Transactions and Proceedingsof thePalaeontological Society of Japan
New Series

No. 99Palaeontological Society of Japan
September 20, 1975

EditorTakashi HAMADA
Associate Editor Ikuwo OBATA

Officers for 1975 - 1976
Honorary President: Teiichi KOBAYASHI
President: Tatsuro MATSUMOTO
Councillors (*Executive): *Kazuo ASAMA, Kiyoshi ASANO, *Kiyotaka CHINZEI,*Takashi HAMADA, *Tetsuro HANAI, *Itaru HAYAMI, Tadao KAMEL,*Kametoshi KANMERA. *Tamio KOTAKA, *Tatsuro MATSUMOTO, Tokio
SHIKAMA, Tsugio SHUTO, *Yokichi TAKA YANAGI, Toshimasa T ANAL,*Hiroshi UJIIE
Executive Committee:
General Affairs: Tetsuro HANAI, Itaru HA YAMI, Kiyotaka CHINZEI, Saburo
KANNO, Yasuhide IWASAKIMembership:
Finance:Kazuo ASAMA, Kazuhiko UEMURA

Hiroshi UJIIE

Planning: Tamio KOTAKA, Hiroshi NODA
Publications
Transactions: Takashi HAMADA, Ikuwo OBATA
Special Papers: Kametoshi KANMERA, Ienori FUJIYAMA, Tomowo OZAWA"Fossils": Yokichi TAKAYANAGI, Toshiaki TAKAYAMA

Fossil on the cover is the six leaves in a whorl of Trizygia oblongifolia(GERM. & KAULF.) ASAMA from the Maiya formation (Parafusulina zone),
Maiya, N. E. Japan.
All communications relating to this journal should be addressed to the
PALAEONTOLOGICAL SOCIETY OF JAPAN
c/o Business Center for Academic Societies, Japan
Yayoi 2-4-16, Bunkyo-ku, Tokyo 113, Japan
Sole agent: University of Tokyo Press, Hongo, Tokyo

Trans. Proc. Palaeont. Soc. Japan, N. S. No. 99, pp. 109-132, pis. 10, 11, September 20, 1975

648.

FUNCTIONAL MORPHOLOGY OF OTOSCAPHITES PUERCULUS(JIMBO), AN UPPER CRETACEOUS AMMONITE*
KAZUSHIGE TANABE
Department of Geology, Kyushu University, Fukuoka 812~lII!*Cf&Wl7 :/ -'f: T -1

l- Otoscaphites puerculus (JI~IBO) ~~fjg~~JTh~i't:HiJF1t:: ~I::fflf~
p :=. 7:/ (Inoceramus hobetsensis 'Iff) iJ' 1?:i!lUi/fl¥.Jt;::l*~ ~tLt.:
16 -Ij-:/ -;I Ivt;::, Ffff~!:t:i*liJI'JtI!!J!ilG;to.J:: If ~l::lfjj;giftffll~*jr*tI!!J!ilG.@:~ 8 -Ij-:/ -;I I v oa-1.m;t t.: H 24
-Ij-:/ -;I IV, kG 150 1Il1*~ Otoscaphites puerculus t;:: '?~ '-ClEiftIl'Jriii, Wiil'Triii'('~~;WJt.d~~
WHJrHrtJ: ? C C t te., f*r;:~ H 'f((OOPf,:te. '?~'-C~~td*.fi\loa-ilIlj5E L, ]!fltLl¥.Jte.%I!:~i$j]oa­
W-:±l Lt.:o -t~*5*, %l!:1:J te.mi~tJ: 7 '" '>' l-~;j; 7.> Ql(;"f.%I!:~ 7 7 !/ -'f: ~ - :/~@:ili;to.J:: If 5.5rr
iftilidl~l::ffll~;fptl!!J!ilG~ -r "" -~.~~@&~K~~7.>I?~~~m~7p~l-g-~Ql(;.~tt, _~I¥.JK*~~7.>~, ~K~~IjN~~te.*,"lE Lt.:(±m~.~li

1.6rr iJ'l? 1.2rr t;:iIlXP~7.>'::' C iJ,hiJ' -:>t.:o i t.:~g'lte.~~7.>~!!i1;;to.J:: If}J!Hl1;~IJ~ ~ 7 p ~l- g - ~Ql(;.~te. '?~'-C t_rf3'i¥Jfe.i$j]~** Lt.:.::. C oa-7f-~o i$j]H~~*5*, r&~*~~*"eli7'.1Y-'f:~-:/t;::*iJ'Al?tJ:~':I*1t!l'('t, ~Pf,:~~:i:li7J(.J:: I)*~ < tJ:7.> iJ', J:&~1\!i~~*,(,li 77 f/ 'f: ~ - :/te.k{:J 30-47% 7J(oa-Ant.::I*1t!l'('%I!:~.l:I::]~J:t7J( c ~ L < tJ: 7.>0.::. nl?~~~iJ' 1?*fil!liJ:iili~~Jlt~~1r.tc.f*-:> -C Ql(;"f._~1=.Ti5
I?
~~~icH'7.>kGltrll~ (k{:J 7.5rr) t.J]!fiJ'l?nli!!i1;;to.J::lflfM!!i1;~IJ~iJ'f&Je.IJ< tJ:7.>iJ'l?, 001*Je~1".iftt;::1=.m~~oa-JM:i*' i¥JM:iiiJ'I?~~t;::~;tt.:.::. ciJ'lt5E~n7.>o#VJ '811 - Ql(;~~oa-~1=.il' 1?~1JM:tJ:~' LJM:ilkiit;::~;tt.: t ~ C ,\!!,hn7.> 0 i' t.:r(3I~1\!i~-Ij-:/ -;I/v'('I'i,

and CHMBERLAIN (1967) and CIIAMBER~
LAIN (1969) analysed the fundamental
morphology of ammonites using an ana~
logue computer and simulation models.
REYMENT (1956, 1973), HEPTONSTALL(1970), MUTVEI and REYMENT (1973) and
RAUP (1973) discussed the nekroplanktic
problem based on flotation experiments
using modern Nautilus and models ofammonites.
WESTERMANN (1971) dis ..
cussed the functional significance ofmany characters of ammonites at theordinal level.
Moreover, studies of modern Nautius
and Sepia by BIDDER (1962), COLLINS andMINTON (1967) and DENTON and GILPINBROWN (1961, 1963, 1966,1973), have given
a lot of important information for the
study on the functional morphology offossil cephalopods.

Introduction and Acknowledgements
Shelled cephalopods are suitable rna ..
terial for the study of functional mor ..
phology, because of their diverse morphology and complicated organization.
Since MOSELEY'S (1838) mathematicalanalyses of cephalopod shells, studies ofthe functional morphology of ammonites
have been carried out by many paleontologists: Noteworthy examples of suchstudies are calculation of buoyancy andreconstruction of mode of life of thedifferent shell type ammonites by TRUEMAN (1941) and experiments on relative
streamlining using the plaster models ofammonites by KUMMEL and LLOYD (1955).
More recently, RAUP (1965, 1967), RAUP

* Received Nov. 9, 1974: read Jan. 12, 1974
at Fukuoka.
109

Kazushige TANABE

110

As a result of these studies, many
aspects of the functional significance ofammonites have become clear. However,most of the previous studies were mainly
based on small collection, and little has
been done on the functional evolution at
the population level.
I have been working on the functional
evolution of some species of the Upper
Cretaceous scaphitoid ammonites under
the supervision of Professor Tatsuro
MATSUMOTO of Kyushu University.
In this study, I make a biometricalmorphologic analyses of Otoscaphites
puerculus (JIi..mo) on the basis of 24
samples, collec,ted from south Sakhalinand Hokkaido, considering the functional
morphology and evolution of the species.
Acknowledgements: Here I express mysincere gratitude to Professor Tatsuro
MATSUMOTO for his valuable suggestions
and critical reading of my manuscript.
I am indebted to Professor Richard A.
REYMENT of the University of Uppsala,
Professor David M. RAUP of the Univer·sity of Rochester, Associate Professor
Itaru HAY AMI of the University of Tokyoand Dr. Hiromichi HIRANO of Kyushu
University for their careful review of themanuscript and numerous instructive suggestions about the functional morphologyof ammonites. I also express my sincere
gratitude to Associate Professor Kametoshi KANMERA and Dr. Tomowo OZAWAof Kyushu University and to Dr. Ikuwo
OBATA of the National Science Museum,
who have given me much instructive
advice about my research, to Professor
Tetsuro HANAI of the University ofTokyo for permission to examine thecollections in the University Museum.

ammonites from japan and its adjacentareas are, in general, limited to theTuronian and Coniacian. They often
occur abundantly in the silty sedimentsof the Saku formation of the Middle Yezo
Group (MATSUMOTO and OKADA, 1973).
Y ABE (1927) called the biofacies characterized by Scaphites and Otoscaphites theYezoites Beds.
Otoscaphites puerculus (JIMBO), discussing in this paper, is rather small insize for the Scaphitidae; it is characterized by a moderately evolute shell witha pair of long lappets.
Originally, JIMBO (1894, p.37, pI. 5, fig.
4a, b) described the present species as
Scaphites puerculus JIMBO from thePankemoyubari River, a left tributary of
the Yubari River, Yubari district of central Hokkaido.

Material
Systematic position of, Otoscaphites
puerculus : Occurrences, of scaphitoid

Text-fig. 1. Map showing the Cretaceous
outcrops and the areas studied,648. Otoscaphites puerculus, an Upper C1'etaceous Ammonite

)-~

Ub:

~ -?
. -t"o111

Komikinenbetsu
sandstone member'»'",f .

'"<SI"'0<Sl'sv====---oText-fig. 2.

2Km

Map showing the fossil localities in the Tappu district.

Y ABE (1910) summarized the scaphitoid
ammonites from Hokkaido and describedsome species. In that study, he established the genus Yezoites and included
this species in it.
Subsequently, WRIGHT (1953) pointed
out that Yezoites planus of Y ABE (1910)
is a true Scaphites. He judged Y ABE'S(1910) Yezoites as invalid and proposed
the genus Otoscaphites for the group ofmoderately evolute shells with a prominent constriction and a pair of longlateral lappets on their apertural margin;
he included Scaphites puerculus in Otoscaphites.
According to Y ABE (1910), the present
species occurs abundantly in the Turonian and Coniacian of Japan, but I doubt

whether the present species ranges into
the Coniacian, because the range in
growth patterns of the Coniacian specimens is different from that of the Turonian Ones. Furthermore, the Coniacian
specimen has much smaller protoconch
and nepionic sizes than the Turonian one.
The Turonian samples remain constantranges of nepionic and protoconch sizes
throughout the sequence of the areas
studied.
At present, I refrain from deciding
whether these differences are intraspecific or interspecific, because insufficient Coniacian samples are at my disposal for this problem.
,In this paper, I treat only the Turonian
samples for the above mentioned reasons.

112](az~~s hig e T ANA BE

AGE
~

Z

«

STATION3

"

0
.r;

E

S TA TIO N2

u

«

~

Z

E

0

0

c

U

"

S TA TI ON 1

S TATION4

,
~

~

c

"0
.r;
"
/

/
/

"0
C

Z

«

z
0
a:

=>
I-

200

..c"
0
L

~ T uffac eo us r,o ck_

10 0

Mudstonern
D
I
I

Alternat ion

San ds ton eA

110d.c.e'

o

::gb"
1100
106q
106 h

zon e ,choroc te r-ized by huge I. hobets e nsi s

Te xt-fig . 3. Strati g raphic pos it ion of each sam ple from the T a ppu di st rict .

These samples were collected from the
N aibuchi district, south Sakhalin , theTappu district, northern central Hokkaido
and the Oyubari district, central Hokkaido (Text-fig. 1).
Sampling m ethod: Each sample, studied in this paper, is composed of several
specimens collected from a single calcareous nodule. The stratigraphic positionof each sample from the Tappu districtis ex pressed by the thickness measured
from the initial horizon of the earliest
appearance of the present species. Many
specimens of Ino ceramu s (s. str.) hobets-

ensis NAGAO and MATS UMOTO are associated with every sample. In somecases, other heteromorphs sLich as Nipponites and S ealm-ites are associated withthe present species.
According to MATSUMOTO'S (1959) biostratigraphic div ision of the Upper Cretaceous iI} Japan , r (s. str.) hobetsensis isa zonal index of the Upper lower Gyliakian (approximatel y Middle Turonian).
Accordingly, the stratigraphic position ofeach sample is considered as being approximately within the Middle Turonian.

648. Otoscaphites puerculus, an Upper Cretaceous Ammonite
Samples: I used 24 samples in thepresent study. Among them. 3 samples
were collected from the Naibuchi district,
namely N315d and 317d' near the confluence of the Naibuchi River and the
Ichinosawa River and N320 in the upperstream about 3 km apart from the confluence. These samples were collectedby MATSUMOTO in 1937. The detailed
localities are illustrated in MATSUMOTO(1942).
I used 16 samples from the Tappu
district. The fossil localities and theirstratigraphic positions are summarizedin Text-figs. 2, 3. 11 samples except
R2110b', R2110e', R40l8b, R4001d andR4022d were collected by T. MATSUMOTO, T. MURAMOTO, H. OKADA, H.
HIRANO and me in 1971. The rest of
the samples were collected by H. HIRANO
and me in 1973.
TANAKA (1963) lithologically subdivided
the Turonian in the district into several
members. But, according to my fieldobservations, the lateral changes of thelithofacies are rather great.
Accordingly, I used a zone as a key

Text-fig. 4. Map showing the fossil
localities in the Oyubari district (adaptedfrom MATSUMOTO'S unpublished data).

113

bed, characterized by large specimens ofI. (s. str.) hobetsensis and I. (s. str.) iburiensis NAGAO and MATSUMOTO, as wellas certain beds of tuffaceous rocks andUb member (TANAKA'S Kamikinenbetsu
sandstone member) (see Text-fig. 3).
I also used 5 samples from the Oyubari
district. These samples were collectedfrom the lower course of the HakkinzawaRiver, a tributary of the Yubari River,by T. MATSUMOTO in 1973 (Text-fig. 4).
Incidentally, a Middle Turonian Collignoniceras woollgari (MANTELL) was collected from loco Y5206d.

Methods of study
Generally speaking, adult shells form
the main part of each sample. In theadult specimens, the body chamber, including a pair of long lateral lappets, iscommonly in a good state of preservation
as well as phragmocone. This fact implies that the present species is suitablematerial for the morphologic analysis.
I prepared the data for the morphologic
analysis by measuring the median dorsoventral and the cross sections. Moreover,with respect to some favorably preserved
adult specimens, I calculated the volumeof the body chamber and the phragmocone after having separated them at thebase of the body chamber.
Morphologic analysis: Regarding theadult specimens, the coiling of the whorls
becomes b:>se from about 8-97r during
the ontogeny. However, the coiling pattern belongs to planispiral growth. Inorder to analyse the fundamental morphology biometric ally, I tried to polisheach specimen carefully along the dorsoventral plane. When the siphunculartube extended over one whorl at leaston the cutting plane, I regarded thespecimen as having been cut precisely
along the median dorsoventral plane.

114

Kaz~tshige TANABE" ···""'-,,···················r....---- RJ

R,: doualT.

:.----80;

Axi.s

E-i-r~~ ~-t~~-i~~~- of

..,c
"o
:E

coi lingR.

Text-fig. 5. Basic morphology, orientat'ion and measurements in medianand cross sections of scaphitoid ammonites.
,

As to the samples, R2110b' and R2110e',
I also performed the morphologic analysis
along the cross section. Each specimen
was cut at the base of the body chamber.
The basic morphology, orientation andmeasurements on both sections of" thepresent species "are diagrammaticallyshown in Text-fig. 5.
1Each character was measured with! amicrometer attached to a binocular microscope with magnification of 60 and 100
times. I also used a Wild microscope
and a wide-view projector for sketching
the magnified outline. The spiral length648. Otoscaphites puerculus, an Upper Cretaceous Ammonite
of walls was measured with a curvimeter.
The mersured value of each character isthe average of two measurements.
V olumometry : The volumometry of
the body chamber and the phragmocone
was done on 6 specimens of R2110a and2 specimens of R4018b. We are able tocube the volume of the solid (Vm) by thefollowing formula.
Vm=Wm-W:" ,where W m is the weight of the solid andW~, is the immersed weight. An automatic balance of accuracy, 1 mg, wasused for determining the weight.
Abbreviations: The following abbreviations are applied in the present paper.

For fundamental morphology
R : Radius from the axis of coiling(from the centre of the protoconch)
U : Umbilical diameter
B : Breadth of whorl
H : Height of whorl
C : Half length of umbilical diameter
W: Whorl expansion rate (Rn/Rn_l)2
D : Distance of generating curvefrom the axis of coiling (RIC)
T : Thickness of ventral wall
S : Thickness of septum
For biometry
N: Number of specimens in a sample
O.R.: Observed range
X : Arithmetic mean
V : Coefficient of variability (100s/X)
s : Standard deviationax: Standard error of the mean
P : Probability levelIi : Degrees of freedom
X±tO• 05 ax: 95% confidence intervalof the sample meana : Growth ratio
f3 : Initial growth index
r : Correlation coefficient
aa: Standard error of the mean ofgrowth ratio

115

Repository: All the specimens, except
for the Naibuchi samples of the University of Tokyo, are stored in the typecollection of the Department of Geology,
Faculty of Science, Kyushu University
with registered numbers begining withthe prefix GK. H.

Morphologic analyses
Individual relative growth
Growth of radius: It has long been
known that the growth of the whorl of
cephalopod shells displays a logarithmic
spiral (THOMPSON, 1917; HUXLEY, 1932).
OBATA (1959, 1960, 1964, 1965, 1967)
investigated the allometry of such Upper
Cretaceous ammonites as Reesidites minimus (HAY ASAKA and FUKADA), Desmophyllites diphylloides (FORBES), Damesites
damesi (JIMBO), Phyllopachyceras ezoense(YOKOYAMA), Neophylloceras subramosum
SPATH, Neopuzosia ishikawai (JIMBO) and
Gaudryceras tenuiliratum Y ABE.
In these papers, he realized that thegrowth of the radius in each species canbe plotted on a semi-logarithmic graphwith high degrees of correlation as afunction of polar coordinates. Moreover,
he pointed out that the growth patternis constant in each species.
Recently HIRANO (1975a, b) has studied
the ontogeny of some species of Upper
Cretaceous Gaudryceras from the viewpoint of population paleontology. According to him, each species can be divided
into several· growth phases. He showedthat the growth ratio in each growthphase is nearly constant within a species
and that the variability is relatively small_
We can determine the growth ratio of
the radius to the total rotation angle byusing the least squares method. The
equation is expressed as follows (THOMPSON, 1917; HUXLEY, 1932; OBATA, 1959,
1960, 1967).

116

J{azushige TANABE

log R=aO+c or R=(log c)·oa,

10,0where 0 is the total rotation angle and c
is a constant (log c is the initial growthindex).
If rearranged with eC->a, the equation
can be rewritten as follows:9,9:p

SSn 9.8

•

9,7

/1/

R. 0.17909°,.1'. r.O.999~

o R~ 0.1763 eo. I806 ,.0.9990:'.1

e D.1',4 ,.0.9995... IT.. R~ O.167~/'{+ h 0.23469 0 1,553 roO.9977

,/,}

9,6

:tj

4-S.SnR=a·eao •

9.5

•

.;<;

hO.JJ97eo. IJ63 •• 0.9983

01/:0.389:'9°.1167 •• 0.9999.r{/*.. Il100.32996°,12.0 •• 0.9996

9,'

In each growth stage, the spiral angle(w) between a tangent touching the generating curve at a point and a straightline connecting the centre of coiling anda point, can be obtained by the following
formula lOBATA, 1960, 1961).

,/'//,/ji,•tf+ 1/=0,370890.1206 .. 0.9993
9,3

.

9.2

'"

9,1

,I,

o R.Q431.cSQO . . . •• 0,999'.. ho.3HoSCl.IOU .. 0.9959+ 11_0,39<1890.103 ••• 0,9917

9,0

w=tan- 1 1/a .: w<90·0''i)'('

2-3.5".
• R_O.J8J8QD.IU ••• 0.997],,' ,/'
l/~

y,.r
•

I,{,'

8,9

In the case of the present species, thegrowth pattern of the radius exhibits theexistance of 4 growth phases, that is, the
1st (0"-' 1.51t'), the 2nd (2,,-,3.51t'), the 3rd(4"-'5.51t') and the 4th (5.51t'''-') stages during the ontogeny, as shown in Text-fig. 6
and Table 1.
A pronounced gap in growth can berecognized between the 1st and the 2ndstages in every specimen. This gap corresponds to the nepionic (first) constric-

8,8

8.7

•

R 4001d_loR401Bb-1..

R2113g-3+

R 21100-4

8,6e
Text-fig. 6. Phylogenetic changes ofgrowth of radius to total rotation angle.
Each specimen shows nearly the samevalue of the growth ratio of the sample
mean.

Table 1. Growth ratio of radius to total rotation angle
at the 2nd to the 4th stages for each sample.
S o .... p I,

.,;

NJI7d

~

j

N31Sd

Z

N320

';

2nd

I.
N

110 g.

I".,er.

14 _S,5J11: 1

D. R.

N

X i

...

., 0

g.

I.... er.

I 5,5Jr: -

1

O. R.

0.1002.10.0127

0.0186

0.0552 - 0,1267•

0.1 170 !0.01 18

0,01520,0877- 0.1407

O,IS76J.O,OI03

0.01110.1449- 0..1718

0.1060.t 0.0089

nOl34

0,1050 - 0.1069

3

o.124At.O,0331

0.01340.1144 .. 0.1397

0.1549 :,0,0430

0,01740.1361 .. 0.1705

0,00900,1582-0,174"

0.0835 ... 0.1118·

0,11"3.10.01.013

0,00890.1029 .. 0.12"90,16.40:1:0,0090

0.0955- 0,1054

2

O,I27H 0.0572

0.0063OJ23J- 0,132"

0,15"631

0,1026:1 0,0039

0,0107

0,0786" 0,1295

27

O,IH3:!: 0.0058

0,010150.1059 ... 0,1"98

2.

0,l610±O.o05S

0.0145

0,13 2 2.. O.IBA IS

2

I.

O,09tH 0.0,,07

0,00450.0885- 0,09"90,009"

0.1116 .. 0.12"90,00470,1630- 0.1696

0.01320.0903- 0.1189

O.II"st o,ooes

0,0121

0,0919-0.1372

I.

O,1663tO,O"190.10"3-±' 0.0095

I.

O,1183,tO,0839

O,1597-t0.0086

0,01200,1386- 0,1809•

0,1021:-0.0111

0.0095O,Oa97 .. 0.11 JS

O,l208tO.010S

0,00920,1091- O,lJAO

O,1603tO.0136

0,0"'40.1 "90- O,l7!i3

O,107"±0.0178

O,O'IH

0.0922" 0.1301

O,1128tO.0156

0.0097

0,0988- 0.1202

0,1601 ±O,O095

0.01300,1532-0,1675

121101",

2•0.1029±0,003B

0.00750.0891- 0.1180

0,l26a~0.00"90.00970.1101_0,1474

0.1618±0.0055

0,01100.1337- 0.1815

O,0999:1:-0,O1l0

0,01060,0900- 0.1131

0,1 192t 0,012-4

0.0077

0,1101- 0.1270

0.T713tO.0102

0,00120.1764- 0.1781

0.0066

0,0915 - 0,1025

0.12551: 0,0089

0,00.56

0.1182 - 0.1311

O,175l± 0.0127

0.00790,1697_0.1827

18

18

R2113h

•0.1012:0.0105

RAOl8b3

0.0879-1- 0,0370

0,01490.0728-0,1025

O,l184± 0,020l

0,00230.1167- 0,1200

O.l798±O,O150

0,009"

O,170a-O,192.5

RAOOld7

Q.I085t 0.02.50

0,0102

0.0988- 0,126.5

0.1311't 0.0121

0.01660.1111-0."'20

O,1818±O,o117

0,01280,1630-0,1966

YS218b

•0.0955± 0,0040

0,00610.0891- 0.1068

O,I12liO,0097

0.0126

O,1086-0,lA02

O,163JiO.OO5a 0,0076

O,I-45a-O,1738

Y520lr

8

0,10631' 0,0132

0.0158O,Oa72'" 0,1390

O,132atO.0102

0.0123

O,1078-0,IA59

0,l676t 0,0125

0,1359- 0.1 8 I"

0

"!

