ISSN 0031-0204

Transactions and Proceedingsof thePalaeontological Society of Japan
New Series

No.

157

Palaeontologica l Society of Japan
April 30,

1990

Co-Editors

Hisayoshi Igo, Hiroshi Noda and Kei Mori
Editorial Board

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

Officers for 1989-1990
President: Itaru Hayami
Honorary President: Teiichi Kobayashi
Councillors: Kiyotaka Chinzei, Takashi Hamada, Yoshikazu Hasegawa, Itaru Hayami,
Hiromichi Hirano, Hisayoshi Igo, Noriyuki Ikeya, Junji Itoigawa, Tadao
Kamei, Makoto Kato, Tatsuaki Kimura, Itaru Koizumi, Kei Mori, Hiroshi
Noda, Ikuwo Obata, Kenshiro Ogasawara, Tsunemasa Saito, Yokichi Takayanagi, Kazushige Tanabe, Hiroshi Ujiie
Members of Standing Committee: Kazushige Tanabe (General Affairs), Hiromichi Hirano(Finance), Hisayoshi Igo (Editor in Chief, TPPSJ), Hiroshi Noda, Kei Mori (Co-Editors,
TPPSJ), Noriyuki Ikeya (Planning), Kiyotaka Chinzei (Membership), Ikuwo Obata(Foreign Affairs), Yokichi Takayanagi (Editor, "Fossils"), Juichi Yanagida, Sumio
Sakagami (Co-Editors, Special Paper), Tatsuaki Kimura (Friends of Fossils)
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Auditor: Sakae O'Hara
The fossil on the cover is Phillipsia ohmorensis Okubo, an Early Carboniferous trilobite
from the Hikoroichi Formation in the Higuchizawa valley, Ofuna to City, Iwate Prefecture, northeast Japan (Collected by A. Haga, PAt 5766, X 3.0; after Kobayashi and
Hamada, 1980, pI. 6, fig. 4).
All communication relating to this journal should be addressed to the

PALAEONTOLOGICAL SOCIETY OF JAPAN
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Trans. Proc. Palaeont. Soc. Japan, N.S., No. 157, pp. 347-359, 9 Figs., April 30, 1990

893.

EVOLUTIONARY CHANGE IN DIATOM MORPHOLOGYAN EXAMPLE FROM NITZSCHIA FOSSILISTO PSEUDOEUNOTIA DOLIOLUS*--

IT ARU KOIZUMIDepartment of Geology and Mineralogy, Faculty of Science,
Hokkaido University, Sapporo 060
and

YUKIO Y ANAGISA W A
Geological Survey of Japan, 1-1-3 Higashi, Tsukuba, Ibaraki 305

Abstract. Pseudoeunotia doliolus gradually developed its convex dorsal margin fromthe Nitzschia fossilis morphology during the course of time since 2.00 m.y. B.P. Thisdevelopment corresponds with the general trend of the diatom temperature (Td) curveo bserved in the same sedimentary sections. However, the development of the convex dorsal
margin is considered to have likely been caused by a genetic character rather than the effectof surface water temperature decline, because this evolutionary process does not correspondstrictly with the climatic deterioration during the Pleistocene. Our SEM examination of the
diatom valves of P. doliolus and N. fossilis shows that they have the same valve structure
except for the valve symmetry. It is concluded that P. doliolus evolved from N. fossilis at
the beginning of the Pleistocene and that these two species persisted for a period of about one
m.y. until the disappearance of the latter species at 0.6 m.y. B.P. Therefore, this evolutionary change occurred during a time interval of 106 or more years.
Key words.

Diatom, evolution, Nitzschia fossilis, Pseudoeunotia doliolus.

replaced the latter completely in the North
Pacific planktonic population (Koizumi and
Kanaya, 1976).
The disappearance of N. fossilis is remarkably synchronous at 0.6 m.y. B.P. in the
middle- to high-latitudes of the North Pacific(Koizumi and Tanimura, 1985). This datum
level was first proposed by Koizumi and
Kanaya (1976) at the lower part of the
Brunhes Chron (about 0.65 m.y. B.P.) in the
Choshi section of Choshi Peninsula, central
Japan. This species also disappears at an
identical time in the equatorial region (Burckle and Trainer, 1979). P. doliolus isbroadly distributed over the tropical andmiddle-latitudes, so it is an important element

Introduction

From the morphology and structure ofdiatom valves, and from the stratigraphic
occurrence of the species, it is possible tojudge the evolutionary relationships between
some diatom species.
Pseudoeunotia doliolus (Wallich) Grunow
seems to have developed its curved apical axis
during its evolution from Nitzschia fossilis(Frenguelli) Kanaya which is a symmetricalform present at the beginning of the Pleistocene age. The stratigraphic data show that
more than 106 years elapsed before the former'Received March 15, 1989; accepted December 20,
1989
347

Itaru Koizumi and Yukio Yanagisawa348

of both ,tropical and subtropical diatom
assemblages. Its first occurrence is slightly
earlier in the low-latitudes (2.00 m.y. B.P.)
than in the middle-latitudes (l.89 m.y. B.P.)(Koizumi and Tanimura, 1985).
The purposes of this paper are two-fold,namely: (1) to present the stratigraphic
development of the convex dorsal margin in
P. doliolus from N.fossilis, and (2) to
describe the fine valve structures of these two
species based on SEM observations in order
to confirm their evolutionary relationship.

Kanaya, 1976). In addition, samples from apiston core recovered by the R/V Thomas G.
Thompson cruise 49 were also examined (TT49-4: Lat. 35°40.96'N. Long, 157°45.73'E;

Materials and methods
The occurrence of both Pseudoeunotia
doliolus and Nitzschia fossilis were counted
until 20 valves per one sample, except somesamples containing very rarely these species,in the previously reported samples from the
DSDP Site 579 (Koizumi and Tanimura,1985) and the Choshi section (Koizumi and

Figure 2. Measurements of valve asymmetry(a/b) and apical length (I).

50·r----------------,~"'r-----~----------_.----------_r--------~

40·
e DSDP SITE579
eTT49-4

30·

4
NORTH

PACIFIC

OCEAN

!"

N

20·L-________________L -________ ___________ L_ _ _ _ _ _ _ _ _ _
170·
130·E
140·
ISO·
160·
~

Figure 1.

Location of materials used in this study.

~~--------~

180·

893.

349

Evolutionary change in diatom morphology

(f)

U
IW
Z
l!)

e:(

~

E(f)

Td

FREQUE NCY DISTRI BUTIONS
a /b

-

W
J:-1
I- a..
a..~(=Xw/(Xw+Xc))

We:(
Q(f)

ASYMMETRYSYMMETRY

COLD

WARM

o
(f)

W

10

J:

z

20
III

30

e:(

~

E
~

~

40

c

"")

e:(

>:::l

I-

6
e:(

c

>

:I

~

'0

0

1.0

0.8

0.6

0.4

0.2

o

1.0

0.8

0.6

0.4

0.2

o

Figure 3. Stratigraphic distribution in frequencies of the asymmetry index (a/b) for Pseudoeunotia
dolio/us and Nitzschia fossilis, and Td values from the DSDP Site 579.

flaru Koizumi and Yukio Yanagisawa

350

(f)

u

E(f)

I-

~W

W

I...J
1-11.

Z
(!)

e::{

:::?!

FREQUENCY DISTRIBUTIONS

Td(=Xw/(Xw +Xcll

albIl.:::?!
We::{
O(f)

SYMMETRYASYMMETRY

COLD

WARM

0
(f)

W

I
Z
::J

a:
ID

E
c
....

C
J

2

e::{

3
e::{

>-

4

e::{

5
c

>

:>

"C

o
6
1.0

0.8

0.6

0.4

0.2

o

1.0

0.8

0.6

0.4

0.2

o

Figure 4. Stratigraphic distribution in frequencies of the asymmetry index (a/b) for Pseudoeunotia
doliolus and Nitzschia fossilis, and Td values from TT 49-4.

893.

Evolutionary change in diatom morphology

351

C/)
C/)

U

IW
Z
l!)

<1
~

z

OC/)

I- W
<1 ...J
~ ~
a: ~

Td
(=Xw/(Xw+Xc))

FREQUENCY DISTRIBUTIONS

alb

0<1
lL.C/)

ASYMMETRYSYMMETRY

COLD

WARM

C/)

W

:t:
Z

::>

a:
CD

0
~

0
0

>-

E
0

<1'0

J

u.:

~

<1

<1

~

>-

<1
CD

::>
0
I-

«
~
0

>

:l

"0

0

1.0

0.8

0.6

0.4

0.2

o

1.0

0.8

0.6

0.4

0.2

o

Figure 5. Stratigraphic distribution in frequencies of the asymmetry index (a/b) for Pseudoeunotia
dolio/us and Nitzschia fossilis, and Td values from the Choshi section, Choshi Peninsula.

flaru Koizumi and Yukio Yanagisawa

352

Results

metry index (a/b) for P. doliolus are shownby a cluster of bars with a thicker line connecting the arithmetical average in each sample (Figures 3-5). The distributions of theasymmetry index gradually change in time
without a break, because the ranges overlap
one another in the stratigraphy. The stratigraphic distributions of the index for N.
fossilis are also shown as thicker bars.
The frequency distribution of the asymmetry index for P. doliolus obtained from the
DSDP Site 579 are within the range from a/b = 0.89 to 0.25 (Figure 3). The generaltrend in the distributions of this index istoward smaller values in more recent period,
from a/b=0.85 at the lowermost sample
below the Olduvai Event to alb = 0.42 at theuppermost sample near the sea floor. The
large decreases in the index, however, occur at
two horizons; i.e. at the upper boundary of
Olduvai Event and below the Jaramillo
Event. N. fossilis virtually disappears in theearliest part of the Brunhes Chron; a few
sporadic occurrences being noted after the
Jaramillo Event.
The asymmetry index for P. doliolus in thecore TT 49-4 traces a zigzag decline (Figure4). These fluctuations might be due to thesmaller numbers of valves measured in eachsample. N. fossilis disappears in the lower
part of the Brunhes Chron.
The asymmetry index for P. doliolus in the
Choshi section covers a wide range in eachsample, previously decreasing upwards, especially in the interval from the Olduvai to
Jaramillo Events (Figure 5). The last occurrence of N. fossilis lies in the lowest part ofthe Brunhes Chron as in the two sections
previously described.

[IJ Asymmetry index (a/b)
The frequency distributions of the asym-[2J Asymmetry index vs. apical length
The ratio of apical length (1) to asymmetry

1.0• -::Ji- .•••.. - ...... "-.

0.6••,"- I • • •... . ....
. .- ..

-... i'i-

0.6

o

I ••

..

0

0_'0' '0

alb

1-

•• I-

1' •• , •••• : ...

I

0.4

-

••

I •••• ,••_ .... I

... ,

o

0.2

o ~~~--~~~--~~~~~~

o

20

40

60

60

100

Figure 6. Relationship between the asymmetryindex (a/b) and the apical length (I) for
Pseudoeunotia dolio/us from the DSDP Site 579.

water depth 4003 m; core length 744 cm)(Figure 1).
The valve symmetry was measured by theasymmetry index (a/b) defined as a ratio ofwidth in a ventral side (a) and a dorsal side(b) of the transapical axis in a valve (Figure2). In the case of a symmetrical valve, e.g. of
N.fossilis, the ratio (a/b) is equal to 1.
With the progressing asymmetry of the valve
in P. doliolus, however, the ratio (a/b)
decreases toward O. The relationshipbetween the asymmetry index (a/b) and theapical length (1) was also calculated for P.
doliolus.
SEM observation was carried out for valvesof these two species which were picked up
and mounted on sample stages from processedmaterials with a tiny paint brush.

~ Figure 7. 1-2. Nitzschia fossilis (Frenguelli) Kanaya: 1, a/b= 1.00, TT 49-4 (12): 2, a/b= 1.00,
DSDP 579A (5-1). 3-12. Pseudoeunotia doliolus (Wallich) Grunow; 3, a/b = 0.92, Choshi (A-4); 4, a/b=0.83, DSDP 579A (8-1); 5, a/b=0.77, Choshi (A-20); 6, a/b=0:67, TT 49-4 (9); 7, a/b=0.57, DSDP
679A (6-1); 8, a/b=0.43, DSDP 579A (3-4); 9, a/b=0.43, DSDP 579A (2-7); 10, a/b=0.33, DSDP 579A
(I-I); 11, a/b=0.31, DSDP 579A (1-3); 12, a/b=0.22, Choshi (IK 31).

893 .

Evolutionary change in diatom morphology

353

5

3

2

7

8

l,o~m

9
10

11

12

354

Itaru Koizumi and Yukio Yanagisawa

893.

Evolutionary change in diatom morphology

index (a/b) was calculated for 197 valves of
P. dolio/us from the DSDP Site 597 but there
is no specific relationship between these two
measurements (Figure 6).
[3J SEM observation
Pseudoeunotia doliolus (Figure 8): The
areolae of this species are rounded to triangular in shape, with finely perforated cribra(Figures 8-7, 15). They are arranged in two
transapical rows with quincunx pattern
between each two transapical costae (Figure8-15). The transapical costae are equally
spaced but sometimes more narrowly with
only one row of areolae between them (Figures 8 - 1- 4, 12). The external costa has aterminal extension with a small depression on
its top (Figures 8-9,10). The internal costae
often branch at raphe-bearing side so thatfork-like structures are formed (Figure 8-13).
The small knobs are distributed over thevalve face (Figures 8-5, 6). The raphe slit is
not interrupted at its middle point (Figures
8-10, 11). The raphe canal, a circular tube
running below the raphe slit, communicateswith the valve interior through small interspaces between costae (Figures 8-7, 8). An
interspace at the middle point of raphe islarger than others (Figure 8-13). The
chamber-like hollow spaces are present underboth side between each two transapical costae(Figure 8-7).
Nitzschia fossilis (Figure 9): The microstructures of this species observed by SEM isjust the same as those of P. dolio/us. The

355

two rows of areolae between costae (Figure9-4), the branching of internal costae at rapheside (Figures 9-lOa, b), and a large interspaceat the middle point of raphe (Figure 9-9) arealso present in N. fossilis as in P. doliolus.
Furthermore, the irregular narrow spacing oftransapical costae is also observed (Figures 92,3,5).
Discussion
The spatial distributions of diatom events,
defined by first and last appearances in sedimentary sequences, are influenced by the
paleo-position of the subarctic front or thechange of surface water temperature in theunstable oceanic environment of the North
Pacific (Koizumi, 1986b). It is considered,
therefore, that the stratigraphic distributionsof the asymmetry index for P. doliolus and N.
fossilis are also dependent principally upon
the change of Td value (Kanaya and Koizumi, 1966), which is a correlative of thesurface water temperature.
The Td values in the DSDP Site 579 generally decrease upwards with some sharp
fluctuations (Koizumi, 1986b). The first Td
minimum, which has an equivalent degree tothe low Td values during the Brunhes ehron,occurs below the Olduvai Event. Anothersharp drop in Td value occurs slightly above
the Olduvai Event. The Td curve is relatively stable during the interval between the
Olduvai and Jaramillo Events. Large andrhythmic Td fluctuations during the upper+- Figure 8. Pseudoeunotia doliolus (Wallich) Grunow, GH 82-3, RC 226 (cc), bottom sediment of the
Sendai Bay, Japan. Broader scale bar equals 10 pm and narrower one equals I pm. 1, external valve view
(Arrow heads indicate narrower inregular spacing of transapical costae); 2, internal valve view; 3-4,
extenlal oblique views (Arrow heads indicate narrower irregular spacing of transapical costae; 3, raphebearing side; 4, raphe-less side); 5-6, exteternal surface of apex of valve (Arrow head indicates one of theknobs on the valve face); 7-8, sections of valve (r, raphe slit; rc, raphe canal; i, interspace; c, chammberlike hollow space of both mantle; v, cribra of areolae); 9, oblique external view of raphe-less side; 10,
external valve face (Arrow indicates middle point of raphe slit); 11, enlargement of Figure 8-10 (Large
arrow indicates middle point of raphe. Note raphe slit is continuous at this point. Small arrow indicatesa small depression on the top of extension of costa); 12, oblique external view showing narrower irregularspacing of transapical costae (arrrow); 13, internal valve view (Arrow indicates a large interspace at the
middle point of raphe. Arrow head indicates one of the ordinary small interspace. 14, internal view ofvalve apex; 15, internal view showing cribra of areolae.

356

flam Kaizumi and Yukia Yanagisawa~\1 nm IIInilim\ I·•· •••• tr···s·ecm~

Figure 9. Nitzschia fossilis (Frenguelli) Kanaya, TT 49- 4, 630-633 cm. Broader sca le bar equals 10,um and narrower one equals I ,um. 1, e.xternal surface of valve apex ; 2, 3, oblique externa l view showing
narrower irregular spacing of transapical costae (arrow head), 2, raphe-less side, 3, raphe-bearing side ; 4,external valve face and mantle; 5, external va lve view showing narrower irregular spacin g of transapicalcostae ; 6, enlargement of Figure 9 - 7 (Arrow indicates a large interspace at middle point of raphe) ; 7,
oblique internal view; 8, internal va lve view ; 9, enlargement of Figure 9- 10b (Large arrow indicates a large
interspace at middle point of raphe. Small arrow indicates one of ordinary small interspace); lOa - b,internal va lve view (Stereoscopic pair. Arrow indicates a large interspace at the middle point of raphe).

Pleistocene begin near the Jaramillo Event.
Nine Td minima are recognized during theBrunhes Chron. These Td fluctuations arecertainly correlated with the cycles of glacial /interglacial stages.
The development of the convex dorsal

margin in the va lve of P. dalia/us might beaffected by the decrease of surface water temperature. However, no strict correlation canbe recognized between the change of theasymmetry index of P. dalia/us and thefluctuations of Td va lues in the DSDP Site

893.

Evolutionary change in diatom morphology

579 (Figure 3).
The general decline of the Td curve during
the Pleistocene in the Choshi section (Koizumi and Kanaya, 1976) can be correlatedwith the gradual decrease of asymmetry index
of P. doliolus (Figure 5).
The disappearance of N. fossilis in thelower part of the Brunhes Chron seems to berelated to the climatic deterioration as shownby the lowest Td value which is correlatedwith the stage 16 of the oxygen isotope recordin the equatorial Pacific (Koizumi, 1986a)(Figure 3-5).
The SEM observation shows that P.
doliolus and N. fossilis are quite identical invalve structures, except that they differ merely
in valve symmetry. This confirms the evolutionary relationships between the two species,
but presents a problem for the generic separation of Pseudoeunotia from the genus Nitzschia, a situation already noted by Simonsen( 1974).
Kolbe (1954) pointed out the morphological similarity between P. doliolus andNitzschia marina. However, the valve microstructure of N. marina revealed by Akiba
and Yanagisawa (1986) is quite different fromthat of P. doliolus.

Systematic paleontology
Class Bacillariophyceae
Order Pennales
Suborder Raphidineae
Family Nitzschiaceae Grunow, 1860Gen us Nitzschia Hassall, 1845
Nitzschia fossilis (Frenguelli) Kanaya, 1973
Figures 7-1-2; 9Nitzschia fossilis (Frenguelli) emend. Kanaya in
Kanaya et Koizumi ex Schrader. Kanaya andKoizumi, 1970, p.59 (nomen. invalid): Koizumi, 1972, p. 352, pI. 42, figs. 14a-15c (as Nitzschia fossilis Kanaya); Schrader, 1973, p. 707, pI.
4, figs. 9-11, 24, 25; Koizumi, 1973, p. 833 ;Koizumi and Kanaya, 1976, p. 155, pI. 1, figs. 1114.
Synonym.- Pseudonitzschia fossilis Frenguelli, 1949,357

p. 118, pI. 1, fig.7 (not fig. 6); Fragilariopsis
pliocene (8run) Sheshukova-Poretskaya, Kanaya,
1971, p.556, pI. 40.3, figs. 7, 8(not SheshukovaPoretskaya, 1976, p.305-306, pI. 47, fig. 13, pI.
48, fig. 7).

Emended description (Schrader, 1973).Valves elliptical with slightly convex margins
and broadly rounded apices, the middle sometimes more strongly convex, 22-45 Jim long,
6-8 Jim wide. Transapical costae about II
in 10 Jim. Intercostal membrances with twotransapical rows of puncta, about 22 in 10
Jim. Rows punctate, puncta in decussate
arrangement forming oblique rows. Transapical rows and costae near the apices curved.
Puncta near the costae, margin strong, raphe
marginal (Orthographic errors are corrected).
Genus Pseudoeunotia Grunow, 1865
Pseudoeunotia doliolus (Wallich)
Grunow, 1880
Figures 7-3-12; 8Pseudoeunotia doliolus (Wallich) Grunow. Hustedt,
1932, p.259-260, fig. 737; Cupp, 1943, p.190191, fig. 140; Lohman, 1941, pI. 17, figs. 12, 13;
Kolbe, 1954, p.43-44, pI. 3, fig. 41 ; Schrader,'1973, pI. 4, figs. 1-3, 6-8, not 4,5; Simonsen,
1974, p. 56; Koizumi and Kanaya, 1976, p. 155,
pI. 1, figs. 9, 10.

Full description (Hustedt, 1932 translated
in English by Jensen, 1985 with description ofcolony formation and girdle view from thegenus description). Valve side of cells
bound into dorsovental ribbons. Ventral
girdle band side linear, dorsal girdle bandside with slightly convex margins. Valveshalfs lanceolate with bluntly rounded ends;
straight, slightly concave or rarely slightly
convex ventral margin and strongly convex
dorsum, gradually sloping from the middle
toward the ends and often somewhat retracted, 30-70 Jim long, 5-8 Jim wide. Transapical ribs 9-14 in 10 Jim, in between which
are fo.und double rows of delicate areolae inquincunx, about 22 oblique rows in 10 Jim.

358

Itaru Koizumi and Yukio Yanagisawa

Pseudoraphe and central area absent.
Acknowledgments

This paper builds on the fundamental work
on diatoms initiated by Dr. T. Kanaya who
was formerly Professor of Tohoku University.
We would like to thank Professor F.E.
Round of the University of Bristol for a
critical review of this manuscript.
References cited
Akiba, F. and Yanagisawa, Y., 1986: Taxonomy,morphology and phylogeny of the Neogene
diatom maker species in the middle to-high latitudes of the North Pacific. In, Kagami, H.,
Karig, D.E., Coulbourn, W. T., et al. eds.,
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Burckle, L.H. and Trainer, J., 1979: Middle and late
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Cupp, E.E., 1943: Marine plankton diatoms of thewest coast of North America. Scripps Inst.
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Koizumi, I., 1972: Marine diatom flora of the
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vol. 10, p. 309-325, pis. 1-4.
- - and Kanaya, T., 1976: Late Cenozoic marine
diatom sequence from the Choshi district, Pacificcoast, central Japan. In, Takayanagi, Y. andSaito, T. eds., Progress in Micropaleontology, p.
144-159, pI. I, Amer. Mus. Nat History, NewYork.
- - and Tanimura, Y., 1985: Neogene diatom biostratigraphy of the middle latitude western
Pacific, Deep Sea Drilling Project, Leg. 86. In,
Burckle, L.H., Heath, G.R., et al. eds., Initial
Reports of the Deep Sea Drilling Project, vol.
86, p.269-300, pis. 1-6, U.S. Government Printing Office, Washington D.C.
Kolbe, R.W., 1954: Diatom from equatorial cores.
Reports of the Swedish Deep Sea Expedition
1947-1948, vol. 6, p. 1-49, pis. 1-4.
Lohman, K.E., 1941: Geology and biology of North
Atlantic deep-sea cores between Newfoundlandand Ireland. Part 3, Diatomaceae. U.S. Geol.
Surv. Prof. Paper, 196-B, p. 55-86, pis. 12-17.
Schrader, H. -J., 1973: Cenozoic diatoms from thenortheast Pacific, Leg. 18. In, Kulm, L.D., Von
Huene, R., et al. eds., Initial Reports of the
Deep Sea Drilling Project,·vol. 18, p.673-797,
pis. 1-26, U.S. Government Printing Office,Washington D.C.
Scheshukova-Poretskaya, V.S., 1976: Neogene
Marine Diatom Deposits of Sakhalin andKamtschatka. 43Ip., pis. I-50, Leningrad Univ.
Press, Leningrad.
Simonsen, R., 1974: The Diatom Plankton of the
Indian Ocean Expedition of R V "Meteor"
1964-1965. "Meteor" Forschungsergebnisse,
Reihe D, no. 19, p. 1-66, pis. 1-41, Gebruder
Borntraeger, Berlin, Stuttgart.

893.

Evolutionary change in diatom morphology

359:Jl1l~0)~~~~~;:. ~ c -:) < ijHl~*7U - Nitzschia fossilis b' I? Pseudoeunotia doliolus~0)-17~: ~lt~t:Jlllfl Pseudoeunotia doliolus ~;:.~ I?.h 7.> v9 7.> ~ b' tdJJl:t!\ tJ: \" 1.." j~UllJl:t!\Jm~ft*f5~fl Nitzschia fossilis O)~t±l 1.." t..:~~*O)~b' 1?i'0 200 7J~il1JU~ 100 7J~UJ::O)Ili¥
rI3H:'b'Vf-C&<~ ~;:,3eJ!1..,,-C*t..:o P. doliolus O)~iIDtiIH;:,~I?.h7.>~O)~F)t;J~O)~{r.ft-~i¥JtJ:llIJtiJ c 1..,,-c:Jlllml.lt (Td) :j:~~O)iB:{r.CIi'iJWiIl1..,,-C\"7.>b~. jjfij~O)~{r.ft*HI'€fIHU"\,'-C-!ic 1.." -C \, ,tJ:\' '0 -rtJ:b~ P. doliolus O)Jm~O)I* l?~ft~l2B*c]e]JTtlt~Jm -C~ ..:d..:~~.*ml.O)~TKl~-C.~1.."kO)~~~<. 3e~~i¥J~.~Kl~-C.~1.."kc~~I?.h
7.>0 ~ 0) ~ eft P. doliolus c N. fossilis c O):Jlll~~~~~~T!itiHlti~);:'l ~ -cWl.~ 1.." t..:*5*. jjfij~O)il1:~;:.:t-oVf7.>)t;J1*M:O)i!\"~~~. jjfij~b~~ < Il'U c.~0).~~1il'~ -c \"7.> ~ cc.

b'l? ~3Z:1il'~.h7.>0'h'R~. ;j1jPtR.*~

Trans. Proc. Palaeont. Soc. Japan, N.S., No. 157, pp. 360-365, 2 Figs., April 30, 1990

894. A NEW TRILOBITE GENUS RHINOPHACOPS*
ATSUSHI KANEKO
15-7, Fukae-Honmachi 1-chome, Higashinada-ku, Kobe, 658

Abstract. A phacopid genus Rhinophacops is proposed on the basis of Echinophacops
schizoloma Zhou, 1983 described from the Zhusileng Formation (Upper Emsian) of Inner
Mongolia. This new genus is characterized by having an anterior opening during enrollment. Material collected from the Na Member of the Nakazato Formation, Iwate Prefecture, Northeast Japan was described in detail.
Key words. Rhinophacops, trilobite, Devonian, Inner Mongolia, Nakazato Formation,
Northeast Japan.

ian age (Zhou, 1983; Zhan and Ruan, 1983)
and this fossil evidence may suggest that the
Na Member of the Nakazato is close to theEmsian - Eifelian boundary. Furthermore,
the occurrence of the present characteristic
trilobite species from Inner Mongolia andKitakami, Northeast Japan shows closefaunal similarity between both regions.
Acknowledgments: The present author isgreatly indebted to the following persons;Drs. Takashi Hamada (University of Tokyo),Tadao Kamei (Shinshu University), Allen R.
Ormiston (Amoco Production Co., U.S.A.),
Ivo Chlupac (Central Geological Survey,
Prague, Czechoslovakia), Zhou Zhi-quiang(Xi'an Institute of Geology and Mineral
Resources, China), Messrs. Teruo Ono,
Hitoshi Koizumi (Kesen Chishitsu Kenkyusho) and Ken Kawanami (Onimaru Quarry).

