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December 30, 1995

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Trans. Proc. Palaeont. Soc. Japan, N.S., No. 180, pp. 203-207, 1 Fig., December 30, 1995

1

995

1

Genetic variation within a dimorphic species,
Cryptopecten vesiculosus (Bivalvia, Pectinidae)

ISAO SARASHINA
Geological Institute, University of Tokyo, Tokyo 113, Japan
Received 25 March 1994; Revised manuscript accepted 20 October 1995
Abstract. An allozyme analysis of Cryptopecten vesiculosus was conducted to obtain biochemical
evidence to determine whether the two discrete morphologic "phenotypes" represent dimorphism or
two sympatric species. A total of 17 loci were extracted with polyacrylamide gel electrophoresis
from specific tissues of the individuals collected from Sagami Bay, Japan. Of the 17 loci examined,
seven (41.2%) were polymorphic, and avarage heterozygosity per individual was calculated at 0.20,
indicating a high level of genetic variation in this species. The allozyme patterns are not statisticallydifferent between the two "phenotypes", confirming the previous interpretation based on morphologic
and ecologic evidence that the two "phenotypes" represent discontinuous intrapopulational variants.
Key words: Dimorphism, random mating, genetic variation, allozyme, Cryptopecten
Introduction

Cryptopecten vesiculosus (Dunker) is a pectinid species
known from lower sublittoral sandy bottoms of subtropicalto temperate waters of the Northwest Pacific. It first
appeared in the early Pliocene. During the Pliocene andearly Pleistocene populations were monomorphic, butfrom the middle Pleistocene populations always bear two
discrete "phenotypes" characterized by different modes ofshell ornamentation. One phenotype has highly elevatedand generally quadrate radial ribs, while the other has low
and generally rounded radial ribs. They have been called"phenotype Q" and "phenotype R", respectively (Hayami,
1973; 1984).
Color polymorphism is common in molluscs, but the"dimorphism" of C. vesiculosus is unique, because thetwo "phenotypes" can easily be discriminated even in aworn or fragmental specimen owing to the solid nature of
the shell surface ornamentation. "Phenotypic" frequency
can therefore be determined also in fossil samples.
Since this species occurs abundantly in post-early
Miocene strata and present seas, the change of relative
frequency of the two "phenotypes" in time and space was
successfully traced using large population samples(Hayami, 1973,1984).
The morphologic change through geologic time in this
speCies is indeed remarkable and was interpreted as
being the result of acquisition and spread of mutations by
natural selection or random get:letic drift (Hayami, 1973,
1984). Such "phenotypic" substitution without any intermediate forms was further considered as one of thepossible causes for punctuated morphological evolution(Hayami and Ozawa, 1975).
Obviously, the above arguments concerning the evolutionary patterns of C. vesiculosus are based upon theassumption that the two "phenotypes" represent dimorphism within the species. This assumption relied upon
the observations that the two "phenotypes" are strictly
sympatric and have the same reproductive season, andthat no significant difference beteen two "phenotypes"
has been detected in other morphologic characters(Hayami, 1984). It is, however, important to ascertain thegenetic relation between the two "phenotypes" by more
direct methods, because random mating is a fundamental
premise for the discussion of phenotypic substitution.
Crossing experiments are difficult in view of the considerably long life cycle and lower sublittoral habitat of thisspecies. In such a case, electrophoretic analyses ofallozymes may be generally practical and effective.
In this paper, I intend to present a piece of evidence todecide the genetic relation between the two "phenotypes"
based on an electrophoretic survey of allozymes. I also
intend to show the extent of genetic variation in a population of C. vesiculosus.
Material and Methods

Specimens of Cryptopecten vesiculosus analyzed here
were collected on 4th and 8th September 1994 by dredging operation at a locality (about 80 m deep) about 2 km
west of Jogashima Islet, Sagami Bay, central Japan (thesame locality as Sample Jg (1-26) by Hayami, 1984). The
sampling was carried out to coincide with the season of
maximum gonad development expected for this speCies,

Isao Sarashina

204
Table 1.

Buffer and tissue combinations in this analysis.

EnzymeAbbreviation

Alcohol dehydrogenase
AmylaseGlucose-6-phosphate dehydrogenase
Glucose-6-phosphate isomerase
Guanine deaminase
Lactate dehydrogenase
Malate dehydrogenase
Octanol dehydrogenase
Peptidase-B
Phosphog Iucom utase
Phosphogluconate dehydrogenase
Superoxide dismutase

ADH
AML
G6PD
GPI
GDA
LDH
MDH
ODH
PEPB
PGM
PGDH
SOD

because gonadal tissues offer a usful source of allozymes.
Specimens were transported alive to the Gelogical
Institute, University of Tokyo, where they were frozen andkept at -80'C until processed for further analysis. An
amount (0.05-0.1 g in wet weight) of either mantle, muscle
or gonadal tissues of each individual was homogenized ina volume of 0.06 ml of grinding solution (0.01 M Tris, 0.1%(v/v) mercaptoethanol, 0.2% (v/v) glycerol; pH 7.5) usinga hand homogenizer. The homogenates were
centrifuged at 15,000 rpm at 4'C for 5 minutes. The
resulting supernatants were loaded onto vertical 15%
polyacrylamide gels. Electrophoresis was carried out at
4'C for 3-6 hours under a constant voltage of 100 V. Gels
except one for AML were then stained at 37'C following
the methods described by Shimizu and Shimizu (1987) and
Murphy et al. (1990). (Stain for AML: 0.35 M Tris-HCI,
pH 8.0 30 ml; starch 5 g; 10 mg/ml diphosphopyridine
nucleotide 2 ml ; 10 mg/ml 3- [4, 5-dimethyl-2-thiazolyl]
2, 5-diphenyltetrazolium bromide 2 ml ; 4 mg/ml phenazine methosulfate 1 mI.) Table 1 gives the combinationsof buffers and tissues used for the separation of eachenzyme. When multiple loci occur in an enzyme, the lociare numbered in order of decreasing anodal mobility.

Results
Of the 17 loci examined, seven (G6PO-1, G6PO-2, GPI2, LOH, OOH, SOO-1 and SOO-2) in both "phenotype R"
and "phenotype 0" were polymorphic, and the proportionof polymorphic loci (P) was therefore calculated as 0.41.
All of the 17 loci, including the ten monomorphic loci
(AOH, AML, GPH, GOA, MOH-1, MOH-2, PEPB, PGM,
PGOH-1, PGOH-2) could be genetically interpreted. The
results of allozymatic variation observed at each locus are
summarized in Table 2. The examples of elecromorphs
are shown in Figure 1. Heterozygosity at each locus isindicated in Table 3, and the average heterozygosity per
individual was revealed as 0.20. The chi-squares tests

Buffer
0.087M Tris-citrate; pH 9.0
0.087M Tris-citrate; pH 9.0
0.1M Tris-citrate; pH 7.5
0.025M Tris-citrate; pH 7.5
0.025M Tris-citrate; pH 7.5
0.01M Na2 HPO.-citrate; pH 7.0
0.1M Tris-citrate; pH 7.5
0.087M Tris-citrate; pH 9.0
0.045M Tris-citrate; pH 8.6
0.045M Tris-citrate; pH 8.6
0.01M Na2 HPO.-citrate; pH 7.0
0.02M Tris-citrate; pH 7.5

TissueGonad
MuscleMantleGonad
Muscle
Gonad
Gonad
Gonad
Muscle
Gonad
Gonad
Gonad

of goodness of fit indicated that frequencies at each of
the seven loci are consistent with Hardy-Weinberg expectations (P>0.05, Table 2), suggesting that all the individuals of each morphologic "phenotype" belong to a single
randomly mating population.
Chi-squares tests for independence were employed tocompare "phenotype 0" with "phenotype R" based on thedeterminations of allele frequencies at the seven variableloci. Null hypothesis was that no difference in allelicfrequencies exists between "phenotype 0" and"phenotype R". In all the 17 loci, the null hypothesis wasnever rejected at the 95% confidence level; this meansthat no significant genetic difference was observed
between "phenotype 0" and "phenotype R", or that there
is no evidence to support the presence of any reproductive isolation between the two "phenotypes".