X i

0,0119UllOa

121139N

0,0070R2110b

R2110.

O. R.

0.097J.:tO,0147
2

R2110d3,.

12 -3.5'" 10,100510.0620

R2105b

R2110c1100_

X ± I .... cr•

0.0150648. Otoscaphites puerculus, an Upper Cretaceous Ammonite
tion. The size of the nepionic stage ofthe present species indicates a constantrange of nO,,-,890,u in each sample andis not changed with time. The coefficientof variability of each sample is small(V = 2,,-,6). The small gap in growth
between the 2nd and the 3rd stages isprobably referred to the nepionic constriction, because the range of the gap isnearly the same with that between the
1st and the 2nd stages. The growthratio of the 3rd stage is somewhat
greater than that of the 2nd stage.
In order to realize the differences ofgrowth ratio between the 2nd and the 3rdstages and also between the 3rd and the
4th stages quantitatively, I performed
the biometrical examinations On threesamples.
The results of the chi-square tests are
as follows.

The 2nd stage
N 317d: X2=0.48~3.84=Xg.05(Y=lh
R2110a: X2=O.39~7.82=Xij.05(Y=3h
R2110x: X2=1.38~5.99=Xij.05(Y=2h
The 3rd stage
N 317d: X2=O.52~3.84=Xij.05(Y=lh
R2110a: X2 =1.07 ~5.99=Xij.05(Y=2h
R2110x: X2=1.38~5.99= "The 4th stage
R2110a: X2=2.48~3.84=Xg.05(Y=lh
R2110x: X2=1.38~5.99=Xij.05(Y=2h
The results of the chi-square tests indicate that the null hypothesis of normal
distribution of populations is not rejected
for the character.
Next, I examined the differences of thevariances between the two growth stages

117

P~O.05,non-significant

/I

/I

1/

/I

P~O.05,non-significant

/I

/I

/I

1/

P~O.05,non-significant

1/

1/(F -test). The F -test, or variance ratio is
given by the following formula.
F=SI/S~.: SI>S2' lJl=N1-1, lJ 2=N2-1.
The results of the F -test are as follows.

Between the 2nd and the 3rd stages,
N 317d: F=1.84~3.39=F("=9,8) , P~O.05, non-significant
R2110a: F=1.84~2.37=F("=26,SO)' P~O.Ol,
1/
R2110x: F=1.68~2.31=F("=17,17l' P~O.05,
1/
Between the 3rd and the 4th stages,
R2110a: F=1.00~1.90=F("=28,26)' P~O.05, non-significant
R2110x: F=1.29~2.31=F("=17,17l'
1/
1/
The results of the F -test indicate thatthe differences of the variances between
the two growth stages is not significant
with 95% or 99% confidence.
The difference of the mean between thetwo samples can be determined by thefollowing well-known formula (Student's
t-test).

I(N 1 -1)· S~+(N2-1)· s~.y

N1+N 2-2

lJ=N1+N 2-2.
Using this formula, I calculated thatvalue in each sample.

Kazushige TANABE

118

Between the 2nd and the 3rd stages,
N 317d: It I =2.14~2.l1=to.o5("=17), P<{O.05, significant"
R2110a: It I =6.56~2.00=tO.05("=56)'"
R2110x: Itl =8.28~2.04=to.05("=3j),""
Between the 3rd and the 4th stages,
R2110a: Itl =9.47~2.00=tO.05("=54)' P<{O.05, significant/I"
R2110x: Itl =10.l5~2.04=to.o5("=34)'
The results of the t-tests show thatsignificant differences in the growth ratio
exist between the 2nd and the 3rd stages
and between the 3rd and the 4th stages
with 95% confidence.
The growth ratio of the 3rd stage isnearly constant over time, but that of the
4th stage gradually increases with time.
In every sample, the difference in thegrowth ratio between the 3rd and the 4thstages is greater than that between the
2nd and the 3rd stages.
The spiral angle of the 4th stage decreases with time in accordance with theincrease of the growth ratio as shown in
Table 2. The variability in each sample
is extremely small.

Table 2. Measurements of spiral angle of the 4th stageof Otoscaphites puerculus (JIMBO) (in degrees).
SampleN

X ±to•05G.i

R2105b
R2110a
R2110b
R2110c
R2110dR2110f
R2110xR2113g
R2113h
R4018bR4001d

1
29
2
16
5
4
18
2
4
4
7

83.55
83. 28±0. 23
83. 07±1. 71
83. 59±0. 28
83. 24±0. 61
83. 32±0. 38
83. 25±0. 22
82.61 ±O. 51
82. 70±0. 53
82. 51±0. 62
82. 42±0. 49

RAUP (1965, 1967) developed the methodof morphologic analysis of coiled ammonites using two simple parameters, thewhorl expansion rate and the distance ofgenerating curve from the axis of coiling(Text-fig. 5). Using this approach, I examined the ontogeny of R2110b' andR2110e'. The results are shown in Textfig. 7. During the ontogeny, the present
species displays the increase of whorl
expansion rate and the decrease of dis-

V

I

/

/

o. 72

0.60
0.19
0.13
0.49
0.24
0.45
0.06
0.33
0.39
0.53

0.23
0.63
0.58
0.29
0.55
0.07
0.40
0.47
0.64

O.R.

s

I
I

!
I

I
I

83.55
82.30-84.48
82.93-83.20
82.46-84.21
82.69-83.78
83.01- 83. 60
82.44-84.41
82. 57 - 82. 65
82.39 - 83.03
81. 98-82.88
81. 89 - 83. 20

tance of the generating curve from theaxis of coiling.
Growth of whorL height, breadth andumbiLicaL diameter: From the results ofgrowth of radius, the present species canbe divided into two main growth stages,
O'"'-'5.5n- and 5.5n-'"'-' , as a whole. In thepresent study, I examined the growthof whorl height, breadth and umbilical
diameter to· shell diameter by means of
the reduced major axis method (KERMACK

648. Otoscaphites puerculus, an Upper Cretaceous Ammonite
Distance of generating curve from axis

(e/R)

l°r--.__~Or·'__.-~Or<__,-~OTP__.---;O'

o

~

2
N

.~1

c,

.",

.D

C

0.'"

o

Text-fig. 7. Ontogenetic changes ofmorphology, expressed by distance of generating curve from axis and whorl expansion rate. Scale models are adopted from
RAvp (1967).

and HALDANE, 1950). The results are
summarized in Table 3. A pronounced
critical point of growth is observed atTable 3.

119

the point of 5.57C in every specimen(Text-fig. 8). The growth pattern expressed by these characters is almost
harmonious with that of the radius.
HAYAMI and MATSUKUMA (1970) proposed a method of approximate discrimination of allometry using the reduced
major axis. According· to them, therange of isometry is represented by thefollowing interval with 95% confidence(small sample method).
1- to.o6Sa < iV <1+ t o•o6 sa-VN =C'=-VN

where a and Sa are the mean and thestandard deviation of the growth ratio.
Using this method, I tried to discriminate
the allometry of the present species. The
results are appended in Table 3. As to
the growth of whorl height and breadthto shell diameter of every specimen,

Ontogenetic allometry of Otoscaphites puerculus (lIMBO),
calculated along the cross section.

Early stage (0-5.51t)
SampleN

a±tO•06 u"

Sa

O.R.

Allometry

R2110b!

50.8209±0.1122

0.09

0.6616-0.8850

negative

R2110e';;o. 7436±0. 1188

0.10

0.6138-0.8435

R2110b';;0.6431 ±O. 0744

0.06

0.5798-0.7229

R2110e'6o. 7037 ± o. 0848

0.08

0.5740-0.7807"""

R2110b'5

1. 3264±0. 1688

0.14

1. 2129:....1. 5523

positive

R2110e'6

1. 3589±0. 2545

0.24

1. 0045 -1. 6623"

a±tc.or,u"

Sa

O.R.

Allometry

H to D

B to DU to D
Later stage (5. 51t-)
SampleN

R2110b';;1. 2423±0. 1824

O. 15

1. 0158-1. 4216

positive

R2110e'6

1. 1856±0. 0452

0.04

1. 1364-1. 2465,"

R2110b'5

1. 14l9±0. 1035

0.08

1. 0624-1. 2723

R2110e'6

1. 0870±0. 0500

0.05

1. 0260 -1. 1511""

R2110b'50.8002±0.1466

0.15

0.6778-0.9904

negative

R2110e'5

O. 7714±0. 0763

0.07

0.7010-0.8351"

I

H to D

B to DU to D

120
E
E

Kazushige TANABE

5

c

3

==a

"tI

!

2

-"

~
0

.

"".~
"" 0.5a""~ 0.3
0.2

0.1
0.5

0.2

10
Shelr

diameter in mm

Text-fig. 8. Ontogenetic allometry ofwhorl height (H) and breadth (B) to shell
diameter of R 2110e'-3.

NegativeallometryI

the growth ratio changes from negative
allometry to positive allometry during the
ontogeny.
On the contrary, that of umbilical
diameter against shell diameter changes
from positive allometry to negative allometry.
Consequently, the growth pattern interms of the above-mentioned three characters represents the fundamental morphology of the present species.
Growth of septal and ventral wall thickness: In the next step, I tried to investigate the growth of septal and ventral
wall thickness to radius using the
reduced major axis method again. The
chronological changes in the growth ratioof both characters are illustrated in Textfigs. 9-10. Furthermore, the ontogenetic

Positiveallometry

500~~~~~~~~~~------~~~~~~-r~~~~~--------4

LEG END

R 4001dto.osCl"aN-S \("'~~2s""'7"observed ro~ge"

400
R4018b

300

E
c:

4
I

0
N

R 2113h
R 21139

I,

3
c:

I
I

2001--

+

7
0

6

J:

6

I

,

r=-===mz
I
I

>-

.

~

'"

o?

1001;-

::;"

..

E
0

... +
ia

=

11

R 2110 x"""" 9

12

I. ,

" °9.

1®«!'

®

0

0

2

1

Grow t h

Text-fig. 9.

R2110 c
R2110 aR 2105 b

3

ra t i 0 (ex )Changes in growth ratio of the reduced major axis of septal thickness
to radius in samples from the Tappu district.

648. Otoscaphites p~£ercul1,£s, an Upper Cretaceous Ammonite

121

500~N~e~g~a~t~iv~e~a~I~lo~m~e~t~rLy_~I____~p~o~s~i~t~i~v~e-.~o~I~I~o~m~e~t~rLY______-1
LEGEND

R4001d

I

1
I

1
1
I
1

400

"f*"" 5

R4018 b

1

1
1

E 300

I
~4

+

1®

I:

o

R 2113 h
3 R2113g

N

~

200_

I

.;+

6

o
J:

®1

I

+

7

>-

~

~'"

100

;:'"

1®

.,

11

-+-

(0

'E"
"I

I

R 2110 x
R 2110d
R 2110 c
0----13
R21100-" 09 •

0

0

'.,

7

R2105bI:

1°O~----------------L---------------~----------------~
2
Growthrotio (o<J

Text·fig. 10. Changes in growth ratio of the reduced major axis of ventral
wall thickness to radius in samples from the Tappu district.

allometry of some specimens from different horizons is exemplified in Textfig. 11. The results indicate that a plain
critical point exists in the samples fromthe lower horizon (R2105b.-v R2113g).
In these samples, the growth ratiochanges from negative allometry to positive allometry at about the 7.57C stage.
However, the growth ratio of the laterstage (from 7.57C) gradually decreased
with time, and R4018b and R4001d indicate isometry ot slight negative allometry.
At the stage of 8.5.-v97C, the whorl of thepresent species begins to be loosely coiled,therefore, the growth of the ventral wall
thickness is expressed not by the ratioof thickness to the diameter but that ofthickness to the spiral length of ventral
wall. The growth pattern is exemplified

in Text-fig. 12. The thickness continues
to increase until the point far apart fromthe centre of coiling and finally it decreases abruptly to this side of the apertural constriction. The thickness indicates the maximum value at the apertural constriction.
Relative variation
The present species has a conspicuous
constriction and a pair of long laterallappets on its apertural margin. As
ARKELL (1957) pointed out, the shellhaving these characters may be considered as adult.
In the next part of the study, I examined the relative variation of the present species.
Maximum diameter of phragmocone:
In order to ascertain the variation of

122

Kazushige TANABE
1105

0,05

R4001d·2

R4.001d-l

T.O,OIO~o.s66
r.O,9920

T.O,OOeR

0.9317

rcQ9940

0,01

0.01
0.2

E
E

0,3

0,1

0.05

r.0.9891

R2110x-6........

"0.9945
R2110k-12

E
E

..."

..

c

U

c

,-

0.01

·····T"'O.OI3R Q941..c 0.01

r:.O,9752........ Ta O.01ORD.674"

0,1
T:o 0.0002 R2.D27~
R2110a-JO

r.o.9285

C

-"
u

0.2

-

TaO.OOOSRI.339

0.05

T=0.0007 R',56.

C

0

10

.r. 0.05

r=O,9979" ....

R2110a-13

0.05

0

10

0.>

0

.

Il.

c

41 0.01>"·'--i.o.ooe R0. 7 • 2

U)r.O.9847, .. 0,9955

0.01
0.2

10

0,3

0.08
0.05

0.05

Nl15d-2

Y 5218b-J

0.03
0,03
r=0.9921

0,01

0.01

0,2

~ze

0.3

0,5

RadiusText-fig. 11.

T.O,0003 R' ,65'

0.02

0.02

in mm

10

QS

Radiusin mm

Ontogenetic allometry of ventral waH and septal thickness
to radius of selected specimens.

of the phragmocone quantitatively,

X±fo.os(1x, V, sand O.R. were calculated

in each sample. The results are summarized in Table 4. The maximum
diameter of the phragmocone increased
rapidly with time.
Spiral length of body chamber: In thefirst place, the spiral length of the ventral and dorsal walls were separetely
calculated for each adult specimen fromthe Tappu district. For specimens hav-

ing nearly the same value of the sample
mean, the reconstituted length of the
body chamber was estimated. As thereconstituted lengths are almost the same
between the, ventral and dorsal walls, I
have shown the length of the ventral
wall in the examples (Text-fig. 13). The
spiral length is gradually shortened about
0.47[' from R2106h (ca. 1.637[') to R4018b(ca. 1.207[').
TRUEMAN (1941) estimated the length648. Otoscaphites puerc1£lus, an Upper Cretaceous Ammonite
mm

mm

.3

.3

-

C .2

o

R2110x-3~.

91t: ......

0

a

~

0

o
0

.2

R 21139-3

~

"0

~

.1

>

.08

~

:: ,05~c-".~ .03.<:·-~·····7.sX... .02•02.: body chamber
01 7

10

20

30

SO

.01 L---"L---:'=---'--:!-..J....l...LLJ,-,10
20
30
SO
100mm

100mm

length of ventral wall

length of ventral wall

Text-fig. 12. Ontogenetic changes of ventral wall thickness tospiral length of ventral wall of R 2110 x -3 and R 2113g-3.

Table 4.

Measurements of maximum diameter of phragmocone in adult specimensof Otoscaphites puerculus (lIMBO) (in fl.).

SampleN

X±tO.Onl1x

V

s

O.R.

N317d
N315d

3
2

7302. 33 ± 775. 83
9072. 00 ± 6670. 69

4.28
8.18

312.35742.466944- 7517
8547- 9597

R2105b
R2106h
R2106q
R2110a
R2110b .
R2110c
R2110dR2110f
R2110xR2113g
R2113h
R4018b
R4022d

1
3
1
31
3
14
6
2
19
4
4
5
1

8642
8565. 59 ± 1477. 16
94209377.16± 186.08
8598.92 ±2219. 59
9397. 14± 462. 07
9485. 34 ± 672. 67
8973. 50±5216. 199655.14± 335.81
10247.61 ± 464.28
10813.79± 957.81
11 761. 20 ± 1038. 49
14342

/
6.94

/
594.618642
8077- 9228
9420
8353-10396
8025- 9628
8408-10747
8973-10650
8563- 9778
8730-10948
9874-10588
10147-11591
10817-12882
14342

Y5218b
Y5205
Y5201r
Y5201a7
1
68539. 29 ± 498. 429515
9423.17± 625.45
11537

~

0,

.,

/

/

5.41
10.39
8.52
6. 76
6. 74
7.22
2.85
5.57
7.11

507.37893.46800.43640.88580.5!l696. 70291. 81602.02836.52//6.31

538.91/6.32/
595.89//7893- 9315
9615
8556- 9985
11537

123

124

Kazushige TANABE
Reconstituted...

length of body chamber in normal coiling
li-9HN·21
I
I
I

I
I

I
I

R2113g-3

EE

c "r---~----~----~----t---~----~~~~--~~-~ "R2110.-13

.
c

>

o

l0r---~----~----~----r---~----~--~~--~
R2110a-21

.

!

50

g>

R2106h-1

Ph rag mocon e

Body

chamber

Text-fig. 13. Changes of reconstituted length of body chamber
in normal coiling. Each specimen shows nearly the same valueof the sample mean.

of the body chamber on about 81 speciesof ammonites. According to his data,almost every ammonites has a bodychamber longer than In". In the present
species from the upper horizon, the bodychamber is relatively short.
Shape of the adult shells: COBBAN(1951) and WIEDMANN (1965) made clear
the trends of evolution of the scaphitoid
ammonites above the species level. According to them, the shape at the adultstage gradually changed from abnormal
to normal coiling with time in accordancewith the increase in rate of the overlapping of whorls.
In the present species, the same pattern
can be expected. To realize the chrono·
logical change of the shape at the adultstage, I examined the two characters,
Wand D for each specimen from theTappu district. The results are shownin Text-fig. 14. As might well be expected, the change is similar to those of
W orthoceras and some stocks of Sraphites
studied by WIEDMANN (1965).
Umbilical diameter: KUMMEL and
LLOYD (1955) and RAUP (1967) pointed
out that the rate of overlapping of whorl
is an important character in considering
the stability and the relative streamliningof the shell in the floating and the swimming positions. RAUP (1967) realizedthat an evolute shell has generally alonger body chamber than an involute·
shell.
Subsequently, I examined the ratio ofumbilical diameter to shell diameter foreach adult specimen from the Tappu
district. The chronological change ofthe ratio is illustrated in Text-fig. 15.

648. Otoscaphites puerculus, an Upper Cretaceous Ammonite

Number of septa and volutions: The
number of septa for each adult specimen
is nearly constant (40rv 57) and not sochangeable with time. The coefficient ofvariability ranges from 4 to 8. The number of volutions of the phragmocone foreach adult specimen is also constant(7.83,.....,9.69n) with time and the coefficientof variability is relatively small value

c

.~~

•

C

125

(V=2 rv 6).

T
C

00:
0. ....
•

C.0:

Functional considerations

Text·fig. 14. Phylogenetic changes ofmorphology and stability index in adultspecimens from the Tappu distlict. Sta·bility index is adopted from RAUP (1967).

C

'-,OO

,
~

.2I1lh.,..1.2I1l' ..... '

",
L;'-

12110',"'.13
121101,101. :I.21101t.No 1
12110c.No10'2110b",," 3'2110",1'1.26

Umbiticus/ Diom.'.r

Text·fig. 15. Changes of ratio of urn·
bilical diameter to shell diameter in adultspecimens from the Tappu district.

The present species gradually changed
from moderately evolute -(40-50%) tomoderately involute (ca. 30%) with time.
The results can be applied to RAUP'S(1967) generalization.

Buoyancy of an empty shell: Here I
consider the buoyancy of the present
species on the ground of analyses of theindividual relative growth and the relative variation.
The maximum diameter of the phragmocone in each adult specimen from theTappu and the Oyubari districts rapidly
increases with time. Furthermore, thegrowth ratio of septal and ventral wall
thickness to radius of the later stage(from ca. 7.5n) gradually decreases frompositive allometry to isometry or slightnegative allometry. The growth ratioof
these two characters at the stage for the
samples from the lower horizon (R2105b",
R2110x) is much smaller than those of
normally coiled ammonites, as realized
by TRUEMAN (1941) and WESTERMANN(1971). The growth pattern of whorls of
the present species implies the increaseof the area of cross section with time.
As THOMPSON (1917) pointed out, thevolume of the body (Vb) increases in
direct proportion to cube of the length(L), as represented by the following
formula.
Vb=k·V,
where k is a constant.
Consequently, the growth pattern ofthe present species suggests an increaseof buoyancy of the shell with time.

126

KaZ~t8hige

To test this, I calculated approximately
the buoyancy of some well-preserved
specimens of R2110a and R4018b. There
are three methods for estimating thebuoyancy of ammonoid shells.
TRUEMAN (1941) calculated the buoyancy of Promicroceras marstonese SPATH,a Lower Jurassic ammonite after having
measured the internal volume of camera
and body chamber and the volume ofshell material.
MOSELEY (1838), TRUEMAN (1941), RAUP
and CHAMBERLAIN (1967) used simple
equations for calculating the buoyancy of
cephalopod shells. However, these equations may not be applied directly to actual
specimens, because they were obtained
from idealized models.
REYMENT (1973) and RAUP (1973) madefloatational experiments using modern
Nautilus shells and models of ammonoid
shells. As REYMENT (1973) mentioned,
this method is the most useful for studying the buoyancy of shells. But very
well-preserved shells, completely separated from the host rock and if thecamerae are not empty, the time-consuming technique of serial sectioning andmodelling must be resorted to thismethod.
Unfortunately, it is difficult to separate
completely the shell material from thehost rock for the specimens at my disposal.
To calculate the buoyancy of the shell,
the internal volume of camera and bodychamber and the volume of shell material
are required. We can calculate thevolume of phragmocone and body chamber including the shell material. If weassume the present species to be a conewith a circular cross section, the base of
the cone can be conputed from length ofthe cone.
The approximate length of the cone (L)is expressed by the following formula.

TANABE

L=1/2 (total spiral lengths ofventral and dorsal walls).
The volume of the shell material (V.)
is represented by the following formula.

V.=1/3 L.(S-S') ,where S is the base of the cone, including the shell material, and S' is the internal area of the base. The wall thickness
at the base is expressed by the maximum
thickness of each specimen at the apertural constriction.
According to RAUP (1973), the proportion of flooding necessary to sink an
empty shell (F.) is expressed by the following formula.
F.=[pw·(Vt - Vb)-p.,· V.J/pw· V p ,where V t is total volume of water displaced by a shell plus animal, Vb is volume of animal, assumed to be equivalent
to that of body chamber, V. is volume ofshell material, V p is volume of camerae,
Pw is the density of water and p. is thedensity of shell material. P. is assumed
to be 2.62 (REYMENT; 1958, 1973) and1.00 is used for pw.
Using this formula, I calculated thebuoyancy index (F.) for each specimen.
The results are summarized in Table 5.
Additionally, the data of two species of
Nautilus and 6 species of ammonites,
studied by HEPTONST ALL (1970) and
RAUP (1973) are appended in Table 5.
TRUEMAN (1941) weighed several septaof such Jurassic ammonites as Promicroceras marstonense SPATH, Dactylioceras
commune (SOWERBY) and Ludwigia bay lei
BUCKMAN. The proportion of the weightof septa is about 2",6% of the total shellweight for each species.
HEPTONST ALL (1970) calculated thecorrection value of Fa after the reconstruction of the soft parts. The correction value is about 0.10",0.25, subtracted
from the value of an empty shell (Table 5).

648. Otoscaphites puerculus, an Upper Cretaceous Ammonite

127

Table 5. Calculated buoyancy index (F.) (the proportion of flooding necessary
to sink an empty shell). ** Data from RAUP (1973), *** Data from HEPTONSTALL(1970), V p: Volume of phragmocone Vb: Volume of body chamber, Va: Volume ofshell material.
Specimen

Vp

Vb

Vs

V"VP+Vb

VbVP

F.

