ISSN 0031-0204

Transactions and Proceedingsof thePalaeontological Society of Japan
New SeriesNo. 1;32

Palaeontological Society of Japan
December 30, 1983

Itaru HAYAMI and Ikuwo OBATA

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The ostracod carapace on the cover is an adult specimen of Manawa konishii
NOHARA (Suborder Palaeocopina, Family Punciidae) from the East China
Sea. (photo by K. ABE, x190)

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Trans. Proc. Palaeont~ Soc. Japan, N.S., No. 132, pp. 191-219, pIs. 41-46, December 30,1983

769. NOTES ON THE SO-CALLED INOCERAMUS JAPONICUS(BIV AL VIA) FROM THE UPPER CRETACEOUS OF JAP AN*
MASA YUKI NODA
Minamioita Junior High School, Oita 870

Abstract.
In this paper, Inoceramus japonicus Nagao et Matsumoto, 1940
is discriminated into 1. (Platyceramus) higoensis sp. nov., 1. (Pl.) japonicus hokkaidoensis subsp. nov., and I. (Pl.) japonicus japonicus, which approximately
correspond to forma a, ~ and 'Y of the original description, respectively. And I. (Pl.)
higoensis is subdivided into 1. (Pl.) higoensis higoensis and 1. (Pl.) higoensis subsp.
At first I mention the procedures of the specific and the subspecific discrimination at population level. Some selected characters are biometric ally and statistically examined by means of the Student's t-test, the rejection ellipse, 75 percent
rule and analysis of the relative growth. Then I give the specific and subspecificdefinition of the above taxa, comparing them with already known species. FinallyI discuss the phylogenetic relationships of the concerned species and subspecies.

Introduction

On the other hand, the present species resembles closely the widespread species 1. unduiatoplicatus Romer, as has been alreadypointed out by Nagao and Matsumoto (1940),
who suggested the possibility of the specificidentity. Matsumoto and Ueda in Ueda (1962,
p. 166) mentioned the reason of holding thespecific name I. japonicus and furthermore
proposed a problem as fOllOWS, "We expect thatthe statistic studies of the numerous specimensfrom selected provinces in the future mightreveal that the variations overlap between theJapanese and Texas or European provinces
and that the distinction on the average be rather
subspecific. Until that the specific name 1.
japonicus is to be kept. The difference in thegeological age between I. japonicus and I. undulatoplicatus can not also be overlooked. Whether
the immediate ancestor is common or not is,therefore, another question to be settled."
The purpose of the present investigation is
to work out the above mentioned problem by

Inoceramus japonicus Nagao et Matsumoto,
1940, is a good index of the Upper Santonianof Japan. Before that date the specific name,without defintion, was used tentatively by Sasa
(1932), for the specimens from the Kunitan
Formation of the Kuji Group, Northeast Japan.
Nagao and Matsumoto (1940) examined many
specimens from various localities of Japan andSouth Saghalien and recognized three forms inthe species, denominating them as forma a, ~and 'Y. Subsequently the succession of the species
and its relationship with I. ezoensis Yokoyama
from the Santonian of Japan were discussed by
Matsumoto (1959). Matsumoto and Ueda in
Ueda (1962) designated Sasa's specimen (Nagao
and Matsumoto, 1940, pI. 9, fig. 1; Matsumotoand Ueda, 1962, pI. 24, fig. la, b; present paper,
PI. 41, Fig. 1) as the lectotype. This was forma'Y of Nagao and Matsumoto.

* Received September 29,1982.
191

Masayuki NODA

192

means of statistical methods of suitable samples
collected by myself and others.
Although I have not yet dealt with enoughsamples of "I. undulatoplicatus" from the
Texas and the European provinces, I reporta result of my study on the samples of "I.
japonicus" from selected areas of the Japaneseprovince.

of them is available for measurements. Others
are unsuitable for measurements due to moreor less insufficient preservation or too small
size for the standard dimension. The sample
sizes for the selected characters are shown
respectively in Table 1.
In addition to the above, as subsidiarymaterial, samples from Uto Peninsula, Kunitan,

Material
Hitherto known localities of I. japonicus(s. 1.) are numerous, as shown in Text-fig. 1. It
occurs also in South Saghalien (see Matsumoto,1942). It would be desirable to examine a
population sample for every locality, but I
selected some representative good localities
from my experience in the field work. The
samples examined in the present study are
primarily taken from the Lower Subgroup of
the Himenoura Group in the Amakusa Islandsof western central Kyushu and the lower partof Unit C (of Inoma in Matsumoto et al., 1972,
text-fig. 8) of the Upper Yezo Group in the
Haboro area of Hokkaido. Despite of a great
number of specimens from each locality, a part

.,
.2

40·

1-----+- 3 B •\----1-36·

100

200

300km

Text-fig. 1. Map showing the locations of Inoceramus (Platyceramus) japonicus and 1.
(Pl.) higoensis.
1: Abeshinai, 2: Haboro, 3: Obira, 4: Mikasa, 5: Yubari, Oyubari, 6: Hobetsu, 7: Tomiuchi, 8:
Furenai, 9: Urakawa, 10: Kuji, 11: Aridagawa, 12: Kajisako, 13: Uwajirna, 14: Uto, '15:
Amakusa, 16: Shishijima.

769. Inoceramus japonicus

193

Table 1. Sample size for selected characters.
characterah/I H =9Omm

HL/h H ' 9Omm

R.DoH"90mm

tanO H =90mm

rejection ellipse

relative growth

1Kugushima
I Kojima

11

8

8

7

7

7

12

B

7

6

5

5

5

9

A

5

total number

HH
12

28

9

Tomiuchi, Kikume·zawa, Chikubetsu (Pankezawa), Sankei (SK62), Nakahobetsu (lnasato 1),
Kajisako and Kawakami (South Saghalien) arealso examined. They consist of only a few
specimens for each locality and insufficientfor statistics, but used for some observationand measurements.
The examined specimens are probably allochthonous, but the distance between theirhabitat and place of burial is presumed to havebeen short, because they are often preserved
as closed, articulated valves or little damaged
and because it is hardly considered that large
individuals more than 150 mm in shell height
were transported for a long distance from thehabitat to the embedded place where clay andsilt deposited under a quiet condition.
The field work in Hokkaido was made together with Prof. Matsumoto, and the specimens
of Inoceramus were all provided through thekindness of him.
Sample guide
Sample A-I (see Text-fig. 2) Locality: HI
1023, on the western beach about SO m southwestward from the mole, Kugushima, an isletof Amakusa Islands, administratively Ryugatake·machi, Amakusa-gun, Kumamoto Prefecture.
Long. 130 0 24'OS"E , Lat. 32°23'23"N (seetopographic map, Takado Quad., 1 :25000). Str.
position: Upper part of the Middle Member,
Lower Formation, Lower Subgroup, Himenoura
Group (L-l·3 of Tashiro, 1976; K549, Lowerpart of I-d of Ueda, 1962). Mode of occurrence: Common in black shale about 40 cm inthickness, often with inarticulated valves disposed parallel to startification and somewhat
crushed; together with Eupachydiscus haradai(Jimbo), Protexanites (Anatexanites) cf. fuka·
zawai (Yabe et Shimizu), Gaudryceras denseplicatum (Jimbo), Polyptychoceras obstrictum

Text-fig. 2.
ura area.

Locality map of the Himeno-(Jimbo), P. haradanum (Yokoyama). In addition,
Nucula (s. s.) amanoi Tashiro, N. (Leionucula)formosa (Nagao), N. (L.) nagaoi Tashiro, Acila(Trancacila) hokkaidoensis (Nagao), Glycymeris
amakusensis Nagao, Naonavis sachalinensis(Schmidt), Apiotrigonia minor (Yabe et Nagao),
Solemya augusticaudata Nagao and Sphenoceramus naumanni (Yokoyama) are commonly
associated.
Sample A-2 (see Text-fig. 2) Locality: HI
1009, on the northern shore of Kojima, near
Himenoura, Himedo~achi, Amakusa-gun. Long.
130 0 26'12"E, Lat. 32°26'12"N (see topographic
map, Himenoura Quad., 1:25000). Str. position:
Lower part of the Middle Formation, Lower
Subgroup, Himenoura Group (K26, 27, Lowerpart of II Formation of Ueda, 1962). Mode

Masayuki NODA

194

of occurrence : Abundant in a black shale layerof about 100 ern in thickness; commonly inarticulated valves of large individuals more than
150 mm in shell height, buried parallel to stratification and secondarily crushed; together with
Neophylloceras cf. rcimosum (Meek), Hauericeras(Gardeniceras) angustum , Eupachydiscus haradai,
Gaudryceras denseplicatum, Polyptychoceras obstrictum, P. haradanum, Nucula (s. s.) amanoi,
N (Leionucula) formosa , Ez onuculana mactraeformis (Nagao), Nanonavis sachalinenesis, Elec troma shiranuiensis Tashiro, Parvamussium cowperi yubarense (Yabe et Nagao), Miltha (s.1.)
amakusensis Tashiro, Inoceram us (Endocostea)
cf. ba ltic us toy ajoanus Nagao et Matsumoto
and Sphenoceramus cf. nagaoi (Matsumotoet Ueda).
Sample B (see Text-fig . 3) Localities: Hb19972001, Migi-no-sawa, a tributary of the River
Haboro at about 100 m-400 m downstream
from the crossing of road and stream , Haboromachi, Tomamae-gun, Hokkaido; Long. 141°
53'48"E ~ 141°53'55"E, Lat . 44°16'40"N ~44°16'40"N (see topographic map, Horobetsuyama Quad., 1 :25000). Str. position: Unit C
Upper Yezo Group of the Haboro Area, San:
tonian (see Matsumoto and lnoma, 1972, p . 189;
text-fig . 8). Mode of occurrence : Common in'--_ _"'soom

calcareous nodules, generally well preserved;
closed valves with well preserved test including
a pearly layer; associated with Gaudryceras
tenuiliratum Yabe, Hauericeras (Gardeniceras)
angustum, Menuites pusillus Matsumoto, Kitchnites (Neopuzosia) haboroensis Matsumoto etlnoma, K. (N) ishikawai (Jirnbo), Polyptychoceras (Subptychoceras) yubarense (Yabe), Damesites sugata (Forbes) and Sphenoceramus naumanni (Yokohama).
Sample. C (see Sasa, 1932 and Matsumotoand Ueda, 1962).
For the localities record of subsidiary specimens see the item of description and Text-fig. 1.

Method of analysis
Each of the samples examined in this study
does not always represent one fossil population
in a strict sense, but it has been obtained fromone and the same stratigraphic unit within alimited area.
The following characters are statisticallyh

14I· !iS ·Text-fig. 3.
area.

Locality map of the Haboro

Text-fig. 4.
ments.

Basic morphology for measure-769. Inoceramus japonicus
examined. The allometric characters are compared at a certain growth stage.
1. Anterior-hinge angle (a): angle between
anterodorsal margin and hinge-line.
2. Obliquity of shell (8): angle between hingeline and line of H (H: maximum dimension fromumbo to ventral extremity).
3. Number of divergent ribs. The anterior (Ra)195

and the posterior (Rp) ones respectively.
4. Simple ratio of shell height (h) to shell length(I) [h/l].
5. Simple ratio of shell height to shell length at
the growth stage of 90 mm in H [h/IH =90mm]'
6. Simple ratio of length of hinge-line (HL) to
shell height [HL/h].
7. Simple ratio of length of hinge-line to shell

Table 2. Measurements of sample A (Himenoura). linear dimension in mm.
specimen

valve

h

I

H

HL

a

B

Ra , Rb

JG.H2701

R

36.3

32.0

39.0

16.9

120°

51 °

-

JG.H2702

R

28.1

29.3

31.9

14.6

123°

44°

,
4 ,

JG.H2708

R

49.9

47.0

52.6

21.8

111 °

50°

5 ,

2

JG.H2709

L

84.6

72.3

90.1

35.5

110°

53°

7 ,

5

-

2

JG.H2712

R

94.3

67.3

100.0

26.3

110°

70°

13 , 12JG.H2713

R

115.4

79.4

119.3

33.1

107°

73°

14 , 13JG.H2719

L

184.3

145.1

195.3

45.1

117°

75°

13 , 10

JG.H2720

R

195.9

156.0

215.0

49.3

115°

70°

11 , 10

JG.H2727

L

139.4

112.0

144.0

30.5

122°

69°

13 ,

9

JG.H2736

R

177.3

141.2

188.0

47.0

110°

70°

11 ,

9

JG.H2737

L

205.2

167.2

216.5

47.0

116°

73°

14 , 14

specimen

valve

h/l

h/1H=9Omm

HL/h

HL/hH=90mm

R.D·H=90mm

JG.H2701

R

1.13

-

0.47

-

-

-

JG.H2702

R

0.96

-

0.52

-

-

-

tan<'ip.=9Omm

JG.H2708

R

1.06

-

0.44

-

JG.H2709

L

1.17

1.17

0.42

-

-

-

JG.H2712

R

1.40

1.20

0.28

0.30

0.28

2.1445

JG.H2713

R

1.45

1.18

0.29

0.38

0.29

3.4874

JG.H2719

L

1.27

1.28

0.24

0.30

0.18

2.7475

JG.H2720

R

1.26

1.30

0.25

0.36

0.14

3.0777

JG.H2727

L

1.24

1.16

0.22

0.31

0.18

3.0777

JG.H2736

R

1.26

1.27

0.27

0.40

0.14

2.6051.JG.H2737

L

1.23

1.23

0.23

0.29

0.22

2.7475reference:hshell heightI
shell length
dimension from umbo to ventral extremity
H
HL
hinge·lineaangle between hinge-line and anterior marginB
angle between hinge-line and H
Ra
number of anterior rib
Rbnumber of posterior rib
Lleft valveRright valve

h/l :h/1H=9Omm

HL/h
HL/hH=90mm
R.D·H=90mm
tanB H=90mm

simple ratio of h to I
simple ratio of h to I at the growthstage of 90mm in H
simple ratio of HL to hsimple ratio of HL to I at the growthstage of 90mm in H
rib density at the growth stage of
90mm in H
tangent of angle B at the growthstage of 90mm in H

Masayuki NODA

196

for measurements of length and angle respectively. Measurements were made three times forthe same part, and the mean values are shown.
From the above numerical characters, the standard deviation and Pearson's coefficient of variation were calculated. The results of statistics
were analysed by the following procedures.
1. Evaluation of the difference between themeans of a pair of samples by the method of
the Student's t-test.
2. Examination by the method of the rejection
ellipse.

height at the growth stage of 90 mm in H [HL/
hH=90mm] .
8. Divergent rib density (R.D.) at the growthstage of 90 mm in H [R.D. H=90mm]'
9. Tangent of obliquity at the growth stage of
90 mm in H [tanOH=90mm]'
10. Relative growth of shell height and shelllength [l=~hex].
The basic morphology for measurements
is shown in Text-fig. 4. Calipars of JIS standard,
200 mm in measurable extent and 1/20 mm inaccuracy, and contact goniometer were used

Table 3. Numerical characters of Sample A (Himenoura).
ex

h/IH=90mm

HL/h H=90mm

R.D· H=9Omm

tano H=90mm

N

11

8

8

7

7

m

114.6

1.224

0.345

0.204

2.84106s

5.44

0.05420.04800.06080.425860

v

4.75

4.43

13.91

29.80

14.99

N : sample size, m : mean value, s : standard deviation, v : Pearson's coefficient of variation

Table 4. Measurements of sample B (Haboro). linear dimension in mm.
specimen

valve

h

I

H

HL

ex

6

Ra , Rb

JG.H0115

L

100.0

98.6

119.3

44.8

116°

50°

8 ,

8

JG.H0179

L

145.0

160.0

172.3

74.1

101°

54°

6 ,

5

JG.H2738

R

85.6

77.7

90.5

31.4

110°

52°

7 ,

3

JG.H2739

R

108.3

91.8

110.4

46.8

110°

65°

10 ,

4

JG.H2740

R

121.3

106.8

131.4

-

105°

60°

9 ,

-

JG.H2741

L

46.8

44.9

49.0

22.1

106°

47°

6 ,

-

JG.H2742

R

102.1

103.7

121.5

52.6

111 °

52°

10 ,

7

specimen

valve

H/I

h/lH=90mm

HL/h

HL/hH=90mm

R.D.H=9Omm

tan6 H=90mm

JG.H0115

L

1.01

1.05

0.45

0.51

0.15

1.4281

JG.H0179

L

0.91

0.95

0.51

0.56

0.09

1.1504

JG.H2738

R

1.10

1.02

0.37

0.48

0.14

1.1504

JG.H2739

R

1.18

1.13

R

1.14

1.5399-JG.H2741

L

1.04

1.11
-

0.49
-

0.12

JG.H2740

0.43
0.47

-

-

-

0.98

1.13

0.18

1.4281

JG.H2742

R

0.52

0.55

-

769. Inoceramus japonicus
3. Examination of the average relative growth.
(1) Analysis of slope of a pair of reduced
major axes.
(2) Evaluation of intercept of a pair of
reduced major axes.
4. For other characters inadequate for measure.
ments and numerical analysis, for instance,
the marginal outline of shell, the curvature ofdivergent ribs and other feature of surface
ornamentations, I examined by the traditional
method of observation for a number of speci.
mens.
5. Examination in term of 75 percent rule forsubspecific discrimination.
For the detail, refer to Hayami (1969),
Hayami and Matsukuma (1971) and Noda
(1975).

Table 5.

197

Results of analysis
The samples A, B and C are the representa.
tives for the forma a, (3 and 'Y of I. japonicus
respectively. The results of measurements areshown in Tables 2, 4 and 6, and their statistics
are in Tables 3 and 5. The sample C consistsof two specimens, one of which is the lectoFYpe.
1. Correlation between the simple ratio hll at
the growth stage of 90 mm in H and the simple
ratio HL/h at the same growth stage. - Plotting
the ratio hll in ordinate and the ratio HL/h in
abscissa, the rejection ellipses of the samples
A and B are shown in Text.fig. 5a in accordancewith Table 7a. As is demonstrated in Text.fig.
5a, the rejection ellipses of the two samples
drawn at 68 percent confidence level scarcely
overlap each other. Due to the small size ofsamples and the large variation, the ellipses are

Numerical characters of sample B (Haboro).

ah/l H =90mm

HL/hH =90mm

R.D· H =90mm

tano H =90mm

N

7

6
( 5)

5

5

5

m

109.7

1.065
(1.056)

0.518

0.136

1.33938s

6.32

0.0720(0.0767)

0.0356

0.0336

0.198445

v

5.76

6.76
(7.26 )

6.87

24.71

14.82

) .. figures of h/ 1'1i=90mm used for rejection ellipse
For others see the reference of Table 3.

Table 6. Measurements of Sample C (Kuji).
specimen

valve

h

1

H

HL

Q

Ii

Ra. Rp

UMUT-MMS524[- 1-1013]

L, R

100.5

113.2

133.4

59.3

10S o

500

9, 5

specimen

valve

H/l

H/l H_90mm

HL/h

HL/hH_90mm

R.D· H_9Omm

tanli H_90mm

UMUT-MMS524[- 1-1013]

L, R

0.89

0.83

0.59

0.S8

0.12

1.110SMasayuki NODA

198

encircled on a large scale, but the dots of thetwo samples are not mixed with each other onboth of the ordinate and the abscissa.
2. Correlation between the tangent S at thegrowth stage of 90 mm in H and the divergent
rib density at the same growth stage. - Plotting
the value of tanS in ordinate and the rib density
in abscissa, the rejection ellipses of the, twosamples are shown in Text-fig. 5b according
to Table 7b. As is evident from Text-fig. 5b,
the ellipses at 68 percent confidence level ofthe two samples are clearly separated. But thedots of divergent ribs are overlapping in abscissa.
3. Result of Student's t-test. - As is shown in
Table 8, the results of F-test for selected characters, i.e. anterior-hinge angle a, simple ratio hi
IH=90mm, simple ratio HL/hH =90mm, R.D· H=90mm
and tanS H =90mm are not significant in a pairof samples A and B. Thus, for the Student's
t-test, the Welch's method is not adopted.
The results of the Student's t-test for theselected characters are shown in Table 9A, B,
C, D and E respectively. In the characters ofhll and HL/h, the t-values are all significant at
5 percent significant limit, and these characters

Table 7a. Data of rejection ellipse (h/l, HL/h).
sample

X

Y

e

A

0.345

1.224

116°29'20.3mm 18.5mm

B

0.518

1.056

98°14'

42.8mm 18.4mm

~b

All

X : mean of simple ratio of HL/h at the growthstage of 90mm in H
Y : mean of simple ratio of hll at the growthstage of 90mm in H
8 : inclination of long axis
Xa : length of long axis
Xb : length of short axis
Table 7b. Data of rejection ellipse (tanS, R.D.).
sample

X

Y

e

A

0.204

2.841

91°18'

33.9mm 24.5mm

B

0.136

1.339

49°14'

22.8mm 14.6mm

~b

All

X : mean of divergent rib density at the growthstage of 90mm in H
Y : mean of tanS at the growth stage of 90mm
in H
For others see reference of Table 7a.

tan

h/I
1.3 0

II

/'

o
1.2 0

\

J..--

~

~ VV

A
0
0

""

r--- l----'

I/

/

[\

L---

/

:u 0

0

r---- l"-

\
J

0

\

2.5 0

1.1 0

'\

A

0

3.0 0

. \

/;

,

II

[\

\

1.0 0

~

•

\

B

•

./

rJ

1\

0 .• 0

1.50

\

J

~ 7"

0.8 0
0.20

0.30

0.!i0

C.)

0.60 Hl/h

1.00

o.00

...-l/o............

2.0 0

II

/

---

.......

. • 1
)

B

. • /

V

~O.20

0.30

Text-fig. 5a. Rejection ellipse showing at 68 percent confidence level (h/l, HL/h).
5b. (tanS, R. D.). A: 1. (Pl.) higoensis, B: 1. (Pl.) japonicus hokkaidoensis, C: I. (Pl.) japonicus japonicus.

0."0

R.D.

769. Inoceramus japonicus

199

Table 8. F-test for selected characters between samples A and B.
a

F-value 1.4704

h/IH =9Omm

HL/h H =90mm

R.D· H =90mm

tan8 H =9Omm

2.00261.81803.27454.6053

Table 9. Student's t-test for selected characters.
A

9A

A
Ci

-

-

A

B

C

4.71736.8536

B

0

C

0
A

A

3.02170BC

6.9587

6.57804.1542

0

C

0

0

A

B

C

2.27641.2923A

0.1087

B

0

C

-

-

A

B

9E

6.3888Ao : significant

0.2516B

9D

tan6 H =90mm

1.1616C

9C

R.D· H =90mm

1. 7516-A

HL/hH=90mm

C

B

9B

h/lH =90mm

B

B

0

C

0

C

3.80091.0524-- : not significant

show small values in Pearson's coefficient ofvariation. This fact is remarkable for infraspecificdistinction.
As is clear in Tables 3 and 5, the divergent
rib density and tan8 show considerably wide
variations, but the t-values of those characters
are yet both significant in a pair of samples
A and B, also significant in tan8 of sample A
and C. These are notable for morphologic distinction too. The t-values between a pair ofsamples A and C, B and C, are not significant
in rib density, and that between samples B andC, not significant either in tan8.
4. Analysis of the relative growth. - For samples
A and B an average relative growth and forsample C an individual relative growth are drawn
in Text-fig. 6, because sample C consists ofa single specimen, for measurements.
As is evident from Text-fig. 6, in the relative
growth of I and h, the reduced major axis ofevery sample is monophasic without criticalpoint. The relative growth of bivalvia, however,generally show abrupt change at a certain growthstage in various characters.
Although there may be some problems tocompare the average relative growth with theindividual relative growth, depending on thedata of Table 10, the results of analysis forthe slope of reduced major axes of each sample
are shown in Table 11.
K-value (see Hayami and Matsukuma, 1971)of two pairs between A and B, and A and C are
2.26 and 2.68, respectively, which are higher
than 1.96 and indicate significant differences
at 95 percent confidence level, although thevalue between B and C does not indicate asignificant difference.
For the difference of Y intercept of the
reduced major axis (which shows insignificant
value in slope) the K-value is 9.02 which issignificant at 95 percent confidence level.
5. Result of evaluation for the 75 percent rule.
- The 75 percent rule is applied for the selectedcharacters in a pair of samples A and B. The
results are shown in Table 12.
As is clearly shown in Table 12, the coefficient of difference for the simple ratio HL/
h H =90mm between samples A and B is 2.07
which is more than 1.28 the conventional levelof the 75 percent rule for the subspecific distinction, and also it shows a significant value
in tan8. It is slightly less than significant limit
1.28 in the simple ratio h/l. The anterior-hinge
angle a and the rib density are net significant.

Masayuki NODA

200

c

B

A
I =l.851 hO. 7IB

1= 2.061 h 0.B28

1=2.2141"1°·861

r=O.9928

r=O.9881,= 0.9936

O"1O+"----,---3,-~.~S~'~7T8T'~1O"~h 10",,+"----~--~~.-'-S-'~7~8~'~1O-;-,-'-hText-fig. 6. Reduced major axis of h to I (in mm) for each sample. A: averaged relative
growth of sample A, B: averaged relative growth of sample B, C: individual relative growth ofsample C (UMUT. MM6524).
Table 10. Data of analysis of allometry.
sample

a

~

lo~

h

I

r

a

N

A

0.718

2.851

0.455

48.2

43.5

0.99280.0238

13

B

0.828

2.061

0.314

66.1

64.3

0.9881

0.0424

9

C

0.861

2.241

0.345

42.4

54.1

0.99360.0325(9)~ : growth index (slope of the reduced major axis), ~ : Y intercept,

h: mean of shell height,
I : mean of shell length, r : correlation coefficient, a : standard error, N: sample size
sample C : showing individual relative growth, parenthesized number: growth stages.

Table 11. Significance test for the difference ofslopes between a pair of reduced major
axes.
A
A
B

0

C

0

B

C

*2.26

*2.68
0.62

-

* : significant, 0 : significant,- : not significant

Sepcific and subspecific distinction
Nagao and Matsumoto (1940) discriminatedthree forms in a species of I. japonicus, that is,forma a, ~ and 'Y, and Matsumoto and Ueda in
Ueda (1962) suggested that the statistical examination is necessary to elucidate the variation
in a species and the relationship with allied
species from other provinces.
The Student's t-test is an effective method
for the examination of the difference by meansof the biometrical characters in infraspecificdiscrimination, and also the K-test is applicablefor the above characters. The former is morereliable than the latter for small samples but
the latter is effective only for large samples.

769. Inoceramus japonicus

201

Table 12. Coefficient of difference for the selected characters of a pair of samples A
and B.

C.D.

ah/I H =9Omm

HL/hH =90mm

R.D· H - 9Omm

tan5 H 90mm

0.42

1.26

*2.07

0.72

*2.40

C.D. : coefficient of difference,* : significant

Table 13. Data of approximate determination of infraspecific category.
Sample A

Sample B

Sample C

1 1213'14 15 16 1 2 3 4 5 6 1 2 3 4 5 6
t-testSample A000t-testK-test-0

K-test75% rule

Sample B

-

0

0

-

0

0

-

I:l 0

-

0

0

-

0

0

- 0

75% rule
1 : a, 2: h/IH =9Omm' 3 : HL/hH =90mm' 4 : R.D' H =9Omm' 5: tan5 H =9Omm'
6 : 1=~O:, 0 : significant, I:l : less significant, - : not significant

The 75 percent rule is a conventional method
for the subspecific distinction in terms of thebiometrical characters, and it is not affectedby sample size as the Student's t-test. The resultof the Student's t-test does not always agreewith that of the 75 percent rule as has been
already remarked by Hayami (see Hayami,
1969, p. 86).
The short cut method is very effective for thecharacters which are unsuitable for numericalexamination, for example, the surface ornamentation and presence or absence of a certain
character. But in the present study, the short
cut method is not applied (see Noda, 1975,
p.247).