Discussion
As mentioned befere, C. vesiculosus has been interpreted as an example of punctuated evolutionary change (atleast in morphology) wihch transpired slowly in a large
population without reproductive isolation. The allozyme
data offer two kinds of information. One is that the two"phenotypes" of C. vesiculosus represent dimorphism
within a species, and this is the assumption of that interpretation. The other is the level of heterozygosity in thispopulation of C. vesiculosus.
It has been believed that there is a positive correlation
between heterozygosities and effective population sizes(Nei,1987). Heterozygosities of the species whose population sizes are very small, for example, Mirounga angustirostris (elephant seal) and Acinonyx jubatus (cheetah)are zero (Bonnell and Selander, 1974; O'Brien et aI.,
1985). Until now, heterozygosities in many species havebeen examined (Nevo, 1978; Nei and Graur, 1984), and inmany species they are smaller than 0.2. Heterozygosity
in a population of C. vesiculosus surveyed in this study (=0.20) is not small as compared with those in other species

995.
Table 2.

Genetic variation within Cryptopecten vesiculosus

205

Genotypic and allelic variation at 17 loci in a natural population of C. vesiculosus. N is the number of individuals.
AlleleGenotype
Locus

Phenotype

N

Q

30
30
60
30
30
60
30
34
64
30
30
60
31
31
62
31
31
62
30
30
60
31
32
63
30
30
60
30
30
60
33
32
65
30
30
60
31
32
63
30
30
60
30
30
60
30
30
60
31
30
61

AA

ADH

AML

R
Total
Q
R
Total

G6PD-1Q

R
Total

G6PD-2

Q

GPI-1

R
Total
Q

R
GPI-2

GDA

LDH

MDH-1

Total
Q
R
Total
Q
R
Total
Q
R
Total
Q

R
Total

MDH-2

Q

R
Total

ODH

Q
R

PEPB

PGM

Total
Q
R
Total
Q

PGDH-1

R
Total
Q
R
Total

PGDH-2

Q

80D-1

R
Total
Q
R

80D-2

Total
Q
R
Total

30
30
60
30
30
60
9
10
19
2
5

7
31
31
62
3
3
6
30
30
60
1
2
3
30
30
60
30
30
60
7
8
15
30
30
60
31
32
63
30
30
60
30
30
60
12
11
23
2
2
4

AB

BB

AC

BC

12
12
24

6
6

2
3

3

12

5

4

7
8
15

10
19

13
14
27

16

10

17

7
17

13
12
25

CD

DD

1
2

6

o
o
o

o

16

12

2

2
2
4

o
2
2

2
2
4

A

60
60
120
60
60
120
32
35
67
12
19
31
62
62
124
19
20
39
60
60
120
11
15
26
60
60
120
60
60
120
30
33
63
60
60
120
62
64
126
60
60
120
60
60
120
37
34

5
7

1
2
3

BD

15
14
29

20

33

AD

10

9

21
19
40

9
11

CC

4
4
8

5
2
7

6
3
9

8
10
18

71
11

12
23

B

C

25

3

27

6
9

52
35
34

13

69

20

D

7

43
42
85

51
49

100

36
31
67

23
26
49

8
8
16

12
11
23

31
29
60

Isao Sarashina

206

Table 3. Differences between observed and expected (from Hardy-Weinberg Law) numbers of genotypes tested
for significance using chi-squares comparisons and between gene frequencies of "phenotype R" and "phenotype 0"
tested by the same way. "He" is expected heterozygosity, and "Ho" is observed heterozygosity.
Hardy-Weinberg
Test

Allelic frequency (%)
Locus

Phenotype
A

ADH

Q

R
Total
AML

Q

R
Total
G6PD-1Q

R

Total
G6PD-2

Q

R

Total
GPI-1

Q

GPI-2

R
Total
Q
R
Total

GDA

Q

R

LDH

MDH-1

Total
Q
R
Total
Q

R
Total
MDH-2

Q

ODH

R
Total
Q
R
Total

PEPS

Q

R
Total
PGM

Q

R
Total
PGDH-1Q

R
Total
PGDH-2

Q

R
Total
80D-1

Q

R
Total
80D-2

Q

R
Total

100
100
100
100
100
100
53.3
51.5
52.3
20.0
31.7
25.8
100
100
100
30.6
32.3
31.5
100
100
100
17.7
23.4
20.6
100
100
100
100
100
100
45.5
51.6
48.5
100
100
100
100
100
100
100
100
100
100
100
100
30.6
32.3
31.5
17.7
20.0
18.9

S

c

Q-R
comparison

D

Heterozygosity
structures

He

Ho

o

o
o

o
o
o

o
o
41.7
39.7
40.6
58.3
56.7
57.5

5.0
8.8
7.0

0.50
0.87
1.07
2.55
4.16
6.69

21.7
11.6
16.7

69.4
67.7
68.5

0.01
0.03
0.01

82.3
76.6
79.4

0.00
0.06
0.06

7.81
7.81
7.81
7.81
7.81
7.81

3.84
3.84
3.84

3.84
3.84
3.84

0.71

3.40

0.04

0.62

5.99

5.99

3.84

3.84

0.53
0.57
0.56
0.57
0.57
0.57

0.02
0.13
0.02

3.84
3.84
3.84

0.49

3.84

o

o

o
o

0.43
0.44
0.43

0.42
0.45
0.44

o
o

o

o

o

0.29
0.36
0.33

0.29
0.34
0.32

o
o
o
o

o

o
o
o
o
o
o

0.50
0.50
0.50

0.48
0.53
0.51

o

o

o

o
o

o

o
o

o

19.4
18.3
18.9

3.84
3.84
3.84
12.59
12.59
12.59

0.43

0.44
0.31

3.84

monomer

dimer

dimer

o

o
o
0.42
0.45

monomer

0.44

7.81

0.50
0.54

Average heterozygosity per individual =

0.21

0.20

0.12

monomer

o
o
o
o

0.43
0.66
0.68
0.67

50.0
48.3
49.1

monomer

o

o
o
o

o
o
o
o
0.01
0.03
0.01
4.48
5.97
6.57

0.50
0.53
0.52
0.60
0.50
0.55

o

o

69.4
67.7
68.5
12.9
13.3
13.1

o

o

o
54.5
48.4
51.5

o
o
o

0.58

monomer

995.

Genetic variation within Cryptopecten vesiculosus

207

morphologic variation is still obscure. Consequently, theinterpretation that phenotypic substitution results from theaccumulation of a sigle mutant gene still remains tentative, and it is a problem awaiting solution whether theaccumulation was driven by natural selection or random
genetic drift (or by any other causes). Further genetic
investigations are required, and such studies would greatly contribute to the development of evolutionary theory.

A.

(. 1

Acknowledgments\

AA AB AB BB BB AB
B.

I am grateful to Professor Itaru Hayami (Kanagawa
Univ.), Professor Kazushige Tanabe (Univ. Tokyo), and Dr.
Kazuyoshi Endo (Univ. Tokyo) for their guidance in thecourse of the study and critical reading of the manuscript.
Professor Tadahiro Asami (Tachikawa Jun. Col.) kindly
provided me with helpful advice in allozyme analysis. I
also wish to thank colleagues at the Paleobiological
Laboratory of the University of Tokyo for their fruitful
discussion and assistance in collecting the material.

References cited

AC DD BD BD DD CD
C.

AA AA AA AA AA AA
Figure 1. Examples of three types of enzyme banding
patterns in C. vesiculosus.
A : Polymorphic locus of dimer (This example is ODH).
Homozygotes are indicated by one band and heterozygotes
by three. B: Polymorphic locus of monomer (This example
is SOD - 2). Homozygotes are indicated by one band andheterozygotes by two. C : Monomorphic locus (This example is MDH). Two loci are indicated. Upper bands represent MDH -1 and lower bands represent MDH - 2.

hitherto investigated.
From this study it becomes clear that the two
phenotypes of C. vesiculosus represent a dimorphism.
However, the genetic background of this discontinous

Bonnell , M.L. and Selander, RK, 1974 : Elephant seals :genetic variation and near extinction. Science, vol.
184, p. 908- 909.
Hayami, I., 1973 : Discontinuous variation in an evolutionary species, Cryptopecten vesiculosus , from Japan.
Journal of Paleontology, vol. 47, no. 3, p. 401 - 420.
Hayami, I., 1984 : Natural history and evolution of
Cryptopecten (a Cenozoic- Recent pectinid genus).
The University Museum, The University of Tokyo,
Bulletin, no. 24, p. 1-148.
Hayami , I. and Ozawa, T., 1975: Evolutionary models of
lineage zones. Lethaia, vol. 8, p. 1-14.
Murphy, RW., Sites, JW., Donald, Jr., Buth, G. and Haufler,CH, 1990 : Isozyme electrophoresis, In, Hillis,
D.M. and Moritz, C. , Molecular Systematics , p. 45-126.
Sinauer Associates, Inc., Sunderland, Massachusetts.
Nei, M., 1987: Molecular Evolutionary Genetics. p.176207. Columbia Univ. Press, New York.
Nei, M. and Graur, D., 1984: Extent of protein polymorphism and the neutral mutation theory. Evolutionary
Biology, vol. 17, p. 73- 118.
Nevo, E., 1978: Genetic variation in natural populations :patterns and theory. Theoretical Population Biology,
vol. 13, p. 121-177.
O'Brien, S.J., Roelke, ME, Marker, L. , Newman, A.,
Winkler, CA, Meltzer, D., Colly, L., Evermann, J.F.,
Bush, M. and Wildt, D.E., 1985 : Genetic basis for
species vulnerability in the cheetah. Science, vol.
227, p. 1428-1434.
Shimizu, N. and Shim izu, Y., 1987 : Gene mapping on
chromosomes by hybrid cells. In, Muramatsu, M. etal., Gene Research Methods 3, p.261 - 280. Tokyo
Kagaku Doujin Book Co. (in Japanese)Trans. Proc. Palaeont. Soc. Japan, N.S., No. 180, pp. 208-225, 12 Figs., December 30, 1995