R2110a-l-2--3-40.18 cc
0.18
0.19
O. 18
0.14
0.22

0.41 cc
0.45
0.48
0.51
0.45
0.51

0.149 cc
0.236
O. 148
0.246
0.169
0.226

0.202
0.273
O. 181
0.277
0.223
0.236

2.28
2.50
2.53
2.83
3.21
2.32

-0.345-1. 129-0.246-1. 377-0.957-0.651

O. 74
O. 76

O. 1270.181

O. 101

1. 90
1. 81

+0.472+0.302-;)-6
R4018b-l
-2

0.39
0.42

I

0.133

Promicroceras marstonense ................. . 0.089
2.80+0.423**+0.338***Dactylioceras commune . .................... . 0.075
3.30+0.458**+0.223***
Ludwigia baylei ........................... . 0.081
2.36+0.540**+0.520***
2.00
0.089
+0.545**Chondroceras sp ............................ .
+0.464***2.00+0.346**
Asteroceras smithi ......................... . 0.123+0.264***7.50+0.507**+0.248***Liparoceras subcrenatum ................... . 0.036
Nautilus pompilius ...... _.................. . 0.100
3.60+0.206**
Nautilus macromphalus ............................................ +0.08-0.14***

Every specimen of R2110a indicates anegative value of F.. Even if we takethe effect of the phragmocone into consideration, it would be difficult to float
these specimens in sea water.
On the contrary, two specimens of
R4018b could have floated easily under
the non-flooding condition. Their valueof F. is nearly the same as those of normally coiled ammonites, listed in Table 5.
Furthermore, the two specimens could be
more buoyant than Nautilus pompilius
LINNE and N. macromphalus SOWERBY.
Streamlining: Experimental studies on
the relative streamlining of ammonites
were made by KUMMEL and LLOYD (1955).
They measured the drag force acting on
the plaster models of ammonites in acurrent of water. From the results of
their experiments, they concluded theevolute shell forms tend to be less stream-

lined than the involute and highly ornamented forms.
As to the present species, the surface
ornament (rib and tubercle) of the bodychamber became weaker in accordancewith the increase in rate of overlappingof whorls (see Plate 10). From this evidence, it may be inferred that the present
species became more streamlined withtime. But in order to study the relative
streamling of the present species quantitatively, further detailed analysis of thesurface ornament is needed as well ashydrostatic experiments.
Preliminary consideration on the functional evolution: Here I consider thefunctional evolution of the present species. The study on the individual relative growth and the relative variation
indicates that the present species evolved
rapidly.

128

Kazushige TANABE

The results of the buoyancy calculations suggest that the mode of life at
the adult stage changed from benthic tonektoplanktic.
RAUP (1967) and RAUP and CHAMBERLAIN (1967) developed graphically the
relation between shell morphology andthe stability in the floating position,
based on computer analysis of the simulation models. According to them, thestability index is expressed by the distance between the centre of gravity andthat of buoyancy, divided by the shell
diameter.
The chronological change in stability
is shown in Text-fig. 14. The stabilityof the adult specimens gradually decreased for the samples from the Tappu
district.
REYMENT (1973) pointed out that a decrease of the stability is not favorable
for maintaining the vertical position. As
the stability index of the present species
is relatively high, it may be postulated
that the present species could not swim
as quick as the normally coiled ammonites.
It may also be suggested that thepresent species from the lower horizon(R2105b to R21l0x) changed its mode oflife from nektoplanktic to benthic during
ontogeny. The growth of septal andventral wall thickness to radius at theearly stage (O"'ca. 7.5n-) of these samples is negatively allometric as well as
those of normally coiled ammonites by
TRUEMAN (1941) and WESTERMANN (1971).
Unfortunately, I could not calculate thebuoyancy of any young specimen, because of ill-preservation of body chamber.
For considering the function of ammonites, such characters as the siphunculartube, the septal suture. and the shape of
the apertural margin are also important
as well as the characters discussed in thepresent paper. It is absolutely necessary

for a precise discussion of the functional
morphology of ammonites to analysethese characters quantitatively.
The functional evolution of the present
species is tentatively summarized in
Text-fig. 16.
Conclusions

Otoscaphites puerculus (JIlvIBO) is a
Turonian ammonite which is locally distributed in Japan and Sakhalin.
On the grounds of biometrical andhydrostatic treatment of about 150 individuals belonging to 24 samples whichwere collected from the Middle Turonian
in south Sakhalin (Naibuchi district).
northern central Hokkaido (Tappu district) and central Hokkaido (Oyubari district), the following functional significance has been made clear.
The analyses of individual relative
growth and relative variation indicatethat the present species evolved rapidlyin accordance with the increase of internal volume of the phragmocone, the decrease in volume of shell material andthe shortening of the body chamber in
the adult stage.
The approximate calculation of a buoyancy index (the proportion of flooding
necessary to sink an empty shell) suggests that the mode of life at the adultstage changed from benthic to nektoplanktic during the course of evolution.
References
ARKELL, W. J. (1957): Introduction to Mesozoic Ammonoidea In MOORE, R.C. (ed.)
Treat. Invert. Paleont., Part L (Mollusca4), p. LSO-Ll2S. Geol. Soc. Amer. &Univ. Kansas Press.
BIDDER, A. M. (1962): Use of tentacles,
swimming and buoyancy control in thepearly Nautilus. Nature, vol. 196 (4853),

648.

The

of

trend

Otoscaphi tes

~

c

~

puerculus

,..
'0 E
'0 E
0
.0
K
.c

Phragmocone

evolution

in

Age

E

~

~

.~.=.~
E

0

'"

>

'""

~

E

0>

.:

~.c

~ ~

~

~

-."
0 0

u

~

0

.-

~

.-

R4018b-2

«

z

Z

"

OJ

"-

"0

0-

N

0

"C

..
41

Z

C

0

""
::>

to.
"-

41
~

..

u

c:

""Z "C41
OJ
OJ

'"9
,

;:!.
OJ

0-

"C

41

,

C
IV

u

c:

C
41

C
41

~

u
41

u
41

u

"C

"C

6
"C

41
.0
0

Q.

... "C

OJ

.

0-

w

0

0

M

~

OJ

"-

- z"

Q.

c

c

c

:J

:J

:J

:J

c~

"C

"C

"C

"C

C

C

C

C
~

C
Cl

Cl

c:i

41

u
r:::

t

0

:i:

:.'""

>.

0-

C

c:i

:J

OJ

C

, "C

d
u

ci

Cl

Cl

1 ....

Q.

C
41

N

>.-

>.

c

0

"C

""
Z

o ~.

>.

0

.c:

>.

....c:

41

.c: ~

c:

""d

0
M

Z

.... >I
~

....

....0

0

"

C
41

>.
0).."

c:i

u

"C
41_
r:::N

"C
41

0

~

"

c:i

4I Z

l-

r:::
41

"C
41

0

."

N

"-

d

i

-.
U

0

r:::
N

c

,..."

~

'"

'"

N.

41

~

0

<;I

0

i to i i

0

z"

~:

M

K

N

-0

0

e

"

Z

"".

"-

.e

u

~..o

N

;;;

,..

~ >..0

z
:j

N
N
OJ
N

.c

..a."
,.. -;;,,..
0 c
c ."

E u

~

';0 a. '~oD

':?

~

Z

129

Otoscaphites ]Juercul1Ls, an UPPe?" C1'etaceo1Ls Ammonite

Cl

R2110x-l

.c:
0
0

~

:J

M

-0

0()

-~:

z

E
C

0M

0

41
u

M

'"
M
OJ

0

c:

'J

z

OJ
N
N

E

.

0-

"-

"-

R2106h·l

0

OJ

z"
N
N

d

""

0

-0

z

e=
'"0
""

ClN

0()

""
"
z" .c:=

Z

0

-0

N

N

'"~"
~

0

"

c:i

0

0-

OJ

ci

~

u

.c:
r:::
41
al

z"

"

Z

~

M

0

:3

N

0

ci

u

Text,fig. 16. Functional evolution of Otoscaphites puerculus (Jr:vmo)(Fundamental data based on the samples from the Tappu district).

130

Kazushige TANABE

p. 451-454.
CHAMBERLAIN, J. A., Jr. (1969): Techniqueof scale modeling of cephalopod shells.
Palaeontology, vol. 12, pt. 1, pp. 48-55,
pI. 7.
COBBAN, W. A. (1951): Scaphitoid cephalopods of the Colorado Group. U. S. Geol.
Surv. Prof. Paper 239, 42 pp., 21 pis.
COLLINS, D. H. and P. MINTON (1967):
Siphuncular tube of Nautilus. Nature,
vol. 216 (5118), pp. 916-917.
DENTON, E. J. and J. B. GILPIN-BROWN (1961) :The distribution of gas and liquid within
the cuttlebons. Jour. Mar. Bioi. Assoc.,
U. K., vol. 41, pp. 365-381.
- - (1963): On the buoyancy of the pearly
Nautilus. Jour. Physiol., vol 168, pp. 4445.
- - (1966): On the buoyancy of the pearly
Nautilus. Jour. Mar. Bioi. Assoc., U. K.,
vol. 46, pp. 723-759.
- - (1973): Floatation mechanisms in modern and fossil cephalopods In RuSSEL,
F. S. and M. YONGE (ed.) Advances inMarine Biology, vol. 11, pp. 197-268.
Academic Press, London.
HAYAMI, 1. and A. MATSCKUYIA (1970):
Variation of bivariate characters fromthe standpoint of allometry. Palaeontology, vol. 13, pt. 4, pp. 588-605.
HEPTONSTALL, W. B. (1970): Buoyancy control in ammonoids. Lethaia, vol. 3, no.
4, pp. 317-328.
HIRANO, H. (1975a): Ontogenetic study ofLate Cretaceous Gaudryceras tenuiliratum.
Mem. Fac. Sci., Kyushu Univ., ser D, vol.
22, no. 2. (in press).
- - (1975b): Ontogenetic study of Late
Cretaceous Gaudryceras denseplicatum.
Trans. Proc. Palaeont. Soc. Japan, N. S.
(in preparation).
HUXLEY, J. S. (1932): Problems of Relative
Growth. Dial Press, New York. 276 pp.
JIMBO, K. (1894): Beitrage zur Kenntnis derFauna der Kreideformation von Hokkaido. Palaeont. Abh., Neue Serie, vol. 2,
no. 3, 47 pp., 9 pis.
KERMACK, K. A. and J. B. S. HALDA:\"E (1950) :Organic correlation and allometry. Biometrika, vol. 37, pp. 30-41.
KUMylEL, B. and R. M. LLOYD (1955): Experiments on relative streamlining of
coiled cephalopod shells. Jour. Paieont.,
vol 29, no. 1, pp. 159-170.
MATSUMOTO, T. (1942): Fundamentals in
the Cretaceous stratigraphy of Japan.

Explanation of Plate 10
Otoscaphites puerculus (]l1\1Bo) ........ (All x 2)
Arrow points to the base of body chamber
Fig. 1.
Fig. 2.
Fig. 3.
Fig. 4.
Fig. 5.
Fig. 6.
Fig. 7.
Fig. 8.
Fig. 9.
Fig. 10.
Fig. 11.
Fig. 12.
Fig. 13.
Fig. 14.
Fig. 15.

Lateral (a) and ventral views of GK. H. 5709, R 2110a.
Lateral view of GK. H. 5710, sample ditto.
Lateral view (a) and median section (b)of GK. H. 5711, sample ditto.
Lateral view of GK. H. 5712, R 2110b.
Lateral view (a) and median section (b) of GK. H. 5713, R 2110c.
Lateral view of GK. H. 5714, R 2110d, immature shell.
Lateral view of GK. H. 5715, R 2110c.
Apertural part of GK. H. 5716, R 2110x.
Lateral (a) and ventral (b) views of GK. H. 5717, sample ditto.
Lateral view (a) and median section (b) of GK. H. 5718, sample ditto.
Lateral view (a) and median section (b) of GK. H. 5719, R 2113g.
Lateral view (a) and median section (b) of GK. H. 5720, sample ditto.
Lateral view of GK. H. 5721, R 2113h.
Lateral view (a) and median section (b) of GK. H. 5722, R 4018b.
Median section of GK. H. 5723, R 4001d.

TANABE:

Functional morphology of Otoscaphites

Plate 10

648. Otoscaphites puerculus, an Upper Cretaceotts Ammonite
Part 1. Mem. Fac. Sci., Kyushu Imp.
Univ., ser D, vol. 1, no. 3, pp. 133-280.
--- (1959): Zonation of the Upper Cretaceous in Japan Mem. Fac. Sci., Kyushu
Univ., Ser. D, vol. 9, no. 2, pp. 55-93,
pis. 1-2.
- - (1965): A monograph of the Collignoniceratidae from Hokkaido. Part 1.
(Studies of the Cretaceous ammonites
from Hokkaido and Saghalien-14). Ibid.,
vol. 16, no. 1, pp. 1-80, pis. 1-18.
- - and H. OKADA (1973): Saku formationof the Yezo geosyncline (in Japanese).
Sci. Rep., Dept. Kyushu Univ., vol. 11,
no. 2, pp. 275-309.
MOSELEY, H. (1838): On the geometricalforms of turbinated and discoid shells.
Phil. Trans. Roy. Soc. London 1838, pp.
351-370.
MUTVEI, H. and R. A. REYMENT (1973):
Buoyancy control and siphuncle functionin ammonoids. Palaeontology, vol. 16,
pt. 3, pp. 623-636.
OBATA, 1. (1959): Croissance relative surquelques especes des Desmoceratidae.
Mem. Fac. Sci., Kyushu Univ., ser D,
vol. 9, no. 1, pp. 33-45, pis. 4-5.
- - (1960): Spirale de quelquse ammonites.
Ibid., vol. 9, no. 1, pp. 151-163, pI. 15.
- - (1961): Growth analyses in palaeontology (in Japanese). Earth Science, no.
55, pp. 23-28.
- - (1964): Notes on ontogeny of Reesidites
minimum (in Japanese). Fossils, no. 8,
pp. 94-102.
- - (1965): Allometry of Reesidites minimus, a Cretaceous ammonite species.
Trans. Proc. Palaeont. Soc. Japan, N. S.,
no. 58, pp. 29-63, pis. 4-5.
- - (1967): Notes on relative growth inpalaeontology (in Japanese). Fossils, no.
14, pp. 20-39.
RAUP, D. M. (1966): Geometric analysis ofshell coilng: general problems. Jour.
Paleont., vol. 40, no. 5, pp. 1178-1190.
- - (1967): Geometric analysis of shellcoiling: coiling in ammonoid shells.
Ibid., vol. 41, no. 1, pp. 43-65.

131-_. (1973): Depth inferences from vertically embedded cephalopods Lethaia, vol.
6, no. 3, pp. 217-225.
- - and J. A. CHAMBERLAIN, Jr. (1967):
Equations for volume and centre ofgravity in ammonoid shells. Ibid., vol.
41, no. 3, pp. 566-574.
REn'IENT, R. A. (1958): Factors in the distribution of fossil cephalopods. Stockholm Contr. Ceol., vol. 1, no. 6, pp. 98185, pis. 1-7.
-.- (1973): Factors in the distribution offossil cephalopods. Part 3. Experimentswith exact models of certain shell types.
Bull. Ceol. Inst., Univ. Uppsala, N. S., vol.
14, no. 2, pp. 7-41.
TANAKA, K. (1963): A study of the Cretaceous sedimentation in Hokkaido, Japan.
Ceol. Surv. Japan. Rep. no. 197, 119 pp.,3 pis.
THOMPSON, D'ARCY, W. (1917): On Crowthand Form. Cambridge Univ. Press, 1116
pp.
TRUE~'IA:-;, A. E. (1941) : The ammonite bodychamber, with special reference to thebuoyancy and mode of life of the living
ammonites. Quart. Jour. Ceol. Soc. London, vol. 96, pt. 4, pp. 339-383.
WESTERMANN, G. E. G. (1971): Form, structure and function of shell and siphuncle
in coiled Mesozoic ammonoids. Life Sci.
Contr. Royal Ontario Mus., no. 78, pp.
1-39.
WIEDMANN, J. (1965): Origin, limits andsystematic position of Scaphites. Palaeontology, vol. 8, pt. 3, pp. 397-453, pis.
53-60.
WRIGIIT, C. W. (1953): Notes on Cretaceousammonites .. 1. Scaphitidae. Ann. Mag.
Nat. Rist., ser. 12, vol. 6, p, p. 473-476.
YAIlE, H. (1910): Die Scaphiten aus der
Oberkreide von Hokkaido. Beitr. Paliiont.
Ceol. Oesterr.-Ungarns u. des Orients, vol.
23, pp. 159-174, pI. 15.
- - (1927): Cretaceous stratigraphy of theJapanese Islands. Sci. Rep. Tohoku Imp.
Univ., 2nd ser., Geol., vol. 11, no. 1, 74
pp., 12 pis.

Kaz1£shige TANABE

132
Hakkinzawa
Ichinosawa
Kamikinen betsu
Naibuchit3~tR- / iR.
J::~~JJIj

i*J

Obirashibe
OyubariTappu

mn

Explanation of Plate 11
Otoscaphites puerculus (JI~!BO) ....... ·. (All x 10)

Figs. 1-6. Median sections showing early stage.
Figs. 7-9. Cross sections cut parallel to base of body chamber.
Fig. 1.
Fig. 2.
Fig. 3.
Fig. 4.
Fig. 5.
Fig. 6.
Fig. 7.
Fig. 8.
Fig. 9.

GK. H. 5724, R 2110x.
GK. H. 5725, sample ditto.
GK. H. 5726, sample ditto.
GK. H. 5727, R 2110c.
GK. H. 5728, R 2110f.
GK. H. 5729, R 2110d.
GK. H. 5730, R 2110b'.
GK. H. 5731, R 2110e'.
GK. H. 5732, R 2110b'.

'J':ijL ~*17*:it ;(pTANABE:

Functional morphology of Otoscaphites

Plate 11

Trans. Proc. Palaeont. Soc. Japan, N. S., No. 99, pp. 133-U2, pI. 12, September, 20, 1975

649. IKEBEA, EINE NEUE GATTUNG DER PENNATENBACILLARIACEEN A US DEM NEOG EN J AP ANS·~SEIICHI KOMURAJapan Petroleum Exploration Co., Ltd. (JAPEX)

B*%Ir~=*g[:f]:l* § J1~¥r~94 Ikebea: 7dtJt!!.~IC7t;(P1" 7.> l:\)i1iJW,FiM . FlllJ~ . )t7]IJFiMiJ'

I? Fragilarioideae Hlc.:f <1" 7.>~~Jf~:rrr~a- 5 %Iff!!!.!:: c t Ic~JliII; L,.::to)FiM&~ft97t;(pc1:..\\!..at~lc"?~'-C=·':::il~t:7.>o *~~ltml*:l*O)7i-Ma-1iL, :tvilil*S!lP' l7IjO)f,i)ill r IT· 137IjO)~*!JIjO)fftEa-~l!i& c L, Clavicula PANTOCSEK ICJlI~"'C";6 7.> ~~ltll~b~M\I*l3E(r~)'ffi'1~fJ&~fJ!:iI!!illlW~±IC ~t.d:j'o'J' H fr!f 0

bei der hier genannten Gattung keinerlei
Spaltenstrukturen, wie Pinnularien- oder
Kanalraphe, an der Schalenoberfiachevorhanden sind. Aus diesen Grunden
mi:ichte ich die besondere Gattung proponieren.
Das Ziel diesei- Arbeit ist es, eine neue
Gattung der penna ten Bacillariaceen mit
fUnf neuen Arten taxonomisch zu beschreiben sowie ihre phylogenetische
Gehi:irigkeit und Ansiedlung kurz zu
disktieren.
Sowohl Holotypen als Paratypoide derneubeschriebenen Formen werden im
Technical Institute, Japan Petroleum
Exploration Co. (JAPEX) in Hamura in
Tokio, aufbewahrt.

Einleitung
Wahrend den Forschungen an einer
Anzahl von Diatomeenfossilien, die in den
Schichten der ni:irdlichsten japanischen
Inseln eingeschlossen sind, um damit fUr
die Erdi:ilforschung einen biostratigraphischen Standard festzustellen, habe ich
einige zu keiner bisher festgelegten
Gattung gehi:irigen Formen gefunden.
Diejenigen Fossilien, welche unter diesen
Namen hier angefUhrt werden sollen,
tragen, wie Opephom PETIT und ahnliche,
die zur Apikalachse symmetrische undzur Transapikalachse unsymmetrische
Schale ohne Quersepten und Zwischenbander, dagegen haben sie nicht die aus
Punktstreifen bestehende Ornamentur
sondern die mit eine Reihe von marginalen
Stachelreihen umfassene Struktur und ein
Paar von Endknoten.
Der weitverbreitete Individuenreichtum. dieses Organismus in den gesammelten
Proben gestattet es, ihre Beobachtungendurch Rasterelektron,enmikroskop (SEM)zu machen. Dabei wird bestatigt, daB,
* Received Nov. 15, 1974; read Oct. 19,

Fundort und Material
Das fUr diese Arbeit verwendete
Material stammt aus vier isoliertel1 Aufschliissen im Nord-Tenpoku Gebiet, wie
folgt:
Km-3519. Blaulich-grauer bis gelblichweiBer, aschenreicher, unreiner Kieselgur der Koitoi-Schichten. Breitengrad
45°23'36" N, Langengrad 141°41'22" E1974 at Nagoya.

133

Seiichi KOMURA

134

142°E

TENPOKUGEBIET~5·N----\---T~--+-----

et ai., 1965, Loc. cit.; HATA, 1961). Von
Herrn M. FUJITA angeboten.
Km-5037. Grauer, aschenreicher, sandiger
Tonstein der
Masuporo-Schichten.
Breite 45°15'39" N, Lange 141 °54'50" E,
am Siidufer des Uruyagawa-Flusses,
zirka 1,1 Km ostlich des Eisenbahnhofs
Magarifuchi vor der Stadt ebenda.
Mittelmiozan (vgi. MINATO et ai., 1965,
loc. cit.; T AKAI-IASHI & ISHIY AMA, 1968).
Fiir die optisch-mikroskopischen Untersuchungen des Materials wurden Streupraparate meistens mit der von KANA YA(1957, S. 42; 1959, S. 33) dargestellten
Verfahrenstechnik genommen. Sauerbehandlungen wurden aber davon ausgenommen, stattdessen Dekantierung
mehrere Male dazu hinzugefUgt. Ais
Einbettungsmittel fUr
Mikrofossilien
wurde Pleurax verwendet.

Systema tische BeschreibungenOrdnung Pennatae SCI-IUTT, 1896
Familie Fragilarioideae SCHUTT, 1896
o,

10,

Krn

20,

Abb. 1. Lage der Fundpunkte.

Subfamilie Fragilarieae SCHUTT, 1896
Tribus Fragilariinae SCHUTT, 1896
Gattung Ikebea, n. gen.

bei der Volksschule Wakkariai-Minami
in der Stadt Wakkanai. Oberstmiozan(vgi. MINATO et ai., 1965, S. 258; OSANAI, 1954).
Fo-l1. Ebenda. Breite 45°5'14" N, Lange
141 °19'17" E, etwa 3,8 Km siidostlichvon Toyotomi.
Oberstmiozan (vgi.
MINATO et ai., 1965, loc. cit.; NAGAO,
1960). Von Herrn N. FUJIOKA gesammelt.
Fj-2724. Grauer, aschenreicher, toniger
Sandstein der Enbetsu-Schichten. Breite'44°33'55"N, Lange 141°49'19"E, eine
Klippe am Siidufer des Flusses Furenbetsugawa. Oberstmiozan (vgi. MINATO

Gattungstypus: Ikebea amphistriata, n.
sp.
Originale Beschreibung:
ZeBen in
Giirtelansicht linear-keilformig, zuweilenlinear-rechteckig, in ventraler Giirtelbandansicht ziemlich linear und dorsale Seit
mit schwach konvexen Randern, durch
stark entwickelte Stachelkranze am
Schalenrand zu dicht geschlossenen
Bandern verbunden, in Transapikalschnitt
flach elliptisch, ohne Septen oder
Zwischenbander; Schalen im UmriB keiloder keulenformig mit beiden Endenabgerundet, zur geraden Apikalebene

649. Ikebea, Eine Neue Gattung der Pennaten Bacillariaceen
zurTransapispiegel-symmetrisch,kalebene heteropol und asymmetrisch,kurz vor dem Kopf- und FuBpol halsartig
eingeschniirt; Schalendeckel flach gewolbt, mit zwei polaren und ohne
zentralen Knoten ; Schalenoberflache
mehr oder weniger gestreift, nicht
punktiert, ohne keilartige Erhebungen;Pseudoraphe deutlich entwickelt, obgleich
sie nicht vollkommen von Pol bis Pol
lauft; keinerlei Raphe erscheinend, sogar
bei Raster-Mikroskop.