Introduction
The present author already describedtrilobites from the Nakazato Formation in
the Kitakami Mountains, Northeast Japan(Kaneko, 1984, 1985). This paper treats ofphacopid specimens collected by Ono fromthe Na Member of the Nakazato Formation
exposed in the Higuchi-zawa, Hikoroichicho, Ofuna to City, Iwate Prefecture. These
specimens are identified with Echinophacops
schizoloma Zhou, 1983 from the Upper Emsian Zhusileng Formation of western Inner
Mongolia (Zhou, 1983). Based on thisspecies, a new genus Rhinophacops is
proposed and the specimens came from the
Nakazato Formation are fully described herein.
The geologic age of the Nakazato Formation was collectively regarded as Middle
Devonian (e.g. Kobayashi and Hamada,
1977; Minato et al., 1979, Murata, 1972 andothers). Copper et al., (1982) studied brachiopods from the Na Member of the Nakazato and insisted that the brachiopods show a
middle to late Eifelian. However, the present trilobite apparently indicates a late Ems-

Systematic paleontology
Family Phacopidae Hawle and Corda, 1847
Genus Rhinophacops Kaneko, gen. nov.

Derivation of genus name.- the Greek
word rhin horn + typical genus Phacops Emmrich, 1839.
Type-species.- Echinophacops schizoloma"Received October 31, 1986; revised manuscript
accepted February 10, 1990
360

894.

A new Trilobite genus

Zhou, 1983.
Generic diagnosis.- A phacopid with anterior opening left between dorsally archedcephalic and pygidial extremities and withshort cephalic and pygidial marginal spines.
Anterior cephalic doublure gently concave
dorsally inside vincular furrow, which isinterrupted behind between first pair of
cephalic marginal spines. Most anterior
pygidial marginal spine represented by broad(trans.) subrectangular lateral process; eachof subsequent ones by spinule.
Discussion.- Rhinophacops, gen. nov. canbe readily distinguished from all other members of the family Phacopidae by having ananterior opening during enrollment (paired
photographs shown in Figures 2 - Ic, 3b;
1Od, 14). Rhinophacops has a common
ancestor with Echinophacops Zhou, 1983
based on E. mirabilis Zhou from theZhusileng Formation. They share the following characters: (I) extremely depressedglabellae with wedge-shaped lateral profile,(2) completely reduced 2p lateral glabellar
furrows, (3) relatively posteriorly situated 3p
lateral glabellar furrows, (4) reduced (sag.)median part of Ip glabellar lobe whichalmost coalesces into the composite glabellarlobe, (5) small, low lateral nodes of Ip
glabellar lobe, (6) unnotched lateral vincularfurrows, (7) proportionally elongate (sag.),
multi segmented pygidia with marginal spines
developed as distal prolongations of the pleural ribs, (8) deep pleural furrows, (9) lack of
the interpleural furrow, (10) cephalic andpygidial marginal spines which interlocked

Figure 1. Localities
schizoloma (Zhou, 1983).

of Rhinophacops

361

with each other so as to provide an efficientfastening at the completion of enrollment,(II) a tendency of a gap to be left between
the cephalon and pygidium.
Echinophacops differs from Rhinophacops
in not produced anterior opening and much
more developed inversely cephalic marginal
spines as the anterior vincular furrow, whichis completely reduced. The pygidial marginal spines in the former genus are moredeveloped than those of the latter, and theanterior cephalic doublure is not concavewith a pair of protuberances.
Distribution.- The Upper Emsian Zhusileng Formation of western Inner Mongolia
and the Na Member of the Nakazato Formation of Northeast Japan.

Rhinophacops schizoloma (Zhou, 1983)
Figures 2-1-7

1983

Echinophacops schizoloma Zhou, p. 646-648,
pI. 2, figs. 2-16, text-fig. 3.

Description.- Glabella subpentagonal in
outline, wedge-shaped in lateral profile, withshort spines on its anterior margin. Glabellar marginal spines directed outwardly andupwardly; the most anterior three (median
unpaired and first pair counted from thefront) much more prominent than the remainders, of which only second pair is usuallysomewhat more prominent than glabellar
tubercles. I p glabellar furrow transverse anddeep at apodeme but turning forwards andfading away very rapidly medially. 2p lateral glabellar furrow completely reduced. 3p
lightly incised, biparted; inner part situatedat about posterior one third of glabellar
length (sag.), nearly transverse to slightly
convex forwards; outer part almost parallelto axial furrow, never reaching axial furrow.
Ip glabellar lobe triparted; lateral node
small, low, transverse; median part reduced
to two tubercles, coalescing into composite
glabell~r lobe medially.
Anterior and lat-

362

A tsushi Kaneko

894.

A new Trilobite genus

eral cephalic margins bearing eight pairs ofshort cone-like spines, which are directed
outwardly and ventrally; first to fourth pairs
more prominent than sixth to seventh pairs
but less prominent than fifth pair, opposite
inwardly indented portion of inner edge ofvincular furrow. Antero-medial portion ofanterior border furrow developed as a weaktransverse incision, which draws a boundary
between ventral base of the most anterior andprominent trio of glabellar marginal spines
and transverse, very slight swelling between
first pair of cephalic marginal spines representing vestigal anterior border; theremainder portion short (exsag.), shallow andindistinct. Occipital ring highly archedtransversely, about a half as wide (trans.) as
glabella, rising steeply from occipital furrow
and then becoming gentler posteriorly insagittal section; lateral portion semi-isolatedby broad (trans.) anterior incision and by
narrower (trans.), more lateral posterior incision. Occipital furrow deep, U-shaped insagittal section, long (sag. and exsag.) behind
median part of lp glabellar lobe but shortening (exsag.) at apodeme. Axial furrow very
narrow (trans.) and shallowest at occipitalring, becoming broader (tran.) and more
profound between occipital and 1p glabellar
furrows; in front of lp glabellar furrow,axial furrow diverging anteriorly at an angle
30 to 40 degrees from sagittal line, runningstraight, narrowing (trans.) rapidly and shall-363

owing slightly, and then sloping down gently
anteriorly, and U-shaped in cross section.
Facial suture not distinguishable in front ofeye; E almost at posterior border furrow;lateral to E, suture running slightly forward,
curving gently backward on lateral border;
w at approximate level of E. Palpebral lobe
moderate in width (trans.), subreniform inoutline, a little lower than glabella, widest aty; outer palpebral rim defined by very weak
furrow which runs in parallel with palpebral
margin. Palpebral area inflated as highly as
palpebral lobe, flat-topped, delimited bypalpebral furrow abaxially, with subverticaladaxial and posterior slopes. Palpebral furrow not so narrow (trans.), curving outwards
and backwards and cutting up somewhat
deeply from axial furrow, becoming slightly
shallower as far as level of 0, afterthere running in parallel with axial furrow and cutting
down deeply and steeply. Eye mediumsized; visual surface steeply inclined abaxially at 70 to 80 degrees, with 20 dorso-ventral
files, each of which contains up to 6 lenses;
lens distribution is shown in Table I. Vertical concave area well extended beneath visualsurface of eye to lateral border furrow, whichis represented by very broad (exsag.), weak
concavity of gena which is inclined steeply
outwardly. Postocular area completely
reduced. Lateral border represented by moreor less narrow (trans.), slight convexity along
lateral cephalic margin, which widens poster-+- Figure 2. Rhinophacops schizoloma (Zhou, 1983). 1-7, Material from the Nakazato Formation(specimens figure-d are all represented by rubber cast). la-c, Cephalon, JPIOOOI ; a, dorsal view, X 2.0;b, right lateral view, X 2.65; c, anterior view, X 3.8. 2a, Three cephala (A, Band C) and one pygidium (D)contained in a slab together with a dechenelid pygidium (E); cephalon (A), JPI0002, X 1.8. 2b, counterpart of 2a, X 1.8. 3a-d, Pygidium, JP 10003, X 2; a, dorsal view; b, posterior view; c, right lateral view;d, dorso-Iateral view showing marginal spines. 4, Cephal on, JP10004, x2.0; ventral view. 5, Cephalon,
JP10005, x2.0; dorsal view showing well preserved Ip glabellar lobe. 6, 7, Right and left eyes, JPI0006,
PJ 10007, X 5.0. 8-14, Material from Inner Mongolia. 8, Cephalon, Tr-239 (Zhou, 1983, pI. 2, fig. 5),
dorsal view, X 1.5; 9, cephalon, Tr-237 (Ibid., pI. 2, fig. 3), left lateral view, x4.0; lOa-d, cephalon, Tr240 (Ibid., pI. 2, figs. 7-8); a, dorsal view, X 2.0; b, left lateral view, X 2.0; c, enlargement of left eye
shown in b, X 5.3; d, anterior view, X 2.23. 11, Cephalon, Tr-242 (Ibid., pI. 2, fig. II), ventral view, X 2.
12, Cephalon, Tr-243 (Ibid., pI. 2, fig. 12), ventral view, x2. 13a-c, Pygidium, holotype, Tr-244 (Ibid., pI.
2, figs. 13-15), x2.0; a, dorsal view; b, ventral view; c, left lateral view. 14, Pygidium, Tr-245 (Ibid., pI.
2, fig. 16), posterior view, X 2.43. Two sets of photographs each showing an anterior opening (Ie and 3b;
IOd and 14. (Photos, la-7, IOd, 14 by Kaneko; 8-10c, 11-13c by Zhou Zhi-qiang).

A tsushi Kaneko

364
Table I.

Lens distribution of Rhinophacops schizoloma (Zhou, 1983).
number of lenses per file
(front to rear)

specimen
Northeast
Japan
Inner
Mongolia

Figure 1-6

345

566

555

Figure 1-7

355

565

••
555

Figure lOb

355

565

655

total

maximum number
per file
6

•••
•••
555

555

554

32

93

555

554

42

94

555

545

544

42

93

555

6

• probable original number

iorly to meet posterior border. Posteriorborder furrow deep, V-shaped in sagittal
section, moderate in length (exsag.) at axial
furrow but progressively lengthening (exsag.)abaxially, and then gently curving forwards
to meet lateral border furrow. Posteriorborder short (exsag.) and evenly rounded(exsag.) adaxially; outside fulcrum posteriorborder curving downwards and becoming
progressively flattened and elongate (exsag.).
Genal angle well-rounded, with a short spine.
Anterior doublure about a half as long (sag.)as cephalon; inside inner edge of vincularfurrow anterior doublure broadly depressed
dorsally, with steep slope which is narrow(trans.) opposite first cephalic marginal spine
but progressively increases in width posteriorly because depressed portion inside the slope
inclined dorsally posteriorly; medial portion
with weak, broad crescent-shaped concavity
along hypostomal suture. Medial part ofhypostomal suture slightly convex posteriorly
in ventral view, weakly arched in posteriorview. Vincular furrow interrupted behind
between first pair of cephalic marginal spines,
without lateral notches: inner edge somewhat sharp: inner wall of moderate height
posterolaterally, but rapidly decreasing inheight opposite between fifth and fourth
cephalic marginal spines, reduced to weakridge anterolaterally; inner wall moderately
indented opposite at abaxial extremity ofhypostomal suture. Hypostome unknown.
Thoracic axial ring with incision from rear,which does not separate lateral axial node.
Number of thoracic segments unknown.

Pygidium elongate (sag.) triangular in general outline, moderately convex, with upward
deflection of posterior extremity which is also
embayed forwards in dorsal view and with
marginal spines in prolongation of pleuralribs. Axis slender, highly arched, not constricted, comprising an articulating half-ring,
eleven rings and a terminal piece; each ringwith axial node on sagittal line; first ring
furrow deepest and longest (sag.); subsequent furrows becoming progressively shallower and shorter (sag.) posteriorly. Pleuralregion with nine ribs each developing amarginal spine as its distal prolongation; thefirst one represented by a broad subrectangular lateral process; each of the rest by aspinule. Pleural furrow short (exsag.), Vshaped in exsagittal section, moderate indepth; second furrow deepest; subsequentones becoming progressively shallower posteriorly; first two furrows fading away justbefore reaching margin; third to ninth furrows flexed backwards before reaching margin, and then continuing to troughs between
marginal spines. Interpleural furrow absent.
Doublure consisting of very narrow (trans.)
outer band just inside marginal spines andmuch wider, very steep inner band except its
most anterior portion on lateral process fromthe first pleural rib, where the outer band
somewhat widens and curves strongly outwardly and then turns rapidly forwards andnarrows; the inner band becomes gentler andslightly bulges inwardly at the posterior baseof process and then becomes much moregentler at its posterolateral corner.

894.

A new Trilobite genus

Glabella covered with coarse tubercles andrest of body apparently smooth.
Remarks.- The present Nakazato specimens are quite identical with Zhou's Inner
Mongolian ones in the shape, length, number,position and direction of cephalic, glabellar
and pygidial marginal spines, the structures ofglabella and cephalic doublure, the outline,
degree of deflection of posterior extremity andthe number of pleural ribs of pygidium. The
distribution of eye lenses, in which the intraspecific variations are usually recognized in
the family Phacopidae, is also identical.
Slight differences are only recognized in
tubercles on the palpebral area and apparent
persistence of the most anterior portion of thevinicular furrow in Zhou's specimens.
Occurrence .- Fine- to coarse-grainedsandstone beds of the N g Member of the
Nakazato Formation exposed along the riverside of a small tributary branching from the
middle course of the Higuchi-zawa Valley,
Hikoroichi-cho, Ofuna to City, Iwate Prefecture.
Repository.- All specimens came from the
Nakazato Formation are housed in the Institute of Geology and Mineralogy, Faculty of
Science, Kyoto University with prefix lP.
Higuchi-zawa

llm I=l iR, Hikoroichi*~~, Zhusileng

365

References cited
Copper, P., Tazawa, J., Mori, K. and Kato, M., 1982:
Atrypa (Devonian Brachiopoda) from Japan.
Trans. Proc. Palaeont. Soc. Japan, N.S., no.
127, p. 368-374, pI. 59.
Kaneko, A., 1984; A Middle Devonian trilobite
fauna from the Kitakami Mountains, Northeast
Japan -I. The Lichidae. Ibid., no. 136, p.474491, pis. 87-89.
- - 1985: Ditto- II. The Calymenidae. Ibid.,
no. 138, p. 94-110, pis. 14-16.
Kobayashi, T. and Hamada, T., 1977, Devonian
trilobites of Japan - In comparison with Asian,Pacific and other faunas. Palaeont. Soc. Japan,
Spec. Paper, no. 20, p. 1-202, pis. 1-13.
Minato, M., Hunahashi, M., Watanabe, J. and Kato,
M. (ed.), 1979: The Abean Orogeny, Variscan
geohistory of northern Japan, 427p., Tokai
Univ. Press, Tokyo.
Murata, M., 1972: Some Devonian corals from the
Takamori-yama area, Kitakami Massif, Northeast Honshu, Japan. Saito Ho-on Kai Museum
Res. Bull., no. 41, p. 17-27, pis. 2, 3.
Zhan, Y. and Ruan, Y., 1983: Discovery of a
Devonian ammonoid species from Ejin Banner,
western Inner Mongolia. Acta Palaeont.
Sinica, vol. 22, p.1I9-121.
Zhou, Z., 1983: Echinophacops, a new genus of thesubfamily Phacopinae. Ibid., vol. 22, p.642650, pis. I, 2.

B i!flm, Iwate ;'6:-'f, Nakazato

q,.m., Ofuna to

J;lcM*'-Io-=~!R.Q)ma Rhinophacops: pi;] -{:-:/::t ,vQ)l::$:z. A A*It Zhusileng Formation (J;lcM*'-Ijl.) il' I?flH!r ~.h t.: Echinophacops schizoloma Zhou, 1983 ~m~:fl c L -C ~ a Rhino-

phacops ~~P@\"t Go mafi7t~~c~~j6A.,t':l~iHc,'W:n~C~A.,t':liJi:$Q)J't;:flIij'&lf£~fN

c, 'W:nK.<~hl::~~t.:MfN • • cQ)~K~I=l$~%."tGo ~Q)maQ)m~:flK~
5E"'C' ~ G~*il'~tl::J1Jj\Bq,.m.~ N3 $~il' I?~ I? .ht.:Q) ""(:'~*Dl~c~i(; L t.:o tt. 'iQ, q, .m.~fi~.hi"'C'~f*c L-Cq,$T;f-:/*~C;f:§~"tG c~*-I?.h-C ~t.:..il;, 'Y'tt. < c ~ N3 $~Q)-$~T$T;f-:/*.l::$Q)l::$:z.AA*ltKn~~.hG~fi~~"'C'-c~t.:o it.:~Q)15
tt.~i!!&l¥.Jtt.:flil;pI;] -{:- :/ :2" 'v c ~tl::J1Jj\Bil' 1?g[1±l"t G ~ Ul, jilijj\B~Q)tl1:J~lIitB:f!!.1R ~~~"tG 5 *- "'C'£~"'C'ibGo

3llr ~

Trans. Proc. Palaeont. Soc. Japan, N.S., No. 157, pp. 366-381, 10 Figs., April 30, 1990

895.

GIGANTIC AMMONITES FROM THE CRETACEOUS FUTABAGROUP OF FUKUSHIMA PREFECTURE*
T ATSURO MATSUMOTO
c/o Department of Geology, Kyushu University 33, Fukuoka 812

MAMORU NEMOTO
Sakurada 95, Shimo-Asamigawa, Hirono, Futaba-gun, Fukushima 979-04
and

CHISA TO SUZUKI
Nishi 2-6-3, Yotsukura, Iwaki City 979-02

Abstract. Ten large or gigantic ammonite specimens were obtained by a number of
persons from the Upper Cretaceous Futaba Group in the coastal area of Fukushima
Prefecture (Northeast Japan). They are more or less incompletely preserved, but complementary with one another in showing characteristic features, which allow us to conclude thatthey are macroconchs of Mesopuzosia yubarensis (limbo). They can supplement in 'somerespects the knowledge of this species, which has been recently described on the material from
Hokkaido. They occur sporadically in a limited part (silty fine-grained sandstone andsandy mudstone) of the Coniacian Ashizawa Formation, i.e. the lower unit of the tripartite
Futaba Group. For some reasons no microconch of this species has been found from thesame part.
Key words.
Group.

Mesopuzosia yubarensis, macroconch, microconch, Coniacian, Futaba

and Fossils (lMNH) except for one at the
Yotsukura Museum of History (YH). After
preliminary investigations by several members of the Taira Geologic Society (Yanagisawa et al., 1973; Hashimoto et al., 1981), T.
M. was invited by the Board of Education tocooperate with them to complete thepalaeontological study. Among a number of
persons concerned with these gigantic ammonites, M.N. and C.S. were selected by Ichiro
Yanagisawa, the Chief of the Society, toaccomplish this research work with T.M. M.
N. is especially responsible for the field work
to make clear the stratigraphic occurrence of
the ammonites.

Introduction

Since 1963 large or huge ammonites havebeen found from the Upper Cretaceous
Futaba Group of Fukushima Prefecture.
They numbered ten at the date (1982) when
one of us (T.M.) had keen interests in gigantic
ammonites. Some of them are so great that agroup of persons organized by the Iwaki City
Board of Education (IBE) worked for the
excavation. Most of them were brought to aworkshop for preparation and eventuallyregistered at the Iwaki City Museum of Coal
'Received April 17, 1989; accepted December 20,
1989
366

895.

Gigantic ammonites from the Cretaceous

Palaeontological description

Mesopuzosia yubarensis (Jimbo)
Figures \-8

Synonymy. - See Matsumoto, 1988, p. 68.
Material. - The following ten specimens,in the order of date of acquisition, indicatedby the register number at the repository (abbreviated), proprietary (abbr.), finder, year offinding and brief remarks on the state ofpreservation:(1) IMNHP402001, IBE, Teruo Sato (asstudent of Chiba University), 1963, fragmentary piece of middle-aged whorl (Figure 8) ;(2) IMNHP402002, IBE, Tamiye Yoshida(deceased; donated by Mrs. Yuriko Y oshida to IBE, 1965, secondarily deformed anderoded inner whorls with a piece of outerwhorl; (3) YH. PI, YAH, anonym (donatedby way of Tadashi Suzuki), 1967, very incomplete four whorls up to the last septum; (4)IMNHP 402003, IBE, Nagayuki Nemoto (asstudent of Iwaki High School), 1970, nearly
entire shell but for several damaged portionsof outer whorl (Figure 7); (5) IMNHP402004, IBE, Kin'ichi Nabana, 1973,
nearly entire shell embedded in rock matrix(Figures 1,2); (6) IMNHP402005, IBE,
Toyokazu Yoshida (as school boy), 1974,
less deformed phragmocone, without bodychamber (Figure 3); (7) No number, C.
Suzuki's house, private for the present,
Chisato Suzuki, 1979, entire phragmocone,
somewhat deformed, with secondarily sharpened venter (Figure 4); (8) IMNHP402006,
IBE, Kazuo Hashimoto, Takeo Matsumoto,Tokiji N.agata and Chisato Suzuki, 1980,
nearly entire shell, but for so much eroded
body chamber that even the overlapped partof the next inner whorl is exposed (Figure 6) ;(9) IMNHP402007, IBE, Yoshiki Koda,
1981, badly damaged, and secondarily compressed specimen, whose preserved fraction ofouter whorl is still septate; (10) IMNHP
402008, IBE, Y oshiki Koda, 1981, secondarily

367

flattened, large but wholly septate specimen.
The repositories are Iwaki City Museum of
Coal and Fossils (IMNH) (Iwaki-shi
Sekitan-Kaseki-Kan in Japanese) and Yotsukura Museum of History (YH) (Yotsukura
Shigaku-Kan in Japanese). The official proprietaries which correspond to the above two
are Iwaki City Board of Education (lBE) andthe Yotsukura Association of History(Y AH), respectively.
The technical terms in this paper are currently used ones. Their abbreviated expressions are the same as those in the recently
published monograph of the Puzosiidae (Matsumoto, 1988), being briefly explained at thebottom of Table 1. An arrow in a figure
indicates the position of the last suture (LS).
Dimensions. - See Table I.
Observations. - Although the ten specimens are more or less incomplete and secondarily compressed, they are complementarywith one another to know the characters.
Our observations of individual specimens are
given below.
The 5th specimen (Figure I), among others,
is a less deformed, nearly entire shell, but for
the lost last portion (about 20·) which shouldhave shown an apertural margin. Its diameter is 790 mm at the preserved end (E in
Figure 2) and estimated at 825 mm at theinferred peristome. The body chamber is
220· in spiral length and was originally 240·.
It has more convex flanks and a morerounded umbilical shoulder and a moderately
rounded (in stead of narrowly arched) venter,as compared with the septate whorls. The
surface of the shell on the body chamber isnearly smooth and blunt radial elevations aredisposed at each 30· (on an average) on the
inner part of flank, fading away outward.
The last two of them are broad, giving rise topartial inflation of the flank. In the earliest
part of body chamber and the preceding latepart of phragmocone (altogether 180·), narrower radial elevations are discernible on the
inner flank at each 20· or so. Some of them
are extended to the outer flank, showing for-

Tatsuro Matsumoto et al.

368
Table I.
Specimen

Dimensions of measurable specimens.

DU- 540 (I)

207 (.38)(I) IMNHP402001, E(2) IMNHP402002, LS
IMNHP402002, LS + 30'(3) YH. PI, last 4th(4) IMNHP402003, E(5) IMNHP402004, E
IMNHP402004, LS + 10'(6) IMNHP402005, E(7) IMNHP402006, E(8) IMNHP402007, E

H

B

HjB

156

77

0.49

h

Hjh

lnv.

Max.

0.52
~

208
101
81
45
605 (I)
229 (.38) 220 (.36) - 100 (.17)
287 (.36) 295 (.37)
790 (I)
198 (.35)
131 (.23)
201 (.36)- 558 (I)190 (.35) -110 (.20)
540 (I) -198 (.37)
225 (.37) 240 (.39) -125 (.20)
615 (I)- 1056 (I) -392 (.37) -392 (.37)

820

0.49
0.55
0.45

156
1.41
0.48 ~ 800
1.420.51 - 825
208
-159
-1.25
0.66
0.58 -152 -1.25 -0.5 ~ 820
0.52
1621.48 -0.5 ~1200
1.44
-272
0.55 -1200

D=diameter, U=width of umbilicus, H=whorl-height, B=whorl-breadth, h=whorl-height at a point
180' adapically from H, Inv.=degree of involution (overlapped part/whorl-height of the next inner
whorl), Max. = estimated maximum diameter at the end ofreconstructed body chamber, - = approximate
or restored; Measured point: LS = last septum, LS + 3~' = 30' adorally from LS, E = at or near thepreserved end. Measurements are in mm.

ward projection and can be interpreted aspersisting periodic flares. The inner whorls
have, in addition to the periodic constrictions
and flares, numerous ribs of unequal length,
many of which reach the umbilical margin.
About a half (0.51 in height) of the inner
whorl is overlapped by the outer whorl. The
ratio of whorl expansion is moderate (H/h=1.42) and the width of umbilicus is also
moderate (U /D = 0.36).
The 6th specimen (Figure 3), with D = 540
mm at E, is less deformed but wholly septate,
representing a late stage of a phragmocone.
Its whorl-section at a late stage (Figure SA) is
suboval, with B/H=0.58 and more slender at
earlier stages. It has a narrowly arched
venter and gently convex, instead of plainly
flat, flanks. The umbilicus is of moderate
width (U/D=0.37), encircled by a subangular to abruptly subrounded shoulder. The
inner whorl has numerous, fine ribs, whichreach or nearly reach the umbilical margin,
and constrictions with flares of moderate frequency. Numerous, projected, fine ribs persist on to the ventral part of an early half ofthe preserved outer whorl, fading away later,whereas blunt, radial elevations develop on
the inner flank roughly at each 30' and tend

to broaden in the otherwise smooth late part.
These radial elevations are so blunt that they
may not be well shown in the photograph of
Figure 3.
The 7th specimen (Figures 4A, B), with
D=615 mm, is also wholly septate, exhibiting
finely and deeply incised sutures on the outerwhorl. Therefore, it looks very good in lateral view but actually it is distorted, showing
a secondarily sharpened venter and deformed
outline of whorl-section, which can be restored to a narrowly suboval shape (Figures 5B,
C). Although the outer whorl looks smooth,it has blunt radial elevations at intervals(roughly at each 20') on the inner flank. The
radial elevations must have been more widely
spaced (e.g. at each 30°) and broadened or
inflated on the missing body chamber as in
the case of the 5th specimen. On the ventral
part, which is secondarily sharpened, numerous, projected riblets remain, as those of theearly half of the outer whorl in the 6th specimen. Incidentally, several bivalves stick tothe shell of outer whorl. Numerous, somewhat prorsiradiate, long ribs can be seen on
the inner half of the inner whorls which areexposed in the umbilicus. They are distinctly impressed on the external mould which is895.

