter from a centimeter to more than a hundred
meters, occur in the abyssal turbidite sequence of the
Early/Middle Miocene Megami Formation in the Sagara
district, Shizuoka Prefecture, central Japan. The
Megami and Ogami limestones are among the larger ofthese blocks. They have long been of special interest to
paleontologists, because they yield abundant and wellpreserved Miocene shallow marine fossils such as crustose coralline algae (Nishiwada, 1894; Ishijima, 1933;
Iryu and Sasazawa, 1989), larger foraminifers (Hanzawa,
1943; Matsumaru, 1971), hermatypic corals (Eguchi andMori, 1976), molluscs (Nishiwada, 1894) and decapod
crustaceans (Karasawa, 1993).
The origin of the limestones has also been debatedamong geologists and paleontologists, who have madedifferent interpretations of the sedimentary setting of thelimestones and different scenarios for the formation process of these allochthonous limestone blocks.
Konishi et a/. (1988) and Sugiyama (1992) suggested that
the Megami and other limestone bodies were originallyformed on a seamount in an ocean realm and are now
found as allochthonous blocks in the Miocene ac-

cretionary complex.
On the contrary, Nakamori et a/. (1991) reported that thelimestones had formed initially on a shallow shelf of theisland arc, and were then transported to a deeper sedimentary basin, such as a trough on the continental slope
or a trench floor.
During field survey of the Sagara district, the seniorauthor found well-preserved pectinid fossils from a small
limestone named the Ebie Limestone and also from the
Megami Limestone. As a result of our taxonomic investigation, the fossils are identified as Cryptopecten yanagawaensis (Nomura and Zinbo), Chlamys sp. A andChlamys sp. B. In this paper, the molluscan fossils from
the Megami and Ebie limestones are described systematically. In addition, some comments are made on theorigin and sedimentary environments of the limestonelithology and the zoogeographical and ecological information provided by the molluscan species.
Geologic notes on the fossil localities

Neogene marine sediments are extensively distributedin the Sagara district, Shizuoka Prefecture, central Japan.
They are classified into the Megami Formation, the Sagara
Group and the Kakegawa Group, in upward sequence.

176

Tomowo Ozawa et a/.

The Megami Formation is narrowly distributed as an inlier
in the Sagara Group, forming the core of a southwesterly
plunging anticline called the Megami Anticline. It consists mainly of mudstone and fine-grained sandstone inwhich a number of allochthonous reef-limestone blocks
are contained. Benthonic foraminifers indicating an
abyssal environment occur in the mudstone (Nakamori eta/., 1991). The formation is assigned to a late Early toearly Middle Miocene age (Blow's N8 to N9 Zones) basedon the index planktonic foraminifers found in the mudstone (Saito, 1963; Oda, 1971 ; Ujiie, 1975). The age ofthe limestone blocks is also determined as 17-16 Ma bymeans of calcareous nannoplankton and larger foraminifers (Nakamori et a/., 1991).
The molluscan fossils described in this paper wereobtained from the limestones at two localities as described below.
Ebie Limestone: A small limestone block approximately 10 m in diameter crops out in the valley to the northof Ebie, Sagara-cho, Shizuoka Prefecture (Lac. 1 in Figure1). Light brown calcarenite yielded commonly
Cryptopecten yanagawaensis (Nomura and Zinbo) andLegendD

Alluvial and terrace
deposits

Sugegaya Formation
Megami Formation
Limestone

I

I

/

o

Fault

lkm

I
138 12' E
0

Figure 1. Index map showing fossil localities in the Megami Formation.
on the geologic map of Nakamori et a/. (1991).

The fossil localities are plotted993.

Miocene molluscs from Megami and Ebie limestones

Chlamys sp. A together with abundant larger foraminifers
such as Nephrolepidina nipponica (Hanzawa), Miogypsina
kotoi Hanzawa, and Homotrema rubrum (Lamarck).
Megami Limestone: The fossil locality is a cliff in thelimestone quarry of the Megami Limestone at Taisyaku yama, Megami, Sagara- cho (Loc. 2 in Figure 1). Light,
buff- colored coralline algal limestone yielded the following molluscs: Turbo mekamiensis Nishiwada, "Cypraea "sp., Conus sp., Chlamys sp. A, Chlamys sp. B, Spondylus
sp. and Periglypta sp. cf. P. reticulata (Linneaus).
Origin and sedimentary setting of the limestones

The Megami and Ogami limestones are considered tobe coral - algal reef limestones which formed in a warm
shallow marine environment during the Miocene (Eguchi
and Mori, 1976; Konishi et a/. , 1988; Iryu and Sasazawa,1989). They consist mainly of hermatypic coral - coralline

177

algal boundstone with fine - grained sediments as interstitial fillings . Among the reef- building organisms, crustose coralline algae including such species as Lithothamnium ramosissimum, Mesophyllum erubescens and Archaeolithothamnium megamiensis are major frameworkcontributors to the Megami coral - algal reef, together withhermatypic corals of the order Scleoderma including suchgenera as Favia, Echinophyllia, Cyphastrea, Acropora,
Polites, Goniopora and Stylophora (Ishijima, 1960 ; Eguchi
and Mori, 1976; Iyru and Sasazawa, 1989). Irregularly
shaped coralline frameworks are often filled with fine grained packstones and wackestone which yield suchmolluscan fossils as Turbo (Marmarostoma) mekamiensis ,"Cypraea " sp., Conus spp., Chlamys spp., Spondylus sp.
and Periglypta cf. reticulata. A decapod assemblage
characteristic of reef and lagoonal environments occurs
together with these molluscs (Karasawa, 1993).
In contrast to the litho- and bio- facies of the Megami

ca. 16 Ma. .. . . . . .
. . . . . . . . . .. . . . . . . . . . . . . . . .
. . . . . . . .. . . . . . . .

.... . . .....
. . . . . . . .. . . . . . .
. . . . . . . . . . . . . . . . .. . . . .. . . . .... . .
. . . . . . . . . . . . . . . . . . . ... . .. . .
. . . . . . . . . . . . . . . . . . . . . . ... . . .
. . . . . . . . . . . . .. . . . . . . . . . .
. . . . . . . . . . . .... .

Figure 2. Paleogeographic map around the Japanese Islands at ca. 16 Ma, showing the occurrence of
Cryptopecten yanagawaensis (black circles). Modified from Pickering , Underwood and Taira (1993).

178

Tomowo Ozawa et al.

Limestone, the Ebie Limestone is entirely composed of
detrital limestone (calcirudite and calcarenite), which isconsidered to have been formed on the fore-reef slope ofthe Megami reef. In the limestone, two pectinids,
Cryptopecten yanagawaensis and Chlamys sp. A, occur inlarge numbers together with abundant larger foraminifers,
including Nephrolepidina nipponica and Miogypsina kotoi.
Nakamori et al. (1991) reported the occurrence of granules
and pebbles of shale, siliceous sandstone and chert in the
Ebie Limestone, and also the occurrence of granule- topebble-sized gravels of sandstone and shale from the
Oumagadani Limestone. However, careful petrographic
examination of these rocks revealed that they are weathered dacitic volcanic rocks and not sedimentary rocks.
Consequently, no terrigenous materials have been confirmed in the Megami, Ebie and Oumagadani limestones.
This fact strongly suggests that the limestones wereformed in an open-sea environment. Makiyama (1963)
reported the occurrence of a mass of basalt close to the
Ogami Limestone. We also confirmed the occurrence ofan allochthonous block of basalt in the siltsone of the
Megami Formation. The lithologic association of reeflimestone and basalt strongly implies that the limestones
were originally formed on a basaltic seamount in an opensea environment.
Recent geotectonic studies have elucidated the plate
tectonic evolution of the Philippine Sea (Hill et al., 1993).
During the Oligocene to Miocene (ca. 27-14 Ma), backarc
rifting occurred behind the lzu-Bonin Arc to produce the
Shikoku Basin and Kyushu-Palau Ridge (Pickering, Underwood and Taira, 1993). The Megami coralline reef
was formed most likely on a basaltic seamount in thenortheastern part of the Shikoku Basin standing close to
the proto-Japanese Islands during a period of remarkablewarming of the marine climate about 16 Ma (Sugiyama,1992).
Present knowledge suggests that the distribution of
Cryptopecten yanagawaensis is confined to the late Early
to early Middle Miocene of Honshu, Japan. The occurrence of this species is significant for the origin andsedimentary setting of the Megami and other limestones,
because it provides the evidence that the coral-limestone
was formed within the Miocene Japanese faunal realm(Figure 2).
In a phase of rapid sea-floor spreading in the Sea ofJapan, central and southern Honshu rotated clockwise
during 16-15 Ma. This clockwise rotation resulted in thecollision of the sea mounts with the Honshu Arc. Reef
limestones like the Megami Limestone and pillow basalts
like the Takakusayama Basalt which formed the uppersurface of the seamounts were scraped off to form an
accretionary complex in a trench area.
Summarizing the above short discussion, it may beinferred that the Megami and other limestones wereoriginally formed on a seamount in the northeastern part of
the Philippine Sea close to Central Japan and accreted to
the Honshu Arc during the opening of the Sea of Japan.

Systematic descriptions
Class Bivalvia Linnaeus, 1758
Order Ostreoida Ferussac, 1822
Family Pectinidae Rafinesque, 1815
Subfamily Chlamydinae Korobkov, 1960
Genus Cryptopecten Oall, Bartsch
and Rehder, 1938
Type-species.-Cryptopecten alii Oall, Bartsch and
Rehder, 1938 [=Pecten (Chlamys) bullatus Oautzenberg
and Bavay, 1912J. Hawaii, Philippines and Japan, Late
Pliocene to Recent.
Generic diagnosis.-see Hayami (1984, p.90-91).