Intrageneric variation and temporal change in theinternal skeletal structure of plagiacanthids(Radiolaria) from Hokkaido, Japan
SAlOSHI FUNAKAWA
Department of Geosciences, Faculty of Science, Osaka City University, 3-3-138, Sugimoto-cho, Sumiyoshi-ku, Osaka,
558 Japan
Received 23 January 1995; Revised manuscript accepted 14 August 1995
Abstract. From the Kawakami Group (the Upper Oligocene to Lower Miocene) of eastern Hokkaido,
five new species of Clathromitrinae, including three of Corythomelissa, one of Euscenarium and oneof Lithomelissa, are described, placing emphasis on their internal skeletal structure. In addition, one
species of Clathromitrinae from the Taiki Formation (the Upper Miocene) of eastern Hokkaido is also
examined. Some intraspecific and intrageneric variations are recognized in the internal skeletal
structure of Corythomelissa.
The intrageneric variations have three tendencies over time: (1) the prolongation of L-Rd; (2)the rising of connecting archers on the dorsal side of the shell; (3) the decline of A'. These
intrageneric variations show a general trend through Late Oligocene to Late Miocene time which
represents the evolutionary lineage of Corythomelissa.
Key words: Late Oligocene to Late Miocene, Plagiacanthidae, internal skeletal structure, temporalchange, evolutionary lineage

Introduction
Evolutionary lineages of Cenozoic radiolarians havebeen examined by many investigators (e.g. Riedel and
Sanfilippo, 1970,1971 ; Moore, 1972; Foreman, 1973;
Sanfilippo and Riedel, 1973,1982; GoII, 1979; Lazarus etal., 1985; Sanfilippo, 1990) mainly through materials provided by the Deep Sea Drilling Project. Recognition ofthese lineages was based mainly on temporal changes inexternal structures of radiolarian shells. Concerning thefamily Plagiacanthidae, Goll (1979) determined the evolution of the genus Callimitra based on the morphologicalchange of external shells through time. It was revealed
by some authors (e.g. Swanberg and BjcPrklund, 1987;
Nishimura, 1990) that the internal skeletal structure ofNassellaria is formed during early ontogeny. Although
the value of internal skeletal structures for nassellariantaxonomy has been demonstrated by many investigators(Riedel, 1967,1971; Petrushevskaya, 1971a, 1971b, 1975,1981 ; Takemura, 1986; Nishimura, 1990; Sugiyama,
1993,1994), the temporal changes of these structures
have not been studied yet.
It is easy to observe the internal skeletal structure ofplagiacanthids because most internal skeletal elements
are not hidden within the shell. The external skeletons

are highly varied, with their basic external morphologies
usually depending on the internal skeletal structures(Funakawa, 1994). Therefore, to investigate temporalchanges in their internal skeletal structures is a suitable
way to clarify the evolution of some plagiacanthids.
In this paper, five new species of the Clathromitrinae
are described from Upper Oligocene to Lower Miocene
strata putting special emphasis on their internal skeletal
structures. In addition, the internal skeletal structure of
one species of Corythomelissa from Upper Miocene strata
is examined. Detailed examinations of internal skeletal
structures of the above-mentioned species show intergeneric variations in their internal skeletal structures
occurring within the stated time interval. The author
proposes the evolutionary trends of four species of Corythomelissa based on this temporal change in their internal skeletal structures.
Geological setting and materials
The Kawakami Group (Mitani et al., 1959) is distributedin Hombetsu, Morawan and Kamiashoro regions, eastern
Hokkaido, Japan (Figure 1). Along the Morawan Riverroute, the Kawakami Group is well exposed (Figure 2) andis subdivided into three formations, the Hombetsuzawa,

996.

Temporal change of plagiacanthids (Radiolaria)

209

Sea ofOkhotsk

Hidaramata·sawa River

Pacific
Ocean

A

1 Km

r

c

Figure 1. Index maps. (A) Northeast Japan around Hokkaido. Arrow points to Toyokoro Hills region(Funakawa,1994). (8) Distribution of the Upper Oligocene to Lower Miocene sediments in eastern Hokkaido(after Matsui and Ganzawa, 1987). (C) River system around Morawan River.

Morawan and Kiroro Formations in ascending order (Inoueand Suzuki, 1962). The Hombetsuzawa and Morawan
Formations are characterized by numerous biosiliceous
layers. The Morawan Formation is subdivided into four
members; the lower platy shale, the Kamirawan Sandstone, the middle hard shale and the upper tuffaceous
mudstone members. The Kiroro Formation is characterized by sandstone and non-siliceous siltstone, and is
subdivided into two members; the lower sandstone andthe upper siltstone members. Calcareous nodules yielding well preserved radiolarians are contained in thebiosiliceous layers of the Morawan Formation and siltstone layers of the Kiroro Formation.
The age of the Kawakami Group is based on a combination of radiometric, fission track and biostratigraphicaldata (Figure 3). Matsui and Ganzawa (1987) presented
chronological data by K-Ar and fission track dating.
Saito et a/. (1988) reported Late Oligocene diatoms andradiolarians from the lower platy shale member of theMorawan Formation. From the upper siltstone member ofthe Kiroro Formation, a diatom species, Tha/assiosira
fraga, occurs while Actinocyclus ingens is absent (Ariga,
pers. comm.). This fact indicates that the age of theupper part of this member is between 19.5 Ma and 16.8 Ma(Akiba, 1986). These data indicate that the KawakamiGroup was deposited during Late Oligocene to Early
Miocene time.
In this study, seven calcareous nodule samples fromfour horizons are examined. These horizons are shownin Figure 3.
In addition to the above-mentioned samples, the author
examined diatomaceous siltstone samples from the Upper
Miocene Taiki Formation (Yamaguchi and Satoh, 1989;
Yamagishi et a/., 1990). These samples were collectedalong the Oikamanai River and Noyaushi River routes(Funakawa, 1993; 1994) in the Toyokoro Hills region,
eastern Hokkaido (Figure 1). Localities of radiolariansamples are given by Funakawa (1993,1994). All samples are included within the Upper Miocene interval fromthe Oenticulopsis dimorpha Zone through Tha/assionema
schraderi Zone of Koizumi (1985).
Depository of type specimens is in the Department ofGeosciences, Faculty of Science, Osaka City University.
Notes for terminology of internal skeletal structure
Most skeletal terms follow Petrushevskaya (1968) andDumitrica (1991): MB (median-bar), A (apical spine), D(dorsal spine), V (ventral spine), L (right and left lateralspines) and I (right and left secondary lateral spines);notation of connecting arch is a combination of two
abbreviations of internal elements connecting together(i.e. AL is an arch connecting A and L, D-AL is an archconnecting D and AL). Following Funakawa (1995), several internal spicules, A, V, D and two L form several
horns, feet and ribs and these outside skeletal elements
are the prolongations of these internal skeletal elements:
A sometimes forms an apical rib in the shell wall and an

Satoshi Funakawa

210

MORA WAN{'
Hidarimata-sawa River

1 km
Rawan-gawa River

Klroro Formation

[

,--,

mudstone member

I

Km '

IKb J

sandstone member
upper tuffaceous mudstone member

Mu :
! Mm
,~ Mk

syncline
anticline

I~'-,-'~

Morawan Formation [ middle hard shale member
Kamirawan sandstone member

1,Fllillj

lower platy shale member

Hombetsuzawa Formation

fault

X
k

------\

strike and dip

Figure 2. Sample localities along Morawan River Route. Stratigraphy and geological structure are basedon Inoue and Suzuki (1962). Star indicates the sample locality of K-Ar dating reported by Matsui and Ganzawa(1987).

-------------1-..
3:··-Km::-4

1- 16.8 Ma

MW-125, -120, -118

_ _ _ _ _ _ _ _ _ _...L._ _19.5 MaKb

r--:-...............,.f"IIIt- - - - - - -23.8±2.0 Ma (F.T.) 1

90081402·"···.··M~~~-90-0-81-3-06-27.4±1.5 Ma (K-Ar)
90081501,90081302- - - - - -29.2±3.3 Ma (F.T.) 2

Figure 3. Simplified stratigraphic column with horizons of radiolarian samples. Abbreviations are the sameas those in Figure 2. Potassium argon (K-Ar) and Fission
Track (F.T.) ages are from Matsui and Ganzawa (1987).
Arrow with solid line shows the datum from Morawan River
Route. Arrows with dotted lines show data from otherregions than Morawan. 1: Ponki region, the base of
Tsubetsu Formation correlated to the base of the Kiroro
Formation. 2: Hombetsu region, base of the Hombetsuzawa Formation. Diatom occurrences are provided by
Ariga (pers. comm.); 3: Thalassiosira fraga, 4: Actinocyclus ingens. The first appearance datums of these two
diatoms are based on Akiba (1986).

996.