The' results of the above examination arequite adequate for the taxonomic distinction of
the infraspecific category. They are summarizedin Table 13.
In Table 13, both the simple ratios hll and
HL/h show significant values in the Student's

t-test for the samples examined and the two
characters show small values in the Pearson's
coefficient of variation. The patterns of relative
growth between h and I show significant value
in K for slope and intercept of the reduced
major axes. These facts must be sufficient formorphologic distinction.
A serious question, however, arises. As Nagao
and Matsumoto (1940) have recorded, the specimens of forma a are rarely found in Hokkaido
and South Saghalien where those of forma ~are common. It is biologically unreasonable
to discriminate subspecifically various forms ina species obtained from synchronous deposits
of one and the same area.
As is clear from the Tables 11 and 13, sample
A, the representative of forma a, is very distinct
from other two samples. Especially the factthat the difference of slope of the reduced
major axis is significant in K-value in pair ofother samples respectively indicates that theMasayuki NODA

202

forma a should belong to a different lineage
from that of two other samples. The former
is most probably discriminated specificallyfrom the latter.
Nagao and Matsumoto (1940) made 1. japonicus forma a relate to I. incertus var. yubarensis,
whereas Matsumoto (1959) mentioned therelationship between 1. japonicus and I. ezoensis.
Furthermore, I obtained subsequently more
useful data for the consideration of phylogeny
from the same localities in Southwest Japan.
From the fact mentioned above, I consider
that it is reasonable and natural to divide theso-ealled I. japonicus into two independent
species and two subspecies of I. japonicus itself
as will be described below. They correspond
approximately to forma a, ~ and 'Y of Nagao
and Matsumoto (1940).
Subgeneric assignment
Nagao and Matsumoto (1940) included I.
japonicus in the group of 1. ezoensis, since they
avoided to use the subgeneric names which were
under a confused condition at that date.
Heinz (1932) proposed to use the subgenericnames Platyceramus and Cladoceramus, butthey were both nomen nudum in accordancewith the International Code of Zoological
Nomenclature, because he gave no diagnosisof the two subgernera and no designation of
the type-species of Platyceramus. Heinz (1932)
designated 1. michaeli Heinz (= I. digitatus
SchlUter, 1911, revised to I. undulatoplicatus
michaeli by Seitz, 1961,nonI. digitatus Sowerby,1877) as the type-species of Cladoceramus.
Seitz (1961) gave the diagnosis of Platyceramus an d Clad oceramus an d designate d I. man tellid'Mercy (Barrois), as the type-species of Platyceramus. Consequently the subgeneric names
have obtained the availability and validity
since that date, as Matsumoto, Noda and Kozai(1982) already mentioned. Thus, the authorname for these defined subgeneric names is
Seitz, 1961.
Seitz ascribed I. ezoensis and I. ezoensis
vanuxemiformis (revised to I. cycloides vanu-

xemiformis by Seitz) to Platyceramus and 1.
japonicus to Cladoceramus.
Notwithstanding the validity obtained since
Seitz's revision, Vokes (1967) wrongly regarded
these name as being invalid, and Cox (1969)
inadequately recorded Pia tyee ramus as juniorsynonym of subgenus Inoceramus and Cladoceramus as that of genus Sphenoceramus.
I should support Seitz's revisions for thefollowing reasons. Platyceramus must be separated from subgenus Inoceramus, because theformer is equivalve but the latter is inequivalve.
This character is one of the fundamental characters for the subgeneric or generic distinction.
Sphenoceramus is clearly discriminated from
Cladoceramus in that the posterior wing isdistinctly demarcated from the main part ofshell in the former, but gradually flattened
without sharp boundary in the latter, among
other points. In Seitz's (1961) concept, thedistinction between Platyceramus and Cladoceramus is quite delicate. They are similar toeach other in the marginal outline, shell convexity and curvature of concentric ornaments.
The divergent ribs are commonly undevelopedor less prominent, if present, than concentricones in Platyceramus, whereas the divergent
ribs are said to be predominant in Cladoceramus.
But in the C3Se of the intermediate form linking
them, the subgeneric assignment to either ofthem would be difficult.
I have assigned all the species belonging to
the group of 1. naumanni to Sphenoceramus,
regardless of the presence or absence of divergent
ribs. Likewise, the species of Sphenoceramus
from Europe have· been assigned to the same
genus, regardless of the presence or absence ofradial ribs. Thus the presence or absence ofdivergent ribs is not so important as a genericor subgeneric criterion.
The specimens illustrated in Text-fig. 7,
taken from the same bed (Sample A-1), probably
represent a certain population. It is impossible
to discriminate one from another not only
subglmerically but also specifically at populationlevel. From the above discussion, the distinctionof the two subgenera by the degree of develop-

769. Inoceramus japonicus

203

Text-fig. 7. Variation of surface ornamentation in Inoceramus (Platyceramus) higoensis
sp. nov. The specimens illustrated were taken from a single bed of Loc. H1l023 .
A: concentric ribs only, B: special form with posterior divergent ribs only, C: weak divergent
ribs developed, D: typical form, E: "michaeli type" with less numerous and strongly curved
posterior ribs. A, Band C may be immature. A, B: natural size, C, D and E: x O. 7 5.

ment of divergent ribs is unnatural and unreasonable_ It is better to unite the two nominal
subgenera.
It is desirable to adopt Platyceramus, which
has clearly page priority over Cladoceramus, inaccordance with Article 24, (a), Advice 24A of
I.C.Z.N.
Palaeontological description
Family Inoceramidae Giebel, 1852
Genus Inoceramus Sowerby, 1814
Subgenus Platyceramus Seitz, 1961

Inoceramus (Platyceramus) japonicus
Nagao et Matsumoto
Lectotype:-The specimen figured by Nagao
and Matsumoto (1940, pI. 9, fig. 1: reillustrated

in this paper, PI. 1, Fig. 1), was designated by
Matsumoto and Ueda (1962), from Kunitan,
Kuji City, Iwate Prefecture, Kunitan Formationof the Kuji Group , collected by Yasuo Sasa andkept at University Museum of the Universityof Tokyo (UMUT.MM6524 = TK.I-1013).
Specific characters.-Shell equivalve, fairly
large in size. Umbo small, subterminal andslightly prominent but not incurved. Shell
convexity gentle and uniform, anterior partcomparatively steep, posterior one gradually
flattened, passing into a wing-like area. Marginal
outline considerably variable as described below.
Surface ornamentation consisting of concentric and divergent sculptures; the former
are numerous, fine and low minor concentricrings and major concentric ribs in combination,
the concentric ribs regular in size, intensityand distance. Divergent sculpture composed ofMasayuki NODA

204

Text-fig. 8. Illustration of Forma Q , (3 and 'Y of so-called I. japonicus Nagao et Matsumoto(1940). 1: forma 'Y = I. (Pl.) japonicus japonicus Nagao et Matsumoto, 2, 3: forma (3 = 1. (Pl. )japonicus hokkaidoensis subsp . nov. showing the variation of marginal outline and surface ornamentation, 4: forma Q = I. (Pl. ) higoensis sp . nov. 1: xO.4, 2 : xO.3 , 3: xO.6, 4: x O.5.

--

Table 14. Ontogenetic change of obliquity in 1. (Pl. ) japonicus japonicus.

growth stage

H=10mm

20mm

30mm

40mm

50mm

60mm

70mm

90mm

110mm

140mm

170mm

56·

53·

52·

52·

52·

52·

51·

50·

49·

47·

44·

specimen

UMUT.MM6524

round-headed ribs separated by concave interspaces which are as wide as the ribs; the divergent
ribs appearing in a more or less late growth stage,
those of the posterior half of the valve commonly developing later and often less numerous
than the anterior ones. Nodulous elevations
developed at the intersection of the concentricand divergent ribs.
The present species is, herein, subdivided
into two subspecies as follows:
Inoceramus (Platyceramus) japonicus
japonicus Nagao et Matsumoto
PI. 41, Fig. 1; Text-fig . 8A

1940. Inoceramus japonicus (Sasa MS) Nagao
et Matsumoto, Jour. Fac. Sci., Hokkaido
Imp. Univ., [4}, vol. 6, no. 1, p. 24-28,
pI. 9, fig. l.
1959. Inoceramus japonicus : Matsumoto, Mem.
Fac . Sci., Kyushu Univ. , [D}, vol. 9,
no . 2, p.86, pI. ll , fig. f.
1962 . Inoceramus japonicus: Matsumoto andUeda in Ueda, Mem. Fac. Sci., Kyushu
Univ., [D} , vol. 12, no. 2, p . 165, pI. 24,
fig. l.
1975 . Inoceramus (Cataceramus) japonicus: Hayami, Univ. Mus. , Univ. Tokyo, Bull.
no . 10, p. 57 , pars.

769. Inoceramus japonicus
Material:-UMUT.MM6524 [= TK.I-1013]
and UMUT.MM6924 [= TK.I-1011] from thetype locality.
Subspeci{ic diagnosis.-Very oblique, withthe obliquity gradually increasing with growth
and the growth axis convex anteriorly as shownin Table 14. Much elongated from the umbo
to the postero-ventral extremity. Antero-dorsal
margin convex, postero-ventral margin rather
broadly rounded in juvenile stage and morenarrowly curved with growth; the posterior
one widely rounded passing into nearly straight
postero-dorsal margin. Hinge-line long, about
a half of shell length, forming an obtuse angleof about 140° with the postero-dorsal margin.
Remarks. -The present subspecies corresponds
to forma 'Y of Nagao and Matsumoto (1940).
Inoceramus (Platyceramus) japonicus
hokkaidoensis subsp. nov.

PI. 41, Fig. 2; PI. 42, Figs. 1-3;
PI. 43, Figs. 1-3; Text-fig. 8B, C.
1940. Inoceramus japonicas (Sasa MS) Nagao
et Matsumoto, Jour, Fac. Sci., Hokkaido
Imp. Univ., [4J, vol. 6, no. 1, p. 24-28,
pL 7, fig. 2, pl figs. 2-4.
1969. Inoceramus japonicus: Katto, Geology of
Kochi Prefecture. p. 132, fig. 97 (inJapanese).
1975. Inoceramus (Cataceramus) japonicus: Hayami, Univ. Mus., Univ. Tokyo, Bull.
no. 10, p. 57, pars.
1976. Inoceramus japonicus: Noda and Matsumoto, Atlas of Japanese fossils. no. 45268, Cr. 34, fig. 2 (in Japanese).
1978. Inoceramus (Cladoceramus?) japonicus:
Matsumoto and Haraguchi, Trans. Proc.
Palaeont. Soc. Japan, N. S., no. 110,
p. 317, listed.
1982. Inoceramus (PIa tyceram us) japonicus:
Matsumoto, Noda and Kozai, Palaeont.
Soc. Japan, Special Papers, no. 25, p. 62,
pI. 10, fig. 6.
Types.-Holotype: MC510621 from Loc.
IK8015, upper reaches of Kikume-zawa, atributary of the River Ikushumbetsu, near theLake Katsura-zawa, Ikushumbetsu area, Mikasa

205

City, Hokkaido (colI. Kikuo Muramoto). Str.
position: Upper part of Member HId, Upper
Yezo Group (for the stratigraphic sequence
see Matsumoto, 1965, text-fig. 4). Paratypes:
JG.H2805, 2806 and 2807, not far from thetype locality (colI. Noda, Matsumoto and Takahashi). JG.H01l5, 0176 and 2738 from Loc.
Hb1997; JG.H2739, 2740 from Loc. Hb2000.
JG.H2741 from Loc. Hb2001; Migino-sawa,a tributary of the River Haboro, Haboro-machi,
Tomamae-gun, Hokkaido. Str. position: Unit
C . of Upper Yezo Group (in Inoma's sense,
see Matsumoto et al., 1972) (colI. Noda, Matsumoto and Takahashi, 1977); GK.H10027 from
Loc. H2 of Matsumoto (T1006g of Tanabe)a road cutting on the left bank near Tomiuchi
Bridge, Hobetsu-machi, Yufutsu-gun, Hokkaido(colI. Tanabe and Hirano, 1975). Str. position:
upper part of Upper Yezo Group (see Matsumoto, 1942); GK.H10079 from Panke-zawa,a tributary of the Riber Chikubetsu, Tomamaegun (colI. Ueda). Str. position: lower part of D
Formation of Ueda et al. (1962), Upper Yezo
Group; GK.H10105 from Loc. SK62, upper
reaches of the River Haboro, Sankei area, Tomamae-gun (colI. Tanaka). Str. position: lower
part of Unit F (= Unit U5 of Yamaguchi andMatsuno, 1963), Upper Yezo Group.
Material.--.Jfhe type specimens cited above
are concerned with description and measurements.
Subspeci{ic diagnosis. -Shell nearly as highas long, moderately oblique, with constantobliquity through all the growth stages andan almost straight growth axis as shown in
Table 15. Antero-dorsal margin long and straightor slightly concave, the anterior one broadly
curved passing gradually into the widely roundedventral one. Postero-ventral margin moderately
rounded; posterior margin gently arcuate forminga very obtuse angle of about 135°-150° withthe hinge-line, which is fairly long, more than
two fifths of shell length. In the general aspect,
the marginal outline is fan-shaped.
The surface ornamentation as for specificdiagnosis, the divergent ribs are of variable
intensity among individuals, on some individuals

206

Masayuki NODA
Table 15. Ontogenetic change of obliquity in 1. (Pl.) japonicus hokkaidoensis.

----

H=10mm

20mm

30mm

40mm

50mm

60mm

70mm

90mm

JGH2738

50°

50°

51°

51°

50°

51°

51°

52°

JGH2739

60°

60°

60°

61°

61°

61°

60°

60°

60°

JGH2743

50°

50°

50°

GK.H10027

57°

57°

60°

59°

60°

60°

61°

59°

61°

growth stage
1l0mm

140mm

specimenanterior divergent ribs much more numerous
than posterior ones which are widely undulated
and strongly curved posteriorly as on the specimen of JG.H2806.
Remarks. -The present su bspecies corresponds
to forma (3 of Nagao and Matsumoto (1940),
and is readily distinguishable from 1. (Pl.) japonicus japonicus in its straight antro-dorsal marginand straight growth axis bisecting the anteriorhinge angle. In these respects, the present subspecies is somewhat similar to 1. (PI.) undulatoplicatus Romer, but careful comparison is needed(see next chapter).
Occurrence. -1. Abeshinai area of Nakagawa-machi, Nakagawagun (Teshio), Hokkaido. Str. position: Unit
IIId of Upper Yezo Group.
2. Migi-no-sawa, upper reaches of River Haboro(see types JG.H0115, 0176, 2738-2741).
3. Panke-zawa, Chikubetsu area (see paratype
GK.H10079).
4. Kikume-zawa, Ikushumbetsu area (see holotype and paratypes JG.H2805-2807).
5. Oyu bari area. A cliff along the railway at
Kashima-sennen, Y1001d2, at the entrance ofPankehorokayuparo-zawa and Y1559a and Y1561
of Omaki-zawa, Yubari City, Hokkaido. Str.
position: upper part of Member IIId, Upper
Yezo Group (see Matsumoto and Haraguchi,1978).
6. H2268, A cliff about 200 m downstream ofNakahobetsu Bridge, Inasato I, Hobetsu-machi,
Yufutsu-gun, Hokkaido. Str. position: upper
part of Upper Yezo Group.
7. A cliff near the Tomiuchi Bridge, Hobetsumachi (see paratype GK.H10027).

61°

8. West of Frenai, Saru-gun, Hokkaido. Str.
position: upper part of Upper Yezo Group(near the key bed of tuff), (coH. Kido and H.
Matsumoto).
9. Urakawa area, Urakawa-gun, Hokkaido. Str.
position: Unit U1 of Kanie (1966) (probably
its upper part, see Matsumoto and Kanie, 1979),
of Upper Yezo Group.
Inoceramus (Platyceramus) higoensis sp. nov.
PI. 44, Figs. 1, 2;PI. 45, Figs. 1,2;
PI. 46, Figs. 1-6; Text-figs. 4,7 A-E and 8D.

1940. Inoceramus japonicus (Sasa MS) Nagao
et Matsumoto, Jour. Fac. Sci., Hokkaido
Imp. Univ., [4], vol. 6, no. 1, p. 24-28,
pI. 5, fig. 2; pI. 6, figs. 2,3; pI. 9, fig. 2.
1962. Inoceramus japonicus: Matsumoto andUeda, Mem. Fac. Sci., Kyushu Univ.,[D], vol. 12, no. 2, p. 165, pI. 22, fig. 4.
1975. Inoceramus (Cataceramus) japonicus: Hayami, Univ. Mus., Univ. Tokyo, Bull.
no. 10, p. 57, pars.
1976. Inoceramus japonicus: Noda and Matsumoto, Atlas of Japanese fossils. no.45268, Cr. 34, fig. 1 (in Japanese).
1982. Inoceramus (Platyceramus) japonicus:
Matsumoto, Noda and Kozai, Palaeont.
Soc. Japan, Special Papers, no. 25, p. 62,
pI. 11, figs. 1,2.
Types.-Holotype: JG.H2727 from Loc. HI
1009, a northern shore of Kojima, Himedomachi, Amakusa-gun, Kumamoto Prefecture;
Str. position: lower part of Middle Formation, Lower Subgroup, Himenoura Group.
Paratypes: JG.H2701, 2702, 2708, 2709, 2712
and 2713 from Loc. HIl023, a western beach769. Inoceramus japonicusof Kugushima, Ryugatake-machi, Amakusa-gun;
Str. position: upper part of Middle Member,
Lower Subgroup, Himenoura Group. JG.H2719,
2720, 2736, 2737, 2745 and 2746 from thetype locality. OES41001, 14047 and 14103
from the upper reaches of the River Kajisako,
Monobe area, Kami-gun, Kochi Prefecture,
Shikoku; Str. position: upper part of the Kajisako Formation. HK7134 from Kawakami,South Saghalien; Str. position: precisely unknown. HK7232 from Wakkawen, Nakagawamachi, Nakagawa-gun, Hokkaido; Str. position:
Unit I1Id of Upper Yezo Group.
Diagnosis. -Shell equivalve of moderate sizeor considerably large. Umbo subterminal. Convexity of valve gentle and uniform, anterior
part comparatively steep, posterior one gradually
flattened, passing into a wing-like area, posteroventral portion more or less flattened. Longer
than high in juvenile stage, becoming graduallyhigher with growth and much higher than longat the adult stage. O~liquity not conspicuous,decreasing with growth as shown in Table 16,
with the growth axis concave anteriorly. Anterodorsal margin slightly convex, the anterior one
long and broadly arcuate, passing into themoderately rounded ventral one; the broadly
arcuate posterior one continuing to the longand broadly rounded postero-dorsal one, forming
an obtuse angle of about 115°-130° with thehinge-line. Hinge-line rather short, about a halfof shell length at an early stage, becoming
gradually smaller in simple ratio to shell length,--H-10mm

20mm

30mm

40mm

JGH2701

48'

58'

61 '

63'

JGH2702

51 '

54'

56'

JGH2708

47'

50'

52'

53'

JGH2712

42'

43'

46'

53'

JGH2713

44'

50'

54'

57'

Table 16.

207

less than one third of shell length at the adultstage. In the general aspect, the marginal outline
fan-6haped in the young shell and high oval in
the adult one.
Surface ornamentation consisting of concentric and divergent sculptures; the former
are numerous, fine and low minor concentricrings and major concentric ribs in combinatio'n.
The concentric ribs regularly increasing in size,
strength and distance, before the appearanceof the divergent sculpture, round-headed andseparated by concave interspaces as wide as
the ribs. Divergent ribs appearing in a more orless late stage of growth; those of the posterior
half of valve commonly developed later than
the anterior ones. Anterior divergent ribs frequently bifurcate and inserted; posterior ones
less numerous and stronger than the anteriorones, widely undulated and strongly curved
posteriorly. Occasionally some of the posteriorribs tend to be united near the margin. On thelater part of the shell where the divergent ribs
predominate, the concentric ribs are weakened
but the minor rings and growth lines are distinct.
When the divergent ribs are as strong as theconcentric ribs, the numerous nodulous elevations at the intersection.
Remarks.-The present species corresponds
to forma a of Nagao and Matsumoto (1940).
The high elliptical outline, a shorter hinge-iine,
less obliquity and smaller posterior-hinge angle
enable us to distinguish this species from 1. (Pl.)
japonicus emended above.

Ontogenetic change of obliquity in 1. (Pl.) higoensis.

growth stage
50mm

60mm

70mm

90mm

56'

59'

63'

65'

61 '

67'

71'

74'

1l0mm

140mm

170mm

200mm

specimen

73'

JGH2720

44'

47'

54'

57'

60'

63'

66'

72'

72°

71'

70°

JGH2736

50°

52'

55'

56'

58'

62'

64'

69'

67'

70'

70'

70'

JGH2737

50'

54'

58'

62'

65'

67'

68'

70'

74'

74'

75'

73'

Masayuki NODA

208

Table 17. Measurements of I. (Pl.) higoensis subsp. linear dimension in mm.
specimen

valve

h

I

H

HL

0:

6

Ra, RpHK7134

RV

75.2

59.1

82.0

25.0

114°

63°

8,6

HK7232

RV

75.0

59.9

81.7

25.0

117°

63°

9,6

HK7252

RV

79.5

65.0±

88.0±

HK5931

RV

65.5

61.2

78.0

25.5

specimenh/lh/lH=9Omm

HL/h

HL/hH=90mm

R.D.H=9Omm

tan6 H=9Omm

HK7134

1.27

-

0.33

-

-

-

HK7232

1.25

-

0.33

-

-

HK7252

1.22±

-

0.36±

-

-

-

HK5931

1.07

-

0.39

-

-

-

The species included two fonns; one is represented by the specimens from Southwest
Japan, for example, the sample A in the present
study, and the other is a fonn from Hokkaido
and Saghalien, for example, the specimens
figured by Nagao and Matsumoto, 1940, pi. 5,
fig. 2; pi. 6, fig. 2; pi. 9, fig. 2. The fonner ischaracterized by less conspicuous umbo andcomparatively crowded divergent ribs, whereas
the latter by a much projecting umbo beyond thehing-line and coarser divergent ribs. The measurements of the latter are shown in Table 17 andthe relative growth between I and h is demonstrated in Text-fig. 9. For the slope of theimcomplete

1_ 3 177hO 085,- 09928

Text-fig. 9. Reduced major axis of h to 1
for Inoceramus (Platyceramus) higoensis subsp.
(HK7134).

Explanation of Plate 41
Fig. 1. Inoceramus (Platyceramus) japonicus japonicus Nagao et Matsumoto. natural size.
UMUT-MM6524 [= TK.I-1-13], lectotype. Kunitan, Kuji, Iwate Prefecture, Kunitan Formation, Kuji Group (colI. Y. Sasa).
Fig. 2. Inoceramus (Platyceramus) japonicus hokkaidoensis subsp. nov. xO.5. MC.520621, holotype. Loc. IK8015, Kikume-zawa, Ikushumbetsu area, Mikasa City, Hokkaido. Upper partof IUd, Upper Yezo Group (colI. K. Muramoto).
UMUT: University Museum, University of TokyoMC:
Muramoto Collection

769. Inoceramusjaponicus

reduced major axis to that of the sample A,
the K-value is 0.897 which is less than 1.96 at
the 5 percent significant limit but the position(Y intercept) is significant (K=5.38). The twoforms are geographically separated from eachother, the subspecific discrimination, therefore,
would be possible_ But I reserve, at present, togive a subspecific name because of the insufficient record of occurrence for the latter.
Sample A-1 is variable both in the intensity
and in the appearing stage of divergent ribs, as
demonstrated in Text-fig. 7. Some specimens,
e.g. JG.H2708, have scarcely discernible divergent ribs, whereas the specimens JG.H2712
and 2713 have predominant ones regardlessof early growth stage, and these specimens
occurred together in the same mudstone bed.
Due to the small size of sample, the evaluationof population sample by the statistical method
is impossible. Sample A-1, however, probably
represents one population, because they arelinked with various grades of intermediate ornaments. A specimen JG.H2719 (PI. 45, Fig. 2),
shows peculiar ornaments, with fewer and morestrongly curved posterior divergent ribs. There
are, however, some intermediate forms linking
the typical form (see Pis. 44-46 and Table 2).
Occurrence_I. Loc. HU008, a cliff of the sea shore at
Motogama, Himedo-machi, Amakusa-gun, Kumamoto Pref.; Loc. HU009 (= K25 by Ueda, 1962),
the type locality; Loc. HU015 (= K39 by Ueda,
1962), the back of the school (now abandoned),
Hongo, Himedo-machi. Str. position: lower partof Middle Formation, Lower Subgroup, Himenoura Group.
2. Loc. HU0l6, a cliff of road side at Washinosu,
Himedo-machi; Locs_ HU017, 1018 and 1019,
the road cutting along the mountain path from
Shitanuki, Ryugatake-machi, Amakusa-gun; Locs.
HU022, 1023 and 1024, the western beach of
Kugushima, Ryugatake-machi. Str. position:
upper part of Middle Member, Lower Formation, Lower Subgroup, Himenoura Group.
3. Loc. HS103, Mojirobana, Hirano, Higashimachi (Shishijima), Izumi-gun, Kagoshima Pref.;Loc. HS108, eastern shore of Shishijima, Higashi-

209

machi. Str. position: upper part of Lower Formation, Lower Subgroup, Himenoura Group(Yamamoto and Hayami, 1971).
4. Oda and the other localities found in the
Uto Peninsula, which seem to be referred toupper part of Lower Formation, Lower Subgroup, Himenoura Group.
5. Loc. M31, a right bank of the River Kajisako,
about 100 m upstream from the artificial lake;Kajisako, Monobe-mura, Kami-gun, Kochi Pref.,Shikoku. Str. position: Upper mudstone Memberof Kajisako Formation (Matsumoto, Noda
and Kozai, 1982, p. 63).
6. Loc. U129' (by Tanabe, 1972), Kawauchi,
Uwajima City, Ehime Pref., Shikoku. Str. position: upper part of Upper Member, Furushiroyama Formation, Uwajima Group.
7. A cliff on the right bank of Hobetsu River,
Nakahobetsu (Inasato I), Hobetsu-machi, Yufutsu-gun, Hokkaido. Str. position: upper partof Upper Yezo Group (Nagao and Matsumoto,1940).
8. Wakkawen, Nakagawa-gun, Hokkaido. Str.
position: Unit IIId of Upper Yezo Group (precisely unknown).
9. Kawakami, South Saghalien (in the Japaneseplace name, the Russian name unknown). Str.
position: precisely unknown.
Comparison with allied species
Inoceramus (Platyceramus) japonicus and 1.
(Pl.) higoensis resemble a wide.,spread species
1. (Pl.) undulatoplicatus Romer in many features,as Nagao and Matsumoto (1940) have alreadypointed out. Stephenson (1950) also recognized
the resemblance between 1. undulatoplicatusand 1. japonicus but mentioned that the Japanese
species has much coarser divergent ribs thanthe Euramerican species. Subsequently Matsumoto and Ueda (1962) remarked the distinction
between the two species and suggested thenecessity of the statistic study for identificaiton
or discrimination between them.
The measurements of the specimens of theallied species are shown in Table 18. The data
have been measured on an actual specimen

Masayuki NODA

210

Table 18. Measurements of specimens of l. (Pl.) undulatoplicatus. linear dimension in mm.
valve

h

I

H

HL

a

S

Ra • Rp

Bo3, Seitz

R

86.4

90.0

110.0

48.8

84'

46'

7 ,

6

S207WB, Seitz

R

147.2

124.8

166.1

45.7

85'

55'

8 ,

7

Hg49, Seitz

L

323.6

265.7

346.5

114.2

100'

60'

14 ,

9

no. 211, Sornay

L

289.8

217.7

300.9

63.9

104'

67'

13 , 11

specimenno. 229A, Sornay

L

176.0

179.2

213.6

98.6+

93'

45'

9 ,

6

GK.H9202

L

95.4

101.4

110+

59.6

79'

55'

9 ,

6

UT-30564, Young

L

188.0

141.2

214.8

74.4

99'

59'

10 ,

?