Ableitung: Der Gattungsname wird
nach Herrn Dr. Yutaka IKEBE, Vizeprasident unserer Gesellschaft, zum Andenken an seine Beitrage zur Erdolgeologie japans und seine Olexplorationstatigkeit genannt.
Bemerkungen :Die Gattung zeigt
starkeAhnlichkeit
mitClavicula
PANTOCSEK, aber unterscheidet sichdurch langgestreckte Streifung anstatteiniger Bandern von Punk ten. Zu den
Pennales stelle ich auch die Gattung
aufgrund der bilateralen Eigenschaft vonSchalen und Strukturanordnungen.

135

2. Streifen in Nahe des Endes
gegabelt . . . . . . . . . . .. I. bifurcata
II. Transapikalstreifen mindestens imTeil mit drei Strahlen laufend, groBte
Schalenbreite dem Kopfpol genahert
liegend .. . . . . . . . . . . . . . . .. I. clavata
Ikebea amphistriata, n. sp.
Taf. 12, Fig. 1-5; Abb. 2-5

Holotypus: Praparat Nr. jAPEX Km5037(3)= 10.4 X 84.6 (Fm 9928), MasuporoSchichten, Mittelmiozan.
Paratypoide: Praparat Nr. jAPEX Km5037(9)=12.9 X 79.4 (Fm 10241), Schichten
ebenda, Mittelmiozan.
Praparat Nr. jAPEX Km-5037(9)=6.5x
83.2 (Fm 10265), Schichten ebenda,
Mittelmiozan.
Originale Beschreibung:
Zellen in
Giirtelansicht linear-keulenformig, durch
Stachelkranze am Schalenrand zu dicht
geschlossnen
Bandern
verbunden ;Zwischenbander und Septa sowie Pseudosepta fehlend ; Schalen im UmriB

SchWssel zum Bestimmen
der Ikebea-Arten
I. Transapikalstreifen mit ein oder zwei
Strahlen laufend ; groBte Schalenbreite
der Mitte genahert liegend.
a. Streifen Pol bis Pol mit zwei Reihe
durchlaufend.
1. Schalen im UmriB robust, rundliche Randstacheln innerhalb desSchalenrandes stehend ......... .
...................... I. robusta
2. Schalen im UmriB zart, elliptische
Randstacheln am Schalenende
stehend ......... I. amphistriata
b. Streifen nicht in derartigen Weise
laufend.
1. Streifep in der Mitte reduziert..
I. coronata

{
2

3

4

5

Abb. 2-5. Ikebea amphistriata, n. sp.
2: nach Ho!otypus (Taf. 12, Fig. 4).
3: nach Paratypoid (Taf. 12, Fig. 1).
4: nach Paratypoid (Taf. 12, Fig. 5).
5: nach Taf. 12, Fig. 2.

Seiichi KOMURA

136

heteropol-keulenfOrmig bis etwa lanzettlich mit breit gerundeten Kopfpol undspitzer gerundetem FuBpol, unterhalb
der Enden leicht eingeschniirt, groBte
Breite in Nahe der Mitte, aber mehroder weniger oberhalb der Mitte genahert
liegend, 37-49 p. lang, 5-6 p. breit;
Schalenoberfiache schwach gewolbt;
Endknoten deutlich, verhaltnisma.Big
gro.B, oval oder elliptisch, in den beiden
Polenfeldern vorhanden, Eine Reihe vonzahlreichen Stacheln mit ovalen Querschnitt, am Schalenrande stehend, 7-10in
10 p. ; Transapikalstreifennicht
punktiert, schmal und kurz, innerhalb
der Stachelreihen und parallel zur
Schalenrandern von Pol bis an den Pol
langgestreckt durchlaufend; 14-16 in 10
p. ; Pseudoraphe deutlich, breit, lanzettlich,nach den Enden etwa verschmalert.
Ikebea robusta, n. sp.
Taf. 12, Fig. 6, 8; Abb. 6, 7

Holotypus: Praparat Nr. jAPEX Km5037(1)=5.0 X 88.6 (Fm 9794), MasuporoSchichten, Mittelmiozan.

Paratypoide: Praparat Nr. jAPEX Km5037(1)=5.3 X 87.5 (Fm 13403), MasuporoSchichten, Mittelmiozan.
01'iginaie Beschreibung: Schalen im
UmriB breit elliptisch-keulenformig mit
stark konvexen Seiten und kopfig
gerundeten Enden, groBte Breite wie bei
der Typ-Art der Gattung in der Mitte
genahert liegend, 23-38 p. lang, etwa 8 p.
breit; Schalenoberfiache stark gewolbt,
breit Mantel vorhanden; Endknoten
deutlich, relativ klein, oval oder elliptisch.
in den beiden Polenfeldern sich stellend;
Eine Reihe von der zahlreichen, groben,
warzenformigen Stacheln mit gerundetem
Querschnitt an der Basis, entfernt innerhalb des Seitenrandes einschlie.Bend, 59 in 10 p. ; Transapikalstreifen nicht
punktiert, schmal und kurz, keilformig
nach Schalenrandern abfallend, leicht
radial, innerhalb der Stachelreihen zwischen der Pseudoraphe und Stachelreihe
gelegten, in einer bogenartigen Reihe
von Pol bis an den Pol geordnet, 13-15
in 10 p.; Pseudoraphe deutlich, sehr breit.
lanzettlich, von der Mitte gegen die
Enden gleichmaBig enger werdend.
Bemerkungen: Die Art ist mit TypArt, die eine grundsatzlich linzenahnliche
Schalenform hat, zu vergleichen, mit
dessen sie aber zufolge Vorhandensein
von der viel konvexere, weit robustere
UmriBe und der mehr innen gelegten
Stachelreihen, nicht verbunden werdenkann.
Ikebea bzjurcata, n. sp.
Taf. 12, Fig. 11-13; Abb. 8, 9

6

7Abb. 6, 7. Ikebea robusta, n. sp.
6: nach Holotypus (Taf. 12, Fig. 6).
7: nach Paratypoid (Taf. 12, Fig. 8).

Holotypus: Praparat Nr. JAPE X Km5037(8)=5.9x 87.2 (Fm 10129), MasuporoSchichten, Mittelmiozan.
Paratypoide: Praparat Nr. JAPE X Km5037(12)=8.5x86.0 (Fm10454), Schichten
ebenda, Mittelmiozan.

649. Ikebea, Eine Neue Gattung der Pennaten Bacillariaceen

137

Taf. 12, Fig. 9, 10; Abb. 10, 11

-

-- -

~:

=E

8

9

Abb. 8, 9. Ikebea bifurcata, n. sp.
8: nach Ho!otypus (Taf. 12, Fig. 12).
9: nach Paratypoid (Taf. 12, Fig. 13).

Praparat Nr. JAPE X Km-5037(8)=14.9
x86.7 (Fm 10179), Schichten ebenda,
Mittelmiozan.
Originate Beschreibung: Schalen schmal
keulenfOrmig, gro.Bte Breite wie bei dervorigen Art in der Mitte genahert
liegend, 42-54 p. lang, 5-6 p. breit; Knoten
deutlich, kreisrund bis oval; Stacheln
flach bis langlich-elliptisch in Querschnitt.
5-8 in 10 p.; Transapikalstreifen nicht
punktiert, klein, elliptisch oder keilformig,
in der Mitte in Ordnung zu Stachelreihe
parallel und innen genahert verlaufend,
zwei Reihen von Streifen gegen den
Enden zu einander sich zu vereinigen
konvergierend, 12-17 in lOp.; PseudorapheverhaItnisma.Big breit, aber gegen den
Pol nieht nur weit enger werdend,sondern auch dort nieht reiehend.
Bemerkungen: Die Art ist besonders
im Umri.B 1. amphistriata ahnlich, aberunterscheidet sieh davon durch die bis
am Pol unreiehenden Pseudoraphe unddie gegabelten Transapikalstreifen.

Ikebea caranata, n. sp.

Holotypus: Praparat Nr. JAPE X Km5037(4)=14.5x79.4 (Fm 9944), MasuporoSchiehten, Mittelmiozan.
Paratypoide: Praparat Nr. jAPEX Km5037(10)=13.4X82.3 (Fm 10310), Schi·chten ebenda, Mittelmiozan.
Originale Beschreibung: Schalen linearkeiifi:irmig, mit gerundeten Kopfpol undstumpfen Fu.Bpol, von der gri:i.Bte Breite,
die ganz dieht in der Mitte liegt, gegendie beiden Enden wenig an Breite
abnehmend, in zu den Pol genaherten
Teil transapikal eingeschniirt, 30-36 p.
lang, 6 p. breit; Schalenoberflache starkgewi:ilbt; Endknoten deutlich, rundlichoval oder kreisrund, aus der Schalenoberflache sieh abhebend; Stacheln rundbis flach-elliptisch in Querschnitt an derBasis, innen entfernt von und parallel zu
Schalenrand laufend, 6-9 in 10 p. ; Transapikalstreifen nicht punktiert, klein,stabartig, innerhalb der Stachelreihe
einem Kranze ahnlich in Ordnung, im
Vergleich mit der vorliegende Art zu
der Mitte reduziert, 8-13 in 10 p.; zwei

1011Abb. 10, 11. Ikebea coronata, n. sp.
10: nach Ho!otypus (Taf. 12, Fig. lOa-b).
11 : nach Paratypoid (Taf. 12, Fig. 9a-b).

Seiichi J(OMU RA

138

breite hyaline Felder zwischen dem Pol
und der Streifenkranze bleibend; Pseudoraphe, die in der Mitte liegt, linsenartig,
ein drittel der Schalenlange einnehmend.
Bemerkungen: Die Art ist durch die
kranzartig
geordneten
Transapikal streifen charakterisiert und kann dadurch
von den iibrigen II, ebea -Arten getrennt
werden.

IIwbea ciavata, n. sp.
Tat. 12, Fig. 14- 16; Abb . 12- 14

Holotypus: Praparat Nr. jAPEX Km3519(10)= 11.9 x 82.7 (Fm 8417), Koitoi Schichten, Oberstmiozan.
Paratypoide: Praparat Nr. jAPEX Fj2724(8) = 11.4 X 95.0 (Fm 8069), EnbetsuSchichten, Oberstmiozan.
Praparat Nr. jAPEX Fo-ll(16)= 16.5 x
92.0 (Fm 12054), Koitoi-Schichten, Oberstmiozan.
Originale Beschreibung:
Zellen in
Giirtelansicht linear-keulformig, wie bei
Typus von der Gattung durch stark

12

13

14

Abb. 12- 14. Ikebea clava/a, n . sp.
12 : nach Ho!otypus (Tat. 12, Fig. 14) .
13: nach Paratypoid (Tat. 12, Fig . 15) .
14: nach Paratypoid (Tat. 12, Fig . 16).

entwichelte Stachelkranze am Schalenrand zu dicht geschlossenen Bandern
verbunden; Zwischenbander und Septen
fehlend; Schalen im UmriB schlankke ulenformig, groBte Breite stets oberhalb
der Mitte liegend, allmahlich gegen die
beiden Schalenpole verschmalert, in zu
den Pol genaherten Teile mit schwach
konkaven Randern, 41-54 f-l lang , 5- 7 f-lbreit.
Bemerlwngen :Die gegenwartige,
charakteristischkeulenformigeArt
unterscheidet sich leicht von iibrigen
durch drei Reihen von Streifenlinie unddie zu den Pol geschwundene Pseudoraphe. Sie tritt in oberem Teil an der
Schichtenfolge Neogens von Tenpoku Gebiet.
Diskussion

Es ist das Verdienst von F. HUSTEDT(1927- 64), die bis heute allereingehendste
GesamtdarstellungunddieklarsteSystematikbildung der rezenten undfossilen Diatomeen gegeben Zll haben.
Manche Autoren haben infolgedessen
wiederholt auf diese Arbeiten Bezug
genommen (KA TAY A & KOlZUM I, 1966;
KOIZUMl, 1968; SCHRADER, 1969). Damit
folge ich HUSTEDT als Grundlage desGesichtspllnktes zum Klassifikationssystem.
HUSTE DT (op. cit.), der a ls fundamentales Kriterium zur Gruppierung der Araphideae, einer raphenlosen GroBeinheit
der pennaten Diatomeen, Vorhandensein
der Septen beriicksichtigte und weitervon untergeordneter Bedeutung die transapikalen Rippen ansieht, zerlegte dieselbe
Einheit in Diatominae und Fragilariinae.
Der letztere Stamm, der sowohl das
Fehlen oder den Mangel an Septenbildungen als das Fehlen der Transapikalrippen zeigt, enthalt 18 Gattungen.
Von diesen gibt es flinf Gattungen , die649. Ikebea, Eine Neue Gattung der Pennaten Bacillariaceen
zur Transapikalachse asymmetrisch sind:Asterionella HASSALL, Synedrosphenia
PERAGALLO, Podocystis KUTZING, Sceptroneis EHRENBERG, und Opephora PETIT.
Die beiden ersten besitzen mit transapikalen Reihen zarter Punktstreifenoder gekammerter Rippen etwa ganze
Valvarfliichen (HUSTEDT, 1931-37, S. 240
u. 250), dadurch unterscheiden sie sichvon Ikebea. DaB die dritte der genannten
Gattungen nicht in verwandtschaftlichem
Zusammenhang steht, erscheint beim
ersten Blick auf die eigentiimliche
Gestalt und die areolierte Netzstruktur
sehr deutlich zu sein. Als Meeresfossil
bekannt scheinen nur die iibrigen zwei
Gattungen, Sceptroneis und Opephora, zu
sein (vgl. HUSTEDT, op. cit.). Die erstere
beschriinkt, nach WORNARDT (1972, S.53)
und LOHMAN (1948, S. 183), ihre stratigraphische Verbreitung auf Mittelmioziin
und die letztere nach WORNARDT (ioc.
cit.) auf Obermioziin bis Oberplioziin im
WestkiinstengebietderVereinigten
Staaten von Amerika, obwohl Vertreter
der beiden Gattungen an den atlantischen
Kiisten und im Mittelmeergebiet bzw.
durch ganz Europa, wenngleich durchweg
selten und sehr vereinzelt, anzufindensind, wie von HUSTEDT (1931-37, S. 130
u. 134) berichtet. jedenfalls kommt es
mir vor, daB eine groBe Menge vonVorkommen der Gattung Sceptroneis nur
im Mittelmioziin, in welchem derGattungstypus der Ikebea, d. h. I. amphistriata n. sp., im Tenpoku-Gebiet japans
auch sehr hiiufig auftritt, fortgesetzt ist.
Keine der oben zitierten Gattungentriigt aber Endknoten und Stachelreihen
wie bei der neuen Gattung Ikebea.
Die Gattung Clavicula PANTOCSEK,
1886, (fide KARSTEN, 1928, S. 267), derenF6rderung aus dem Mioziin japans sowie
aus der daran angrenzenden SachalinInsel der Sowjet-U nion (SHESHUKOVAPORETZKAJA, 1967, S.246) dargestellt ist,

139

zeigt, daB sie in Beziehung auf Symmetrieverhiiltnis und Besitzen der beiden
verdickten
Endknoten
mit
Ikebeaverwandtschaftlich nahe zusammenhiingt.
Sie hat nach SHESHUKOVA-PORETZKAJA(1967, loco cit.) weitere stratigraphische
Verbreitung im Obereoziin Kazakhstans
und der Ukraine bis zum N eogen
Sachalins.
Aus den oben diskutierten morphologischen Verhiiltnissen der neu proponierten Gattung zu bisher dargestellten
Formen mit ihren stratigraphischen
Vorkommenszustiinden geht hervor, daB
die fragliche Gattung Ikebea die stammesgeschichtlichen Zusammenhiinge zwischen
Sceptroneis und Clavicula aufzeigt, obgleich von KARSTEN (1928, loco cit.) die
systematische Stellung dieser sonderbarenkeulenfOrmigen Gattung fUr unsicher
angenommen wurde.
Die mittels des Raster-Mikroskopes
hergestellte Aufnahme (Taf. 12, Fig. 7)
zeigt eine tiberfeinskulptur auf der
Schalenunterfliiche von Ikebea amphistriata. Diese besteht aus einer Reihevon winzigen dendritischen Schmalspalten, die sich senkrecht zum Schalenrande bis halbwegs zur Sagittallinie
ausstrecken. Ihre systematische Bedeutung liiBt sich nur aus diesen wenigen
Aufnahmen nicht erkliiren. Fokussierung
bei Raster-Mikroskopie ist von sozeitraubender Beschwerlichkeit, daB die
Umstiinde ununtersucht geblieben sind.
Damit wird es in Zukunft zu untersuchen
sein, wie weit derartige Ultrastruktur
nur varia bel innerhalb der Individuengruppe oder Artkonstant oder auch gar
charakteristisch fUr die Gattung seinkann.
Es ist auch notwendig, die stratigraphische Bedeutung der vorliegenden Gattung zu beriicksichtigen. Die im Mittelmioziin auftretenden Arten sind verhiiltnismiiBig primitiv gestaltet, wie Ikebea

140

Seiichi KOMU RA

robusta n. sp. und I. bifurcata n. sp. Sie
tragen die isolierten. gerundeten bis
gefW.chten Randstacheln und die etwas
zerstreut geordneten, mindestens in einem
Teil der Schalenlange mit zwei Reihen
laufenden Transapikalstreifen, sowie das
im Vergleich zur Schalenbreite sehr
breite Mittelfeld. Die aus dem Ober·
stmiozan beschriebene Art mit komplizierteren Zeichnungen, d. h. Ikebea
clavata n. sp., erscheint dagegen entwickelter, wei I ihre Randstacheln langlichmiteinander verwaehsen, ihre Transapikalstreifen in drei Reihe aufwachsen,
und endlieh ihre Pseudoraphe stattdessen
zur Nahe der Pole reduziert ist. Mit
dem Zeitverlauf gibt es da eine Tendenz
zur Verwandlung in der Struktur der
Ikebea-Formen; demnaeh diirfen ihre
Evolutionslinie und Beniitzungswert zur
Neogenstratigraphie bei kiinftigen Untersuchungen erklart werden.
Es handelt sich vieUeicht aus derLiteratur von Diatomeen Japans undnaherer Reiche urn die Abbildungen, dienach SAW AMURA und YAMAGUCHI (1963,
Taf. 1, Fig. 5) als " Fragilaria sp." undnaoh SHESHUKOVA-PORETZKAJA (1967,
Taf. 39, Fig. 6a-b; Taf. 40. Fig. 5a-b)
als .; Goniothecium tenue Brun" verMfentlieht worden sind, da sie enge
Ahnlichkeit mit Ikebea-Arten zu haben
scheinen.
Die aus folgenden Formen bestehenden
Diatomeenfloren umfassen die beiden
Proben, aus den die hier besehriebenen
Arten stammen:1) aus dem AufsehluB von KoitoiSchichten (Km-3519),
Denticula kamtschatica ZABELINA
Thalassiosira antiqua (GRUNOW)
CLEVE
Thalassiosira decipiens (GRUNOW)JORGENSEN
Coscinodiscus stellaris ROPER
Thalassioneina nitzschioides GRUNOW

2) aus dem AufschluB von MasuporoSchiehten (Km-5037),
Denticula lauta BAILEY
Denticula nicobarica GRUNOW
Thalassionema nitzschioides GRUNOWMediaria splendida SHESHUKOVAPORETZKAJA
Kisseleviella carina SHESHUKOVAPORETZKAJAKeine limnisch-brachischen Diatomeen
wurden aus den vorliegenden beiden
Proben gewonnen. Das zeigt vermutlich.
daB aile Ikebea-Arten pelagisch-ozeanisehe
Habitat haben k6nnen.

Danksagung
Es ist mir eine angenehme Pflicht.
Herrn Dr. T. KANAYA. friiherem auBerordentliehen Professor an der Universitat
Tohoku, fiir die kritische Einsicht derOriginalstiicke zu dank en.
Fiir Ver6ffentlichungserlaubnis derArbeit bin ich Herrn Dr. Y. lKEBE.
Vizeprasident von JAPEX. zu groBem
Danke verpflichtet. Die Arbeit durch
Raster-Mikroskop wurde im Technology
Research Center der japan Oil Development Corporation durchgefiihrt.
!ehdanke Herrn Dr. Y. lSHIWADA, Vizedirektor, fUr die M6glichkeit, dies dort tun
zu k6nnen. sowie aueh Herrn K. SUZUKI
und Herrn H. KAMAKURA fiir ihre
hilfreichenAnleitungen bei der Bedienung.
I-Ierrn Dr. K. SAW AMURA und Dr. O.
FUKuTA am Geologischen Landesamt
japans in Tokio sowie I-Ierrn Dr. T.
ONITSUKA, Direktor der Oceania Petroleum Pty. Ltd., danke ieh ebenso fiir die
langjahrigen Anregungen.
lch danke endlich I-Ierrn M. FUJITA
und N. FUJIOKA, Geologen von jAPEX,
fUr die freundliche Dberlassung derProben.

649. Ikebea, Eine Ne'ue Gattung der Pennaten Bacillariaceen
Li tera turverzeichnis(Die Schrift der russischen Literatur wird
als Transkription gegeben.)
HATA, M. (1961): Explanatory text of thegeological map of japan, Hatsuura.
Ceol. Surv. Japan, 1-2, I-60, 1-'-8, Abb. 115, Tab. 1-10, 1 Karte, (Jap. mit eng!.
Zusammenf.).
HUSTEDT, F: (1927-64): Die Kieselalgen
Deutschlands,
Osterreichs undderSchweiz mit
Beriicksichtigung
deriibrigen Lander Europas sowie der an·
grenzenden Meeresgebiete: in Raben·horstes Kryptogamen-Flora von Deutschland, Osterreichs und der' Schweiz.
Leipzig, 7, (1), 1-920, Abb. 1-542, (2), 1736, Abb. 1-1105, (3), 1-556, Abb. 1-411.
KA"V,yA, T. (1957): Eocene diatom assemblages from the Kellog and "Sidney"
shales, Mt. DiabloA,rea, California. Sci.
Rept. Tohoku Univ., 2nd ser. (Ceol), 28,
27-124, Taf. 1-6, Abb. 1-4, Tab. 1-6, ;;Karten.
- - (1959):
Miocene" diatom-assemblages
from the Onnagawa formation and theirdistribution in the correlative formationsin Northeast Japan. Ibid., 30, 1-130, Taf.
1-11, Abb. 1-2, Tab. 1, 7 Karten.
Ki\:\,AYA, T. u. KOIZU;Vll, I. (1966):Interpretation of diatom thanatocoenoses
from the north Pacific applied to a studyof core V20-130 (Studies of a deep-sea
core V20-130, part 4). Ibid., 37, 89-130,
Abb. 1-6, Tab. 1-4, 1 Karte.
KARSTEN, G. (1928): Bacillariophyta (Diatomeae): in ENGLER u. PRANTL: Die
natiirlichen Pflanzenfamilien. 2, 105-303,
Abb. 93-424.
KOIZUl\U, I. (1968): Tertiary diatom flora of
Oga Peninsula, Akita Prefecture, Northeast japan. Sci. Rept. Tohoku Univ. 2ndser. (Ceol.) 40, 171-240, Taf.32-35, Abb.

Enbetsu
Furen betsuga wa
HamuraKoitoi
Magarifuchi

Uli:
J}IJ
@l.lIJJIJHI
:.M
N
p5

/itJ

IIll

ilI-~

141

1-15, Tab. 1-2, 2 Karten'.
LOHMA:\', K. E. (1948): Middle Miocene
diatoms from the Hammond Well: in
Cretaceous and Tertiary subsurface
geology. State Maryl. Board Nat. Res.,
151-187, Taf. 5-11, Tab. 16-19.
MINATO, M. et al. (1965): The geologic
development of the japanese islands.
Tokio, i-xxv, 1-442, Taf. 1-30, Abb. 126, Tab. 1-25.
NAGAO, S. (1960): Explanatory text of thegeological map of Japan, Toyotomi.
Ceol. Surv. Hokkaido. 1-42, Photo. 1-20,
Abb. 1-6, 1 Karte, (lap. mit eng!.
Zusammenf.).
OSANAI, H. (1954): Explanatory text ofthe geological map of Japan, Wakkanai.
Ibid., 1-3, Taf. 1-6, Abb. 1-7, Tab. 1-3,
1 Karte, (Jap. mit eng!. Zusammenf.).
SAWA~WRA, K. U. YAMAGUCHI, S. (1963):
Subdivision of Miocene by fossil diatom
in the Tsubetsu Area, east Hokkaido.
Bull. Ceol. Surv. Japan, 14, 777-782, Taf.
1, Abb. 1-2, (Jap. mit eng!. Zusammenf.).