Temporal change of plagiacanthids (Radiolaria)

211

apical horn

A' and D----//

dorsal rib

/

foot

/

1

/

2

3

Figure 4. Schematic illustrations of internal skeletal structure of Corythomelissa. 1: Internal skeletal
structure of left lateral view. 2: Subdivision of two segments with internal skeletal structure. 3 : internal
skeletal structure of apical view. Stars indicate the branches of D and L, and other abbreviations are explainedin the text.
1 and 3 : Grey lines show internal spicules and thick black lines do connecting arches. 2 : Thick lines
show internal spicules (white) and their prolongations in and outside the shell wall (black). Weak lines showconnecting arches inside the shell (white) and in the shell wall (black). Broken line shows outline of shell.
Dark grey part indicates the first segment and light grey part does the second segment.

apical horn outside the shell; V sometimes forms aventral rib in the shell wall and a ventral horn outside theshell; 0 forms a dorsal rib in the shell wall and a footoutside the shell ; two L form two lateral ribs in the shellwall and two feet outside the shell. A' was defined by
Sugiyama (1993) and is applied for the skeleton extending
dorsally from A near the junction of A and AL. L- Rd was
defined by Funakawa (1995) and applied to the part of AL
between L and the junction of AL and AL- AL or D- AL(Funakawa, 1995, Figure 5). A segmentation such as
cephal is, thorax, abdomen and post- abdominal segments
is generally used in Nassellaria. Because someplagiacanthids have no or indistinct collar stricture (Funakawa, 1994; 1995), this segmentation is unsuitable fordetailed descriptions in this family. Hence the segmental
concept follows Funakawa (1994). First segment is distinguished from second segment by one to three pairs ofconnecting arches and some branches of internal
spicules (Figure 4).
Taxonomic descriptions

Order Polycystina Ehrenberg, 1838,
emend. Riedel, 1967
Suborder Nassellaria Ehrenberg, 1875
Family Plagiacanthidae Hertwing, 1879, emend.
Petrushevskaya, 1971a
Subfamily Clathromitrinae Petrushevskaya, 1971b
Remarks .-Sugiyama (1994) included this subfamily inthe family Sethophormidae Haeckel, 1881. An emended
diagnosis of Sethophormidae presented by Sugiyama(1994) is that A, 0 and two L have one verticil of threebranches without exception. Most speCies of this sub-family have these branches, however, some species
described in this paper lack some of the branches.
Therefore the author uses this subfamily provisionally forthe following three genera in the sense of Petrushevskaya(1971a). More examinations of internal and external
skeletal structure are needed to establish the taxonomy offamily - or subfamily- level.
Genus Corythomelissa Campbell, 1951 , sensu
Petrushevskaya, 1975
Type species. - Lithomelissa corythium Ehrenberg,
1873.
Remarks .- Composition of internal skeletal structure is
as described by Funakawa (1994) except for arches located on dorsal side of shell. A and V form apical andventral horns outside the shell wall respectively, andnever lie in shell wall as apical or ventral ribs. 0 and two
L are well developed as lateral and dorsal ribs in shell wallof second segment and prolong to become three feetoutside the shell. L- R by Sugiyama (1993) is absent.
Length of L- Rd is variable. Junction of A and AL is
located inside the shell wall. 0 has a pair of branches
which connect usually to right and left D- AL respectively
when D- AL is present. L has a pair of indistinct
branches which usually connect to VL and D- AL respectively. This genus has complicated internal skeletal
structure and the fine internal skeletal structures are hard
to reflect the external morphology.
The Late Miocene speCies , Corythomeiissa sp. (C.
horrida by Funakawa, 1994) has one AL- AL on dorsal sideof shell but three speCies described below from the Upper
Oligocene to the Lower Miocene have two D- AL insteadof one AL- AL. In this paper, these four speCies that haveSatoshi Funakawa

212

different internal skeletal structures are included in thegenus Corythomelissa because they are related
phylogenetically to each other, as described in the dis~cuss ion. Although the external morphology of this genus
resembles several genera of Paleogene Clathromitrinae (e.
g. Spongomelissa and Tripodiscium), phylogenetic relations between them are unclear because the internal
skeletal structures of most species of Paleogene Clathromitrinae have not been clarified sufficiently. A schematic illustration of internal skeletal structure of the following three species is shown in Figure 4.

Corythomelissa omoprominentia sp. nov.
Figures 5- 1a- 2bType specimens. - Holotype, OCUCR- 0035: Paratype,
OCUCR- 0036.
Description. - Shell is composed of two segments.
First segment is subspherical with an apical horn. Apicalhorn is three- bladed, approximately equal in length toheight of first segment. External surface of first segment
is thorny. Pores in first segment are circular to subcircular and irregularly distributed . In some specimens,
both D- AL and VL are indistinct and incomplete (Figure 5-1b). Strictures between two segments are indistinct
because of a thickened shell wall with numerous thorns .
Ventral horn is three- bladed, extends laterally and isshorter than apical horn. L- Rd is long. Two branches
arise from D and connect to dorsal side end of D- AL.
Two branches arise from L ; ventral one connects to VL
and dorsal one, usually indistinct, to AL or D- AL. D- AL
diverges from AL where AL separates from internal surface of shell wall. A' is present in most speCimens anddiverges from A at a higher horizon than the junction of A
and AL (Figures 5-1c, - 2b). Most internal spicules are
circular in section except for their external parts, such as
horns and feet. Axial projections are distinct as somedownwardly directed appendages. Second segment isoblate spherical at side view and subdivided into upperand lower parts by a distinct shoulder. The upper parthas distinct lateral and dorsal ribs. External surface of
second segment is thorny. Three feet are three- bladed
and approximately equal in length to apical horn, extending obliquely downward at the shoulder of second segment. Pores in second segment are circular to subcircular and irregularly distributed. Distal aperture of second segment is sometimes closed by porous plate.
Dimensions (in ,um}.- Measurements are based on 14
mature specimens. Length of apical horn, 49- 60 (aver-Figure 5. 1a- 2b : Corythomelissa omoprominentia Funakawa sp. nov. 1a- c: OCUCR - 36, MW-125, paratype. 1a: Right lateral view; Black arrow points to right L. 1b: Basal view ; White arrow points to indistinct
left L, black one to left branch of D. 1c : Enlargement of basal view ; Black arrow points to A' ? 2a - b :OCUCR- 35, MW-125, holotype. 2a : Left lateral view ; White arrow points to left L. 2b: Basal view ; White
arrow points to a dorsal branch of left L. Scale bars : 1a and 2a = 100 J1 m; 1b and 2b = 50 J1 m ; 1c = 20 fl m.

996. Temporal change of plagiacanthids (Radiolaria)
age is 53) : Length of ventral horn, 27- 48 (37). Outside
diameter of first segment (not including ventral horn), 5793 (72) : Outside diameter of second segment (not including feet), 128-160 (143). Inside width between two AL, 51 70 (59) : Inside depth between ends of D and V, 63- 90(72). Height of first segment (not including apical horn),
38- 53 (47). Total height of shell (not including feet and213

apical horn), 90-139 (120).
Remarks .- This species is distinguished from Corythomeiissa horrida Petrushevskaya by a distinct shoulder on
second segment. This species is distinguished from
Euscenarium sp. aft. E. tricoipium of Funakawa (1994) by
the presence of two D- AL and a distinct shoulder on
second segment.

Figure 6. 1a- 2c : Corythomelissa pachyostraca Funakawa sp. nov. 1a- c : OCUCR- 37, 90081306,
holotype. 1a : Right lateral view. 1b : Basal view ; White arrows point to left branch of D and dorsal branchof left L. 1c : Enlargement of basal view; White arrow points to left branch of D. 1d : Enlargement of basal
view ; Black arrow points to A' . 2a- c: OCUCR- 38, 90081306, paratype. 2a : Right lateral view ; Arrow 1
points to the stricture along right AL, 2 to the stricture along right DL. 2b : Basal view ; White arrows point
to right and left AL, black ones to right and left branches of D. 2c : Enlargement of basal view ; Arrow 1 points
to A and 2 to A' . Scale bars: 1a and 2a = 100 11m ; 1b and 2b = 50 11 m; 1c, 1d and 2c = 20 11 m.