UT-30691 , Young

R

188.0

146.0

207.6

70,

89'

57'

15 ,

8

UT-30719, Young

R

211.6

182.0

238.4

95'

46'

6 , 10specimen

valve

h/l

h/lH-90mm

HL/hH=90mm

R.D·H=9Omm

tanOH=90mm

species

Bo3, Seitz

R

0.96

1.14

0.45

0.13

1.7321

1. undulatoplicatuB
undulatoplicatuB

S207WB, Seitz

R

1.18

1.09

0.54

0.13

1.4281

1. undulatoplicatus
undulatoplicatuB

Hg49, Seitz

L

1.22

1.00

0.61

0.12

1.1917

1. undulatoplicatus 8ubsp.

no. 211, Sornay

L

1.33

1.03

0.46

0.17

1.1917

1. aff. undulatoplicatuB
michaelino. 229A, Sornay

L

0.98

0.90

0.52+

0.13

1.0724

GK.H9202

L

0.94

0.96

0.64

0.14

1.3270

0.92
1.33

0.58

0.08

1.11060.53

0.17

1.53980.17

1.0355

UT-30564, Young

L

1.33

UT-30691, YoungR

UT-30719, Young

R

1.29
1.16

0.78

GK.H9209 from the Austin Chalk, Texas, andphotographs of other specimens from Texas(Young, 1963) and Madagascar (Somay, 1964,1969). It is, however, unable to examine asufficient number of extra Japanese specimens
to know the extent of variation.
Plotting the above data in the rejction ellipseof Text-fig. 5, they are mostly encricled in thedomain of Sample B, as demonstrated in Text-

I. japonicuB mammillatus

1. undulatoplicatUB
undulatoplicatuB
1. undulatoplicatu8
1. undulatoplicatus
1. undulatoplicatusfig. 10. From the above examination, it is understood that 1. (Pl.) undulatoplicatus and otherallied species are well agreeable with 1. (Pl.)
japonicus hokkaidoensis subsp. nov_ in the
numerical characters, but there are some disagreeable points in unmeasurable characters.
For example, the European specimens of 1. (Pl.)
undulatoplicatus described by Seitz (1961) areof rhomboidal outline with a subangular or

Explanation of Plate 42
Fig. 1. Inoceramus (Platyceramus) japonicus hokkaidoensis subsp. nov. natural size. JG.H2739,
paratype. Loc. Hb2001, Migi-no-sawa, a tributary of the River Haboro, Tomamae-gun,
Hokkaido. Unit C of the Upper Yezo Group (colI. M. Noda, T. Matsumoto and T. Takahashi).
Fig. 2. Inoceramus (Pl.) japonicus hokkaidoensis subsp. nov. natural size. JG.H2741, paratype.
Loc. Hb2002, near the Loc. Hb2001 (colI. ditto).
Fig. 3. Inoceramus (Pl.) japonicus hokkaidoensis subsp. nov. natural size. GK.H10027, paratype, Loc. H2[= T1006g by Tanabe], a left bank of the River Mukawa, near Tomiuchi
Bridge, Hobetsu-Machi, Yufutsu-gun, Hokkaido. HId Formation of the Upper Yezo Group(colI. K. Tanabe and H. Hirano).
JG: Jonan Geological Association
GK: Kyushu University

769. Inoceramusjaponicus
h/I
1.3 0

Ian I
,/

1.1 0

I---

II
o

1.2 0

\

~
u

r "" 1\

A
0
0

'-

b

2

..-/

1.00

S_

..

•

\

B

\

0.90

\

I

'\

\

2.50

2.00

.

a.
.6- r---

/

O.SO

_2

II

0.60 HL/h

1. 50

.~

II

/

\

J

"- r---..-

./

1

'\

0

1\
36

~

A

0

0

3.0 0

' -. /
0.30

I

9_

•

V-- r---.,

/

3.S 0

~ I~

\

0.10
0.20

211

.-/

l/o

I--r--_9

•,-

•
B-1

3- ~! _s
/
\ a.•

I

/

6 •• 1.t..lnA

1.00

o.00

~O.20

0.30

0040

R.D.

Text-fig. 10. Some allied species plotted in the rejection ellipses o'f Text-fig. 5a and b. 1:
UMUT.MM6524, 2: Bo. 3, 3: Hg49, 4: S207WB, 5: no.211, 6: no.229A, 7: GK.H9202, 8: UT30564, 9: UT-30691, 10: UT-30719. 0: I. (PI.) higoensis, e: I. (PI.) japonicus hokkaidoensis,~: foreign allied species. A: rejection ellipse of 1. (PI.) higoensis, B: rejection ellipse of I. (PI.)
japonicu8 hokkaidoensis.
narrowly rounded ventral margin, whereas
1. (Pl.) japonicus hokkaidoensis is fan-shaped.
As to the American specimens, the distinction
has already been remarked by Stephenson(1950), Seitz (1961) and Matsumoto (in Matsumoto and Haraguchi, 1978).
Inoceramus michaeli Heinz, 1932 (= 1. digitatus SchlUter, 1877; I. undulatoplicatus val.
michaeli Heinz, 1928; non 1. digitatus Sowerby,1829) somewhat resembles the specimens JG.H
2719 and JG.H2807 in that the posterior divergent ribs are much coarser, stronger and moreacutely bent than the anterior ones. Heinz(1932) discriminated specifically 1. michaeli
from 1. undulatoplicatus as an independent
species, but Seitz (1961) treated it as a subspecies of 1. undulatoplicatus.
In this study, the specimens of sample A,
illustrated in Text-fig. 7 and PIs. 44-46, show
a considerable variation in the divergent sculpture, in which the ornament of the pecuriar
form (Text-fig. 7E; PI. 45, Fig. 2) would be
regarded as the "michaeli type". The specimensof Text-fig. 7 (sample A-1) and PIs. 44 and 45(sample A-2) came from a single bed respectively ..
Thus, it is unreasonable to discriminate subspecifically the specimens with this type ofornament.
On the ground of population concept, they
are linked one with another by intermediate
forms. I consider, therefore, this kind of difference in divergent ribs is within the scope ofvariation in a single species 1. (PI_) higoensis.
The specimens called 1. (Pl.) aff. undulatoplicatusvar. michaeli from the Middle Santonian ofsouthwestern Madagascar (Sornay, 1964, p. 174,
fig. 6, 7) also resemble 1. (Pl.) higoensis, but
the former is distinguished from th~ latter inthe marginal outline with a small an terior-hinge
angle and its straight antero-dorsal margin.
A specimen JG.H2807 from Kikume-zawa,
is also "michaeli type". Although it was foundfrom a shaly bed about 20 m upper stream fromthe type locality of 1. (PI.) japonicus hokkaidoensis, it can be also included within the variationof a subspecies of 1. (PI.) japonicus hokkaidoensis, because the various grades of ornament
linking the typical form to "michaeli type"

212

Masayuki NODA

are found in the specimens collected fromthiS and adjacent areas (JG.H2805, 2806, 2807a,
2807b, MC510621, HK7239a, 7239b, 7240 and
TK.I-I019).
1. japonicus mammillatus Sornay (1969,
p. 218, figs. 10, 11) was established on a single
specimen (no. 229A) from the Middle or Upper
Santonian of southwestern Madagascar. Sornay
remarked the resemblance between this subspecies and the forma ~ of 1. (Pl.) japonicus[= 1. (Pl.) higoensis sp. nov. in this paper]. But
judging from his illustration, its longer hingeline, smaller anterior-hinge angle and larger
obliquity with a straight growth axis enable
us to distinguish it from 1. (Pl.) higoensis and
1. (Pl.) japonicus japonicus. In these respects,
that specimen (229A) is rather comparablewith 1. (Pl.) japonicus hokkaidoensis but clearly
distinguished from the latter in its more prominent umbo, slightly concave antero-dorsal
margin and smaller anterior-hinge angle.
1. japonicus var. antsohaensis Sornay (1964,
p. 172, figs. 4,5), from the Santonian of southwestern Madagascar, may belong to a different
stock of species, because its outline is muchelongated antero-posteriorly.
1. diversus Stoliczka (1871, p. 407, pI. 27, fig.
6), from the Trichinopoly Group of Anapaudy,
southern India is clearly discriminated fromthe group of 1. (Pl.) japonicus as have been
already mentioned by Nagao and Matsumoto(1940, p. 27).

A specimen from the Lower Santonian ofnorthwestern Germany was compared by Seitz(1961, p. 109, pI. 7, fig. 3) with 1. (Pl.) japonicus.
According to his illustration, it could be comparable with 1. (Pl.) higoensis in the developmentof surface ornamentations at earlier stage of
growth and the ontogenetic change of obliquity
but is clearly discriminated from 1. (PL) higoensis
in the straight antero-dorsal margin, smaller
anterior-hinge angle and longer hinge-line.
Anyhow, Seitz's specimen is not identical withany subspecies of 1. (Pl.) japonicus and 1. (PI.)
higoensis. In addition, the stratigraphic positionof the German specimen is geologically older
than that of the Japanese specimens.
Biostratigraphically 1. (PL) undulatoplicatuscharacterizes the Lower Santonian (Seitz, 1967
and many other authors), whereas 1. (Pl.) japonicus and 1. (PL) higoensis represent a particularzone of the Upper Santonian of Japan (Matsumoto, 1978 in Matsumoto and Haraguchi).
To sum up, I. (Pl.) japonicus and 1. (PL)higoensis is distinguished from 1. (PL) undulatoplicatus. Seitz (1961, 1967) and Sornay (1964,1969) have already recognized 1. japonicus as
distinguishable from I. undulatoplicatus on
their own reasoning.
Phylogenetic relationships
Inoceramus (Platyceramus) japonicus and I.
(Pl.) higoensis occur characteristically in the

Explanation of Plate 43
Fig. 1. Inoceramus (Platyceramus) japonicus hokkaidoensis subsp. nov. xO.8 GK.H10105, paratype. Loc. SK62, upper reaches of the River Haboro, Sankei area, Tomamae-gun, Hokkaido.
Lower part of Unit F of the Upper Yezo Group (colI. K. Tanaka).
Fig. 2. Inoceramus (Pl.) japonicus hokkaidoensis subsp. nov. xO.6. GK.H10079, Panke-sawa, atributary of the River Chikubetsu, Tomamae-gun. Lower part of HId Formation, Upper
Yezo Group (colI. Y. Ueda).
Fig. 3. Inoceramus (Pl.) japonicus hokkaidoensis subsp. nov. natural size. JG.H2738, paratype.
Loc. Hb1998, Migi-no-sawa, Haboro. Unit C of the Upper Yezo Group (colI. M. Noda, T.
Matsumomto and T. Takahashi).

769. Inoceramus japonicus

Upper Santonian in Japan, being effective zonal
indices. Nagao and Matsumoto (1940) remarked
that 1. japonicus evidently belongs to the stock
represented by 1. ezoensis Yokoyama and that
there is no essential difference between 1. incertus var. yubarensis Nagao et Matsumoto and1. japonicus forma a.
1. ezoensis occurs in the Lower to Upper
Santonian of Japan. Its range, therefore, overlaps
with that of 1. (Pl.) japonicus in the later half.
I

400

A

1'0

20

30

40

50

60

70

80

90

100

110

H mm

30

40

50

60

70

80

90

100

110

H mm

B

400

10

20

Text-fig. 11. Ontogenetic change of obliquity of I. (Pl.) japonicus and its allied species.
1: I. (Pl.) ezoensis, 2: I. (Pl.) japonicus japonicus,
3: 1. (Pl.) japonicus hokkaidoensis, 4: I. (Pl.)
yubarensis, 5: I. (Pl.) sp. aff. I. (Pl.) yubarensis(JG.H2706), 6: 1. (Pl.) higoensis.
Table 19.

213

The immature shell of 1. (PL) japonicus before
the appearance of divergent ribs is scarcely
distinguishable from that of 1. (Pl.) ezoensis.
1. (PL) higoensis is nearly contemporary with
1. (Pl.) japonicus, because it defined a zone inSouthwest Japan above the Zone of 1. (PL)amakusensis does so in northern Japan_ 1. (PL)higoensis is closely similar to 1. (PI.) yu barensis(independent species since Matsumoto andNoda, 1968, p. 320), from the Coniacian of
Hokkaido, in the shell.form, including thecomparatively smaller anteriorly concave growthaxis. The concentric major ribs are, however,much lower and less distinct in the later thanthose on the umbonal half of the former. In
this connexion, there is an undescribed form
which is provisionally called 1. (Pl.) sp_ aff.
1. (PL) yubarensis, from the Lower Santonianpart of the Himenoura Group (N oda ColI.,
JG.H2706, see Text-fig. 12). It resembles 1.
(Pl.) yubarensis but differs in surface ornamen·tation. Namely its major concentric ribs are
more distinct and regularly increased in· intensity and distance (or coarseness). It has nodivergent ribs, but otherwise it is very close
to 1. (Pl.) higoensis. Although the available
material is yet insufficient, this may represent
a transitional form from 1. (Pl.) yubarensis
to 1. (Pl.) higoensis.
From the above facts, as well as the onto-

Data of the relative growth (reduced major axis of h and I) of 1. (PI.)
japonicus and its allied species.

species

a

(3

log(3

r

a

N

A

0.947

1.104

0.043

0.99430.0320

10

B

0.714

2.698

0.431

0.99730.0166

10

C

0.833

1.841

0.265

0.99830.0146

11

D

0.718

2.851

0.455

0.99280.0238

13

E

0.828

2.061

0.314

0.9881

0.0424

9

F

0.861

2.241

0.345

0.99360.03259

A : I. (Pl.) yubarensis, B: 1. (Pl.) sp. aff. I. (Pl.) yubarensis, C: I. (Pl.) ezoensis,
D : I. (Pl.) higoensis, E : 1. (Pl.) japonicus japonicus, F: I. (Pl.) japonicus hokkaidoensis.

Masayuki NODA214

the above consideration.
For comparison, I would like to give some
remarks on the lineage of 1. (Pl.) undulatoplicatus. Woods (1912b) connected I. undulatoplicatus with the flat form of I. inconstans
Woods based on the resemblance of surface
ornamentation in the young shell. He regarded
I. (Pl.) undulatoplicatus as a descendant of
I. inconstans or a closely related species. Thereis, however, no connecing form between them,as he mentioned. I. inconstants described byWoods (1912a) shows a considerable extent
of variation and the extremely long range fromthe Lower Turonian to the Upper Campanian.
It is not a homogeneous species. Seitz (1967,
p. 93) revised the species, which belongs evidently to a stock different from the group ofgenetic change of obliquity as shown in Text-figs.
llA and B, the presumed phylogenetic relationships of 1. (Pl.) japonicus, 1. (Pl.) higoensis andtheir ancestral species are shown in Text-fig. 12.
The specimens HK5931 and HK7257 (Nagao
and Matsumoto, 1940, pl. 5, fig. 2; pI. 6, fig. 3
respectively) from Nakahobetsu, Hokkaido areof both with weak divergent ribs, which would
be presumed a transitional form linking 1. sp.
aff.1. (Pl.) yubarensis to 1. (Pl.) higoensis.
It is evident that 1. (Pl.) japonicus is intimately related to 1. (Pl.) ezoensis whereas 1.
(Pl.) higoensis to I. (PL) yubarensis by way ofI. sp. aff. I. (Pl.) yubarensis and transitional
form of the specimens HK5931 and 7252.
Tables 19 and 20 are very useful to compare
their phylogenetic relationships. The stratigraphic occurrences of these species support
Table 20.

species

K-test for the slopes between a pair of I. (Pl.) japonicus and its allied
species.
A·

A

B

C

D

E

F

6.47

3.24

5.98

2.24

1.89

5.38

0.14

2.51

4.03

4.14

0.11

0.79

2.. 68

2.26

B

0

C

0

0

0

-

0

0

-

0

-

D

E

0

F

-

0.62

0
0

.-

A : I. (Pl.) yubarensis, B: I. (Pl.) sp. aff. I. (Pl.) yubarensis, C: I. (Pl.) ezoensis~ : I .. (Pl.) higoensis, E: I. (Pl.) japonicus hokkaidoensis, F : I. (Pl.) japonicu~

Jap0n/cus.

o : significant, - : not significant.

Explanation of Plate 44
Fig. 1. Inoceramus (Platyceramus) higoensis sp. nov. natural size. JG.H2727, holotype. Loc.
HIl009, a northern shore of Kojima, Himedo-machi, Amakusa-gun, Kumamoto Prefecture.
Lower part of the Middle Formation, Lower Subgroup, Himenoura Group (colI. M. Noda).
Fig. 2. Inoceramus (Pl.) higoensis sp. nov. xO.75, plaster cast of the external mould of the holotype.

769. Inoceramus japonicus

215-----------_L

Text-fig. 12. Diagram showing the phylogeny of I. (PI.) japonicus and its allied species.

1. (PI.) japonicus and the revised species occurs
in the lower part of the Middle Coniacian ofEuramerica as Kauffman (1975, 1976 and 1977)
has stated.
Judging from the precise description of
Seitz (1961),1. (Cladoceramus) undulatoplicatusis closely similar to 1. (PI.) rhomboides Seitz
in shell-form_ There is, furthermore, a form
called 1. (PI.) rhomboides heinei Seitz[= 1. cycloides var. undulata Heine, 1929 (nonMantell)], which is essentially similar to I. (Pl.)
rhomboides rhomboides of Seitz in the shellform and the concentric ornamentation but
has weak divergent ribs_ This is at least morphologically a transitional form between 1.
(Pl.) rhomboides and 1. (CI.) undulatop licatus ,although I would not repeat here my commentson the subspecific classification of Seitz.
According to Seitz (1961, also 1967, p. 144),
1. (PI_) rhomboides rhomboides ranges fromthe Lower Santonian to the Lower Campanian,as 1. (Pl.) cycloides Wegner does . 1. (C L) un-

dulatoplicatus , including subspp. undulatoplicatus michaeli and subsp. indet, are restricted
to the Lower Santonian and I. (Pl.) rhomboides
heinei occurs also in the Lower Santonian.
1. (Pl.) cycloides wegneri Bohm, which is closely
similar to I . (PI.) cycloides cycloides in theshell-form and the concentric ornaments but
has rather weak divergent ribs in more or lesslate growth stages, occurs also in the Lower
Santonian of Germany.
It should be noted that as to the subdivisionof a stage, there is some discrepancy between
Germany and Japan. For example, the Santonianis tripartite into the Lower, the Middle andthe Upper substages in Germany, whereas it isbipartite into the Lower and the Upper inJapan. The Campanian is bipartite in Germany
but tripartite in Japan.
From the resemblance in early ontogeny,
linking by transitional or intermediate forms
and their stratigraphic levels, the above discussed
species are undoubtedly closely related to one

Masayuki NODA

216

another, which have been derived from somecommon ancestral species of 1. (Platyeeramus).
The relationships of the above mentioned
species in Europe are analogous with those of
the species and subspecies in Japan and theparallel evolution is recognized ·between Europe
and Japan with some time lag in the development
of divergent ribs.
This conclusion com firms the opinion of
Matsumoto (in Matsumoto and Haraguchi,
1978, p. 317) which was concisely and preliminarily given in his discussion of biostratigraphy.
Evidently 1. undulatoplieatus should be
assigned to the subgenus Platyeeramus, since
its close ally 1. rhomboides is a typical Platyeeramus. Caldoeeramus is, thus, unnecessary,as has been recently pointed out by Matsumoto
et al. (1982, p. 63).
Conclusion

1. By means of the statistic examination as
well as normal observation, it has been elucidated
that two independent species and two subspecies
are distinguished in the so-called 1. japonicus
Nagao et Matsumoto, i.e. 1. (Pl.) higoensis sp.
nov.,1. (Pl.) japonieus hokkaidoensis subsp. nov.
and 1. (Pl.) japonieus japonieus Nagao et Matsu~
moto, which approximately correspond to forma
0:, ~ and 'Y of Nagao and Matsumoto (1940)
respectively.
2. On all sorts of available evidence discussed
in this paper, 1. (Pl.) japonieus is discriminatedspecifically from 1. (Pl.) undulatoplieatus Romer
which seemingly resembles 1. (Pl.) japonieus
hokkaidoensis in some biometric characters.
3. In a sample of 1. (Pl.) japonieus takenfrom the same bed, some specimens have peculiar
posterior divergent ribs of the "miehaeli type".
They occur together with typical specimens
and linked by intermediate forms. They should
be regarded as a variation within a species orsubspecies.
4. From the resemblance in immature shelland partly overlapping stratigraphic occurrence,
1. (Pl.) japonieus is probably a derivative from
1. (Pl.) ezoensis and 1. (Pl.) higoensis may bedescendant of 1. (Pl.) aff. 1. (Pl.) yubarensis(a specimen JG.H2706) or 1. (Pl.) yubarensis.
On the other hand, 1. (Pl.) undulatoplieatusprobably descended from 1. (Pl.) eycloides
by way of 1. (Pl.) rhomboides. These relationships are an example of parallel evolution withsome time lag in developing divergent ribs.
The development of divergent ribs is a convergence of the two lineages in PIa tyee ramus.
5. Platyeeramus and Cladoeeramus obtained
the validity since Seitz's revision (1961). However, the subgeneric distinction between themis very difficult in view of the presence of linking
intermediate forms and impossible at populationlevel. It is desirable to adopt PIa tyee ramus which
has the page priority over Cladoeeramus.

Acknowledgements
I am deeply indebted to Emeritus Professor
Tatsuro Matsumoto of Kyushu University forhis cordial guidance, useful advice and a criticalreading of the typescript. I wish to thank Dr.
Masayuki Tashiro, Messrs. Kikuo Muramoto
and Takemi Takahashi for their help in thefield works and Dr. Kazushige Tanabe andMessrs. Kikuo Muramoto, Takeshi Kozai, Kenji

Explanation of Plate 45
Fig.1. Inoceramus (Platyceramus) higoensis sp. nov. xO.75. JG.H2720, paratype, plaster cast of
external mould. Loc. HIl009 (coll. M. Noda).
Fig. 2. Inoceramus (Pl.) higoensis sp. nov. xO.75, JG.H2719, paratype. Loc. 1009. Showing an
ornament of the "michaeli type" (coll. M. Tashiro).

769. Inoceramus japonicus

Sanada and Yoshimitsu Haraguchi for theirgenerosity of offering some valuable specimens
for this study. I am also indebted to Prof. Makoto
Kato and Prof. Toshimasa Tanai of Hokkaido
University and Dr. Itaru Hayami of University
Museum of University of Tokyo for their kindness to let me study certain type specimensof Nagao and Matsumoto (1940). I am alsoindebted Messrs. Seiya Kimura and Katsuhiko
Mukunashi of Oita Educational Center for
making program and computer time available
for this study. A part of the financial expenditure was defrayed from the Shimonaka Commemorative Foundation (1978, 1980).
References
Cox. L. R. (1969): Moore, R. C. (ed.) Treatiseon Invertebrate Paleontology (N), Mollusca
6, (1 of 3), p. 314-321, Geol. Soc. Amer.
and Univ. Kansas Press.
Hayami, 1. (1969): Mensuration of fossils andstatistics - an example of palaeontological
exercise - Sci. Repts. Dept. Oeol., Kyushu
Univ., vol. 10, no. 2, p. 67-90 (in Japanesewith English abstract).
--(1975): A systematic survey of the Mesozoic
Bivalvia from Japan. Univ. Mus., Univ.
Tokyo, Bull. 10, p.1-249, pIs. 1-10.
--and Matsukuma, A. (1971): Mensuration offossils and statistics - Analysis of allometry
and variation - Sci. Repts. Dept. Oeol.,
Kyushu Univ., vol. 10, no. 3, p. 135-160(in Japanese with English abstract).
Heine, F. (1929): Die Inoceramen des mittelwestfiilischen Emscher und unteren Untersenons. Abh. Preufl>. Oeol. Landesanst., N.
F., no. 120, 124 pp. 20 pIs.
Heinz, R. (1928): Das Inoceramen-Profil der
Kreide Liineburgs mit Anfiihrung derneuen Formen und deren Kennzeichnung.
Beiriige zur Kenntniss der ober Kretazischen
Inoceramen 1. Jber. Niederaachs. geol.
Ver.• vol. 21, p. 63-81, pI. 2.
--(1932): Aus der Neuen systematik derInoceramen. Mitt. Min. Oeol. Staatsinst.
Hamburg. vol. 13, p. 1-26.
Kanie, Y. (1966): The Cretaceous deposits in
the Urakawa district, Hokkaido. Jour. Oeol.
Soc. Japan, vol. 72, no. 7, p. 315-328 (in217Japanese with English abstract).
Katto, J. (1969): Oeology of Kochi Prefecture.
316 pp., Kochi Municipal Library, Kochi(in Japanese).
Kauffman, E. G. (1975): Dispersal and biostratigraphic potential of Cretaceous benthonicbivalvia in the Western Interior. Oeol. Assn.
Canada, Spec. Paper, no. 13, p. 163-194.
--(1977): Systematic, biostratigraphic andbiogeographic relationships between middle
Cretaceous Euramerican and North PacificInoceramidae. Palaeont. Soc. Japan. Special
Papers, no. 21, p. 169-212.
--(1978): British middle Cretaceous Inoceramid biostratigraphy. Ann. Mus. d 'Hist
Nat. Nice, vol. 4 (for 1976), p. IV 1IV.12.
Matsumoto, T. (1942): Fundamentals in the
Cretaceous stratigraphy of Japan. part 1.
Mem. Fac. Sci., Kyushu Imp. Univ., [Di.
vol. 1, no. 3, p. 129-280, pIs. 5-20.
--(1959): Zonation of the Upper Cretaceous
in Japan. Mem. Fac. Sci., Kyushu Univ.,[D i , vol. 9, no. 2, p. 55-93.
--(1965): A monograph of the Collignoniceratidae from Hokkaido Part 1. (Studyof the Cretaceous ammonites from Hokkaido and Saghalien-XIV). Ibid., vol. 16, no. 1,
p.1-80, pIs. 1-18.
--and Haraguchi, Y. (1978): A new Texanitine
Ammonite from Hokkaido (Study of Cretaceous Ammonites from Hokkaido andSaghalien - XXXIV). Trans. Proc. Palaeont.
Soc. Japan, N. S. no. 110, p. 306-318,
pI. 42.
--and Kanie, Y. (1979): Two ornate ammonites from the Urakawa Cretaceousarea, Hokkaido. Sci. Rept. Yokosuka City
Museum, no. 26, p. 13-20, pI. 5.
- - , Muramoto, T. and Inoma, A. (1972):
Two small desmoceratid ammonites from
Hokkaido (Study of the Cretaceous Ammonites from Hokkaido and SaghalienXXIV). Trans. Proc. Palaeont. Soc.
Japan, N. S. no. 87, p. 377-394, pI. 47.
--and Noda, M. (1968): An interesting speciesof Inoceramus from the Upper Cretaceousof Kyushu. Ibid. no. 71, p. 317~325, pI. 32.
- - , Noda, M. and Kozai, T. (1982): Upper
Cretaceous Inoceramids from the Monobe
area, Shikoku. Palaeont. Soc. Japan, Special
Papers, no. 25, p. 53-68, pl~. 8-11.