Gigantic ammonites from the Cretaceous

Figure 1. Mesopuzosia yubarensis (limbo), macrocon~h. Lateral view of the 5th
IMNHP402004, from Ashizawa. Arrow: position of the last septum . Scale bar = 100 mm.

369

specimen,Tatsuro Matsumoto et al.

370

"

E

.....

., ..'
....
",6

'1'.

••

'.::: '::, '.'..,!~.

<1.:J.~.f'~").

. . ····0.-:

.,

,·if;

~l:;

..,

1.:\
'1

Figure 2. Mesopuzosia yubarensis (Jimbo), macroconch. Schematic drawing of IMNHP402004 to
supplement Figure I, with whorl-section (Q) at the beginning of the body chamber. Bar= 100 mm.

preserved in the calcareous nodule of silty
sandstone. This heavy nodule was carefully
brought to the Museum by T. Suzuki. The
ribs should curve forward on the outer half of
the inner whorl, although that part is overlapped by the outer whorl in this specimen.
The last mentioned is evidenced by the 8th
specimen (Figure 6), which exhibits clearlynumerous, forward curved ribs on the outerhalf of the next inner whorl. The outerwhorl of this specimen, which includes themain part of the body chamber, is so muchbroken that the adequate cleaning has
exposed the overlapped outer part of the next
inner whorl. The shelly material is preserved on the originally overlapped part of theinner whorl. The diameter of this secondarily compressed specimen is 1050 mm at thepreserved end and would be nearly 1200 mm
at the inferred peristome.
The 4th specimen (Figure 7), with D = 605
mm at about the middle of the body chamber

895.

Gigantic ammonites from the Cretaceous

371

E

Figure 3. Mesopuzosia yubarensis (limbo) , macroconch. Lateral (A) and ventral (B) views of the 6th
specimen , IMNHP402005, from Ashi zawa. Sca le bar = 100 mm.

(E in Figure 7, 110' adorally from LS) , issomewhat crushed and secondarily compressed . It shows, however, the mode ofribbing ill the main part of the phragmocone
and the change of ornamentation from thelast part (about 90' ) of the septate whorl tothe body-chamber. At the point with H =150 mm , i .e. 120' prior to the last septum,
there is a narrow but distinct constriction
with an accompanied narrow flare . lt issomewhat prorsiradiate on the inner half offlank and curved considerably forward on theouter half, showing a ventral projection. Up
to the point with H = 165 mm , i.e. somewhat
ahead of that con striction, there are numerous, crowded, fine ribs which run parallel tothe constrictions and may be occasionallygently sigmoidal. They are mostly long, reaching the umbilical margin , but some areintercalary. The periodic constrictions withweak flares are discernible on inner whorls, as
far as preservation is favourable. In the lastpart of the septate whorl the ribs becomecoarser and are separated by wider inter-372

Tatsuro Matsumoto et al.

aFigure 4. Mesopuzosia y ubarensis (Jimbo), macroconch. Lateral (A) and ventral (B) views of C. Suzuki 's
specimen , found loose (but proba bl y deri ved from the Ashi zawa Formation) at Momoki zawa. Venter isseco nd aril y sharpened. Scale bar = 50 mm. Dots in A indicate the position of blunt radial bulges.

spaces. At the beginning of the body chamber thick but blunt radial elevations appear,with interspaces somewhat wider than theelevations. On the main part of the bodychamber the radial elev ations become broader
and separated by much wider interspaces(roughly at each 30°), fading away outward.
They may be still broader and give inflation
as in the 5th specimen in the late part of the

body chamber, but this part is not preservedin the 4th specimen .
The 1st specimen (Figure 8) is a fragmentary piece of a n inner whorl , with H = 156 mm
and B = 77 mm . Its outer halfis well preserved because it was overlapped by a large outerwhorl , showing numerous, projected rib s
where shell is preserved, and finely a nd deeply
inci sed sutures (E and L) where shell is taken

895.

Gigantic ammonites from the Cretaceous/..- .....

I/

,

'"\

I

\

I

'

I
I

\

,,

\

,

I

I

.... ~,\

I\'" -1I

,,
I

A

B

,

\

,

\r ,I

,,
I

C

"'

Figure 5. Mesopuzosia yubarensis (Jimbo),
macroconch . Whorl-sections. A : IMNHP402005
at E in Figure 3. B: Chisato Suzuki 's specimen at
Q in Figure 4 (seco ndarily distorted) . C: Ditto,
restored. Scale bar == 30 mm.

373

off. Its inner ha lf is much eroded, beca use of
the unprotected condition. The sutural elements are so much eroded that their detail s
are not preserved, but one can see the generalconfiguration of nearly erect U2 and ob li quely descending auxiliaries (i .e. U3 = S).
Furthermore, the internal suture is exposedon the dorsal part of this isolated speci men ,show ing deep I (antisiphonal lobe) , erect U I(by T.M.'s indication) and ob liqu ely descending auxiliaries, i. e. suspen sive U 3 = S by
T.M.'s way of indication (see Matsumoto ,1954, figs. 2, 3). This specimen is higher thanbroad, with 8 j H =0.49 and slender or elon gated suboval in whorl-section , having gently
convex (i nstead of plainly flat) flank s and anarrowly arched venter.

Figure 6. Mesopllzosia yubarensis (Jimbo), macroconch. Lateral view of the 8th specimen ,IMNHP402006, from Ashizawa. The o uter whorl is so much broken that the next inner whorl is whol ly
exposed. Sca le bar= 100 mm.

374

Tatsuro Matsumoto et al.

The 2nd specimen is badly preserved, but
the available piece of outer whorl consists of
the last portion of phragmocone and the
beginning of the body chamber, whose dimensions in somewhat secondarily deformed state
are H=208 mm, B= 101 mm, and B/ H = 0.49
and the worl-section is generally similar tothat of the first specimen in having gently
convex Ranks and a narrowly arched venter.
This piece of whorl , roughly 65" in length, is
an internal mould but has three weak radial
elevations at each 20° on the inner half ofRank. The slightly abraded suture is disti nctly exposed on the right side showi ng
large, asymmetrically tripartite L, but is mucheroded on the left side. The diameter of a
restored outline of the shell is roughly 540
mm at LS. This is nearly the same as that of

the 6th specimen.
The 3rd specimen consists of very incomplete pieces of overlapping 4 whorls, of which
the outermost one has LS. It shows generally the change of characters mentioned
above. The last third whorl is less deformed,
whose outline in cross-section is a slender
egg-shape, with H = 81 mm , B= -45 mm , and
B/ H = 0.56.
The 9th and 10th specimens are still septate
at the preserved end but huge, about 600 mm
and 660 mm, respectively. They are secondarily crushed and only the left side is preserved.
Diagnostic characters.- Summarizing theforegoing observations, the diagnostic characters may be written as follows:
The shell is gigantic, normally somewhat

Figure 7. Mesopuzosia yubarensis (limbo), macroconch.
IMNHP402003, from the north of Ohhisa. Scale bar = 100 mm.

Lateralviewof the 4th

specimen,

895.

Gigantic ammonites from the Cretaceous

375

Figure 8. Mesopuzosia yubarensis (limbo). Lateral (A). ventral (B) and dorsal (C) views of the 1st
specimen, IMNHP402001 , fragmentary inner whorl of a large shell , from the north ofOhhisa. Scale bar =50mm.

over 820 mm at the end of the body chamber,attaining 1200 mm or more in larger examples. The body chamber occupies 240 inspiral angle, nearly smooth on the surface ofshell but for blunt major radial elevations at
wide intervals (at each 30 on an average),00which develop on the inner part of flank ,broadening but fading away outward. The
elevations on the late part are generally
greater than those on the early part, giving
rise to partial inflation of the body chamber.
The body chamber is generally oval in376

Tatsuro Matsumoto et af.

section, showing a moderately rounded
venter, fairly convex flanks and roundedshoulders on the umbilical margin. The
outer whorl overlaps about a half (in H) of
the next inner whorl and the rate of whorl
expansion is moderate or rather low. Hence,
the umbilicus is moderately wide.
The inner whorls are much higher thanbroad, with narrowly sub oval cross-section,
showing narrowly arched venter, gently convex (instead of plainly flat) flanks, abruptly
subrounded umbilical shoulders and low but
nearly vertical umbilical walls. They haveperiodic, weak constrictions, with associatednarrow flares, and numerous, dense and fineribs, which are mostly long, reaching theumbilical margin, with some intercalated
shorter ones, subradial or slightly prorsiradiate or occasionally gently flexuous on the
inner part of flank and curved forward on theouter part, showing marked ventral projection. The rate of whorl expansion is moderate, involution nearly a half and umbilicus ofmoderate width.
The last part of the phragmocone, that may
form the outer whorl with the body chamber,shows a gradual change in the outline ofwhorl-section and ornamentation. The fineribs remain as projected riblets on the ventral
part and the periodic flares may persist to
some extent, but soon these ornaments disappear and are replaced by blunt radialbulges on the inner part of flank, which arenarrower and somewhat more frequent thanthose on the body chamber.
The sutures are of typical Puzosia pattern,showing the disposition of E, L, U2, U3 = S,
UI, I (by T.M.'s formula; see Matsumoto,
1954, figs. 2-4), large and asymmetrically tripartite L, and much intricate, fine and deep
incisions of the elements.
Comparison and discussion.- The above
described characters match very well those of
macroconchs of Mesopuzosia yubarensis(limbo), which has been recently redefined on
the material from Hokkaido (Matsumoto,
Kawashita and Takahashi in Matsumoto

1988, p. 68-76). Examples of macroconchs
which preserve the body chamber were notsufficiently numerous in the Hokkaido material. Now the gigantic specimens from the
Futaba Group do supplement that weak
point, in showing the characters of both theinner and outer whorls, although some ofthem are secondarily compressed.
The largest specimen from Hokkaido(ditto, fig. 27) is estimated at about 1300 mm
in the diameter of the restored entire shell.
This is nearly the same dimension as that of
the maximum diameter in the restored outlineof the 7th and 8th specimens from the Futaba
Group (see Table 1). There is, however,some extent of variation in the size of macroconchs. The diameter of 825 mm or soseems to be more common in the Futaba...... _lAO-57'.,.-.,.,'-',FUTABA-GUN~~_\""""\\ ......

OHHISA~~,[t
B ••......•

37"10'MOMOKIZAWA

Figure 9. Map showing localities of the gigantic ammonites numbered in the order of acquisition;solid circle in situ; cross: loose. Inset at the upper
right corner is the index map, in which outcropping
area of the Cretaceous Futaba Group is dotted.
Solid square: town - - Hn: Hirono, Hs: Hisanohama, Yt: Yotsukura. Chain: administrative
boundary of Futaba-gun (north) and Iwaki City
(south).

895.

Gigantic ammonites from the Cretaceous

material.
For some reasons, no microconch has beenobtained from the macroconch bearing bedsof the Futaba Group. A small puzosiid
specimen was acquired by Kazuo Hashimotofrom the rock close to the bed whichcontained the 9th and 10th specimens. It is
not M. yubarensis, because it has coarser ribs
which do not show strong ventral projection.
It may be juvenile Pachydesmoceras cf. mihoense (Matsumoto).
Occurrence.- The localities of the described specimens, except for the 3rd without
record, are shown in a map of Figure 9.
They are north of Ohhisa (1,4), around
Ashizawa (2, 5, 6, 9, 10) and northeastern partof Momokizawa (7 and 8, of which 7 isloose), all in the northern part of Iwaki City
by the recent administrative division. In
addition to the natural outcrops along theRiver Ohhisa [sometimes called Ohbisa (e.g.
the 1st and the 4th specimens), the recent
public works to construct a new road andsome other private engineering works havebrought new exposures of the Cretaceous
strata, from which the described gigantic
ammonites were found. Stratigraphicallythese ammonites can be allocated roughly at
two levels in the middle member of the
Ashizawa Formation, which itself forms thelower unit of the tripartite Futaba Group(Saito, 1960, 1961) or Futaba Beds in theoriginal work of Tokunaga and Shimizu(1926). A bed of orange coloured, probably
tuffaceous, coarse- to medium-grained sandstone in the upper part of the Ashizawa
Formation is a key to correlate the strata ofseparated outcrops. The described gigantic
ammonites occur in the muddy fine-grainedsandstone or sandy siltstone below this key
bed. Bioturbation is observable here andthere, whereas fine lamination is distinct inother parts. Calcareous nodules arecontained at various levels and some of thegigantic ammonites (e.g. the 5th, 6th and 7th
specimens) are in them, whereas others areembedded directly in the country rock and377

compressed secondarily.
Inoceramus uwajimensis Yehara occurs
fairly abundantly at various levels in the
Ashizawa Formation. Several specimens ofI. uwajimensis and I. mihoensis Matsumotowere obtained and brought to the Museumfrom the outcrop where the 9th and the 10th
gigantic ammonites were excavated. The
rock of this outcrop is referred to the higher
one of the two levels. A deformed nautiloid
specimen of Cymatoceras sp. was associatedwith the 2nd specimen, which is nearly thesame level as the 5th and the 6th specimens of
the giants. This level is the lower one of thetwo levels mentioned above. At this level asingle, somewhat secondarily deformed specimen of Forresteria (Forresteria) alluaudi(Boule, Lemoine et Thevenin) (Figure 10)
was once obtained by Mitsuo Kitago and is
now held in the Hirono-Machi Board of
Education. This ammonite species and theassociation of I. uwajimensis with I. mihoensis suggest the Middle Coniacian age of the
middle part of the Ashizawa Formation.
Further remarks

Macroconchs of ammonoids are currently
regarded as adult female shells (Lehmann,
1981). In many species of the Puzosiinae thebody chamber of a gigantic macroconch is
generally broader than its phragmocone aswell as its corresponding microconch (Matsumoto, 1988). This is well exemplified by M.
yubarensis. Furthermore, the body chamberof an adult macroconch of this species has
blunt radial elevations at wide intervals (e.g.
at each 30' on an average) on its otherwisesmooth shell-surface, and some of them in the
middle to late part of the body chamber are
broader or greater than others, giving rise topartial inflation of the flanks. Similar features seem to occur generally in other speciesof Mesopuzosia and Puzosia, as one of us(Matsumoto, 1988) has recently shown.
Incidentally, Matsumotoceras donlisteri van
Hoepe'n, 1968 (p. 157, pI. 1, fig. I ; text-fig.

Tatsuro Matsumoto et al.

378la), from South Africa, may be also such an
example. Anyhow, the general broadeningof the body chamber in a large macroconch
may imply an enlargement of the body whichmust be related to the remarkable growth of
the genital and other organs so that the adultfemale may have exhibited .especially vigorous activity in life. The periodic inflationsof the body chamber described above suggest
the extra capacity afforded to the mantle.
One can presume, as a working hypothesis,that adult females of these kinds of ammonite
species may have been periodically active informing and then laying egg-capsules. To
find fossil egg-capsules of appropriate size
would be required to verify this speculativeinterpretation.
We agree with Saito (1960, p. 112, fig. 2) inadmitting the lateral changes in the sedimentary facies and thickness of the Ashizawa
Formation. In the vicinity of Ashizawa,
muddy sediments prevail rather than gravels
and coarse-grained sands, representing probably the central part of the basin. Such anenvironment may have been favourable inshallowness and quietude for the adultfemales of M. yubarensis to lay egg-capsuleson some suitable substances at the bottom.
Should this assumption be warranted, themales of the same species would scarcely
come in there. The mating place must havebeen somewhere else.

Material. Thanks are extended to Professor
Ichiro Yanagisawa, Chief of the Taira Geologic Society, for his instructive support toour investigation. The Iwaki Educationaland Cultural Corporation took necessary
procedures in the excavation, transportationand triming of the fossil specimens. Mr.
Tadashi Suzuki, among others, helped us in
the laboratory works as a staff of the Corporation. Photographs of the gigantic ammonites were taken by Mr. Tomoyuki Matsumoto with the aid of Messrs. Tadashi Suzuki,
Yoshiki Koda and Keiichi Suzuki; those of
Forresteria by Dr. Masayuki Noda. Mr.
Toshimitsu Watanabe and Dr. Seiichi Toshimitsu kindly helped us in our stratigraphic
field work. Miss Akiko Murakami assisted
us in preparing the typescript, which was
improved with kind suggestions from Dr.
Ikuwo Obata and anonymous referees.
Appendix: An ammonite referable to
Forresteria from the Futaba GroupT. Matsumoto and M. NemotoThis is a concise systematic description ofan ammonite belonging to the genus Forresteria mentioned in the main text of this paper.

Acknowledgements

Family Collignoniceratidae Wrightet Wright, 1951
Subfamily Barroisiceratinae Basse, 1947
Genus Forresteria Reeside, 1932

We are much indebted to the authorities of
the Iwaki City Board of Education (Superintendent Mr. Mamoru Iijima), Iwaki City
Museum of Coal and Fossils (Director Mr.
Yasuo Goshogaki), Hirono-Machi Board of
Education (HBE) (Super-intendent Mr.
Katsumi Endo) and Yotsukura Museum ofHistory (Director Mr. Tokuji Honda) for
every facility which they afforded to thisstudy. We highly appreciate the finds ofscientifically valuable specimens by the persons whose names are recorded in the item

Type species.- Barroisiceras (Forresteria)
Jorresteri Reeside, 1932 (p. 14, original designation) [ = Forresteria alluaudi; (Boule,Lemoine et Thevenin, 1907)J (see Matsumoto, 1969, p.306).
Remarks.- In the original definition,
Reeside (1932, p. 14) proposed the subgenus
Forresteria for what he wrote in the same
page the group of Barroisiceras Jorresteri andfour species were assigned to this subgenericgroup. B. (F.) Jorresteri was one of them,
being indicated at their top. In other words,

895.

Gigantic ammonites from the Cretaceous

the author (i.e. Reeside, 1932) of the newsubgeneric name (i.e. Forresteria) employed
this same name (i.e. forresteri) for one of the
included species. That is tautonymy andaccordingly the type species can be recognized as an original designation. In theTreatise (Wright in Moore, ed., 1957, p.
L432) Forresteria was ranked up to the genus
and Barroisiceras (Forresteria) forresteri
Reeside was written as its type species. This
is not the subsequent designation (as misprinted in Kennedy et al., 1983, p. 251) andwas quite correct on account of thetautonymy (see p. xvi in Editorial Preface of
the Treatise). At that date Wright (op. cit. p.
L432, fig. 551.2) did not mention that F. (F.)
forresteri is a junior synonym of F. (F.)
alluaudi (Boule, Lemoine et Thevenin, 1907).
This synonymy was at first pointed out by
Matsumoto (1969, p. 311-312) with necessary
reasoning and has been confirmed recently byKennedy et al. (1983) on sufficient materialof South Africa. They also commented
amply the subgeneric taxonomy.
Subgenus Forresteria (Forresteria)
Reeside, 1932
Forresteria (Forresteria) alluaudi(Boule, Lemoine et Thevenin)
Figure 101907.

Acanthoceras (Prionotropis) alluaudi Boule,Lemoine et TMvenin, p. 12, pI. I, figs. 6-7,
text-fig. 17.
1908-1979. omitted for brevity.
1983. Forresteria (Forresteria) alluaudi (Boule,Lemoine et Thi!venin); Kennedyet al., p. 267
Table 2.

379

(with full synonymy list).
1984. Forresteria (Forresteria) alluaudi (Boule,Lemoine et TMvenin); Kennedy, p.46, pI. 8,
figs. 4-9.

Material.- HBE-Pl, obtained by Mitsuo
Kitago from Ashizawa, close to and nearly at
the same level as the place where the 5th and6th huge macroconchs of Mesopuzosia yubarensis were contained. It was embedded in
the country rock (not in a calcareous nodule)of greenish grey, medium-grained sandstone,
but the shelly material is mostly resolved andremains only partially.
Dimensions.- See Table 2. As the specimen is secondarily distorted at the preserved
last part of the outer whorl, it is measured ona restored outline.
Description.- Although the specimen issmall, one third (120°) of its outer whorl is the
body chamber. The less deformed septate
part is higher than broad, showing BjH =0.69. The whorl is moderately involute,
about two thirds of the inner whorl is overlapped by the outer one and the umbilicus isnarrow, less than 20% of the diameter.
Despite the compressed shell-form, the ribs
are moderately coarse and provided with
distinct tubercles which strengthen as theshell grows. The clavate tubercles of theouter three rows (on the siphonalline and at
the ventrolateral shoulders) are twice as
numerous as those of the inner rows (bullate,smaller ones at the umbilical shoulders andnodose or spinose ones at the middle offlanks). The suture is moderately incised,showing roughly subrectangular outlines of

Measurements of F. (Forresteria) alluaudi on selected specimens.

Specimen

Position

HBE-PI
HBE-PISAS Z591*
OK. H2622**

E
LS
E
E

D

U

-56.0 9.2 (.16)
43.0 7.0 (.16)
45,4 10.6 (.23)
42.0 9.2 (.22)

H
29.0 (.52)
22.5 (.52)
21.0 (,48)
20,4 (,48)

B

B/H

H/h

UT

VT

-21
15.6
21.6
25.0

(.38) 0.72(.36) 0.69(,48) 1.0(.59) 1.22

1.63
1.67
1.52

11

20

13

?23

1.65

II

21

* Ken~~dy et al., 1983, fig. 12 C-D; ** Matsumoto, 1969, pI. 40, fig. 1.
umbilical and ventral tubercles, respectively in outer whorl.

UT, VT: number of380

Tatsuro Matsumoto et al.

Figure 10. Forresleria (Forresleria) alluaudi (Boul e, Lemoine et Thevenin). Specimen HBE-PI , fromthe middle part of the Ashi zawa Formation . Two latera l (A, B), back (C) a nd fronta l (up side down) (D)views, X I. Scale bar = 10 mm.

E, L, U2 and sadd les between them.
Comparison and discussion.- Based on avery large co ll ection (over 100 specimens)from a particular zone (Coniacian U) of
South Africa, Kennedy et al. (1983) haverecognized a great variabi lity of F . (F.)
alluaudi and placed in sy nonymy numerous
previously described species from South
Africa , Madagascar, North America andJapan . They did not, however, stated clearly
the distinction between the dimorphic pair.
Only one examp le, SAS Z923 (ditto, fig. 28) is
explained as " adult? microconch with bodychamber" . Any macroconch with completely preserved body chamber does not seem tohave been illustrated. They did not indicate
the position of the last septum in their numerous figure s, except for a few internal moulds
with clearly exposed sutures. The early partof our specimen up to 0 = 30 mm is similar to
SAS Z2195 (ditto, fig . 11 A-B) from South
Africa, whose Bj H = O.72. In our specimen
Bj H = 0.6 at the corresponding size (i .e. H=
15 mm) and 0.72 at 0 = 56 mm. In the compressed , involute and narrow ly umbili cateshell-form, our specimen may be comparablewith what Kennedy et al . (1983, figs. 7A-C,
D - F) illu strated as "slender variants" of F.

(F.) alluaudi, but quite dissimilar in ornaments. That slender form is feebly and finely
ornamented with numerou s ventra l clavi ,whereas our form has as coarse ribs and asstrong tubercles as those of normal or typical
middle aged she ll s of F. (F.) alluaudi . For
example, as to the ornamentation , our specimen resembles quite well such a n example ofF. (F.) alluaudi as SAS Z59l (ditto , fig. 12C- 0) from South Africa. In addition to thesix specimens described by Matsumoto (1969 ,p. 308, pI. 40, figs. 1- 4 ; text-figs. 5-7 ) fromthe Ikushumbets area of Hokkaido , there are
now more specimens from the Haboro andother areas of Hokkaido. Thi s is not theplace to describe them but they are all what
we cal l normal forms , with so me (but not
extreme) extent of variation. To sum up, thespecimen from the middle part of the Ashi zawa Formation of the Futaba Group is
identified with F . (F .) alluaudi and probablyof middle growth-stage. Thi s species showsa world-wide di stribution and occurs in the
Middle Coniacian , where accurately dated(Kennedy, 1984, p. 46). That statement con forms with the biostratigraphy of the Futaba
Group.

895.

Gigantic ammonites from the Cretaceous

References cited
Boule M., Lemoine, P. and Th~venin A., 1906-1907:
C~phalopodes cr~tac~s des environs de DiegoSuarez. Ann. Pallont., vol. I, p. 173-192 (120), pIs. 14-20 (1-7) (1906); vol. 2, p. I-56 (2176), pIs. 1-8 (8-15) (1907).
Hashimoto, K., Matsumoto, T. [Takeo], Suzuki, C.
and Nagata, T., 1981: Records of excavation of
the huge ammonites from Iwaki City. TairaGeol. Soc. Bull., no. 4, p.II-15 (incl. 2 pIs.) (inJapanese).
Hoepen, E.C.N. van 1968: New and little known
Zululand and Pondoland ammonites. Ann.
Geol. Surv. S. Africa, vol. 4 (for 1965), p. 157181 (incl. 12 pIs.), I map.
Kennedy, W.J., 1984: Systematic palaeontology andstratigraphic distribution of the ammonite faunasof the French Coniacian. Spec. Pap. Palaeont.,
no. 31, 160 p., 33 pIs.
- - , Wright, C.W. and Klinger, H.C., 1983:
Cretaceous faunas from Zululand and Natal,
South Africa. The ammonite subfamily Barroisiceratinae Basse, 1947. Ann. S. Afr. Mus.
vol. 90, pI. 6, p. 241-324,51 figs.
Lehmann, U., 1981: The ammonites. Their life
and their world. Engl. transl. by Janine Lettau.
246pp., Cambridge Univ. Press, Cambridge.
Matsumoto, T., 1954: Family Puzosiidae from Hokkaido and Saghalien. Mem. Fac. Sci. Kyushu
Univ. [D] Geol., vol. 5, no. 2, p. 69-118, pIs. 923.

381--,1969: A monograph of the Collignoniceratidae
from Hokkaido. Part III. Ibid., vol. 19, no. 3, p.
297-330, pIs. 39-45.
- - , 1988: A monograph of the Puzosiidae (Ammonoidea) from the Cretaceous of Hokkaido.
Palaeont. Soc. Japan, Spec. Pap., no. 30, iii+
179 p., 88 figs.
Moore, R.C. ed., 1957: Treatise on Invertebrate
Paleontology, Part L, Mollusca, Cephalopoda,
Ammonoidea., 490 p., Geol. Soc. Amer. andUniv. Kansas Press.
Reeside, J.8., 1932: The Upper Cretaceous ammonite
genus Barroisiceras in the United States. U.S.
Geol. Surv. Prof. Pap., 170B (for 1931), p. 9-29,
pIs. 3-10.
Saito, T., 1960: The stratigraphic studies of the
Futaba Group, Futaba-gun, Fukushima Prefecture (Part I). Bull. Fac. Arts & Sci., Ibaraki
Univ. (Nat. Sci.), no. II, p. 107-113 (in Japanesewith English abstract).
- - , 1961 : The Upper Cretaceous System ofIbaraki
and Fukushima Prefectures, Japan (Part I).
Ibid., no. 12, p. 103-144.
Tokunaga, S. and Shimizu, S., 1926: The Cretaceous
formation of Futaba in Iwaki and its fossils.
Jour. Fac. Sci., Imp. Univ. Tokyo, Sect. II, vol.
I, no. 6, p. 181-212, pIs. 21-27.
Yanagisawa, I., Sato, T., Nemoto, M. and Nemoto,N., 1973: Large ammonites from Iwaki City.
Report no. I, 15 p. incl. 3 pIs. (in Japanese).
Iwaki City Board of Education, Fukushima
Prefecture.