Cryptopecten yanagawaens;s (Nomura and Zinbo)
Figures 3-1-4
Pecten (Aequipecten?) yanagawaensis Nomura and Zinbo,
1936, p. 337, pI. 20, figs. 2a, b.
Pecten (Aequipecten) yanagawaensis Nomura and Zinbo.
Nomura, 1940, p.19, pI. 1, figs. 10-13.
Cryptopecten yanagawaensis (Nomura and Zinbo). Masuda,
1958, p.189, pI. 27b, figs. 1-8; Itoigawa, Shibata andNishimoto, 1974, p.67, pI. 11, figs. 6-9; Taguchi, Ono andOkamoto, 1979, pI. 4, figs. 1, 2; Hayami, 1982, p. 235;
Hayami, 1984, p.113-115, pI. 8, figs. 6-9; Sato, 1984, p.
257, pis. 36, 37; Chijiwa and Tomita, 1985, pI. 41, fig. 7 ;Masuda, 1986, pI. 1, fig. 5; Sato, 1991, p.70-78, pis. 12, 13.
Aequipecten yanagawaensis (Nomura and Zinbo). Masuda,
1962, p.192, pI. 26, fig. 8; Masuda and Takegawa, 1965,
pI. 1, figs. 12, 13; Masuda, 1973, pI. N-54, figs. 14-16;
Ogasawara, 1976, p.44, pI. 3, figs. 3, 6; Katto and
Masuda, 1978, pI. 5, figs. 4, 5; Itoigawa, Shibata, Nishimoto and Okumura, 1981, pI. 7, figs. 2, 3; Itoigawa,Shibata, Nishimoto and Okumura, 1982, p. 46; ? Shikama,
1973, p. 190, 194.
Type and type locality.- The holotype (Saito Ho-on Kai
Museum, Sendai, Reg. No. SM8553; Nomura and Zinbo,
1936, p.337, pI. 20, figs.2a, 2b) from the early Middle
Miocene Yanagawa Formation at a river cliff of the
Abukuma-gawa, southwest end of Yanagawa Park,
Yanagawa town, Fukushima Prefecture, north Japan(3T51.1'N, 140·36.1'E). length, 21.5 mm; height, 20 mm
high; depth, 5 mm.
Species diagnosis.-see Hayami (1984, p.113).
Materia/s.-Four illustrated specimens (Earth Sciences,
Nagoya Univ. Reg. No. ESN2536-2539) and more than ten
poorly preserved specimens from the Lower to Middle
Miocene Ebie Limestone at Sagara town, Shizuoka Prefecture, central Japan.
Description.-Shell moderate in size, slightly inflated,nearly equiconvex, height subequal to length; equilateralor somewhat inequilateral, radiately ribbed, apical angle ofdisk approximately 100·; ears moderate in size, anterior
one slightly larger than posterior; anterodorsal and posterodorsal margins of disk straight or slightly concave,byssal notch moderate in depth. Outer surface of disk
ornamented with 21-24 elevated and rounded radial ribs,

993.

Miocene molluscs from Megami and Ebie limestones

Figure 3. All figures in natural size unless otherwise stated. 1- 4. Cryptopecten yanagawaensis (Nomura
and Zinbo) Loc. 2 (Ebie Limestone). 1: left valve, ESN 2536,2 : left valve, ESN 2537, 3 : left valve, ESN 2538,
4 : left valve, ESN 2539. 5. Chlamys sp. A, right valve, ESN 2540, Loc. 1 (Megami Limestone) x 2. 6 - 8 .
Chlamys sp. B. 6 : right valve, ESN 2541 , Loc.2 (Ebie Limestone), 7: right valve, ESN 2542, Loc.2 (Ebie
Limestone), 8: left valve, ESN 2543, Loc. 1 (Megami Limestone). 9. Spondylus sp., left valve, ESN 2544, Loc.
1 (Megami Limestone), X O.75. 10-11. Periglypta sp. cf. P. reticulata (linnaeus). 10: inner mold of left valve,Loc. 1 (Megami Limestone), 11: right valve, Loc.1 (Megami Limestone). 12-14. Turbo (Marmarostoma) mekamiensis Nishiwada. 12: Loc. 1 (Megami Limestone) ; 12a: apertural view, 12b : upper side view, 13: adapertural view, ESN 2545, Loc. 1 (Megami Limestone), 14: a part of last whorl showing spiral cords and interstitial
threads, ESN 2546, Loc. 1 (Megami Limestone). 15. "Cypraea " sp., adapertural view, Loc.1 (Megami Limestone).

179

Tomowo Ozawa et a/.

180

each of which consists of a comparativaly narrow central
ridge and a pair of relatively narrow hollow parts; ribinterspace marked with a number of fine radial threads.
Radial ribs are weakly impressed on the inner surface ofthe shell, and a relatively large semi-circular adductor
muscle scar is observed.
Dimensions (in mm) and number of radial ribs. Specimen ESN 2536 ESN 2537 ESN 2538 ESN 2539
Valve
left
left
left
left
Height
24.7
24.8
21.6
18.8
Length
26.2
26.1
22.0
19.6
Depth
3.6
3.9
3.5
Radial ribs
22
24
20
Remarks.-The specimens from the Ebie Limestone,
here assigned to Cryptopecten yanagawaensis, are wellcomparable in size, number of radial ribs, and other shellcharacteristics with the type and other specimens of C.
yanagawaensis from late Early to early Middle Miocene
formations in central and northern Honshu. The present
species is very akin to Cryptopecten hsintienensis
Masuda and Huang, 1993, described from the Middle
Miocene Kuanyinshan Sandstone, northern Taiwan, butdiffers in having a larger and less inflated equiconvex
shell. The stratigraphic occurrences of C. yanagawaensis seem to be restricted to the upper Lower to lower
Middle Miocene in north and central Honshu. Specimens from the Uematsu Formation in the Kushimoto
district, Kii Peninsula, are also undoubtedly referable tothis species.
Occurrence.-Abundant in the Ebie Limestone.
Known distribution.-This species is known from the
Yanagawa Formation at Yanagawa, Fukushima Prefecture(type locality), the Moniwa Formation at Moniwa andJunishin (Masuda, 1958; Sato, 1991), Taira Member of the
Kanagase Formation of Ogawara (Masuda and Takegawa,1965) near Sendai, Miyagi Prefecture, the Nagaoka Formation, Tochigi Prefecture (Sato, 1991), the Tsugawa Formation, Niigata Prefecture (Tsuda, 1965), the Kurosedani
Formation, Toyama Prefecture (Tsuda, 1965), the Sunakozaka Formation at Higashi-ichise near Kanazawa, Ishikawa Prefecture, (Ogasawara, 1976), the Akeyo (Shukunohora Sandstone) and Oidawara Formations at Mizunami,
Gifu Prefecture (Itoigawa, Shibata and Nishimoto, 1974),
the Onuma Formation, Mie Prefecture (Chijiwa andTomita, 1985), the Uematsu Formation at Kushimoto,
Wakayama Prefecture, and the Bihoku Group in Okayama
Prefecture (Taguchi, Ono and Okamoto, 1979).
The present report from the late Early to early Middle
Miocene Ebie Limestone provides additional occurrence
data on this species.
Geologic age.-Late Early Miocene to early Middle
Miocene (Blow's N8 and N9 Zones).
Genus Chlamys Reding, 1798
Chlamys sp. A
Figure 3-5

Descriptive remarks.-A small right valve was obtained
from the Megami Limestone. Shell is small and moderately convex with 13 main ribs and additional secondary
ribbing. Ears are very unequal. Considering only important shell characters, this species is similar to Chlamys(Chlamys) zeelandona (Hertlein) from North Island, New
Zealand.
Occurrence.-Rare in the Megami Limestone.
Chlamys sp. B
Figures 3-6-8

Descriptive remarks.-More than five specimens wereobtained from the Ebie Limestone (Loc. 1) and three specimens were collected from the Megami Limestone. Shellis small to medium, depressed, slender, and slightly
oblique. Ears are unequal. Surface of disk is sculptured by numerous radial riblets with no scale in interspaces.
Occurrence.-Common in the Megami and Ebie limestones.
Family Spondylidae Gray, 1826
Genus Spondylus Linnaeus, 1758
Spondylus sp.
Figure 3-9

Descriptive remarks.-An incomplete left valve wasobtained from the Megami Limestone. The valve israther large and elliptical. The surface is sculptured bynumerous radiating striae which are nearly smooth. In
the surface sculpture of the shell, this species is similar to
Spondylus sanguineus Dunker but differs in having amuch larger shell. It is also allied to Spondylus
anacanthus Mawe but is distinguished from that species
in lacking spines.
Occurrence.-Rare in the Megami Limestone.
Family Veneridae Rafinesque, 1815
Genus Periglypta Jukes-Browne, 1914
Periglypta sp. cf. P. reticulata (Linnaeus)
Figures 3-10,11

Descriptive remarks.-Four poorly preserved specimens
comparable to Periglypta reticulata came from the Megami
Limestone. The shells of these specimens are rather
thick, solid and heavy, inflated and roundly quadrate inshape. The posterodorsal margin is quadrately angled.
The umbo is situated anteriorly. Strong radial ribs arecrossed by concentric cords forming a coarse reticulationon the surface.
Occurrence.-Frequent in the Megami Limestone.
Class Gastropoda Cuvier, 1797
Order Archaeogastropoda Thiele, 1925
Family Turbinidae Rafinesque, 1815
Genus Turbo Linnaeus, 1758
Subgenus Marmarostoma Swainson, 1829

993.

Miocene molluscs from Megami and Ebie limestones

Turbo (Marmarostoma) mekamiensis Nishiwada, 1894

Figures 3-12~14

Type-specimen.- Turbo (Marmarostoma) mekamiensis
Nishiwada, 1894, p.139, pI. 5, figs. 5a, 5b (Holotype, Univ.
Mus. Univ. Tokyo, Reg. No. CM15259); Nishiwada, 1895,
p. 240, pI. 29, figs. 5a, 5b (see also Nishiwada, 1894).
Materia/s.-Eleven topotype specimens including one
registered specimen (ESN 2545) were considered in thefollowing description.
Description.-Shell is medium-sized, heavy, globular
and turbiniform, and is composed of four rounded whorls
that are separated by shallow sutures with channels.
Shoulder is not angled. Whorls are spirally sculptured
with prominent, raised and rounded spiral cords, which
number 12 on the last whorl, and narrow interstitial threads
which are finely scaled (Figure 3-13). Subsutural spiralcords are a little wider than others. The basal lip near
the columella is rather thick and slightly ridged. Apertureis nearly circular. Umbilicus is closed.
Remarks.- The present specimens are morphologically
identical with Turbo (Marmarostoma) mekamiensis Nishiwada, 1894, also described from the Megami Limestone.
It closely resembles T. (M.) setosus Gmelin, which lives in
the central Pacific south of the Bonin and Okinawa
Islands, but differs from that species in having a smaller
number of spiral cords that are more flat-topped. It
resembles Turbo (Marmarostoma) argyrostoma Linnaeus,
but is distinguished from that species in having a smaller
shell, a more rounded shoulder and shallower suture.
Measurements (in mm).Specimen
Hagima coil.
Height of shell
44.0
Width
42.0
Height of body whorl
28.7
Height of aperture
26.0
Apical angles
85

ESN 2545
38.0
38.3
22.0

0

Occurrence.-Common in the Megami Limestone (typelocality). Late Early to early Middle Miocene.
Order Mesogastropoda Thiele, 1925
Family Cypraeidae Rafinesque, 1815
Genus Cypraea Linnaeus, 1758
"Cypraea" sp.