Masayuki NODA

218

Nagao, T. and Matsumoto, T. (1940): A monograph of the Cretaceous Inoceramus ofJapan. part II. Jour. Fac. Sci., Hokkaido
Imp. Uniu., [4], vol. 6, no. 1, p. 1-64,
pis. 1-22.
Noda, M. (1975): Succession of Inoceramus in
the Upper Cretaceous of Southwest Japan.
Mem. Fac. Sci., Kyushu Uniu., [D], vol. 23,
no. 2, p. 211-261, pis. 32-37.
--and Matsumoto, T. (1976): Atlas of Japanese fossils, 45, Mesozoic molluscan fossilsof Japan 4, (Cretaceous Inoceramus 1-6)
24 pp. (in Japanese). Tsukiji Shokan, Tokyo.
oSasa, Y. (1932): Geology of Kudi District, Iwate
Prefecture_ Jour. Geol. Soc. Japan, vol. 39,
no. 466, p. 401-430 (in Japanese).
Seitz, O. (1961): Die Inoceramen des Santon von
Nordwestdeutschland. Beih. Geol. Jb., vol.
46, p.1-186, pis. 1-15.
--(1967): Die Inoceramen des Santon und
Untercampan von Nordwestdeutschland.
Ibid., vol. 75, P. 1-171, pis. 1-27.
Sornay, J. (1964): Sur Quelques nouvelles especesd'Inocerames du Senonien de Madagascar.
Ann. PaIeont., vol. 50, no. 2, p. 167-179,
pis. 1':"'3.
Sornay, J. (1969): Especes et sous-especes
Senoniennes nouvelles de la Faune d'Inocerames de Madagascar. Ibid., vol. 55, no. 2,
p. 195-222, pis. A-H.
Stephenson, L. W. (1950): Index fossils withparticular reference to the Upper Cretaceousof Eastern United States. Jour. Geol. Soc.
Japan, vol 56, no. 653, p. 89-94.
Stoliczka, F. (1871): Cretaceous fauna of southern India. Palaeont. Indica, [6], 538 PP.
50 pis. Calcutta.
Tanabe, K. (1972): Stratigraphy of the Cretaceous formation in the Uwajima district,

Ehime Prefecture, Shikoku. Jour. Geol.
Soc. Japan, vol. 78, no. 4, p. 177-190(in Japanese with English abstract).
Tashiro, M. (1976): Bivalve fauna of the Cretaceous Himenoura Group in Kyushu. Palaeont.
Soc. Japan, Special Papers, no. 19, 102 pp.
12 pis.
Ueda, Y. (1962): The type Himenoura Group. Appendices Palaeontological notes. Mem.
Fac. Kyushu Uniu., [D], vol, 12, no. 2,
p. 129-178, pis. 22-27.
- - , Matsumoto, T. and Akatsu, K. (1962):
The Cretaceous deposits in the Chikubetsu
area, Hokkaido. Sci. Repts. Dept. GeoL
Kyushu Uniu., vol. 6, no. 1, p. 15-32 (inJapanese with English abstract).
Vokes, H. E. (1967): Genera of bivalvia - A
systematic and bibliographic catalogue.
Bull. Amer. Paleont. vol. 51, no. 232, p.
105-394.
Woods, H. (1912a): A monograph of the Cretaceous Lam ellibranchia. 2, part 8, Inoceramus.
Palaeontgr. Soc. London, p. 285-340,
pis. 51-54.
--(1912b): The evolution of Inoceramus in
the Cretaceous Period. Quart. Jour. Geol.
Soc., vol. 68, p. 1-10.
Yamaguchi, S. and Matsuno, H. (1963): Sankei.
Explanatory tex t of the geological mapof Japan, scale 1:50000, Asahikawa, no. 34,
Geol. Surv. Japan, 50+9 pp. 1 map (inJapanese with English abstract).
Yamamoto, S. and Hayami, I. (1971): Cretaceous system of Shishijima, Kagoshima Prefecture. Sci. Repts. Dept. Geol., Kyushu
Uniu., vol. 11, no. 1, p. 35-44 (in Japanesewith English abstract).
Young, K. (1963): Upper Cretaceous Ammonites
from the Gulf Coast of United States. The
Uniuersity of Texas Publication, (6304),
142 Pp., 82 pis.

Explanation of Plate 46
Fig. 1-6. Inoceramus (Platyceramus) higoensis sp. nov. all natural size. 1. JG.H2701; 2. JG.H2702;
3. JG.H2708; 4. JG.H2709; 5. JG.H2712 and 6. JG.H2713, paratypes. Loc. H1l023, awestern shore of Kugushima, Ryugatake-machi, Amakusa-gun, Kumamoto Prefecture. Upper
part of the Middle Member, Lower Formation, Lower Subgroup, Himenoura Group (coil. M.
Noda).

769. Inoceramus japonicus

219

Abeshinai 'ti::if;~;r~. Amakusa 7"(1/[. Asahikawa 1t!!1I1. Chikubetsu ~5JrJ. Frenai j1&l*J. Furushiro·
yama J!1~I-Li. Haboro ::fJ$Jt Higashi·machi JRIIIJ. Himedo-machi !<I:iPIIlJ. Himenoura !<I:iil-ll. Hirano:if!llf. Hobetsu f!g5JlJ. Hongo
Horobetsuyama iM\\5JrJl-Li. Ikushumbetsu ~,*5JrJ. Inasato flliIlL
Izumi-gun l±l7JcIl~. Kajisako mfieJ!1. Kami·gun 1!l'~llli. Katsura·zawa ttiR. Kawakami JIIJ:.
Kawauchi i"Jr~. Kikume·zawa *iiIDiR. Kojima 'Nil;. Kugushima ff"lCt;. Kuji·Kudi R~. Kunitan
IBft. Migi-no·sawa ;f5(J)iR. Mikasa ::::::~. Minamioita mx7t. Mojirobana -'E- y
Monobemura fufflltt. Motogama 5C~. Nagashima Rlih. Nakagawa-gun "plllllli. Nakahobetsu *~5JrJ.
Oda Wlm. Omaki-zawa ::k:~iR. Oyubari Xg~. Pankehorokayuparo-zawa /~:/ 7";t: P 11 ='- - /~ P
iR. Panke-sawa /~ :/ 7" tR. Ryugatake-machi fl1 7" flrlIlJ. Sankei ::::::~. Saru-gun r:PVfEllli. Shirahama
B~. Shishijima W-T~. Shitanuki r~. Teshio 7"(J1ri\. Tomamae-gun 2ilitrllli. Tomiuchi ffil*J.
Uto ~±. Urakawa iHii"J. Uwajima ~fn,!1l;. Wakkawen '7:;; 11 =:/. Washinosu :'I(J)!,I!, Yezo~:%, Yubari g~, Yufutsu-gun ~tbllli*Jl!!l.

p..

f3*J:tiIlB!IIi:*J: i)j£'i"7.,t'hkP7., Inoceramus japonicus Nagao et Matsumoto 1:''0
t '-C: r:l *(J) -If" :/ ~ =-- 7 :/1lM'J: tiIll:.!f!jl]&S91:.i!€i" 7., t 'hkP 7., Inoceramus japonicus I:' '0\"-C
fl(:,jlW IVfJe}J(:t (:. 1)0 *- -C. -t.h-1:'.h(J) j£'l1!l(J) {, (J) f:. '0 ~>fiICgt(j9i:.~H L t-:f.t !1'!:. 2 '0 (J)1'ttft L
t-: 1i1! C. -t.h.7C*c(J):fiRiJ; 2 '0(J) E!E~i:.f'Z5JrJ ~.h 7., ~ Ct)~li[~:g ~.h t-:o i"tJ:h i?, I. (Pl.) higoensis sp. noy .• I. (Pl.) higoensis subsp., I. (Pl.) japonicus hokkaidoensis subsp.noy .•I. (Pl.) japonicus japonicus Nagao et Matsumoto '"C, ~.hG(J) 'i i?!lli:fl1!~~~-C I. (Pl.)
higoensis '1 Nagao and Matsumoto (1940) iJ~ forma a C Lt-: {, (J). -t(J){t!!,{1.7dlJc'.hforma (j. r c L t-: {, (J) f:.a 1:t*fI~i" 7., 0 *:WO'"C11@{;$:lW(J)ft;lfiiJ' G:fiR;t t-: It!ffifj{((J) lK5JIJ~ L
t-:j/&§l~jili"'.

-t.h-1:' .h(J)iT-l]&I:' '0\" -C ~cJlil( L, 7Hlijj£'(J)iliW-:fiR c Jt~BC Lt-:o ;t t-:.

>fiIC~t(J)*a*~;f§MIlli:J:t(J)fo'iH)TtJ: G m:.j£'l±l~$-I:'~--)\' '-C -t(J)*>fiIC~~~ Lt-:o ~ G I:'. jjji:J~(J)jfflH.ltI:''0\"-CiiJfUN.L. Cladoceramus c~.h-Ct,t-:{,(J)~ail:~-C Platyceramus c Lt-:o !Ilfm~z

Trans. Proc. Palaeont. Soc. Japan, N. S., No.132, pp. 220-229, pIs. 47-50, December 30, 1983

770. CRETACEOUS NAUTILOIDS FROM HOKKAIDO-iII
PART 3. SOME NAUTILOIDS FROM THE CAMPANIANOF SOYA, NORTHERN HOKKAIDO*TATSURO MATSUMOTO
c/o Department of Geology, Kyushu University 33, Fukuoka 812
and

TOSHIYA MIYAUCHI
Natural History Collection of Northern Hokkaido, Midori-6, Wakkanai 097

Abstract.
This is Part III of a monograph of the Cretaceous Nautiloids from
Hokkaido being published in series. It contains the descriptions of the three species
from the Campanian strata exposed on the northwestern coast of Cape Soya (Textfig. 1). The first is a new species of Eutrephoceras, which is allied to E. kobayashi
Matsumoto and E. pseudobouchardianum (Spengler) but its siphuncle is central
instead of subventral or subdorsal. Its whorl is broader and more inflated thanE. tawaense Furuichi or E. balchistanense (Spengler). The second is a new speciesof Cymatoceras, which resembles C. cenomanense (Schluter) but its suture is not
so sinuous as in that species. The third is a new species of Anglonautilus, which isdistinguished from A. undulatus (Sowerby) in its much weaker ribs and the development of a shallow ventral groove on its body-chamber. The group of strata
in the studied area is subdivided into 8 members, A to G in ascending order, of
which A to D are the Middle Campanian and E to G the Upper Campanian. The
first species occurs in C and D, the second in F and the third probably in C. They
are all of shallow open sea facies.

Introduction

which are being studied by us. This paper gives
a result of our study on the nautiloids.

One of us (T. Miyauchi) has been engaged incollecting the natural history material from
northern Hokkaido to enrich the knowledgeof botany, malacology and palaeontology. The
other of us (T. Matsumoto) was invited to
Wakkanai to cooperate with him in the palaeontological study. There are several nautiloid
specimens among fairly numerous fossils collected from the Cretaceous of the Soya area,

Note on Stratigraphy
Before going into the palaeontological descriptions, we should give a note on the Cretaceous
stratigraphy of the Soya area. Cape Soya, which
now belongs administratively to the easternpart of the City of Wakkanai, consists primarilyof Cretaceous and Tertiary strata, besides small
bodies of basaltic rock and Quaternary terrace* Received October 29, 1982
220

770. Cretaceous Nautiloids
deposits at several levels. As shown in the published geological maps (Osanai et al., 1959;
Matsumoto and Obara, 1971), the Cretaceous
strata are overlain by the Tertiary (Miocene)
Magaribuchi Formation with an unconformityof a considerable time gap. The strata of theCretaceous and the Tertiary are both folded andfaulted, showing generally parallel structures.
The Cretaceous strata exposed on the eastern
coast of Cape Soya range in age from Upper
Albian (?) to Campanian, showing fairly complex
geological structures (Matsumoto and Miyauchi
in Matsumoto, 1982). Those. exposed in thenorthernmost part and the western coastal
area of the cape are mostly referred to theCampanian. They show rather gentle inclinations,but there is repetition or omission of strata by
the faults of N-S and NW-SE trends (Text-fig.
1). The Maastrichtian is lacking in the coastal

221

area but a part of it crops out in the central
hilly area between Koishi and Magaribuchi,
where Tertiary strata occupy a wider area.
The exposures of the strata in the western
coastal area are insufficient on the land side,
but there is a wave cut bench off the coast.
That bench is usually submarine, but at thetime of the lowest tide (twice a year) someparts of the bench are accessible for us to examine the constituting strata and to collectthe contained fossils. There was, furthermore,a reconstruction of the fishery harbour of Soyain 1973, when one of us (T. Miyauchi) had
an opportunity to observe the temporarily
exposed (otherwise submarine) strata at the
excavated place, and we collected fossils fromthe excavated rock masses brought to the coast.
In addition to the large scale excavation
at the Soya harbor, small scale dredgings ofN+
r4ARU-YAr~A

o.

lOOOm

Text-fig. 1. Geological outline map of the northwestern part of Cape Soya.
Cm: Middle Campanian, Cu: Upper Campanian, T: Tertiary, v: basalt e: fossil locality (in situ),+: ditto (floated), 1-6: localities of the Cretaceous nautiloid,.1: Landing place of Rinzo Mamiya.
Inset at the lower right comer the index map.

222

Tatsuro MATSUMOTO and Toshiya MIYAUCHI

submarine rock floor are in operation more
frequently along the coast-line for the passage
of small fishery boats. Fossils can be hunted
from the dredged rock fragments.
Through these procedures of field work,
the biostratigraphical sequence in the northwestern coastal area of Cape Soya has been
made clear as follows in ascending order:
A. Medium- to coarse-grained, cross-bedded sandstone, exposed at the southeastern cornerof Ohmisaki (e.g. near the Primary School).
Sphenoceramus schmidti (Michael) occurs incertain layers.
B. Mudstone, with subordinate sandstone, typically exposed at the head of the cape, characterized by S. schmidti, Gigantocapulus giganteus (Schmidt), Canadoceras kossmati Matsumoto etc., occurring mostly in the contained
clacareous nodules.
C. Silty fine-grained sandstone or fine-sandy
siltstone. In the contained calcareous nodules,
drifted pieces of vegetable matter are accumulated along with some well preserved
molluscan fossils. This unit is called the"Fukiyose Beds" [Fukiyose in Japanesemeans drifted together] in our field workfor convenience' sake. There are at least
four beds which contain such nodules. This
unit constitutes the wave <;ut bench off
the coast· of Kiyohama-I [=Dai-ichi Kiyohama] and also a part of the one off thewestern coast of Kiyohama-II [= Dai-ni
Kiyohama] [= "Orannai"]. The characteristic
species are Canadoceras mysticum Matsumoto,C. sp. nov. (small form), C. multicostatum,
Baculites aff. B. chicoensis Trask, Eutrephoceras soyaense sp. nov. and probably
also Anglonautilus mamiyai sp. nov. (bothdescribed below), among many others S.
schmidti occurs in the lower part of thisunit.
D. Silty fine-grained sandstone to fine-sandy

siltstone, often bioturbated. Some of thecontained nodules are prolific. In addition
to the ammonite species which are common
with those from units Band C, there are
Pseudophyllites sp. Desmophyllites sp. andPachydiscus sp. and probably E. soyaense.
The fossiles from this unit exposed between
Kiyohama-I and Soya are often distorted
because of the deformation along a faultof N-S trend.
E. Green silty fine-grained sandstone withpartly sandy siltstone. It contains a characteristic heteromorph ammonite, Schlueterella
sp. nov. aff. S. pseudoarmata (SchlUter). In
addition, Diplomoceras notable Whiteaves,
Parasolenoceras sp. nov., Baculites inornatus
Meek, Pachydiscus sp. nov. aff. P. neevesiWhiteaves and Canadoceras multicostatum(large form) are here. Metaplaceaticeras
subtilistriatum is found rarely. Also Cymatoceras honmai sp. nov. (to be described below)
is probably from this unit.
The beds of Unit E were recognized below
Unit F during the large scale excavation (in1973) to reconstruct the fishery harbour of
Soya and have traced elsewhere along with F.
F. Dark grey silty sandstone or sandy siltstone
containing rather sporadically remains ofMetaplacenticeras subtilistriatum (Jimbo) andalso very rarely Hoplitoplacenticeras sp. In
addition to the Soya harbour excavation,
this unit is exposed in the coastal belt (partly
off-shore and partly on-land areas) southof the har.bour and also on a shoal about
150 m off the coast of Kiyohama-II.
G. Sandy siltstone with some interbeds or
lentils of sandstone. Fossils are rare, but
for scattered occurrences of Desmophyllites
diphylloides (Forbes), Anapachydiscus (ascicostatus (Yabe), Canadoceras multicostatumand Metaplacenticeras subtilistriatum.
In the published geological map (Osanai

Explanation of Plate 47
Figs. 1, 2.
Eutrephoceras soyaense sp; nov. . . . . . . . . . . . . . . . . . . . . . . . . . . . • Page 223
1. MNH. 8240606 (paratype), ventral (a) and lateral (b) views, xl.
2. MNH. 8240505 (paratype), lateral (a) and frontal (b) views, xl.

Matsumoto and Miyauchi: Cretaceous Nautiloids

Plate 47

770. Cretaceous Nautiloids
et al., 1959), Units A and B are major part of
the Ohmisaki Formation and the rest (including
units C to G altogether) is indicated as theOrannai Formation. Based on the concept ofcycle of sedimentaion, the above subdivided
units should be grouped into two formations;the lower one (the Ohmisaki Formation in arevised sense) which begins from the sandstoneof Unit A and ends at Unit D, and the upperone (the Orannai Formation emend.) consistingof Units E, F and G.
Biostratigraphically, the lower formation is
assigned to the Zone of Sphenoceramus schmidtiCanadoceras kossmati, which represents SubStage
K6a2 on the Japanese scale (Matsumoto 1977
fig. 1; 1978, table 7 in Moullade and' Nairn',1978), approximately Middle Campanian interms of the international scale (indicated as
em in Text-fig. 1). Units E, F and G are to be
assigned to Substage K6a3, approximately Upper
Campanian (Cu in Text-fig. 1). The latter can becalled the Zone of Metaplacenticeras subtilistriatum.
The localities of the described nautiloids ,1 to 6, are indicated in Text-fig. 1. They arereferred to some of the above explained units,
as will be recorded under Occurrence in thepalaeontological descriptions.
Acknowledgments:-We are grateful to Messrs.
Hajime Honma, Kinji Takagawa, Terumasa
Masuda and Toshio Saheki who kindly helped us
in the field work and have provided some of their
obtained specimens to the Collection of MNH for
this study. Thanks are extended to Mr. Akio
Tanabe of Wakkanai who generously supported
our study and Dr. J. A. Jeletzky who kindly
sent us replica of the two type specimens ofWhite aves with necessary information. As in
preceding parts, Dr. Masayuki Noda and Miss
Kazuko Hara continued to help us in preparing
plates of photographs and typescripts.

Palaeontological Descriptions
Class Cephalopoda
Subclass Nautiloidea

223

Order Nautilida
Family Eutrephoceratidae Miller, 1951
To evaluate this family one of us has discussed
at length in Part I (Matsumoto, 1983).
Genus Eutrephoceras Hyatt, 1894
Type species:-Nautilus dekayi Morton, 1834.
Remarks:-For the general account of thisgenus, readers may refer to Miller (1947), Kummel (1956, 1964) and Wiedmann (1960), withwhom we are agreeable in many respects, but
for a point. Namely, in accordance with theestablishment of Kummeloceras Matsumoto
1983, we are inclined to restrict Eutrephocera;to the group of species which have nearly linear
or only slightly sinuous sutures and almost
smooth surface of shell, with finely reticulate
or lattice ornament on a young shell. Eutrephoceras, thus understood, is not the direct
ancestor of the living Nautilus but interpreted asa rather reduced group derived from Cenoceras.
Judging from its rather globose shell-form ,smooth shell-surface and simple septal sutures,
we presume that species of Eutrephoceras wereadapted themselves to certain environmentsof very shallow, wavy sea-waters. A fairly common occurrence of a species of Eutrephocerasin particular beds (Le. the Fukiyose Beds ofUnit C in the preceding chapter) seems to
support this interpretation.
Eutrephoceras soyaense sp. nov.
PI. 47, Figs. 1, 2;PI. 48, Fig. 1

Material:-Holotype, MNH. 148, consisting of
the inner septate whorl (A) and the posterior
portion of the body-chamber (B) from loco 5of Text-fig. 1. Paratypes, MNH. 8240605, MNH.
8240606, MNH. 8232102, MNH. 8232013 andGK. H5932 from loco 3 of Text-fig. 1. Thereis another comparable (with indication cf.)
specimen, MNH. 82032904 from loco 6.
Description:-..JJ'he shell must have beenmoderately large, as suggested by type specimens

224

Tatsuro MATSUMOTO and Toshiya MIYAUCHI

MNH. 148 and 82040606. The holotype and
MNH. 82032103 are somewhat smaller, about
65 mm in diameter at the end of the phragmo.
cone.
The whorl is rounded in cross-5ection, some·what broader than high, being broadest in thelower part. The umbilicus is very narrow on theinternal mould and embedded by callus when
the shell is preserved.
The surface of the shell looks smooth. On
the young shell with diameters below 20 mm,
as represented by MNH. 82032102 and GK.
H5932, fine reticulate ornament is discernible.
Septation is fairly dense, about 10 per half
whorl. The suture-line is nearly linear, without
perceptible ventral lobe (Le., nearly straighton the venter), very broadly arcuate (Le., very
shallowly concave) on the flank, with an in·distinct low saddle near the rounded umbilicalshoulder, showing a short descending line tothe urn bilical margin.
The siphuncle is nearly central, i.e. at about
the midst of the dorso·ventral median-line ofa septum.

Comparison:-E. soyaense is fairly similar
to E. kobayashii Matsumoto (1967, p. 164, pI. 3,
fig. 1, text.figs. 1, 2), from Urakawa (south
central Hokkaido) in having the subrounded
whorl, with B/H somewhat over 1.0, and fairly
frequent septa, but distinguished in its central,instead of subventral, position of the siphuncle
and narrower umbilicus which is filled withcallus.
E. soyaense somewhat resembles E. tawaense
Furuichi (1982, p. 336, pI. 54, figs. 1---4; text.figs.
1-4), from the Upper Campanian of Shikoku,
but the latter has a narrower whorl, with B/Hless than 1.0. The siphuncle position is unknown
in that species. Incidentally, E. tawaense seems
to be very close to and could be identical with
E. balchistanense (Spengler) (1910, p. 139)[= Nautilus sublaevigatus of Noetling, 1897,
p. 69, pI. 19, figs. 1, 2; pI. 20, figs. 1, 2], fromthe Upper Cretaceous of Baluchistan.
With respect to the rouned venter, central
siphuncle and frequent sutures, E. soyaense issimilar to E. sublaevigatum (d'Orbigny, 1850)[= Nautilus laevigatus d'Orbigny, 1840, p. 84,

Measurements (in mm) of Eutrephoceras soyaense:
Specimen

DiameterUmbilicus

HeightBreadth

B/H

MNH. 148A

67.0(1)4.2(.06)

38.0(.57)

43.0(.64)

1.13

70.0

80.0

1.14

42.0(.63)

44.0(.66)

1.05

64.0

67.0

1.05

37.0(.62)

42.5(.71)

1.15

148B
MNH. 8240505

67.0(1)o82040606

GK.

8203210360.0

8203210220.0

o14.0(.70)

15.4(.77)

1.10

35.0

o

22.0(.63)

27.0(.77)

1.22

H5932

Explanation of Plate 48
Fig.1. Eutrephoceras soyaense sp. nov . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 223
Holotype, MNH. 148, lateral (a) and ventral (b) views of the inner whorl, frontal view (c) of
both the inner and the outer whorls, xL
Fig. 2. Cymatoceras honmai sp. nov . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 225
MNH. 144 (holotype), two lateral (a, b) and frontal (c) views, xL

Matsumoto and Miyauchi: Cretaceous Nautiloids

Plate 48

770. Cretaceous Nautiloids

pI. 17, figs. 1-4], from the Albian of Europe,
but the latter has a more inflated whorl, witha larger B/H (e.g. 1.21 in d'Orbigny's illustra·tion). GK. H5932 has nearly the same B/H as
E. sublaevigatum, but it is a poorly preserved
small immature shell.
E. soyaense is likewise similar to E. pseudobouchardianus (Spengler, 1910) [= N. bouchardianus of Stoliczka, 1866, p. 203, pI. 92, figs. 4,
4a, which is the lectotype of E. pseudobouchardianus designated by Matsumoto (1967, p. 167)],
from the Arriyalur Group of India, but thesiphuncle is dorsocentral in the latter.
Occurrence:-The holotype was obtainect by
T. Miyauchi from one of the dredged blocks
on the coast of Kiyohama-II at loco 5 in Textfig. 1. It came probably from Unit D. Most of
the paratypes were obtained by H. Honma and
T. Miyauchi from the wave cut terrace off
the coast of Kiyohama-I at loco 3 of Text-fig. 1.
GK. H5932 was obtained by T. Matsumoto
from the same locality. They came from the"Fukiyose Bed" of Unit C, uppermost part of
the Zone of Sphenoceramus schmidti. A poorly
preserved specimen of E. cf. soyaense wasobtained at Sannai (loc. 6 in Text-fig. 1) in oneof floated nodules. It may have come somewhere
near the boundary of Cm and Cu in Text-fig. 1.
Family Cymatoceratidae Spath, 1927
One of us has given comprehensive remarkson this family in Part II (Matsumoto in Matsumoto and Muramoto, 1983).
Genus Cymatoceras Hyatt, 1884
In addition to C. pacificus Matsumoto et
Muramoto, 1983, we are going to introduce
herein another new species from the Campanianof Hokkaido.
Cymatoceras honmai sp. nov.