SCHRADER, H. J. (1969): Die pennaten Diatomeen aus dem Obereozan von Oamaru,
Neuseeland. Beih. Nov. Hedw., 28, 1124, Taf. 1-39, Tab. 1-5.
SHESIIUKOVA-PORETZKAJA, V. S. (1967): Neogenovy morskie diatomovye vodorosli
Sakhalina i Kamchatki. Izd. LCU, 1327, Taf. 1-50, Abb. 1-9, Tab. 1-19,(Russ. mit eng!. Zusammenf.).
TAKAHASHI, K. u. ISIIIYA:VIA, S. (1968): Ex,planatory text of the geological map ofjapan, Numakawa. Ceol. Surv. Hokkaido,
1-46, Abb. 1-21, Tab. 1-3, 1 Karte, (Jap.
mit eng!. Zusammenf.).
WORNARDT, W. W. (1972): Stratigraphic
distribution of diatom genera in marine
sediments in western North America.
Paleogeogr. Paleocl. Paleoecol., 12,49-74,
Taf. 1-4, Abb. 1-9.

Masuporo
Tenpoku
Toyotomi
Uruyagawa
Wakkanai~~&"~i1lE1:t-}11

flt

P".I

142

Seiichi KOMURA
TafelerkUi.rungen(VergroBerung: Jeder schwarze Stock entspricht einheitlich 10 Mikron ohne andersartiges Bezeichnen.)Fig. 1. Ikebea amphistriata, n. gen., n. sp.
Parapypoid. Praparat Nr. JAPEX Km-5037(9)=6.5x83_2 (Fm 10265). Masuporo-Schichten.
Mittelmiozan.
Fig. 2. Ikebea amphistriata, n. gen., n. sp.
Giirtelansicht. Exemplar der zwei zelligen Kette. Praparat Nr. JAPEX Km-5037(3) =8.0x
86.5 (Fm 9915). Masuporo-Schichten. Mittelmiozan.
Fig. 3. Ikebea amphistriata, n. gen., n. sp.
Giirtelansicht. Praparat Nr. JAPEX Km-5037(7)=4.4x85.3 (Fm 10067). MasuporoSchichten. Mittelmiozan.
Fig. 4. Ikebea amphistriata, n. gen., n. sp.
Holotypus. Praparat Nr. JAPEX Km-5037(3)=10.4x84.6 (Fm 9928). Masuporo-Schichten.
Mittelmiozan.
Fig. 5. Ikebea amphistriata, n. gen., n. sp.
Paratypoid. Praparat Nr. JAPEX Km-5037(9) = 12.0 x 79.4 (Fm 10241). MasuporoSchichten. Mittelmiozan.
Fig. 6. Ikebea robusta, n. sp.
Holotypus. Praparat Nr. JAPEX Km-5037(1) =5.0 x 88.6 (Fm 9794). Masuporo-Schichten.
Mittelmiozan.
Fig. 7. Ikebea amphistriata, n. gen., n. sp.
Raster-elektronenmikroskopische Aufnahme. Exemplar der dendritischen Schmalspalten.
Fig. 8. Ikebea robusta, n. sp.
Paratypoid. Praparat Nr. JAPEX Km-5037(1) = 14. 7x 91.3 (Fm 13404). MasuporoSchichten. Mittelmiozan.
Fig. 9. Ikebea coronata, n. sp.
Paratypoid. Praparat Nr. JAPEX Km-5037(10)=13.4x82.3 (Fm 10311,10310). MasuporoSchichten. Mittelmiozan.
Fig. 10. Ikebea coronata, n. sp.
Holotypus. Praparat Nr. JAPEX Km-5037(4)=14.5x79.4 (Fm 9943, 9944). MasuporoSchichten. Mittelmiozan.
Fig. 11. Ikebea bi/urcata, n. sp.
Paratypoid. Praparat Nr. JAPEX Km-5037 (8) =14.9x 86.7 (Fm 10179). Masuporo-Schichten.
Mittelmiozan.
Fig. 12. Ikebea bi/urcata, n. sp.
Holotypus. Praparat Nr. JAPEX Km-5037(8)=5.9x87.2 (Fm 10129). Masuporo-Schichten.
Mittelmiozan.
Fig. 13. Ikebea bi/urcata, n. sp.
Paratypoid. Praparat Nr. JAPEX Km-5037(12) =8.5 x 86.0 (Fm 10454). MasuporoSchichten. Mittelmiozan.
Fig. 14." Ikebea clavata, n. sp.
Holotypus. Praparat Nr. JAPEX Km-3519(10)=11.9x82.7 (Fm 8417). Koitoi-Schichten.
Oberstmiozan.
Fig. 15. Ikebea clavata, n. sp.
Paratypoid. Praparat Nr. JAPEX Fo-11 (16) = 16.5 x 92.0 (Fm 12054). K~itoi-Schichten.
Oberstmi6zan.
Fig. 16. Ikebea clavata, n. sp.
Paratypoid. Praparat Nr. JAPEX Fj-2724(8)=11.4x95.0 (Fm 8069). Enbetsu-Schichten.
Oberstmiozan.

Ikebea, eine neue Gattung der Bacillariaceen

KOMURA:

1

2

4

3

Tafel 12

6

5

I

;

.:

.,

r

I

,

.
!

~

· :

I

:

•" •.

•, i•
~

.

l~ r

t

I 1

I,

;

.

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I
11

12

13

14

15

16

10a

I

\.'

10b

Trans. Proc. Palaeont. Soc. Japan, N. S., No. 99, pp. 143-155, pl. 13, September 20, 1975

650.

ON TWO FOSSIL MOLLUSCAN SPECIES FROM THE
EOCENE OF THE BONIN ISLANDS*Y ASUHIDE IWASAKI
Geological Institute, Faculty of Science, University of Tokyo,
Hongo, Tokyo 113, Japan'H~W-!Itl$JT~g[O) fl. fl::.E 2 fi~;:, "?\, '-C: 'Bi£W-~'!i~,;f:\j~f;:,7t:1pi" ~, !Itl:ifr~O)~~\'I}E?fjl¥t&lf1l1.*-iL"'C'~~E}jI(fiO)~~¥tiJ'I?g[I±li"~fl.{I::.EO)?~, iJ'''?-C ~ I -Jf1 f4 ~ / 711 ~O)=&fl.tL-cE.~~ ~~~• • "'C'~~~t~~.tLk~~~~/7l1~, :ifrkK.N~
1JQk.. k~I!kiO)~:I*t.c t· t ~iI'b-C, ry ~ ¥.? f4O)fiO)~1i.~EJf.J~l!g1l.:)~jji" ~ ,~iJ;J!,1, '0 "i t.:.O)~ll~iJ; 3 - p 'Y /{J::ffB~jffi*g[O) Spondylus spinosus (SO\\'ERBY, 1812) ~;:,~ L <M1J;J,i" ~~ t iJ' I?, lfijl*td\~1jE~im~~ LWt.: J: ? td~m~;:,~.'t Lt.: t ~'k..I?.tL~iJ~, f~J~, *~EJf.Jt;:,*6lf"? <~*,Htt.ch j~,@,~O)~ftllHYljc LM~[l:~~i"~o 1fij~1;:,j:~Hif~ ~.tLt.:7 "'~7'*f40)
1 fit,\!!,:h.tL~~fl.I;:'''?\''-CIt., !Itl¥r~t;:,~~O) Velates J: I) t tr L0.5Hf-i"~ j} / =z j}"1 M
1;:,j!j:I,'~ttlliJ~&~il'bI?.tL~o LiJ' Uj!~EO)IfijMJ: IJ*~-C'~ I), f'*tr-:I*flM'J: <t.c\',O)"'C'Jmfii'i
It.TlWi~ L -Cl, ,tJ:l, 'iJ;, .m:l*H!!tJHI5~[l.i" ~o fol.j.fjt t.o)~~I;:,;f:§~i" ~mcE~It.l'i¥Jlll L, ~iliiO)1.fmEr~o)7,.f*ff ~.tL -n, ~ 0) 'C, ~fi O)-ffiliJ'9;::h.tL -C;t.; ,), iJ,,,? j!iJ'V1'O)mt:It.r\li <t.c'?-C\"~o¥t IIr.f ~ ~Introduction
In july, 1969, the writer had an opportunity to visit and to make a shortgeological survey at Chichijima and,
Hahajima of the Bonin Islands (Ogasawara Islands) as a member of a scientific expedition organized jointly by the
Ministry of Education and the Agencyof Cultural Affairs, japan, at the timeof return of the Bonin and Volcano
Islands to the japanese territory.
Hahajima is located in the western
Pacific Ocean 1,000 km south of Tokyo.
This island has been well studied byjapanese paleontologists since YOSHIWARA (1901, 1902), YABE (1920) and HANZA WA (1925) reported the occurrence of
Eocene nummulite and alveolinid forami-* Received Feb. 5, 1975; read Jan. 17, 1973
at Sendai.

143

nifers. Further investigations were unfortunately interrupted by World War II.
The Bonin Islands were governed subsequently by the United States of America for over 20 years. During the postwar administration, Hahajima was an
uninhabited island. Pathway networks
and villages vanished into heavy bush in
the island. Several fossiliferous outcropsthat were previously reported, however,
have been very well preserved. Someshelly fossils are exposed thoroughly at
weathered surface of those outcrops andalso in nearby blocks.
Abundant fossil samples obtained fromthe Eocene foraminifer-bearing rocks
during the short excursion include apectiniform bivalve species which was
described by OYAMA (1943) as a peculiar
limid ' OW ASAKI and AOSHIMA, 1970).
This paper deals with the systematic,

144

Yasuhide IWASAKI

ecological and other significance of thisspecies and the description of an associated neritid gastropod.

Geological outline
Hahajima (Hillsborough Island) is themain island, having an area of 21 km 2 ,

r/

~, ))

ir··.
f.

.'
i

..". BOninIslands

HohoJlmo ' \500 kma

1 N ishiuro

Hahajima

2 Miyukihamo

.

t

'

'Xl

~:,o

D 'hl'
()

b

a

DO

~.

2 km

Text-fig. 1. Map showing the locationof Hahajima (a), and the location of Nishiura and Miyukihama (b).

of the Hahajima-retto (Hahajima groupof YOSHIWARA (1902)) that occupy thesouthern part of the Bonin Islands, andthat make up parts of ancient volcanoes
once raised above sea level in the midstof the Pacific Ocean. Lava flows andvarious kinds of pyroclastic flow deposits
predominate in the total stratigraphic
succession. Sedimentary rocks are lessin quantity and their distribution is restricted in the southern half of the island.
Most of these sediments are tuffaceousand intercalated in thick pyroclastic
layers. Fossil-bearing sandstone abutson lavas and tuff breccia, and coquina
limestone frequently thins out between
two layers of volcanic ejecta, hence thelateral extension of a single sedimentarylayer is usually traceable within a few
kilometers. Layers dip gently, less than
20° in usual, southwestward in the southern area, and northwestward in thenorthern area. Thus Hahajima seems
to be a part of western slope of a dissec ted volcano. ~arger foraminifers suchas Nummulites boninensis and Alveolina
javana boninensis are contained insandy sediments at Miyukihama (Cocoanut Beach of HANZAWA (1947)), Nankin- .
. hama (Nanking Beach), and in limestone
at Nishiura and several other localities
OW ASAKI and AOSHlMA, 1970).
HANZAWA (1925,1947) summarized thestratigraphic succession of Hahajima.
The coarse sandstone that exposes atthe border ridge between Miyukihama
and Nankinhama (Text-fig. 2) seems tocorrespond either to "~3 Nummulites
tuff" or to "1;:5 Nummulites-Discocyclina
tuff and agglomerate" of HANZA w A(1947). Also the tuffaceous coquina limestone at Nishiura seems to correspondto his "~7 Eorupertia-All'eolina tuff".
Accordingly, the coarse sandstone at
Miyukihama and Nankinhama seems to
be lower in horizon than the coquina

650.

Eocene of the Bonin Islands

145

....
" ~:.::

Miyukihoma

Nonkinhomo

'::.'
"

','

-6

o

200m

Text-fig. 2. Geological sketch map of Miyukihama and Nankinhama. 1. Andesite lava
flow. 2. Volcanic breccia. 3. Tuff breccia. 4. Coarse-grained sandstone. 5. Mediumgrained sandstone. 6. Nummulites-bearing part. X m • Collecting locality of Miyukihama.
X n • Collecting locality of Nankinhama.

limestone at Nishiura. In the present
field observation, however, no evidence
that the former is lower than the latteris recognizable because abundant volcanic materials distributed between the
two areas prevent the writer from astrict correlation of these two sedimentary layers. SAITO (1962) stated that no
significant stratigraphic difference wasestimated between those two layers on
the basis of planktonic foraminiferal correlation. Thus, molluscan shells collected from N ankinhama, Miyukihama
and Nishiura are nearly of the samegeological age. Geological age of thelayers is Rutetian (Middle Eocene) (HANZA WA, 1947; SAITO, 1962).

On the molluscan fossils
The sedimentary rocks of the Hahajima Eocene yield abundant foraminifers,
but molluscan fossils are quite uncommon. Descriptions and remarks on theforaminiferal fossils have been publishedby Y ABE (1921), HANZAW A (1947, 1950),
SAITO (1962) et at. Studies on molluscan
fossils from the Eocene of Hahajima havebeen done by YOSHIW ARA (1902), Y ABEand HATAI (1939) and OYAMA (1943).
YOSHIWARA (1902) first cited the occurrence of molluscan fossils. They are
Trochus (?) sp., " Nerita" sp. that resembles Velates schmidelianus, Nerita sp.,Natica sp., Vermetus sp., Voluta sp.,
Pecten sp., Ostrea spp., Cardium sp.,
Tapes sp. and Dentdlium sp. from thetuff of Nishiura probably corresponding
to the tuffaceous coquina limestone ofthis article. Specimens of YOSHIWARA'S
collection can not be examined because
they were lost. Y ABE and HATAI (1939)
described a large naticoid gastropod asa new genus and new species, Hahazimania hahazimensis, based on threemolds from the calcareous tuffite of
Nishiura, probably the same rocks thatYOSHIWARA'S specimens came from.

Yas~~hide

146

~

/
l:> .

I

. . . , . , ...
· ~ · Cl ·!..·A · tl · t:.

m ~llia

I w ASA f{[
L 10C01
is, therefore, formulated as R OlClO by
DALL'S system (DALL, 1913). This formula is the same as that of the spondylids. The linear arrangement of teeth
and sockets and sturdiness of teeth also
agree well with those of Spondyius . A
restored hinge area of a left valve chiefly
on the basis of the internal mold (specimen CM 8489) is sho\vn in Tex t-fig. 4.

200m

2

Te x t-fig. 3. Geo logica l sketch map of
N is hiura. 1. Alternation of a ndes ite lava
flow a nd t uff breccia. 2. TuffaceoLls limestone . 3. Tuffaceous sa nd sto ne. X . Collec t ing locality of N is hiura .
1 em

OY AMA (1943) described Lima (Me ololima ) ogasawamna, new subgenus andnew species, based on a few specimens
collected from Nishiura and Miyukihama.
In the origi nal description of the sub genus, it was noted that the left valve
is larger than the right, and that theligamental a reas of two valves are different in size. OYAMA stated f urther
that the inaeq uivalved configuration wasa diagnostic fe ature of the subgenus.
The pectiniform specimens new ly collected are identical with the t ypes ofLima (JvJeotolima) ogasawamna in theshell outline, and may be conspecifi c withYOSHI WARA'S " Pecten sp.". Of ten specimens examined during the present stud y,nine are disarticulated valves and they
are all damaged in the umbonal region.
The other specimen is an inner mold of
the dorsal part of a valve (PI. 13, fig. 4),
showing a nearl y straig ht hinge line withthree sockets and two stout teeth. A
socket at the middle portion appears to
be a resilium pit that - is triangular inshape. Arrangement of the hinge line

Text-fig. '1. Restored hinge pa r t ofleft va lve of Spondylus ( !\Ileotolill/a ) oga sawaranus ( O YAM A , 1943) .

T his spec ies is considered most appropriatel y as belonging to the gen us Spondyius instead of Lima . The unequa l sizeof valves and ligamental areas between
two valves is a quite common characteristic of the genus Spondyiu s, though it
is ver y peculiar for the genus Lim a. In
com parison with common Recen t spondylids, however, the present species diffe rs from them in its nearly equal convex ity of two valves and equally spaced
and stout radial ribe. The s urface ofribs is almost smooth except for three
specimens having rows of tubercles andsparse punctations mainly on the ribs
near the both marginal portions. This
species is easily distinguished from other
Cenozoic Spondyius species in the West
Pacific, and has an external appearance
closer to some pectinids than to spondylids. The only species morphologicallycomparab le with the present one is Spon-

650.

Eocene of the Bonin Islands

dylus spinosus (SOWER BY, 1812), which
was originally described from the Upper
Cretaceous Chalk of Great Britain. S.
spinosus is a common species in theUpper Cretaceous molluscan faunas ofWest Europe, characterized by a pectiniform shell outline with 25 to 50 distinct radial ribs and by long spines foundexclusively on the right (lower) valve.
According to WOODS (1901), the shellmorphology of the Cretaceous spondylid
is variable especially in surface ornaments that vary considerably amongindividuals from different stratigraphic
horizons. The present Eocene species
seems to be closely allied to such individuals of the Cretaceous species having
fewer radial ribs, though the shell convexity is generally weaker.
The specimens of this Eocene species
apparently have no spines, but tubercles
and punctations on some radial ribs may
be the vestiges of some peculiar ornaments. Some right valves of the Cretaceous S. spinosus which have lost theirspines in the course of fossilization display similar surface appearance to thesetuberculate and punctate Eocene specimens. Thus, the three Eocene specimens
are inferred to be right valves that most
likely had long spines similar to thoseof the Cretaceous species in the living
state. The true length and shape ofspines which have existed on the rightvalve of the Eocene spondylids are unknown, but it is at least obvious thatspines are fewer in number than in the
Cretaceous species, and that they are
distributed mainly on the ribs near theanterior and posterior peripheries.
The hinge 0.£ all specimens except for
one inner mold are broken away. Such
broken shells are also common in the
Cretaceous species (WOODS, 1901; CARTER, 1972; Collections of U niv. Mus.,
Univ. Tokyo). This is partly due to147some mechanical damage in the courseof disarticulation of the strong spondylid
hinge, and partly because (CARTER, 1972)
the umbonal area is chemically lost due
to leaching of the aragonitic inner layers.
The shells of the Eocene spondylid aremade up of at least two structurally different layers that are recognized in the
cross section of shells. The crystal formof both layers is calcitic, outer foliatedand "inner" grained layers. The outer
foliated layer is rather well preservedwith original growth increments, andlong tabulae of original foliated structure
can be observed on the fractured surface.
On the other hand, grained structure issporadically found beneath the outer foliated layers. This is thin in comparison
with the outer layer and seems to becomposed of recrystallized calcite that
replaced a part of aragonite layer without any ghost of original shell structure.
The shells of common Recent spondylids
are made up of three structural layers;
the foliated, crossed-lamellar and innercrossed-lamellar structures of T Po. YLOR,KENNEDY and HALL (1969), or foliated,crossed-lamellar and complex structuresof KOBAY ASH! (1971), and consist of calcite and aragonite. The absence ofaragonite layer in the Eocene shell seems
to be due to alteration or leaching subsequent to burial. The shell layers originally occupied by aragonite and not recrystallized are almost thoroughly filledwith sedimentary particles instead of
remaining a vacant space. It is still
problematic whether the shell of thisspecies is essentially double layered or
triple layered. The shell structure of
the Eocene species does not coincide withthat of the Recent limids, which consistsof foliated, crossed-lamellar and complex
crossed-lamellar structures (TAYLOR,KENNEDY and HALL, 1969).
The Cretaceous S. spinosus is regarded

Yas~~hid e IWASAKI148

sib ly accumu lated in a way formin g abottom not unlike a chalky environment.
The complete shell form of the Eocene
SpondyLu s (iVleotoLima) ogasawamnus isthus restored on the basis of above discussed characteristics and of a simulation
to Spondyius spinosus described and discussed by SOWERBY (1812), WOODS (1901)
and CArnER (1972) (Text-fig. 6a, b).

ab

0 .5 mm

Text-fig. 5. Ace tate replica of shellof Spondylus (Meotolima) ogasawaranus( OYAMA, 1943) . A part of cross section
along umbo (left ) t o ve ntral margin( ri g ht ). a. Well preserved outer foliatedlayer. b. Grained calci te, a par t of middle
layer? c. Cavity filled w ith ca lcite, origin a ll y pene t rated by boring animals.

as a dweller on soft bottom of chalky
sediment without cementing to hard objects in the adult stage ( CARTER, 1972).
The spiny right valve is considered tolay downward, and the long spines prevent the shell, especially its commissureplane, from sinking into the soup y substrate ( C A RTER, 1972). This is an ecological adaptation different from othercontemporaneous spond ylids. The modeof life of the Eocene species is presumably similar to that of S. spinosus, because of the close resemblance in shellmorphology. The environment in which
the Eocene species acquired such living
attitude is not a chalky basin but thesubmarine slope of a volcano, where debris of shell materials and fine tuff pos-

Text-fig . 6. Restored she ll morphology
of Spondylus (Meoto lima) ogasawaranu s( OYAMA, 1943) .
Oblique-posterior v ie w(a), anterior v iew (b).
Oy AMA (1943)

originally noted that theleft valve is larger than right valve probably on the basis of an articulated specimen ; in the present article the large
valve of OYAMA'S specimen is regarded
as right. This interpretation coincides
with S. spinosus as well as the common
tendency in other Spondy Lus species.

650 . Eo cene of the Bonin I slands
The type specimens (syntypes) of " Lima
ogasawarana" were lost according to
Oy AMA, MIZUNO and SAKAMOTO (1960).
T he second species to be describ ed inthis article is a large neritid gastropod.
The single specimen at hand is not wellpreserved, shell material of the aperturalside is dissolved away. The shell ischaracterized by its ovoid form andstrong expansion of the body whorl. The
outer lip of the aperture turns gentl youtward, and the inner lip which is lostin the present specimen seems to extend
widely on the penultimate whorl forminga labial area, judging from remnants ofthe marg inal flange surrounding the base.
The feature of the labial area as restored
in Tex t-fig. 7 somewhat resembles thoseof Septaria and Dostia. No umbilicus isobservable. The present specimen has athin test, less than 1 mm in thickness, so
the appearance of shell is rather fragil e
if compared with common neritid species.
The Recent neritid shell is composed ofthree structural layers, namely outer
prismatic layer of calcite, middle crossedlamellar layer and inner complex crossedlamellar layer of aragonite. According to
BOGGILD (1930), species of Neri tina havea very thin outer calcite layer in comparison with thick layer of species belonging to Neri ta (s. I.). This thin outerlayer is common to species of Th eodo xu s,
Clithon, Septaria and Dostia. The testof the present specimen is all calcitic
and seems to be made up of only a single
layer. Although t ypical prismatic structure cannot be observed in this calcitic
test owing to recrystallization, the thinshell seems to correspond to the outerlayer , especially that of the Neritina
group. Inner two layers of the shellconsisting of aragonite, are most likel yleached as in the same case with Spon dylus ogasawaranus. Thickening of outer
lip and feature of inner lip as well as

149

lcm

Text-fig. 7. Restore d aperturalside of "Neritina" sp.

dentition characterizing the neritid shell
aperture cannot be observed owing to thereplacement by sedimentary particles.
This specimen is in all probability notconspecific with YOSHlWARA'S " Nerita"
sp. which is allied to Velates schmidelianus (CHEMNITZ) because of the differencein the mode of coiling of spires. Hahazimania hahazimensis Y ABE and HATAI
is a naticoid and is obviously different
in shell morphology from the present
species. The characteristics of this species are considered to be mostl y allied
to those of genus Neriti na (s. I.) despite
the shell size being much larger thancommon Neri tina species.
Comparison with the molluscan
species and assemblages ofrela ted area and stages

Fossil bearing Eocene formations are
known from the Japanese Islands andseveral islands in the West Pacific surrounding the Bonin Islands. The Eocene
molluscan fossils in the main islands ofJapan are summari zed by MIZUNO (1964a,b). The Takashiman and Okinoshimanstage faunas are the Eocene representatives of Kyushu, and they are predom-150

Yasuhide IWASAKI

ina ted by shallow embayment or inland
sea inhabitants containing brackish water
species. The other is the Lower Ishi·
karian fauna of Hokkaido, which is predominated also by shallow embayment
species and by non-marine species. Remarkable differences in species association are recognizable between above
cited Eocene faunas and the molluscan
fossils in Hahajima, and seem to reflect
differences in the living environment.
Another molluscan assemblage is described from the Eocene Miyara formation of Ishigaki Island (MACNEIL, 1964).