Ashizawa 1SlR (Jt!!~), ..@lR (~~), Fukuoka mllUJ, Fukushima fi,lll" Haboro ;j3J
1jJ16, Futaba XlI.~, Hirono J.tlT, Hisanohama ~z¥A, Hokkaido ~ti'ta~, Ikushumbets(Ikushunbetsu) ~~5.lIj, Iwaki ~ ,b ~,Momokizawa f;Jt*:lR, Nishi @, Ohhisa (sometimes called Oohisa or Ohbisa) *~, Sakurada WEE, Shimo-Asamigawa r/':l1;~}II,
Taira 3j2, Yotsukura ~~m,lll,!JiI<O) B1II!*XlI.~~f¥giH3:*7 /' -'E- T -1 r ; ~§clt 1963 ~t)* 10 ,¢.iJ;:.Jt 1...-, -t-O)gt1±l0)~1!f~i61), *$7h'b~mEER1tEtB~;:.Jili:~' f*~~.h"t:~'G7.J~, ~~7.J~*i*~-C
i6~kof*~~.KaN~i6G~ ffi~K~C'~~~~i6I), ~-~t~~~.hGoW~$lJl:Z'ffifml¥J~;:.~:J'i5i"" G t IfHE7.J;b7.J'G oop~ i "('a~}j7.J;~*t':7.J;jjljjfJlljlt~~ '8iii-c,~.O)*~t.A~a~ru-c~.~M~~~Z'~i""o -t-O)~O)~.~m~, ~i'ta~Kl<
gti"" G Mesopuzosia yubarensis (Jimbo) O)~fi t ~ ? 0 3((.ohiU~'$ t 1±m (*9 240') 7.J' GJ)j(;G~O)~}j~t~~1L~Z'*lftulrIJTiiiIH~%, ~.O)~7.J;ilHtWl~i"" G7.J,b I) ~;:,~~'~M~1!i~7.J~J.t~ ,r"m;~"('fJlljiiiF9-¥i;:'~ C, f±mf&-¥ "('It* < tt. I) ~~,~ G~ Z'~i"" G0 IDt i:J ~-CilH£7.J; 82 cm ~ I), ffifi;:.lt 120 cm Z'~-*- Go .:.h t ~~O) ~ 0) It~ti'ta~7.J' G ~ ~JlI~1!f~.ht":oXll.~0)It~*j&J;@0)~1t7.J;l < b7.J'GoJ:§c~O)=-mlO)"<!/ P ::1 /'!/ (M IDt)~~.hGo gtJt!!ft~~O)~ I) ~~,Jt!!IKF9"(', ~JfI¥Jf::.ltXll.~~f¥r$O)"@lR~op{flH;:.~t..:
G7JE.*IHt'L-li'Y;'fi--li'Y.7JE;'fiO)~~ G.ht..:$5t OJ ~ 20 m opO) 2 ~$) "(', 1=1= :dtE~lt::1 =7 y 7 /'flfop-li'y$Z'~i"" 0 M IDtt.:vtO)~~gtI±lO)JlEl3 i;:.-?~'"t:~~ 1.. - t..:oUs

i0*Jtt!~ , tN*!iT ' ~*T.!l!

1t~ t

1.. - "t:1!;lH=I=~ Forresteria (Forresteria) alluaudi (Boule, Lemoine et Th~venin) Z'§C

.1...-ko

i0*Jt.,tN* !iTTrans. Proc. Palaeont. Soc. Japan, N.S., No. 157, pp. 382-411, 17 Figs., April 30, 1990

896. EVOLUTION OF SOME LATE CRETACEOUS
DESMOCERATINE AMMONOIDS*HIROMICHI HIRANO
Institute of Earth Science, School of Education, Waseda University,
Shinjuku, Tokyo 169

T AKASHI OKAMOTO
Geological Institute, Faculty of Science, University of Tokyo,
Hongo, Tokyo 113
and

KOHJI HATTORI
Mie Prefectural Corporation, Tsu, Mie 514

Abstract. The Cretaceous sediments of Hokkaido accumulated in an island arc settingthat was part of a plate convergence margin in the Northwest Pacific. Many differences havebeen recognized between such sediments and those of epicontinental seas, and there are also
faunal differences. A land with a coastline extending to north and south laid to the westof the forearc basin in which lateral changes of lithofacies and biofacies occurred. The
desmoceratine taxa Desmoceras (Pseudouhligella) ezoanum. Desmoceras (Pseudouhligella)japonicum. Tragodesmoceroides subcostatus and Tragodesmoceroides matsumotoi. n. sp. tobe described below flourished in this forearc basin sea during Cenomanian and Turonian
times. A phylogenetic progression from D. (P.) japonicum through T. subcostatus to T.
matsumotoi is proposed, based upon investigations of relative growth, sutural ontogeny,
shell ornamentation, stratigraphical ranges and geographical distribution. In this lineage
the eastern limit of the habitat moved towards the west with decreasing adult size at eachspeciation event. The ontogeny of sutural complexity, however, gradually accelerated withtime. The details of the evolution of this lineage and T. matsumotoi are described anddiscussed together with the relationship to such events as a marine transgression/regression,
oceanic anoxic events and speciation/extinction.
Key words. Late Cretaceous, ammonoids, Desmoceras. Tragodesmoceroides.
evolution, speciation.

south in central Hokkaido. Sediments of thesupergroup have been interpreted by Okada(1983) as forearc basin deposits. A coastline
can be distinguished, extending north andsouth, at the western margin of the forearc
basin, and the sea deepened towards the
trench in the east through the structural high.

Introduction

The Yezo Supergroup (Okada, 1982, 1983)
ranging in age from Albian to Maastrichtian
is longitudinally distributed from north to'Received June 14, 1989; revised
accepted February 28, 1990.

manuscript

382

896.

Evolution of desmoceratine ammonoids

Sedimentological aspects of this basin, viz:
Storm deposits in the west, lateral currents
extending from west to east, and north-south
axial currents have been well investigated(Ando, 1987; Tanaka, 1963; Tanaka andSumi, 1981), together with the lateral changeof molluscan faunas from the shallower western faunas to the offshore eastern faunas (e.g.,
Obata and Futakami, 1977; Tanabe, 1979;
Futakami, 1986a, b). The sediments are represented by coastal conglomerate, stormgenerated sandstone, flysch and offshore mudstone, the ages of which have been determinedby ammonoids, inoceramids, foraminifers,
radiolarians, nan no-fossils, isotope dating
and magnetostratigraphy (e.g., Takayanagi
and Matsumoto, 1981).
About two hundred ammonoid species
have been described from the Yezo Supergroup. The longevity of these species varies
from less than two million years to more thanten million years (Hirano, 1984). Amongthem, most desmoceratine species have arange of one stage, which can be interpreted
to mean intermediate longevity. The desmoceratine ammonoids occur fairly abundantly in Cenomanian to Santonian strata
but their specific diversity is low. Although
the various taxa have been described, used aszonal indices, and preliminarily investigatedfrom the viewpoint of phylogeny at a specificlevel, nonetheless a detailed case study of
their evolution has not yet been published.
Recently, the timing of eustatic transgressions and regressions has been revised (Matsumoto, 1977, 1978; Reyment and Marner,
1977; Hancock and Kauffman, 1979; Reyment and Bengtson, 1986) and the importanceof oceanic anoxic events has been recognized(e.g., William, 1988). The relation between
these oceanic events and the evolution ofammonoids is, however, still uncertain. In
general, in considering the evolutionary history of the ammonoids, it is believed thatammonoid groups inhabiting offshore waters
were able to survive crises and were able toimmigrate later into shallower waters where383

ecological niches had opened, because theformer inhabitants of the shallower waters
had died in the crisis (e.g., Wiedmann, 1973).
However, this supposition is not always
proved by case studies.
The morphological evolution of D. (P.)
ezoanum and D. (P.) japonicum of Cenomanian age and T. subcostatus and T.
matsumotoi, n. sp. of Turonian age is investigated in the current work mainly on thebasis of relative growth analyses of population samples, and the relationship between
evolution and oceanic events is discussed.

Materials and methods

Materials
Desmoceratine ammonoids studied in thispaper were obtained from the Middle andUpper Yezo Group in the Oyubari area,
Yubari City and the Obira area, Rumoi
County, Hokkaido (Figure I). Detailedroute maps including the locality guide, geological maps, zonation maps and columnar
sections of the former have been published by
14DEoFigure 1. Map showing the areas studied andthe distribution of the Cretaceous rocks (black areas)in Hokkaido island. The Obira (OB) and Oyubari(Y) areas of the western Cretaceous belt and the
Hidaka (H) and Urakawa (U) areas of the eastern
Cretaceous belt are indicated. Scale: km.

384

Hil'Omichi Hirano et at.

Figure 2. Cross sect ion of an ammonite showing the measured portions. C.A. : Coiling axis, P :Protoconch, B: Whorl-breadth, B7: B at the growthstage of the 3.5 whorls (volution angle: 180" X 7), R :Radius-length , R7: R at the same growth stage as
above, C: Umbilical radius length, C7 : C at thesame growth stage as above.

growth ratio , 8 : spiral angle of the whorl ,C : y-intercept) was obtained from thesemi logarithmic plots, and the growth ratio ,a in the middle growth stage onward wasused to show the characteristics of each population sample, which is defined to be composed of specimens within one and the same
calcareous concretion . The who le morphology including surface ornamentation was a lso
observed in advance of and / or in para ll elwith the biometrical procedure. Sutural ontogeny and va riation were studied with a
Nikon binocular microscope fitted with drawing equipment. In districts with minimal
tectonic disruption , samples are stratigraphically arranged in columnar sections. For
d ating purposes, statistics of population samples are allocated to Inoceramus zones.

Hirano et al. (1977,1980, 1981,1989) and
Hirano (1982 , 1986). A revised locality
guide and columnar sections of the Middle
and Upper Yezo Group of the latter are given
in another paper (Sekine et at ., 1985) inaddition to geological and zona l maps by
T sushima et at. (1958) and Tanabe et at.
(1977). Comprehensive biostratigraphicalguides for these two areas are now underpreparation , and are omitted here for brevity.

B

Methods

D

The concepts and methods of relative
growth and biostatistics used in this accountare the same as those descri bed by Hayami(1969) , Hayami and Matsukuma (1971) and
Hirano (1975 , 1978).
At the beginning of the study, each ammonoid shell was cut and polished to provide
a cross section along or across the medianplane. Then various portions were measured
with a Nikon Profile Projector C- 16 (Figure
2; Hirano , 1975, p. 168, fig . 2, Hirano , 1988,
p. 516, fig. 3). A regression formula, log y=
a8 + log C (where y: radius length , etc. , a:Figure 3. Shell forms of three desmoceratine
ammonites. A, B: Tragodesmoceroides subcostalus,
C: Desmoceras (Pseudouhligella) japonicum , D: D.
(P .) ezoanum.

896.

Evolution of desmoceratine ammonoids

D. poronaicum and D. dawsoni belong to thesubgenus Pseudouhligella proposed by Matsumoto (1938). The characteristics of the subgenus are that the whorl is compressed,
grad umbilicate in the adult stage and that theventer is ornamented with weak subcostae.
D. (P.) japonicum and D. (P.) ezoanum are
the indices for the Japanese Cenomanianstage, and as they have the same stratigraphical and geographical ranges they are

Phylogeny of Desmoceras (Pseudouhligel/a)japonicum
Six species of the genus Desmoceras havebeen recorded from Japan: D.latidorsatum(Michelin, 1838); D. kossmati Matsumoto,
1942; D. japonicum Yabe, 1904; D. ezoanum Matsumoto, 1942; D. poronaicum
Yabe, 1904; D. dawsoni Whiteaves, 1900.
Among these D.japonicum, D. ezoanum,
~

..

ClI

~ c0

tf)

N

!¥p~

A

c:::J

cr::::J

B

I-----l

~

C

~

0

385

Mean & 95 0/0 confidence interval
Observed range
Simple ratio (B/H Ofo)

IFTF? IT

I·r· '1':"114

Ob

II:::::: I: ::: '1"·1r--."'C H

23
1

0

[]

1

1 Y

EB

I

I--

I
I

I.;·;.·)·· .. 1

1

~

of-c

~

u L
-

EU

I

0_

c

~
u L

~

I

-

-

-

,
~

60

- -

-

3

I

Obi &'lliwHilii\'!iI

-

I

18

~

-

17 Y

Ob

7 Y
59 Ob

Y

9

-

35 Ob

113

I-EE-I

EU

Ob

11

I

EB

I

N

L

I

YI E
I:: ::1::: :1

L.

....::l t--

4 Y

II

Ob I

61

c

6 Ob

I

2 Y

-

- -

- -

r:l

1 Y

120

-

Ob

1 Ob

80

100

Figure 4. Chronological change of the simple ratio of the whorl-breadth to the whorl-height at thethird and a half whorl (volution angle: 180 X 7). A: Tragodesmoceroides matsumotoi. n. sp., B:
Tragodesmoceroides subcostatus. C: Desmoceras (Pseudouhligella) japonicum. D: D. (P.) ezoanum. Y:
Oyubari sample, Ob: Obira sample. Each number indicates the number of treated specimens.
0386

Hiromichi Hirano et al.

thought to be sympatric species. D. (P.)
dawsoni is recorded from the Albian, and D.
(P.) poronaicum from the Cenomanian insome limited localities outside of the areas
studied.

Relationship between D. (P.) japonicum and
D. (P.) ezoanum
D. (P.) japonicum and D. (P.) ezoanum areclearly distinguished from each other in several respects: differences in whorl-section
being the most obvious. The flanks of D.
(P.) japonicum are flat and parallel to eachother and the venter is rounded and wide
(Figure 3). On the other hand, in D. (P.)
ezoanum the whorl-section is widest at the
middle of the preceding whorl and it becomes
rapidly narrower outwards, forming anarched venter (Figure 3). This observationof the whorl-section is also biometricallydemonstrated by the simple ratio of whorlbreadth to whorl-height, BjH, at the growth
point of 77C (the third and a half whorl)(Figure 4), where the observed ranges and
95% confidence intervals of means for two
Obira samples of D. (P.) ezoanum clearly do
not overlap those of D. (P.) japonicum. On
the other hand, in the growth ratio of thebreadth to the volution (Table 1, Figure 5)
and the size of the protoconch (Figure 6), theobserved values very much overlap with eachother, and the two species cannot be distinguished by using these characters. The
growth ratio of the radius length of D. (P.)
japonicum in relation to the volution
increases with time (Figure 7) and the growthratio of the umbilical radius of the species inrelation to the volution decreases slightly
with time (Figure 8). Therefore, the simple
ratio of the umbilicus to the diameter, U jD,
at the growth point of 77C also decreases withtime (Figure 9). Although the low numberof samples is insufficient to state with certainty, D. (P.) ezoanum also seems to follow thesame trend. Thus, although these two
species share many common characters, they
can be separated on the basis of some major

characters.

Matsumoto (1954) proposed that
D. (P.) ezoanum was derived from D. inane(Stoliczka), via D. kossmati and D. (P.) poronaicum. However, as. the taxa of this lineage are not presently accessible to us, nofurther mention is possible.

Phylogeny of D. (P.) japonicum
D. (P.) japonicum (Figures lO-I-11 ; Figure 11-26) was first described by Yabe (1904)
under the name of Desmoceras dawsoni
Whiteaves var. japonica. Later it was separated by Matsumoto (1938) as an independent
species, D. (P.) japonicum Yabe. Matsumoto (1941) proposed that the Albian D.
latidorsatum (Michelin) was the probableancestor of D. (P.) japonicum, and later on heagain pointed out that D. (s.s.) latidorsatum
was possibly an ancestor of D. (P.) japonicum (Matsumoto, 1954).
In both the Obira and the Yubari samples,the growth ratio of the radius length of D.
(P.) japonicum in relation to' the volution
increases from the Lower to the Upper
Cenomanian (Figure 7). The same trend isseen in the decreasing simple ratio U jD (Figure 9), the increasing protoconch width (Figure 6) and the decreasing growth ratio of theumbilical radius to the volution (Figure 8).
The other morphologies such as the simple
ratio BjH (Figure 4) and the growth ratio of
the whorl-breadth to the volution (Figure 5)
are stable throughout the entire range of thespecies, until its extinction at the end of the
Cenomanian.
No species of D. (Pseudouhligella) occur in
the Turonian of Japan.' The most similar
Turonian species to the Cenomanian D. (P.)
japonicum is Tragodesmoceroides subcostatus.
Comparison of morphology between the
Cenomanian D. (P.) japonicum and the Turonian T. subcostatus is as follows. There isno clear difference between these two species
in protoconch size (Figure 6), nor in thegrowth ratio of the whorl-breadth to thevolution (Table 1, Figure 5), but the youngest

Table I.

Coefficients of difference among four species on two parameters. Right upper: the growth ratio of the radius length to thevolution. Left lower: the growth ratio of the whorl-breadth to the volution.
D. ezoanum

Desmoceras japonicum

Tragodesmoceroides subcostatus

T. matsumotoi

Uc. Ob

LC.Y

LC.Ob

Uc.Y

UC.Ob

L.Y

L.Ob

N.Y

N.Ob

H.Ob

T.Y

T.Ob

H.Y

H.Ob

T.Ob

1.23

0.80

0.79

0.91

2.54

1.73

2.24

2.16

2.21

2.15

2.48

4.05

3.91

4.51

0.71

0.61

0.31

0.23

0.28

0.32

0.23

0.22

0.36

1.50

1.42

1.63

0.06

1.14

0.80

1.02

1.02

0.97

0.95

1.16

2.50

2.39

2.76

*

0.14

1.84

1.17

1.58

1.54

1.54

1.49

1.82

3.69

3.52

4.22

D.e.

Uc. Ob

*

~

LC. Y

0.27

'";;.::.'c"

LC. Ob

0.48

*

0.47

0.68

UC.Y
UC.Ob

0.42

0.64

*

0.17

0.05

0.63

0.89

0.00

0.07

*

1.63

1.04

1.40

1.37

1.36

1.31

1.62

3.46

3.30

3.96

L.Y
L. Ob
N. Y
N.Ob
H.Ob
T. Y
T.Ob

0.00

0.23

0.41

0.37

0.00

0.11

0.13

0.12

0.14

2.88

2.65

3.58

0.21

0.56

0.50

*
0.06

0.00

0.07

0.53
0.74

0.07

0.07

0.07

0.08

1.52

1.42

1.70

0.29

0.37

0.32

0.47

0.05

*

0.00

0.06
0.00

0.13

0.10

0.10

0.11

2.29

2.12

2.71

0.24

0.38

0.07
0.08

0.00

1.79
2.32

0.19

0.17

0.74

0.68

1.05

0.15

0.10

0.23

0.16

*

0.00

0.00
0.23

1.94

0.06

*

0.18

0.43

0.00
0.00

0.19

0.28

0.55
0.65

0.06

0.00

0.43
0.48

*

0.09

0.19

0.44

0.00

1.01

0.95

1.54

0.34

0.35

0.44

0.37

0.45

*

0.22

0.34

*

1.55

1.13

1.81

1.77

2.52

1.28

1.55

1.38

1.34

1.59

1.90

2.09

1.32

0.93

1.61

1.58

2.22

1.10

1.30

1.19

1.15

1.36

1.57

1.67

0.21

1.24

1.56

1.36

1.32

1.61

2.03

2.34

0.42

.......
s:::

;:;

:--J
s:::
"'
..,'c::.-

~

S

~

'-l

~

H. Y
H.Ob
T.Ob

1.56

1.06

1.85

1.82

2.77

2.25

2.50
2.38

2.21

2.99
2.82

2.47

2.27

3.00

*

0.15

0.00

*

0.18

0.13

*

Gothic numerals: Coefficient of difference> 1.28 i.e., Overlap less than \0% of the area. For abbreviation, Ob: Obira area, Y: Oyubariarea, LC: Lower Cenomanian, UC: Upper Cenomanian, L: Lower Turonian Saxonicus-Labiatus Zone, N: lower Middle Turonian
Hobetsensis nonsulcatus Zone, H: upper Middle Turonian Hobetsensis hobetsensis Zone, T: Upper Turonian Teshioensis Zone, D.e.:
Desmoceras ezoanum, T.m.: Tragodesmoceroides matsumotoi.

00

~

tlJ

~--..

6·
~

~

~

I:)

'"
~

~
S·
~

$:)

~
~

I:)
~
I:)

~

w
00

-.I

Hiromichi Hirano et al.

388

T. subcostatus show a significant nonoverlap with D. (P.) japonicum in the latterratio due to its slightly decreasing trend
throughout the Turonian (Table 1). The
simple ratio of breadth to height at thegrowth point 7n of T. subcostatus also mostly overlaps that of D. (P.) japonicum (Figure4). The growth ratios of the radius to thevolution of the Upper Cenomanian D. (P.)
japonicum do not overlap those of T. subcostatus (Table 1) because of the increasing
growth ratio of D. (P.) japonicum mentioned

above. The same is true for the simple ratio,
UID (Figure 9). The growth ratio of theumbilical radius length to the volution of D.
(P.) japonicum also shows a chronologicallydecreasing trend, but it mostly overlaps thatof T. subcostatus, because the variation of themorphology of the latter is fairly large (Figure 8).
Hirano (1988) mentioned an intermediate
form of D. (P.) japonicum, from the lateUpper Cenomanian, which has T. subcostatus-type anteriorly projected weak ribs

Cb
Ol CLI
C
0
V) N

-"'

Growth rat ioC 8.log B)
I~I

6 Ob

T

033 4 Ob
1 I: : : : : I: : :1:<1 4 Y

-

~

1

c

"'c H

I

ffil:j

1

I

61

I---j::::I:::l

0

L..

lJ

::J I--

~

1

N

1

t--

1

L

1 1 Ob

1 Y
II( ... J·::; .. I I

14 Ob

II' : : : ..... '1

17 Y....... 1

I

I

El

-

-

-

U

-

- - 1

E I-0
c L

2 Y
- - Id..d

-

-

-

I

I

11

Ob

-

20

Ob

~

CLI

0.10

0.11

0.12

~

0.13

1 Y

0.14

0.15

65

Ob

Y

3

AAooooc':1X\'QGl§

I

L

Y

7

~

0 I-C
Cb

Ob

35

leaeea

1

U

I

EE3
1···:'1'····1

E U

U

Ob

23 Y

1

0.16

- -

Ob
0.17

Figure 5. Chronological change of the growth ratios of the whorl-breadth to the volution.
are the same as Figure 4.

Symbols896.

Evolution of desmoceratine ammonoids

on the venter. It occurs at locality R5222(Matsumoto et al., 1978), and the horizon isslightly higher than that of Vascoceras aff.
durandi and Fagesia thevestensis, being
regarded as the lower Lower Turonian. The
whorl-sections of the two species resemble
each other in appearance as well as in thesimple ratio, B/H. Later, plain T. subcostatus was obtained from some contiguous but
slightly lower horizons than that mentioned
above. Thus, an intermediate form mentioned in Hirano (1988) is not remarkable at the389

present time.
In short, only the strength and the anterior
projection of subcostae are different, and theother characters are not always significantly
different between D. (P.) japonicum and T.
subcostatus.
Both species occur most abundantly in andaround Japan. A time gap between the disappearance of D. (P.) japonicum and theappearance of T. subcostatus is very short asshown by a columnar section with a range
chart of these species (Hirano, 1986, p. 10, fig.

Cb Cb
0-

-

ro 0c:

1Il N

Protoconch widthT

1 ~~lfl 1

6 Ob

1··1······1::::::(:·1
1"'1: ...... ::1:. ...... I·.'j

4 V

4 Ob

1

c:

.-ro

1

c: H

....

~

0

-

1
1 alB

1 1 Ob

Ob

61

I

23 V

1 V

r.....
"I" I

1
I

N

I

I: : : : :1 : : : :1

0

::J

I1llI

35
V

Ob

1

14 Ob

1

I" " .1" . : .1

1

17

I--

.. T... j
1 I"
I--E3II3 1 7 V
'

L

c:

Cb
U

-

Wl»mNXm

1-uFigure 6.

Ob

~

L
0.5

1
(jJ

V

EE3

I

0._

11

- -~
- - - - - - - - - - - - -

0

c:

1

2

ECb

65 Ob
3 V

1

~

L

U

tI!I

1

E U

0

I 20

Ob

Ob
1 V

Chronological change of the protoconch width.

0.8

0.9 mmSymbols are the same as Figure 4.

Hiromichi Hirano et af.

390

4).
It could almost be concluded that T. subcostatus evolved from D. (P.) japonicum on
the basis of the information mentioned above.
The tempo and mode of evolution seem to beconcordant with the punctuated equilibrium
hypothesis of Eldredge and Gould (1972),
although we cannot make an unequivocal
conclusion on this point especially in view ofthe presence of polymorphic mechanisms, asmentioned by Hayami and Ozawa (1975) and
Hirano (1978, 1979).

Q)

-"'

Q)

0'1

C
0
N
!j')

Speciation of Tragodesmoceroides
suhcostatus
We have elucidated the allopatric speciation from T. subcostatus (Figures 11-1-12)
to T. matsumotoi, n. sp. (Figures 11-16-25)
on the basis of numerous specimens obtained
from various stratigraphical levels.
Among the six characters (Figures 4 - 9),
the clear differences of these two species in thegrowth ratios of the radius length (Figure 7)
and breadth (Figure 5) to the volution demonstrate this fact. The ranges of these two

c::o Mean & 95 Of. conf idence interval

kcc§oc'iJ A~

1----1 Observed range

c::::J B~ D

Growth ratio(9.logR)

~ 60b

T

~:~;;:;j"""1

I

c
H
c

I

"'

m

I

61 Ob

~

I

23 Y

L..

;:,

0

r--

L

lEa

1 14 Ob17 Y

1 65 Ob!ieII®4

1

U

~

0 I-C

I~

- - -

-

-

- - - -

2

Y

- - 20 Ob 1

-

Q)

U

1 11 Ob-- - f:J0c

3 Y

feeeee*eeeeeeeeem

I

Q)

u L
E

1 17 Y

1.····1·:; :::1

I

U
I"-

1 35 Ob

EE3

1

r--

E

1 Y

EEl

1

N

4 Y

kl:::1 1 11 Ob

1

0

~

4 Ob

",'1::::::::::1:::::':::::::::1

r--

L
0.13

0.14

C

0.15

0 01.16 Y

0.17

0.18

0.19

- - -

- -

1

1 Ob

0.20

Figure 7. Chronological change of the growth ratios of the radius length to the volution.
the same as Figure 4.

0.21
Symbols are896.

Evolution of desmoceratine ammonoids

embedded authochtonously. All of the specimens which belong to T. matsumotoi, n. sp.
occur only in the district of Takishita (locs. A
and C of Figure 12) and Kamikinenbetsu(loc. B of Figure 12) in the Obira area. T.
subcostatus, which has significantly larger
growth ratios, occurs in the east to north-east
district of the Obira area (Tanabe et al.,1977), and these two species never co-occur.
The same is true in the Oyubari area, where
the new species occurs only at one locality

growth ratios show clearly different values
and there is either no overlap or only veryslight overlap between these two species(Table 1). It is clearly demonstrated by
Tanabe (1979) that the distribution of ammonoid spcies laterally changes from the west
to the east in the Obira area. In addition,
many desmoceratine ammonoids studied inthese areas in this time contain their aptychi
in their body chamber, in situ. Thus, itfollows that most desmoceratine ammonoids

CI.I

-

391

CI.I

01
ro c0

If)

N

Growth ratio(8,log C)
6 Ob

~

T

[·.·.1 ....

t· . ... [ . ..