PI. 48, Fig. 2;Pl. 49, Figs. 1,2
Material:-Ifwo specimens of different sizes,

225

of which the smaller one, MNH. 144 is theholotype and the larger incomplete one, MNH.
146 is regarded as probably a part of the adultbody-chamber of the same species.
Description:-'llie holotype is wholly septate
and measured as follows (in mm):
D = 50.5, U = 5.6 (11% of D), H = 30.0,
B = 37.0; B/H = 1.23
It is an internal mould, without preserved
test. It probably represents an immature stage.
The whorl is subtrapezoid in section, broader
than high and broadest in the lower part, having
high and nearly vertical umbilical walls, subangular umbilical shoulders, gently convex andconvergent flanks, subrounded ventrolateralshoulders and a broadly arched or nearly flat
venter. The umbilicus is deep and narrow, about
11 per cent of the shell diameter.
The surface of the internal mould looks
smooth.
The siphuncle is dorsad from the center,being situated at the middle of the whorl-height.
The septa are regularly and fairly densely disposed, numbering 19 per whorl. They show avery shallow and broad external lobe, a moderate
sinuosity on the flank with an asymmetric,
shallow lateral lobe, a low saddle at the umbilicalshoulder and an umbilical lobe.
The larger specimen (MNH. 146), about
100 mm in breadth, is unseptate and probably
represents a part of the body-chamber of an
adult shell. It contains frequently septate inner
whorls, which are unfortunately distorted andobliquely cut. The last septum is at about thewhorl.height of 90 mm. The body-chamber
is subquadrate in section, with rather flattened
flanks and a very broad venter. The venter isbroader and more flattened than that of theabove described holotype. The apparent difference may be due to the secondary deformation.
As only the inner layer of the shell is preserved,
the so-called ribs are manifested indistinctly
and rather irregularly. They are dense. Theirbackward curve is broad and shallow.
Comparison:-The holotype resembles oneof the syntypes of Cymatoceras cenomanense

226

Tatsuro MATSUMOTO and Toshiya MIYAUCHI(SchlUter) (1876, p. 168, pI. 45, figs. 1, 2),from the Cenomanian of West Germany, inshell-form, position of siphuncle and septal
density. There is, however, unnegligible difference in the sutural pattern. In that German
specimen the lateral lobe is somewhat deeper
than in ours and in addition there is a saddle
at about the umbilical shoulder. Such a distinct
saddle is lacking in the holotype of the present
species.
Occurrence:-The holotype was obtained by
H. Honma in 1981 from a pile of rock fragments
dredged at loco 2 of Text-fig. 1, off the western
coast-line of Kiyohama-I. It is undeformed
and its rock matrix is greenish dark grey, calcareous fine-sandy siltstone. Presumably it. may
have come from Unit E on the western side of
the compact and coarse sandstone of Unit G
which constitute the wave cut terrace for a long
distance off the western end of Kiyohama-I.
The para type was obtained by one of us(T. Miyauchi) from one of the blocks excavatedfrom the bottom of the reconstructed harbourof Soya at loco 1 in Text-fig. 1. It is certainlyreferable to Unit E (Le. the Subzone of Schlueterella sp. nov.).

species. Two other Lower Cretaceous species
have been regarded by Kummel as belonging
to A nglonautilus, but no species later thanthe Cenomanian has been known.
The species described below is certainlyreferred to the same genus and thus the rangeof the genus is extended upward to the Campanian. One of us (Matsumoto) has noticed apoorly preserved specimen in the late Dr. Shingo
Yehara's Collection (Tenri High School, 1981,
p. 20), from the Upper Aptian of Miyako (?)(Northeast Japan), which may be referable tothis genus. Another new species from the Cenomanian of Hokkaido has been recently describedby Matsumoto and Takahashi (1982).

Genus Anglonautilus Spath, 1927

The last septum is at about 75 mm in diameterand the body-chamber is preserved for about
120° on the right side; its true length probably
exceeds that amount to some extent. The left
side is somewhat broken obliquely, so thata part of the inner whorl is favourably shown.
For some reasons a part of the phragmocone
is distorted for about a half volution (Le. from-180° to -360° preceding to the last half
whorl).
The body-chamber is subrounded-subquadrate

Type species:-Nautilus undulatus J. Sowerby,
1813.
Remarks:-We depend on Kummel (1956,
p. 430), who has given a generic diagnosis on
the basis of his observation of the topotype(Kummel, 1956, pI. 20, figs. 1, 2; text-fig. 1),
from the Aptian of England. A. undulatus canbe said to range up to the Cenomanian, since
the specimens of Sharpe (1853, pI. 5, fig. 4)
and Shimansky (1960) are referred to the same

Anglonautilus mamiyai sp. nov.
Plate 50, Fig. 1

Material:-A single specimen, MNH. 147,
that is the holotype by monotypy. The shelllayer is preserved.
Description:-At the preserved last partthe shell is measured as follows in mm:

D = 95, H = 59(.62), B = ca 33 x 2 = 66(.69);
B/H = 1.12

Explanation of Plate 49
Figs. 1, 2.
Cymatoceras honmai sp. nov. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 225
1. MNH. 144 (holotype), ventral view, xL
2. MNH. 146, ventral (a) and lateral (b) views, xO.7.

770. Cretaceous Nau tiloids
in section, with gently inflated flanks , roundedventrolateral parts and a broad venter with ashallow depression on the middle. It is broader
than high, with B/H = 1.12. On the test of theouter whorl a fine longitudinal elevation is
faintly discernible on the extension of themedian line of the ventral depression. It cannot
be called a keel and is not impressed on theinternal mould. It may not be worth special
consideration for a specific diagnosis.
On the septate whorl there is no ventral
depression. The venter is broadly rounded in
its late part but somewhat more narrowly archedin the next inner whorl. The umbilicus is nearlyclosed and surrounded by a steeply inclinedwall.
On the outer whorl there are low and broad,blunt undulations which are better manifestedon the ventrolateral part. They show a considerably backward sinus on the venter. On
the surface of the outer shell-layer fine growthlines and periodic lirae are discernible.

227

On the surface of the shell of the next inner
whorl, there are fine radial and longitudinal(i.e. spiral) lirae, forming a lattice pattern . The
radial lirae show only very shallow and broad,backward curvature on crossing the venter.
The siphuncle is somewhat dorsad of thecenter, crossing septa at about the middle of
the whorl-height. The septal suture is rather
simple, showing a very shallow and broad external lobe and only a slight sinuosity on theside.
Etymology:-The locality is close to thehistorical landing place, where Rinzo Mamiya
sailed off to Sakhalin in 1808 for a geodetic
work. The species is dedicated to this pioneer
geographer.
Comparison :-The holotype of the present
species is fairly similar to the topotype of Anglonautilus undulatus (Sowerby), from the Lower
Greensand of England, figured by Kummel(1956 , pi. 20, figs. 1,2; text-fig. 26) in the generally subquadrate whorl-section and the presence

Text-fig. 2. Anglonautilus suciensis (Whiteaves).
Replica of the lectotype, supplied to Kyushu University by courtesy of the Geological Survey ofCanada. Lateral (A) and frontal (B) views, x O.8.
(Photos by M. Noda.)

228

Tatsuro MATSUMOTO and Toshiya MIYAUCHI

of low and broad undulations. The undulations
are more distinct and coarser and the sutureshows a more pronounced lateral lobe in thelatter. The former has more convex flanks
than the flattened ones in the latter. The shallow
ventral groove is characteristic of the former.
A. undulatus from the Cenomanian of thenorthern Caucasus, illustrated by Shimansky(1960, p. 244, pI. 3, fig. 1), is much larger andhas less depressed whorl and stronger ribs thanthe holotype of the present species.
A smaller specimen figured by Sharpe (1853,
p. 15, pI. 5, fig. 4a-c) under N. undulatus, fromthe Varians Zone (Cenomanian) of England,
has likewise coarser, more distinct ribs thanours on the ventral part of the body~hamber.
Its whorl is higher than broad than the above
mentioned topotype, but this may be Ii variation.
Anyhow, it has a distinctly more compressed
whorl and more sinuous sutures than the holotype of the present species.
The illustrated syntype of Nautilus suciensis
Whiteaves (1879, p. 97, pI. 11, fig. 1, 1a) (Textfig. 2), from the Campanian Division A [= "Productive Coal Measures"] of Sucia Islands, which
is designated here as the lectotype of that species,
may be better referred to Anglonautilus rather
than to Cymatoceras, because it has on thebody~hamber fold-like ribs which are weakened
toward the umbilicus. Its ribs are more distinct
and more numerous than those of A. undulatus
and still more so than those of the present
species. Its body~hamber has no ventral groove,but otherwise it is fairly similar to A. mamiyai
with respect to the shell-form and the positionof siphuncle.
A specimen described by Whiteaves (1884,
p. 197, pi. 21) as a variety of N. suciensis,
from Skidegate Inlet, British Columbia, is evi-

dently referred to Cymatoceras, and was called
later N. (C.) carlottensis Whiteaves (1900, p. 269).
It is similar to, if not identical with, C. atlas(Whiteaves, 1876). Its body~hamber has aventral groove.
Occurrence:-This interesting specimen was
found by a schoolboy with K. Takagawa in oneof the calcareous nodules at loco 4 of Text-fig. 1
on the sea-shore of Kiyohama-II [= "Orannai"]on the 12th April 1980, and then kindly presented to the MNH Collection. The lithology
of its rock matrix (grey calcareous siltstone)
and the mode of shell preservation, as well asother fossils, suggest its derivation from theupper part of Unit C.
Repositories
GK:

Geological Collections, Kyushu University, Fukuoka.
MNH: Natural History Collection of Northern
Hokkaido, c/o T. Miyauchi, Midori 6Chome, Wakkanai.
The Holotype with a MNH number is tobe transferred to GK.
References Cited(For brevity the references listed in Parts 1 and 2
are not repeated here.)
Matsumoto, T. (1977): Zonal correlation of theUpper Cretaceous in Japan. Palaeont. Soc.
Japan, Spec. Pap., no. 21, p. 63-74.
--(1978): Japan and adjoining areas. In
Moullade, M. and Nairn, A. E. M.: The
phanerozoic Geology of the World II The
Mesozoic, A, chapt, 4, p. 79-144, Elsevier,
Amsterdam.
(1983): Cretaceous natutiloids from Hok-

Explanation of Plate 50
Fig.1. Anglonautilus mamiyai sp. nov . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Page 226
MNH. 147 (holotype), ventral (a), two lateral (b, d) and frontal (c) views, xl.
Photos (Pis. 47-50) by courtesy of Dr. M. Noda.

Matsumoto and Miyauchi: Cretaceous Nautiloids

Plate 50

229

770. Cretaceous Nautiloids
kaido-I. Trans. Proc. Palaeon t. Soc. Japan,
N.S., no. 129, p. 9-25, pIs. 4-9.
- - , and Miyauchi, T. (1982): Appendix in
Matsumoto: Inoceramus and ammonite
donated again to the Kitakyus':lU Museumof Natural History. Bull. Kitakyushu Mus.
Nat. Hist., no. 4, p. 1-9, pIs. 1-2.
- - , and Muramoto, K. (1983): Cretaceous
nautiloids from Hokkaido-II. Trans. Proc.
Palaeont. Soc. Japan, N. S., no. 130, p.
85-95, pIs. 16-20.
- - , and Obara, J. (1971): Relations of Cretaceous and Tertiary strata in the Soya area,
Hokkaido. Sci. Repts., Dept. Geol., Kyushu Univ., vol. 11, no. 1, p. 17-34 (inJapanese with English abstract.)- - , and Takahashi, T. (1982): A new nautiloid
species from the Cretaceous of Hokkaido.
Proc. Japan Acad., vol. 58, ser. B, no. 10,
p.295-298.
Noetling, F. (1897): Fauna of Baluchistan.
Fauna of the Upper Cretaceous (Maestrichtian Beds of the Miri Hills). Palaeont. Indica,Mem. Geol. Surv. India, ser. 16, vol. 1,

pt. 3, p. 1-79, pIs. 1-23.
Osanai, H., Mitani, K. and Kitagawa, Y. (1959):
Soya and Cape Soya. Expl. Text. Geol.
Map, scale 1:50,000, 52 p., map, Geol.
Surv. Hokkaido (in Japanese with English
abstract).
Tenri High School (1981): Catalogue of Fossil
Specimens in the Collection of the late-Dr. Shingo Yehara, p. 1-77 (incl. pIs. 1-9)
(in Japanese), Tenri.
Whiteaves, J. F. (1879): On the fossils of theCretaceous rocks of Vancouver and adjacentislands in the strait of Georgia. Geol. Surv.
Canada, Mesozoic Fossils, vol. 1, pt. 2,
p. 93-190, pIs. 11-20.
--(1884): On the fossils of the coal-bearing
deposits of the Queen Charlotte Islands
collected by Dr. G. M. Dawson in 1878.
Ibid., vol. 1, pt. 3, p. 191-262, pIs. 21-32.
--(1900): On some additional or imperfectly
understood fossils from the Cretaceous
rocks of the Queen Charlotte Islands, witha revised list of the species from these rocks.
Ibid., vol. 1, pt. 4, p. 265-307, pIs. 33-39.

Kiyohama i;1f~, Koishi IJ<fi, Magaribuchi [lhiJI*. Maru-yama 1LW, Ohmisaki ~kl~ljl. Onkoro·
manai :;t:/::z p -< -r 1 , Orannai ~/IiljP"3, Sannai Wi*J. Soya *i:t. Urakawa fjfliUI, Wakkanai
fttft'l~tilih~g[B!!Uc:;tt7A:ll1M-m.

-to) 3 *i:t0):IJ ://{"'-7:/~:;tt7A:ll1M: *i:t~11jlCm) lH:,J:tm (Cu) v:'bt-::5:itl!.~t;;~1±l1":5 0 ~ O):itl!.~t;, f?:;t t7 A :IJ'1 ~{t::fit;;t'=f~1±l Lt.:o ~tL j::)>d:'~llIl L 3 fii>d:'~~.'iJ1j L -C, (1)Eutrephoceras soyaense. (2) Cymatoceras honmai. (3) Anglonautilus mamiyai
frJ15,:i'fi1'!!!c L-Cfjc~Lt.:o (1) 11 E. kobayashii ~ E. pseudobouchardianum I:.W:5t;;, j!l!~k:III'Wt;:Ct'*v:.{ftjgtL. E. tawaense J: t)~.lf!f~O)I~lllt;;!t~,. (2) 11 C. cenomanense t:.{);!,:5t;;.
*j~;sl\lJ!O)i8ini?t;;iJg~"(3) 11 A. undulatus 1:..ltLJ!1Jt;;11:5t.H:'~~<, tt:mO)7i-JID9=t*i:.i~
HIIJ'm't;;j6.l:t1":5 o td,,~:itl!.O)Jl"lJ'f~Tt;'G A-G 0)'ifIllITli:.5Ht, A-D
E-G t;;-ttL.:f
tLPfUft-tj-11!v>d:'~L, tl!<fi1Lt.:*~IIjl~c~MP"3)~H:.~t.:I). 45-kO)lWjf\:11 Cm, Cu-e~:5o(1) 11 c, D, (2) Ii F, (3) lit.:..s;1v C 'ifIl1\"I~-e~:5o ~'ftLt7i-~v:.JIDLt.:VtifiHf].!:';I,dJ:~ tL :5 0
t'~* i1!ft~ • '8 i*J fijkijt0)~tg§iflJ.i'iHt!lTIHU1,"j] ://{"'-70:/cptm (f;(~ 1 BlccTrans. Proc. Palaeont. Soc. Japan, N. S., No. 132, pp. 230-252, December 30, 1983

771. PAL YNOLOGICAL STUDY OF 200-METER CORE
SAMPLES FROM LAKE BIWA, CENTRAL JAPAN
I: THE PALAEOVEGETATIONAL AND PALAEOCLIMATIC
CHANGES DURING THE LAST 600,000 YEARS*NORIO FUJI
Department of Earth Science, Faculty of Education,
Kanazawa University, Kanazawa 920

Abstract. The samples of a 200-meter core obtained from the present bottom
in Lake Biwa, Central Japan for the investigations of the palaeoclimatic and palaeovegetational changes in and around the lake during the last 600,000 years can bedivided into 19 pollen zones from the view point of palynology_ The palaeoclimaticchange and the ages of glacial and interglacial stages display similarity to the palaeotemperature curve by oxygen isotope ratio determination from the Caribbean Sea.
During the glacial stages or stadials, the typical vegetation thriving today in the
Subpolar or Subalpine zone of Japan prevailed at the summit area and/or themontane area around Lake Biwa, and in the lowland around the lake, plants growing today in the Cool Temperate zone were distributed. In the interglacials andinterstadials, the palaeovegetation in the higher area was characterized mainly byplants of the Cool Temperate zone and the present Temperate zone, and in thelowland, the palaeovegetation was composed mainly of broadleaved deciduousand evergreen trees growing in the Warm Temperate zone.

Introduction

Alps. Almost the whole area between the southern border of the inland ice and the Alps waspoor of forest; it was covered only with tundraor cold steppe vegetation.
In the Japanese Islands, however, crustal
movements, volcanic activity, weathering, anderosion have dominated during this period.
The Islands were not affected by an ice sheet
or piedmont glaciers; there were only somesmall glaciers in a few high mountain areas suchas the Japan Alps and Hidaka Mountain Chain.
It therefore is difficult to depend on glacial
geology and topography or palaeopedology to
study the history of glaciation in this area.
The detailed chronology of stadials and interstadials during the last glacial age is complex.
So are correlations with earlier glaciations in

The existence and character of several Quaternary glaciations are documented by the glacial
geology, topography, palaeoclimatology, andpalaeopedology in many countries. In Europe,
during the cold part of the last glacial age (Dreimanis et al., 1972), some 15,000 to 20,000 years
before the present, an inland ice sheet covered
the nothern part of the continent, and bothmountain and piedmont glaciers covered the*Received October 29, 1982; Read June 18,
1977 at the 119th Meeting of the Society at
Shizuoka University; Contribution from the
Department of Earth Science, Faculty of
Education, Kanazawa University; New SeriesNo. 103.
230

771. Palynology in Last 600,000 years, Lake Biwa

Europe and North America. Therefore, if we
do not want to lose ourselves in a terminology
based on inaccurate correlations, it seems necessary to establish a stratigraphic nomenclature
which is not primarily based on meager andinaccurate evidences in mountainous regions,but rather on sedimentary sequences in basins
outside the glaciated regions. Extensive deposits
from glacial and interglacial times can be studied
in deep bore holes. Pollen analysis of the stratigraphic sequences in minute details during thelast two million years can reveal a continuousrecord of the change of vegetation and climate
in the non-glaciated area
With this objective in mind, a project was
proposed to study 200-m core sediments from
Lake Biwa obtained in 1971 (Horie et al., 1974).
As a member of a research team the writer has
been engaged in an intensive investigation of
the palaeolimnological evidence of the subsurface
deposits of the lake.
In this paper, a palynological record of thecontinuous 200-m core sediments, spanningthe last about 600,000 years from Lake Biwa
is presented, along with the vegetational andclimatic interpretations of this record. A moredetailed record from the core and the interpretation will be presented in the near future.
Acknowledgments
The palynological investigation reported herein was carried out during a stay (1975 to 1976)
at the Limnological Research Center of the
University of Minnesota, Minneapolis, Minnesota,
the United States of America. I am greatly
indebted to Prof. Herbert E. Wright Jr. of the
Limnological Research Center for his kind advice
and the helpful criticism of the manuscript. I
am indeed grateful for the support and encouragement of Dr. Shoji Horie of the Instituteof Palaeolimnology and Palaeoenvironment on
Lake Biwa, Kyoto University and Dr. Teiichi
Kobayashi, Prof. Emeritus of the Universityof Tokyo during this investigation. I wish to
express my acknowledgment to Prof. Edward
J. Cushing of the Department of Ecology,

231

University of Minnesota, to Prof. W. A. Wattsof the Botany Department, Trinity College,
Dublin in Ireland, to Dr. C. R. Janssen of
the Laboratory of Palaeobotany and Palynology,
Utrecht, Netherlands, and to Dr. Hsin-Yi Lingof the Department of Geology, University ofNorth lliinois for their useful discussion. I also
acknowledge the help of Miss Kazuko Kanedaof the Kanazawa University. My investigation
made possible through a Scientific Grant from
the Ministry of Education, Japanese Government
for ten years (1971 to 1980) and a help of the
University of Minnesota, U.S.A.
Significance of research on deposits
from Lake Biwa
Palaeomagnetic stratigraphy has provided ameans of correlating continents and oceansover the world. With the advent of deep-sea
research by DV Glomar Challenger and otheroceanographic vessels, oceanographers and geologists have verified the probable existence ofcontinental drift through work conducted on
an international scale and thus established a
new field of plate tectonics and neotectonics.
Recent studies of sediments in deep-sea cores(Hays et al., 1969) and of loess deposits from
central Europe (Kukla, 1970) indicate successive changes of palaeoclimate during the
Quaternary period.
Our understanding of climatic change during
the Quaternary period are based primarily on
research on terrestrial and submarine deposits.
However, the Quaternary system exposed onland is frequently represented by coarse-grainedmaterials such as sand and gravel. This is trueof Pleistocene deposits from the Japanese Islands
but also in deposits from Europe. The pollen
record, unfortunately, is not continuous innorthern Europe, because, especially in thelate and middle Pleistocene, deposits suitablefor pollen preserVation, like peat and clay, wereprincipally formed during the interglacials andinterstadials. Deposits from glacial times are
not preserved even in areas located between
the ice sheets. Coarse-grained materials such as

232

Norio FUJI

sand and gravel are not suitable for pollen
analysis. Furthermore, if the change of sea levelis explained by glacial~ustatic theory, sea levelshould have been lower during the cold glacialand stadial times. Therefore, it is difficult tocollect continuous samples in the Quaternary
period, which is characterized by an alternationof warm and cold climatic times.
On the other hand, although sediments ofboth the cold and warm periods are completein the deep-sea cores, we cannot evaluate changes
in climate over short periods because of theextremely slow sedimentation rate.
On the basis of the above·mentioned con·siderations, the following conditions have to besatisfied if climatic changes can be investigatedby means of palynological, geochemical andpalaeomagnetic analyses:
a: the rate of sedimentation must be large,
b: the sediments must be entirely fine-grainedmaterials, such as silt, clay, or gyttja, andc: the sediments must be continuous since theearly Pleistocene.
According to a few glacial.geological fieldworks (Minato, 1972; Kobayashi, 1958; and Hori·e, 1961 etc.), several expansions of glaciers probably occurred in the Japanese Islands during
the Wisconsin glacial age, those fluctuations
being closely similar to the oscillation of theice sheets in both Europe and North America.
Late·Pleistocene climatic changes were probably
synchronous throughout the Northern Hemi·
sphere. In unglaciated areas, the bottom sedi·ments of ancient lakes may cover the whole
Pleistocene. Lake Biwa in Central Japan is sucha lake (Horie, 1961 & 1962). The exact thicknessof bottom deposits in the center of the lake is
not known yet, but geological evidence indicatesthat the lake was formed in the latest Pliocene
or earliest Pleistocene and has been in existence
continuously. Furthermore, Lake Biwa is thethird oldest lake in the world, after Lake Baikal
and the Caspian and Aral Seas.
In addition, Lake Biwa is important for thefollowing reasons:a) A strikingly negative gravity anomaly exists
in the northern part of Lake Biwa, amounting
to -55 milligal. Isoanomaly lines almost coincidewith the outline of coastal line of this lake
(Tsuboi et al., 1954; Abe et al., 1974). Suchgravity anomaly suggests us the existence of
extremely thick (ca. 1,000 m class) lacustrine
sediments.
b) A great number of endemic species ofanimals and plants is known in the lake. They
differ markably from the biota of other partsof Japan.
c) Judging from the previous geologicalstudies (Ikebe, 1933; Takaya, 1963; Hayashi,1974), the Pliocene·Pleistocene and PleistoceneHolocene boundaries exist in lake sedimentsthat are preserved as the lacustrine terraces.
This fact affords us the evidence of an ancient
Lake Biwa that appeared in sometime during
the Neogene.
A deep boring in such a lake having an ex·tremely long limnetic history must yield valuable
samples for palynological research. These samples
contain a continuous record of the change inclimate since the latest Pliocene or earliest
Pleistocene. These results may be correlatedwith changes in climate during the Quarternary
period already worked out in North America(Dreimanis et al., 1972) and Europe. From
those viewpoints it may be said that the longcore is significant for the promotion of ourknowledge in the Quaternary geology not onlyin the Japanese Islands but also in the othercountries of the globe.
Topography
Lake Biwa, the largest lake in the JapaneseIslands, is located northeast of Kyoto, Central
Japan (approximately 35'1.3'10" N. Lat. and136'1.'28" E. Long.). As shown in the topographic map (Text.fig. 1), a lowland around
Lake Biwa is named the ami Basin. Wakasa
and Ise Bays are located respectively in thenorthwest and southeast of the basin. The
lake is situated just on the isthmus that seems
to be the distorted portion of two arcs com·prising Honshu Island.
The Nosaka Mountains (500-1,000 m) occur
on the border between Fukui and Shiga prefectures of the north of this basin, the Ibuki

771. Palynology in Last 600,000 years, Lake Biwa
Mountains (500-1,300 m) on the border be·
twee'n Gifu and Shiga prefectures, the Suzuka
Mountains (500-1,200 m) on the prefecturalborders between Shiga and Mie or Gifu prefec·tures of the east of the basin, and Hira Mountains(500-1,200 m) and Mizuguchi Hills to the west
and south of the lake.
Although the distance between the above·
mentioned mountain areas and the lake is very
short (5-20 km), the difference of height
between mountain and the lake is large (5001,200 m). Rivers· flowing into the lake, therefore, generally are fast.
An important topographical character aroundthe lake is an existence of graben structure. In

Japan Slla233

both the eastern and western sides of the lake,
there are active faults with north-south trend(the Suzuka trend of Huzita, 1962).
ClimateMost of the Omi region under discussion isthe central part of the Temperate zone, andthe weather is controlled mainly by topography
characterized by the large lake and the northtrending. mountains. In general, the weatherof the northern half corresponds to that of
the Hokuriku region, while the southern partto that of the Kinki region. At Otsu the meanannual temperature is about 14°C.

reoianWANAS. BAY

o -"'----'---"'.3.0 km;."..