It is noticeable that among 17 species
described, one gastropod species, Ampuilinopsis ct. A. hahazimensis (=Hahazimania hahazimensis), is closely related
to the species of the Hahajilpa Eocene
according to MACNEIL (1964). Other
species that were reported from the
Miyara formation are not found in Hahajima. MACNEIL noted the faunal resemblance to the Eocene formations in Kyushu of the japanese Islands rather thanto elsewhere in the West Pacific. Paleoecologically, both the Ishigaki Island andKyushu are located at the eastern marginal zone of the Asiatic continent, hence
the living environment of the Miyara
fauna may be more intimately related tothose of the Takashiman and Okinoshiman stage faunas than to the oceanicisland fauna of Hahajima.
Several islands in the West and theSouth Pacific are composed in part of the
Eocene clastic sediments such as the
Alutom formation of Guam (TRACEY etai., 1964), the Hagman and Densinyama
formations, the Matansa limestone of
Saipan (CLOUD, SCHMIDT and BURKE,
1956), Wainimala Series and limestone in
Viti Levu of Fiji (LADD, 1966). Althoughabundant occurrences of larger foraminifers have been emphasized, well preserved molluscan fossils have scarcely

been reported from these formations.
Another Eocene molluscan fauna is reported from Tonga in the South Pacific(LADD, 1970). It occurs from tuffaceous
limestone and is represented by small
sized gastropods. No comparable species
with the two Eocene species of Hahajima was reported. The geographicaldistribution of Spondyills ogasawaranus
and " Neritina" sp. may be restricted to
Hahajima and adjacent small areas.
There are few evidences to combine
phylogenetically the Cretaceous SPOIldyius spinosus with the Eocene S. ogasawaranus. The former species seems
to be endemic to the European region,and its extension in distribution to North
America, or to East Asia has not beenreported. There are, therefore, no areas
where the distribution of both species
overlaps. Stratigraphically younger S.
ogasawaranus may not be a direct descendant of the European species, but
be derived from a stock of sessile spondylids lived in the Pacific region of the
Mesozoic, which is probably different
from the S. spinoslls stock, in a manner
similar to S. spinosus. S. ogasawaranus
may be. therefore, regarded as a good
example of parallelism in adaptation.
A few Cretaceous spondylid species
have been known in japan. Spondyius
japonicus from the Upper Cretaceous
formation in Nagano, described by AMANa and MARUI (1958) is a large species
with numerous fine radial ribs, and its
morphology is more similar to some
Recent sessile forms. S. decoratus NAGAO
is another Cretaceous species (HAY AMI,
1956), and its shell morphology also
resembles common Recent spondylids
rather than S. ogasawaranus. Both Cretaceous species in japan have no apparent morphological and inferred ecologicalrelations to the Eocene species.

650. Eocene of the Bonin Islands
Description of species

Superfamily Pectinacea
RAFINESQUE, 1815

151

Upper Cretaceous Spondylus spinosus(SOWER BY, 1812) in Europe, although theapplication of this subgenus is tentatively
restricted to the Eocene Pacific species.

Family Spondylidae GRAY, 1826
Genus Spondylus LINNE, 1758
Subgenus Meotolima OYAMA, 1943

Spondylus (Meotolima) ogasawaranus(Oy AMA, 1943)
Plate 13, figs. 1-7

Type species: Lima (Meotolima) ogasawarana OYAMA. 1943, (original designation).
Subgeneric diagnosis: Moderate sized
spondylid. Pectiniform in outline with
distinct radial ribs on shell surface.
Nearly aequilateral, slightly inaequivalve.
Right valve larger than left valve. Right
valve has several spines formed mainly
on ribs near anterior and posterior peripheries. Left valve has no spines. Twovalves equal in convexity.
Remarks: Species of this subgenus
seem to be kept on soft bottom sedimentsby spines of right (lower) valve in life
position in the adult stage instead of
cementation by right valve to hard substrate. Meotolima was proposed originally by OYAMA (1943) as a subgenus of
Lima without description of the hinge
teeth. The inaequivalve shells were emphasized as a diagnostic character ofthis subgenus. Cox et ai. in MOORE(1969) adopted OYAMA'S proposal, andtreated Meotolima as a subgenus of genus
Lima. Meotolima is here assigned to asubgenus of the genus Spondylus because
Lima ogasawarana of OYAMA has an
isodont hinge as illustrated in Text-fig. 4.
The diagnostic characters of the subgenus are redefined. The morphologicalcharacteristics of Meotolima have intimate relations to peculiar mode of life
among spondylids. The shell morphology
and inferred ecology of the Meotolima
species are very similar to those of the

Lima (Meotolima) ogasawarana OYAMA, 1943,
p. 36, 37, pI. 2, figs. 9, 10; pI. 14, fig. 7.
Lima (Meotolima) ogasawarana OYAMA: OYAMA, MIZUNO and SAKA:VIOTO, 1960, p. 124,
pI. 33, fig. 1.

Supplementary description: Shell moderate to small in size for the genus, suborbicular in outline, nearly aequilateral,
inaequivalve. Dorsal end auriculate, andventral margin broadly rounded. Umboof right valve (lower valve) more prominent than that of left valve. Left umbo
scarcely projects from the hinge line.
Convexity of two valves nearly equal.
Auricle small, neither byssal gape nor
byssal notch found in adult shell. Weakauricular sulci observed anteriorly andposteriorly both in right and left valves.
Shell surface ornamented with equally
elevated and spaced distinct radial ribs.
Ribs neither bipartite nor grooved. Number of .ibs between 21 and 25, 23 and 24
of modal value. Rib profile triangularor rounded quadrate shaped. Interspace
narrow. Growth lines visible only near
ventral margin of adult shell. No ornamentation found on ribs except spines.
Spines grow in most individuals on theribs just adjacent to the anterior andposterior auricular sulci of right valve.
Spines seem to be 2 or 3 in number oneach rib. Actual length and feature ofspines unknown. Other ribs rarely furnished by spines. No spines found onleft valve. Hinge plate not so long, about

Yasuhide IWASAKI

152

a half of shell length. Hinge teeth stout
and 2 in number (Text-fig. 4) in eachvalve. Resilium large. Inner surface
weakly grooved at middle and ventral
part where thin inner shell layer remains unsolved (recrystallized by calcite).
Grooves correspond to the rib elevationof outer surface. Adductor scar indis-

tinct. Inner ventral margin crenulated
strongly. Two valves seem to close
tightly at the ventral margin. Test
moderately thick and may consist atleast of two different structural layers,
the outer calcite foliated layer, but inner
layer either leached or recrystallized.

A1easurements:
Specimen' Length
CM 8480
CM 8481
CM 8482
CM 8483
CM 8484
CM 8485
CM 8486
CM 8487
CM 8488*Type
specimen

I Height

Depth

Number of Apicalradial ribs angle

Valve

Localityleft

Nankinhama(Nanking Beach)

"
right

"
"

"

"

left

"
"

36.5
(mm)
40.4
40.0
34. 7
42.5
40.0
36.3

37.4
(mm)
38.4+
40.5
36.5
47.0
42.0
38.1

9.6
(mm)
9.4
9.4
10.3
12.6
12.0
10.4

23

90°

24
24
24
21
24
24

97°
85°
86°
86°
93°
92°

28.4
20.0+
33 ca

28.6+
25.2
36.2

6.8?
6.0
15.3
(R+L?)

22
23+
23

89°
84°
?

"
right
left
right
left+
right

Miyukihama(Cocoanut Beach)
Nishiura""?

* after OYAMA (1943)

Comparison: The species resembles
Spondylus spinosus (SOWERBY, 1812) of
the Upper Cretaceous (Turonian to Maastrichtian) in shell morphology, but isdistinguishable by the smaller number ofradial ribs. Surface sculpture and shellconvexity are less variable comparedwith morphological variation of S. spinosus described by WOODS (1901). Most of
adult shells do not exceed 50 mm in shelllength, though some individuals of S.
spinosus attain 70 mm.
No species of Spondylus other thansessile forms have been reported fromthe Paleogene formations in the JapaneseIslands and the West Pacific.
Remarks: This species occurs fromthe coarse tuffaceous sandstone and tuff-

aceous limestone of Hahajima associatedwith Nummulites boninensis HANZA w A,
1947 and Alveolina javana boninellsis
HANZAWA, 1950. It is not common. The
valves are disarticulated in most individuals, and are broken at the hinge orin the umbonal area. No articulated
specimens were examined. All spines on
the right valves are broken at their base,and their existence is only recognizableby scars marked on shell surface. Such
broken valves show a pectinid appearance like Aequipecten or Cryptopecten,
and are rather dissimilar to common
Recent spondylids which are cemented
by right valve to a hard substrate. This
species seems to be endemic to theislands.

650.

Eocene of the Bonin Islands

Occurrence and specimens: Nummulttes-bearing coarse tuffaceous sandstoneof Miyukihama (Cocoanut Beach), CM
8486, and Nankinhama (Nanking Beach),
CM 8480-CM 8485, Okimura; Alveolinabearing tuffaceous limestone of Nishiura,
CM 8487-CM 8489, Okimura; both inHahajima (Hillsborough Island), Ogasawara-mura, Tokyo-to.
These specimens are deposited in the
Department of Geology and Palaeontology, University Museum, Universityof Tokyo.

Superfamily Neritacea RAFINESQUE, 1815
Family Neritidae RAFINESQUE, 1815
Genus Neritina LAMARCK, 1816
" Neritina " sp.
Plate 13, fig. 8; Text·fig. 7

Description: Shell very large for the
genus. Ovoid in outline, but somewhat
flattened at apertural surface. Test thinfor common neritid species and seems tobe fragile. Spire low, slightly protruding,so the right side (apertural side) almost
flat. Body whorl expanded attaining
about a half of shell diameter. Fivespires observable. Aperture large. Its
width nearly equal to height. Outer lip
bent outward. Inner lip extends abaxially to the opposite end of aperture forming a labial area, and its margin seems
to protrude making thin flange like thatof Septaria species. No umbilicus. Dentition of aperture unknown, and apertural
margin most likely smooth. Shell surface smooth. Surface pigmentation andoperculum unknown.
Measurements: Maximum diameter,
50.0; shell height, 38.5; shell width, 33.4
(in mm).

153

Remarks: Only one specimen is athand. The shell outline shows apparent
neritid characteristics.
It resembles
somewhat pre-Cenozoic species of " Naticopsis" in overall shell outline, but themorphology of aperture seems to bedifferent. Generic assignment of thespecies is based mostly on aperturalconfiguration inclusive of morphology ofouter and inner lips, that are restoredfrom fragmental data (Text-fig. 7). Verythin test does not represent that of living
state as stated in the chapter of discussion. Original thickness of test at its
aperture is estimated to be more than
3 mm. The specimen is so large in sizefor genus Neritina that identification to
the assigned genus is somewhat hesitant.
This species differs from Velates speciesof the Eocene in the shell outline especially in the mode of coiling and sturdiness of test.
Occurrence and specimen: Alveolinabearing tuffaceous limestone of Nishiura,
Okimura, Hahajima (Hillsborough Island),Ogasawara-mura, Tokyo-to, CM 8490,
stored in the Department of Geology andPalaeontology, University Museum, University of Tokyo.
Acknowledgments: The writer is muchindebted to Prof. Emeritus Fuyuji T AKAI,
Profs. Tetsuro HAN AI, Kiyotaka CHINZEIof the Geological Institute, University ofTokyo, and to Prof. Itaru HAYAMI of the
University Museum, University of Tokyo
for kind advice in the course of thepresent study. Thanks are due to Dr.
Mutsuharu AOSHIMA for co-operation in
the field work at Hahajima, to Mr. Yoshimasa TSUKAHARA for preparation offossil specimens. The writer is also
thankful to the Ministry of Education,
Japan for making an opportunity to visit
the Bonin Islands.

154

Yasuhide IWASAKIHAYA~-ll, 1. (1965):

References cited
AMA:-\O, M. and MARCI, N. (1958): On the
new species of Spondylus from the Cretaceous formation in Nagano Prefecture.
Kumamoto Jour. Sci., Ser. B, Sec. 1, Vol.
3, No.1, p. 27-30, pI. 2.
BOGGILD, O. B. (1930): The shell structureof the mollusks.
Det. Kg!. Danske
Vidensk. Selsk. Skrifter, Naturvidensk.
od Mathem. Ald., 9 Riikke, II, 2, p. 233325, pis. 1-15.
CARTER, R. M. (1972): Adaptations of British Chalk Bivalvia. Jour. Paleontoi., Vol.
46, No.3, p. 325-340, pis. 1-3.
CLOUD, P. E., Jr., Scm'lIDT, R. G. and BURKE,
H. W. (1956): Geology of Saipan, Mariana Islands. Part 1. General geology.
U. S. Geol. Surv., Prof. Paper, 280-A, 126
p., 25 pis., 3 sheets.
DALL, W. H. (1913): Class Pelecypoda. in
EASTMAN, C. R. edit. Text-book of paleontology, Vol. I, p. 422-513, Macmillan,
London.
HAXZAWA, S. (1925): Notes on some foraminiferous rocks from Okinawa-jima andthe Ogasawara Island. (in Japanese),
Jour. Geol. Soc. Tokyo, Vol. 31, No. 386,
p. 10-24.
- - (1947): Eocene Foraminifera fromHaha-jima (Hillsborough Island). Jour.
Paleontol., Vol. 21, No.3, p. 254-259, pis.
39, 40.
_ . (1950): Eocene Foraminifera fromHaha-jima (Hillsborough Island) (2).
Short Papers, IGPS, No.1, p. 1-4, pI. 1.

Lower Cretaceous marine
pelecypods of Japan, Part 1. IvIem. Fac.
Sci., Kyushu Univ., Ser. D, Vol. 15, No.
2, p. 221-349, pis. 27-52.
IWASAKI, Y. and A05HlMA, M. (1970): Report on geology of the Bonin Islands.
in The nature of the Bonin and Volcano
Islands., p. 205-220, Ministry of Education
and Agency for Cultural Affairs, Japan.
KOBAYASHI, 1. (1971): Internal shell structure of recent bivalvian molluscs. Sci.
Repts., Niigata Univ., Ser. E, No.2, p.
27-50, pis. 1-10.
LADD, H. S. (1966): Chitons and gastropods(Haliotidae through Adeorbidae) fromthe Western Pacific islands. U. S. Geol.
Surv., Prof. Paper, 531, 98 p., 16 pis.
- - (1970): Eocene mollusks from Eua,
Tonga. Ibid., 640-C, 12 p., 5 pis.
MACNEIL, F.S. (1964): Eocene megafossils
from Ishigaki-shima, Ryilkyu-retto. Ibid.,339-B, 14 p., 3 pis.
MIZUNO, A. (1964a): Paleogene and early
Neogene molluscan faunae in West Japan.
Geol. Surv. Japan, Rept. No. 204, 72 p.
- - (1964b): Summary of the Paleogene
molluscan faunas in North Japan. Ibid.,
No. 207, 28 p.
MOORE, R. C., edit. (1969): Treatise on invertebrate paleontology, Pt. N, Mollusca
6, Bivalvia Vol. 1, 489+38 p., Geol. Soc.
America and Univ. Kansas.
Oy A~1A, K. (1943): Familia Limidae. Conchologia asiatica, Vol. 1, pars 1, p. 1-74,
pis. 1-14, Tokyo.
- - , MIZCXO, A. and SAKA~IOTO, T. (1960):

Explanation of Plate 13(All figures in natural size unless otherwise stated)
Figs. 1-7. Spondylus (Meotolima) ogasawaranus (OYAYIA, 1943)
la, posterior view of Ib,right valve, CM 8483; 2, right valve, CM 8482; 3, interior viewof right valve, CM 8488, x 2; 4, inner mold, dorsal part of right valve, CM 8489; 5, left
valve, CM 8480; 6a, anterior view of 6b, left valve, CM 8485; 7, interior view of left
valve, CM 8487. 1, 2, 5, 6 from Nankinhama (Nanking Beach); 3, 4, 7 from Nishiura.
Fig. 8. "Neritina" sp.
,I.
8a, posterior view, 8b, apical view, CM 8490, from Nishiura.

IWASAKI:

Eocene molluscs of Ogasawara

Plate 13

4

6b

7

ab

650.

Illustrated handbook of Japanese Paleogene molluscs. 244 p., 71 pis., Ceol. Surv.
japan.
SAITO, T. (1962): Eocene planktonic Foraminifera from Hahajima (HillsboroughIsland).
Trans. Proc. Palaeont. Soc.
japan, N. S., No. 45, p. 209-225, pis. 3234.
SOWERBY, J. (1812): Mineral conchology ofGreat Britain. Vol. 1, 234+10 p., 102
tabs. (pis.), London.
TAYLOR, J.D., KE:-iNEDY, W.J. and HALL, A.
(1969): The shell structure and mineralogy of the Bivalvia. Introduction,
Nuculacea-Trigonacea.
Bull.
BritishMus., Nat. Rist., Zool., Supp. 3, 125 p.,
29 pis.
TRACEY, J. 1., Jr., SCHLANGER, S.O., STARK,
J. T., DOAN, D. B. and MAY, H. G. (1964) :General geology of Guam. U. S. CeoI.
Surv., Prof. Paper, 403-A, 104 p., 3 pis.
WOODS, H. (1901): A monograph of theCretaceous Lamellibranchia of England.

Chichijima
Hahajima
Ishigaki
Ishikari
MiyakoMiyaraMiyukihama

I.

5t
ffl:

155

Eocene of the Bonin Islands

9b
9b

::{5
::{5

:m:

'8
'8

J5
&

~

fl11J$~

Vol. 1, Pt. 3, p. 113-144, pis. 20-26,
Palaeontogr. Soc. London.
YABE, H. (1920): Tertiary higher foraminiferal rocks from Japan (2). (in Japanese), jour. Ceol. Soc. Tokyo, Vol. 27,
No. 322, p. 293-300.
- - (1921): Notes on some Eocene Foraminifera. Sci. Rept., Tohoku Imp. Univ.,
2nd Ser., Vol. 5, No.4, p. 97-108, pis.
16-20.
- - and HATAI, K. M. (1939): On an interesting Gastropoda from Haha-zima, Ogasawara Islands, Japan.
japan. jour.
Ceoi. Ceogr., Vol. 16, Nos. 3,4, p. 209212, pI. 12.
YOSHIWARA, S. (1901): The Ogasawara
group is not situated on the Fuji Chain.
(in Japanese), jour. Ceol. Soc. Tokyo,
Vol. 8, No. 96, p. 380-389.
- - (1902): Geological age of the Ogasawara Group (Bonin Islands). CeoI.
Mag., New Ser., Decade 4, Vol. 9, No.
7, p. 296-303.

Nankinhama
Nishiura
Ogasawara
OkimuraOkinoshima
Takashima

ilL$: ~
ft§iI'Ii

'j' ~ !*

rIp :tt¥91 / 9b
jl1ij

9b

Trans. Proc. Palaeont. Soc. Japan, N. S., No. 99, pp. 156-171, pis. 14, 15, September 20, 1975

651. MISSISSIPPIAN CONODONTS FROM THE OMI LIMESTONE,NIIG AT A PREFECTURE, CENTRAL J AP AN
KOZO WATANABE
Noda Senior Highschool, Noda-City, Chiba 278

wlfaEIiRJ6-O)WlfaJlliS~ 'f:'7tmi" Q Endothyra
Q Gnathodus bilineatus-G. commutatus-G.
{tEIlf~~~~t.:c0):2 / 1-':/ r {tEllflt,
j:PJ'&EW(J6-15~/
r :* W#iHiERJ6-£r$El9t,*O):2
I?, iltWEJI,]f:.7tmi"/ r':/ r.: n I?
1-':/(*~JII,(tl!, 1969) iJ'

nodosus ~~tr:2
Gnathodus bilineatus-G. commutatus TIl' (KOIKE, 1967), tJ\ffEERJ6-m:rmH~O):2/ 1-':/ HtEIlf (Hisaharu IGo, 1973), ~ I? I:' t~ JlI:t& iff $'l il~ £ 0) Gnatnodus
bilineatus-G. nodosus-G. commutatus {tEIlf (Hisayoshi IGO & K013AYASIII, 1974) ~c ll'Il~t.dtEIlf~-e~ fJ, wlfaEIR¥'i"O) Endothyra ;1#0)-fl\1i;t, P C >b~t*O) Chesterian
9='$, :l - P 'Y ,,{ 0) Visean J::flIlfc~t tt; ~ Q c
iIJt ill ~jt Jl!i

~O)

*

n

* -=
<

species recognized in the Upper Viseanof Europe or the Chesterian of North
American Mississippian.
Deep thanks is expressed to Professors
Mosaburo KANUMA and Professor Tatsuaki KIMURA of Tokyo Gakugei U niversity, Associate Professors Hisayoshi IGO
of University of Tsukuba and Toshio
KOIKE of Yokohama National University
for their continuous encouragement andcritical reading of this manuscript.
Thanks are also due Associate Professor
Atsushi ISHII and Mr. Hisaharu IGO ofTokyo Gakugei University and Mr. Fumio
KOBA YASH! of Tokyo University of
Education, for their kind advice and help
in various ways.

Introduction and acknowlegements

The Endothyra Zone established by
HASEGAWA et al. (1969) in the Lowest
Omi Limestone Group distributed inwestern part of Niigata Prefecture yields
many conodont species which are widely
recognized in the Lower Carboniferous.
Carboniferous conodont faunas of Japan
were described and illustrated from the
Nagoe Formation of the Atetsu Limestone(KOIKE, 1967), Ohkubo area of the Lowest
Akiyoshi Limestone (Hisaharu IGo. 1973)
and Itsukaichi district of Western Tokyo(Hisayoshi IGO & KOBAYASHI, 1974).
The present paper deals with a conodont
fauna from the Endothyra Zone of the
Omi Limestone. The fauna recognizedfrom this zone is closely similar to theabove mentioned faunas. Namely, it ischaracterized by the occurrence ofCnathodus bilineatus, C. nodosus and C.
commutatus, which were well known

Remarks on the lowest part of
the Omi Limestone

The Omi Limestone Group is distributed
in a wide belt, trending northwest andsoutheast in the Nishikubiki County of
Niigata Prefecture, Central Japan. The* Received March 31, 1975; read Jan. 25,
1969 at Tokyo.

156

651.

Mississippian Conodonts from the Omi Lime.stone

lowest part of this limestone group wasstudied repeatedly by HA YASAKA (1924),
KAWADA (1954), FUJITA (1958), SAKAGAMI(1962, 1963), IGO & KOIKE (1964), ROWETT& MINATO (1968), HASEGAWA et al. (1969)
and WATANABE (1974).
Among the above, rather detailed
geology and paleontology were contributed by KA WADA and FUJITA. Theirlowest division was characterized by theMillerella-Coral-Brachiopod Zone, which
was distributed in a narrow belt trending
northwest and southeast along the
Kurohime-Myojyo Tectonic Line in theltagamine district of the Omi Limestone.
This zone was measured in thickness

157

about 250 m by KA WADA and 400 m by
FUJITA.
On the basis of fusulinacean and endothyroid foraminiferas, the strata of thelower facies of the pre-Moscovian were
subdivided into two zones by HASEGAWA
et al. (1969), namely, the Endothyra Zone
and the Eostaffella-Millerella Zone. According to the faunal distribution, they
thought that the Carboniferous strata of
the lower facies had formed an arcuatedarrangement which was separated in
distribution into the inner and the outer.
As the result, HASEGAWA et al. proved
more extensive distribution of the Lower
Carboniferous than that of the previously/ItI: ....

2S(j"ITAGAMINE

100

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

.....
"

......

0,

Text-fig. 1.

...

-~-~-

.....

MT. KUROHIME

250m

'

Index map showing the locations of two sections for this conodont study.

158

Kozo WATANABE

published geologic maps. The thicknessof the pre-Moscovian zones are about
150 m and 170 m, respectively.
Recently, in the lowest fusulinaceanzone, WATANABE (1974) recognized the
Eostaffella kanmerai Zone, however, thedistribution and thickness of this zone
are still open.
These zones are delimited at theirbase by pyroclastic rocks composed ofbasic tuffs and breccia tuffs. In theareas of calcareous sediments in the
Inner Zone of Southwest Japan, thelowest part of the Carboniferous succession is well marked by pyroclastic
rocks; such a succession is recognizedin the Akiyoshi, Taishaku, and Atetsu
areas, except the Omi area where underlying pyroclastic rocks are not so welldeveloped owing probably to the interruption of the so-called Kurohime-Myojyo
Tectonic Line. Therefore, the pyroclastic
rocks which were regarded by KA w ADA(1954) as the base of the Omi Limestone
were considered, according to FUJITA(1958), to be the intrusive dike formed
along the thrust plane. Recently, HASEGAWA et al. (1969) surveyed widely forthis limestone area and founded a goodstratgraphic succession of the lower partat the Fukugaguchi point in the Kurohime district, where the pyroclastic rocks
composed of basic tuffs were comformably overlain by the Endothyra Zone.