I

B:3

1

23 V

I e3

0

EJ

r--

1V
I·.···j.... !

~

-

-

-

U
E r--

- - - I
I

0

0.050

65

I

1 1 Ob

-

-

-

I

m 1V

0.075

Ob

I

2 V

- -

fjl

0.025

Ob
1 7 V

f*'mvllXWll//l,,\vlA

L

V

3 V

~
I

17

En

[';,lm

I

c
CI.I
u L

14

I
I

-

I

I: : : : : '1: "::. ":":1

I

35 Ob

I

I

L

CI.I

1 1 1 Ob

EEJ

I

r--

U

4 V

Ob

61

L..

E U
0
c r--

.... ·1· ........ ;;:;::n
I

::J

N

4 Ob

[ifJ

I

c
ro
.c H
~

.. j.... ··1·:-:·:1

0.100

-

-

I

-

-

-

20 Ob

1 Ob
0.125

0.150

0.175

0.200

Figure 8. Chronological change of the growth ratio of the umbilical radius length in relation to thevolution. Symbols are the same as Figure 4.

Hiromichi Hirano et al.

392(loc. 2344 of Hirano et al., 1981, fig. 4; alower stream of the Pankemoyuparo River).
The adult size of T. subcostatus is also larger
than that of T. matsumotoi. Thus, the newly recognized species, T. matsumotoi is characterized by: (1) it occurs only from the
Hobetsensis and Teshioensis Zones of the
Middle-Upper Turonian, (2) it occurs only inthe north-west part of the Obira area andfrom one restricted locality in the Oyubariarea, (3) it occurs strictly allopatrically withrespect to T. subcostatus, (4) the adult size issmaller than T. subcostatus and (5) somebiometrical parameters do not overlap thoseof T. subcostatus. On the basis of suchdifferences mentioned above, the new species
T. matsumotoi is distinguished from thehitherto known T. subcostatus. Incidentally, the Cretaceous System of the westernpart of the Obira area is both empirically andquantitatively known to yield more inshore
ammonoids than does the eastern part
(Tanabe, 1979). There is scarcely any doubtthat these two species were in a relationship

Q)

en Q)
C

ttS

IJ)

0
N

Simple ratio(U/D Ofo)

1 ~ ::::~ -, ~E,;~-;:::- 'I

T

I'·'!""'" "l

.-c H
....0

1--- fn..
1 1:"1"1
1

1
EI3

I

I

I

fIW

1

0

I

L

-

E~

13 Ob

U

'r-' '1 1

7 Y

I

9 Ob

59 Ob

~

- - - - - - ~- 2- Y- I

~
==

0

c

I 17 Y

3 Y

!M

c -

Q)

1 35 Ob

1 1:"

E U

1 Y

I· '1"'1

1

I--

I

18 Ob

~

1 Ob

L

iii
8

23 Y

1 1 Ob

EE3

N

Q)

1

0

::J

L

1

-=--

1

t- I - -4 Y~

61 Ob I

C
ttS

Ob

4 Ob

1«« I: : : . : : : .. ·~············3··l

I--

U

1 6

10

12

14

16

18

20

1 Y
22%

Figure 9. Chronological change of the simple ratios of the umbilical diameter to the whorl diameterat the growth stage of the third and a half whorl. Symbols are the same as Figure 4.

896.

'.,

9

Evolution of desmoceratine ammonoids

393,""1'••-' . ~.

10

11

Figure 10. Desmoceras (Pseudouh/ige//a) japonicum Yabe. 1, 3 (l ateral) a nd 2 (posterior) from
A20l4c. 4 (posterior), 5 (latera l) and 6 (cross section) from YC24l4. 7 (posterior) and 8 (lateral) from
As70 1Sf. 9 (l ateral) and 10 (posterior) fro m T504J. 11 ( latera l) from As70 1Sd. All in natura l size.

Hiromichi Hirano et al.

394

of habitat segregation. Some biometricalparameters show no difference between T.
subcostatus and T. matsumotoi, and for thisreason the two species are considered to bevery closely related to each other. Tragodesmoceroides matsumotoi most likely speciatedfrom T. subcostatus. No morphologicalchange in T. subcostatus is detected throughout its range, either in an observational or abiostatistical view.
Both species died out at the end of theTuronian, and no descendants are detectedamong the Coniacian desmoceratids.

and deep incisions. Arkell et al. (1957)
summarized the generic diagnosis based upon
Matsumoto (1942, 1954), and it is as follows:
Very involute, moderately inflated; falcoid
constrictions and sharp, dense falcoid ribs or
striae on outer part of side, and strongly
projected on venter, mid-line of which tends
to be raised.

Tragodesmoceroides matsumotoi, sp. nov.
Figures 11-16--25
1988

Tragodesmoceroides sp.: Hirano, In Wiedmann and Kullman eds., p. 513-523.

Systematic description
Order Ammonoidea Zittel, 1884
Suborder Ammonitina Hyatt, 1889
Superfamily Desmocerataceae Zittel, 1895
Family Desmoceratidae Zittel, 1895
Subfamily Desmoceratinae Zittel, 1895
Genus Tragodesmoceroides Matsumoto, 1942

Type-species: Tragodesmoceroides subcostatus Matsumoto, 1942.
Generic diagnosis: Matsumoto, 1942 (p.
25, p. 28, figs. I-dl and d2) described thegeneric diagnosis with illustration, and laterhe (Matsumoto, 1954, p. 262, pI. 4) fully described it with a photograph. According to
the latter the generic diagnosis is as follows:
Relatively small desmoceratids characteristically ornamented with sharp and narrow ribs
which covers the ventral half of the matureshell. Similar to Desmoceras in shell-form,
but with a very narrow crater-like umbilicus.
Apertural margin provided with strongly
projected sinuses. Suture-line similar to thatof Desmoceras in general pattern, with fineTypes: WEA103T (Figures 11-22--24) isdesignated here as the holotype, which was
obtained at locality A, Takishita, Obira area
(Figure 12; same as loc. R6072 of Tanabe etal., 1977). Two specimens, WEAlOlT (Figures 11-16--18) and WEA102T (Figures 1119--21) are designated as paraty.pes, both ofwhich were also obtained from the same
exposure as the holotype.
Materials: Sixty-one specimens from Middle Turonian Inoceramus hobetsensis hobetsensis zone at locality A, the River Obirashibe and six from Upper Turonian Inoceramus teshioensis zone at locality B, the River
Kamikinenbetsu of the Obira area (Figure12), and twenty-three from Inoceramus hobetsensis hobetsensis zone at locality YC2357,
the River Pankemoyuparo (Hirano et al.,1981) of the Oyubari area are used in thisstudy. All the specimens including types
mentioned above are curated in the Typecollections, Institute of Earth Science, Schoolof Education, Waseda University.
Etymology: Dedicated to Tatsuro Matsu-~ Figure 11. 1--15: Tragodesmoceroides subcostatus Matsumoto. 1 (lateral), 2 (posterior), 3 (crosssection) from YE2009b. 4 (cross section) from YE2009b. 5 (lateral), 6 (posterior), 7 (lateral) from
2YC3050X. 8, 9 (lateral), 10 (posterior), 11 (anterior) from Y A6037. 12 (lateral, X 2 of 13), 13 (lateral),
14 (posterior), 15 (cross section) from R5222=T6044a-84. 16--25: Tragodesmoceroides matsumotoi, n. sp.
16 (lateral), 17 (section), 18 (posterior) from loc. A, Paratype (WEAlOIT). 19 (lateral, X 3), 20 (posterior, X
3), 21 (cross section, X 3) from loc. A, Paratype (WEA102T). 22 (lateral, X 3), 23 (posterior, X 3), 24 (crosssection, X 3) from loc. A, Holotype (WEA 103T). 25 (lateral, X 3) from loc. A. 26: Desmoceras (Pseudouhlige/la) japonicum Yabe. 26 (cross section) from As7018f. All in natural size unless otherwise mentioned.

896 .

Evo/ution of desmoceratine ammonoids

395

6

396

Hiromichi Hirano et al.

moto, a noted investigator of cephalopods
and historical geology.
Specific diagnosis: A species of Tragodesmoceroides, which is characterized by anddistinguished from other species in clearlysmaller growth ratios of the radius length andthe whorl-breadth in relation to volution andsomewhat smaller growth ratio of the umbilical radius length in relation to the volution.
Description: The shell is small and mostly
less than 2 cm in the adult diameter. The
whorl-section is rounded and the height isnearly the same as the breadth in the earlystage, but the height increases more rapidly
than the breadth. The growth ratio of theradius length in relation to the volution issmall (Figure 7). The growth ratio of thebreadth in relation to the volution is alsocharacteristically small (Figure 5). Thus,
flanks are nearly parallel to each otherbeyond the middle growth stage, although
they are somewhat inflated. The umbilicus
is narrow and deep through the development
as shown by the small growth ratio of theumbilical radius in relation to the volution(Figure 8). The shell surface is ornamented
with numerous falcoid lirae in the middle
growth stage and subcostae in the adult stage,
which strongly project anteriorly in the ventral area. There are a few falcoid constrictions, which are mostly parallel to lirae or
subcostae, on one whorl. The ontogenetic
development of a suture-line is characterized
by that of Desmoceratidae (Figures 13-16),
and is ELV2V3V4=S, VlvVldI (Figures
15-16) in terms of the sutural formula ofKullmann and Wiedmann (1970). The
sutural patterns of T. subcostatus (Matsumoto, 1954, p.264, figs. 8-9; Figure 14)
are substantially the same as those of thepresent species, but the formula can bedifferent whether the differentiation of the VI
after the formation of V2 is considered as
VlvVld or V3. The adult sutural pattern isaccomplished beyond the third whorl.
Comparison: The present species is very

similar to ancestral T. subcostatus (Figure 4).
In relative growth analyses, the present
species is clearly distinguishable from T. subcostatus in the smaller growth ratios of theradius length and the breadth in relation to
the volution (Table I). The growth ratio of
the umbilical radius of the present species inrelation to the volution is somewhat smaller
than that of T. subcostatus (Figure 8).
Although statistical comparison is impossible at the present because of the lack ofapertural margin of the shell, the adult size ofthe present species is clearly much smaller
than that of T. subcostatus in 183 specimens.
There is no significant difference in the
sutural pattern between T. subcostatus andthe present species (Figures 14-16), but
ELV2V3V4=S, VlvVldI is accomplished at
the second and a half whorl in T. subcostatus
and beyond the third whorl in the present
species. These two species of Tragodesmoceroides have deeper lobes and more complex incisions than D. (P.) japonicum (Figure
13).

Occurrence: The present species occurs in
the Turonian Inoceramus hobetsensis hobetsensis and Inoceramus teshioensis zones, withacanthoceratacean ammonoids in the westernnearshore shallower facies, where hummocky
cross-stratification of medium-grained sandstone deposited at the bottom shallower thanintense storm wave base is preserved, andnever co-occur with T. subcostatus. Incidentally T. subcostatus occurs in the eastern outer intermediate facies of the Western
Cretaceous belt, where turbidites predominated, but does not occur in areas as far as the
Hidaka (Obata et al., 1973) and Vrakawa(Kanie, 1966) of the Eastern Cretaceous belt,
where offshore mudstone predominated.
T. subcostatus of North America was described by Matsumoto (1959), but the occurrence of the present species is still unknown
there.

~ 6

G

9

D

10

g5 [dB
D
§
4

7

~3

g2

00
'0

?~

bd

..:
I:)

RIVER

OBIRASHIBE

i::......

o·
~

13

~

~

12

~

I:)

'...."'~

11~......

S·

N

~

~

~
~

f
D
I
R~IER

I:)
~
I:)

~
I KM

=:J

NAlAlINEIBETSU ~Figure 12. Map showing the fossil localities A, Band C of T. matsumotoi, n. sp. and Inoceramus zonation of the Obiraarea. 1: Cenomanian formations, 2: Lower Turonian Inoceramus labiatus zone, 3: lower Middle Turonian I. hobetsensis
nonsulcatus zone, 4: upper Middle Turonian I. hobetsensis hobetsensis zone,S: Upper Turonian I. teshioensis zone, 6: Lower
Coniacian I. uwajimensis zone, 7: Upper Coniacian I. mihoensis zone, 8: Lower Santonian I. amakusensis zone, 9: Upper
Santonian I. japonicus zone, 10: Tertiary, 11: Boundary of zone, 12: Local key-marker tuff bed, 13: Fault.

W

\0
-.J

Hiromichi Hirano et al.

398

Discussion

1. Migration to shallower water.
Tsushima et al. (1958) showed that theUpper Cretaceous sediments become coarser
westward and finer eastward, and Tanabe(1979) demonstrated that acanthocerataceanammonoids occur abundantly westward.
These results are in agreement with the resultsof Tanaka (1963) and Tanaka and Sumi
(1981) on palaeocurrent analyses of the wholearea of the Cretaceous Yezo Supergroup.
The sedimentary facies which transect the

Yezo Supergroup were schematically illustrated by Matsumoto and Okada (1973),
Okada (1982) and Hirano (1982), which show
the western inshore and eastern offshore
facies.
In such a basin setting, T. matsumotoi isallopatric to T. subcostatus and occurs onlyin the nearshore area. T. matsumotoi often
co-occurs with acanthoceratacean ammonoids
in the localities. The peculiar faunal composition of T. matsumotoi at Takishita, Obirahas already been discussed by Tanabe (1979,
p.619, Table 2 for locality R2003) from a

N~

o~
p~

Q~
i

~H

I

R~

~G

=

s

t~F
~E

T

u

=
Figure 13. Sutural ontogeny of Desmoceras (Pseudouhligella) japonicum Matsumoto represented by
two specimens from the Obira area. A-J: T6311-12x85-1, A: primary suture (0.157), B: 1/2 whorl, C:
I whorl(0.236), D: 1+ 1/3 whorl (0.420), E: 1+ 1/2 whorl (0.484), F: 2 whorls (0.865), G: 2+ 1/2 whorls(1.187), H: 3 whorls (1.675), I: 3 + 1/2 whorls (2.270), J: 4 whorls (3.467), K- U: T631 1-12x85-2, K :probably primary suture (0.167), L: probably 2nd suture, M: 1/3 whorl (0.230), N: 1/2 whorl (0.287), 0:
I whorl (0.400), P: 1+ 1/3 whorl (0.470), Q: 1+ 1/2 whorl (0.609), R: 2 whorls (1.050), S: 2+ 1/2 whorls(1.440), T: 3 whorls (2.202), U: 3+ 1/2 whorls (3.529). Height of the whorl in mm in parentheses. Bar
scale: I mm, A-E, G-I, K-M, N-Q, R-S and T-U are in the same scale, respectively.

896.

Evolution of desmoceratine ammonoids

399

Acila sp., Nanonavis sp. and ostoreid, gastropods, simple corals, fish bones, floatingwood and plant leaves in addition to someacanthoceratids at the type-locality of T.
matsumotoi. It is of no doubt that these two
species of Tragodesmoceroides inhabited

different view, although the species was not
yet been recognized at that time. We recognized hummocky cross-stratification, whichindicates a shallower condition than storm
wave base, in some medium-grained sandstone beds and obtained such bivalves as

L~

O~

p~

=

Q~
J

,

R~
5

~E

{\,rv~ 0

~c
~B
~A
,

i

u

=

Figure 14. Sutural ontogeny of Tragodesmoceroides subcostatus represented by two specimens fromthe Obira area. A-K: T6039-0-85-1. A: primary suture (0.159), B: 4th suture, C: 1/2 whorl (0.228),
D: I whorl (0.351), E: I + 1/2 whorl (0.559), F: 2 whorls (0.800), G: 2+ 1/2 whorls (1.115), H: 3 whorls(1.720), I: 3+ 1/2 whorls (2.531), J: 4 whorls (3.200), K: 4+ 1/2 whorls (5.230). L-U: T6039-0-85-2.
L: primary suture (0.157), M: 2nd suture, N: 1/2 whorl (0.288), 0: I whorl (0.359), P: 1+ 1/2 whorl(0.465), Q: 2 whorls (0.755), R: 2 + 1/2 whorls ( l.l 07), S: 3 whorls (1.383), T: 3 + 1/2 whorls (1.716), U :4 whorls (2.671). Height of the whorl in mm in parentheses. Bar scale: I mm, A-F, I-K, L, P, Q and T-u are in the same scale, respectively.

Hiromichi Hirano et al.

400

K~

=

L~

M~
I

,

N~

=

~F
=

o~~

~E

p

~D
Q

~c
~B
~A

R

i

Figure 15. Sutural ontogeny of Tragodesmoceroides matsumotoi, n. sp. represented by two specimensfrom the Obira area. A-I: TIOI2yl-85. A: 2nd suture, B: I whorl (0.299), C: 1+ 1/2 whorl (0.403),
D: 2 whorls (0.491), E: 2+ 1/2 whorls (0.626), F: 3 whorls (0.958), G: 3+ 1/2 whorls, H: 4 whorls (I.
975), I: 5 whorls (3.990). J-R: TlOI2h8-85. J: 1/2 whorl (0.219), K: I whorl (0.249), L: 1+1/2
whorl (0.305), M: 2 whorls (0.421), N: 2+ 1/2 whorls (0.587), 0: 3 whorls (0.798), P: 3+ 1/2 whorls(1.104), Q: 4 whorls (1.553), R: 4+ 1/2 whorls (2.039). Height of the whorl in mm in parentheses. Bar
scale: I mm. A-D, J-M, N-O and P-R are in the same scale, respectively.

different waters of conditions; T. matsumotoi shallower nearshore water and T. subcostatus deeper offshore water.
D. (P.) japonicum, the ancestor of T. subcostatus, occurs in the western and eastern
belts of the Cretaceous Yezo Supergroupwhich is distributed longitudinally north tosouth in central Hokkaido. However, T.
subcostatus, does not occur in the deeper
eastern belt, being limited in the outer intermediate facies of the western belt, where turbidite~ predominate.
T. matsumotoi exclusively occurs in the western nearshore faciesof the western belt, where stormbeds predominate. Thus, the lineage of T. matsumotoi

via T. subcostatus from D. (P.) japonicum
changed habitat toward western shallower
water at each speciation episode.

2.

Size decreasing strategy.

Evolutionary size increase has already been
discussed by many authors on various taxa (e.
g., Hallam, 1978; Hayami, 1978). The present lineage shows the reverse, size decrease.
Even in the Yezo Supergroup which yields
exceptionally well preserved shells, it is not sofrequent to see completely preserved adultspecimens with a peristome and an undeformed body chamber. The approximation of
the final septum which indicates the close of
growth is not always confirmed. Although896.

Evolution of desmoceratine ammonoids

401

K

N~
1

o~

~G
i

I

~F
R

~E

~D

s

~c

~B
~A

T

!

Figure 16. Sutural ontogeny of Tragodesmoceroides matsumotoi and Damesites damesi for comparison. A-K: T. matsumotoi (Y090009a-85) from the Oyubari area. A: primary suture (0.128), B: 2ndsuture, c: I whorl (0.273), D: 1+ 1/2 whorl (0.352), E: 2 whorls (0.506), F: 2+ 1/2 whorls (0.716), G: 3
whorls (1.026), H: 3+ 1/2 whorls (1.412), I: 4 whorls (1.998), J: 4+ 1/2 whorls (2.998), K: 5 whorls(4.594). L-T: D. damesi (KI007g-82) from Santonian I. amakusensis zone in the Kotanbetsu area, northof the Obira area. L: primary suture (0.10 I), M: 1/2 whorl (0.116), N: I whorl (0.311), 0: I + 1/2 whorl(0.424), P: 2 whorls (0.624), Q: 2 + 1/2 whorls (0.910), R: 3 whorls (1.301), S: 3 + 1/2 whorls (I. 799), T :4 whorls (2.459). Height of the whorl in mm in parentheses.. Bar scale: I mm. A-F, G-J, L-Q and
S- T are in the same scale, respectively.

402

Hiromichi Hirano et al.

we cannot show quantitatively the change ofadult size in the present lineage under suchconditions, we can recognize a trend of size
decrease in the description of Matsumoto(1938, 1942, 1954) and Figures 10-11 of thispaper: Specimens of D. (P.) japonicum
which exceed 10 cm in diameter are very
common; T. subcostatus has a maximum
diameter of 4 cm, and T. matsumotoi does
not grow over 3 cm- maximum diameter.
This conclusion does not come from a few
specimens of some limited areas, but fromseveral hundred specimens of various localities in the Yezo Supergroup which is distributed in the area of some 50 km in thewidth of east and west and of some 200 km in
the length of north and south. Therefore
this conclusion is not biased by current sorting or other sedimentological factors.
These lines of evidence indicate that theevolutionary lineage of T. matsumotoi via T.
subcostatus from D. (P.) japonicum migrated
into shallower water step by step with adecreasing trend of the adult shell size. It is
not yet clarified that the population sizes ofthese species increased with the change overof these strategies, but T. matsumotoi seems
to occur most abundantly.

3.

Sutural complexity.
In spite of the fact that the present lineage
changed its habitat from deeper water toshallower water at each episode of speciation,
the sutural complexity increased. We measured the rate of ontogenetic development ofa half length of the suture line in relation to
the area of the whorl section in the growthstage from the middle of the second whorl to
the fourth whorl for each species (Figure 17).
The result indicates us that the growth rate of

the sutural length consistently accelerated inrelation to the area of the whorl section, thatis, the suture historically became more complex for a same area. The function of suturalpart is regarded as hydrostatic apparatus toprotect the whorl against water pressure withleast amount of shell material (economy ofcalcium carbonate) and provision for muscle
attachment (Westermann, 1971; Hirano,
1975; Seilacher, 1975; Kennedy and Cobban, 1976; Bayer, 1977; Henderson, 1984).
The phylogenetical increase of sutural complexity is not explained only from this view,
because the present lineage immigrated into
shallower waters. Thus the mode of life andthe depth of the water column where theseammonoids inhabited are important topics,
and pleitropy may have played a key role inrelationship to changes of other characters.

4.

Relation to oceanic events.

Many conditions which control the rise anddecline of marine animals have been recognized. It has also been recognized. that timesof marine regression coincide with major
boundaries of geological ages which aredefined by extinctions/appearances of marine
animals. Wiedmann (1973), for example,
adovocates that the renewal of ammonoid
faunas at each age boundary of Late
Cretaceous is due to the effects of marine
regressions at each boundary. However,Matsumoto (1977) and Hancock and
Kauffman (1979) have shown that eustatic sea
level changes do not necessarily coincide withage boundaries in the Cretaceous. Therefore, the renewal of ammonoid faunas at eachage boundary has to be investigated for eachage in each area. For such a study aprobabilistic contemporaneous extinction~ Figure 17. Acceleration in the ontogeny of sutural complexity of the lineage from D. (P.) japonicum
through T. subcostatus to T. matsumotoi. A few specimens for these species are chosen, and ontogenetic
development of sutural length (half length) in relation to the area of whorl (half area of the whorl section)in each specimen are plotted. Santonian Damesites damesi, which shows the concordant value in the trendof the Cenomanian-Turonian lineage, is also shown for comparison. In inlet, UC: Upper Cenomanian, L:
Lower Turonian Inoceramus labiatus zone, N: lower Middle Turonian Inoceramus hobetsensis nonsulcatuszone, H: upper Middle Turonian I. hobetsensis hobetsensis zone, T: Upper Turonian Inoceramus teshioensis zone, A: Lower Santonian Inoceramus amakusensis zone. 0.703-0.950: growth rate of sutural length
in relation to the area of the whorl section.

896.
L
50.0

Evolution of desmoceratine ammonoids

4

403

8

10.0

1.0
0.950

0.771
T. SUICOSTATUS

0.1'--_ _ _
L
50.0

~~

___

~~

___

~

-O.DAMESI_ _ _...J

3

7

10.0

1.0
0.904
T. SUICOSTATUS

T. MATSUMOTOI

0.1'-----~~--------~----'

L ~----------------------------~-,
50.0

2

6

10.0

1.0

0.1 L - - -____

~

0.125

0.113

O. JAPON1CUM

T. MATSUMOTol___________________...J

L r---------------------~--------_,

50.0

5

10.0

1.0

0.703

0.840

0.JAPON1CUM

1. SUICOSTATUS

O.l~---__:"':":'---~----~---....J

0.01

0.10

1.00

10.00

0.01

0.10

1.00

10.00

404

Hiromichi Hirano et al.

(Raup et al., 1973) has to be considered.
But it is also necessary to consider whether or
not such a contemporaneous extinction is a
result of a deterministic process. Even if
Cretaceous age boundaries do not coincidewith eustatic sea level changes, changes inmarine morphology caused by local tectonic
movements are still important factors causingchanges in local marine faunas. Species-area
hypotheses as adovocated by Schopf (1974)
and Simberloff (1974), and as discussed by
Gould (1977), can also be applied on various
scales ranging from world-wide to local.
Also, eustatic extinction/speciation models(Hallam, 1978, 1984, 1987) are applicable forvarious scales.
Comparison of the sedimentary and faunal
successions in the Yezo Supergroup with thefactors mentioned above reveals the importance of the oceanic anoxic event at the
Cenomanian/Turonian boundary and theregression and transgression at the Turonian/
Coniacian boundary.
Black shale beds of 5 m in thickness at the
Cenomanian/Turonian boundary are widely
recognized in the Yezo Supergroup (e.g.,
Obira = Tappu, Kotanbetsu, Ashibetsu, Ikushunbetsudake and Oyubari areas) by us.
Upper Cenomanian inoceramids are obtained
from calcareous concretions in the underlying
grey mudstone beds which are frequently
intercalated by sandstone beds. In the blackshale beds, however, there are neither calcareous concretions nor marine molluscs. The
black shale beds are overlain by alternating
grey mudstone with sandstone beds, fromwhich Turonian ammonoids and inoceramids
bearing calcareous concretions occur at about
the 50 m higher level than the black shale.
Alth6ugh more detailed investigation isunder progress, in the meantime the presenceof this black shale is interpreted to indicate
the oceanic anoxic event (OAE) at the
Cenomanian-Turonian boundary. Therefore, we regard that the Cenomanian D. (P.)
japonicum died out at the OAE and T. subcostatus phyletically speciated in the surviv-

ing small populations. At the time of speciation the habitat of the lineage became limited
to the western shallower waters. It is uncertain whether T. subcostatus evolved throughimmigration of surviving populations from
offshore to nearshore waters or from isolated
small populations which were left in theshallower waters.
Late Turonian is the age of a world-wide
regression, which is recognized also in thesedimentary succession of the Yezo Supergroup. Sedimentation of the Middle Yezo
Group ceased at about the TuronianConiacian boundary and that of the Upper
Yezo Group began with the Coniacian transgression.
T. matsumotoi speciated from isolated
small populations which were left in theshallower waters in the phase of a world-wide
regression. The habitat of T. matsumotoi isin the shallower waters of which bottom isshallower than the intense storm wave base.
T. matsumotoi and T. subcostatus which
inhabited offshore waters never co-occur andthus allopatric. At the present we regard
both two species died out at the end Turonian. Some Damesites species which may
be related to these two species occur in theConiacian onward, and the phylogenetical
relation between them will be the subject for
future next investigations.
Conclusions
I. Desmoceras (Pseudouhligella) japonicum existed throughout the Cenomanian,during which the protoconch size and growthratio of the radius length in relation to thevolution increased. On the other hand, thesimple ratio U /D and the growth ratio of theumbilical radius in relation to the volution
decreased. The growth ratio of breadth inrelation to the volution and the simple ratio
B/H did not change, and was stable.
2. There is an overlap of biometric characters between D. (P.) japonicum of theUpper Cenomanian and T. subcostatus of the896.