~-'-'---35'N

~
~

plain

~ mi. area

I.e Ionic IInl

Pacific Ocean

Text-fig. 1. Topographic map of the Lake Biwa area, Central Japan.
1: Mt. Hira, 2: Mt. Hiei, 3: Mt. Gozaisho, 4: Mt. Fujihara-dake, 5: Mt. Ibuki, 6: Mt. Mikuni-ga-dake,
7: Mt. Mikuni-dake, I: Kaburaki tectonic line, IT: Yanagase tectonic line, ITI: Suzuka tectonic line,
IV: Hira tectonic line, x: boring locality_234

NorioFUJI

The weather system in summer is more orless controlled by the Bonin high atmosphericpressure. The mean July temperature of thearea increases to about 24°C, and the precipitation decrease to about 150 mm. In spite oflittle precipitation the Omi basin is relatively
humid because of higher evaporation rate fromthe large lake in itB center. During this season
a southerly wind prevails.
During the winter the weather is dominatedby the Siberian high pressure. The average
January temperature is about 2°C, and the precipitation in the same month is about 300 mm.
Strong humid northwesterly or westerly ~inds
prevail in the area, and snowfall is abundantin the northern part and mountainous areas.
Frost occurs first in early November. Thereare 200 non-frost days and 1,900 hours ofsunshine per year. The basin is hidden in a mist
for about 60 days as the result of much evaporation from the lake.
Vegetation
The vegetation around the lake is complicated,and due partly to the above climatic condition,and partly to the filet that the lake located near
Kyoto, which was a capital of .Japan for about
1,100 years, for a long time man has exacted
a heavy toll on the natural vegetation by clearing
forestB for farming, by lumbering for ship-building, by cutting wood for charcoal, and by using
timber for domestic purposes. The reconstruction of the vegtation around the lake, as in manyother areas in the Japanese Islands and in othercountries, poses serious difficulties. The original
vegetation has been destroyed throughout thesurroundings of Lake Biwa.
The vegetation around the lake belongs to
the flora of the central part of the Temperatezone and is located near the northern limit of
Citrus (orange) in the Japanese Islands. The
vegetation is divided into two types, namely .
Querco-Fagetea crenatae and Camellietea japonicae types (Kobayashi etal., 1974).
1) Querco-Fagetea crenatae region
The Querco-Fagetea crenatae region occurs

around Mt. Hira and in the Ibuki and Suzuka
Mountains. The flora of this type is found in areas
higher than about 300 m above the sea levelin the northern part and higher than 700 m inthe southern part of this region.
In the neighborhood of the lake, this type isdivided into eight natural communities. They are:Lindero umbellatae-Fagetum crenatae, QuercoClethretum barbinerois, Scrophulario-Aceretum
shirasawae, Rumohreto-Eupteletum polyandrae,
Zelkova serrata, Enkianthus cemuus forma
rubens, Fagus crenata-Cryptomeria japoniea
and Hosta montana communities. Among them,
Lindero umbellatae-Fagetum crenatae is distributed at about 800 m in the Ibuki Mountains,and Zelkova serrata community occurs along
a valley, with Quercus acutissimo serratae belonging to Camellietea japonieae region in thenorthern part of this region. Fagus crenataCryptomeria japonica community occurs aroundthe summit area of Mt. Hira. The distributionof the other communities and assemblages isconfined to local area in the region. Although
Cryptomeria japoniea does not mix with Fagus
crenata, the former mixes with Quercus cripula
or Castanea crenata. The Lindero umbellataeFagetum crenatae is scattered in the Cryptomeria
japonica forest. A bies {irma-Illicium regiosum
community occurs on a very small scale together
with Larix leptolepis about 750 m high on
Mt. Hiei.
A SUbstitutional vegetation of the QuercoFagetea crenatae region is divided into Fagus
crenata-Quercus mongolica var. grosseserrata
community, Castaneto-Quercetum crispulae, Cryptomeria japonica-Chamaecyparis obtusa plantation, Sasa and Miscanthus sinensis communities
in the Omi region. The Fagus crenata-Quercus
mongolica var. grosseserrata community is
substitutional vegetation of Fagus crenata
forest. Around 700-800 m high in the Nosaka,Hira, Ibuki and Suzuka Mountains, the Quercus
crispula, Fagus japonica, Acer japonieum, andA. ru{ineroe are distributed as high trees, Parabezoin trilobum of the above-mentioned community grows remarkably as scrub or small
tree. Castaneto-Quercetum cripulae is distributed

771. Palynology in Last 600,000 years, Lake Biwa

wide between Fagus crenata-Quercus mongolica
var. grosseserrata community area and Quercetum
acutissima-serratae area belonging to Camellietea
japonicae region. A distributional lower limit of
the Castaneto-Quercetum crispulae is distributed
about 600 m above the sea level at the southernpart of this region, and about 300 m at thenorthern part. Sasa or Miscanthus sinensis community scatters at the summit areas and ridges
reaching to 1,000 m or more in altitude.
2) Camellietea japonicae region
The Camellietea japonicae region covers awide area in the Omi basin. However, naturalvegetation belonging to this type occupies verysmall areas. In this region, the natural forestof broadleaved evergreen trees is as follows:
Quercus glauca, Quercus myrstona-efolia, Bladhio-8hiietum cuspidatae, Aucuba japonica var.
borealis-Quercus stenophylla communities.
On the other hand, Alnus japonica andSalix scrub are found on a small scale along
the lakeside or riverside in the northern partof this region.
A SUbstitutional vegetation of the Camellietea
japonicae region is divided into thirteen communities or assemblages as follows: Quercetum
acutissimo-serratae, Rhododendron-Pinetum azumanus, Rhododendron-Pinetum kinkianum, Sasabamboo, Bamboo stand, Miscanthus sinensis,
Phragmites communities, Salix scrub in riverside,
Thea sines is garden, Mornus garden, Paddy-field
weed communities and Pinus thunbergii plantation. Among them, the Pinus densiflora forest
occupies very wide areas. The forest is divided
into Rhododendron-Pinetum azumanum andRhododendron-Pinetum kinkianum. The latterassemblage is distributed in the southern part,and the former in the northern part. Roughly
speaking, in the northern part of this region
the Quercetum acutissimo-serratae is distributed
wider and higher than the distributional areaof the Pinus densiflora forest. This assemblage,
however, is dotted with the Pinus forest in thesouthern part.
The true natural vegetation is very sparsearound Lake Biwa, and most of it is found in
the Querco-Fagetea crenatae region. The original235

vegetation is almost never found in the Camellietea japonicae region except forests composedof a several broadleaved evergreen trees aroundsome shrines and temples and the Zelkova
serrata community in the northern part.
In this region, the snow line and forest line
are about 4,300 m and 2,300-2,600 m above
the present sea level respectively (Minato et al.,1958).
Geology
Palaeolimnology is Pleistocene stratigraphy
applied to lakes (Deevey, 1955), that is, it islacustrine biogeography with a discussion of
the problems of such ancient lakes as Lake
Biwa. The writer will discuss at first the discontinuous distribution of biota in the lake
sediments around the lake.
Judging from many stratigraphic and palaeontologie observations on ancient deposits
around the lake (Ikebe, 1933, and Ishida
et al., 1969), it is presumed that the lake appeared in the latest Pliocene and has continued
its existence ever since.
The Quaternary system in and around Lake
Biwa has been roughly divided into the following
three groups (Yokoyama et al., 1974);
1) Plio-Pleistocene Kobiwako Group
This group occupies the Omi and Iga basins.
It is 1,000 to 1,500 m in total thickness and isdivided into six formations which are composedof lacustrine and fluvial deposits and yieldmany lacustrine fossil molluscs similar to thoseliving in the present lake. Some mammal fossils
such as Stegodon orientalis and Elephas shigensis
are found in the Pleistocene deposits. The radiometric ages of 3.0 to 0.35 million years fromminerals contained in the volcanic ash·layersof this group were obtained by means of thefission·track (Nishimura and Yokoyama, 1975).
The absolute age of the basal part of this groupis estimated to be 4.5 to 5.0 million years before
the present.
2) Middle to Late Pleistocene Terrace Deposits
These deposits consist mainly of a single
gravel layer. Fossil remains are scanty except

Norio FUJI

236

BB42S Ka
1iB4.i3___-_K_-_rdb. 1610<K;)(47)O<Ki(46 OBi (70)

:;:;
os

100

A~

• (Az) (87). db. 365

.!!!>
.c
UJ

200

o Mr (210)o Kn3 (220)o Kn2 (235)
r..;

300

400

E

o Sa

UJ

OM, (310)

os
>0
os

(290)

(

)

:

Year B.P. in 1O'(Fission·track).0 : main volcanic ash
Ka
Ki
Bi
Az
Mr
Kn3
Kn2
Sa
M,

: Kamiogi: Koromogawa: Biotite: Azuki: Murasaki: Konolll: Kono I: Sagami: Magata

down-warping accompanied by faulting. The con·nection between the lake and Japan Sea or Osaka
Bay at that time may have been possible, forthe peneplain was fonned near sea level. The
existence of such connection is supported by
the occurrence of land-locked marine fishes
and molluscs in the lake (Kuroda, 1948). Since
then, the lake basin has continuously occupied
an environment isolated by the surrounding
barriers for more than two million years without
any serious geological disturbance.
Tectonic lines stated already show recent
activity and indicate that the crustal movement
has continued during the Quaternary. The Omi,
Iga, Kyoto, and Nara basins near the lake were
fonned along the Suzuka trend. These tectonic
lines are very important in a discussion of theorigin and the geological structures in and aroundthe lake.
The center of downwarping of the Lake
Biwa basin almost coincides with the centerof the gravity anomaly. There is an argument
among geophysicists whether such a peculiar
gravity anomaly is caused mainly by the special
structure of the earth's crust or mainly by thicklacustrine sediments, but if the latter is correct,
we can expect the existence of extremely thicksediments, resulting from continuous sinkingof the lake basin. This inference is supportedby the geological evidence of a few recent long
drilled cores in the eastern area of the Omi basin.

500

Text-fig. 2. Chronological correlation among the Quaternary deposits in and around
Lake Biwa.

in a few localities. The thickness of these de·posits is less than 20 m.
3) Holocene Deposits
These deposits are mostly fan and/or deltaic
sediments deposited by the present rivers, andcomposed of sandy beds mixed with some clay
and gravel. The thickness of these deposits isabout 10m.
Geomorphologically the base of the Lake
Biwa basin has been regarded as the Neogene(?Miocene) peneplain which was subsided by

Palynological investigation(a) Location of the Boring
A 200-m core used for the writer's investi·
gation was collected from Lake Biwa in the water
depth of 65 m at a location between the Olanoshima Island and Omi-maiko in Shiga Prefecture,
during the autumn of 1971.
(b) Description of Core Samples
About one and half months after recovery,
the long core was cut at 1 m length, and samples
were taken at intervals of about 5 m for primary
analyses. The core was then frozen and cut
longitudinally. Samples used for geochemical
analyses, palaeomagnetic, palaeontologic, mineralogical, granulometric, and radiometric dating

771. Palynology in Last 600,000 years, Lake Biwa
analyses were taken always from a half of thecore keep under frozen state. The other halfof the core was divided for observation oflithofacies and volcanic ashes under the normal
state after melting.
The core sediments mainly consist of soft
homogeneous clay including at least 30 thin
volcanic ash layers. The clay is generally bluein color when it is fresh, though it is grey or
black at several horizons. The balck clay contains
some plant fragments (Yokoyama et al., 1974,1975). Almost all grains of sediments are
smaller than 44 microns in diameter, except
either large plant fragments or volcanic materials.
No sedimentary structure can be observedby the naked eye.
The volcanic materials in the core samples are
divided into two types, andesitic and trachytic.
The former contains two pyroxenes, hornblende, and abundant volcanic glass. The latteris chiefly composed of orthorhombic pyroxene,
hornblende, biotite, quartz, volcanic glass flakes,
and small pumice grains and were derived from
Quaternary volcanoes such as Dai-sen, Sanbe·
yam a, Ohe-takayama, etc., which occur 100350 km west of Lake Biwa (Yokoyama, 1973).
About 50 smaples taken at intervals of about
5 m throughout the core were analyzed forpalynological investigation.
The samples taken from the same horizons
have been analyzed for chemical components,
palaeomagnetism, particle size, clay mineralogy,
and microfossils.
(c) Preparation for Pollen Analyses
Pollen grains in the sediments were concentrated with slight modifications (Fuji, 1963,
1965, 1973, 1974, 1975, 1976) of the method
described by Faegri and Iversen (1964). Sedi·
ments containing coarse organic materials as
moss, small leaves, and small shells were strained
through a fine screen. As most sediments werepredominantly silt and clay, they were left
for 2 hours in hydrofluoric acid to remove thesiliceous minerals. They were treated by standard
acetolysis method. Pollen grains from most
samples were stained with safranin, and were
mounted in glycerine jelly. Throughout the237

present investigation one slide (size of covering
glass area: 24 x 24 mm) was generally enoughto obtain a pollen count of about 500.
(d) Method for Interpretation of Palaeovegetation and Climatic History
The writer depends upon pollen analyses
for reconstructing a vegetation during a geological age. For the interpretation of pollen
spectra obtained from the 200-m core sample
the writer used two ways as (1) pollen spectraof the modem samples taken in and around
Lake Biwa and from various localities of someclimatic zones throughout the Japanese Islands(Wright et al., 1967), and (2) the warmth index(month-degrees) (Fuji, 1965). According to
the law of total effective temperature, thedistribution of a plant is influenced more withthe sum of mean day or month temperature thanwith the mean annual temperature. The total
temperature is given by the formula:(em - p), where
em: mean month temperature
p: physiological zero point, which is shown
generally to be by 5°C in the JapaneseIslands
In the formula, if em is smaller than p, (em - p)value is omitted from this formula.
The total temperature is generally called the"warmth index" (Kira et al., 1958).
The relationship among the warmth index(month-degrees), major plants growing in theJapanese Islands, latitude, temperature andclimatic zones is summarized. On the basis of
the distribution of the warmth index of every
plant, all of the arboreal genera found fromthe samples can be grouped into one of thefollowing five groups: the Subpolar or Subalpine
zone (warmth index month-degrees: 15°-55°),
the Cool Temperate zone (45°-90°): the Cool
Temperate zone - Temperate zone (55°-140°);the middle part of the Cool Temperate zone Warm Temperate zone (70°-140°); and thesouthern part of the Temperate zone - theSubtropical zone (100°-180°).
(e) Construction of the Diagrams
Shown from the left to the right in pollen
diagrams are sediment stratigraphy, lithofacies

238

Norio FUJI

and depth of the core, spectrum number, C14
and fission-track dates, palaeomagnetic stratigraphy, summary diagram, pollen profiles of eachtaxon and assemblage zone. The pollen sum
used on the pollen types concerned, on the local
situation, and on the kind of deposit. The mainpollen diagram is divided into two parts. The
pollen diagram (2) shows all non-arboreal pollen(herbs), aquatic and marsh plants, and ferns,
excluded from the pollen sum but calculated asa percentage over the pollen sum. Percentages
in both diagrams are shown on two scales; thescale with 10 x exaggeration permits the accurateplotting of minor curves and minor fluctuatfons.
The summary diagram is drawn to facilitate
the discussion and interpretation of palaeovegetation and climatic history. This summary
diagram is composed of changes of the ratio
between total AP and total NAP, and of percentages of the Subpolar plants, Cool Temperate
plants, Cool Temperate - Temperate plants,
plants of the middle area of the Cool Temperatezone and of the Warm Temperate zone, andplants of the southern area of Temperate zone
and of the Subtropical zone, calculated on thebasis of the warmth index (month-degrees)as will be described in a later chapter. Therefollow the curves for boreal conifers.
(f) Remarks on Identification of Pollen
GrainsMost of pollen grains from the core samples
are found in the present Japanese Islands, andtheir descriptions can be found in the publishedreferences.
Some of the critical genera are discussed
below.
1) Abies: In the Japanese Islands, six species
belong to Abies. A. Mariesii, A. Veichii, A.
sachalinesis, and A. sachalinesis var. mayriana
grow in the Subpolar or Subalpine zone. Abies
homolepis and A. firma grow in the Cool Temperate and Temperate zones. Pollen grains oflatter two species, however, are not distinguishedfrom other species of Abies from the view pointof the shape of pollen grains.
2) Picea: Six species of Pice a are found in
the Islands. Although Picea is not classified

into species on the basis of pollen morphology,
P. jezoensis and P. jezoensis var. hondoensis, P.
glehnii, P. bicolor var. reflex, andP. bicolor growin the Subpolar of Subalpine zone, and Picea
polita is found in the Cool Temperate zone
(Yamazaki,1951).
3) Pinus: Genus Pinus includes about six
spcies. Pinus pumila and P. pentaphylla arefound in the Subpolar or Subalpine zone, P.
koraiensis grows in the Cool Temperate andSubpolar or Subalpine zones, and P. densifora,
P. himekomatsu, and P. thunbergii grow in
the Temperate and Warm Temperate zones.
Pinus, however, is divided easily into two types
by the pollen morphology: They are P. haploxylon-type and P. diploxylon-type. Species
with five leaves belong to the former; they growin the Subpolar or Subalpine zone at the present.
The latter includes species with two leaves,such as P. densiflora, P. himekomatsu, andP. thunbergii.
4) Taxodiaceae: For genera belonging to
Taxodiaceae, Cryptomeria and Taxodium growin the Japanese Islands after the early Pleistocene. However, in the surroundings of Lake
Biwa, the Plio-Pleistocene Kobiwako Group is
distributed widely and yields pollen grains ofMetasequoia and Glyptostrobus. Accordingly,
these pollen grains are found sometimes as
secondary (reworked) fossils in younger deposits.
Pollen grains of Metasequoia and Cryptomeria
are discriminated from other genera by grain
size and shape of papilla. According to themeasurement of modern species (Fuji, 1973),
Metasequoia: 20 x 23 microns in width andlength; Cryptomeria japonica: 30-33 x 34-38
microns; Sequoia sempervirens: 36-42 x 34-38
microns; Glyptostrobus pensilis: 26-28 x 30 33 microns; Taxodium distichum: 22-25 x 2529 microns. The secondary pollen grains are notshown on the pollen diagram.
5) Tsuga: In the present-day Japanese Islands,
Tsuga diversifolia is found in the Subalpine or
Subpolar zone and T. sieboldii in the Cool
Temperate zone and in the northern part ofTemperate zone. They are not differentiatedfrom other species.

771. Palynology in Last 600,000 years, Lake Biwa
6) Betula: Species such as Betula ermani isfound in the Subpolar or Subalpine zone, andB. platyphylla in the Cool Temperate zone. Theirpollen grains are not differentiated.
7) Fagus: In the present-day Japanese Islands,
Fagus has two species,F. crenata and F. japonica.
According to the wirter's observations: Fagus
crenata measures 38-40 x 45-48 microns andcan thus be distinguished from F. japonica whichmeasures 29-32 x 33 microns. F. crenata grows
in the Cool Temperate zone, and F. japonica isfound in the middle part of the Cool Temperate
and Temperate zones (Fuji, 1976; Fuji et al.,1975).
8) Quercus: Quercus is divided into two
subgenera, Lepidobalanus and Cyclobalanopsis,by its grain~ize and morphology. An evergreen
Quercus belongs to the latter, and deciduous
Quercus to the former. Pollen grains of Cyclobalanopsis can be distinguished from those of
the Lepidobalanus by a combination of features(Shimakura, 1973). As shown below, grains of
Cyclobalanopsis are in general smaller than thoseof Lepidobalanus. The thickness of the pollen
grain wall of both subgenera varies from 0.8 to
1.8 microns. The Lepidobalanus usually showsa somewhat thicker wall than Cyclobalanopsis.
The wall in Cyclobalanopsis, however, is relatively thicker because of the small size of thegrain. The costae in Cyciobalanopsis are generally
heavier than those of Lepidobalanus. The shapeof costae and colpi in Cyclobalanopsis differsfrom that of Lepidobalanus. The shape of
costae and colpi in Cyclobalanopsis often showsa poroid area or a constriction (Bottema, 1974).
Cyclobalanopsis (evergreen Quercus)
Quercus acuta: 21-23 x 26-27 microns;
Quercus glauca: 29-20 x 21-23; Q. phillyraeoides: 20-22 x 23-26;
Lepidobalanus (deciduous Quercus)
Quercus serrata: 22-23 x 24-28 microns;
Q. dentata: 32-34 x 36-38; Q. variablilis:
29-30 x 31-33; Q. acutissima: 28-30 x
37-38.
Cyclobalanopsis occurs in the Temperate andWarm Temperate zones, and Lepidobalanus in
the Cool Temperate zone and in the northernpart of the Warm Temperate zone.

239

The use of the suffIX "-type" after the nameof a species or a genus implies that the fossil
may belong to the named species or genus or
to others of closely similar or identical morphology which have not been distinguishedby the writer. Thus, Pinus haploxylon-type
includes pollen grains of Pinus with five leaves
such as Pinus pumila, P. pen taphylla , and P.
koraiensis. This type is not divided into three
above-mentioned species on the basis of pollen
morphology. The use of "cf." as in cf. Cepharotaxus indicates that most of grains could bereferred to this genus.
(g) Zoning of Pollen Assemblages, and Interpretation of Vegetation and Climatic
History
In order to facilitate descriptions and discussions of the pollen assemblages, the pollen
diagrams are divided into 19 pollen zones basedon distinct changes in pollen percentages (Fujiet al., 1972). Changes in the ratio of Total AP
to Total NAP can be established, but changes
in the values of one or two pollen types may
also lead to the establishment of pollen zones
which have similar assemblages of pollen grains
and spores. The writer has attempted to indicate
them under the same letter code in order tofacilitate comparisons.
ZONE I, depth 195-198 m: The pollen
assemblage of this zone is defined by Pinus
diploxylon-type (46%), Picea (24%), Fagus
crenata-type (21%), and Cryptomeria (10%),and is characterized by a very high pollen percentage of plants thriving in the middle partof the Cool Temperate - Temperate zone. The
mean annual temperature of the summit areaand lowland at the time of this zone may havebeen higher than 5°C and 13°C respectively,
and the humidity was probably more or less arid.
ZONE II, depth 173-195 m: This zone ischaracterized by large amounts of boreal conifers, especially Abies and Picea, and Cool Temperate - Temperate plants. The climate in thelakeside at that time may be compared withthat in the middle part of the Cool Temperatezone. In the lowland areas, Cryptomeria, Pinus
diploxylon-type, Alnus, Fagus crenata-type,
Carpinus, Zelkova, Juglands, and Lepidobalanus

I>:)
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~

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E
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Text-fig. 3.

Arboreal pollen diagram of samples at 5 meters interval from a 200-meter core.

771. Palynology in Last 600,000 years, Lake Biwa

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I242

Norio FUJI

grew, and at the mountain sides Abies, Tsuga,
and Betula grew. Pinus pumila and Abies may
have prevailed in the summit area during thelater part of this period.
ZONE III, depth 168-173 m: Although thepollen percentages of the boreal conifers arealmost the same as in Zone II, the pollen valuesof broadleaved deciduous trees decrease, andplants of the Warm Temperate - Subtropicalzones such as broadleaved evergreen trees andPodocarpus attain relatively higher values. The
climate at that time may have been as warm asthat of the present day and relatively arid.
ZONE IV, depth 160-168 m: This zone· ischaracterized by an increase of plants of theCool Temperate zone and of the Cool Temperate- Temperate zones, and by a decrease in plantsof the middle part of the Cool Temperate Temperate zones and of the southern Temperate- Subtropical zones. Judging from the pollen
assemblages, the climate at that time may havebeen as cool as that in the southern part of theCool Temperate zone and was probably wet as
indicated by the large value of Cryptomeria.
ZONE V, depth 154-160 m: This zone ischaracterized by decreases in the Subpolar or
Subalpine plants and in the Cool Temperate Temperate plants, and by sharp increase in the
middle Cool Temperate - Temperate plants.
In the mountainous area, broadleaved deciduoustrees, Abies (perhaps A. firma), Picea (perhaps
P. polita) , and at the lakeside, Pinus densiflora
prevailed. There were also scattered Cryptomeria,
Zelkova, Juglans, Salix, and Alnus. The climate
may have been similar to that of the present
day.
ZONE VI, depth 148-154 m: Relatively
high percentages of the Subpolar or Subalpine
plants and Cool Temperate - Temperate plants,
and decreases in the percentage of the middle
Cool Temperate - Temperate plants and thesouthern Temperate - Subtropical plants are
the characteristic features of this zone. The
climate of the lowland at the time represented
by this zone may have been similar to that of
the middle part of the Cool Temperate zone.
ZONE VII, depth 128-148 m: The mainelements of this zone are Pinus diploxylon-type(28-34%), Cryptomeria (12-30%), and Abies(13-29%). This zone is characterized by boreal
conifers which lasted for a time with only longsmall fluctuations in abundance. The climaticcondition at that time was similar to that ofthe present day with temporarily cool periods.
ZONE VIII, depth 125-128 m: The pollen
assemblage of this zone contains Pinus diploxylon-type (28%), Abies (25%), Picea (11%),and Cryptomeria (9%). The zone is notable fordrastic increases in the Subpolar of Subalpine
plants, and boreal conifers, and for decreases
in the Cool Temperate - Temperate and southern Temperate - Subtropical plants_ The climate
during this time may have been similar to thatof the middle part of the Cool Temperate zone,
and was probably relative dry with the meanannual temperature of about 10° at the lakeside.
ZONE IX, depth 118-125 m: This zone issimilar to zones V and VII. The climatic condition at that time may have been somewhat
milder than that in the northern part of theTemperate zone. Abies (perhaps A. homolepis)
and Picea prevailed with a little Betula (perhaps
B. platyphylla) and Fagus crenata-type in thehigher part of mountainous area. In the lowlandarea, the broadleaved trees, especially Lepidobalanus, and Pinus densiflora probably prevailed.
ZONE X, depth 95-118 m: This zone ischaracterized by a high concentration of boreal
conifers, especially Abies (45%) andPicea (18%).
The climate in the lowland at that time may
have been as cold as that of the northern partof the Cool Temperate zone and dry, with atemporarily cooler interval during the middleof the period. On the other hand, in the mountainous areas, boreal conifers prevailed.
ZONE XI, depth 78-95 m: This zone ischaracterized by an increase in other plants
than boreal conifers. The climate in the lakesidearea may have corresponded to that of thenorthern part of the Temperate zone or of thesouthern part of the Cool Temperate zone,
and wetter condition probably prevailed.
ZONE XII, depth 71-78 m: This zone ischaracterized by increases in boreal conifers

771. Palynology in Last 600,000 years, Lake Biwa

and plants of the middle part of the Cool Temperate - Temperate zones. The climate in thelowland area around Lake Biwa may have been
as cool as those of zones VI and VIII, but, on
the other hand, Pinus haploxylon-type (hereperhaps P. koraiensis), Abies (perhaps A. homolepis) , and Picea (perhaps P. polita) presented
in the mountainous area.
ZONE XIII, depth 67-71 m: This zone ischaracterized by a markedly drastic increasein plants growing in the Cool Temperate Temperate zones, particularly Cryptomeria.
The climate was probably similar to that of
the southern part of the Cool Temperate zone,
c
~

.
".

243

and was clearly wetter.
ZONE XIV, depth 45-67 m: The mainelements of the pollen assemblage of this zone
are Abies (26-42%), Pinus diploxylon-type(21-26%), Sarix (24%), Picea (17%), and Cryptomeria (11-17%). The zone is marked bya drastic decline in plants thriving in the Cool
Temperate zone, and by a strong increase inboreal conifers. The climate appeared to havedeteriorated slightly during this time fromcool condition at the beginning of the period
to relatively cold and dry conditions at the middle
and at the end of the period.
ZONE XV, depth 27-45 m: The climate
Summary

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80

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----, I

Text-fig. 5. Summary pollen diagram of the palynological analysis of a 200-meter core. a:
Picea, b: Cryptomeria, c: boreal conifers, d: Pinus haploxylon + Larix (x 10), e: except Tsuga,
f: except Abies.

244

Norio FUJI

during the early part of this period may havebeen similar to that of the northern part of
the Temperate zone. In the late period, however,it became cooler and resembled that in the southern part of the Cool Temperate zone.
ZONE XVI, depth 16-27 m: During thisperiod the climate deteriorated and, in thelakeside area, boreal conifers and broadleaved
deciduous trees probably prevailed.
ZONE XVII, depth 13-16 m: This zone ischaracterized by a drastic decline in boreal
conifers. Instead of boreal conifers, plants of
the Cool Temperate - Temperate zones, particularly Cryptomeria (12%), and Lepidobalanus(16%) were relatively abundant. The climate
at that time may have been correlated to thatof the northern part of the Temperate zone orof the southern part of the Cool Temperate zone.
ZONE XVIII, depth 9-13 m: The climate
at the time represented by this zone had been
the coldest throughout the last 560,000 years,
and was almost comparable to that of Zone X.
In the summit and mountainous areas, Pinus
pumila, Abies (perhaps A. mariesii or A. veitchii),and Picea prevailed. Boreal conifers such as
Abies homolepis, A. {irma, Picea (? P. polita),
Pinus koraiensis, Betula (perhaps B. platyphylla)
and other broadleaved trees were distributedin the lowlands around Lake Biwa.
ZONE XIX, depth 0-9 m: During the tim!!
represented by this zone, boreal conifers and the
Cool Temperate plants decreased in abundance
and were replaced by plants growing near the
middle part of the Cool Temperate zone and in
the southern part of the Temperate - Subtropical zones. At this time, Lepidobalanus(perhaps Quercus crispula and Q. serrata),
Acer, Cryptomeria japonica, and Chamaecyparis
prevailed in the mountainous area instead ofAbies, Larix, and Ulmus as in the period represented by zone XVIII. On the other hand,
Lepidobalanus as Quercus acutissima and Cyclobalanopsis as Quercus glauca were distributed
widely with Salix and Alnus along the sidesof the lake and rivers. The climate of this time
may have been 10 _ 20 C warmer than and morehumid than at the present (Fuji, 1976).