The aut her believes that the pyroclastic
rocks, though not whole, is not the basal
part of the Lower Carboniferous limestone, because he found Neoschwagerina
sp. from one of the lenses in them.
Concerning with faunal evidences,
HA Y ASAKA (1924) once discriminated that
the Omi fauna was very prolific inbrachiopod and coral faunas including
Gigantoproductus edelburgensis (PHILLIP),
Syringothyris cuspidatus MARTIN andother species. And he stated that Gigan-

toproductus was from the uppermost partof the Lower Carboniferous or from thetransitional zone between the Lower andUpper Carboniferous. According to IGO& KOIKE (1964), the above Syringothyris
cuspidatus, which was said to be anindicator of the Tournaisian, is one of
the characteristics of the Omi Limestone
fauna.
FUJIT A discussed that the coral fauna
including Lithostrotion somaense, Amygdalophyllum giganteum, Lonsdaleia florijormis and Axophyllum centro tum fromhis lowest zone (C l ) in the Itagamine,
which were indicating the Upper Mississippian of North America or the Lower
Namurian of Europe.
As to the bryozoan fauna SAKAGAMI(1962, 1963) described Fenestella cfr.
triserialis URLICH, etc. F. triserialis was
originally reported from Keokuk Groupof the Middle Valmeyeran of North
America and also reported from theLower Carboniferous of U. S. S. R. He
stated that the Omi bryozoan fauna wasmore related to the Russian fauna rather
than the North American one.
IGO & KOIKE (1964) described theconodont fauna from the Omi Limestone
consisting of the Streptognathodus expansus-S. suberectus faunule from theammonite-bearing limestone which occurred in the Millerella-Coral-Brachiopod
Zone. This faunule indicates the Lower
Pennsylvanian or the Upper Namurian.
In the micro-biostratigraphical studies
on the foraminiferal faunas of Chugoku
region, Southwest Japan, OKIMURA (1966)
discussed the geologic'age and correlationof the lowest part of the Omi Limestonedepending on the INAMURA'S collection.
The endothyrid-paleotextularid faunuleand the Eostaffella-Millerella faunule
were discriminated by him in the lowest
part of the Omi Limestone. According
to OKIMURA, these faunules were very

651.

Mississippian Conodonts from the Omi Limestonesimilar to the assemblages of the Endostaffella delicata Zone and the Eostaffella
sp. A-Millerella sp. A Zone as well in
the Chugoku region, and both zones werecorrelated to the Upper Valmeyeran andthe Upper Chesterian Oi" the Middle
Visean and the Lower Namurian.
HASEGAWA et al. (1969) mentioned thesimilarity of fossil assemblages and lithofacies of the Omi Limestone to the Ohkubo area of the Lowest Akiyoshi Limestone Group, though they have notreferred to the geologic age of theEndothyra Zone of the Omi Limestone.
The Ohkubo fauna consisting of smaller
foraminiferas (OKIMURA, 1966), rugose
corals (MINATO & KATO, 1963, OTA,
1968), brachiopods (YANAGIDA, 1965) andconodonts (Hisaharu IGo, 1973) seems to
be divergent in the geologic age. However, they summarized that the geologic
age of this fauna indicated the Viseanor the Upper Mississippian.
From above mentioned evidences, thegeologic age of the lowest part of the
Omi Limestone is the Lower to Upper
Visean or the Valmeyeran to Chesterianof North America.

Previous conodont studies
The first discovery of Carboniferous
conodonts in Japan was made by IGO &KOIKE (1964) from the ammonite-bearing
limestone which occurred from theMillerella-Coral-Brachiopod Zone of the. Omi Limestone. They discriminated thefollowing species Streptognathodus expansus IGO & KOIKE, S. suberectus DUNN,
Idiognathodus parvus DUNN, Idiognathoides noduliferus (ELLISON & GRAVES),
I. convexus (ELLISON & GRAVES), 1.
opimus (IGO & KOIKE), and many otherspecies. This conodont fauna is very
similar to those of Idiognathodus parvlls-

159

Idiognathoides noduliferus Zone (K-II) of
the Kodani Formation of the Atetsu
Limestone (KOIKE, 1967) and Streptognathodus expansus-S. suberectus Zone of the
Bird Spring Formation of Southern
Nevada (DUNN, 1970). It was considered
to be equivalent to the parts of G, andG2 , the goniatite zones of the European
Namurian to Westphalian, or the Upper
Morrowan of North America. In thepresent study, this conodont assemblage
appears in the middle part of the Sections
II, III, and IV.

Conodont fauna
As mentioned before, the Endothyra
Zone in the Itagamine district establishedin the lowest subdivision of the Omi
Limestone is restricted in distribution
along the Omi river. This limestone ismassive throughout and has no stratification. Accordingly, the author measured
seven sections not only in vertical but
also horizontal directions. More than 100
samples were collected from these sections.
The vertical sections from N-I to N-V
were measured in the Nishiyama quarryof the Denki-Kagaku Mine and thehorizontal sections, N-I and K-I, in the
Nishiyama and Higashiyama quarries ofthis mine (Text-fig. 1).
Fortunately, an excellently preserved
conodont fauna was found from all sections. The vertical sections from N-II
to N-V yield the Lower to Middle Pennsylvanian conodonts, and the horizontal
sections N-I and K-I contain the Upper
Mississippian conodonts. The present
paper treats only upon the Mississippian
condont assemblages from two horizontal
sections. The Pennsylvanian conodonts
will be published by the author in thenear future.
Section N-I: This horizontal section
was measured in the outer part of the160

Kozo W AT ANABE

Endothyra Zone at the Nishiyama quarryof the Denki-Kagaku Mine in the 1tagamine district. More than 25 samples
were collected and conodonts were recovered from 6 samples.
Numerous
conodonts were separated from grey towhite sparry limestone, and the following
species were discriminated; Gnathodus
bilineatus (ROUNDY), G. commutatus(BRANSON & MEHL), G. nodosus (BISCHOFF), Callusgnathus unicornis (YOUNGQUIST & MILLER), c. sp., Spathognathodus
campbelli REXROAD, S. minutus (ELLISON),
Ozarchodina compressa REXROAD, Apatognathus? sp., Magniratelella sp., andHindeodella sakagamii 1GO & KOIKE.
Among the above, Gnathodus bilineatus,
G. commutatus and Cavusgnathus unicornis
are predominant. The following fossils
were found from the preparations;
Eostaffella kanmerai (1Go), Endothyranopsis sp., and Hexaphyllia sp. Thesefossils were known in the Onimaruan ofJapan or the Visean of Europe. Therefore,
this measured section, which was referredto the outer part of the Endothyra Zone,
seems to be able to include the Eostaffellakanmerai Zone (WATANABE, 1974) or the
Eostaffella-Millerella Zone of HAS EGA w A
et al. (1969).
Section K-J: This section was alsomeasured horizontally in the inner partof the Endothyra Zone, which was situatedin the central part of this limestonecomplex. This horizontal section of thisstratum is similar to the horizon ofGigantoproductus edelburgensis-bed described and illustrated by HAY ASAKA(1924). Crinoidal, massive and whitesparitic limestone yields many species,
namely, Gnathodus bilineatus (ROUNDY),
G. dr. bilineatus (ROUNDY), G. commutatus(BRANSON & MEHL), G. nodosus (BISCHOFF), Spathognathodus campbelli REXROAD, S. minutus (ELLISON). Ozarchodina
compressa REXROAD, O. subequalis (HIG.

GINS), Neoprioniodus scitulus (BRANSON &MEHL), N. loxus REXROAD, Hindeodellasegaformis BISCHOFF, H. sakagamii 1GO &KOIKE, Hindeodus alatoides (REXROAD &BURTON), Magniratelella sp., and Gen. et
sp. indet.
This fauna is characterized by the occurrence of Spathognathodus campbelli,
Gnathodus bilineatus, G. cfr. biiineatus,
G. commutatus and G. nodosus. and also
is marked by the frequent occurrence ofHindeodella segaformis and Gen. et sp.
indet. The last species is well known in
the Scaliognathus anchoralis Zone (upperTn,,) of Europian Tournaisian (MARKS &WENSINK, 1970; GROESSEMS, 1974). The
indeterminable genus is quite enigmatic,
because it has four processes. This
somewhat resembles
Lambdagnathus
REXROAD from the Chesterian of North
American Mississippian. but Lambdagllathus consists of three denticulate processes instead of four. However. thepresent material occurs rarely andfragmental in this section. therefore. thespecimens are not referable to any extant
genus and so they are thought to bescientifically new and should be namedin the future. As cited on Table 1, there
are no remarkable faunal change between
the collections. The author has not found
any primitive fusulinacean from thesamples containing many endothyroid
foraminiferas. The occurrence of Gigantoproductus edelburgensis in this section
indicates the Onimaruan of Japan or
the Upper Visean of Europe.
Correlation: The two conodont faunas
from the Endothyra Zone in the Omi
Limestone are quite related with eachother, although the K -I horizon seems tobe slightly lower than that of the N-1
for the occurrence of fusulinacean.
Namely, the N-1 fauna containing Eostaffella kanmemi consists mainly of thetwo markers Gnathodus bilineatus and651.

Mississippian Conodonts from the Omi Limestone

C. commutatus, and also the K-I faunacontaining Endothyra spp. is characterized
by the co-occurrence of the three markers
Cnathodus bilineatus, C. commutatus andC. nodosus.
Association of conodont elements,
comparable with those found in the N-I
and K-I faunas, has been reported fromvarious parts of the world. Faunas with
Cnathodus bilineatus, C. commutatus andC. nodosus have been recognized inGermany (BISCHOFF, 1958; MEISCHNER,
1962), Belgium (HIGGINS & BOUCKAERT,
1968), England (HIGGINS, 1961; RHODES
et aI., 1969), Spain (MARKS & WENSINK,1970), North America (REXROAD &COLLINSON, 1962; WEBSTER, 1969; DUNN,
1965; COLLINSON et aI., 1971; LANE &STRAKA, 1974) and Japan (KOIKE, 1967;
Hisaharu IGo, 1973; IGO and KOBAYASHI,
1974).
In the Griotte Limestone of Spain, thetwo bio-zones with many similar associations were descriminated in the Upper
Visean (CuIIIa-CuIIIr) by MARKS &WENSINK (1970), which were upwardly
the Cnathodus commutatus commutatus
Zone and C. commutatus nodosus Zone.
The basal part of the C. commutatuscommutatus Zone yielded C. typicus andin the lower part of the C. commutatus
nodosus Zone, Cnathodus girtyi was associated with the zone markers. The
two species are not found in the Omi
faunas.
RHODES et al. (1969) found the comparable zonal sequence in the Avon Gorge,
England. The three markers, Cnathodus
bilineatus-C. commutatus-C. nodosus, werecharacteristic species in the lower,
Mestognathodus beckmanni-C. bilineatus
Zone and the upper, Cnathodus mono nodosus Zone. Cnathodus girtyi and Mestognathus beckmanni were also thecharacteristics in these zones which were
unknown in the Omi faunas. They cor-161

related these zones with CuIIIa and CuIII,8
of European zones and with the C.
bilineatus-Cavusgnathus chamctus Zoneof North America.
It is possible, though not precisely, tocorrelate the Omi faunas with those fromthe Chesterian successions in North
America.
The upper part of the
Chesterian was marked by the occurrenceof Kladognathus mehli, K. primus, Cavusgnathus naviculus, and Cnathodus girtyi.
The first two species have not yet been
known in the Omi and the other faunasin Japan, except for Kladognathus sp.
from the upper part of the Nagoe Formation (KOIKE, 1967). The Omi fauna issimilar to that of the Lower to Middle
Chesterian than of the Upper Chesterian.
The conodont-bearing Carboniferous
limestone have been described from a
few areas in Japan. KOIKE (1967) reported
a succession of conodont fauna from the
Nagoe and Kodani Formations in Southwest Japan which ranges from Upper
Mississippian to Middle Pennsylvanian.
His Mississippian Cnathodus bilineatusC. commutatus nodosus Zone correlated
to the Middle Chesterian is very similar
to that of the Omi ones.
Faunas with Cnatlwdus biiineatus, C.
commutatus, C. nodosus, C. homopunctatus
and C. cfr. texanus was described by
Hisaharu IGO (1973) from the Ohkubo
area of the Lowest Akiyoshi Limestone,
Southwest Japan. This Ohkubo fauna
was correlated by him to the Upper
Visean or the Chesterian.
Recently Hisayoshi IGO and KOBAYASHI(1974) reported a succession of conodont
faunas from the Mitsuzawa Limestone,
western part of Tokyo. The lower
conodont fauna with C. bilineatus, C.
nodosus and C. commutatus was concludedby them to the late Chesterian of North
America or the early Namurian rather
than the late Visean of Europe.

162

Kozo WATANABE
Table 1.

Distribution of conodonts from the Omi Limestone.
K-I

N-I

Sections
Sample number

2

Cnathodus bilineatus ......... .
C. cf. bilineatus····· .. " ...... .
C. commutatus ............... .
C. nodosus ................... .

21

3

4

6

8

1 29

8

3

2

233

Cavusgnathus unicornis ....... .
C. sp. . ...................... .

1

3

1

3

Spathognathodus campbelli ... .
S. minutus ................... .

1

2

467

9

10 11

2
2

7

3

1 2
121
12
5

5 18 13
3

159

3

Ozarchodina compressa ....... .
O. subaequa[is ................ .

3

Neoprioniodus scitu[us··· ...... .
N. loxus ..................... .

446
2

Hindeodella segajormis ....... .
H. sakagamii ................. .

2

f
f

f

f

f

Hindeodus alatoides ........... .

2

Magniratelella sp.

2

Apatognathus ? sp. . .......... .

f

2

Gen. et sp. indet.··············
Total

2

4

10 31

4

45 13

3

1 15 48 30

170

2

f: fragment

According to the repeating studies
regarding the corals, smaller foraminifers
and brachiopods, the age of above
mentioned faunas of Japan has beenthought to be the early to late Visean.
In conclusion, the conodont fauna fromthe Endothyra Zone of the Lowest Omi
Limestone is entirely lacking Gnathodus
girtyi and its subspecies, which are rather
common in European Visean or the late
Chesterian and also does not yield
Gnathodus texanus and its related species
which are the characteristic in the Middle
Valmeyeran of North America. Therefore. the present fauna is considered torepresent a part of the Middle Chesterianof North America or the Upper Viseanof Europe.

Systematic description

Genus Cavusgnathus HARRIS &HOLLINGWORTH, 1933

Type species:

Cavusgnathus

HARRIS & HOLLINEWORTH, 1933

Cavusgnatlzus sp.
PI. 15, Fig. 3

altus

651.

Mississippian Conodonts from the Omi Limestone

Remarks: The present material isfragmental, but it is similar to
Cavusgnathus unicornis with short stout
shape, high platform, deep medium troughand short blade. However, it is distinguished from Cavusgnathus unicornisby the absence of hornlike posterior denticle of blade.
Material studied and occurrence: 4specimens from (1) and (2) of the Sec.
N-1.
Reg. Nos.: TGU 1100, 1101.
Cavusgnathus unicornis

YOUNGQUIST & MILLER
PI. 15, Figs. 1, 2, 4-6

Cavusgnathus unicornis YOUNGQUIST & MILLER, 1949, p. 619, pI. 101, figs. IB-23;
REXROAD, 1957, p. 17, pI. 1, fig. 7;
REXROAD, 195B, p. 17, pI. 1, figs. 6-11.;
REXROAD & BURTON, 1961, p. 1152, pI.
13B, figs. 10-12; REXROAD & COLLINSON,
1963, p. 9, pI. 1, figs. 26, 27; REXROAD &Fl'RNISH, 1964, p. 670, pI. 111, fig. 6;
REXROAD & NICOLL, 1965, p. IB, pI. 1,
figs. IB-20; KOIKE, 1967, p. 294, 295, pI. 1,
figs. 2, 3;T HOMPSON & GOEBEL, 196B, p.
23, pI. 1, figs. 2, 5, 6, B.

Remarks: Immature forms (PI. 15, Figs.
4-6) have distinct transverse ridges anda large horn-like posterior denticle ofblade than that of the adult form (PI. 15,
Figs. 1, 2).
Material studied and occurrence: 7
specimens from (1), (2) and (6) of theSec. N-1.
Reg. Nos.: TGU 1102, 1103, 1104.

163

PI. 14, Figs. 1-5

Polygnathus bilineatus ROUNDY, 1926, p. 13,
pI. 3, figs. lOa-10c.
Gnathodus bilineatus, HASS, 1953, p. 79, pI.
14, figs. 25-29; REXROAD & FURNISH,
1964, p. 670; DUNN, 1965, p. 114B, pI. 140,
figs. 7-9; WIRTH, 1967, p. 205, pI. 19, figs.
6-9; KOIKE, 1967, p. 296, pI. 1, figs. 9-11 ;GL013ENSKY, 1967, p. 440, pI. 5B, figs. 9,13; IGO & KOIKE, 196B, p. 29, pI. 3, fig.
6; RHODES, AUSTIN & DRUCE, 1969, p.
94, pI. IB, figs. 14-17; WEBSTER, 1969, p.
30, pI. 5, figs. 11-12; DUNN, 1970, p.
330-331, pI. 62, figs. 13, 14; MARKS &WENSINK, 1970, p. 25B, pI. 2, figs. 3a-h,
4; Hisaharu IGo, 1973, p. 192-193, pI. 29,
figs. 1-6; IGO & KOBAYASHI, 1974, p.419420, pI. 56, figs. 1-3; LANE & STRAKA,
1974, p. 72-77, pI. 32, figs. 1-5, 7, 9, 1113; pI. 33, figs. 11-13, 19-23, 25, 2B-32;
pI. 34, figs. 13-26; pI. 40, fig. 27.
Gnathodus bilineatus bilineatus, BISCHOFF,
1957, p. 21-22, pI. 3, figs. 11, 15; pI. 4,
fig. 1; HIGGINS & BOUCKAERT, 196B, p.
29, pI. 3, fig. 9.

Remarlzs: LANE and STRAKA (1974)
described many specimens from the late
Mississippian of Arkansas and Oklahoma
and discriminated four morpho types basedon the outer lobate platform ornament.
The Omi specimens have concentric nodose ridg.es parallel to the outer margin of
the lobate platform, therefore, which arereferred to morphotype (3 of Gnathodus
bilineatus.
Material studied and occurrence: 60
specimens from (1), (2), (4), (6) and theSec. N-I, and 3 specimens from (6) and(7) of the Sec. K-1.
Reg. Nos.: TGU 1105, 1106, 1107, 1108,
1109, 1110.

Genus Gnathodus PANDER, 1856
Type species:
PANDER, 1856.

Gnathodus mosquensis

Gnathodus bilineatus (ROUNDY)

Gnathodus dr. bilineatus (ROUNDY)
PI. 14, Figs. 6, 7

Remarks:

The present specimen isKozo WATANABE

164

similar to Gnathodus commutatus, however, the inner platform is widely inposterior part along the carina and has
a low ridge. Some nodes developed on
the inner platform.
Material studied and occurrence: 4specimens from (4), (6) and (7) of theSec. K-I.
Reg. No.: TGU 1111.
Gnathodus commutatus(BRANSON & MEHL)

Pl. 14, Figs. 8-11
SPathognathodus commutatus BRAJ'SO:" &MEIIL, 1941, p. 98, pl. 19, figs. 1-4.
Gnathodus commutatus, REXROAD & BURTON,
1961, p. 1153, pI. 39, figs. 1-3; HIGGINS &BOCCKAERT, 1968, p. 30, pI. 2, fig. 5;
RHODES, ACSTI:" & DRUCE, 1969, p. 95,
pI. 19, figs. 9-12; WEBSTER, 1969, p. 31,
pl. 5, fig. 13; Hisaharu IGo, 1973, p. 193194, pI. 29, figs. 8-13; IGO & KOBAYASHI,
1974, p. 420-421, pI. 56, figs. 6, 7.
Gnathodus commutatus commutatus, BISCHOFF,
1957, p. 23, pI. 4, figs. 2-6, 15; KOIKE,
1967, p. 296, pI. 1, figs. 12-16; WIRTH,
1967, p. 206, pI. 19, figs. 10, 11; DU:":-I,
1970, p. 331, pI 62, figs. 11, 12; MARKS &WI,:-;SIXK, 1970, p. 285, pI. 3, figs. 1a-b;
LA:"E & STRAKA, 1974, p. 77-78, pI. 37,
figs. 1-9; pI. 40, figs. 15-18, 23-26.
Gnathodus scotiaensis GLOBENSKY, 1967, p.
441, pI. 58, figs. 2-7, 10, 12.

Remarks: A detailed synonymy was
given by RHODES, AUSTIN & DRUCE(1969, p. 95-96).
Material studied and occurrence: 13
specimens from (1), (2), (3), (6) and (8) of
the Sec. N-I and 21 specimens from (7),(9) and (10) of the Sec. K-I.
Reg. Nos.: TGU 1112, 1113, 1114, 1115,
1116, 1117, 1118.

Gnathodus nodosus BISCHOFF

Pl. 14, Figs. 12-16Gnathodus commutatus nodosus BISCHOFF,
1957, p. 23-24, pI. 4, figs. 12, 13; HIGGINS, 1961, p. 213, pI. 10, figs. 7, 8; KoIKE, 1967, p. 297, pI. 1, fig. 19; WIRTH,
1967, p. 207-208, pI. 2, figs. 15-18; MARKS& WENSINK, 1970, p. 260, pl. 3, figs. 3, 4.
Gnathodus nodosus, RHODES, AUSTIN & DRUCE,
1969, p. 104--105, pl. 19, figs. 16a-20c;
Hisaharu IGo, 1973, p. 194, pI. 19, figs.
14-17; IGO & KOBAYASHI, 1974, p. 421,
pI. 56, figs. 8-12.

Remarlls: All recovered specimens
referable to Gnathodus nodosus BISCHOFF
from the Omi Limestone vary in form
from nodose ridge on both sides of theplatform to fused into a lengthened node
extending anteriorly. These specimens
occur within one rock sample. Therefore,
it seems to display some morphologicalgradation within a species.
Material studied and occurrence: 1
specimen from (3) of the Sec. N-I and
10 specimens from (2), (7) and (9) of theSec. K-I.
Reg. Nos.: TGU 1119, 1120, 1121, 1122.

Genus Hindeodella ULRICH& BASSLER, 1926
Type species:BASSLER, 1925.

Hindeodellasubtilis

Hindeodella segafonnis BISCHOFF
PI. 15, Figs. 8-10
Hindeodella segaformis BISCHOFF, 1957, p.
28-29, pI. 5, figs. 40, 41a-b, 43; MARKS &WENSINK, 1970, p. 265, pI. 1, figs. Za-b;
AUSTIN & GROESSEXS, 1972, pI. 1, figs.
13, 19.

Remarks: The present specimens are
fragmentary. However, it is distinguished from the other hindeodellids by651.

Mississippian Conodonts !1'om the Omi Limestone

the pronounced angular zig-zag bending
bar and a larger denticles oh the apexof each bend.
Material studied and occurrence: Only
fragments from (7), (9) and (10) of theSec. K-1.
Reg. Nos.: TGU 1123, 1124.

165

Genus Magnilaterella REXROAD& COLLINSON, 1963
Type species:

Magnilaterella robsta

REXROAD & COLLINSON, 1963.

Magniraterella sp.
Hindeodella sakagamii IGO & KOIKE

PI. 15, Figs. 15, 16

PI. 15, Fig. 7

Remarks: The present specimen isclosely related to a species of Ligonodina.
The largest denticle on the lateral bar,which is characteristic in this genus,
occures near the midpoint.
i\I/aterial studied and occurrence: 1
specimen from (1) of the Sec. N-I and 2
specimens from (6) of the Sec. K-1.
Reg. No.: TGU 1127.

Hindeodella sakagamii leo & KOIKE, 1964, p.
184, pI. 27, figs. 1, 2; leo & KOIKE, 1965,
p. 85, pI. 8, figs. 1, 2; KOIKE, 1967, pI. 4,
fig. 4.

Material studied and occurrence: Only
fragments from (1) to (8) of the Sec. N-I
and (2) of the Sec. K-1.
Reg. No.: TGU 1125.

Genus Ozarchodina BRANSON& MEHL, 1933

Genus Hindeodus REXROAD& FURNISH, 1964
Type species: Trichonodina i11lperjecta
REXROAD, 1957.
Hindeodus alatoides(REXROAD

typicaPI. 14, Figs. 20, 21

PI. 15, Fig. 17
Falcodus? alatoides REXROAD & Bl:RTO:",
1961, p. 1152, pI. 140, fig. 8.