Satoshi Funakawa

214

Etym%gy.- The specific name means "distinct shoulder" in Latin.
Occurrences.-MW-125, -120 and -118. Rare to few.
Stratigraphie notes.-Lower Miocene.
Corythomelissa pachyostraca sp. nov.
Figures 6-1a-2c

Type specimen.-Holotype, OCUCR-0037: Paratype,
OCUCR-38.
Description.-Shell is composed of two segments.
External surface of shell is spineless. First segment is
subspherical with an apical horn. Apical horn is robust,
three-bladed and twice to three times as long as height offirst segment. First segment of some specimens has athickened shell wall with very few and small pores.
Pores in first segment are circular to subcircular, verysmall in size and irregularly distributed. Strictures along
AL and D-AL are indistinct in some specimens. Ventral
horn is three-bladed and much shorter than apical horn,extending laterally to obliquely upward. Length of L-Rd
is variable but is usually very short. In most specimens,
right and left L-Rd show different lengths. Some specimens have right or left DL instead of D-AL and L-Rd isabsent in this case (Figures 6-1c, -2b). Two branches
arise from D and connect to dorsal side end of D-AL.
Two branches arise from L; ventral one connects to VL
and dorsal one, sometimes indistinct, to AL or D-AL. DAL diverges from AL where AL meets the internal surfaceof shell wall. A' is distinct and spiny. Two Land Dare
three-bladed in section for most part. MB, basal part of
V and lower part of A are circular in section. Axial
projection is distinct. Second segment is hemisphericalwith three lateral and dorsal ribs. Three feet are threebladed and approximately equal in length to apical horn.
Feet extend obliquely downward from the lower part ofsecond segment. Pores in second segment are circular
to subcircular, larger than those in first segment andirregularly distributed. Distal aperture of second segment
is fully open without teeth.
Dimensions (in ,um).-Measurements are based on 62
mature specimens. Length of apical horn, 51-123 (84):Length of ventral horn, 24-67 (40). Outside diameter offirst segment (not including ventral horn), 58-117 (79):
Outside diameter of second segment (not including feet),
83-160 (123). Inside width between two AL, 46-83 (63):Inside depth between ends of D and V, 45-93 (69).
Height of first segment (not including apical horn), 30-63(46). Total height of shell (not including feet and apicalhorn), 62-147 (105).
Remarks.- The variable length of L-Rd and the presence of one DL instead of D-AL in some specimens are
considered intraspecific variation in this species because
it seems that the length of L-Rd changes gradually. This
species is distinguished from Corythomelissa horrida
Petrushevskaya and C. omoprominentia sp. nov. by short
L-Rd and a first segment with a spineless and thickened
shell wall. This species is distinguished from Euscenarium sp. aff. E. trico/pium of Funakawa (1994) by thepresence of L-Rd.
Etym%gy.- The specific name means "thick shell" in
Latin.
Occurrences.-90081302, 90081501, 90081306 and
90081402. Few to common (90081306 and 90081402) tovery rare (90081302 and 90081501).
Stratigraphic notes. -Upper Oligocene.

Corythome!issa spinosa sp. nov.
Figures 7-1a-3c

Type specimen.-Holotype, OCUCR-0039: Paratype,
OCUCR-0040, -0041.
Description. -Shell is composed of two segments.
First segment is subspherical with an apical horn. Apicalhorn is stout, three-bladed and twice to three times aslong as height of first segment. Surface of first segment
is thorny. Pores in first segment are small, circular to
subcircular and irregularly distributed. Ventral horn isthree-bladed and shorter than apical horn, extending
laterally to obliquely upward. In some specimens, D-AL
is indistinct (Figure 7 -2b). Strictures between two segments are indistinct because of the thickened shell wallwith numerous thorns. L-Rd is long. Two branches
arise from D and connect to dorsal end of D-AL. Twobranches arise from each L; ventral one connects to VL
and dorsal one, usually indistinct, to AL or D-AL. D-AL
diverges from AL where AL separates from internal surface of shell wall. A' is present in most specimens anddiverges from A at a higher horizon than the junction of A
and AL (Figure 7-1b). Most internal spicules are circular
in section except for their external prolongations, such as
horns and feet. Axial projections are distinct as numerous fine appendages. Second segment is hemispherical.
The upper part of second segment has distinct lateral anddorsal ribs and its external surface is somewhat spiny.
Three feet are three-bladed and their lengths are approxi-

Figure 7. 1a-3c: Corythomelissa spinosa Funakawa sp. nov. 1a-b: OCUCR-39, MW-125, holotype. 1a: Leftlateral view. 1b: Enlargement of basal view; White arrow points to left AL, black one to A' 7. 2a-2c: OCUCR-40,
MW-125, paratype. 2a: Right lateral to ventral view. 2b: Basal view. 2c: Enlargement of basal view. 3a-c:
OCUCR-41, 90081501, paratype. 3a: Right lateral view. 3b: Basal view; Arrows 1 point to right and left D-AL, 2 toright and left AL, 3 to right VL, white one to right branch of D. 3c: Enlargement of basal view; White arrow points to
A. 4a-4c: Corythomelissa sp., Oik-7 (Modified from Funakawa, 1994). 4a: Dorsal view. 4b: Basal view; Arrow 1
point to right and left AL, 2 to AL-AL, 3 to right and left branches of D. 4c: Enlargement of basal view; White arrow
points to AL-AL. Scale bars: 1a,2a and 3a=100.um; 2b, 3b, 4a and 4b=50.um; 1b,2c and 3c=20.um; 4c=10
.urn.

996.

Temporal change of plagiacanthids (Radiolaria)

215

Satoshi Funakawa

216

mately equal to that of apical horn. They extend obliquely downward from middle to lower part of second segment.
Pores in second segment are circular to subcircular, larger
than those of first segment and irregularly distributed.
Distal aperture of second segment is fully open without
teeth.
Dimensions (in ,um).-Measurements are based on 62
mature specimens. Length of apical horn, 51-123 (84):Length of ventral horn, 24-67 (40). Outside diameter offirst segment (not including ventral horn), 58-117 (79):
Outside diameter of second segment (not including feet),
83-160 (123). Inside width between two AL, 46-83 (63):Inside depth between ends of D and V, 45-93 (69).
Height of first segment (not including apical horn), 30-63(46). Total height of shell (not including feet and apicalhorn), 62-147 (105).
Remarks.- This species is distinguished from C. pachyostraca sp. nov. by the thorny wall of first segment.
This species resembles C. horrida but is distinguishedfrom it by the presence of D-AL on the dorsal side of theshell. This species is distinguished from C. omoprominentia sp. nov. by the well developed feet and theopen distal aperture of the second segment.
Etym%gy.- The specific name means "spinose" in
Latin.
Occurrences.-AII samples examined. Few in
90081302 and 90081501, very rare in 90081306 and
90081402 and common in MW-125, -120 and -118. Rareto very rare in Upper Miocene samples, Ny-89, Ny-81,
91092604 and 91092607 (Funakawa, 1993; 1994).
Stratigraphic notes.-Upper Oligocene to Upper
Miocene.

Corythomelissa sp.
Figures 7 -4a-c
Corythomelissa horrida Petrushevskaya: Funakawa, 1994, p.

476, figs. 14, 1a-b.

Remarks.-Shell is composed of two segments. First
segment is hemispherical or cup-shaped, with an apicalhorn. Apical horn is stout, three-bladed and is approximately equal in length to height of first segment. Surfaceof first segment is thorny. Pores in first segment arecircular to subcircular and are irregularly distributed.
Ventral horn is three-bladed and is shorter and narrower
than apical horn, extending laterally to obliquely upward.
AL-AL is indistinct (Figure 7 -4b). Strictures between twosegments are indistinct because of the thickened shellwall with numerous thorns. L-Rd is very long. Twobranches arise from D and connect to shell wall. Twobranches arise from each L: ventral one connects to VL
and dorsal one, usually indistinct, to AL. Two branches,sometimes indistinct, arise from V and connect to VL.
AL-AL diverges from AL where AL separates from internalsurface of shell wall. A' is absent (Figure 7 -4b). Most
internal spicules are circular in section except for theirexternal prolongations, such as horns and feet. Axial
projection is present. Second segment is cup-shaped.

Three feet are three-bladed and their lengths are approximately equal to that of apical horn. They extend obliquely downward from middle to lower part of second segment.
Pores in second segment are circular to subcircular andare irregularly distributed. Distal aperture of second
segment is fully open in most specimens but in somespecimens it tends to be closed by a porous plate.
Although all specimens examined in this study are
Corythome/issa horrida Petrushevskaya of Funakawa(1994), it is questionable to identify this species as C.
horrida because of the different ranges between C. horrida
and Funakawa's (1994) species. C. horrida was described by Petrushevskaya (1975) frQm Antarctic
Oligocene to Miocene deposits. The species was thenreported by several authors: by Goll and Bjq,rklund (1989)
from the Middle to Upper Miocene (Norwegian Sea, ODP
Leg 104); and by Takemura (1992) from the uppermost
Eocene to Upper Oligocene (southern Indian Ocean, ODP
Leg 120). On the other hand, Funakawa's (1994) species
does not occur from either the Upper Oligocene or Lower
Miocene in this study. This fact indicates that Funakawa's (1994) species is different from C. horrida. Therefore, the author renounces Funakawa's (1994) specificidentification of this species· and emends it as Corythome/issa sp.
Dimensions and Occurrences.-Refer to Funakawa,
1994, p.477.
Genus Euscenarium Haeckel, 1887, sensu
Petrushevskaya, 1981