Evolution of desmoceratine ammonoids

Lower Turonian. The comparatively stronger ribbing, the ventral anterior projection of
subcostae and the smaller adult size are
unique to T. subcostatus. Both species havetheir main distribution in and around Japan,
and T. subcostatus mostlikely evolved fromD. (P.) japonicum at about the Cenomanian/Turonian boundary.
3. Tragodesmoceroides subcostatus, following its evolution from D. (P.) japonicum,
was morphologically stable in qualitative andbiometric terms throughout the duration of
the Turonian. The speciation of T. subcostatus from D. (P.) japonicum seems to havebeen in harmony with the punctuated equilibrium hypothesis.
4. Speciation occurred in T. subcostatus
by the Middle Turonian, and T. matsumotoi
arose. These taxa were clearly allopatric,
and the latter inhabited shallower waters,
which is characterized by some storm deposits
in the Obira and Oyubari areas. Growthratios of the radius length and the breadth inrelation to the volution are different between
the two species, and the adult size of T.
matsumotoi is smaller than that of T. subcostatus.
5. T. subcostatus was morphologicallystable throughout, with no temporal fluctuation around an average, except for one parameter (a simple ratio, U /0) mentioned earlier
and there is no transitional form between thetwo species of Tragodesmoceroides. There isa small possibility of polymorphism becauseof the habitat segregation of these two species.
Thus migration from offshore to shallower
waters took place instantaneously in the geological sense.
6. The timing of speciation of T. subcostatus from D. (P.) japonicum and that of T.
matsumotoi from the former is in accordancewith oceanic events, with an oceanic anoxic
event for the former and a marine regression
for the latter.
7. The lineage of T. matsumotoi via T.
subcostatus from D. (P.) japonicum has anincreasing rate of the sutural length in rela-405

tion to the area of the whorl section. That is,
the sutural complexity accelerated with time.
8. The present lineage also shows adecreasing adult size with time. In accordance with this trend the habitat changed
from deeper waters to changeable shallower
waters step by step.
Acknowledgements

As an extension of this research project, T.
Shiroki for 1978, H.Okaue for 1979, T.
Okamoto for 1982, K. Hattori for 1983, T.
Nitta for 1984, and Y. Takauchi and T.
Kondo for 1985 have studied some desmoceratid ammonoids under the supervision of thefirst author. Prof. Emer. T. Matsumoto gave
invaluable advice to one of the authors,
Hirano. Dr. G.R. Chancellor of Peterborough, Dr. W.J. Kennedy of Oxford, Prof. A.
Hallam of Birmingham and Prof. R.A. Reyment of Uppsala helped us with linguistic
improvement of the early draft of this paperand critical discussion. Dr. G.R. Stevens of
the New Zealand Geological Survey, Lower
Hutt helped us to complete this paper.
Grant-in-Aid for Scientific Research of the
Ministry of Education, Science and Culture(0, No. 364286 for 1978; C, No. 57540464
for 1982; C, No.61540577 for 1986 and1987), Research Fund of the GeographicalSociety of Tokyo (for 1983 and 1986), andGrant-in-Aid for the Fundamental Researchof Waseda University (No. 58A-29 for 1983;
No. 59A-56 for 1984; No. 60A-46 for 1985 ;No. 61A-69 for 1986; No. 62A-79 for 1987 ;No. 63A-99 for 1988) were given to one of theauthors, Hirano. The authors express theircordial thanks to these people and organisations.
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facies of Hokkaido, Japan. Palaeontology, vol.
22, no. 3, p. 609-630.
- - , Hirano, H., Matsumoto, T. and Miyata, Y.,
1977: Stratigraphy of the Upper Cretaceous
deposits in the Obira area, northwestern Hokkaido. Sci. Rept. Dept. Geol., Kyushu Univ.,
vol. 12, no. 3, p. 181-202 (in Japanese with English abstract).
Tanaka, K., 1963: A study on the Cretaceous sedimentation in Hokkaido, Japan. Rept. Geol.
Surv. Japan, no. 197, p. 1-119, pis. 1-3.
- - and Sumi, Y., 1981: Cretaceous paleocurrents
in the central zone of Hokkaido, Japan. Bull.
Geol. Surv. Japan, vol. 32, no. 2, p. 65-127, pis.
1-6 (in Japanese with English abstract).
Tsushima, S., Tanaka, K., Matsuno, H. and Yamaguchi, S., 1958: Geological map sheet I: 50000"Tappu-district" with explanation. 74p., Geol.
Surv. Japan (in Japanese with English abstract).
Westermann, G.E.G., 1971: Form, structure andfunction of shell and siphuncle in coiled Meso-408

Hiromichi Hirano et al.

zoic ammonoids. Life Sci. Contr., Royal Ontario Mus., no. 78, p. 1-39.
Whiteaves, J.F., 1900: On some additional or imperfectly understood fossils from the Cretaceous
rocks of Queen Charlotte Islands, with a revised
list of the species from these rocks. Mesozoic
Fossils, vol. I, no. 4, p.263-307, Geol. Surv.
Canada.
Wiedmann, J., 1973: Evolution or revolution of

r&WlB!IUCTA~~ 7 A!IE~7 :/~T-1

ammonoids at Mesozoic System boundaries?
Bioi. Rev., no. 48, p. 159-194.
William, W.H., 1988: Paleoceanography: A review
for the GSA centennial. Geol. Soc. Amer.
Bull., vol. 100, p. 1934-1956.
Yabe, H., 1904: Cretaceous cephalopoda from Hokkaido. Jour. Coil. Sci., Tokyo, vol. 20, p. 1-45,
pis. 1-16.

r MO):lm{t: r&WlB!lEf.CO)~t*fr=H::'li, TA~ ~ 7 A!IE~O) 7:/ ~ T -1 r MiJ~~* L.. t::.o ~tl19*fi$O) B!IE~ciitr~#MljlUl¥1JO)-t\;~
C. ~:hG~~~J!llh' I? Ii., .: 0) T A ~ ~ 7 A!IE~O) t O)iJ~~~.i£:I±l-t Go .::h I? 0) ? '0,.i£:I±l!l!lilto)~~'~ / "?.=. 7 :/WlO) D. japonicum, D. ezoanum, 7-;>. - P .=. 7 :/WlO) T.

subcostatus K. ":)~ '-C, ± C. L.. -c:k6TiJl:to J: tf/J 'fit!rn 0) -tf":/ 7',1--Z- m~ '-C, ;t§)(tijj(;~WHJT
Z-±kG~~c.L..-C, *~O).D:lm~:toJ:tf*~~O)~~z-~.L..ko-t~b'0,

D.

japonicum c. D. ezoanum Ii., *"" 1:.rtWlrl3,z-)j c: -C.DO)'f;f;f,O)~{tlltJ: ~ '0 T. subcostatus Ii., D. japonicum c. -=O).'titz-~~'-c ]llltJ: <, r&~iJ' I?:lm{t L.. k t 0) c. ~;t I?:hGo i k, T. subcostatus t .:t"O)1:.#Wlrl3,z-)j c: -C.Dt;::'f;f~0)~{tii4!\li~'iJ~, 7-;>. - P .=.
7 :/Wlq:r~i "(·t;::~:5Nt L.. T. matsumotoi, n. sp. z-1:. c: t::.o D.japonicum, T. subcostatus,
T. matsumotoi O)~{t*~z-)j c: -C, ji~~O)~ ~ O)~~tl!ITOO;jJtt;::~~-t G ;t§~~ijj(;~Ii., i1Wi

i7z11IlJ! ~:h -C ~'G iJ~, ~:5t{to)":) cijj(;{;j>O)-tf"-1 ;(iJ~l,\jlZ:p L.., 1:.,'&,J¥lGO)*~mw.iJ~gg~O)~
J: IJ t;::~fbL..t::.o it::., '::hI?O)~O):5t{t~~WGli, i'ia].l!. i'ia~~i'iai$4!\Ii~~l;r*~c. ~-1~ :/ YiJ~-~-tG': c. iJ'l?, .: 0) J: ? tJ:i'iai$~!tc. O)~~t;::":)~'-C tIDfliC:k of!f~:@:
Jli. HIi$$PJ.!ffiJ*

Appendix

The statistics on which the description, figures (Figures 5-11) and discussion in the text based are shown in the following tabular forms (Tables 2-7).

896.
Table 2.

Evolution of desmoceratine ammonoids

409

Protoconch width of studied desmoceratine ammonites. Number of specimens (N), 95%, confidence interval (C.l.), standard
deviation (S.D.), coefficients of variability (C.V.) and observed
range (O.R.) are shown for each species of each zone.

Species[Obira area] .
T. matsumotoi
T. matsumotoi
T. subcostatus
T. subcostatus
T. subcostatus
T. subcostatus
D. japonicum
D. japonicum
D. ezoanum
D. ezoanum[Oyubari area]
T. matsumotoi
T. subcostatus
T. subcostatus
T. subcostatus
T. subcostatus
D. japonicum
D. japonicum
D. ezoanum

Zone

N

c.1.

S.D.

c.v.

O.R.

T
H
T
H

6
61
4
II
35
14
65
II
20

.634±.041.650±.011.629±.077.578±.045.573±.025.685±.027.765±.011.682±.053.767±.028
.557

.040
.041
.048
.068
.074
.046
.045
.080
.059

6.42
6.32
7.66
11.8
12.9
6.77
5.88
11.7
7.75

.579-.688.516-.689.571-.689.474-.660.397-.757.626-.794.625-.880.566-.821.647-.887234.655±.013.590±.109.599.594±.045.624±.034
.744
.580
.614

.031
.078

4.73
13.3

.610-.720.500-.680

.088
.038

14.7
6.04

.401-.722.566-.674.714-.803.478-.681

HN
S

C

CN
C

CN
H

T
H

I

HN

17
7
3
2
I

S
C

CN
CN

For abbreviation of zones, T: Teshioensis Zone, H: Hobetsensis hobetsensis Zone, HN: Hobetsensis nonsulcatus Zone, S: SaxonicusLabiatus Zone, C: Upper Cenomanian, CN: Lower Cenomanian. C.
I. =x±tO.05.S.D./IN
Table 3.

Relative growth ratios of whorl-radius in relation to the volution of studied desmoceratine ammonites. For abbreviations
see Table 2.

Species[Obira area]
T. matsumotoi
T. matsumotoi
T. subcostatus
T. subcostatus
T. subcostatus
T. subcostatus
D. japonicum
D. japonicum
D. ezoanum
D. ezoanum[Oyubari area]
T. matsumotoi
T. subcostatus
T. subcostatus
T. subcostatus
T. subcostatus
D. japonicum
D. japonicum
D. ezoanum

Zone

N

c.1.

S.D.

c.v.

O.R.

T

6
61
4
11
35
14
65
II
20

. 138±.002.139±.001.156±.006.158±.003.I56±.002.15H.005.I74±.002.I73±.007.189±.004
.188

.002
.004
.004
.005
.006
.009
.007
.011
.009

1.42
2.50
2.59
3.00
3.84
5.86
4.06
6.21
4.90

.137-.142.131-.145.150-.159.150-.163.143-.170.146-.174.147-:187.153-.185.175-.210

H
T
H

23
4

.003
.005

2.39
3.23

.133-.145.153-.165

HN

17
7
3
2

.138±.001.158±.007.161.15H.003.157±.003
.176
.162
.156

.005
.003

3.16
2.10

.147-.165.153-.163.168-.179.153-.171

H

T
H

HN
S

C

CN
C

CN

S
C

CN
CN

I

Hiromichi Hirano et al.

410

Table 4.

Relative growth ratios of whorl-breadth in relation to thevolution of studied desmoceratine ammonites. For abbreviation see Table 2.

Species[Obira area]
T. matsumotoi
T. matsumotoi
T. subcostatus
T. subcostatus
T. subcostatus
T. subcostatus
D. japonicum
D. japonicum
D. ezoanum
D. ezoanum[Oyubari area]
T. matsumotoi
T. subcostatus
T. subcostatus
T. subcostatus
T. subcostatus
D. japonicum
D. japonicum
D. ezoanum

Table 5.

Zone

N

C.l.

S.D.

c.V.

O.R.

T

6
61
4

.118±.003.117±.001.129±.003.133±.004.133±.003.132±.004.I41±.002.I41±.006.133±.003
.156

.003
.005
.002
.007
.009
.006
.006
.010
.007

2.17
4.41
1.60
5.07
6.61
4.82
4.03
6.95
5.28

.144-.122.103-.126.127-.132.122-.142.117-.155.119-.139.122-.158.126-.154.123-.152.115±.002.131±.005.131.134±.005.133±.009
.140
.129
.132

.005
.004

3.98
2.88

.101-.124.126-.134

.009
.010

6.83
7.17

.107-.146.123-.151.131-.150.123-.134

H
T

H
HN
S

C
CN
C
CN
H
T

H
HN
S

C
CN
CN

II

35
14
65
II

20

23
4
17
7
3
2
I

Relative growth ratios of whorl-umbilical radius in relation to
the volution of studied desmoceratine ammonites. For abbreviations see Table 2.

Species[Obira area]
T. matsumotoi
T. matsumotoi
T. subcostatus
T. subcostatus
T. subcostatus
T. subcostatus
D. japonicum
D. japonicum
D. ezoanum
D. ezoanum[Oyubari area]
T. matsumotoi
T. subcostatus
T. subcostatus
T. subcostatus
T. subcostatus
D. japonicum
D. japonicum
D. ezoanum

Zone

N

c.1.

S.D.

c.V.

O.R.

T

6
61
4

.050±.005.060±.003.087±.022.085±.006.090±.007.074±.016.078±.006.096±.022.099±.013
.100

.005
.011
.016
.008
.019
.029
.024
.034
.029

9.72
18.5
18.1
9.74
21.2
38.7
30.3
34.9
29.1

.041-.054.041-.098.071-.101.075-.102.045-.143.033-.130.039-.148.027-.139.058-.173.059±.007.I04±.029.079.113±.01O.115±.003
.088
.106
.080

.016
.021

27.3
20.0

.034-.097.084-.131

.020
.029

18.1
24.8

.091-.165.092-.175.077-.095.098-.114

H
T

H
HN
S

C
CN
C
CN
H
T

H
HN
S

C
CN
CN

II

35
14
65
II

20

23
4
17
7
3
2

896.
Table 6.

411

Simple ratios of breadth to height of whorl at the fourth whorlof studied desmoceratine ammonites. For abbreviations see
Table 2.

Species[Obira area]
T. matsumotoi
T. matsumotoi
T. subcostatus
T. subcostatus
T. subcostatus
T. subcostatus
D. japonicum
D. japonicum
D. ezoanum
D. ezoanum[Oyubari area]
T. matsumotoi
T. subcostatus
T. subcostatlls
T. subcostatus
T. subcostatlls
D. japonicum
D. japonicum
D. ezoanum

Table 7.

Evolution of desmoceratine ammonoids

Zone

N

c.l.

S.D.

c.y.

O.R.

T

6
61
4
II
35
13
59
9
18

1.12±.029
1.12±.001
1.05±.042
1.07±.043
1.08±.016
1.05±.041
1.06±.014
1.05±.058.792±.034
.760

.029
.039
.031
.065
.048
.069
.055
.078
.068

2.57
3.44
2.90
6.12
4.45
6.57
5.17
7.41
8.62

1.09-1.17
1.00-1.23
1.02-1.09.957-1.16.948-1.17.889-1.19.923-1.15.970-1.24.627-.923

23
4
I
17
7
3
2

1.12±.016
1.08±0.68
1.07
1.10±.016
1.12±.019
1.01
1.03
1.06

.036
.049

3.21
4.54

1.07-1.24
1.01-1.13

.032
.021

2.90
1.91

1.02-1.15
1.09-1.15.992-1.02
1.01-1.05

H
T

H
HN
S

C
CN
C
CN
H
T

H
HN
S

C
CN
CN

Simple ratios (%) of umbilical radius to whorl radius at the
fourth whorl of studied desmoceratine ammonites. For abbreviations see Table 2.

Species[Obira area]
T. matsumotoi
T. matsumotoi
T. subcostatus
T. subcostatus
T. subcostatus
T. subcostatus
D. japonicum
D. japonicum
D. ezoanum
D. ezoanum[Oyubari area]
T. matsumotoi
T. subcostatus
T. subcostatus
T. subcostatus
T. subcostatus
D. japonicum
D. japonicum
D. ezoanum

Zone

N

C.I.

S.D.

C.Y.

O.R.

T

6
61
4
II
35
13
59
9
18

18.0±2.1918.4±.53
16.0± 1.11
16.1±.76
16.4±.61
1O.9±.83
11.8±.30
14.9± 1.77
13.0±.76
17.6

2.19
2.08
0.80
1.14
1.79
1.38
1.14
2.35
1.53

12.2
11.3
5.01
7.08
10.9
12.7
9.69
15.7
11.8

15.4-21.5
14.5-22.9
15.3-16.9
14.3-17.5
12.5-21.3
8.4-14.0
9.4-14.0
12.2-20.0
10.3-17.3

234

17.6±.74
17.3±3.61
18.4
17.5±.94
18.7±.90
12.8
17.9
19.7

1.72
2.61

9.77
15.1

13.4-20.7
14.8-20.5

1.84
1.00

10.5
5.35

15.1-21.8
17.4-20.1
12.7-12.9
15.4-20.4

H
T

H
HN
S

C
CN
C
CN
H
T

H
HN
S

C
CN
CN

I

17
7
3
2

Trans. Proc. Palaeont. Soc. Japan, N.S., No. 157, pp. 412-429,6 Figs., April 30, 1990

897.

MIOCENE ISOCRINIDAE (STALKED CRINOIDS) FROM JAPANAND THEIR BIOGEOGRAPHIC IMPLICATION*
TATSUO 011
Geological Institute, University of Tokyo, Hongo, Tokyo 113, Japan

Abstract. Three isocrinids, Teliocrinus springeri (Clark), Isocrinus sp. and Isselicrinussp., are described from the late Early to early Middle Miocene of Japan, and their biogeographic implications are discussed. Teliocrinus had been represented only by a living species
distributed in the Indian Ocean, and this discovery not only extends its stratigraphic recordback to the Miocene but also widens its geographic distribution to the western Pacific region.
Isocrinus sp. is based on many disarticulated columnals and is very similar to Oligocene
Isocrinus oregonensis and I. nehalemensis from western Oregon. Isselicrinus sp. is based on
fragmentary columnals, representing one of the latest occurrences of this genus.
A relatively striking turnover of the isocrinid fauna is presumed to have occurred in thewestern Pacific during the period between the late Early Miocene and Recent. This turnoverincludes the disappearance of Teliocrinus, Isocrinus and Isselicrinus from the western Pacific,
and the introduction of Metacrinus and Saracrinus into this area. As a possible explanation for this, the northwestward movement of oceanic plates and a collision of a part of
Gondwana (Australia/New Guinea) to the Eurasia continent are considered, which probably brought Metacrinus to the western Pacific region and an appearance of a barrier
separating the deep-water isocrinid fauna into two provinces. Shallow water dwellers likemany species of comasterid comatulids in the Indo-Pacific region are less subjected to such
faunal separation.
Key words.

Crinoidea, Miocene, paleobiogeography.

invertebrates generally are very scarce, andpaleoecological studies of benthic faunas forthe most part remain to be conducted.
Within such deep environments, echinoderms
are sometimes proportionally dominant withrespect to molluscs. However, because of
their comparatively low preservation potential, fossil echinoderms from deeper environments have not yet been adequately investigated.
The present papaer presents systematic
descriptions of three species of Isocrinidae(Teliocrinus springeri, Isocrinus sp., and Isselicrinus sp.) from four different Japanese
Miocene localities, and their biogeographic
and evolutionary significances are also assessed in some detail.
Thus far, Pentacrinus ariakensis Yoko-

Introduction

Miocene marine deposits are widely distributed in many local areas of Japan.
Recent paleontological work has focused
mostly on biostratigraphy based on· planktonic foraminifers and other microfossils, or
paleoenvironmental and ecological analysis
based on molluscan fossils from intertidal toshelf environments. These investigations
have revealed precise spatio-temporal distributions of several molluscan assemblages inand around the Japanese Islands (Itoigawa,
1981, Chinzei, 1986, among others). In
deposits representing deeper environments,
such as bathyal zones or continental slopes,'Received July 27, 1989; accepted December 20, 1989
412

897.

Miocene Crinoids from Japan

yama is the only stalked crinoid so far described from the Tertiary of Japan (Yokoyama, 1911; Nagao, 1928). Sieverts (1932)
described Balanocrinus sp. and Metacrinus
sp. from the upper Miocene of Borneo andfrom the Pliocene of Sulawesi, respectively.
Wanner (1938) described Balanocrinus sundaicus from the lower Miocene of Madura
Island, north of Java. Klikushin (I 977a)
subsequently assigned the above two speciesof Balanocrinus to Isselicrinus; the revision
seems appropriate owing to the diagnostic
features of the columns. Klikushin (l977a)
further pointed out a possibility that Pentacrinus ariakensis Yokoyama from the
Paleogene of western Japan be placed in a
species of Isselicrinus. Nevertheless, the dataon Tertiary Isocrinidae from the western
Pacific region remain scarce. Though still
speculative, the new occurrence of Miocene
isocrinids from Japan will provide importantdata on the biogeography of the Isocrinidae
in this region.
The Recent isocrinid faunas of the Pacificshow clear differences from those of the Indian Ocean. Each ocean is inhabited by an·almost independent generic and species composition: Metacrinus in the Pacific andTeliocrinus in the Indian Ocean. It is important to consider how and when such characteristic faunas of each ocean became established, with respect to paleobiogeography andpast plate movements. Previous discussions
on paleobiogeography of marine invertebrates, including those of the stalked crinoids,
have tended to emphasize origin and migration or dispersal rather than the concept ofvicariance. Among the paleobiogeographic
interpretations of stalked crinoids, Roux
(1979, 1987) proposed that western Pacificand Atlantic Isocrinidae originated from acommon Mesozoic Tethyan ancestral fauna("faune Mesogee"), and migrated toward thepresent distributions. A comparison of thefossil records of the Tertiary Isocrinidae withthe distribution of Recent species provides
data that help to determine the relative merits413

of the two concepts, dispersal and vicariance.
Recently, the paleobiogeography of Southeast Asia has attracted increasing attention
with respect to plate tectonics. The classic
work by Wallace on the biogeography of the
Malay archipelago has been reviewed in relation to continental movement and collision ofAustralia/New Guinea with Eurasia, and"Wallace's Line" has been reinterpreted as aremnant of an ancient suture between thecontinents (Audley-Charles, 1981: Hayami,1987). The interpretation of Wallace's Line
as a faunal boundary was based mostly onland animals and plants. Shallow-water
marine invertebrates are thought to have enjoyed relatively free interchange between thewestern Pacific and the Indian Ocean. For
example, Ekman (1953) showed many examples of marine animals that possess wide
distribution both in the western Pacific andthe Indian Ocean. Thus, the distribution
pattern of the marine invertebrates is thought
to exhibit less pronounced faunal boundaries
in this region.
Material and occurrence
Three isocrinid species were collected fromfour different areas; Morozaki, Shobara,
Ichishi and Hota in Honshu Island (Figure1); each area was in a sedimentary basin thatwas separated from the others by topographic
basement relief. Stratigraphic studies basedon planktonic foraminifers, diatoms and pteropods (Shibata and Ishigaki, 1981 ; Koizumi,
1981 ; Ito, 1982; Doi, 1983; Watanabe,1988), as well as paleomagnetic polarity(Hayashida and Ito, 1984; Hayashida, 1985,
1986) indicate that crinoid-bearing formations of Morozaki and Ichishi are late Early
Miocene in age (N. 7-8 and N. 8 of subdivision by Blow (1969), respectively). The
crinoid-bearing horizon ofthe Bihoku Groupin Shobara has not yet been correlated precisely with microfossils, but the occurrence ofKadonosawa-type molluscs such as Geloina
yamanei and Vicarya callosa japonica from a.j:>.
.j:>.

ISE BAY~c::;:;:::c

S-:

LOC.9.<J'
..Il
/)

....

o

1km

o
Figure 1. Localities of the Miocene crinoids from Japan. A. Teliocrinus springeri from the Yamami Formation, MorozakiGroup (Locs. 1-5). B. lsocrinus sp. from the upper member of the Bihoku Group (Locs. 6,7). C. lsselicrinus sp. from theYakuoji Member, Katada Formation, Ichishi Group (Loc. 8). D. lsselicrinus sp. from the Ohkatabira Formation, Awa Group(Loc.9).

897.