Hindeodus alatoides (Rl':XROAD & B17RTO:"),REXROAD & FUR:"ISH, 1964, p. 67, pI. 111,
figs. 18, 19; REXROAD & NIcOLL, 1965,
p. 20, pI. 2, fig. 10; KOIKE, 1967, p. 304,
pI. 4, figs. 5-10.

Remarks: The above mentioned synonymy was given by REXROAD & NICOLL(1965, p. 20).
Material studied and occurrence:

Ozarchodina

Ozarchodina compressa REXROAD& BURTON)

specimen from (10) of the Sec. K-1.
Reg. No.: TGU 1126.

Type species:

BRANSON & MEHL, 1933.

1

Ozarchodina compressa REXROAD, 1957, p. 36,
pI. 2, figs. 1, 2; Rl':XROAD, 1958, p. 24,
pI. 6, figs. 1, 2; REXROAD & BURTON,
1961, p. 1156, pI. 141, figs. 16, 17; REXROAD& NIcOLL, 1965, p. 24, pI. 2, figs. 3, 4;
TUOMPSON & GOEBEL, 1968, p. 40, pI. 3,
figs. 17, 20.

Remarlzs: The present specimens recovered are closely similar to the typespecimens.
Material studied and occurrence: 1
specimen from (1) of the Sec. N-I and 2
specimens from (10) of the Sec. K-1.
Reg. Nos.: TGU 1128, 1129.

166

Kozo WATANABE

Ozarchodina subaequalis (HIGGINS)

Neoprioniodus scitulus

PI. 14, Figs. 22, 23(BRANSON & MEHL)

Subbryantodus subaequalis HIGGINS, 1961, p.
219, pI. 12, fig. 15, text-fig. 6-1.
Ozarchodina subaequalis, MARKS & WENSINK,
1970, p. 267-268, pI. 1, fig. 13 only.
Ozarchodina cfr. recta, DUNN, 1970, p. 338,
pI. 62, figs. 25-26.

Remarks: The present specimen recovered in this study is closely similar
to Ozarchodina subaequalis described by
MARKS & WENSINK (1970). This species
differs from the other ozarchodinids inthe presence of discrete, down-curved
posterior blade.
Material studied and occurrence: 3
specimens from (9) of the Sec. K-I.
Reg. No.: TGU 1130.

PI. 14, Figs. 17, 18

Prioniodus scitulus BRANSO;-'; & MEHL, 1941,
p. 173, pI. 5, figs. 5, 6.
Neoprioniodus scitulus, REXROAD, 1957, p.35,
pI. 2, figs. 22, 26; REXROAD & NICOLL,
1965, p. 23, pI. 2, figs. 11, 12; KOIKE,
1967, p. 307-308, pI. 4, figs. 31, 32;
WEBSTER, 1969, p. 39-40, pI. 7, fig. 13;
RIIODES, AUSTIX & DRUO:, 1969, p. 162163, pI. 22, figs. 9a-10b; Hisaharu IGo,
1974, p. 195, pI. 29, figs. 30, 31.

Remarks: A detailed synonymy was
given by WEBSTER (1969, p. 39-40).
Material studied and occurrence: 15
specimens from (6), (7), (9) and (10) of
the Sec. K-1.
Reg. Nos.: TGU 1132, 1133, 1134.

Genus Neoprioniodus RHODES& MULLER, 1956
Type specimen: Prioniodus conjunctus
GUNNELL, 1931.

Genus SPathognathodus BRANSOlli& MEHL, 1941

Type species: Spathodus primus BRANSON & MEHL, 1933.

Neoprioniodus laxus REXROAD
PI. 14, Fig. 19

Neoprioniodus loxus REXROAD, 1957, p. 34,
pI. 2, figs. 8, 9; REXROAD, 1958, p. 23,
pI. 5, figs. 7-9; REXROAD & BURTON,
1961, p. 1155, pI. 140, fig. 12; REXROAD& COLLINSON, 1963, p. 18, pI. 2, fig. 28;
REXROAD & FURNISH, 1964, p. 674, pI.
111, fig. 26; REXROAD & NICOLL, 1965,
p. 23, pI. 2, fig. 23; THOMPSON & GOEBEL,
1968, p. 38, pI. 3, figs. 4, 12; WEBSTER,
1969, p. 39, pI. 7, fig. 12.

Remarks: A detailed synonymy was
given by WEBSTER (1969, p. 39).
Material studied and occurrence: 2
specimens from (9) of the Sec. K-I.
Reg. No.: TGU 1131.

Spathognathodus campbelli REXROAD
PI. 15, Figs. 11-14

Spathognathodus campbelli REXROAD, 1957, p.
37, pI. 3, figs. 13-15; REXROAD, 1958, p.
25, pI. 6, fig. 9; REXROAD & BURTON,
1961, p. 1156, pI. 141, fig. 15; HIGGINS,
1962, pI. 2, fig. 20; REXROAD & FURNISH,
1964, p. 674, pI. Ill, figs. 23, 24; REXROAD& NICOLL, 1965, p. 26, pI. 1, fig. 6;
GLOBENSKY, 1967, p. 447, pI. 55, figs. 12,
20; KOIKE, p. 310, pI. 3, figs. 26-34;
WIRTH, 1967, p. 233-234, figs. 14-16;
THOMPSON & GOEBEL, 1968, p. 41-42, pI.
4, fig. 11; WEBSTER, 1969, p. 43-44, pI. 7,
fig. 5; DUNN, 1970, p. 339, pI. 64, fig. 31 ;MARKS & WEXSINK, 1970, p. 270, pI. 4,
figs. 9-10; Hisaharu IGo, 1973, p. 196,

651.

Mississippian Conodonts from the Omi Limestone

pI. 29, fig. 23.
Spathognathodus cfr.
AUSTIN

campbelli, RHODES,& DRUCE, 1969, p. 223, pI. 8,

167

K-1.
Reg. Nos.: TGU 1139, 1140.

figs. 1-4.

Remarks: Numerous specimens reo
ferred to this species indicate conspicuous
variation in the arrangement of denticles,
which were already remarked by KOIKE(1967, p. 310).
Material studied and occurrence: 2
specimens from (1) and (2) of the Sec.
N-I and 197 specimens from (6), (7), (9),(10) and (11) of the Sec. K-1.
Reg. Nos.: TGU 1135,1136,1137,1138.
Spathognathodus minutus (ELLISON)
PI. 15, Fig. 18

SPathognathodus minutus (ELLISON), REXROAD& BURTON, 1961, p. 1156-1157, pI. 141,
figs. 10-11; IGO & KOIKE, 1965, p. 88-89,
pI. 9, figs. 16-18; KOIKE, 1967, p. 311, pI.
3, figs. 39-42; WEBSTER, 1969, p. 44, pI.
7, fig. 4; DUNN, 1970, p. 339, pI. 61, figs.
27, 30; DUNN, 1965, p. 140, figs. 15, 21, 24.
SPathognathodus rexroadi WEBSTER, 1969, p.
45, pI. 7, figs. 2, 3.
(Further synonyms: see MERRILL (1973, p.
305-306»

Remarks: MERRILL (1973) summarized
the Mississippian-Pennsylvanian spa thognathodids depending on the biometrics
and discriminated between SPathognathodus minutus-group and S. ellisoni-groupin the already known specimens of S.
minutus.
The present specimen fall in the transitional form of them. However, the Omi
specimen is closely similar to Spathognathodus rexroadi WEBSTER (=S. minutus by MERRILL) described by WEBSTER(1969) from Southern Nevada.
Material studied and occurrence: 2
specimens from (1) and (8) of the Sec.
N-I and 3 specimens from (9) of the Sec.

Gen. et sp. indet.
PI. 15, Figs. 21-24

Description: Complex unit consistingof four processes; a carina-like posterior
process, two lateral processes and ablade-like anterior process. Anterior
denticulate process is thin with apicaldenticles, usually triangular in shape.
Postero-lateral processes are thick androd-like with stout denticles bending
antero-posteriorly. A basal pit is locatedon the lower surface at the juncture of
the lateral processes with blade-carina
from which the keel and secondary keels
extend posteriorly and toward the lateralprocesses. The anterior blade inclines
somewhat outward and downward, andit may be slightly sinuous.
Remarks: The present specimens recovered are fragmentary. However, thegeneral form is most similar to a speciesof the genus Ancyrodella with no orconsiderably reduced platform. Namely,
Ancyrodella ioides described by ZIEGLER(1958, p. 42, pI. 11, figs. 4-11) from theearly Upper Devonian of Europe is closely
similar to the present specimens with along high blade and two lateral branches.
Probably, it is thought to be a decendant
form of the above species-group. Also,
the present ones are related with Lambdagnathus REXROAD described from the
Chesterian of North America, but it differs particularly in having of four processes instead of three.
Material studied and occurrence: 4specimens from (7) of the Sec. K-1.
Reg. No.: TGU 1141.

168

Kozo lVATANABE
References

AUSTIX, R. L. and GROESSEXS, E. (1972):
The origin and evolution of the middle
Dinantian conodont genera Doliognathus,
Dollymae, Scaliognathus, and Staurognathus and related forms. Extrait desAnnales de la Soc. Geol., Belgique, tom.
95, Fac. II, p. 229-238, pI. 1.
BRAXSON, E. B. and MEHL, M. G. (1941):
Caney conodonts of Upper Mississippianage.
Denison Univ., Bull. Jour. Sci.,
Labs., vol. 35, p. 167-178, pI. 5.
BISCHOFF, G. (195'1):
Die ConodontenStratigraphie desrhenoherzynischen
Unterkarbons mit Berucksichtingung der
Wocklumeria-Stufe undder Devon/
Karbon-Grenze. Abh. Hess. Landesamt.
Bodenforschung., vol. 19, p. 1-64, pIs. 1-6.
COLLIXSON, C., REXROAD, C. B. and THO~'IP­
SON, T. L. (1971): Conodont zonation of
the North American Mississippian. In
SWEET and BELGSTRo:\I (Editor), Symposium on Conodont Biostratigraphy. Geol.
Soc. Am., Mem. 127, p. 353-394.
DCNN, D. L. (1965):
Late Mississippian
conodonts from the Bird Spring For-mation in Nevada. Jour. Paleont., vol.
39, p. 1145-1150, pI. 140.
--- (1970a): Middle Carboniferous conodonts from western United States andphylogeny of the platform group. Ibid.,
vol. 44, p. 312-342, pis. 61-64.
- - (1970b): Conodont zonation near theMississippian-Pennsylvanianboundaryin Western United States. Geol. Soc.
Amer., Bull., ,vol. 81, p.2959-2974, 4 figs.
FCJITA, H. (1958): Geology of Omi Limestone(Per·mo-Carboniferous), Niigata Prefecture. Contr. Inst. Paieont., Tohoku Univ.,
vol. 48, p. 1-60 (in Japanese).
GLOBENSKY, Y. (1967): Middle and Upper
Mississippian conodonts from the Winsor
Group of the Atlantic provinces of Canada.
Jour. Pa/eont., vol. 41, p. 432-448, pis.
55-58.
HASEGAWA, Y. et al. (1969):
Paleozoic
formations of the Omi Limestone Group.
Geol. Soc. Japan, p. 1-25 (in Japanese).
HASS, W. H. (1953):
Conodonts of theBarnett Formation of Texas. U. S. Geol.
Surv., Prof. Paper 243-F, p. 69-94, pis.
14-16.
HAYASAKA, 1. (1924): On the fauna of the

Explanation of Plate 14
Figs. 1-5. Gnathodus bilineatus (ROUNDY)
1. Oral view. x30, from (7) of the Sec. K-I; 2-5. Oral views. x40, from (2), (4), (6)and (8) of the Sec. N-1.
Figs. 6, 7. Gnathodus efr. bilineatus (ROCNDY)
6, 7. Oral views. x 40, from (4) and (7) of the Sec. K-1.
Figs. 8-11. Gnathodus c011!11!utatus (BRANSON & MEHL)
8, 9. Oral views. x 40, from (3) and (6) of the Sec. N-I: 10, 11. Oral views. x 40, from
(7) and (9) of the Sec. K-1.
Figs. 12-16. Gnathodus nodosus BISCHOFF
12, 13. Oral views. x 40, from (3) of the Sec. N-I: 14-16. Oral views. x 40, from (7)and (9) of the Sec. K-I.
Figs. 17, 18. Neoprioniodus scitulus (BRANSON & MEIIL)
17, 18. Lateral views, x 30, from (6) and (9) of the Sec. K-I.
Fig. 19. Neoprioniodus loxus REXROAD
19. Lateral view. x 30, from (9) of the Sec. K-1.
Figs. 20, 21. Ozarchodina compressa REXROAD
20. Lateral view. x 30, from (1) of the Sec. N-I; 21. Lateral view. x 30, from (10) of
the Sec. K-1.
Figs. 22, 23. Ozarchodina subaequalis (HIGGIXS)
22, 23. Lateral views. x 30, from (9) of the Sec. K-1.

W AT ANABE: Mississippian conodonts from Omi Limestone

Plate 14

651. Mississippian Conodonts from the Omi Limestone
authoracolithic limestone of the Om imura in the western part of Echigo.
Sci. Rept. Tohoku Imp. Univ., 2nd Ser.,vol. 8, no. 1, 83 p, pIs. 1-7.
HIGGINS, A. C. (1961):
Some Namurian
conodonts from North Staffordshire.
Ceol. Mag., vol. 98, no. 3, p. 210-224,
pIs. 10-12.
- - (1962): Conodonts from the" Griotte "Limestone of Northwest Spain. Espana
Inst. Ceol. y Minera., Notas y Comull., no.
65, p. 5-22, 3 pIs.
- - and BOUCKAERT, J. (1968): Conodont
stratigraphy and paleontology of theNamurian of Belgium.
Expl. Cartes.
Minieres, Belgium, Mem., no. 10, 64 p.,
6 pIs.
IGo, Hisaharu (1973): Lower Carboniferous
conodonts from the Akiyoshi LimestoneGroup, Southwest Japan. Trans. Proc.
Palaeont. Soc. Japan, N. S., no. 92, p. 185199, pI. 29.
IGo, Hisayoshi and KOIKE, T. (1964): Carboniferous conodonts from the Omi
Limestone, Niigata Prefecture, Central
Japan. Ibid., N. S., no. 53, p. 179-193,
pIs. 27-28.
and - - (1965): Carboniferous conodonts from Yobara, Akiyoshi Limestone,
Japan. (Studies of Asiatic conodonts,
Part 2). Ibid., no. 59, p. 83-91, pIs. 8-9.
- - and -_. (1967): Carboniferous conodonts from Kuantan, Malaya. Ceol.
Paleont. of Southeast Asia. vol. V, p. 2630, pI. III, Univ. of Tokyo Press.
_.- and KOBAYASHI, F. (1974): Carboniferous conodonts from the Itsukaichi
district, Tokyo, Japan. Trans. Proc.
Palaeont. Soc. Japan, N. S., no. 96, p. 411426, pI. 56.
KATO, T. and IISAKA, G. (1934): The Omi
Limestone and Kurohime-Myojyo Tectonic Line. Jour. Ceol. Soc. Japan., vol.
41, p. 417-420 (in Japanese).
KAWADA, S. (1954): Stratigraphical andpaleontological studies of the Omi
Limestone in the Itagamine district,Niigata Prefecture. Bull. Tokyo Univ.,
Education, Ceol. & Min. Illst., no. 31, p.
15-27 (in Japanese).

169

KOIKE, T. (1967): A Carboniferous succession of conodont faunas from theAtetsu Limestone in Southwest Japan.
(Studies of Asiatic conodonts, Part 6).
Tokyo Kyoiku Daigaku, Sci. Repts., Sec.
C, vol. 9, p. 279-318, pIs. 1-4.
MARKS, P. and WENSI='IK, J. (1970): Conodonts and age of the "Griotte" Limestone
Formation in the Upper Aragon Valley(Hueca, Spain). Koninkl. Nederl. Akad.,Westensch, Amsterdam, Proc., Ser. B,
73, no. 3, p. 238-273, pIs. 1-4.
MEISCHUNER, K. D. (1970):
ConodontenChronologie des Deutschen Karbons.
Compte Rendu 6e COllgres Intern. Strat.
Ceol. Carbonif., Sheffield 1967, vol. 3, pI.
1169-1180.
LANE, H. R. and STRAKA II, ]. J. (1974):
Late Mississippian and Early Pennsylvanian conodonts Arkansus and Oklahoma. Ceol. Soc. America, SPecial Paper
152, 139 p. pIs. 32-44.
MERRILL, G. K. (1973): Pennsylvanian nonplatform conodont. Genera, I: Spathognathodus. Jour. Paleont., vol. 47, no. 2,
p. 289-314, pIs. 1-3.
MIKATO, M. and KATO, M. (1963): Fossils
with the Lowest Namurian aspect newly
found by Dr. Y. HASEGAWA in the
Akiyoshi Province. Chikyu Kagaku, no.
66, p. 32-42, pIs. 1-2.
OKI~'IURA, Y. (1966) : Micro-biostratigraphicalstudies on the forminiferal faunas of theLower Carboniferous formations of the
Chugoku region, Southwest Japan. Hiroshima Univ., Ceol. Rep., no. 15, p. 1-46,
pI. 1 (in Japanese).
OTA, M. (1968): The Akiyoshi LimestoneGroup; A geosynclinal organic reef
complex. Akiyoshi-dai, Sci., Mus., Bull.,no. 5, p. 1-44, pIs. 1-31, (in Japanese).
REXROAD, C. B. (1957): Conodonts from the
Chester Series in the type area of Southwestern Illinois.
Illinois Ceol. Surv.,
Rept. Inv. 199, p. 1-;43, pIs. 1-4,
- - (1958): Conodonts from the Glen Dean
Formation (Chester) of the Illinois
Basin. Ibid., Inv. 209, p. 1-27, pIs. 1-6.
- - and BURTO:-';, R. C. (1961): Conodontsfrom the Kinkaid Formation (Chester)170

Kozo WATANABEin Illinois. Jour. Paleont., vol. 35, p.
1143-1158, pis. 138-141.
- - and COLLINSON, C. (1963): Conodontsfrom the St. Louis Formation (Valmeyeran
Series) of Illinois, Indiana, and Missouri.
Illinois Geol. Surv., Rept. Girc., 388, p. 128, pis. 1-2.
- - and _ . (1965): Conodonts from the
Keokuk, Warsaw and Salem Formations(Mississippian) of Illinois. Ibid., 355, p.
1-26, pI. l.
- - and FURNISH, W. M. (1964): Conodontsfrom the Pella Formation (Mississippian)of south·central Iowa. Jour. Paleont.,
vol. 38, p. 667-676, pI. 3.
- - and NICOLL, R. S. (1965): Conodontsfrom the Menard Formation (Chester
Series) of the Illinois Basin. Indiana
Geol. Surv., Bull., 35, p. 1-27, pis. 1-2.
RHODES, F. H. T., AUSTIN, R. L. and DRUCE,
E. C. (1969): British Avonian (Carboniferous) conodont faunas and theirvalue in local and intercontinental correlation. British Mus. (Nat. History),

Bull., Geol., Supp. 5, p. 1-313, pis. 1-31.
ROUNDY, P. V. (1926): The microfauna in
Mississippian formations of San Saba
County, Texas. U. S. Geol. Surv., Prof.
Paper 146, p. 5-23, pis. 1-4.
SAKAGAMI, S. (1962,1963): Lower Carboniferous Bryozoa from the Omi Limestone,
Japan. Part I and Part II, Trans. Proc.
Palaeont. Soc. Japan., N. S., no. 48, p.
321-330, pis. 49-50; no. 49, p. 25-34, pis.
3-4.
STAUFFER, C. R. and PLUMMER, H. J. (1932) :Texas Pennsylvanian conodonts and theirstratigraphic relations.
Univ. Texas.,
Bull., 3201, p. 13-50, 4 pis.
THOMPSOz.;, T. L. and GOEBEL, E. D. (1968):
Conodonts and stratigraphy of the
Meramecian Stage (Upper Mississippian)in Kansas. Kansas Geol. Surv., Bull.,
192, p. 1-56, pis. 1-5.
- . and FELLOWS, L. D. (1970): Stratigraphy and conodont biostratigraphy ofKinderhookian and Osegian (Lower
Mississippian) rocks of Southwestern

Explanation of Plate 15
Figs. 1, 2, 4-6. Gavusgnathus unicorn is YOUNGQUIST & MILLER
1, 4, 6. Lateral views. 2-5. Oral views. 1, 2. x30, 4-6. x40, from (1), (2) and (6) of
the Sec. N-I.
Fig. 3. Gavusgnathus sp.
3. Oral view. x 30, from (2) of the Sec. N-I.
Fig. 7. Hindeodella sakagamii IGO & KOIKE
7. Lateral view. x 30, from (1) of the Sec. N-I.
Figs. 8-10. Hindeodella sega/ormis BISCHOFF
8, 9. Lateral views. 10. Oral view. x 30, from (7) and (9) of the Sec. K-I.
Figs. 11-14. Spathognathodus campbelli REXROAD
11-14. Lateral views. x 30, from (6), (7), (10) and (11) of the Sec. K-I.
Figs. 15, 16. Magniraterella sp.
15. Lateral view. 16. Oral view. x 30, from (6) of the Sec. K-I.
Fig. 17. Hindeodus alatoides (REXROAD & BURTON)
17. Lateral view. x 30, from (10) of the Sec. K-I.
Fig. 18. Spathognathodus minutus (ELLISON)
18. Lateral view. x 30, from (1) of the Sec. N-I.
Fig. 19. Lonchodina? sp.
19. Lateral view. x 30, from (2) of the Sec. N-I.
Fig. 20. Apathognathus? sp.
20. Lateral view. x 30, from (8) of the Sec. N-I.
Figs. 21-24. Gen. et sp. indet.
23, 24. Oral views. 21, 22. Aboral views. x 30, from (7) of the Sec. K-I.

W AT ANABE: Mississippian conodonts from Omi Limestone

Plate 15

651.

Mississippian Conodonts from the Omi Limestone

Missouri and adjacent area. Missouri
Geol. Surv., Water Resources, Rept. Inv.,
no. 45, 263 p. 8 pIs.
WATANABE, K. (1974): Profusulinelia assemblage in the Omi Limestone, Niigata
Prefecture, Central Japan. Trans. Proc.
Palaeont. Soc. Japan., N. S., no. 92, pIs.
51-53, p. 371-394.
WEBSTER, G. D. (1969): Chester throughDerry conodonts and stratigraphy ofnorthern Clark and southern Lincoln
Counties, Nevada. Califo.rnia Univ. Publ.
Geol. Sci., vol. 79, p. 1-121, pIs. 1-8.
WIRTH, M. (1967): Zur Gliederung deshoheren Palaozoikums (Givet-Namur) im
Gebiet des Quinto Real (Westpyrenaen)
mit hilfe von Conodonten. Neues Jahrb.

AtetsuDenki-Kagaku
Fukugaguchi
Higashiyama
Itagamine
Itsukaichi
KodaniKurohime

IIiiJ~'fl!:~{t!!f:rliBIE?- r:J* ?:jji

III
~I~

1il3m

IJ\
!1.k

~

til:!

171

Geol. Palaeont. Abh., Bd. 127, p. 179-244,
pIs. 19-23.
Y ANAGlDA, J. (1973): Early Carboniferous
Visean faunas discovered from Mitsuzawa, Southeastern part of the Kwanto
massif. Part II. Brachiopods. Trans.
Proc. Palaeont. Soc. Japan., N. S., no. 90,
p. 99-112, pIs. 15-16·.
YOUNGQUIST, W. L. and MILLER, A. K. (1949) :Conodonts from the Late Mississippian
Pella beds of south-central Iowa. Jour.
Paleont., vol. 23, p. 617-622, pI. 101.
ZIEGLER, W. (1958): Conodontenfeinstratigraphische Untersuchungenan derGrenze Mitteldevon/Oberdevon und in
der Adorfstufe. Notizbl. hess. L.-Amt
Bodenforsch. 87, p. 7-77, 12 pIs.

Mitsuzawa
MyojyoNagoe
Nishikubiki
Nishiyama
OhkuboTaishaku

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172
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Transactions and Proceedings of the PalaeontologicalSociety of Japan

September 20, 1975

New Series No. 99

CONTENTS
TRANSACTIONS
648. TANABE, Kazushige:

Functional morphology of Otoscaphites puerculus (JIM-

BO), an Upper Cretaceous ammonite .. .. .. .. . . .......... . .. ....... . . . . 109
649.

KOMURA, Seiichi: Ik ebea, eine neue Gattung der pennaten Bacillariaceen
aus den Neogen Japans . ... ... . . . . . . . ...... . ........... . . . .... ...... . 133

650.

IWASAKI, Yasuhide:

On two fossil molluscan species from the Eocene of

the Bonin Islands ........... ... .. ............ .... .. .... ......... ..... 143
651. WATANABE, Kozo : Mississippian conodonts from the Omi Limestone, Niigata
Prefectur~Central Japan . . ............ . .. ... ... .. ..... . ............. 156