Figure 3-15

Descriptive remarks.- This species is mostly found as
casts in the Megami Limestone. The illustrated specimen is a medium-sized, pyriform-ovate shell reaching 37
mm in length. It certainly belongs to Cypraea (s.l.) but the
species identification is difficult owing to the poor preservation.
Occurrence.-Rare in the Megami Limestone.

181

Acknowledgments

We express our thanks to Mr. Tadao Matsuura, School
Master of the Hagima Primary School in Sagara town,
Shizuoka Prefecture for his permission to examine thefossil collection stored in the school. Our sincere thanks
are extended to Dr. Koichiro Masuda, Emeritus Professorof the Miyagi University of Education for his help in
identification of pectinid fossils. Thanks are also
extended to Dr. T. Agata and Mr. Takenori Kato, Laboratory of Petrology, Department of Earth and Planetary
Sciences, Nagoya University, who assisted us in petrographic study. We are also grateful to Dr. Richard W. Jordan, Department of Earth and Environmental Sciences,
Yamagata University for his reading the manuscript. This
study was supported in part by Grant-in-Aid for Scientific
Research from the Ministry of Education, Science andCulture, project no. 05304002.

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Miocene molluscs from Megami and Ebie limestones

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Megami R"t$, Taishaku-yama 'iiHRilJ, Ebie w~tI, Ogami ~t$, Oumagadani 1lfIJf.!fr?":fr,
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Trans. Proc. Palaeont. Soc. Japan, N.S., No. 179, pp. 184-192,6 Figs., September 30, 1995

I 994 I Cephalopod fauna of the Nakadaira Formation(Lower Permian) in the Southern Kitakami Massif,
Northeast Japan
MASAYUKI EHIRO
Institute of Geology and Paleontology, Faculty of Science, Tohoku University, Sendai, 980-77 Japan
Received 19 May 1995; Revised manuscript accepted 3 August 1995
Abstract. Eight species referable to six genera of nautiloids and two species belonging to two generaof ammonoids are described from the Lower Permian Nakadaira Formation in the Southern Kitakami
Massif, Northeast Japan. These nautiloids are Tainoceras, Foordiceras, Pleuronautilus, Aphelaeceras, Parastenopoceras and Stearoceras. Pleuronautilus yahagiensis is a newly proposed species.
Ammonoids are Agathiceras and Artinskia. Agathicaras dominates the fauna.
Key words: Cephalopoda, Lower Permian, Nakadaira Formation, Southern Kitakami
GeologiC setting

Introduction
In the Kitakami Massif, unlike the Middle and Upper
Permian, cephalopod fossils are very rare in the Lower
Permian. Only four species of nautiloid and one speciesof ammonoid have hitherto been reported. They are
Tainoceras kitakamiense Hayasaka from the uppermost
part of the Sakamotozawa Formation (Motoiwazawa
Sandstone Member; Murata, 1971), Metacoceras sp. fromthe Rodai Formation (Yabe and Mabuti, 1935), Tainoceras
abukumaense Hayasaka from the Nakadaira Formation(Ehiro, 1977), Tylonautilus cf. permicus Hayasaka from the
Nishikori Formation (Ueda, 1963) and Agathiceras cf.
brouweri Smith from the Sakamotozawa Formation (Koizumi, 1975). The last three species were only listed andno description was given.
Recently, the present author paleontologically reexamined the above-listed T. abukumaense (=Pleuronautilus yahagiensis sp. nov. of this paper) and reinvestigated the Nakadaira Formation at the fossil localities.
In the course of this study, some additional cephalopod
fossils were collected from the locality from which T.
abukumaense was first reported, 500 m northwest of
Nakadaira (Loc. A, Figure 1), and also from a new locality
on a peak (482 m above sea level), about 500 m to thenortheast of Natsugayoi (Loc. S, Figure 1) and 2 km northof Nakadaira, both in Yahagi-town, Rikuzen-Takata City,
Iwate Prefecture.
The purpose of this paper is to describe cephalopods
from the Nakadaira Formation and to discuss a cephalopod biostratigraphy of Permian strata in the Southern
Kitakami Massif.

A.

General aspect of the Nakadaira Formation
The Nakadaira Formation is distributed in the Nakadaira
district on the western side of the Hizume-Kesennuma
Fault, which traverses the Southern Kitakami Massif witha NNW-SSE trend (Figure 1). The formation is composedof a thick (about 1,000 m) series of alternating beds ofconglomerate, sandstone, shale and limestone, which has
been complicated owing to folding and faulting (Ehiro,
1977). It unconformably overlies the Lower-Middle Carboniferous Kidoguchi Formation (Ehiro and Mori, 1993) andis in fault contact with the Lower Carboniferous Magoshi
Formation and Lower-Middle Carboniferous Senbakaya
Formation, both distributed on the eastern side of the
Hizume-Kesennuma Fault. The Nakadaira Formation is
conformably overlain by the Middle-Upper Permian Ochiai
Formation, which is composed mainly of shales withsubordinate amounts of sandstone, conglomerate andlimestone. The Nakadaira Formation yields fusulinids
such as Robustoschwagerina schel/wieni Hanzawa andChalaroschwagerina vulgaris (Schellwien and Dyhrenfurth)from the lower-middle part and Pseudofusulina ambigua(Deprat) and P. fusiformis (Schellwien and Dyhrenfurth)from the upper part (Ehiro, 1977). These fusulinids indicate that the formation is roughly correlatable with thetype section of the Sakamotozawan Series in the Hikoroichi district of the Southern Kitakami Massif.
The standard of reference sequence of the Sakamotozawa Formation has been divided biostratigraphically into
five zones based on fusulinids (Kanmera and Mikami,1965). They are in ascending order the Zellia nunosei,
Monodiexodina langsonensis, Pseudofusulina vulgaris

994.

Cephalopods from Lower Permian Nakadaira Formation

185

nautilus yahagiensis sp. nov., P. sp., Aphelaeceras cf.
falciferum Yin, Parastenopoceras sp. and Stearoceras sp.
Ammonoid.-Agathiceras sp.
The impure limestone occurring just above the shale
yields such fusulinids as Rugosofusulina alpina (SchelIwien) and Pseudofusulina bona? Rosovskaya. R. alpina
is very abundant. A limestone bed, about 40 m above theshale, contains Chalaroschwagerina vulgaris (Schellwien
and Dyhrenfurth), Pseudofusulina? sp., Parafusulina cf.
multiseptata (Schellwien) and Rugosofusulina aft. complicata (Schellwien). The horizon of cephalopod fossils
at Nakadaira is therefore correlated with the upper part of
the Lower Sakamotozawa Formation, bacause
Rugosofusulina alpina, found just above the cephalopod
horizon, is restricted to the upper part of the Monodiexodina langsonensis Zone in the type Sakamotozawa
Formation (Kanmera and Mikami, 1965).

C.

~10 ~11
Figure 1. Geologic map of the Nakadaira-Natsugayoi
area (slightly modified from Ehiro, 1977) with cephalopod
localities (Loc. A and 8). 1: Magoshi Formation, 2: Senbakaya Formation, 3: Kidoguchi Formation, 4-7: Nakadaira Formation (4: conglomerate, 5: sandstone, 6:
shale, 7: limestone), 8-10: Ochiai Formation (8: conglomerate, 9: sandstone, 10: shale), 11 : cephalopod locality.
HKF: Hizume-Kesennuma Fault.

Cephalopod horizon and associated fauna at Natsugayoi
The Nakadaira Formation developed around the 482-m
high peak, located northeast of Natsugayoi, is composed
mainly of limestones and is interbedded with some shales(Figure 2b). Cephalopods, together with bryozoans, brachiopods and crinoid stems, were collected from loose
impure limestone blocks on the north slope just below thepeak. The cephalopod fauna collected at Natsugayoi
comprises the following species:
Nautiloids.-Foordiceras sp., F.? sp., Pleuronautilus
sp. and Stearoceras sp.
Ammonoids.-Agathiceras sp. and Artinskia sp.
From the limestone which crops out on the 482-m highpeak, Ehiro (1977) reported a fusulinid species,ab
Nagatoel/a sp.
.... { Chalaroschwagerina sp.

PseudofiJsulina ? sp.

(= Chalaroschwagerina vulgaris), Pseudofusulina fusiformis and Pseudofusulina ambigua Zones.

~

Chalaroschwagerina vulgaris
Pseudofusulina ? sp.
Parafusulina cf. multiseptata

1

.....

B. Cephalopod horizon and associated fauna at Nakadaira
Near the fossil locality of the northwest of Nakadaira,the Nakadaira Formation is composed in ascending orderof shale beds (more than 20 m in thickness), impure
limestones (25-30 m), limestones (about 15 m), sandstones(10-12 m) and limestones (more than 15 m) (Figure 2a).
The uppermost part of the shale bed sequence is somewhat calcareous and is intercalated with some thin (1 to 5cm), irregularly lenticular limestones. The shale yields
some fossils of solitary corals, bryozoans, brachiopods,
gastropods, pelecypods, cephalopods and crinoid stems.
The cephalopod fauna at Nakadaira consists of the following species:
Nautiloids.-Tainoceras sp., Foordiceras? sp., Pleuro-

PseudofiJsulina cf. kraffli?

t cephalopods(~)

Rugosojusulina complicata{

ChalarOSChwagerina vulgaris ?

~ PseudofiJsulina fiJsiformis ?

r

Rugosojusulina alpina~ \ PseudofiJsulina bona ?

:Jcephalopods~

limestone~

impure limestone

~

shale

HY@l

sandstone

Figure 2. Columnar sections of the Nakadaira Formation near the cephalopod localities. a: northwest of Nakadaira (Loc. A in Figure 1), b: northeast of Natsugayoi(Loc. 8 in Figure 1).

Masayuki Ehiro

186

Pseudofusulina cf. kraffti (Schellwien and Dyhrenfurth). A
limestone bed lying about 50 m below the peak and below
the cephalopod horizon yields such fusulinids as Chalaroschwagerina vulgaris? and Pseudofusulina fusiformis?
These fusulinids possibly indicate that the cephalopod
horizon at Natsugayoi belongs to the Upper Sakamotozawan Series.