Type species.-Euscenium trico/pium Haeckel, 1887.
Remarks.-Composition of internal skeletal structure is
as described by Funakawa (1994). A and V form apicaland ventral horns outside the shell wall respectively, andnever lie in shell wall as apical or ventral ribs. D and two
L are well developed as lateral and dorsal ribs in shell wallof second segment and prolong to three feet outside theshell. L-R of Sugiyama (1993) and L-Rd are absent. D
has a pair of branches which connect to right and left DL
respectively. L has a pair of branches which connect to
VL and DL respectively. This genus is distinguished from
Corythome/issa by the absence of L-Rd. A schematic
illustration of internal skeletal structure of the following
species is shown in Figure 8.
Euscenarium microcapitalium sp. nov.
Figures 10-1a-2b

Type specimen.-Holotype, OCUCR-0042: Paratype,
OCUCR-0043.
Description.-Shell is composed of two segments.
First segment is hemispherical. Apical horn is threebladed and length is equal to twice the height of first
segment. Ventral horn is three-bladed and shorter thanapical horn. Shell wall of first segment is thickened andusually poreless, with smooth surface. When pores arepresent, they are very small, circular and irregularly dis-

996. Temporal change of plagiacanthids (Radiolaria)

217

D

A
/
/
/

3

Figure 8. Diagrams of internal skeletal structure of Euscenarium microcapitalium Funakawa sp. nov. 1:
Internal skeletal structure of left lateral view. 2: Subdivision of two segments with internal skeletal structure.
3 : Internal skeletal structure of apical view. Dotted lines are indistinct elements. Stars are the branches of
D and L, and other abbreviations are explained in the text.
1 and 3: Grey lines show internal spicules and black lines do connecting arches ; dotted line is indistinct
element. 2: Thick lines show internal spicules (white) and their prolongations in and outside the shell wall
(black). Weak lines show connecting arches inside the shell wall (white) and in the shell wall (black). Broken
line shows outline of shell. Dark grey part indicates the first segment and light grey part the second segment.

tributed. Strictures along AL, VL and DL are shallow.
Junction of A and AL is inside the shell, just below theinternal surface of shell. A' is well developed and goes
down along shell wall and forms indistinct AD. Right andleft branches arise from D and connect to DL. Ventral
and dorsal branches arise from L and are indistinct.
Most internal spicules are circular in section except for
their external prolongations, such as horns and feet.
Axial projection is distinct. Some specimens have one totwo projections on underside of both D and L. Second
segment is oblate spherical to subcylindrical with three
distinct lateral and dorsal ribs. Three feet are long,
three- bladed, and extend obliquely downward. Pores insecond segment are circular to subcircular and larger thanthose of first segment. Distal aperture of second segment is fully open, without teeth .
Dimensions (in J1.m). - Measurements are based on eightmature specimens. Length of apical horn, 31 - 48 (40):Length of ventral horn, 12 (measured on only one specimen). Outside diameter of first segment (not including
ventral horn), 41 - 48 (43) : Outside diameter of second
segment (not including feet), 52 - 64 (57). Inside width
between two DL or AL, 36- 43 (39): Inside depth between
ends of D and V, 37 - 45 (40). Height of first segment (notincluding apical horn), 25- 32 (29). Total height of shell(not including apical horn and feet), 41 - 63 (51).
Remarks .- This speCies is smaller than Euscenarium
tricolpium (Haeckel) and E. joergenseni Dumitrica. It isdistinguished from E. sp. cf. E. tricolpium of Funakawa(1994) by a small first segment and shallow strictures
between the two segments. This speCies has similar
skeletal structures to Corythomelissa pachyostraca sp.

nov. except for the smaller shell and the absence of L- Rd.
Etymology .- The specific name means "small cephalis"in Latin.
Occurrences .- Rare in 90081302,90081501 and
90081306.
Stratigraphic notes. - Upper Oligocene.
Genus Lithomelissa Ehrenberg, 1847, sensu
Petrushevskaya, 1971 b
Type species. - Lithomelissa microptera Ehrenberg,
1854.
Remarks .- Various forms of Clathromitrinae and, perhaps Lophophaeninae, have been placed in this genus.
To properly classify these forms, it is necessary to investigate their internal skeletal structure. The following
species has external skeletal characteristics similar to thetype species, Lithomelissa microptera Ehrenberg, therefore it is provisionally assigned to Lithomelissa in thispaper. A schematic illustration of the internal skeletal
structure of the following species is shown in Figure 9.

Lithomelissa trifolio/ata .sp. nov.
Figures 10- 3a- 4c
Clathrolychnus sp Sugiyama, 1994, pI. 2, fig. 3a- b.
Type specimens. - Holotype , OCUCR - 0044 : Paratype,
OCUCR - 0045.
Description. - Shell is composed of two segments.
Internal skeletal structure is composed of MB, A, D, V, two
L, two AL, two DL, two VL, LL and AD (A' ). L- R and L-

21 8

Satoshi Funakawa///

dorsal rib /
/
/

foot

/

/

/

2

3

Figure 9. Diagrams of internal skeletal structure of Lithomelissa trifoliolata Funakawa sp. nov. 1: Internal skeletal structure of left lateral view. 2: Subdivision of two segments with internal skeletal structure. 3:
Internal skeletal structure of apical view. Stars are the branches of D and L and other abbreviations are
explained in the text.
1 and 3 : Grey lines show internal spicules and black lines connecting arches; dotted line is indistinct
element. 2: Thick lines show internal spicules (white) and their prolongations in and outside the shell wall
(black). Weak lines show connecting arches inside the shell wall (white) and in the shell wall (black). Broken
line shows outline of shell. Dark grey part indicates the first segment and light grey part the second segment.

Rd are absent. At the ventral side of shell, there is one
LL below two VL. A forms an apical horn but does notform an apical rib in shell wall of first segment. Apicalhorn is stout, three- bladed and approximately equal inlength to height of first segment. Apical horn has lateralprojections extending from three blades, which sometimes
become narrow strings that connect to external surface offirst segment. V forms a very fine ventral horn. First
segment is hemispherical and distinguished from second
segment by strictures along DL, LL and some branches ofLand D. Junction of A, A' and AL is inside the shell. A'
is well developed and forms AD. Right and left branches
arise from D and connect to right and left DL respectively.
Ventral and dorsal branches arise from L and the latter
connects to DL. Shell wall of first segment is thickened
and external surface is very rough . Pores in first segment
are restricted to its basal part and are circular to subcircular. Most internal spicules are circular in section
except for their external parts, such as horns and feet.
Axial projection is distinct. There are no projections onunderside of either D or L. Second segment is irregularly
cylindrical. Lateral and dorsal ribs are difficult to distinguish from complex meshwork on external surface of
second segment. The three feet are three- bladed andshorter than apical horn. Pores in second segment are
irregularly shaped, variable in size and irregularly distributed. Distal aperture of shell is fully open, without teeth .
Dimensions (in ,um).- Measurements are based on ninemature speCimens. Length of apical horn, 47 - 65 (57).
Outside diameter of first segment, 66- 83 (77): Outside
diameter of second segment (not including feet), 79-139(110). Inside width between two DL, 49- 68 (58): Inside
depth between ends of D and V, 54- 71 (62). Height offirst segment (not including apical spine), 52 - 71 (63).
Total height of shell (not including spical spine and feet),110- 159 (136).
Remarks. - The internal skeletal composition of thisspecies is very similar to that of Euscenarium microcapitalium sp. nov. but is distinguished by well developed A' which forms distinct AD. This species is distinguished externally from Euscenarium microcapitalium byan irregularly cylindrical second segment and poorly
developed feet. The internal skeletal structure resembles that of Corythomelissa pachyostraca sp. nov. but isdistinguished from it by the presence of AD and theadsence of L- Rd. This species resembles Lithomelissa
sphaerocephalis Chen but is distinguished from it by alarger first segment. It is distinguished from L. challengerae Chen by a smaller second segment, from L. tricorn isChen by the number of horns extending from the surfaceof the first segment and from L. robusta Chen by a smaller
shell (Chen, 1975).
Etymology .- The specific name means "with threeblades" in Latin.
Occurrences. - Very rare in 90081501 and few in
90081306.
Stratigraphic notes .- Upper Oligocene in eastern Hokkaido. Sugiyama (1994) reported this species from theLower Miocene Toyohama Formation, Morozaki Group, incentral Japan.
Temporal change of internal skeletal
structure in Corythomelissa
Four species of Corythomellissa have characteristic
connecting arch compositions . C. pachyostraca is char-

996.