Miocene Crinoids from Japanslightly lower horizon (Okamoto and Terauchi, 1974) suggests that the age would be N.
8-N. 9; i.e., late Early to early Middle
Miocene. The fossil locality at Ohkatabira(Loc.9) was previously assigned to an unnamed subdivision of the Hota Group (Mitsunashi et al., 1984). More recently, it has
been correlated to the Ohkatabira Formationof the Awa Group; early Middle Miocene,
N. 9-10 (Watanabe, 1988). This horizon is
stratigraphically equivalent to the lower partof the Amatsu Formation which is widelydistributed in the southern part of Boso Peninsula.
The specimens described in this study arehoused in the following institutions: Mizunami Fossil Museum (with prefix MFM), andUniversity Museum, University of Tokyo(UMUT), except for the specimens of Isocrinus sp. from Shobara which are partly
housed in the University Museum (UMUT
CE 18692-18699) and the private collectionof S. Hirose.
1. Teliocrinus springeri (A.H. Clark) Eight specimens were collected from the
Yamami Formation of the Morozaki Group(Figure lA). This formation is characterized by mudstone-dominated turbidites andmudstone, and is thought to represent anoffshore environment (Shikama and Kase,
1976; Shibata, 1977).
Specimen 1 (MFM 38051) occurred withina thin fossiliferous layer, 15 cm above thebase of a thick turbiditic siltstone (2 m) of thelower part of the Yamami Formation (Loc.
1). The turbidite bed consists mostly ofsilt-sized acid volcaniclasts, with graded bedding at the base. The crinoid specimen occurred a~sociated with unidentified irregularsea urchins, mostly fragmentary. Fossils are
restricted to this thin layer.
Specimen 2 (UMUT CE 18691) occurred inconglomeratic sandstone exposed at a roadcut near Hajikami (Loc. 2). This horizon iscorrelated to the lower part of the Yamami
Formation. The sandstone is poorly-sorted,
containing intraclasts of pebble- to granule-415

sized mudstone, fragments of ophiuroids, andindeterminable echinoderm ossicles.
Specimen 3 (MFM 38052) occurred at thebase of a thick turbidite bed (4 m) exposed ata large cut beside a farm in Yamami (Loc. 3).
The horizon is correlated to the middle partof the Yamami Formation. The turbidite
bed consists of white pumiceous fine-grained
tuff. At the locality, several beds of this tuff
show graded bedding, with distinct parallel
lamination near the base, and are interbeddedwith massive gray mudstone. These
tuffaceous turbidites flowed into a deep environments under high-energy conditions, andwere deposited rapidly. The fossil horizon
consists of many plant fragments, associatedsporadically with well-preserved fish skeletons, small ophi uroids and asteroids.
Specimen 4 (MFM 38053) occurred near
the base of a turbiditic sandstone bed (15 cm),
associated with abundant fragmentary molluscan shells, in the upper part of the Yamami
Formation (Loc.4). The sandstone iscoarse- to medium-grained, contains intraclasts of mudstone, and shows conspicuous
load casts at the base. All fossils were poorly preserved; the shells were completely dissolved, and concentrated in the lowermost
part of the turbidite bed. They consist of
Dentalium (Fissidentalium) yokoyamai andindeterminable gastropods.
Specimens 5 through 8 (MFM 38054A38054D) occurred on a single slab of finegrained sandstone exposed on the Utsumi
coast (Loc.5). These specimens are wellpreserved and the skeletons are almost intact,
although the calcareous parts were entirely
dissolved. This slab is thought to haveoriginated from the sandstone of the samelithology exposed on the coast; the horizon
is in the upper part of the Yamami Formation.
All the well-preserved specimens except for
those from Locs. 2 and 5 were collected near
the base of turbidite beds. The outcrop at
Loc. 5 consists of massive fine-grained sandstone and a small amount of mudstone. The

416

Tatsuo Oji

slab from the Loc. 5 may also have been
derived from a turbiditic sandstone layer,
because the lithology is very similar and thestratigraphic position is correlatable to thoseof the locality of Specimen 4. The excellent
state of preservation, despite their occurrencein turbiditic layers, suggests that these fragile
crinoid skeletons were not subjected to substantial transport or disturbance. The specimens were probably subjected to rapid burial
by turbidity flow while they were still alive,
because they suffered almost no post-mortem
disarticulation. Most notably, specimen 1
shows several arms disarticulated only at thecryptosyzygial articulations (Figures 4-4; 5D), strongly suggesting that the specimen wasburied while still alive, and autotomized its
arms at the articulations.
2. Isocrinus sp.- 318 specimens, all consisting entirely of fragmentary columns andcolumnals, were collected from a road cut at
Shinchiku, Shobara, Hiroshima Prefecture(Figure lB, Loc. 6). Several disarticulated
columns of the same species occurred fromgray massive siltstone exposed on the riverfloor of Togo-gawa (Loc. 7), 2.2 km southwest of Loc. 6.
The Bihoku Group in Shobara lies unconformably on a basement of acidic tuff, andconsists of lower (approx. 26 m) and upper(more than 13 m) members (Okamoto, 1987).
Isocrinus sp. occurred in the upper member.
The lower member consists of poorly-sorted
conglomeratic sandstone, and contains intertidal to shallow-water molluscs and otherfossils, including Vicarya callosa japonica
Yabe and Hatai, Tateiwaia yamanarii (Makiyama), Glycymeris sp., Crassostrea sp.,
Geloina yamanei Oyama and Astryc/ypeus sp.
These fossils include Kadonosawa-type tropical and subtropical molluscs, characteristic of
tidal flat and intertidal environment in theearly Middle Miocene. The upper member
consists predominantly of dark gray silty
shale, with intercalations of fine-grained sandstone. It is less fossiliferous than the lower
member, and contains disarticulated col um-

nals and columns of Isocrinus sp., Dentalium(Fissidentalium) yokoyamai, Acila sp.,
Lucinoma sp., turrid gastropods, a foraminifer Dentalina sp., galatheid crustaceans,
and an ostracod Cytherella sp. (Yaj ima,
1988). Columns of Isocrinus were especiallyabundant in a patch near the base of thelower part. Of the species present,
Dentalium yokoyamai, also lives in Recent
waters around Japan, and is regarded as an
occupant of the "bathyneritic zone (from 100120 to 200-250 m)" in the outer shelf to upper
bathyal slope in southern Japan (Oyama,1973). Cytherella sp. is considered a warmwater species and currently lives along the
Pacific coast of southwest Japan (Yaj ima,
1988). Probably rapid transgression had
occurred during the deposition of the lower
and/or the upper parts.
3. Isselicrinus sp.- Two fragmentary columns (MFM 38055 and 38056), were collectedfrom bioturbated siltstone in an abandoned
quarry in Katada (Figure I C, Loc. 8). The
horizon is correlated to the Yakuoji Member,
Katada Formation, Ichishi Group (Shibata,1970). The Yakuoji Member consists mostlyof alternating beds of sandstone and siltstone,
and slump deposits of the alternating beds
and intraclasts. Sandstone beds of the alternating beds are mostly turbidites, showing
graded bedding at the bases.
Five fragmentary columnals (UMUT CE
18700-18704) were also collected from fossiliferous mudstone at a quarry in Ohkatabira, Kyonan-cho, Chiba Pref. (Figure ID,
Loc. 9). The most dominant fossils at Loc. 9
are disarticulated but well-preserved
Glycymeris cisshuensis, and a small numberof Flabellum sp. Crinoid columnals are scattered in gray mud with granules of chert.
Interpretation of paleozoogeographyof the Pacific Cenozoic Isocrinidae
Information about the distribution of Isocrinidae during the Cenozoic time continues
to be insufficient. However, important infor-

*~oMetacrinus & Saracrinus
Endoxocrinus
Hypalocrinus
Teliocrinus
Isselicrinus®

o Isocrinus
E.-M. MIOCENEOLIGOCENE....
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Figure 2. Occurrence of the Cenozoic Isocrinidae and the· approximate position of continents at each time. Paleogeographic maps were based on Smith, Hurley and Briden (1981), with slight modification. A: Oligocene. B: Early to Middle
Miocene. C: Recent. Note clear faunal separation of isocrinid fauna between today's Pacific and the Indian Ocean.
-I>-

....,

418

Tatsuo Oji

mation on the biogeography of isocrinids isnevertheless contained in several scattered
records of occurrences of isocrinids from the
Tertiary. These records include recent discoveries of Tertiary isocrinids that haveextended the stratigraphic records of three
genera back to the Tertiary. These genera
had previously been considered only as
Recent representatives in the Indo-Pacificregions.
Teliocrinus is the only isocrinid genus
found in the tropical area of the Indian
Ocean, and it is not distributed in otheroceans. Species of Metacrinus and Saracrinus characterize tropical to warm-temperatearea of the western Pacific, distributed dominantly from southern Japan to eastern Australia and New Caledonia (Figure 2C).
There are, however, a few exceptional distributions reported outside this area. Saracrinus nobilis was reported off the western
coast of Sumatra, (Doderlein, 1912). Saracrinus nobilis, Saracrinus angulatus andMetacrinus varians were recorded near thesouthern tip of Timor Island (DOderlein,
1907, Clark, 1932). Although species ofMetacrinus and Saracrinus have also beenreported from a few stations facing the Indian
Ocean, they are restricted to the area along thesouthern coast of the Greater and Lesser
Sundas. Therefore, Metacrinus and Saracrinus are principally regarded as Pacificelements, whereas Tellocrinus is an element of
the Indian Ocean.
During the Miocene, however, a considerably different generic composition of Isocrinidae is recognized in the western Pacific region(Figure 2B). In Japan, Teliocrinus wasfound in deep environments, based on its
representation in turbidite sequences and its
association with other deep-sea fauna. Other
isocrinids, including Isocrinus sp. and Isselicrinus, probably occupied shallower environments, such as the shelf-edge and upper slope.
Species of Isselicrinus were also found in the
Miocene of Borneo and the Madura Islands,suggesting a wide distribution at that time.

During the Miocene, there was presumably no
Metacrinus and Saracrinus, which are themost dominant genera in the Japanese waters
today (Oji, 1989). Therefore, a clear change
of isocrinid faunal composition must haveoccurred after the late Early Miocene.
Although of different age, three otherrecords of isocrinids from the Tertiary provide important data for the reconstruction of
isocrinid paleobiogeography. The first is an
occurrence of Metacrinus from the Eocene of
Seymour Island, Antarctic Peninsula (Rasmussen, 1979; Meyer and Oji, 1988). Thisoccurrence indicates that Metacrinus alreadyexisted as early as the Eocene, although it
presumably was not distributed in the Pacificat that time. This genus has probably migrated to the Pacific and has diversified after
the Middle Miocene. Secondly, there is an
occurrence of two species of Isocrinus, I.
oregonensis and I. nehalemensis, in the
Oligocene near the Pacific coast of Oregon,
USA (Moore and Vokes, 1953). Isocrinus
sp. from Shobara described here is morphologically very similar, suggesting a strong
relationship to the Isocrinus species from
Oregon. These Isocrinus species existed during the Oligocene to Miocene, but have sincedisappeared from the Pacific. Finally, an
excellent specimen of Isocrinidae, which issimilar to Hypalocrinus, was recently discovered from the Eocene of northwest
Washington, USA (Franzen-Bengtson In
preparation). Hypalocrinus had also been
represented only by a recent deep-water
Pacific species, H. naresianus.
Figure 3 summarizes isocrinid occurrencesfrom the Indo-Pacific region in the Cenozoic.
Comparison of the distribution of isocrinid
faunas at different times leads to the following three hypotheses:(1) Teliocrinus has disappeared from the
Pacific, and is now found only in the Indian
Ocean. Isocrinus also disappeared from the
Pacific after Middle Miocene. Isselicrinus
had a wide distribution in the Miocene of thewestern Atlantic, western Tethys (Italy) and897.

RECENT
QUAT
PLiOC
MIOC
OLiGOC

Miocene Crinoids from JapanS PACIFICINDIAN 0

W PACIFIC

Teliocrinus

Metacrinus Hypalocrinus Endoxocrinus
,

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419

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I

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Isocrinus: Isselicrinus
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Figure 3. Schematic spatio-temporal distribution of Isocrinidae of the Pacific. A collision of Australia/New Guinea has probably brought Metacrinus into the Pacific region, and it has also established wide
epicontinental seas between the Pacific and the Indian Oceans, which has become a barrier to the isocrinid
faunas.

western Pacific (Borneo, Madura and Japan),whereas it has disappeared entirely since the
Miocene.
(2) Metacrinus already lived in the marginal seas of the Gondwana during the
Eocene, at least in an area of Antarctic Peninsula, and entered the western Pacific after the
Miocene.
(3) The recent distribution patterns of Isocrinidae show that there are almost no common species between the Pacific and the Indian Oceans. A significant barrier seems toexist along the archipelago in Indonesia.
According to a reconstruction of paleogeographic distribution of lands and oceans in
the Eocene to Miocene (Smith, Hurley andBriden, 1981), there was a wide opening ofocean, forming a part of the eastern Tethys,
between Eurasia and a part of Gondwana,connecting the present Pacific and the Indian
Oceans: Therefore, there was no distinct
barrier between the Pacific and the Indian
Oceans (Figure 2A). Such a wide passage
may have enabled the interchange of deep-sea
faunas like crinoids along its northern coast.
Teliocrinus had probably inhabited both the
Pacific and the Indian Oceans since the
Miocene. Subsequently, because of thenorthward movement of Australia/New
Guinea to Eurasia, this seaway has graduallyinterrupted to form an archipelago (AudleyCharles, 1981) and probably created a large
shallow shelf in this area. After the establishment of the archipelago and shallow seas
between the two oceans, and following immigration of Metacrinus, interchange of isocrinids may have become interrupted by thisbarrier; Teliocrinus was replaced by Metacrinus in the Pacific and a characteristic fauna
has been formed in each ocean.
As for the comatulid (stalkless) crinoids, A.
H. Clark (1937) pointed out a strong similarity between the western Pacific and the Indian
Ocean, noting: "The crinoid fauna of the
Indian Ocean is simply the progressively
depauperate western extension of the very richfauna that has its centre in the region of thelarge Malayan islands." (Clark, 1937, p. 103).
According to the compilation of comatulidsof Japan by Utinomi and Kogo (1968), morethan 30% of comasterid species of Japanesewater are also found in the Indian Ocean.
This figure clearly contrasts with the lack ofisocrinid species living widely in the bothoceans. Many of the comatulids live inmuch shallower water, and consequently, the420

Tatsuo Oji

897.

Miocene Crinoids from Japan

Indonesian and Malayan archipelagos andwide shelf area do not constitute a significant
barrier for such comatulids. The different
distribution patterns of isocrinids andcomatulids imply that such an archipelago
can be a barrier for only the deep sea fauna,
whereas it might not be a barrier for theshallow water fauna. Other than crinoids,
Ekman (1953) presented that many vertebrates and invertebrates living in shallow
waters have their distributions both in the
Pacific and the Indian Ocean. Further investigation on the deep-sea faunas in this region
will provide more information whether they
possess different patterns of distribution in
the both oceans or not.

Systematic description
Family Isocrinidae, Gislen, 1924
Genus Teliocrinus DOderiein, 1912

Synonym: Comastrocrinus

A.H. Clark,

1912.

Type species: Hypa/ocrinus springeri A.H.
Clark, 1909.

Diagnosis: An isocrinid with cryptosyzygial articulation in primibrachials and frequently with synarthry between first and second secundibrachials. First pinnule on first
secundibrachial of outer division and on
second secundibrachial of inner division.
Relatively long and slender cirri.
Remarks: Teliocrinus was firstly introduced as a monospecific genus for a species ofIsocrinidae from the Indian Ocean. Doderlein (1912) thought that this species, Teliocrinus asper, was a new species. In the same
year, A.H. Clark (1912) proposed Comastrocrinus for three species, one of which was
pre-described species, C. springeri (typespecies Hypa/ocrinus springeri, A.H. Clark,
1909), and two of which he thought were new,421

from the Indian Ocean; C. liliaceus and C.
ornatus. Later, A.H. Clark (1923) assigned
T. asper as the same species to T. springeri.
Therefore Comastrocrinus was replaced by

Teliocrinus.
According to a compilation of isocrinid
species by A.H. Clark (1923), Teliocrinus
consists of three species, all of which camefrom the Indian Ocean. A.H. Clark (1912)
discriminated Teliocrinus ornatus from T.
springeri only by its small size. Four specimens assigned to T.ornatus by A.H. Clark
were collected from the same station at which
T. springeri was also collected. T.ornatus
should be regarded as relatively young individuals of T. springeri. T. liliaceus was collected at two stations off Burma. Because of
the wide distribution of T. springeri from thewest coast of India to Burma and off the west
coast of Sumatra Island, the distribution of
T. liliaceus is included entirely in that of T.
springeri. T. liliaceus was distinguishedfrom T. springeri by its less prominent evertion of the distal end of the proximal brachials. This character may be considered as
intraspecific variation, because such variation
is often observed in a population of a single
species. H.L. Clark (1928) proposed anotherspecies, Teliocrinus monarthrus, based on asingle specimen from an unknown locality(off the northern coast of Australia ?).
According to H.L. Clark, this species isdistinguished by "having fewer internodals,much more spiny cirri, and only a single
segment in the IIIBr series". The number ofinternodal plates usually shows considerable
variation within a species Of Isocrinidae, andthis can not be a good criterion. As for thenumber of tertibrachiaIs, as long as there arefurther divisions distally, specimens of Teliocrinus kept in the Smithsonian Institution
have four (one case in the specimen USNM
35995, one case in USNM 36068), or three~ Figure 4.
Teliocrinus springeri (A.H. Clark) from the Morozaki Group. 1: Specimen 4 (MFM
38053) from Utsumi, Loc. 4. X 2.4. 2: Specimen 7 (MFM 38054C) from Utsumi coast, Loc. 5. X 1.7.
3: Specimen 2 (UMUT CE18691) from Hajikami, Loc. 2. X 1.65. 4: Specimen I (MFM 38051) from
Loc. I. X 1.8. 5: Specimen 5 (MFM 38054A) from Utsumi coast, Loc. 5. X 3.8.

~

D

N

E

N

;
~

~

0:;
:;:::

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S-:

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,

Figure 5. Camera lucida drawings of Teliocrinus springeri (A.H. Clark) from the Yamami Formation, Morozaki Group. A: Specimen 3(MFM 38052) from Yamami (Loc. 3). B: Specimen 5 (MFM 38054A) from Utsumi coast (Loc. 5). C: Specimen 6 (MFM 380548) from Utsumi
coast (Loc. 5). D: Specimen I (MFM 38051) from Loc. I. E: Specimen 8 (MFM 38054D) from Utsumi coast (Loc. 5).

897.

Miocene Crinoids from Japan(three cases in USNM 35995) tertibrachials.
Six specimens collected by the Siboga Expedition (Doderlein, 1912) shows wider variationin the number of tertibrachials: one (threecases), two (four cases), three (three cases) and
four (two cases). In the other species like
Endoxocrinus parrae where intraspecific variation is recognizable owing to a large numberof specimens, the number of plates in a brachitaxis shows rather wide variation. T.
monarthrus would therefore be better treatedas a synonym of T. springeri.
From the viewpoint of ligamentary articulation between the brachials, Teliocrinus isincluded as a member of the new group (Oji,1985), which is characterized by having
cryptosyzygy instead of synarthry in primibrachials. However, at least some of the proximal ligamentary articulations are synarthrial,
especially in IIBrl-2. The common presenceof a synarthry within species of the new groupsuggests that Teliocrinus, as Nielsenicrinus,
has features intermediate between the twogroups.
Geographic and stratigraphic distribution:
Late Early Miocene (Japan) and Recent (Indian Ocean, from the west coast of Indian
Peninsula through Burma to the southerncoast of Sumatra).

Teliocrinus springeri (A.H. Clark, 1909)
Figures 4-1-4; 6-1-3
Hypalocrinus springeri A.H. Clark, 1909
Teliocrinus asper Doderlein, 1912
Comastrocrinus springeri A.H. Clark, 1912
Comastrocrinus liliaceous A.H. Clark, 1912
Comastrocrinus ornatus A.H. Clark, 1912
Teliocrinus springeri, Roux, 1977
Teliocrinus springeri, Rasmussen, 1978

Diagnosis: As for the generic diagnosis.
Description: Specimen I : Basals are small,rounded and separated on dorsal surface.
Radials are high, three fourth as high as
width. First primibrachial (IBrl) is wider
than high, showing cryptosyzygial articula-423

tion with second primibrachial (IBr2). IBr2
is first axil-Iary, modified pentagonal on dorsal surface. In three rays, secundibrach consists of two brachials in IIBrT rayon dorsal
view, and they give rise to tertibrachs, whereas secundibrach on right side shows no branching. Secundibrachs on right side presumably have synarthry (at least in two rays).
Secundibrachs on right side have cryptosyzygy between third and fourth brachials.
No other division is observed. Finials taper
gradually toward tips. Cryptosyzygies are
distributed at an approximately regular interval. Most cryptosyzygies are disarticulated,and hypozygal and epizygal are detachedslightly. Only very proximal part of column
is preserved. This part is very cirriferous,
some cirri reach as far as secundibrach.
Specimen 2: This specimen consists onlyof a long column. Proximal column hasradial pores. Most proximal columnals arevery thin and pentalobate in section.
Medium to distal portion of column issmooth on surface, rounded pentagonal insection. Nodals are slightly higher thaninternodals. Cirral socket is large, occupying
almost entire height of nodal and interferinghypozygal as a depression. Number of internodals is 2+, 1O?, II, 11, 12 and 9+ fromproximal to distal internodals. Columnal
articulation shows typical symplexy with
distinct crenulae. There is gradual transitionin size of crenulae from adradial to marginal
position. Total number of crenulae is four
to five around one petal. There is no conspicuous radial groove. Petal is subguttiform and it possesses galleried stereom
with rounded mesh.
Specimen 3: This specimen consists of acrown and column. Detailed character andmorphology of proximal crown are unknown
because of the poor state of preservation.
Number of distal arms is at least six, probably
more. Internodals are presumably seven oreight, according to the distribution of fragmentary cirri. Cirri are short and slender.
Specimen 4: This specimen consists of a

424

Talsuo Oji

897.

Miocene Crinoids from Japan

calyx, proximal arms and a proximal column.
Basals are relatively large and rounded, separated on surface. Radials are large, threefourths as high as width, pentagonal in dorsal
surface. Distal edge of radial is smooth andslightly convex, giving straight muscular articulation with first primibrachial. First primibrachial (IBrI) is cylindrical, slightly narrower than radial. IBr2 is axillary. Articulation IBrI-2 is presumably cryptosyzygial,
giving straight suture on dorsal surface.
There are two secundibrachs, each possessing
two brachials. At least one IIBrI-2 is possibly synarthrial. IIBr2 is axillary. No further division is observable. Proximal columnals are alternating in height and width, andstellate in section. Radial pores between
columnals are observable at least up to fifthinternode.
Specimen 5: This specimen consists of acalyx, proximal arms and a distal arms.
Basals are moderate in size, rounded rhombic
and separated on dorsal surface. Radials arelarge, with rounded proximal and convex
distal edges. IBri is cylindrical and slightly
narrower than radial. IBr2 is axillary, pentagonal in dorsal surface. Articulation
IBrI-2 is presumably cryptosyzygial. Most
distal arms are at least 11 in number.
Specimen 6: Only poorly-preserved small
specimen with five arms impressed as a moldon sandstone. Arms are undivided except
for a pair of arms, which fork from primaxillary.
Specimen 7: Small-sized specimen withproximal to distal arms. Basals and radials
are scarcely preserved. IBri is cylindrical,
wider than high. IBr2 is axillary, low tri-

425

angular on dorsal surface. IIBrI-2 is presumably muscular. IIBr2-3 is cryptosyzygial.
Other cryptosyzygies are observed at lIBrJOII in one arm, IIBr 13-14 in the other. Distalarms have long and fine pinnules.
Specimen 8: Only long column, consists ofeight noditaxes. Number of internodals ineach noditaxis is 8 or more, 7,9, 7,9, 8, 8 and
7 or 8 from proximal to distal internodes.
Remarks: Specimens from the MorozakiGroup are safely assigned to Teliocrinus
Doderlein 1912 because they have smoothcolumns with slender and short cirri, relatively long intern ods, ramification patterns andpossession of both cryptosyzygial and synarthrial articulations. Difference in arm
ramification among Morozaki specimens may
well be attributed to the different growthstages they belong to. T. springeri was previously known only from the present Indian
Ocean. Although they are ca. 16 Ma apart,the Morozaki specimens show no essential
differences from the Recent specimens of T.
springeri, in morphology of column, columnal articulations, slender cirri, arm branchingpattern including the number of arms,
arrangement of ligamentary articulations, andmorphologies of brachials. Therefore, I amof the opinion that Morozaki specimens
should be assigned to T. springeri.
Genus Isocrinus von Meyer, 1836
Isocrinus sp.
Figures 6-4-8

Description: Columnals are slightly alter-~ Figure 6. 1-3: Teliocrinus springeri (A.H. Clark) from the Morozaki Group. 1,2: Scanningelectron micrographs of articular facet of a columnal, specimen 2 (UMUT CE18691) from Hajikami, Loc.
2. X 27 and X 91. 3: Specimen 8 (MFM 38054D) from Utsumi coast, Loc 5. X 3.4 4-8: Isocrinus sp.
from a road cut at Shinchiku (Loc. 6), the Bihoku Group. 4,5: Part of columns (UMUT CEI8692 andCEI8693). X 3.0. 6-8: Columnals (CE 18694-CEI8696). x3.0, x2.9 and x2.9. 9-14: lsselicrinus sp.
9,10: A part of column and articular facet (MFM 38055) from Yakuoji (Loc. 8), Ichishi Group. x3.3 11,
12: A part of column and articular facet (CE 18701) from Ohkatabira (Loc. 9), Awa Group. X 5.0. 13,14:
A part of column with nodal, and articular facet of the distal facet of nodal (CE 18702) from Ohkatabira(Loc. 9), Awa Group. x4.7.

426

Tatsuo Oji

nating in height and degree of inflation inmost columns, and eminently alternating inproximal columns. Internodals are stellate
and nodals pentalobate in section. Lateralsurface of internodals is almost flat or a little
inflating, and large columnals show lateralhorizontal crests. Cirrus socket is always
five in number, large in small specimens,
occupying almost entire height of the nodal,
and it is also large, but proportionally slightly smaller in large specimens. Distal articulation of nodals is synostosial, and it is concave, surrounded by raised edge. Articular
facet of internodals have nine to ten crenulae,
and there is gradual transition in size from
adradial to marginal crenulae, attaining theirgreatest length in the middle. Petal is lanceolate.
Remarks: The generic assignment of thisspecies to Isocrinus is tentative, because thediagnostic features of Isocrinus, i.e. combination of the arm articulation types (synarthrial
articulation between primibrachials and
IIBrl-2, and cryptosyzygial or symmorphialarticulation in IIBr3-4) are not observed in
the present collection. This species is presumably closely related to Isocrinus oregonensis and Isocrinus nehalemensis from the
Oligocene or Eocene of Oregon (Moore andVokes, 1953), because (1) external morphology of columnals are quite similar, i.e. general size of columns, tumidity of a columnal,
not so rounded pentagonal transverse sectionof column, and height of a columnal, (2)number of internodals is similar (dominantly
7, sometimes 8, rarely 6 or 9 in the present
species). Most specimens were subjected todeformation because of post-burial compaction. This is probably related to the argillaceous and soft lithology of the bed. Of thespecimens with at least one complete noditaxis, the number of internodals is five to nine:
5 (one case), 6 (two cases), 7 (58), 8 (14), 9 (5).
Of the 318 columns and columnals, five specimens show tetragonal outline. Klikushin(1977b) reported similar abnormality for a
Paleogene species Cainocrinus gorbachae.

This abnormality probably originated fromfour instead of five basal plates in the calyx.
The present specimens show higher frequencyof such an abnormality (5/318) than Cainocrinus gorbachae (2/1076).
Genus Isselicrinus Roverto 1914
emend. Rasmussen 1954
Remarks: Among isocrinid genera, Isselicrinus is defined by the following characteristics: less than five, usually two to three cirral
bases on the lower edge of the nodal, longinternode, and conspicuous and uniform
peripheral crenulae and adradial ridges on
the articular facet of columnals (Rasmussen,
1978, Klikushin, 1977a). Many species from
the Maastrichtian, Danian to Eocene, andrarely from Oligocene and Miocene are included in this genus (Klikushin, 1977a).
Maastrichtian to Paleogene species show relatively wide distribution, especially wellknown in Europe, whereas Isselicrinus has
declined and presumably extinct in the
Neogene (probably Miocene). Miocene
species have hitherto been described from
Italy (Noelli, 1900), Haiti (Springer, 1925),
Madura Island, north of Java (Wanner, 1938)
and Borneo (Sieverts, 1932). Morphology ofcolumnals of the Japanese species is mostsimilar to Isselicrinus sundaicus (Wanner)from Madura Island, although reliable
identification of the Japanese species isdifficult because of its fragmentary state ofpreservation. Isocrinids generally show considerable variation in stalk morphology, andthe species of Isselicrinus must be reviewed
from the viewpoint of intraspecific variation.
Klikushin (1977a) proposed a subdivision ofthis genus into three subgenera, Praeisselicrinus, Buchicrinus and Isselicrinus, mainlyon the basis of the degree of crenulation or its
absence on articular facet below nodal plate.
Most of the Recent species of Isocrinidae like
Metacrinus rotundus show relatively welldefined crenulation on a facet below nodal of
the proximal part of the column, whereas it
becomes flattened toward the distal part.

897.

Miocene Crinoids from Japan

Therefore, careful review of this character will
be needed.