Cephalopod fauna of the Nakadaira Formation
Most cephalopod genera present in the Nakadaira
Formation have relatively long stratigraphic ranges.
Those species belonging to the genus Foordiceras are
known from Middle (Lower?) to Upper Permian strata andthose of Pleuronautilus from Lower Permian to Middle
Triassic beds (Kummel, 1953). Aphelaeceras species areabundant in Lower Carboniferous strata, but some species
are also known from the Lower Permian of North China(Yin, 1933) and from the Upper Permian of South China(Zheng,1984). The genus Parastenopoceras, which is so
far represented by only one species (type species: P.
khvorovae Ruzhentsev and Shimansky, 1954), is restricted
to the Artinskian of the Urals; Artinskia ranges from theuppermost Carboniferous to Lower Permian (Artinskian)(Ruzhentsev,1962). From these stratigraphic ranges, thegeologic age of the middle to the upper part of the
Nakadaira Formation is considered to be Early Permian,most probably Artinskian. This conclusion is in generalaccordance with previous correlations based on
fusulinids: the Sakamotozawan Series was correlatedwith the Upper Wolfcampian to Middle Leonardian (Kanmera and Mikami, 1965) or with the Upper Chuanshanian(Mapingian) to Lower Chihsian interval (Minato et al.,1978).
The ammonoid fauna of the Nakadaira Formation israther monotonous, largely represented by Agathiceras.
For the Permian of the Southern Kitakami Massif, thepresent author proposed three ammonoid zones (Ehiro,
1987): the Timorites Zone recognized in the middle andupper parts of the Kanokuran Series (Middle Permian), theAraxoceras Zone in the lower and middle parts of theUpper Permian Toyoman Series and the Medlicottia kitakamiensis Zone in the upper part of the Toyoman. Basedon the new data presented in this study, I propose to add
the Agathiceras Zone below the Timorites Zone (Ehiro,
1995). The Agathiceras Zone extends from the upper partof the Lower Sakamotozawan to the lower part of the
Kanokuran.
Systematic descriptions
All the specimens described in this paper are depositedin the collections of Institute of Geology andPaleontology, Tohoku University (IGPS) and in the Rikuzen-Takata City Museum (RCM). They were collectedby the author in the year 1991-1993 unless otherwise
stated.

Subclass Nautiloidea Agassiz, 1847
Order Nautilida Agassiz, 1847
Superfamily Tainocerataceae Hyatt, 1883
Family Tainoceratidae Hyatt, 1883
Subfamily Tainoceratinae Hyatt, 1883
Genus Tainoceras Hyatt, 1883
[Type species: Nautilus quadrangulus
McChesney, 1868]
Tainoceras sp.
Figures 3-1; 4-1a-c
Material.-One fragmental specimen, IGPS coil. cat. no.
102680, represented by outer and inner moulds, collectedfrom Nakadaira.
Descriptive remarks.- The specimen is deformed andonly one side of it is preserved. The conch is fairly large,
thickly discoidal and evolute in outline, bearing a wideand deep umbilicus. The whorl is estimated to be slightly
depressed dorsoventrally and the whorl section is subrectangular. The umbilical wall is steep and the umbilical shoulder acutely rounded. The flat lateral side bears
prominent ribs which extend from the umbilical to ventral
shoulder. The ribs· are slightly concave and nodose at
the ventral end. The venter is broadly rounded, but thecenter of it is narrowly sulcate. The presence of a pair ofrows of nodes suggest they border a median sulcus.
The suture is only partly preserved. It consists of a low
and rounded ventrolateral saddle, and a broad, shallow
and slightly sinuous lateral lobe.
The paired ventral nodes are characteristic of the genus
Tainoceras. Two species of Tainoceras, T. abukumaense
Hayasaka and T. kitakamiense Hayasaka, previously reported from the Southern Kitakami (Hayasaka, 1962;
Murata, 1971), differ from the present species in not having
lateral ribs. Some species of Tainoceras having remarkable lateral ribs were described from the Middle Permian
Maokouan formations of South China, and from theMiddle and Upper Permian of the Salt Range, Pakistan.
Among these species, the present species somewhat
resembles T. comptum Reed (Reed, 1944, p. 353, pI. 60,
fig. 1, pI. 62, fig. 2) described from the Upper? Productus
Limestone of the Salt Range in being large in size, but it
is distinguished from the latter by its narrower and sharp
ribs. The present species may be a new species,
because there are no other large species comparable to it.
However, the specimen is clearly too incomplete to betreated as the type of a new species.

Genus Foordiceras Hyatt, 1883
[Type species: Nautilus goliatus Waagen, 1879]
Foordiceras sp.
Figures 3-2; 4-2a, bMaterial.-A fragmented specimen, IGPS coil. cat. no.
102681, about a half volution of inner mOUld, collectedfrom Natsugayoi.

994.

Cephalopods from Lower Permian Nakadaira Formation.+----+-..-. •Ii).--t--++

)

.

2

~3
5

8
9

a-

b __

the ventral shoulder, and a shallow lateral lobe.
The Natsugayoi specimen is represented by a fragmented, broadly covex flank inclining toward the umbilicus,
with an acutely rounded ventral shoulder and broadly
rounded umbilical shoulder. The umbilicus is rather
large. The side is ornamented with radial ribs which
extend from the umbilical to ventral shoulder. The ribs
increase in height and width towards the ventral margin.
The suture is unknown.
Judging from the general shell form and the shape ofsuture, these two specimens probably belong to the genus
Foordiceras. This identification is, however, somewhat
questionable, because of their very poor state of preservation.
Subfamily Pleuronautilinae Hyatt, 1890
Genus Pleuronautilus Mojsisovics, 1882
[Type species: P/euronauti/us trinodosus
Mojsisovics, 1882J

Pleuronautilus yahagiensis sp. nov.

10mm

Suture lines of nautiloids from the Nakadaira
Formation. 1. Tainoceras sp., IGPS coil. cat. no. 102680.
2. Foordiceras sp., IGPS coil. cat. no. 102681. 3. Foordiceras? sp., IGPS coil. cat. no. 102682. 4. Pleuronautilus
yahagiensis sp. nov., IGPS coil. cat. no. 102686. 5-6.
Parastenopoceras sp., 5: IGPS coil. cat. no. 102689, 6:
IGPS coil. cat. no. 102690. 7-9. Stearoceras sp., 7: IGPS
coil. cat. no. 102692,8: IGPS coil. cat. no. 102691,9: IGPS
coil. cat. no. 102694. Scale bars: a for 5-6, b for 1 and 7,
c for 2-4 and 8-9.
Figure 3.

Description.- The conch is small, about 30 mm indiameter, and has a thickly discoidal outline, with amoderately large umbilicus. The shell form is slightly
compressed with broadly arched venter and slightly convex sides that converge dorsally. The whorl section issubtrapezoidal. The ventral and umbilical shoulders arerounded. Transverse ribs, almost straight, extend fromthe umbilical to ventral shoulder.
The suture has a shallow and wide ventral lobe, a low
saddle on the ventrolateral shoulder and a shallow laterallobe which occupies nearly all the flank.

Foordiceras ?

187

sp.

Figures 3-3; 4-3, 4Materia/s.-Fragmented inner and outer moulds, IGPS
coil. cat. no. 102682, collected from Nakadaira; anotherfragmental outer mOUld, IGPS coil. cat. no. 102683, collected from Natsugayoi.
Description.- The Nakadaira specimen is strongly
deformed ventrolaterally. The venter is broadly archedwith rounded ventral shoulders. The sides, havingstraight radial ribs, may have been convex. The suture
has a shallow ventral lobe, a low and rounded saddle on

Figures 3-4; 4-5a-7
Tainoceras abukumaense Hayasaka. Ehiro, 1977, p.13.
Materials.-Holotype: An outer mould of a large specimen, IGPS coil. cat. no. 102684, collected by M. Ehiro in1969. Paratypes: A fragmentary outer mould of a moderately large specimen, IGPS coil. cat. no. 102685; Outerand inner moulds of a fragmented, small specimen, IGPS
coil. cat. no. 102686. All collected from Nakadaira.
Diagnosis.-Pleuronautilus having a semicoronate
conch section and strong radial ribs with nodes on theventral margin.
Description.- Three specimens are all elliptically
deformed. The conch of the holotype, two and a half?
volutions of which are exposed, is evolute and discoidal in
outline, with a large, moderately deep umbilicus. The
outer mould of the moderately large specimen (Figure 46), though the central region of its shell is not wellpreserved, seems to possess a small umbilical perforation,
about 8 mm in the longest diameter. The umbilicalshoulder is rounded and the umbilical wall is steep. The
broadly rounded flanks converge toward the venter, butdiverge near the acutely rounded ventral shoulder. The
venter is slightly arched or flat, but becomes slightly
concave in the mature stage. Therefore, the cross section of the conch is semioval to semicoronate in shape,with its greatest width near the umbilical shoulder. The
diameter of the adoral end of the large specimen is 95 mm
in the deformed state and its corresponding height, widthand umbilical diameter measure about 33, 24 and 42 mm,
respectively.
The flanks have strong radial rdbs, which are straight
throughout their entire length. They extend from theumbilical to ventral shoulder and have conspicuous elongated nodes on the ventral margin. The nodes coalesce
to form almost continuous carinate ridges along theventral shoulder. There are 19 ribs on the last whorl.

Masayuki Ehiro

188

The interspaces between the ribs are somewhat wider
than the ribs themselves, but are nearly equal in width to
the ribs near the adoral end of the large specimen.
The suture lines are only poorly preserved on a fragmental and partly squashed inner mould of a small specimen (Figure 4-7). The suture (Figure 3-4) consists of abroadly rounded, shallow ventral lobe, a rounded saddle
on the ventral shoulder, and a broadly rounded, shallow
lateral lobe.
Comparison.-In having strong and straight ribs withnodes at the ventral margin, the present new species
somewhat resembles Pleuronautilus Iinchengense (Yin)(described originally as Huanghoceras ; Yin, 1933, p.21,
pI. 3, figs. 1-3) from the Lower Permian Taiyuan Series ofNorth China, Pleuronautilus tubercularis (originally described as Nautilus; Abich, 1878, p.22, pI. 3, figs. 5, 5a;
Shimansky in Ruzhentsev and Sarycheva, 1965, p. 160, pI.
15, figs. 1a, 1b) and Pleuronautilus sp.1 (Teichert andKummel, 1973), the latter two having been described fromthe Upper Permian Dzhulfian bed of Dzhulfa. The new
species is, however, clearly distinguishable from the otherthree foms by a semi coronate cross section.
Etymology.-From the local geographical name Yahagi,
from which the specimens were collected.

Pleuronautilus sp.