Temporal change of plagiacanthids (Radiolaria)

Figure 10. 1a- 2b : Euscenarium microcapita/ium Funakawa sp. nov. 1a- c : OCUCR - 42, 90081306,
holotype. 1a : Dorsal view; White arrows point to right and left L. 1b: Basal view ; White arrows point toright branch of D and dorsal branch of left L, black ones to right and left AL. 1c : Enlargement of basal view;
Arrows 1 point to right and left AL, 2 to A' and 3 to left DL. 2a- b : OCUCR - 43, 90081306, paratype. 2a :Right lateral view ; White arrow of 2a points to V. 2b: Basal view; Black arrows point to right and left AL.
3a - 4c: Lithomelissa trifo/io/ata Funakawa sp. nov. 3a- b : OCUCR - 44, 90081306, holotype. 31 : Right lateralview ; White arrow points to right L. 3b : Basal view; Black arrows point to right and left AL, white one to AD(A'). 4a- c : OCUCR- 45, 90081306, paratype. 4a : Dorsal view; Black arrow points to D. 4b: Basal view ;White arrows point to left branch of D and dorsal branch of right L, arrows 1 to right and left AL. 4c :Enlargement of basal view ; White arrows point to right and left branches of D, black one to right DL. Scalebars : 1a, 2a, 3b and 4b = 50 ,u m ; 3a and 4a = 100 ,u m : 1b, 1c, 2b and 4c = 20 ,u m .

219

Satoshi Funakawa

220

Figure 11. Temporal changes in internal skeletal structure of Corythomelissa from Late Oligocene to Late
Miocene time. All figures are left lateral views. 1a, b : C. pachyostraca. 2a, b : C. spinosa and C. omoprominentia. 3a, b: C. sp. of Funakawa. 1a, 2a, 3a: Enlarged diagrams of internal skeletal structure, showing connecting arches as black lines and internal spicules as grey lines. 1b, 2b, 3b : Diagrams of strictures
between the first and second segments; Dark grey part indicates the first segment and light grey part thesecond segment; White lines show the elements inside the shell and black lines those in and outside the shellwall ; CD-@ show the structures in the shell surface along arches VL (CD), AL (@ ), O- AL (® ), and AL- AL (@).

Table 1. Occurrences of examined species of Corythomelissa, Euscenarium and Lithomelissa in this study.

EpochsampleNo.
species

L. Mio ( U. Mio

U.Oli

rooo

~

co

a;

Corythomelissa pachyostraca

+

F

F

Corythomelissa spinosa

F

+

+

0000
C')l.[)
C")
~
N
<0
N

'~:

~

LOOCO\
NNr-

00

J~T"""c.o(()"-~'~"90?~~
88
25
25
5:
,\>~~
~________________________~~
m~m~~m~+-~m_4_~~---4 Zm m,}r---------------------r_-+--+-~r_--_4(~--~
Cn

R~------------------------_+--_4--_4--~~--__4

F \ )Corythomelissa omoprominentia~------------------------+--~4---4--~/~---4
Corythomelissa sp. of Funakawa\\ R~--------------~--+-R~~---41

Euscenarium microcapitalium

R

Lithomelissa trifoliolata+\~------------------------_+--_+--_4--~~----~'~----~

F+ : Very rare ; R : Rare; F : Few ; C : Common.

996.

Temporal change of plagiacanthids (Radiolaria)

•
••
••
••

.,
.,c:

••
•••

.,

o

o

221

••
••

•

P\

i

.,

iii

..J

Corythomelissa honida

Euscenarium sp. ct. E trico/pium

••
.,
c:
.,
o

o
:;
CD

W

CoryttJomelissa omoprominentia

·~ t

A
t L'~

iii

"~f!j~ fA

Corythome/issa pachyostraca

.,

.,o

c:

o

C>

o.,
iii
..J

~

a.

Uthomelissa

Figure 12. Suggested evolutionary succession of four species of Corythomelissa, one of
Lithomelissa and one of Euscenarium from Late Oligocene to Late Miocene time. For details ofinternal skeletal structure, see Figures 4, 8 and 9, and discussion in the text.

Satoshi Funakawa

222

acterized by short L-Rd, usually two D-AL and distinct A'(Figures 6-1d, -2c). The internal skeletal structure of thisspecies exhibits considerable intraspecific variation;right or left L-Rd may be absent and at this side, D-AL is
replaced by one DL (Figures 6-1c, -2c). C. spinosa andC. omoprominentia are characterized by long L-Rd andtwo D-AL (Figures 5-1b, -2b; 7-3c). A Late Miocene C.
sp. of Funakawa is characterized by long L-Rd and one
AL-AL (Figure 7-4b). These features are considered to
be important intrageneric skeletal differences and thebasic elements of the internal skeletal structure changed
little from Late Oligocene to Late Miocene time: connecting arch had been transformed significantly throughtime (Figure 11).
Features of the occurrences of four species from theUpper Oligocene to Upper Miocene are noteworthy (Table1); (1) c. pachyostraca is restricted to the Upper
Oligocene and absent in the Lower to Upper Miocene, (2)C. spinosa is common to rare in the Upper Oligocene toUpper Miocene, (3) C. omoprominentia appears in theLower Miocene, (4) c. sp. of Funakawa is rare in theUpper Miocene. It is considered that these patterns ofoccurrence reflect an evolutionary succession. On the

Table 2.

other hand, fluctuating abundance of C. pachyostraca andC. spinosa through Late Oligocene time may represent anenvironmental change within the inner zone of the Kuril
Arc (Fukusawa and Ishihara, 1992).
These four species exhibit three distinct trends ofmorphological change of internal skeletal structures from
Late Oligocene to Late Miocene time (Figure 11). The
first trend is an increase in length of L-Rd; L-Rd is very
short in C. pachyostraca, generally longer in C. spinosaand C. omoprominentia and longest in C. sp. of Funakawa.
The second trend, which is related to L-Rd prolongation,
is a change in the arch position on the dorsal side of shell.
C. pachyostraca, C. spinosa and C. omoprominentia have
two D-AL, and these arches connect with D, while C. sp.
of Funakawa has one AL-AL which passes above D.
This trend indicates that the arches on the dorsal siderose in time through Early to Late Miocene. The third
trend is disappearance of A': C. pachyostraca has distinct A': C. spinosa and C. omoprominentia have indistinct A' that diverges from A at a higher horizon than thejunction of A and AL; C. sp. of Funakawa does not haveA'. It is clear that these three trends in internal skeletal
structures represent evolutionary change in these four

Compiled occurrences of Corythomelissa, Euscenarium and LithomeJissa in previous studies.
Eocene: Oligocene : MioceneiCorythomelissa horrida Petrushevskaya

I

Corythomelissa pachyostraca sp. nov.

I

Corythomelissa spinosa sp. nov.

I

Corythomelissa omoprominentia sp. nov.

!

Corythomelissa sp.

I

Euscenarium tricolpium (Haeckel):

Euscenarium joergenseni (Dumitrica)

I

Euscenarium aft. trico/pium (Haeckel)

unnamed Euscenarium

Uthomelissa charengerae Chen

Uthomelissa cheni Caulet

i

•
•
! • !
I

I

I

I

I

I

I

I

I

I

:

:

I

8

I

I

I

11

I

i

i

11

I

I

I

;

5
2

I

I
9

1

I

I

1

1,

I

5

!

I

:

!

TPleistocene to Recent

I

6, 10

1

I Pliocene

i 4,11 i• I
I

Euscenarium microcapitalium sp. nov.

Uthomelissa ehrenbergi Butschli•

T

References7:

I 3,6,7

I .: This paper

7:

Uthomelissa sp. L. aft. mitra

i

3

i

Uthomelissa robusta Chen

!

3,6

!

6, 10

I

: 1 : Butschli (1882)
2 : Haeckel (1887)
I 3 : Chen (1975)
I 4 : Petrushevskaya (1975)
I 5 : Nishimura and Yamauchi (1984)
6 : Abelmann (1990)
7 : Caulet (1991)
I 8 : Sugiyama (1992): 9 : Sugiyama et al. (1992)
10: Takemura (1992)
I 11: Funakawa (1994)

I

Uthomelissa duoliphysa Caulet
Uthomelissa mitra Butschli

1

I

I

Uthomelissa sphaerocephalus Chen

10

I

Uthomelissa tricornis Chen10i 3,6,10 :Uthomelissa tritoliolata sp. nov.

I

•

I

!

996.

Temporal change of plagiacanthids (Radiolaria)

species (Figure 12): C. spinosa evolved from C. pachyostraca at Late Oligocene or pre-Late Oligocene time; C.
sp. of Funakawa evolved from C. spinosa through Early
Miocene to Late Miocene time. Because C. omoprominentia has internal skeletal structures similar to C.
spinosa, it is considered that C. omoprominentia evolved
from C. spinosa through Late Oligocene to Early Miocene
time.

Phylogeny of Late Oligocene to Miocene
Clathromitrinae based on their internal
skeletal structures
Corythomelissa pachyostraca has two short L-Rd, two
D-AL and distinct A'. This internal skeletal structure isvery similar to that of Euscenarium microcapitalium sp.
nov. and Lithomelissa trifoliolata sp. nov., although thelatter two species have two DL on the dorsal side and AD,
but do not have L-Rd. If the trends of increasing lengthof L-Rd and decline of A' of Corythomelissa are
extrapolated back in time, the internal skeletal structure ofa pre-Late Oligocene form would be very similar to that ofEuscenarium microcapitalium. Furthermore, if the declineof A' is extrapolated back in time, the internal skeletal
structure of E. microcapitalium would be similar to that of
Lithomelissa trifoliolata. These skeletal similarities suggest a provisional hypothesis: C. pachyostraca evolved
from E. microcapitalium or from species ancestral to it; E.
microcapitalium evolved from Lithomelissa trifoliolata orfrom species ancestral to it.