Comparison with previous
palaeoclimatic analyses
The age determination of the upper part ofthe core from Lake Biwa has been carried out by
the C14 method (Horie et al., 1971), and theother by the fission-track method (Nishimura
et al., 1975). The age of the lowermost horizon,
about 200 m below the present lake bottom, isabout 565,500 years, B.P. With the use of the age
determination by C14 and fission-track methods,
and palaeoclimate by the palynology, the writerdetermined preliminary the ages of the boundaries between glacial and interglacial times, andbetween stadial and interstadial times.
Same samples from the 200-m core analysed
for the palynology, geochemistry and othermicropalaeontology were studied from the viewpoint of palaeomagnetism (Kawai et al., 1972).
All samples are belonged to the Brunhes normal
polarity epoch, the past 690,000 years, and the
new three short reversed polarity events, called"B", "Biwa I", and "Biwa II" from the lake bottom, have been recognized in the core. Judging
from a correlation between the palaeomagnetic
results from Lake Biwa (Kawai et al., 1972) andthese from some deep-sea cores (Opdyke, 1972;
Ninkovich et al., 1966), the "B" reversed polarity event at a depth of 50 to 55 m in the coreof Lake Biwa is correlated with the Blake event(Ninkovich et al., 1966; Denham, et al., 1975)
which is estimated to have lasted from 117,000
to 104,000 years ago. Then the "Biwa I" eventat a depth of 80.5 to 85 m and the "Biwa II"
event at a depth of 130.0 to 132.5 m are estimated respectively to be from 176,000 to
186,000 years ago and from 292,000 to 289,000
years ago (Yaskawa, 1974). Accordingly, sedimentation at the 200-m.J.evel must have begun
from the early stage of Brunhes normal polarity
epoch. Therefore, pollen analysis of this longcore stated in this paper has produced a record
for most of the Brunhes epoch.
The phases of vegetation development during
the time not covered by the radiocarbon andfission-track age determinations need to bedated by the other methods. Geological studies

771. Palynology in Last 600,000 years, Lake Biwa

from the surroundings of Lake Biwa unfortunately do not provide much evidence for suchdating. So the changes in vegetation and associated climatic changes inferred from thepalynological results offer the possibility forfurther dating. As there are no other palynological studies covering the 565,000 years
time span represented by the Lake Biwa core,
the writer correlated the pollen diagram from
Lake Biwa with Emiliani's palaeotemperature
curve (1966 & 1974) based on oxygen isotope
analysis. Emiliani's study covers the last 700,000
years and shows fluctuations in more detailthan palaeoclimatic curves from other deep-sea
cores (for example: Hays et al., 1969).
On the palaeoclimatic curve from Lake Biwa
(Text-fig. 6) cold, warm, and temperate climatic
periods are named as c-1, c-2, ... , w-1, andt-1, t-2.
The t-10 period (temperate climatic period)
is correlated with period no. 15 in Emiliani's
curve, but if estimated age by Kanari et at.
(1975) is correct, the end of t-10 period wasslightly later than period no. 15. A short andrelatively mild period separates the c-10 andc-12 periods. This mild period is correlated witha mild period between nos. 13 and 14 of the
Emiliani's curve. According to the present
writer's curve, the duration of the c-12 period
was as long, and the climate was as cold as thatof the c-11 period. Although there is a cold
period shown by no. 14 in Emiliani's curve correlated with the c-12 period, this cold period was
shorter and colder than the c-12 period. A temperate climatic period shown by an abbreviation
t-9 may be correlated with period no. 13 inEmiliani's curve. The latter, however, is chronologically older by about 10,000 years than theformer. Judging from the present analyses,
the duration of the t-9 period is inferred tohave been shorter than that of period no. 13.
This inconsistancy may result from the longsampling interval (5 m) used in the Lake Biwa
core. Shorter sampling intervals should be
used in the future.
The t-8 period is clearly correlated withperiod no. 11 of Emiliani's curve from the

~~

t,,;
~~

!

:~

t
z

i

."
0

245

1J

Text-fig. 6. Correlation diagram between
the palaeoclimatic change in the Omi Basin andpalaeotemperature curve based on oxygenisotope ratio determination from the Caribbean
Sea (Emiliani etal., 1974).

viewpoints of chronology and palaeoclimatology.
Lack of exact agreement is again attributed
to the long sampling interval in the Lake Biwa
core. Climatic fluctuations during the periods
from c-9 to c-7 are too indistinct to be correlatedwith Emiliani's curve. There are so many periodsof mild climate that it is difficult for example,
to decide which of these should be correlatedwith the Emiliani's no. 9. However, if it isassumed that the c-8 period is correlated witha cold period between the Emiliani's periods
no. 8 and no. 9, the t-7-b subperiod in the pres-246

Norio FUJI

ent curve may be correlated with the Emiliani's
no. 9. A mild climatic period shown by theabbreviation t~ may be correlated with the cool
period just before period no. 8 of Emiliani's
curve. Judging from chronological and palaeoclimatic investigations, it is most probablethat the cold c-7 and mild t-5 periods are correlated with periods no. 8 and no. 7 of Emiliani's
curve respectively. According to the writer's
analysis, the climatic condition during thetime interval from period c-7 to period c-6
was continuously cold. A marked drastic climate
amelioration is recognized in the time, about
210,000 years B.P., between period c~ andperiod t-5. A similar climatic amelioration is
occurred during the time interval from period
no. 8 to period no. 7 of Emiliani's curve but
this interval appears to correspond precisely
to the time interval from period c-6 to period
t-5 in absolute age. The mild t-5 period may
be correlated with Emiliani's period no. 7,
judging from the climatic fluctuations recorded.
Emiliani and Shackleton (1974) showed
two tentative palaeotemperature curves forthe period between the mild period no. 7 andcold no. 4. According to the present writer's
curve, the climate during this time may havecorrespond more closely to the trend of theperiod line in Emiliani's curve, except in the
period around about 120,000 years B.P.
The e-3, t-3, c-1, and t-1 periods may becorrelated with periods nos. 4, 3, 2 and 1 ofEmiliani's curve, respectively.
In conclusion, judging from this detailed
comparison there are a few differences between
Emiliani's generalized temperature curve fromthe Caribbean Sea and the present writer's
climatic curve from Lake Biwa, still there seems
a general similari ty between the curves.

The contents of heavy metal irons in thesamples are almost similar to those of soils in
unpolluted areas. Ranges of determined values
are as follows. As: 9-58 ppm, Cd: 0.24 ppm,
Cu: 34-66 ppm, Mn: 620-5300 ppm, Pb:
18-43 ppm, Zn: 98-160 ppm. However, thefact that the highest peakes of Cd and Mncontents are observed at the depth of 130 m
suggesting that some environmental change
might have taken place at around the age of
300,000 years B.P. The four peaks also correspond to the minimum values of organic carboniorganic nitrogen ratio (Koyama et aZ., 1973).
The content of organic carbon varies similarly tothat of the total carbon showing four remarkablepeaks at 15 m, 90 m, 140 m warm periods which
are recognized from the results of palynologicalanalysis. According to vertical profiles of organiccarbon and nitrogen content of the core samples,ranging 4.4-14.7 mgC/g of dry sediment and
1.0-2.3 mgN/g of dry sediment respectively,
were found to be almost similar to that of size
distribution of the fine-grained clastics. Thissuggests that the allochthonous materials must

' - -_ _ _ _ _

~3

,,]03

JlI~/, Dr,. II.rI.
10

12

peCIc Dr")' •• d.
14

16

XI0 3

P

D.···· ..'~_--'0_---~- .. c,! 100Comparison with chemical, palaeomagnetic,
and fossil diatom analyses
The samples examined for the contained
microflora were also investigated from palaeomagnetic, chemical, granulometric, mineralogical,
and fossil diatoms aspects.

Text-fig. 7. Vertical distribution of total
carbon and nitrogen in the core sample from
Lake Biwa (Koyama et al., 1973).

247

771. Palynology in Last 600,000 years, Lake Biwa

contribute to the sedimentary organic materials
in certain extent. This fact was supported by
the low values of the C 16 + C 1S /C 20 - C 30 ofdicarboxylic acids of the sediments, because
C20 - C30 of the acids are mainly drived fromthe terrestrial plant wax, whereas C 16 and C 1S
acids are main constituents of dicarboxylic acidsin the autochthonous phytoplankton. The
concentration of phaeopigment and carotenoids
was determined to vary with intervals of thecore depth. Vertical profiles of these plant
pigments are almost similar with those of carbohydrate, amino acids and protein and lipid andwith that of fossil diatoms. These facts suggestthat the productivity of organic materials dueto the photosynthetic activities of diatoms
in this lake varied with time in the past time.
In addition, vertical profiles of these organic
materials and fossil diatoms were found to bequite similar with the change in the palaeo-temperature around this lake, which was established on the basis of palynological analysis
by the present writer.
The positive correlation between the totalorganic contents and l) 13C values can be foundthroughout the core samples. The isotopic
composition of organic carbon becomes enrichedin l) 13C with increase in the organic carbon
contents. The isotopic variation in organiccarbon in the core samples is undoubtedly
controlled with a kinetic isotope effect due tothe temperature at which plankton grew. In
warmer climate, the production rate of organic
materials such as plankton in the lake andtheir accumUlation rate in the sediments are
relatively higher, resulting in relatively higherl) 13C enrichment than those in a colder climate.
The palaeoclimatic variation estimated bypalynological investigation shows an excellent
correlation with that by the l) 13C values. From

Change of climate (Fuji. 1977)
t-5

t-6

C-4

C·6

50

100

C·7

t-l0

t-8

t·7
C;8

C-9

C·lO
,

--;;
~

C

-32

0

-e.

u

~

-34

.....00
~u

'"

-36

-38

.....~~A (Mori.1974)
100

:8
x

:iii
OJ
u

e
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:a

50

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S0
E-<

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0

200
Depth below the la~e bottom (m)~,I ~<o

14.98

80

110

170 180270460

Time(XlO'year B.P.lby "Candfission·track methods(Horie.Nishimura}

Text-fig. 8. Comparison among the change of climate (Fuji, 1977), l) 13 c oforganic Carbon and total diatom cells from the samples a 20Q-meter core in Lake

Biwa.

248

Norio FUJI

The palaeomagnetic study of the 200-m
core reveals that there are three short reversed
polarity events in the Brunhes normal plarity
epoch (Kawai et al., 1972). Comparison between
the results of the magnetic reversals and of
the palaeoclimate estimated by the palynologicalresearch is shown in Text-figs. 6 and 9. Viewed
from the tentative conclusion on the palaeoclimate during the last 0.6 million years, thecold periods may be chronologically responded
to the reversed polarity events. Although thereason remains unknown, when the polarity
was reversal, it has not been solved yet in thepresent why the palaeoclimate was cold or cool(Kawai et al., 1972). In addition, it is a very
noticeable fact that some horizons were foundin the core at which the variation of fossil diatom
abundance and species was correlated with theevent of oscillating geomagnetic field. The
correlations are shown in the following Table 1.
Among the correlations one at the Biwa event
II was the most conspicuous. It can be con·this isotopic study, it can be concluded thatthree or four glacial and interglacial ages wererepeated in the depositional history of Lake
Biwa sediments during the past 600,000 years(Nakai, 1973).
On diatom fossils (Mori, 1975) the following
are noticed. Two genera of Melosira and Stephanodiscus, which belong to discoid diatoms andare planktonic habitat, are observed abundantly
through the core column. A diatom assemblage
consisting mainly of Melosira solida and Stephanodiscus carconensis, which are observed in
the lake at present, is found in a part of 75.0 m
in core depth and above. And below that depth
diatom assemblages differ remarkably fromthe viewpoint of a dominant species of diatom.
It is possible to recognize five diatom zones in
the core column based on the rise and fall in theabundance of Melosira solida. There are four
periods in the core column when M. solida isyielded abundantly. Lake Biwa was undera temperate to warm climate in those peirods.

41 da pText-fig. 9. Comparison between the change of palaeoclimate based on thepollen analyses and the intensity of palaeomagnetism in samples of a 200-metercore from Lake Biwa. 1: palaeoclimatic change based on pollen analyses; 2: intensityof palaeomagnetism.
Table 1. Relationship between geomagnetic events and variation of
diatom assemblage from a 200-meter core.
Geomagnetic events

Microfloral change of diatom

B (Blake event)Extinct horizon of Melosira cf. juergensi

C (Biwa event I)

Decrease horizon of M. cf. juergensi

C-D (weak magnetism)

Bl diatom su bzone

D (Biwa evnet II)

Decrease horizon of Melosira salida & M.
cf. juergensi

771. Palynology in Last 600,000 years, Lake Biwa

sidered that an oscillating geomagnetic field hadsome influence on the diatom fossils existence,
though it might be indirect.
The scientific solution of these similarity
is due to the detailed measurements and analyses
and to the co-operation with the scientists ofboth geophysics and cosmophysics (Kind, 1969).

249

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Conclusions(1) Judging from the pollen analyses, the200-m core samples of Lake Biwa can be divided
into 19 pollen zones; Zones I, through XIX.
(2) The climatic curve and ages from Lake
Biwa display similarity to the palaeotemperature
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(3) During the glacial stages or stadials, thetypical vegetation thriving today in the Subpolaror Subalpine zone of Japan prevailed at thesummit area and/or the montane area around
Lake Biwa and, in the lowland around the lake,
plants growing today in the Cool Temperatezone were distributed. In the interglacials andinterstadials, the vegetation in the higher area
was characterized mainly by plants of the Cool
Temperate zone and the present Temperate zone,
and in the lowland, the vegetation was composed
mainly of broadleaved deciduous and evergreen
trees growing in the Warm Temperate zone.
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and by cutting woods began about 3,000 years
B.P. The influence is supported by the archaeological evidence around the lake.

of Lake Biwa and Japanese Pleistocene,250

Norio FUJI--(1976): Palaeoclimatic and palaeovegetational changes around Lake Biwa, Central
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- - , Mizuno, A. and Aoki 1. (1974): Method
and operation of deep coring at Lake Biwa.
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Koyama, T., Mizuno, A., Ishiwatari, R., Ogura,K., Handa, N., Terashima, M., Koyama, M.,
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p.149.

771. Palynology in Last 600,000 years, Lake Biwa
Kuroda, T. (1947): Freshwater Molluscs ofLake Biwa. Yumehamaguri, vol. 3, p. 26-51.
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30, p. 81-119.

251

Tsuboi, C., Jitsukawa, A. and Tajima, H. (1954):
Gravity survey along the lines of precise
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21, p. 1-77.
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Yokoyama, T. (1973): An outline of Quaternary
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--and Horie, S. (1974): Lithofacies on a
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Paleolimnology of Lake Biwa and theJapanese Pleistocene, vol. 2, ed. S. Horie,
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- - , - - , Fuji, N., Handa, N. and Kanari, S.
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Wright, Jr., H. E., McAndrews, J. H. and van
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Lake Biwa l'eg; ylJi , Fujihara·dake fii;JJj{ /Ir, Fukui miff, Gifu ~!it.$., Gozaisho 1JlIitEffl, Hidaka
B i¥Ii, Hiei .it1&', Hira .it~, Hokuriku ~tlW, Ibuki W~, Iga W1JI., Ise Bay W~rElj, Kaburaki Ej3 ~~, Kinki J!ft&, Kyoto JiOIiL Mie =:m, Mikuni·ga-dake =:j;!iI 'r ffi, Mizuguchi
IJ ,Nara ~~, Nosaka ffl:&:, Okinoshima i4'/ tfl" Omi JliiI, Osaka *~, Otsu *~, Shiga Y!,j!l,Suzuka ~Im, Wakasa *~, Yanagase:jljD 'rifj*Norio FUJI

252

Rfi!i~/& 200m ;f,-!i '/'7'. -IT,/7',J.-oy7E:f#''¥=1'19li1f'1E I: )~:k60TJ1pr..'0)t:llmi1:ct:l~r:l ;jq:.;t;vt 0t.f,gg*c~ 3m l.: -C O)t:lilll1=. O)ilr),fIU: .:t hl:'];--':> <t:I~1W::O) grfl:: z.'1E IlJl
L-C. ~~~;t;vt~.ggeO)~.gr~0) • • 0)10K~~~cz.§~cL-C. 1~11p~. De
1'~0) 7/\im 65 m O)iM/!Eb, I?ff0 200 m I:. 7it~;f, - !i '/ 1J'~~Mtt Lt.:o .:t L -C. 7€;1v c'7'C~t:.;ru
R~~~7z. • • ~~~c~«~ ~0)~7·-lT'/~~~. liIf'1EO).-~~cL-C. 5m~~
1=t~~ ~h. 1'E1M};jfrO)tJVA;;b' I? liIf'1E ~ht.:o .:to)f,,'L!l1:. 200 m ~ 7 ':tl90)1Er)H*I:.~7t~h.
f:J60TJ1pr"'1:.12@l0)~t,i!m (7./CWD c 10@lO)mtfnJtJjO)iHE Lt.: ~ C b~nm~~ ~ht.:o ~ O).J: ? it.
ilf2W1I:.;t;vt ~ ~.~fI::O)~c~z.:h !i ~lfijb' I? O)M*fJiJ{ft{;i;I:'.J: ~ t:l7Jciffit~fl:: CJ:1:if,(i"" ~ c.
3t~1'191;::.7,..-C.J: Oi~f!;(~~o tJ:;t;. J.H!W1~b'I?O)-Ij-'/~'J.-I;t. :.tfll!HI::"¥=. 013C, fH.U~~.
7 -f "/ Y" '/. r '7 "/ 1Jfi,;1pt\;;iJ!.lJ~. 7itv:t:l11!!~~~O)mfm,r2:b'l?t'1EfJJl~h. ~~*~fl::c.:thl?cO)~if,(.Htm~-c~~~o•~O)gri!

m.

Trans. Ptoc. Palaeont. Soc. Japan, N. S., No. 132, pp. 253-262, pIs. 51-53, December 30,1983

772. RADIOLARIANS IN MIDDLE JURASSIC SILICEOUS SHALEFROM KAMIASO, GIFU PREFECTURE, CENTRAL JAP AN*
SHINJIRO MIZUTANI AND SATOSHI KIDO**
Department of Earth Sciences, Nagoya University,
Nagoya 464, Japan.

Abstract. Three new species of Radiolaria, Pantanellium fovea tum, Dictyo·
mitrella(?) kamoensis and Pachyoncus kamiasoensis, are described from the middle
Jurassic siliceous shales in Kamiaso, Gifu Prefecture. These species together withother spumellarians and nassellarians characterize the Dictyomitrella(?) kamoensis- Pantanellium foveatum Assemblage, which is commonly found in the radiolarianassemblages recognized in the sedimentary complex of the Mino area, central Japan.

Introduction

its biostratigraphic position in the Jurassic
succession in the Mino area, central Japan.
Dr. E. A. Pessagno, Jr., University of Texas
at Dallas, and Dr. K. Nakaseko, Osaka University,
gave us many instructive suggestions on theJurassic radiolarian biostratigraphy. Dr. A. Yao
and Mr. T. Matsuoka of Osaka City University
kindly informed us their biostratigraphic resultsin the Mino area. Dr. M. Adachi, Mr. I. Kawa·
guchi, and Mr. S. Kojima of Nagoya University
showed us their micropaleontologic data dis·cussing the litho· and biostratigraphy in theirfields of central Japan. Dr. K. Shibata of Geo·
logical Survey of Japan who generously joined
us in the study of the chronostratigraphy of
the Jurassic formations, carried out the isotopic
age determinations on our samples. We are muchindebted to all of them, and would like torecord our sincere appreciations for their kind·ness and encouragements.
The expense of this study was partly defrayedby Grant-in·Aid for Co-operative Research of
the Ministry of Education, Science and Culture(Grant No. 57340047).
All the original data of the radiolarian fossils
treated in this paper are stored in the Rad File,
Department of Earth Sciences, Nagoya Univer·

The radiolarian micropaleontology and bio·
stratigraphy have been rapidly advanced in thisdecade through the advent of new techniquesin laboratory works. The results of developments
have forced us to reappraise our ideas about
stratigraphy and geologic history of central
Japan. We have carried out an extensive field
investigation in the Mino area, in the course ofwhich we recognize three Jurassic radiolarianassemblages, i.e., (1) the Mirifusus baileyi, (2)the Dictyomitrella sp. A - Pantanellium sp. A,and (3) the Unuma echinatus Assemblages(Mizutani et al., 1981; Kido et al., 1982). Radio·
larian species in the respective assem blage werereported in each type area by Mizutani (1981),
Kido et aL (1982), and Mizutani and Koike(1982).
We describe in this paper three new speciesof radiolarians which represent the second
assemblage of the above-mentioned three, andintroduce the DictyomitreUa(?) kamoensis Pantanellium fovea tum Assemblage, discussing* Received November 1, 1982, read Oct. 17,
1982 at Tsu.

** Present Address:

Mikata School for the

Delicate Children.
253

254

Shinjiro MIZUTANI and Satoshi KIDO

sity. The data are numbered, for example, as
22789/542, in which the numerator representsa sequential number of SEM negative film andthe denominator indicates that of the rockspecimen from which the radiolarian fossil
was extracted.
Geologic setting
The Kamiaso area was geologically studied
by Mizutani (1964), and subsequently by Adachi
and Mizutani (1971), and recently by Kano
(1979). Paleontologic researches have been
performed by Koike et al. (1971), Igo and
Koike (1975) and Igo (1979) on conodonts,
and by Nakaseko and Nishimura (1979) andMatsuda and Isozaki (1982) on radiolarianfossils. Kido (1982) and Kido et al. (1982)
also have carried out radiolarian biostratigraphic
works for a continuous outcrop of siliceous
shale and chert exposed along Hidagawa (HidaRiver). The studied area reported in this paper
is composed mainly of chert, siliceous shale,
black shale interbedded with turbidite andsandstone, trending approximately NE-SW (Text.
fig. 1). Although these formations are apparently
seen to be conformably overlain by successive
beds with the thickness of the order of hundred
meters, detailed mapping reveals that some ofthem occur repeatedly in places in much smallerscale. The duplicate and interleaved occurrenceof a lithologic unit is also verified by the bio.
stratigraphic study, which then confirms a close
relationship between the lithostratigraphy and

rn:Jporphyrite

middle {~ sandstone and shale
Jurass i c E:::3
E:3 sil iceous tuffaceous shale~~~~1/r~ [llI] bedded chert
earlyIIlllIlll1Il chert - siliceous shale
Triassic ~ alternation

Text·fig. 1. Geologic map of the Kamiaso area and sampling locations. The
dotted area in the inset map shows the distribution of the Mesozoic·Paleozoic
sedimentary complex of the Mino area, central Japan.

772. Middle Jurassic Radiolarians

the chronostratigraphy.
Measured stratigraphic sections and biostratigraphic analyses reported by Kido (1982), Kido
et al. (1982) and Matsuda and Isozaki (1982)
along the exposures of the Hida River show
the middle Jurassic siliceous shale to be underlain
by middle Triassic to early Jurassic bedded
chert, and overlain in tum by sandstone and shale
totaling approximately 200 m in thickness (seeText-figs. 1 and 2). The middle Jurassic shale
appears to cover the early Jurassic bedded chert;
but because a minor bedding fault is foundparallel to the lithologic boundary between
them, and because minor intraformational folds
are occasionally developed in the lowest partof the shale, the stratigraphic continuity cannot
be ascertained; it is also presumable that there
is a stratigraphic break between them.

et al., 1981; Kido et al., 1982), the Unuma
echinatus Assemblage and the Dictyomitrella(?)
kamoensis - Pantanellium fovea tum Assemblage,
in which latter new species of radiolarian fossils
described in this paper are much more commonly
contained.
Kido (1982) and Kido et al. (1982) reported
radiolarian species identified in each assemblage;
among them, Acanthocircus hexagonus (Yao),
Acanthocircus suboblongus (Yao) , Eucyrtidium(?) unumaensis Yao, Stichocapsa japonica
Yao, Tricolocapsa cf. riisti Tan and Tricolocapsa
plicarum Yao are common in both assemblages.
The Unuma echinatus Assemblage of this area ischaracterized by concurrence of Parasatumalissp., Unuma echinatus Ichikawa and Yao, andCyrtocapsa mastoidea Yao as described by
Ichikawa and Yao (1976), Yao (1972, 1979)
and Yao et al. (1980) in the Inuyama area,
while the Dictyomitrella(?) kamoensis - Pantanellium foveatum Assemblage is characterized
by the abundance of Pantanellium foveatumn. sp., Pachyoncus kamiasoensis n. sp. andRadiolarian Assemblage
In the Jurassic shale of this area, we recognized two radiolarian assemblages (Mizutani

Kashlbara

Kamlaso
BridgeHisulkyobedded chert' .• .' . sandstoneandu..... . shale

Vl

Fault

Vl

0
L.

black
shale

~

....,

Q.l

535
"C
"C

E

....,.

-

255

542
/
"
,,,, "'''faul t
orbreak

s11 iceous shale
bedded chert

>L.

oQ.l

D.P.

Dictyomitrella(?) kamoensis - Pantanellium foveatum Assemblage Zone

U.e.

Unuma echinatus Assemblage Zone

Text·fig. 2. Measured stratigraphic sections and rock'specimen numbers at
Kashibara, Kamiaso Bridge and Hisuikyo (see Text·fig. 1).

256

Shinjiro MIZUTANI and Sa toshi KID 0

Dictyomitrella(?) kamoensis n. sp. These new
species, however, do not always occur exclusively
in the above-said assemblage, but they areoccasionally found in the Unuma echinatus
Assemblage. It is very likely that the Unuma
echinatus Assemblage and the Dictyomitrella(?)
kamoensis - Pantanellium fovea tum Assemblage
are inherently comprised in a fossil association
occurringin a chronologically continuous
formation.
As discussed by Mizutani and Koike (1982)
and Shibata and Mizutani (1982), the Unuma
echinatus Assemblage zone of Unum a, Gifu
Prefecture, is probably of the Bajocian, whichis equated with that of Kamiaso biostratigraphi·
cally as well as lithologically. The field investi·
gation suggests that shale carrying radiolarian
remains of the Dictyomitrella(?) kamoensis Pantanellium foveatum Assemblage apparently
conformably overlies siliceous shale of the
Unuma echinatus Assemblage. In the Kamiaso
area, Ristola(?) turpicula Pessagno and Whalen,
described later, coexists with Pantanellium
fovea tum n. sp. and Dictyomitrella(?) kamoensis
n. sp. in the siliceous shale. According to Pessagno
and Whalen (1982), Ristola(?) turpicula is foundin the late Bathonian sample of the Snowshoe
Formation of Oregon. In Southwest Japan,
regional correlation made by Yao et al. (1982)
on the Triassic and the Jurassic formations
demonstrates that the Unuma echinatus As·
semblage zone is successively covered with thesiliceous shale or mudstone carrying radiolariansof their Lithocampe(?) nudata Assemblage,
which can be correlated to our Dictyomitrella(?)
kamoensis - Pantanellium fovea tum Assemblage.
All these data consistently indicate the sili·
ceous shale of the Unuma echinatus Assemblage
to be overlain successively by that of the Dictyomitrella(?) kamoensis - Pantanellium fovea tum
Assemblage in Southwest Japan. The stratigraphic sequence containing radiolarian fossilsof these two assemblages probably ranges inage from the Bajocian to the Bathonian, or
possibly to the Callovian.
We describe herein three new species of
middle Jurassic radiolarians, two of which aremarker .species with distinctive morphologic
characters, occurring commonly in Southwest
Japan, and characterize the Dic ty om itrella (?)
kamoensis - Pantanellium foveatum Assem blage.
Pachyoncus kamiasoensis n. sp. is regarded
as a supplementary species in this assemblage,
while Ristola(?) turpicula Pessagno and Whalen
is dealt with as a key taxon for a biostratigraphic
correlation in the Circum-Pacific radiolarian
realm.
Systematic Description
Subclass Radiolarian MUller, 1858
Superorder Polycystida Ehrenberg, 1838,
emend. Riedel, 1967
Order Spumellariina Ehrenberg, 1875
Genus Pantanellium Pessagno, 1977
Type species:-Pantanellium riedeli Pessagno,
1977, p. 78, pI. 6, figs. 5-11.
Pantanellium fovea tum Mizutani
and Kido, n. sp.
PI. 51, Fig.1a-1d, 2a-2c;PI. 52, Fig. 1-3

Pantanellium sp. A Mizutani etal., 1981, p. 197,
fig.2b.