Figures 4-8a-9
Materials.- Two specimens were examined: Outer andinner moulds, both fragmented, IGPS coil. cat. no. 102687,
collected from Nakadaira. A fragmental outer mould,
IGPS coil. cat. no. 102688, collected from Natsugayoi.
Description.- The conch is evolute and thickly discoidal in outline. The Nakadaira specimen (Figure 4-8)
attains a diameter of at least 75 mm. The Natsugayoi
specimen (Figure 4-9) is fragmented, but its size is estimated nearly equal to that of the Nakadaira one. The
umbilicus is moderately large and rather deep. The
central region of the shell is not well preserved. The
umbilical shoulder is rounded and the umbilical wall is
steep. The slightly convex flanks converge toward theventer. The venter is nearly flat and the ventral shoulders are acutely rounded to edged. The cross section of
the conch is subtrapezoidal and the greatest whorl widthis just over the umbilical shoulder.
The lateral sides are ornamented with strong radial ribs.
They extend from the umbilical to ventral shoulder andbecome wider and lower toward the venter. From thepreserved last whorl, which is a little less than a half
volution, the specimen is estimated to have about 11 ribsin the last half whorl. The interspaces between the ribs
and the ribs themselves are nearly equally wide in the lastwhorl.
The suture line is not observed.
Superfamily Trigonocerataceae Hyatt, 1884
Family Trigonoceratidae Hyatt, 1884
Genus Aphelaeceras Hyatt, 1884
[Type species: Nautilus (Discites) disciform is
Meek and Worthen, 1873J
Aphelaeceras ct. falciferum Yin

Figures 4-10a, bCompare.-Apheleceras falciferum Yin, 1933, p. 8, textfig. 2, pI. 1, figs. 2-4.
Material.-An outer mould, RCM F762, collected by M.
Sato in 1991 from Nakadaira.
Description.- The conch is evolute and thinly discoidal
in outline, with a moderately large and shallow umbilicus.
The conch diameter attains more than 110 mm in a
deformed state. The umbilical shoulder is acutely
rounded and the umbilical wall steep. The side is convex
near the umbilical margin but flat or slightly concave fromthe central part to the ventral margin. The venter isnearly flat and the ventral shoulders are edged. The
conch section is semioval to modified hexagonal, with its
greatest width near the umbilical shoulder. The surfaceof the conch appears to be smooth.
Comparison.- The present specimen is comparablewith Aphelaeceras falciferum Yin in shape of the conch
section. However, whether or not it is conspecific withthe latter is somewhat questionable, because the conch israther poorly preserved and the suture is not known.

Family Grypoceratidae Hyatt in Tittel, 1900
Genus Parastenopoceras
Ruzhentsev and Shimansky, 1954
[Type species: Parastenopoceras khvorovae Ruzhentsev
and Shimansky, 1954J
Parastenopoceras sp.

Figures 3-5, 6; 6-1a-2
Materials.- Two fragmental specimens, IGPS coil. cat.
nos. 102689 and 102690, collected from Nakadaira.

Figure 4. 1. Tainoceras sp., IGPS coil. cat. no. 102680, lateral (a) and ventral (b) views, and cross section (c), x 0.7.
2. Foordiceras sp., IGPS coil. cat. no. 102681, lateral (a) and ventral (b) views of the inner mould. 3,4. Foordiceras?
sp., 3: IGPS coil. cat. no. 102683, 4: IGPS coil. cat. no. 102682, lateral views. 5-7. Pleuronautilus yahagiensis sp. nov.,
5: IGPS coil. cat. no. 102684 (Holotype), 6: IGPS coil. cat. no. 102685, 7: IGPS coil. cat. no. 102686, lateral views (5a,5b, 6, 7) and cross section (5c). 8,9. Pleuronautilus sp., 8: IGPS coil. cat. no. 102687, 9: IGPS coil. cat. no. 102688,
lateral views (8a, 9) and cross section (8b). 10. Aphelaeceras cf. falciferum (Yin), ReM F762, lateral view (a) and crosssection (b), X 0.75. All figures are approximately in natural size unless otherwise stated. Figures 1,3-10 are rubber
casts from outer moulds. Thin lines of cross sections show cross sections through rib and nodes.

994. Cephalopods from Lower Permian Nakadaira Formation

189

Masayuki Ehiro

190

Descriptive remarks.- The two specimens are large,
fragmented phragmocones, more than 150 mm in diameter. Although the umbilical part is not preserved, theconch section appears to be semielliptical with convex toflat sides and a strongly convex venter. The shell surface is smooth. The suture lines are partly preserved: ahigh rounded ventral saddle and a broad lateral lobe arerecognizable.
Although the present specimens are rather poorly
preserved and their generic assignment is somewhat
questionable, the suture and the conch section are diagnostic of the genus Parastenopoceras. Compared with P.
khvorovae (Ruzhentsev and Shimansky, 1954, p.99, pI. 9,
figs. 4-5), the type species of the genus, which has adiameter of 34 mm, the present species is quite large.
Genus Stearoceras Hyatt, 1893
[Type species: End%bus gibbosus Hyatt, 1891J

Stearoceras sp.
Figures 3-7-9; 6-3-6Materia/s.- Three specimens, IGPS coil. cat. nos.
102691-102693, collected from Nakadaira; another specimen, IGPS coil. cat. no. 102694, from Natsugayoi.
Description.- The specimens are all fragmented anddeformed, in part strongly obliquely deformed. They aresmall to moderate, ranging from about 30 mm to more than
60 mm in diameter. The conch is thickly discoidal andmay be involute, with a small umbilicus. Its cross section
is subtrapezoidal and depressed dorsoventrally. It possesses a broadly arched venter, somewhat convex sides
which slightly converge ventrally, and a steep umbilicalwall. The ventral shoulders are broadly rounded and theumbilical shoulders acutely rounded. The shell surface
is smooth. The sutures form a broad and shallow ventral
lobe, a low ventrolateral saddle, and a broad and shallow
lateral lobe.
Subclass Ammonoidea Agassiz, 1847
Order Goniatitida Hyatt, 1884
Suborder Goniatitina Hyatt, 1884
Superfamily Agathicerataceae Arthaber, 1911
Family Agathiceratidae Arthaber, 1911
Genus Agathiceras Gemmellaro, 1887
[Type species: Agathiceras suessi
Gemmellaro,1887J

Agathiceras sp.
Figures 5-1,2; 6-7-12

Materia/s.-Six specimens, IGPS coil. cat. nos. 102695102700, collected from Nakadaira; another specimen,
IGPS coil. cat. no. 102701, from Natsugayoi.
Description.- The specimens are small to moderatesized, with a conch diameter of 27 to 52 mm in a deformed
state. The conch is involute and thinly discoidal in
outline, with an almost closed umbilicus. The conch
section is semielliptical. The slightly convex sides converge toward the umbilicus and the umbilical shoulders
are rounded. The venter is convex with roundedventrolateral shoulders. The flanks are ornamented bymore than 30 fine spiral Ii rae. The inner mould is marked
by sinuous transverse constrictions numbering about four
per volution.
The suture is poorly preserved. There are one bifid
ventral lobe and three or four simple rounded lobes on thelateral sides.
Owing to the poor state of preservation and lateral
deformation, identification is difficult at the level of
species.
Order Prolecanitida Miller and Furnish, 1954
Superfamily Medlicottiaceae Karpinsky, 1889
Family Medlicottidae Karpinsky, 1889
Subfamily Medlicottinae Karpinsky, 1889
Genus Artinskia Karpinsky, 1926
[Type species: Goniatites flax Eichwald, 1857J

Artinskia sp.
Figures 6-13a, bMateria/.-One fragmentary specimen, IGPS coil. cat.
no. 102702, collected from Natsugayoi.
Description.-Only the ventral side and a portion of thelateral part of the living chamber? are preserved. The

n.tn.r·)\~
1'\00Jv~

1

\..:

....

2

(

I
5 mm

Figure 5. Suture lines of Agathiceras sp. from the
Nakadaira Formation. 1: IGPS coil. cat. no. 102697, 2:
IGPS coil. cat. no. 102698.

Figure 6. 1, 2. Parastenopoceras sp., 1: IGPS coil. cat. no. 102689, 2: IGPS coil. cat. no. 102690, lateral (1a) andventral (1b, 2) views. 1a-b= xO.6, 2= xO.8. 3-6. Stearoceras sp., 3: IGPS coil. cat. no. 102691, 4: IGPS coil. cat. no.
102692,5: IGPS coil. cat. no. 102693, 6: IGPS coil. cat. no. 102694, all lateral views. 3-5=x1,6=xO.65. 7-12.
Agathiceras sp., 7: IGPS coil. cat. no. 102695, 8: IGPS coil. cat. no. 102696, 9: IGPS coil. cat. no. 102697, 10: IGPS coil.
cat. no. 102701, 11: IGPS coil. cat. no. 102698, 12: IGPS coil. cat. no. 102699, all lateral views, x 1. 13. Artinskia sp.,
IGPS coil. cat. no. 102702, lateral view (a) and ventral view (b), X 0.8. Figures 1-6, 13 are inner moulds, 7-12 are rubber
casts from outer moulds.

994.

Cephalopods from Lower Permian Nakadaira Formation

191

Masayuki Ehiro

192

fairly large conch, the diameter of which reaches morethan 120 mm, appears to be flattened laterally. The
venter is nearly flat, but bears a prominent median groove.
The ventrolateral shoulders are narrowly rounded. On
each side of the ventral groove is a row of prominent
rounded nodes, which are transversely elongate andextend on to the lateral zones. On the fragmental outermould of the flank near the ventral shoulder, there remains
sinuous growth lines. The suture is unknown.

Acknowledgments
The author expresses his deep gratitude to Professor
Kunihiro Ishizaki of Tohoku University for his identificationof fusulinids. I am very grateful to Professor Tsunemasa
Saito of Tohoku University for his critical reading of themanuscript. Thanks are also extended to Professor
Brian F. Glenister of the University of Iowa and Dr. Yoshihiro Tanimura of the National Science Museum for theirkind assistance in the literature research, and to Mr.
Hiroaki Sasaki of Tohoku University who prepared manythin sections used in this study.

References cited
Abich, H., 1878: Geologische forschungen in den Kaukasischen Landern. Theil 1, Eine Bergkalkfauna ausder Araxesenge bei Djoulfa in Armenien, 126 p.,
Alfred Holder, Wien.
Ehiro, M., 1977: The Hizume-Kesennuma Fault - With
special reference to its character and significance on
the geologiC development -. Contributions fromthe Institute of Geology and Paleontology, Tohoku
University, no. 77, p.1-37. (in Japanese with English
abstract)
Ehiro, M., 1987: Permian ammonoids of the Southern
Kitakami Massif, Northeast Japan - Their stratigraphic distribution and zonation of the Permian-.
Journal of the Geological Society of Japan, vol. 93, p.
823-832. (in Japanese with English abstract)
Ehiro, M., 1995 in press: Permian ammonoid fauna of theKitakami Massif, Northeast Japan - Biostratigraphy
and paleobiogeography -. Paleo world, no. 5, Nanjing University Press.
Ehiro, M. and Mori, K., 1993: Discovery of Chaetetes fromthe Kidoguchi Formation of the western part of Yahagi-machi, Rikuzen-takata City, Southern Kitakami
Mountains and its significance. Journal of the Geological Society of Japan, vol. 99, p.407-41O. (inJapanese)
Hayasaka, I., 1962: Two speCies of Tainoceras from thePermian of the Kitakami Mountains. Bulletin of the
National Science Museum, vol. 6, p.137-143.