Isselicrinus sp.
Figures 6-9-14

Descrintion: Specimens from Yakuoji,
Ichishi: Larger specimen (MFM 38055) has
six internodals, smaller specimen (MFM
38056) has three internodals. Outline ofcolumnals is elliptical, because of post-burial
compaction. Lateral surface of column issmooth and with no conspicuous inflation or
depression in larger specimen (MFM 38055),
whereas it is slightly depressed at suture
between columnals in smaller specimen(MFM 38056). Suture is almost straight onsurface. Articular facet of columnals shows
distinct marginal crenulae, 7-8 in number inlarger specimen and 8-9 in smaller specimen.
Crenulae becomes longer toward radial direction. Adradial ridges are conspicuous andthey are broadest in the middle.
Specimens from Ohkatabira, Awa: Outline of columnals is elliptical, also due topost-burial compaction. Most specimens
consist of two columnals, and lateral surfaceof columnals are smooth but depressed
toward suture between columnals. One
nodal plate (UMUT CE 18700) possesses two
cirral bases. They are directed obliquely
downward. Several internodal plates below
nodal possess longitudinal depressions onlateral surface of columnals, corresponding
presumably down-directed CIrrI. Facet
below nodal is concave, having conspicuous
marginal crenulae. Articulation between
internodals is similar to that of the specimensfrom Yakuoji.
Remarks: The present species shows
rather conspicuous crenulation on thearticular facet of the columnals, a nodal withtwo cirral bases, and thus classified under thesubgenus Isselicrinus, if we follow
Klikushin's classification. These wereobtained from two slightly different horizons427

of two areas, Yakuoji of the Ichishi Group
(N.7-8) and Ohkatabira of the Awa Group
(N. 9-10). All specimens show considerable
similarity of columnal morphologies, such assmooth lateral surface of columnals and distribution of crenulation on the columnal
articulation. Several specimens from Ohkatabira show weak but prominent periodic
constrictions at the surfure of two adjacentcolumnals.
Acknowledgments
I am grateful to Itaru Hayami, David Meyerand Arnold Miller for their suggestion to thisstudy and improvements of the English.
Haruyoshi Maeda also gave me several constructive comments. Kazuo Okamoto, Akira
Hayashida, Kiyotaka Chinzei and Y oshio
Watanabe gave important informations about
the stratigraphy and the crinoid localities.
The following persons gave me the opportunity to study the Miocene specimens; Fujio
Sakakura, Yoshiaki Mizuno, Masashi
Okuyama, Masatoshi Yamaoka, Kiichiro
Hachiya, Shigeto Hirose, Takanobu Yamaoka, Ryo Miura, Akihiro Murata, Takashi
Endo, and Yoshitsugu Okumura. Atsushi
Matsuoka and Terubumi Ohno kindly sentme some important references. Thanks arealso to David Pawson for the access to
NMNH specimens.
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Kyushu, Japan, Part I. Sci. Rept. Tohoku Imp.
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assemblages from the Miocene Bihoku Group at
Negita and "Kaseki-dani", Shobara City.
Abstr. papers. 94th Meet. Geol. Soc. Japan, p.
381.
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Oji, T., 1985: Early Cretaceous Isocrinus from Northeast Japan. Palaeontology, vol. 28, no. 4, p.
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Oyama, K., 1973: Revision of Matajiro Yokoyama's
type mollusca from the Tertiary and Quaternary

•

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Miocene Crinoids from Japanof the Kanto Area. Palaeont. Soc. Japan, Spec.
Pap., no. 17, p. 1-148, pis. I-57.
Rasmussen, H.W., 1978: Systematic description,
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Paleontology, Part T. Echinodermata 2,
Crinoidea (I). Geological Society of America
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--,1979: Crinoideos del Cretacico Superior y delInferior de la Isla Vicecomodieno (Seymour
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Roux, M., 1977. The stalk-joints of Recent Isocrinidae (Crinoidea). Bull. Brit. Mus. (Nat.
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p.613-618.
- - ', 1987: Evolutionary ecology and biogeographyof recent stalked crinoids as a model of the fossil
record. p. I-53. In, Jangoux, M. and Lawrence,
J.M. eds. "Echinoderm studies 2", Balkema,
Rotterdam.
Shibata, H., 1970: Molluscan faunas of the First
Setouchi Series, Southwest Japan, Part I.
Fauna of the Ichishi Group. Jour. Earth Sci.,
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Mizunami Fossil Mus., No.4, p. 45-53.
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Chubu province, Japan. Ibid., No.8, p.55-70,
pis. 12, 13.
Shikama, T. and Kase, T., 1976: Molluscan faunas of
the Miocene Morozaki Group in the southernpart of Chita Peninsula, Aichi Prefecture, Japan.
Sci. Rept. Yokohama Natn. Univ., Sec. 2, no. 23,
p. 1-25, pis. I, 2.
Sieverts, H., 1932: Jungtertiare Crinoiden von Seranund Borneo. Neues Jahrb. Min. Geol. PalCiont,
Abh., vol. 69, Abt. B, p. 145-168.
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Springer, F., 1925: A Tertiary crinoid from the West
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1-8, pI. I.
Utinomi, H. and Kogo, I, 1968: A revised catalogueof crinoids collected from Japanese waters.
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Wanner, J., 1938: Beitriige zur Paliiontologie desostindischen Archipels. XV. Balanocrinus sundaicus n. sp. und sein Epoke aus dem Altmiociin
der Insel Madura. Neues Jahrb. Min. Geol.
Paliiont. Beil. -Bd. 79, Abt. p. 385-402, 2 pis.
Watanabe, Y., 1988 (MS): Evolution of the forearc
basin of the Setogawa-Mineoka tectonic belt incentral Japan. Doctoral dissertation, Universityof Tokyo, 218 p.
Yajima, M., 1988: Preliminary notes on the Japanese
Miocene Ostracoda. p. 1073-1085. In, Hanai,T., Ikeya, N., and Ishizaki, K. eds., Evolutionary
Biology of Ostracoda. Kodansha Ltd., Tokyo.
Yokoyama, M., 1911 : Some Tertiary fossils from theMiike coalfield. Jour. Coli. Sci., Imp. Univ.,
Tokyo, vol. 27, Art. 20, p. 1-16, 3 pis.

Amatsu 3'(1$, Awa '1i:5f, Bihoku VIIl~t, Hajikami :f)Jf$, Hota i*Efl, Ichishi
Iwaya ;'fi~, Katada )tEfl, Morozaki Iiffi~, Ohkatabira :kiJ!IE.y, Shinchiku
Shobara J±JJil:, Togo-gawa p'mBJII, Utsumi i*Jrffj, Yakuoji ~:E~, Yamami

-;E;,
fi~,

illWo

B*~~m~~~~?~~v~C~~~~~~~~~;~~~?~~V~3~~B*~~~*1tJ: 'J ~~L, ~~~~:I:t!!~~~~~~~i'Go Iiffi~~~~ Teliocrinus fiftt*1 :/ t-l$~m~~~;:: J: "? -C ~ ~%I G:h -C ~ ,t.: 1QJ~~~G~~~fi~~;::YIJj G-Itko VIIl~t~~~ Iso-crinus sp. fU!HlB:t- 1/::{ :/1·1·1~~~~;::1i1bl.i' Go -;E;~~, '1i:5f~~~ Isselicrinus sp. fi,~~~~ • • ~~.~~10~~GoD.~~.d~A:h.'J~~fi~cm~~~K6*
3jZ1$~~~;::~~.lb G:hG o ~ ~~1r.vi Teliocrinus, Isocrinus, Isselicrinus ~~iJ~IQJ~~J: 'J ~~rnL, Metacrinus C SaracrinusiJ~IQJ~~~;::16t.:G~:ht,:~c"(·~Go ~~~lJJ3c L-C,::l:/ r-'7:t'~-$ (:t--A t- 7 V 7c=-"--¥=-7) c~-7o/7~1Jj~iJ~~;;tG:hGo~~1Jj~~;::J: 'J Metacrinus iJ~6*3jZ1$~~~;::16t.:G~:h, it.:1Jj~~;::J: "?-C~c.td:~;rffj~
iJ~ll!ii~c tJ: 'J, jiIff:kl$~ ~.~ ~ ? ~ ~ V~~5t~G ~;::~"?t.: cmtR~:hGo:k~,Mlf~Trans. Proc. Palaeont. Soc. Japan, N.S., No. 157, pp.430-434, 3 Figs., April 30, 1990

SHORT NOTES

23. A NEW METHOD TO EVALUATE DISSOLUTION OF CaC03
IN THE DEEP-SEA SEDIMENTS*
HIROMI MATSUOKA
Graduate School of Natural Science and Technology,
Kanazawa University, Kanazawa 920

aminifers or the initial composition of planktonic foraminiferal assemblage is not always
definite.
Oba (1969) divided a planktonic foraminifer, Globorotalia men a rdii , into three
types with respect to preservation of the tests(the perfect, damaged, and fragmented) andevaluated the degree of dissolution from theratio among the three types. This method
using only G. menardii is better than theother methods, because it is expected to beaffected by dissolution but not environmental
changes. In spite of that this method wasdeveloped to estimate the amount of CaCOa
dissolution (Oba and Ku, 1977; Ku and Oba,
1978), works employing the method were so
far only a few (Oba, 1983).
Several papers have reported on selective
dissolution of calcareous nannofossils(McIntyre and McIntyre 1971 ; Berger, 1973;
Roth and Coulbourn, 1982), but, unlike foraminifers, calcareous nannofossils are rarely
used to evaluate CaCOa dissolution in the
deep-sea sediments. It wa~ difficult to not
only observe them in detail under a lightmicroscope for their small size but also to
express their degree of dissolution objectively.
The purpose of this paper is to propose a
new method to evaluate the degree of CaCOa
dissolution in deep-sea sediments by calcareous nannofossils and then to substantiate its
usefulness by comparing with the othermethod by a planktonic foraminifer (G.
menardii).

Introduction

The most part of CaCOa stored in deep-sea
sediments is produced in the sea-surface byplanktonic foraminifers and calcareous nannoplanktons. The CaCOa sinks down to thesea floor through water column and is deposited there. Accumulation of CaCOa isaffected by its dissolution in the deep-sea aswell as production in the sea-surface. While
the CaCOa production reflects environment of
the sea-surface, its dissolution does that of the
deep-sea. Evaluation of the degree of dissolution is essentially important to analyze thechange in deep-sea paleoenvironment.
Three methods have been generally employed to evaluate degree of CaCOa dissolution: (l) Solution Index (Berger, 1968); (2)the ratio of planktonic to benthic foraminifers; and (3) the ratio of fragmented toperfect tests of planktonic foraminifers. The
Solution Index is based on the difference ofdissolution among species of planktonic foraminifers; ratio of species more resistant todissolution and those less resistant. However, fossil assemblage content of planktonic
foraminifers is effected by the initial assemblage as well as dissolution. It is impossible
to estimate accurately the degree of dissolution from the Solution Index. The other two
methods are also insufficient because the initial ratio of planktonic to benthic for'Received August 25, 1989; accepted December 20,
1989
430

Shorl Notes 23.

CaC03 dissolulion nannoplankton

Method and samples
A calcareous nannofossil , Calcidiscus leptoporus has two shields (distal and proximal) which are connected with a central
column. Schneidermann (1977) investigatedselective dissolution of nannoflora in core-top
sediments and showed a distinctive pattern ofdissolution In C.leploporus. The twoshields of well-preserved C. leptoporus areconnected each other. When dissolution
proceeds , however , either the proximal shieldtends to dissolve along the suture line or thecentral column is dissolved to separate twoshields. Only distal shields tend to occur inintensively dissolved samples.
In this work the manner of preservation in
C. leptoporus dissolution is adopted to ev a luate CaC0 3 dissolution. Fossil coccoliths ofC.leptoporus is divided into two types, theperfect one with two shields and the broken
one with only distal shield (Figure I) ; a431

coccolith with distal shield and a part of
pro ximal shield is included in perfect coccolith. The ratio of the two types is employed as a criterion to evaluate degree of
C aC0 3 dissolution.
The piston core " KH84- 1, St. 21 " wasrecovered from the deep-sea floor at westflank of the West Mariana Ridge (W55.8'N ,14r 22.3'E ; water depth of 3512 m) during
KH84- 1 cruise of R / V Hakuho-Maru of
Ocean Research Institute, University ofTokyo (Figure 2). The core is 916 cm long,essentially composed of olive calcareous ooze
and intercalates thin layers of tephra andsandy silt (Kobayashi , 1985). The base ofBrunhes Epoch is located at 498 cm (subbottom depth) and the top and base of the
Jaramillo event at 620 cm and 670 cm, respectively from paleomagnetic measurement(Kobayashi et al. , personal comm.) . The
sedimentation rate of the core is to be about
0.7 cm / Ky. Two major biostratigraphic

Figure 1. Photographs 1,2 and 3 a re electron micrographs and the scale Dal 1,1 photograph 1 represents
5,um. Photographs 4, 5 and 6 a re optica l micrographs and the scale bar in photograph 4 represents 500,um.
1- 3, Calcidiscus leptoporus (Murray and Blackman) , Sa mple at 90 cm (subbottom depth): 1, proximal viewof perfect coccolith (distal and proximal shield); 2, proximal view of perfect coccolith (distal shield and apart of proximal shield); 3, proxima l view of broken coccolith (distal shield). 4- 6, Globorotalia menardii(Parker, Jones and Brady), Sample at I cm (subbottom depth) : 4, perfect test; 5, damaged test; 6, fragmented test.

Hiromi Matsuoka

432

r--r-----,-----,,,,---,-----.--,50'N

40'N

30'N

KH 84-1 st.21

•

20'N

GUAM

10'N

0'

120'E

Figure 2.

Locality of Core KH84-l St. 21.

events of nannofossils are founded: the firstoccurrence of Emiliania huxleyi at 180 cm :and the last occurrence of Pseudoemiliania
lacunosa at 310 cm in sub bottom depth(Matsuoka and Okada, 1989). The proposed
age of these events is 0.27 Ma and 0.46 Ma
respectively (Thierstein et al., 1977) and is ingood agreement with that determinedmagnetostratigraphically. Only the upper
600 cm of the core was studied in this work.
Small pieces of core samples were. takenwith 10 cm-interval for the C. leptoporus
analysis. These samples were prepared tomake carbon replicas to observe under atransmission electron microscope. C. leptoporus more than 5 Jim in diameter wascounted to 50 specimens to determine theratio of the perfect to the broken coccoliths.
Between 210 cm and 320 cm in the sub bottom
depth, however, the samples of C. leptoporus
were counted to 100 specimens with smear
slide under a light microscope because of its
scarcity.
About 3 g core samples were taken with 5

cm-interval for G. menardii analysis. The
samples were disaggregated in water andwet-sieved at 63 Jim in diameter. Tests of G.
menardii larger than 250 Jim in diameter werecollected to determine the ratio of perfect
tests. They are divided into three groups(Figure 1) based on the criteria ofOba (1969).
While 50 to 100 tests of G. menardii weresecured from most of the examined intervals,
certain intervals yielded less than 30 tests, sothat the latter was excluded from the following discussion.

Result and discussion
Figure 3 shows that the curve of change in
CaC03 dissolution as determined by themethod with C. leptoporus well correlateswith that by G. menardii. It might be doubted that destruction of coccoliths and foraminiferal tests is caused from mechanicaldisintegration during separation procedure
but not from chemical dissolution. The
specimens of C. leptoporus and G. menardii
treated here are little affected by artificial
destruction because experimental results with
C. leptoporus conform to those with G.
menardii in spite of the completely different
treatments. Mechanical destruction in sedimentation process is another matter of concern. Effects of this destruction seem to bedifferent between G. menardii and C. leptoporus, because the size of G. menardii test
is about 100 times larger than that of C.
leptoporus coccolith. The shape of coccoliths of C. leptoporus observed here is similar to the dissolution pattern described by
Schneidermann (1977). The shapes of thetests of G. menardii treated here resemble thethose artificially dissolved by Oba and Ku(1977). These findings imply that the observed destruction of coccoliths and foraminiferal
tests is essentially attributable to CaC03
dissol ution.
The dissolution curve of C. leptoporus in
Figure 3 indicates that the dissolution tends
to advance with increase of the subbottom

Short Notes 23.

ooCaC03 dissolution nannoplankton

G. menardii

C. /eptoporus% of perfect50% of perfect
50

100 0

100

E

~2

I
I-

433

method with C. leptoporus, because it has
intensive resistance to dissolution. C. leptoporus is widely and abundantly distributed and the perfect coccoliths are easily distinguished from the broken ones under a lightmicroscope. This method with C. leptoporus should be convenient and time-saving tool
for paleo-oceanographic studies to evaluate
the degree of CaC03 dissolution.

a.

~ 3
W

II:

o 4
o
5

6 -'------'---~=-----' .1.--=::=.._ _ _---'

Figure 3. Correlation of percentage of the perfect test of G. menardii (left column) with that of C.
leptoporus (right column).

Conclusions
Conclusions are as follow: (I) it is a useful
method to measure the ratio of the perfect tothe broken coccoliths of C. leptoporus inorder to evaluate degree of CaC03 dissolution in deep-sea sediments and (2) the method
based on the percentage of perfect tests of G.
menardii (Oba, 1969) appears to be verified asa valid and reliable tool for evaluating
CaC03 dissolution.
Acknowledgments

depth, whereas that of G. menardii dose notindicate the same trend. Two causes may be
attributed to this tendency: (I) C. leptoporus continues to dissolve after deposition;and (2) C. leptoporus tends to be damaged
with compaction of sediment. Although it
can not be determined which cause is responsible to the tendency, at present, it appears to
be interesting with respect to diagenesis of
calcareous nannofossils.
The 8 cycles are recognized in the CaC03
dissolution curve between the core top andthe Brunhes-Matuyama boundary and they
appear to agree chronologically with thecycles of glacial-interglacial stages. Thisfind supports the opinion that dissolutions
increased during interglacials but decreased
during glacials in the Pacific Ocean. The
oxygen isotope ratio of planktonic foraminifers from this core is being determined
to discuss the CaC03 dissolution in moredetail.
Even if the dissolution is intense, it ispossible to evaluate CaC03 dissolution by theI am grateful to Profs. K. Konishi and T.
Oba (Kanazawa University) and H. Okada(Yamagata University) for their helpfuladvice and discussion. My thanks are also
due to Prof. K. Kobayashi and Mr. T. Furuta(Ocean Research Institute, University ofTokyo) for the access of the core samples andunpublished information on magnetostratigraphy.
References
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Deep-Sea Res., vol. IS, p. 31-43.
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112-129.

Hiromi Matsuoka

434

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analysis of Quaternary nannoplankton in subtropical northwestern Pacific Ocean. Mar.
Micropaleontol., vol. 14, p. 97-118.
Mcintyre, A. and Mcintyre, R., 1971 : Coccolith concentrations and differential solution in oceanic
sediments. In, Funnel, B. and Riedel, W.R.
eds., The Micropaleontology of Oceans. Cambridge University Press, Cambridge, p.253-261,
pis. 16.1-16.2:
Oba, T., 1969: Biostratigraphy and isotopic
paleotemperatures of some deep-sea cores fromthe Indian Ocean. Tohoku Univ., Sci. Rep.,
2nd Ser. (Geol.), vol. 41, no.2, p.129-195, pis.
20-23.
- - , 1983: Importance of constant volume sampling
for sediment core study. Fossils, no. 34, p.33-

40. (in Japanese with English abstract)- - and Ku, T.L., 1977: Measurement of CaC03
dissolution in deep-sea sediments. Ibid., no. 27,
p. 1-14, pI. I. (in Japanese with English abstract)Roth, P.H. and Coulbourn, W.T., 1982: Floral andsolution patterns of coccoliths in surface sediments of the North' Pacific. Mar. Micropaleontol., vol. 7, p. I-52.
Schneidermann, N., 1977: Selective dissolution of
Recent coccoliths in the Atlantic Ocean. In,
Ramsay, A.T.S. ed., Oceanic Micropaleontology,
Academic Press, New York, N.Y., p. 1009-1053,
pis. 1-6.
Thierstein, H.R., Geitzenauer, K.R., Molfino, B. andShackleton, N.J., 1977: Global synchroneity oflate Quaternary coccolith datum levels: Validation by oxygen isotopes. Geology, vol. 5, p.
400-404.

435

PROCEEDINGS OF THE PALAEONTOLOGICALSOCIETY OF JAPAN

B*o~~~~

1990~~~. ~~B *51:¥!.J"M~~:ft· ~:ftn~ 1990 ~ 2 Yl 2 B -4 B tc:.!f.

(2)
(3)

nffi*~*~~~·.!f.nffi*~ • • ~$~~.~hk(~:lJQ~ 265).

Causal factors of global mass-extinctions:
Biotic and abiotic ......... 3jZ!f5!.-;@:. 1iiif*'fIlx
Sea-level changes through geological times................................ ·,J,~fm::. • :!tlffi&,±tifE

1; A

~

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Glanta -1fID/:0) ceratoikiscids (1VtIi:t~M)
Third International Conference on Paleo-oceanography(Cambridge; 1989~9YlIO B-16 B) t±lffl!;'*15'...................................................... ······J1lf~1jnE
~

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*'fIl~~'E*Jl.M1r.E~0)1:¥!.J:it!HJIl.!:.:t0)Jjj(;.lz:~~...................................................... ,J,~JJii:!iggft~~ 29 @] IGC (Kyoto, 1992) ~.tc:rPJH"-C~~A:J1lf~~~·~~~~·~$-Jjj(;~ 28 @] IGC (Washington, D.C., 1989)0)*15'............................................. 1J!Il$-Jjj(;. iltrffi~~~ 29 @] IGC (Kyoto, 1992) O)*{iIlI:/XrJi'. ......... J1lf~~~
51:¥!.J~:i!!0) -y /,;f-:; 1/ A ~tc: -:>1. '-CA.

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andtheoretical

approaches in 'evolutionary biology.................................... ~~~ii1Ij • liI5PJ~x

Structure, formation and evolution of fossil
hard tissues .................. 'N'*~tifE· ~~tli\((3) Tempo and modes of morphologic evolution infossil lineages .............. +~~1:. iI.ll.:fr1illZ(4)Evolution and migration of marine vertebrates
In the Pacific realm ...... ft:frJlI~!MIl • 1lUJ~~~(5)

Taphonomy with special reference tosedimentological and geochemical approaches.................................... Jli~ijt4=. • rW~B.

Interdisciplinary Symposia(1)

Paleobiogeography of Phanerozoic biota inview of plate tectonics.............. ·it7.K~.

~

Jjj(;[.:t0)3] .......................................... j\~ flll
"Lacazopsis" tc:-:>I.'-C ...... ~1LffiI~
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ifjpJIIJl~n'QO)

An interesting pachydiscid ammonite from Hokkaido,
with remarks on relevant taxa ............ Matsumoto, T.

y;.-;f-y,/.l.

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constraints: Constructional.............................. ~W~5!.- • 06'~~.llIJ • 5:fr m
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Notes on a Cretaceous bivalve Inoceramus (Platycer-amus) mantelli Mercey (Barrois) from Japan.............................. Noda, M. and Toshimitsu, S.
Wp~~$~~0)~~*l9W~-C~~~hk7/''E":r-1 ~ 3 f! .. ·Em~.

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mopolitan elements ................................. ]3;;* '1i.
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..........................................·.. liit!!i '/1r. iIl1.:fr1iliZ
The most primitive living balanomorphan from theNorth Fiji Basin Abyssal Hydrothermal Field

437······ .. ················yamaguchi, T. and Newman, W.A.
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Mollusca). from the Bear River. southwest Washington. U.S.A. ···············Kanno. S. and Danner. W.R.
Dinosaur tracks and radial cracks: unusual footprintfeatures·········Matsukawa. M.• Obata. I.. and Lockley. M.G.
JIJi:.!lt~BJIIWFJ&JiI~ii' G9§Ji!. ~ nt.:~'I@;O)~Ji'tffi{tE············OOJ't.iE* • I1E!l!f1!!J?X • ~illij(J.t • *ttJII~5f'IJ
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Miocene Mizunami Group of central Japan and its
implications on paleogeography ············Tomida, Y.
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Molluscan fossils from the Ryukyu islands. Southwest
Japan; Part 3. Gastropoda and Pelecypod a from the
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Okinawa-jima ....... ································Noda. H.

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New members approved at the Council Meeting on February 1, 1990
Iwane Mizuno
Manabu Kano
Chiyomi Yamakawa
Hideki Okuyama
Toshio Tanaka
Y oshihiro Mizuno
Miki Miyagi
Jean Vannier
Yukihiro Takaizumi
Mamoru Yasuda
Kazuhiro Sugiyama
Norikazu Kurosawa
Eiichi Uchida
Takami Nobuhara
Masahiro Kunimitsu
Hiroaki Karasawa
Masahiro Sugiyama
Kanji Shikano
JunichiMizunoShin-ichi
Sano
Yoshio Yuki
Ryousuke Motani
Takao Ubukata
Tomoaki Naruse
Tadahiro Kajiwara
Kokichi Inoue
Takaya Takeuchi
Atsushi Ujihara
Kazuo Kurosawa
Mitsuharu Oshima
Osamu
Takahashi
Hiroyuki Maeda
Mika Sato
Takashi Toyoda
Masayuki Shimizu
Takayuki Yoshiike
Takeshi Ohsawa
Akihiko Murakami
Mitsuo Kamei
Yuji Yamaoka
Masaru Sugawara
New ferrows approved:
Hisao Ando
Mitsunobu Furuichi
Keiichi Hayashi
Yukio Isozaki
Junji Horiuchi
Koutarou Kamata
Hitoshi Koizumi
Takeshi Kozai
Naoyuki Kuga
Tomio Kuroda
Haruyoshi Maeda
Shinya Matsuda
Kazuyuki Matsusue
Nobuomi Matsuura
Rihito Morita
Toru Nakamori
Harumi Nishimura
Tatsuo Oji
Takashi Okamoto
Asahiko TairaSeiichi Toshimitsu
New Honarary members approved by the 1990th Annual Meeting of the Society held
on February, 1990.
Kazuo Asama
Tetsuro Hanai
Kametoshi Kanmera
Tsugio Shuto
Toshimasa Tanai
Seceding members:
Junichi Kamishima
Hiromi Kanasugi
Kazuhiro Takabatake
Bunji Mizunuma
Osamu Miyashita
Yutaka Saito
Tadashige Habe
Huang Muk Kim(Foreign members)
H.M. Kapoor
Patehara Pariwatvorn
Changwu Pan
T. Suntharalingam
Susumu Honjo
Godfrey F. Kaufmann
Rucha Ingavat
Lowther J. Stewart
James Xavier Corgan
Lioyd H. Burckle
Deceased members:
Sumio Yamazaki
Kimihiko Ozaki
Shigeru Imanishi
Yukio Kuwano

ti;~~~~(1989-1990)

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Transactions and Proceedings of the PalaeontologicalSociety of Japan

New Series No. 157

April 30, 1990

CONTENTS
TRANSACTIONS
893.

Itaru Koizumi and Yukio Yanagisawa: Evolutionary change in diatom
morphology - An example from Nitzschia fossilis to Pseudoeunotia dolio/us ................................................ 347

894.

Atsushi Kaneko: A new trilobite genus Rhinophacops .................. 360

895.

Tatsuro Matsumoto, Mamoru Nemoto and Chisato Suzuki: Gigantic ammonites from the Cretaceous Futaba Group of Fukushima Prefecture ........ 366
Hiromichi Hirano, Takashi Okamoto and Khoji Hattori: Evolution of some
Late Cretaceous desmoceratine ammonoids .............................. 382

896.
897.

Tatsuo Oji: Miocene Isocrinidae (stalked crinoids) from Japan and their,',biogeographic implication ........................................... .412

SHORT NOTES
Hiromi Matsuoka: New method to evaluate dissolution of CaC0 3 in the'deep-sea sediments .................................................... 430
PROCEEDINGS .......................................................... 435

23.