Description:-Cortical shell spherical withlarge hexagonal and pentagonal pore frames(predominantly hexagonal). All pore frames
have circular pits at pore frame vertices andhave short flat secondary spines at bars between
pore frame vertices. The presence of the pits
mentioned above is much more distinctly manifested by the stereophotographs as shown in
Plate 51, Figs. 1c and 1d. Bars of pore frames
moderately thick along Y and three to fourtimes thicker along Z (designations describedherein are after Pessagno and Blome, 1980,
p. 241, text-figure 5). Five pore frames visible
along AA', while five pore frames also visible
along BB'. Shorter polar spine about 3/4 lengthof longer one. Proximal 3/4 to 4/5 part of the772. Middle Jurassic Radiolarians

shorter spine is triradiate in the axial section
and its distal 1/4 to 1/5 circular in the same
section, longitudinally composed of threemoderately wide, flat-topped ridges about
the same width along polar spine, alternatingwith three relatively wide grooves. The grooves
become wider proximally. Longer polar spinewith three flat-topped ridges about the same
width as that of shorter spine. The ridges also
alternate with three wide grooves longitudinally.
First medullary shell with fragile hexagonal andpentagonal pore frames is connected with twotriradhite primary radial beams and numerous
thin secondary radial beams (Plate 52, Fig. 1).
Remarks:--I'antanellium fovea tum n. sp. differs from all other species of Pantanellium bypossessing diagnostic circular pits at all verticesof pore frames. Pantanellium baileyi Pessagno
and Blome and Pantanellium malheurense
Pessagno and Blome have flat secondary spines
along bars between nodal points, but do nothave any pits at pore frame vertices. Secondaryspines of Pantanellium fovea tum n. sp. arerather short. Some specimens have narrower
ridges than the type specimen on both polar
spines completely triradiate in axial section,
but their cortical shell has similar structure(PI. 52, Figs. 2 and 3). We assign these forms
to Pantanellium fovea tum n. sp., too.
Etymology:-Fovea (Latin, feminine) = pit.
Measurements:,system of measurement described below is based on that of Pessagno andBlome's description (1980, p. 241, text-figure 5).
AA'A'S'AS BB' cc' dd' (micron)65 72 60 62 24 24 Holotype
70 80 60 65 24 22 Paratype
64 70 53 64 22 23 Average of 20
specimens
70 80 60 72 28 25 Maximum in 20
specimens
55 60 40 57 18 20 Minimum in 20
specimens
Type locality:-Kamiaso, Gifu Prefecture,
central Japan.
Deposition:-Holotype (16395/535), paratype(12253/334 ).

257

Occurrence:-Mino area, central Japan. See
Mizutani et al. (1981) p. 195, fig. 1. This species
is also reported by Wakita (1982) from thenorthern part of the Mino area (pI. 7, figs. 1
and 2), and similar species is found by Owada
and Saka (1982) in the Kanto Mountains (pI. 1,
fig. 2). It is highly probable that this species iswidespread in Southwest Japan.

Genus Pachyoncus Pessagno and Blome, 1980
Type species:-Pachyoncus tumidus Pessagno
and Blome, 1980, p. 237, pI. 10, figs. 9, 16,17,
19,20, pI. 11, fig. 12.
Pachyoncus kamiasoensis Mizutani
and Kido, n. sp.
PI. 52, Fig. 4a-4d; PI. 53, Fig. la-lc

Description:-Cortical shell subspherical orrather subcylindrical with large hexagonal andpentagonal pore frames. Four or five pore frames
visible along AA', five pore frames visible along
BB'. Pore frames have short, triradiate secondaryspines or circular pits at pore frame vertices.
Some secondary spines are connected withneighbouring secondary spines by thickeningof bars between nodal points. Otherwise, bars
have very short secondary spines between nodal
points. These morphologic characters of thisspecies can be observed in the stereophotographs
as displayed in Plate 52, Figs. 4c and 4d, andin Plate 53, Figs. la and lb. Bars of pore frames
moderately thick along Y, three or four times
thicker along Z. Both of polar spines quite wide
proximally, triradiate in axial section. One polar
spine shorter than the other. Both polar spines
have three wide ridges alternating with threewide grooves.
Remarks:--I'achyoncus kamiasoensis n. sp.
is closely related in form to Pachyoncus crassus
Pessagno and Blome, which has short triradiate
secondary spines connected with neighbouringsecondary spines by thickening of bars, andcircular pits at pore frame vertices. ButPachyoncus kamiasoensis differs from the latter in having

258

Shinjiro MIZUTANI and SatoshiKIDO(i) bars of pore frames thicker along Z, and(ii) thicker polar spines.
Etymology: - Pachyoncus
kamiasoensis isnamed for Kamiaso, its type locality.
Measurements:AA' A'S' AS BB' cc' dd' (micron)70 100 9070 32 34 Holotype
70
8270 35 33 Paratype
66 104 9077 34 32 Average of 12
specimens
75 12010090 40 40 Maximum in 12
specimens
55 95 6070 30 30 Minimum in 12
specimens
Type locality:-Kamiaso, Gifu Prefecture,
central Japan.
Deposition:-Holotype (22789/542), paratype(22785/324).
Occurrence:-Mino area, central Japan.

Order Nassellariina Ehrenberg, 1875
Genus Dictyomitrella Haeckel,1887
Type species:-Eucyrtidium articulatum Eh·renberg, 1873, p. 226; 1875, pI. 11, figs. 2, 3
(subsequent designation by Campbell, 1954,
p. D140).
Dictyomitrella(?) kamoensis Mizutani
and Kido, n. sp.
PI. 53, Figs. 2, 3, 4a-4b"Dictyomitrella" sp. A; Mizutani et aL, 1981,
p. 197, fig. 2a.

Description:-1J'est conical to subcylindricalhaving six to nine segments. Cephalis dome·
shaped without hom, and with or without small
pores at the joint to thorax. Thorax truncate·conical with one row of pores at the joint toabdomen. Abdomen and post·abdominal cham·bers also truncate-conical, a few last chambers
cylindrical in form, and increasing slightly inheight and moderately in width. Abdomen andpost-abdominal chambers separated by nodose
circumferential ridges have each one row ofpaired pores just below and above the ridges,
pores increasing in size toward distal segments.
Ten to fifteen pores visible along circumferential
ridges. Abdomen and post·abdominal chambers
have tetragonally -arranged two rows of circularpits somewhat larger than neighbouring pores,
pits and pores arranged trigonally.
Remarks:-We tentatively assign this species
to genus Dictyomitrella, belonging to a conicalor subcylindrical multicyrtid Nassellaria, which
has circumferential ridges with each one rowof pores below and above and has imperforate
surface on medial part of post·abdominal seg·ments. Dictyomitrella(?) kamoensis n. sp. isquite similar to Canoptum(?) sp. A of Pessagno
and Whalen (1982, p. 125, pl 7, figs. 14 and16), but diagnostically differs from the latterby lacking inner layer of polygonal pore frames(Plate 53, Figs. 4a, b). Dictyomitrella(?) kamoen·
sis n. sp. has a single layer of thick wall withsmooth inner surface and two rows of circular

Explanation of Plate 51 (marker = 50 microns)
Figs. 1 and 2. Pantanellium foueatum Mizutani and Kido n. sp. (la-1d, holotype; 2a-2e, para·
type)
1a, 16395/535.
1b, 16398/535; upper part of fig. 1a.
1e, 16396/535.} sereopth oograpt
h sof eorbe. al sh eo
II ffi 1
1d,16397/535.
Ig. a.
2a, 12253/334.
2b, 12207/334; axial view of shorter spine of fig. 2a.
2e, 12206/334; axial view of longer spine of fig. 2a.

MIZUTANI and KIDO : Middle Jurassic Radiolarians

Plate 51

259

772. Middle Jurassic Radiolarians
pits on outer surface. Dictyomitrella(?) kamoensis n. sp. differs from Dictyomitrella sp. A (De
Wever et al., 1979, p. 90, pI. 5, figs. 12, 16) bypossessing one row of pores not only just below
but also just above the nodoce circumferential
ridges. It also differs from Triassocampe ofDumitrica et al. (1980) by having segmentswith the largest diameter in its lower part.
Etymology:-Dictyomitrella(?) kamoensis n.
sp. is named for Kamo-gun, Gifu Prefecture,
its type locality.
Measurements:Length Width
180
160
156

95
90
92

180

105

130

85

(micron)Holotype with 8 segments
Paratype with 7 segments
Average of 11 specimens
with 7 segments
Maximum in 11 specimens
with 7 segments
Minimum in 11 specimens
with 7 segments

Type locality: -Kamiaso, Gifu Prefecture,
central Japan.
Deposition:-Holotype (12675/396), paratype(11643/391).
Occurrence:-The present species occurs widely in the Mino area, central Japan. Hattori and
Yoshimura (1982) reported this species fromthe Nanjo area (pI. 3, fig. 4), Kojima (1982)
from Takayama (pI. I, fig. 3), Wakita (1982)
from the northern margin of the Mino area
(pI. I, fig. 6), and Yao et al. (1982) described
the occurrence of similar species from Inuyama(pI. 3, fig. 21). Owada and Saka (1982) also
reported this species from Kanto Mountains(pI. 1, fig. 14). All of these papers suggest thewide occurrence of Dictyomitrella(?) kamoensis
in Southwest Japan.
Genus Ristola Pessagno and Whalen, 1982

Type species: -Parvicingula(?) procera Pessagno, 1977, p. 86, pI. 9, figs. 6--9.
Ristola(?) turpicula Pessagno and Whalen
PI. 53, Fig. 5

Ristola(?) turpicula Pessagno and Whalen, 1982;
pI. 11, figs. 8, 12, 13,16,20; pI. 13, figs. 11.
Description:-Apical portion of the test
conical and termination blunted, lacking a hom.
Except for the apical portion, the upper halfof the post-abdominal chambers is cylindrical,
whereas the remaining lower part of the test
is slender fusiform. Circumferential ridge distinct
in the medial and distal part of the test andis not well developed in the upper half. Postabdominal chambers always have coarse pentagonal and hexagonal pore frames arranged inthree rows. Length of the test 150 microns
and width of the basal part 80 microns, comparatively smaller in size than those of Pessagno
and Whalen's specimen. The present specimen,
however, closely resembles what was describedby Pessagno and Whalen, especially that of
their paratype (plate 11, figure 12).
Deposition:-12214/334.
References
Adachi, M. and Mizutani, S. (1971): Sole markings and paleocurrent system in the Paleozoic group of the Mino terrain, central
Japan. Mem. Geol. Soc. Japan, no. 6, p. 3948, pIs. 1-3. [in Japanese with English
abstract]
Campbell, A. S. (1954): Radiolaria, in R. C.
Moore (ed.) Treatise on Invertebrate Paleontology, Part D, Protista 3, p. D11-D163.
De Wever, P., Sanfilippo, A., Riedel, W. R. and
Gruber, B. (1979): Triassic radiolarians
from Greece, Sicily and Turkey. Micropaleontology, vol. 25, p. 75-110, incl.
pis. 1-7.
Dumitrica, P., Kozur, H. and Mostler, H. (1980):
Contribution to the radiolarian fauna of
the Middle Triassic of the Southern Alps.
Geol. Paliieont. Mitt. Innsbruck, Bd. 10,
p. 1-46, inci. pIs. 1-15.
Ehrenberg, C. G. (1838): t:Jber die Bildung derKreidefelsen und des Kreidemergels durch
unsichtbare Organismen. Abh. Koenigl.
Akad. Wiss. Berlin, p. 59-147, pI. 1.
--(1873): Grossere Felsproben des Polycystine - Mergels von Barbados mit weiteren
Erliiuterungen. Monatsber. Koenigl. Preuss.

260

Shinjiro MIZUTANI and Satoshi KIDO

Akad. Wiss., p. 213-263.
--(1875): Fortsezung der mikrogeologischenStudien als Gesammt-tJbersicht der mikroskopischen Paliiontologie gleicharting analysirter Gebirgsarten der Erde mit specieller
Riicksicht auf den Polycystinen Mergel vonBarbados. Abh. Konigl. Akad. Wiss. Berlin,
p. 1-'-225, pIs. 1-30.
Haeckel, E. (1887): Report on the Radiolaria
collected by H. M. S. Challenger during theyears 1873-76. Rept. Sci. Result. Voyage
H. M. S. Challenger, Zool., vol. 18, p. 11803, pIs. 1-140.
Hattori, I. and Yoshimura, M. (1982): Lithofacies distribution and radiolarian fossils
in the Nanjo area in Fukui Ptefecture,
central Japan. News of Osaka Mic ropa leontologists, Spec. Vol. no. 5, p. 103-116,
incl. pIs. 1-4. [in Japanese with English
abstract]
Ichikawa, K. and Yao, A. (1976): Two new
genera of Mesozoic cyrtoid radiolarians
from Japan. in Takayanagi, Y. and Saito,
T. (eds.) Progress in Micropaleontology;
Micropaleontology Press, p. 110-117, incl.
pIs. 1 and 2.
Igo, H. (1979): Conodont biostratigraphy andrestudy of geological structure at the easternpart of the Mino Belt. Prof. M. Kanuma
Commemoration Volume, Biostratigraphy ofPermian and Triassic Conodonts and Holothurian Sclerites in Japan, p. 103-113. [inJapanese]--and Koike, T. (1975): Geological age ofthe Kamiaso conglomerate and new occurrence of Triassic conodonts in Mino moun-tains. J. Geol. Soc. Japan, vol. 81, p. 197-198. [in Japanese]Kano, K. (1979): Giant Deckenpaket and olistostrome in the eastern Mino district, central
Japan. J. Fac. Sci., Univ. Tokyo, Sec. II,
vol. 20, p. 31-59, pIs. 5-7.
Kido, S. (1982): Occurrence of Triassic chert
and Jurassic siliceous shale at Kamiaso, Gifu
Prefecture, central Japan. News of Osaka
Micropaleontologists, Spec. Vol. no. 5,
p. 135-151, incl. pIs. 1-5. [in Japanesewith English abstract]- - , Kawaguchi, 1., Adachi, M. and Mizutani,S. (1982): On the Dictyomitrella(?) kamoensis - Pantanellium fovea tum Assemblage
in the Mino area, central Japan. Ibid., Spec.
Vol. no. 5, p. 195-210, incl. pIs. 1-6. [inJapanese with English abstract]
Koike, T., Igo, H., Takizawa, S. and Kinoshita,
T. (1971): Contribution to the geologicalhistory of the Japanese Islands by theconodont biosjratigraphy. Part II. J. Geol.
Soc. Japan, vol. 77, p. 165-168.
Kojima, S. (1982): Some Jurassic, Triassic andPermian radiolarians from the eastern partof Takayama City, central Japan. News ofOsaka Micropaleontologists, Spec. Vol. no.
5, p. 81-91, incl. pIs. 1-4. [in Japanesewith English abstract]
Matsuda, T. and Isozaki, Y. (1982): Radiolarians
around the Triassic-Jurassic boundary fromthe bedded chert in the Kamiaso area,
southwest Japan. Ibid., Spec. Vol. no. 5, p.
93-101, incl. pIs. 1-3. [in Japanese withEnglish abstract]

Explanation of Plate 52 (marker = 50 microns)
Figs. 1-3. Pantanellium fovea tum Mizutani and Kido n. sp.
1,16400/334.
2,16185/535.
3,12765/400.
Figs.4a-4d. Pachyoncus kamiasoensis Mizutani and Kido, n. sp. (4a-4d, holotype)4a, 22789/542.
4b, 22792/542; lower part of fig. 4a.
4c, 22791/542. }.
4d, 22790/542.
stereophotographs of cortIcal shell of fig. 4a.

MIZUTANI and KIDO : Middle Jurassic Radiolarians

Plate 52

261

772. Middle Jurassic Radiolarians
Mizu tani, S. (1964): Superficial folding of the
Paleozoic system of central Japan. J. Earth
Sci., Nagoya Uniu., vol. 12, p. 17-83,
pis. 1-5.
--(1981): A Jurassic formation in the HidaKanayama area, central Japan. Bull. Mizunami Fossil Museum, no. 8, p. 147-190,
pIs. 55-64. [in Japanese with English
abstract and description]- - , Hattori, I., Adachi, M., Wakita, K., Okamura, Y., Kido, S., Kawaguchi, I. andKojima, S. (1981): Jurassic formations in
the Mino area, central Japan. Proc. Japan
Acad., vol. 57, Ser. B, p. 194-199.
--and Koike, T. (1982): Radiolarians in theJurassic siliceous shale and in the Triassic
bedded chert of Unuma, Kagamigahara
City, Gifu Prefecture, central Japan. Newsof Osaka Micropaleontologists, Spec. Vol.
no. 5, p. 117-134, incl. pIs. 1-5. [inJapanese with English abstract]
Miiller, J. (1858): Uber die Organisation und
die Lebenserscheinungen der Thalassicollen,
Polycystinen und Acanthometren. A bh.
Konigl. Akad. Wiss. Berlin, p. 1-62, pIs.
1-11.
Nakaseko, K. and Nishimura, A. (1979): Upper
Triassic Radiolaria from Southwest Japan.
Sci. Rept. Coil. Gen. Educ., Osaka Uniu.,
vol. 28, p. 61-109, incl. pIs. 1-12.
Owada, K. and Saka, Y. (1982): Preliminary
note on the Paleozoic and the Mesozoic
formations in the Chichibu Belt, Okutama
district, Kwanto Mountains, Japan. Newsof Osaka Micropaleontologists, Spec. Vol.
no. 5, p. 67-80, incl. pIs. 1 and 2.. [inJapanese with English abstract]
Pessagno, E. A., Jr. (1977): Upper Jurassic
Radiolaria and radiolarian biostratigraphyof the California Coast Ranges. Micropaleontology, vol. 23, p. 56-113, incl. pIs. 1-12.
--and Blome, C. D. (1980): Upper Triassic andGifu Jl$(til..

Hisuikyo m*~,Jurassic Pantanelliinae from California,
Oregon and British Columbia. Ibid., vol. 26,
p. 225-273, incl. pIs. I-II.
--and Whalen, P. A. (1982): Lower andMiddle Jurassic Radiolaria (multicyrtid Nassellariina) from California, east-central
Oregon and the Queen Charlotte Islands,
B.C. Ibid., vol. 28, p. 111-169, incl. pIs.
1-13.
Riedel, W. R. (1967): Subclass Radiolaria, in
Harland, W. G. et al. (ed.), The Fossil
Record; Geol. Soc. London, p. 291-298.
Shibata, K. and Mizutani, S. (1982): Isotopic
ages of Jurassic siliceous shale and Triassic
bedded chert in Unuma, central Japan.
Geochem. J., vol. 16, p. 213-223.
Wakita, K. (1982): Jurassic radiolarians fromKuzuryu-ko - Gujo-hachiman area. News ofOsaka Micropaleontologists, Spec. Vol. no.
5, p. 153-171, incl. pIs. 1-7. [in Japanesewith English abstract]
Yao, A. (1972): Radiolarian fauna fr~m theMino Belt in the northern part of the Inuyama area, central Japan. Part I: Spong-usaturnalids. J. Geosci., Osaka City Uniu., vol.
15, p. 21-64, pis. 1-11.
--(1979): Radiolarian fauna from the Mino
Belt in the northern part of the Inuyama
area, central Japan. Part II: Nassellaria I.
J. Geosci., Osaka City Uniu., vol. 22, p. 2172,pls.1-12.
- - , Matsuda, T. and Isozaki, Y. (1980): Triassic
and Jurassic radiolarians from the Inuyama
area, central Japan. Ibid., vol. 23, p. 135154, pIs. 1-3.
- - , Matsuoka, A. and Nakatani, T. (1982):
Triassic and Jurassic radiolarian assemblages
in Southwest Japan. News of Osaka Micropaleontologists, Spec. Vol. no. 5, p. 27-43,
incl. pIs. 1-4. [in Japanese with English
abstract]

Kamiaso J:1f!;1=,.

Kamo 1)n~.

Kashibara f-lfW-,

Mino ~tl. .---

Shinjiro MIZUTANI and Satoshi KIDO

262

Ji!j(:Jj!9iU:1f!;:t0)1l'NJl:oEl-q:.0) y "- 7*,cq:.j(Jj:ald&;I;: d~Jj!!Ji!<1JQ~W-l:::*1I1T 1:ffl;:tO)~~)llri}
H.::.31±1-t07-1' - r, l1'NJl:oEl-:}';J::lfji:P;'fi' Jl:oEl-/J>i?tJ:0=::rt· y,,- 7*~Wo!J1tL, ;'fi;f§P.l/
lf~tf.Jf'::', i t.:, :tP.l/If$B~f'::'f9.l:ilt U':o 2: O)? ,!?, l1'NJl:oEl-v;::'ft Unuma echinatus'flUU:
Dictyomitrella (?) kamoensis-Pantanellium foveatum U~O) 2 t&/tl(;I;U~/J'~co i?n 0.
:llI~ i? ft, f&t;'~f~~-t 0 t71!l&f1fi~~lf, 4 fl1j0)1ldlX;I; (? '!? 3 f1fift~f!n)~8ctt U-':o 2: 0)

5 t:::> Dictyomitrella (?) kamoensis n. sp. c Pantanellium foveatum n. sp. fH~~fi-c'
El *0) ~:ft!H'::' i ~ <iil±l-j 00 Pachyonclls kamiasoensis n. sp. It1:8CO) 2 f1fi c;J:l<f?

;li; I),

ftl!O):ttl!~-c-ait-':*H!f~n"n't.n'o 2:0) Dictyomitrella (?) kamoensis-Panta.
nellium foveatum U~f'::' ~i 0 Ristola (?) turpicula ft, ~t** v ~. /,1'110) Snowshoe@ (Bathonian 1:$) J:: fJ ii-t 0 2: /J'~D i?n -n, 0 •*~f$7ElN~ •It'~-to/J',

.

'

n

c

*p

..

Explanation of Plate 53 (marker = 50 microns)
Fig. 1. Pachyoncus kamiasoensis Mizutani and Kido, n. sp. (la-1e, paratype)lab' 2 227 86// 324.} stereophotographs of cortical shell of fig. 1c.
1 ,2 7 8 7 3 24.
1e, 22785/324.
Figs. 2-4. Dictyomitrella(?) kamoensis Mizutani and Kido, n. sp. (2, holotype; 3, paratype)2,12675/396.
3,11643/391.
4a, 11670/391.
4b, 11671/391 ; lower part of fig. 4a.
Fig. 5. Ristola(?) turpicula Pessagno and Whalen.
5, 12214/334.

MIZUTANI and KIDO : Middle Jurassic Radiolarians

Plate 53'

.1 .• ,

.'

..-

'

1'"

.''-.

263
PROCEEDINGS OF THE PALAEONTOLOGICALSOCIETY OF J AP AN

B *ti1=.¥J.}'¥:~m132@]{7IJ~t.J; 1983:q::10}3 23 B Ie:,1m*:7,:~z.~JiI;)<!: L-clJtlfr~;/ct-: (~~*,'51i;)o• ~~~t.J'l?jliHe U-:",,'l--,qeaz~~ .. 151tNt~~~~~R~~.*m*~~~~~R~~5*(7)1'&~~ft15.1ii1f.................. :f'~1Nil~*~tB*(7).:pWl.:p~t!t (7) ~.ilftii~ft:P:2V~jjjj <!:.:t(7)tl:!;!tA9Jt~ .... iDi~U~ff· fof:lII:i:.F!. •• *1:tJllggl'l~· *lIIiR:¥· jul!Ml:~· triJlli!&:JlB
A new genus of porcelliid gastropod from the
Akiyoshi Limestone Group ' ..... Nishida, T.
~OO!1B7i-j-~f~mJl (7) 1 / '" ') A A <!: .:t(7) £;[i;:........................ B3ftlEZ· W*Ili~::k7:)-~f?,'UilUihLJJI=&J{ (1) -Aptian fauna-,.

· .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ... B3.:p :lij~j.ij B*I::.:t,;~ ~ lltrWl B!JIi:*c =~J{ Hayamina<!:.:t (7) .i£:I±lJijIf .................... :f'~B3 iI'-fB !II!;j:-e Crassostrea (7)::z P =- -I::' -::> l' -C ..... .
· ................. , ........... ' ... i~HII3fP.trr=f ~ (7) =i'X :1)- (7) nlt-;/iH;l]llB nlt y ;( A I::. ":n ' -C ....
· . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. :7,:!IlF Pl.tlt

Eotrematoceras, a new orthocerid from thePermiam Mizuyagadani Formation, Fukuji,
Hida Marginal belt ......... , ........ , .. .
· ..... Niko, S., Nishida, T. and Okimura, Y.
f.:kff15IJ(;{5J1-MTfmJ\1lC7) Schistocerataceae ImH
7 /' -T= T 1 r I::' -::>l '-C .... ~r,,9rff-f- '. j1li'B3N;W;
Late Permian ammonoids from the Kitakami
Massif, Northeast Japan ................. .
· . . . . . . . . . . . . . . . .. Ehiro, M. and Bando, Y.
On the Lower Triassic ammonoids from
Pastun in Kashmir, India ........ Bando, Y.
B !II!*ill1J~ JI~t.J' I? I±l t-: :/ l' ~ ? 'f: ft15 ......

· ................. , . . . .. :'t;-III;'J~M· tft*~-fr
Dipteridaceae (Pteridophyta) from the Upper
Triassic Mine Group in Yamaguchi Prefecture, Japan (1) .................... Naito, G.
j"-JE(7)*JI.i£:C7) Sphenopteris . ......... 1*JiiUltknr;
Paleovegetation and paleoclimate based on
the polIen-lll}alysis of Kurobe·gawa·fan Sub·merged Forest, central Japan ........... ,· ......... , ... , ....... Fuji, N. and Fujii, S.
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Transactions and Proceedings of the PalaeontologicalSociety of Japan
New Series No. 132

December 30, 1983

CONTENTS
TRANSACTIONS
769. NODA, Masayuki: Notes on the so-called Inoceramus japonicus (Bivalvia) from theUpper Cretaceous of Japan .. . . .. . .... .. . ...... . ... . . . . . . . .... 191
770. MATSUMOTO, Tatsuro and MIYAUCHI Toshiya: Cretaceous nautiloids from Hok·kaido-III . . ... .. .. ....... . . . . . ... ... .. . . . . ..... . ... . .... 220
771. FUJI, Norio: Palynological study of 200-meter core samples from Lake Biwa, central
Japan . .... . .. . .. .. ....... . . ... .. ...... ... . . .. .. . . . . .. . 230
772 . MIZUTANI, Shinjiro and Krno, Satoshi: Radiolarians in Middle Jurassic siliceous
shale from Kamiaso, Gifu Prefecture, central Japan . .. .. .. . . .... . .. ... 253
PROCEEDINGS . . . . . .. . . . . . .. .. . . . . . . . . .. .. . .... . . .. . ... ... . .. ... 263