Kanmera K. and Mikami, T., 1965: Fusuline zonation of
the Lower Permian Sakamotozawa Series. Memoirsof the Faculty of Science, Kyushu University, SeriesD, vol. 16, p.275-320.
Koizumi, H., 1975: Paleozoic cephalopods of Japan. 149
p., Teiseki Bunko, Chiba, Japan. (in Japanese)
Kummel, B., 1953: American Triassic coiled nautiloids.
U.S. Geological Survey, Professional Paper 250, p.1104.
Minato, M., Kato, M., Nakamura, K., Hasegava, Y., Choi,
D.R. and Tazawa, J., 1978: Biostratigraphy and correlation of the Permian of Japan. Journal of the Faculty of Science, Hokkaido University, Series 4, vol. 18,
p.11-47.
Murata, M., 1971 : Fusulinid biostratigraphy and molluscan
fauna from the uppermost part of the Sakamotozawa
Formation and the pre-Kanokura unconformity, in thesouthern part of the Kitakami Massif, northeast
Japan. Transactions and Proceedings of the
Palaeontological Society of Japan, New Series, no. 82,
p.92-116.
Reed, F.R.C., 1944: Brachiopoda and Mollusca from theProductus Limestones of the Salt Range. Memoirsof the Geological Survey of India, Palaeontologia
Indica, New Series, vol. 23, p. 1-768.
Ruzhentsev, V.E., 1962: Superorder Ammonoidea. In,
Ruzhentsev, V.E. ed., Osnovy paleontologii, volume 5
Mollusca-Cephalopoda I, p.243-409. (in Russian)Ruzhentsev, V.E. and Sarycheva, T.G., 1965: Development and change of marine organisms at the Paleozoic-Mesozoic boundary. Trudy Paleontologicheskogo Instituta Academiia Nauk SSSR, vol. 108, p.1431. (in Russian)Ruzhentsev, V.E. and Shimansky, V.N., 1954: Lower Permian coiled nautiloids of the southern Urals. Trudy
Paleontologicheskogo Instituta Academiia Nauk
SSSR, vol. 50, p.1-152. (in Russian)Teichert, C. and Kummel, B., 1973: Nautiloid cephalopods
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Hikoroichi B~m, Nakadaira'i='3jZ, Natsugayoi !l;m, Rikuzen-Takata ~MiWiE8, Southern Kitakami Massif l¥itm~tJ:UJj;fg, Yahagi ~f'FTrans. Proc. Palaeont. Soc. Japan, N.S., No. 179, pp. 193-195, 1 Fig., September 30, 1995

SHORT NOTES~A new Carboniferous cephalopod Bogos!ovskya
akiyoshiensis from Southwest Japan

SHUJI NIK01, TAMIO NISHIDA2 and YUKO KYUMA3
1Department of Environmental Studies, Faculty of Integrated Arts and Sciences, Hiroshima University, Higashihiroshima,
724 Japan
2Department of Earth Science, Faculty of Education, Saga University, Saga, 840 Japan
3Nishiurakami Elementary School, Nagasaki, 850 Japan
Received 3 April 1995; Revised manuscript accepted 17 July 1995

The Akiyoshi Limestone comprises an organic reef
complex that was deposited on a seamount during Early
Carboniferous to Middle Permian time. It is found as alarge (8X16 km across) allochthonous body in the accretionary Akiyoshi Terrane with synchronous siliceousand Permian terrigenous clastic sediments in Southwest
Japan (Kanmera et al., 1990). The limestone is abundantly fossiliferous and provides knowledge of reef
paleocommunities in a low-latitude oceanic sea environment. Taxonomic studies concerning the Akiyoshi cephalopod fauna began with Nishida (1971) and were followed
by a series of works with his collaborators, including
Nishida and Kyuma (1982, 1984), Kyuma and Nishida(1987, 1992), Niko et al. (1987, 1991). In the course of
successive collecting efforts, twenty-nine specimens of arare orthocerid cephalopod Bogoslovskya were recoveredby Nishida and Kyuma from the Middle Carboniferous partof the Akiyoshi Limestone in the Isa area, Yamaguchi
Prefecture. A new species Bogoslovskya akiyoshiensis
is defined herein on the basis of these specimens. ASM
stands for the Akiyoshi-dai Museum of Natural History.
Systematic paleontology

Superfamily Orthocerataceae M'Coy, 1844
Family Orthoceratidae M'Coy, 1844
Subfamily Michelinoceratinae Flower, 1945
Genus Bogos!ovskya Zhuravleva, 1978
Type species.-Bogoslovskya perspicua Zhuravleva, 1978.
Diagnosis.-Shell orthoconic with circular to laterallycompressed cross section; surface smooth to finely lirate; sutures transverse, juvenile sutures with laterallobes, but becoming straight adorally; siphuncle submarginal to subcentral, narrow; septal neck long, orthochoanitic; connecting rings cylindrical; auxiliary
deposits occur in septal foramen of juvenile shell; lacking cameral deposits.
Remarks.-The juvenile shell morphology based on

Bogoslovskya akiyoshiensis Niko, Nishida and Kyuma sp.
nov. has been added to the generic diagnosis.
Bogos!ovskya akiyoshiensis Niko, Nishida

and Kyuma sp. nov.
Diagnosis.-Species of Bogoslovskya with approximately 7 degrees angle of expansion; circular then compressed cross section; ornamentation of fine transverse
lirae; width (maximum inner diameter of each camera indorsoventral plane)/Iength ratio of camerae approximately
2.5-3.9 in adoral shell.
Description.-Orthocones with relatively rapid shell
expansion for genus, angle ranges from 7.0 to 7.2
degrees; cross section of shell circular in juvenile shell,
then becoming laterally compressed, breadth/height ratioof shell approximately 0.92; largest specimen (ASM
50220) of phragmocone reaches 18.5 mm in height; shellsurface marked by fine lirae on anti-siphuncular (dorsal ?)side of adoral shell, transverse and slightly oblique,toward aperture on anti-siphuncular side, lirae becoming
finer toward siphuncular side; sutures slightly oblique,toward aperture on siphuncular side, juvenile sutures withweak but broad lateral lobes becoming nearly straightadorally; septa moderately deep; cameral length shortfor genus, width (maximum inner diameter of each camera
in dorsoventral plane)/Iength ratio in apical shell 1.952.05, increasing to 2.48-3.93 adorally; siphuncle narrow,maximum diameter of septal neck/shell height approximately 0.06-0.08, submarginal position, minimum distanceof central axis of siphuncle from shell surface per shellheight in dorsoventral section ranges from 0.19 to 0.23;
septal necks gently tapering orthochoanitic, in adoral
siphuncle slightly directed toward central axis of siphuncle, thus septal necks form funnel shape; neck length
moderate for genus, 1.3 mm of orthochoanitic portion atshell height 13.0 mm; annulus of weak auxiliary deposits
occurs in apical septal foramen, connecting rings notpreserved; no cameral deposits detected.

Shuji Niko et al.

194

7

4

32.

New Carboniferous cephalopod from Akiyoshi

Discussion.- This species shares considerable adultshell morphology with the Late Devonian (Famennian)species Bogoslovskya perspicua Zhuravleva (1978, p.57,
pI. 3, figs. 4a, b; the type species of the genus) in essential features such as laterally compressed shell, siphuncular size and position, septal neck shape and lack of
cameral deposits. Thus, the assignment of the species
within the genus Bogoslovskya appears certain. Bogoslovskya perspicua is distinguished from B. akiyoshiensis
sp. nov. only by its slightly narrower shell (angle of expansion 5-6 degrees versus approximately 7 degrees), longer
camerae (width/length ratio approximately 1.7-1.8 versus
2.5-3.9 in B. akiyoshiensis sp. nov. in corresponding shell
diameter) and lack of surface ornamentation. The juvenile shell morphology of Bogoslovskya perspicua is notknown. Previously, Bogoslovskya has been reported only
from the Middle to Upper Devonian of the Urals. Thus,
this is the first record of Bogoslovskya outside the Urals,
and the discovery extends the range of the genus into theMiddle Carboniferous (Moscovian). The present new
specimens reveal the possession of auxiliary deposits inthe juvenile siphuncle, which may be comparable to theadhesive area of the genitio-intestinal ligament in living
Nautilus (Blind, 1988).
Etymology.- The specific name is derived from the
Akiyoshi Limestone, where this species occurs.
Types.- The holotype, ASM 50202, is an incomplete
phragmocone, 36.2 mm in length. The following eightparatypes, all incomplete phragmocones, are assigned:
ASM 50151, 50152, 50209, 50210, 50219, 50220, 50239,
and 51260.
Occurrence.- This species occurs in a bioclastic grainstone to coquinoid limestone of Middle Carboniferous(Moscovian) age as indicated by the associated foraminifer Fusulinella biconica (Hayasaka). The collectingsite is identical with locality 1M 60 in Niko et al. (1991, fig. 1).

Acknowledgments
We are indebted to Dr. C.H. Holland, Trinity College,
University of Dublin, and Dr. Rex E. Crick, University ofTexas for reviewing this report.

References cited
Blind, W., 1988: Ober die primare Anlage des Siphos bei

195

ectocochleaten Cephalopoden. Palaeontographica
Abteilung A, vol. 204, p.67-93, pis. 1-3.
Flower, R.H., 1945: Classification of Devonian nautiloids.
The American Midland Naturalist, vol. 33, p.675-724.
Kanmera, K., Sano, H. and Isozaki, Y., 1990: Akiyoshi
Terrane. In, Ichikawa, K., Mizutani, S., Hara, I., Hada,
S. and Yao, A. eds., Pre-Cretaceous Terranes ofJapan, p.49-62. Publication of IGCP Project 224,
Osaka.
Kyuma, Y. and Nishida, T., 1987: Akiyoshiceras, a new
neoicoceratid ammonoid genus from the Upper Carboniferous of Akiyoshi. Bulletin of the Akiyoshi-dai
Museum of Natural History, no. 22, p. 23-41, pis. 1-5.
Kyuma, Y. and Nishida, T., 1992: Welleritid ammonoids
from the Akiyoshi Limestone Group. Bulletin of the
Akiyoshi-dai Museum of Natural History, no. 27, p.121, pis. 1-8.
M'Coy, F., 1844: A synopsis of the characters of the
Carboniferous limestone fossils of Ireland. Privately
published, 274 p. (reissued by Williams and Norgate,
London, 1862)
Niko, S., Nishida, T. and Kyuma, Y., 1987: Middle Carboniferous Orthocerataceae and Pseudorthocerataceae(Mollusca: Cephalopoda) from the Akiyoshi limestone, Yamaguchi Prefecture. Transactions andProceedings of the Palaeontological Society of Japan,
New Series, no. 148, p.335-345.
Niko, S., Nishida, T. and Kyuma, Y., 1991 : Middle Carboniferous Bactritoidea (Mollusca: Cephalopoda) fromthe Akiyoshi Limestone Group, Yamaguchi Prefecture. Transactions and Proceedings of the
Palaeontological SOCiety of Japan, New Series, no.
161, p.714-719.
Nishida, T., 1971 : Carboniferous ammonoids from Akiyoshi. Bulletin of the Akiyashi-dai Science Museum, no.
7, p.1-24, pis. 1-7.
Nishida, T. and Kyuma, Y., 1982: Mid-Carboniferous
ammonoids from the Akiyoshi Limestone Group.
Bulletin of the Akiyoshi-dai Museum of Natural History, no. 17, p. 1-54, pis. 1-10.
Nishida, T. and Kyuma, Y., 1984: Notes on Pseudoparalegaceras from the Akiyoshi Limestone Group.
Journal of Faculty of Education, Saga University, vol.
31, p. 221-241.
Zhuravleva, F.A., 1978: Devonskiye ortocerody, nadotryad
Orthoceratoidea (Devonian orthocerids, superorder
Orthoceratoidea). Akademia Nauk SSSR, Trudy
Paleantalagicheskoga Instituta, vol. 168, 223 p. (inRussian)

Akiyoshi tk"E, Isa WitC.

Figure 1. Bagaslavskya akiyoshiensis Niko, Nishida and Kyuma sp. nov. from the Akiyoshi Limestone Group. 1-4.
paratype, ASM 50152, juvenile shell, 1: lateral view, siphuncular side on left, arrow shows position of septal view given
in 2, x 2, 2: septal view, siphuncular side down, x 2, 3: dorsoventral thin section, x 4, 4: details of siphuncular
structure, arrows indicate auxiliary deposits, x 20. 5-8,12. holotype, ASM 50202, 5: view of siphuncular side, x 2,
6: lateral view, siphuncular side on right, x 2, 7: septal view of apical end, siphuncular side down, x 2, 8: dorsoventral thin section, x 4, 12: details of siphuncular structure, x 10. 9. paratype, ASM 50219, lateral view, siphuncular side on right, x 2. 10,11. paratype, ASM 50220, 10: lateral view, siphuncular side on right, x 2, 11: septal viewof apical end, siphuncular side down, x2. 13,14. paratype, ASM 50209, 13: details of siphuncular structure, X10, 14:dorsoventral thin section, x 4.

Trans. Proc. Palaeont. Soc. Japan, N.S., No. 179, pp. 196-200, 3 Figs., September 30, 1995

SHORT NOTES

Reexamination of the age of the Canoptum assemblage(Radiolaria) from acidic tuff in the Hiuchiwan Unit of theTanba Group, Southwest JapanHISASHI SUZUKI
Department of Geology and Mineralogy, Faculty of Science, Kyoto University, Kyoto, 601-01 Japan
Received 8 May 1995; Revised manuscript accepted 28 July 1995

Introduction

Species of the radiolarian genus Canoptum Pessagno,
1979 have often been found from Upper Triassic andLower Jurassic strata in the Mesozoic accretionary complexes of Southwest Japan (e.g., Yao et al., 1980; Ishiga,
1983; Fukudomi, 1990; Suzuki and Itaya, 1994; lijima etal., 1994). In general, Canoptum species occur in association with various other species of nassellarians, but
occasionally they constitute a particular type of radiolarian assemblage, in which species of Canoptum make up
70-90% of the nassellarian individuals (Yao, 1990; Suzuki, 1993, 1995). The geologic age of all these Canoptumdominant assemblages found in Southwest Japan has
hitherto been considered as latest Triassic (Fukudomi,
1990; Musashino et al., 1992; Takashiroyama ResearchGroup, 1993; Itasaka et al., 1994), because their species
composition resembles that of the Canoptum triassicum
assemblage (Yao, 1982) described from the uppermost
Triassic chert of the Inuyama area. Furthermore, it has
been taken as supporting evidence for this age assignment that typical Jurassic genera such as Parahsuum,
Droltus, Bagotum, etc. are not found in these Canoptumdominant assemblages.
The present author has reported the Canoptum-dominant assemblages in the Umenoki Unit of eastern Shikoku
and the Kanoashi Complex of Shimane Prefecture, andnamed them the Canoptum assemblage (Suzuki, 1993,
1995). These Canoptum assemblages are concluded to
be of Early Jurassic age, because the assemblages
contain Early Jurassic species and occur from strata that
also yield a typical Early Jurassic assemblage containing
Parahsuum.
The present study deals with the third finding of the
Canoptum assemblage in Lower Jurassic strata. The
assemblage was found from acidic tuff in the Hiuchiwan
Unit of the Tanba Group. Radiolarian assemblages fromthis acidic tuff were first reported by Musashino et al.
(1992). They showed two types of radiolarian assemblage, i.e. the Canoptum triassicum and the Parahsuum
simplum assemblage, and referred their age to latest

Triassic and Early Jurassic, respectively. Reexaminationof the species composition of the Canoptum triassicum
assemblage of Musashino et al. (1992) leads to the conclusion that the assemblage should be attributed to the
Early Jurassic rather than latest Triassic.
Acknowledgments. - The author is deeply indebted toProf. K. Chinzei (Kyoto Univ.), who guided him in fieldsurvey and read the manuscript.
Material

Acidic tuff containing radiolarian fossils at Nakayama
Pass in Sonobe town, Kyoto Prefecture (Figure 1) belongs
to the Hiuchiwan Unit of the Tanba Group (Imoto et al.,1991). The Hiuchiwan Unit is an olistostromal complex
composed of greenstone, limestone, chert, acidic tuff,
mudstone and sandstone (Imoto et al., 1991). The acidic
tuff at Nakayama Pass is fine-grained and light green,
stratified with intercalations of black mudstone. These
strata strike N75-80"E, and dip 35-45" southwards.
Sketch of the outcrop studied and columnar section are
shown in Figure 2. The strata are continuous and there
is no fault in the outcrop. The outcrop is a part of thesection described by Musashino et al. (1992).
Seven rock samples were collected from the outcrop.
These samples were processed with about 3% hydrofluoric acid for 24 hours and were sorted with a sieve between
opening 180,um and 63,um. Obtained residues wereconfined between object glass and cover glass withmounting medium "Entellan New" to make the preparations. Radiolarian genera and species were identified
under an optical microscope.
Radiolarian assemblages and their age

Abundant radiolarian individuals were detected fromfive rock samples among the seven samples collected.
The radiolarian species are listed in Table 1, and representative species are shown in Figure 3. While thesamples 103a, 103d and 103e yield the Canoptum-dominant assemblage, the samples 103b and 103c yield the33.

Canoptum assemblage from the Tanba Group197

Figure 1. Location of the outcrop studied. (b). Based on the topographic map "Sonobe", 1 : 50,000 scale,
Geographical Survey Institute.

assemblage containing abundant Parahsuum individuals.
The two assemblages occur alternatively in a section 3.4
m thick (Figure 2).
The Canoptum - dominant assemblage from samples
103a, 103d and 103e is considered to be an equivalent of
the Canoptum assemblage from the Kanoashi Complex
reported by Suzuki (1995), because (1) Canoptum content
reaches more than 70% of the nassellarian individuals, (2)there is a nassellarian species (gen. et sp. indet., Figure 34) that is closely similar to Nassellaria gen. et sp. indet. A,
one of the characteristic species of the Canoptum assemblage of the Kanoashi Complex, and (3) typical Early
Jurassic genera such as Parahsuum, Drottus and Bagotum
are scarcely found in this assemblage.
In the assemblage containing Parahsuum, the following
species were recognised as leading fossils : Parahsuum
ovate Hori and Yao, Droltus hecatensis Pessagno andWhalen, and Bagotum sp. The occurrence of these

species indicates an Early Jurassic age. Parahsuum
ovate is an index fossil of the Parahsuum simptum zone of
the Inuyama area (Hori , 1990), suggesting an age from
Hettangian to early Toarcian . The stratigraphic range ofDrottus hecatensis and of the genus Bagotum makes
further detailed age assignment possible. According toPessagno and Whalen (1982), Droltus hecatensis ranges
in age from Rhaetian (?)/ Hettangian to early Pliensbachian, and the genus Bagotum Pessagno and Whalenoccurs from strata younger than Sinemurian. Consequently, the assemblage containing Parahsuum suggests
a Sinemurian or early Pliensbachian age, based on theoccurrence of these taxa.
Although typical Early Jurassic genera common inSouthwest Japan could scarcely be found in the
Canoptum assemblage of Nakayama Pass, Canoptum
species and Natoba minuta Pessagno and Poisson in thisassemblage may suggest an Early Jurassic age. ThereHisashi Suzuki

198
Table 1.

List of radiolarians from the acidic tuff of Nakayama Pass.

species/sample No.

103a

103b

103c

103d

103e

103f

Liosphaeridae gen. et sp. indet.

*

*

*

*

*

*
*

Praeconocaryomma sp.
Sphaerostylus sp.

*

Pseudostylosphaera sp.
Gorgansium sp.

*

Triactoma (7) sp.
Staurosphaera (7) sp.
Stypolarcus sp.

*

*
*
*
*

*
*

Hagiastrinae gen. et sp. indet.
Orbiculiforma sp.

*

*

*

Palaeosaturnalis sp.

*

*
*

*

*

*
*

*

*

*
*

*

*
*

Canoptum sp.

C. rugosum PESSAGNO and POISSON
Tricolocampe sp.
Natoba minuta PESSAGNO and POISSON
Cornutella (7) sp.
Saitoum sp.
Archicapsa sp.
Parahsuum sp.
P. ovale HORI and YAO
Oroltus sp.

***

O. hecatensis PESSAGNO and WHALEN
Bagotum sp.
Oictyocephalus sp.
Stylocapsa (7) sp.
Tricolocapsa sp.
Stichocapsa sp.

are many individuals of Canoptum species in the assemblage which have H-type structure around circumferential
ridges (Figure 3-1). Pessagno and Poisson (1981)
mentioned that the H-type structure of Canoptum had
been observed exclusively within Early Jurassic species.
Natoba minuta was first described from the lower Pliensbachian of Turkey (Pessagno and Poisson, 1981). Unfortunately, there is no further report of its occurrence
outside the locus typicus except for the Umenoki Unit ofeastern Shikoku, in which Suzuki (in press) depicted
Natoba minuta from lower Pliensbachian chert. The
stratigraphic range of Natoba minuta is not yet clear, but
it could probably be limited within the Lower Jurassic,
because Natoba minuta has thus far been reported fromneither the Upper Triassic nor Middle Jurassic. Based on
the occurrence of these forms, the age suggested by the
Canoptum assemblage of Nakayama Pass is Early Juras-

*

*

*
*
*

*

*
*
*
*
*
*

*

*

*

*

*
*
*

*

Laxtorum (7) sp.

Nasseliaria gen. et sp. indet.

*
*
*
*
*
*

*

*

*
*

sic, so that there is no great difference between ages of
the assemblage containing Parahsuum and the Canoptum
assemblage.
Musashino et al. (1992) illustrated some speCies, whichhave been thought to suggest a Late Triassic age, fromthe same acidic tuffs at Nakayama Pass: Triassocampesp., Squinabo/el/a sp., Sarla (?) sp. and Veghicyc/ia sp.
(Musashino's Orbiculiforma multifora). However, taking
the occurrence of Early Jurassic speCies into consideration, these Late Triassic taxa could be fossils derived from
Late Triassic strata, or their ranges may extend into the
Early Jurassic. This study ascertained no radiolarianspecies indicative of a Late Triassic age, with the exception of isolated spiral spines of supumellarians.
Consequently, the section of acidic tuff studied at
Nakayama Pass can be assigned to the Early Jurassic. It
is certain that the Canoptum-dominant assemblage which33. Canoptum assemblage from the Tanba Group

(a)

199

(b)
Horizon (m)

3

I03g
?

103f

2

t03e
l03d

1
acidic tuff

l03c

assemblage ::containing :103b Parahsuum:

black mudstoneoFigure 2. (a). Sketch of the outcrop studied . (b). Columnar section . Solid circles in Figure (a) represent
sampling points.

Figure 3. Radiolarians of the Canoptum assemblage (1 to 5) and the assemblage containing Parahsuum(6 to 8) at Nakayama Pass. 1 : Canoptum sp., which possesses H- type structure around circumferential ridges,
2: Canoptum rugosum Pessagno and Poisson, 3 : Gorgansium sp., 4 : Nassellaria gen. et sp. indet., 5:
Notoba minuta Pessagno and Poisson, 6 : Parahsuum ovate Hori and Yao, 7 : Parahsuum sp., 8a- b : Drottus
hecatensis Pessagno and Whalen. Scale bar equals 100 ,u m.

Hisashi Suzuki

200

has hitherto been considered as latest Triassic occurs
also from Lower Jurassic strata of Southwest Japan.

References cited
Fukudomi, T., 1990: Jurassic melange, Kanoashi Complex, in western Shimane Prefecture, Southwest
Japan. Journal of the Geological Society of Japan,
vol. 96, p.653-667. (in Japanese with English
abstract)
Hori, R., 1990: Lower Jurassic radiolarian zones of SW
Japan. Transactions and Proceedings of the
Palaeontological Society of Japan, New Series, no.
159, p. 562-586.
lijima, H., Sekine, K. and Saito, Y., 1994: Geologic age ofthe Kamiyoshida Unit of the Chichibu belt, Kanto
Mountains, Japan. Bulletin of the National Science
Museum, Series C, Geology, vol. 20, p.119-131.
Imoto, N., Matsuura, H., Musashino, M., Shimizu, D. and
Ishida, S., 1991: Geology of the Sonobe District. 68
p., 1 geological sheet map at 1 : 50,000. Geol. Surv.
Japan, Tsukuba. (in Japanese with English abstract)
Ishiga, H., 1983: Two suites of stratigraphic succession
within the Tamba Group in the western part of theTamba Belt, southwest Japan. Journal of the Geological Society of Japan, vol. 89, p.443-454. (inJapanese with English abstract)
Itasaka, K., Matsuoka, A. and Tazawa, J., 1994: Late
Triassic radiolarians from the pre-Tertiary rocks in the
Washisaki area, northeast of Sado Island, Niigata
Prefecture, central Japan. Journal of the GeologicalSociety of Japan, vol. 100, p.368-370. (in Japanese)Musashino, M., Kusunoki, S. and Kusunoki, T., 1992:
Triassic clastic rocks situated at the uppermost partof the Tamba Belt. Bulletin of Kyoto University of
Education, Series B, Mathematics and Natural Science, no. 80, p. 1-9, pis. 1-2. (in Japanese with English
abstract)
Pessagno, E.A. Jr. and POisson, A., 1981: Lower Jurassic
radiolaria from the GOmO~IO allochton of southwestern Turkey (Taurides Occidentales). Bulletin of theMineral Research and Exploration Institute of Turkey,
no. 92, p. 47-69, pis. 1-14.

Pessagno, E.A. Jr. and Whalen, P.A., 1982: Lower andMiddle Jurassic radiolaria (multicyrtid Nassellariina)
from California, east-central Oregon and the Queen
Charlotte Islands, B.C. Micropaleontology, vol. 28, p.
111-169, pis. 1-13.
Suzuki, H., 1993: The Canoptum Assemblage (Radiolaria)
from the Umenoki Unit (the Northern Chichibu Belt) in
the Kamikatsu town area, Tokushima Prefecture,
Southwest Japan. News of Osaka Micropaleontologists special volume, no. 9, p.109-117, pI. 1. (inJapanese with English abstract)
Suzuki, H., 1995: Das Verbreitungsmuster der CanoptumVergesellschaftung (jurassische Radiolarien) in der
grauen Tonstein-Abfolge vom Kanoashi-Komplex,
SOdwestjapan. Journal of the Geological Society ofJapan, vol. 101, p. 451-461. (in Japanese with German
abstract)
Suzuki, H., in press: FrOhjurassische Radiolarienfauna
aus dem mesozoischen akkretierten Komplex von
Ost-Shikoku, SOdwestjapan. Neues Jahrbuch tUr
Geologie und Palaontologie, Abhandlungen, Bd.197.
Suzuki, H. and Itaya, T., 1994: Accretionary complexes of
the Kurosegawa, Northern Chichibu and Sanbagawa
Belts in the Kamikatsu town area (Shikoku), Southwest Japan. Journal of the Geological Society ofJapan, vol. 100, p. 585-599. (in Japanese with English
abstract)
Takashiroyama Research Group, 1993: A new information on the geological history of the Tamba Belt,
Southwest Japan. Earth Science (Chikyu Kagaku),
vol. 47, p.549-554, pI. 1. (in Japanese)
Yao, A., 1982: Middle Triassic to Early Jurassic radiolarians from the Inuyama area, central Japan. Journalof Geoscience, Osaka City University, vol. 25, p.5370, pis. 1-4.
Yao, A., 1990: Triassic and Jurassic radiolarians. In,
Ichikawa, K., Mizutani, S., Hara, I., Hada, S. and Yao,
A. eds., Pre-Cretaceous Terranes of Japan, p.329345, pl. 1-4, Pub. IGCP Project No. 224, Osaka.
Yao, A., Matsuda, T. and Isozaki, Y., 1980: Triassic andJurassic radiolarians from the Inuyama area, central
Japan. Journal of GeOSCience, Osaka City UniverSity, vol. 23, p.135-154, pis. 1-3.

201

Palaeontological Society of Japan (JSP) Council Actions
During its meeting on June 23, 1995, the Council enacted the following changes to its
membership.
New members elected:
Futoshi Akamatsu,
Masakatsu Fujita,
Emiko Hayakaze,
Shigeru Hiramatsu,
Sinji Kikuchi,
Hiroto Matsuki,
Jun Mitsuhashi,
Kousuke Naruse,
Motoo Okada,
Hiroyuki Takata,
Tsukasa Tome,Toshio Yasui,

Naoko Egashira,
Keisaku Fukata,
Seiji Hayashi,
Kazuhiro Ishii,
Masahiro Kishigami,
Nachio Minoura,
Shigeo Miyazaki,
Kumiko Nishiyama,
Masaaki Okuda,
Hideo Takimoto,
Shintaro Tsuchiya,
Isao Yonemitsu.

Yoshihiro Fujimoto,
Naoto Hamada,
Yoshihiko Hieda,
Shunsuke Kawakami,
Takeshi Kon,
Taro Mito,
Rei Nakashima,
Harushige Noda,
Takuji Shibasaki,
Yukiko Tate,
Hideki Ushirosako,

Resigned members:(Fellow)
Yasuo Maeda(Ordinary member)
Hollis Christopher, J., Hu Chung-Hung,
Shigeji Ogino,
Mitsuru Marukawa,Harumi Sugawara

Iginio Dieni,
Masamichi Shiozaki,

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Transactions and Proceedings of the PalaeontologicalSociety of Japan
September 30, 1995

New Series No. 179
CONTENTS
TRANSACTIONS
991.

Katsumi Takayasu , Damayanti D. Gurung and Keiji Matsuoka : Some new species offreshwater bivalves from tne Mio- Pliocene Churia Group, west- central Nepal .. . ...... . 157

992.

Tarou M. Kiso: Organic components in enameloid of extant and fossil shark teeth .. .. .. 169

993.

Tomowo Ozawa, Keisuke Inoue and Susumu Tomida: Early to Middle Miocene molluscan fossils from the Megami and Ebie limestones in Shizuoka Prefecture and their _implications for the formation of a Miocene coral - algal reef within the Japanese faunal
realm

994.

...... . ............... .. . . .... ... .... . ........ . .. .......... ....... .......... 175

Masayuki Ehiro: Cephalopod fauna of the Nakadaira Formation (Lower Permian) in theSouthern Kitakami Massif, Northeast Japan .. .. .. .. .. . . .. .. .. .. .. .. .. . . .. .. .. .. . . . . . . 184

SHORT NOTES

32.

Shuji Niko, Tamio Nishida and Yuko Kyuma : A new Carboniferous cephalopod 80goslovskya akiyoshiensis from Southwest Japan .. .. .. .. .. . . . . . . .. .. .. . . . . .. .. .. .. .. .. .. 193

33.

Hisashi Suzuki: Reexamination of the age of the Canoptum assemblage (Radiolaria)
from acidic tuff in the Hiuchiwan Unit of the Tanba Group, Southwest Japan .. . . ...... 196

PROCEEDINGS .. . . .. .. .. .. .. .. .. .. . . . . .. .. .. .. .. .. . . .. . . .. .. . . .. .. .. . . .. .. . . . . . . .. .. .. .. 201