Acknowledgments
The author is grateful to Prof. Akira Yao of Osaka City
University for his discussion and many suggestions, toProf. Itaru Koizumi of Hokkaido University for diatom
identifications of Upper Miocene samples, to Dr. Seiji Sato
of Hokkaido University for many discussions and suggesting the study of the Kawakami Group, to Dr. Paulian
Dumitrica for many discussons and suggestions, to Mr.
Yasuto Ariga of Nippon Oil Exploration Limited for providing unpublished data on diatoms and many suggestions
on the geology of Morawan region, to Dr. Chris Hollis of
Institute of Geological and Nuclear Sciences, New
Zealand for many suggestions and assistance with English expression, and to Dr. John Toler formerly of Dentsu
Advertising for assistance with English expression.

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Swanberg, N.R. and 8j¢rklund, K.R., 1987: The prece-

225

phalic development of the skeleton of Amphimelissa
setosa (Actinopoda: Nassellarida). Marine Micropaleontology, vol. 11, p. 333-341, pI. 1.
Takemura, A., 1986: Classification of Jurassic nassellarians (Radiolaria). Palaeontographica, Abt. A, vol. 195,
p.29-74, pis. H2.
Takemura, A., 1992: Radiolarian Paleogene biostratigraphy in the southern Indian Ocean, Leg 120. In, Wise,
SW. Jr., Schlich, R., et al., Proceedings of the Ocean
Drilling Program, Scientific Results, vol. 120, p.735756, pis. 1-7. Ocean Drilling Program, Collage Station, TX.
Yamagishi, H., Oka, T. and Okamura, T., 1990: Geomorphology and geology of southern Tokachi area. With
Geological Sheet Map at 1 : 50,000, 71 p. Geol. Surv.
Hokkaido. (in Japanese with English abstract)
Yamagushi, S. and Satoh, H., 1989: Geology of the
Nukanai district. With Geological Sheet Map at 1 :50,000, 78 p. Geol. Surv. Japan. (in Japanese withEnglish abstract)Trans. Proc. Palaeont. Soc. Japan, N.S., No. 180, pp. 226-260, 19 Figs., December 30, 1995

Upper Paleozoic bryozoans from the Lake Titicaca
region, Bolivia
Part 1.

Introductory remarks, stratigraphy andsystematic paleontology
SUMIO SAKAGAMI
Konakano 48, Akiruno-shi, Tokyo, 190-01 Japan

Received 5 June 1995; Revised manuscript accepted 4 September 1995
Abstract. A biostratigraphic analysis of the bryozoan fauna of the Upper Paleozoic CopacabanaGroup in the Lake Titicaca region identified 15 genera and 45 species. Eight of the bryozoan species
are new and 14 are presently not assignable to specific taxa. The new species are the cystoporates
Fistulipora carrascoi, F. titicacaensis, F. mu/tidiaphragma, the trepostomes Stenodiscus a/tip/ana,
Pseudobatostomella micropora, P. yanagidai, the cryptostome Rhombopora kawabei and fenestrate
Septopora andeana. Biogeographically, among the 23 formerly described species, eight areendemic to the Andean province, seven are common to the Midcontinent province of North America
and eight are found in the Tethyan province. The bryozoan faunas indicate a strong relationship withthose of the Midcontinent province although considerable migration from the Tethyan realm presumably occurred.
Key words: Bryozoans, biostratigraphy, Copacabana Group, Lake Titicaca region (Bolivia), Upper
Paleozoic
Introduction
The present paper, devoted to the stratigraphic andtaxonomic descriptions of Upper Paleozoic bryozoans
from the Lake Titicaca region, Bolivia, was originallyconceived as an article to be published in the Special
Paper series of the Palaeontological Society of Japan.
Aiming for an earlier date of its publication, however, an
unorthodox style of publication is adopted herein with theoriginal article being split into two separate papers to beprinted in two sequential numbers of this quarterly journal.
Introductory sentences, all the stratigraphic informationand the description of cystoporate and trepostomebryozoans appear in Part 1 of the paper. Part 2 will deal
with the description of cryptostome and fenestratebryozoans and the bibliographic references including all
those cited in both Parts 1 and 2.
Although knowledge of Upper Paleozoic bryozoan
faunas has increased, that of South America hasremained poor. Bassler (1936) established a new genus,
Rhomboporel/a from the "Carboniferous" in Bolivia which
is now considered to be a junior synonym of Rhombotrypel/a. Chronic (in Newe", 1949, 1953) described 18
species from nine genera including 15 new species andtwo new genera from the Copacabana Group in Peru.

Unfortunately, all his identifications were based on
silicified surficial features of the bryozoan colonies.
Since 1980 I have led a team of Japanese geologists tocarry out biostratigraphic field surveys of the CopacabanaGroup in the central Andean region in Peru and Bolivia.
Some preliminary results have been reported by Sakagami(1983, 1984 ed., 1986 ed.), Sakagami et a/. (1981,1983,
1985,1991), Sakagami and Mizuno (1994), Nagai (1983) andYanagida (1983). The present study analyzes thebryozoan fauna from the Copacabana Group in the
Bolivian part of the Lake Titicaca region, where abundantfossils including bryozoans, fusulines, corals, brachiopods, molluscs and others were collected.
The Copacabana Group1.

Pevious work

The name Copacabana was used originally by Cabrera
and Petersen (1936) for the upper part of the limestone
section exposed at the Strait of Tiquina. Because
D' Orbigny (1842) considered the brachiopods from Yaurichambi to be Carboniferous in age, the geological age of
the Copacabana limestone was believed to be Carboniferous by almost all later investigators. Dunbar and Newell997.

Upper Paleozoic bryozoans from Bolivia, Part 1(1946), however, proposed the term Copacabana Group forthe entire group of Upper Paleozoic rocks of the
Copacabana Peninsula and the Strait of Tiquina, andpointed out that the Copacabana Group at Yaurichambi
was Early Permian (Wolfcampian) in age, based on thefusuline fauna.
In the Lake Titicaca region, Newell (1949) measured
three stratigraphic sections of Upper Paleozoic sediments
cropping out at Tiquina, Pirhuate and Munani. His Lower
Permian Copacabana Group consisted of massive graycherty limestone interbedded with gray and red-colored
shales. The basal part of the sequence is comprised ofdark gray and black shales (part of which is nonmarine inorigin). Locally, the upper part had a massive, unfossiliferous red sandstone unit (Tiquina sandstone).
The comprehensive studies on Paleozoic Group of the
Andean region (especially in Peru and Bolivia) by Newell(1949), and Newell, Chronic and Roberts (1949, 1953) are
well known. Newell et al. (1953) recognized four major
divisions in the Upper Paleozoic of Peru, namely inascending order, Mississippian Ambo Group consisting of
dominant sandstone with thin black shales and coal (total
thickness unknown, exceeding 2,700 ft), Pennsylvanian
Tarma Group consisting of thin-bedded limestones andblack shales (maximum thickness about 6,900 m) anddisconformable with the Ambo Group, Pennsylvanian andPermian Copacabana Group consisting of massive limestones and black shales (maximum thickness about 6,300m), and Permian Mitu Group consisting of red beds andvolcanics (maximum thickness about 12,000 ft). They
measured and studied nineteen stratigraphic sections in
Peru, and described many marine fossils including
fusulines, brachiopods, bryozoans, molluscs andechinoderms.
Subsequently, Maeda (1977) reviewed the previous
geological work, the geotectonic problems of the
Copacabana Group in the Bolivian region. Urdininea andYamagiwa (1980) recognized three fusuline subzones(namely, the Triticites nitens, Pseudoschwagerina texana
and Eoparafusulina gracilis subzones) in the Pseudoschwagerina zone in the Copacabana Group at Cerro
Jacha Khatawi in Yaurichambi.
In 1980, a group of Japanese geologists (Sakagami etal., 1981, 1983) mapped the geology of the area between
Lihuirco and Quisuar in the northern part of Abancay,
Peru, where the Permian Copacabana Group is welldeveloped, and discussed the geologic structure of thearea. Subsequently, Nagai (1983) discussed some of thesedimentary environments of the Copacabana Group.
Numerous fossils including fusulines, bryozoans, brachiopods, molluscs and others were collected from 34
outcrops and rock samples for sedimentary petrographic
study were taken from about 150 points along the route.
In 1982, another biostratigraphic field survey (Sakagami etal., 1984) studied the Copacabana Group developed at
Cerro Jacha Khatawi in Yaurichambi and made stratigraphic sections along three routes on a small hill at Cerro
Jacha Khatawi. Abundant fossils such as fusulines,
bryozoans, brachiopods, molluscs and others were col-227

lected. Arellano (1983) described two new Permian
species of trilobites from this region, namely Paladinyampupatensis from Yampupata and Ditomopyge derimsi
from Yaurichambi. Kobayashi and Hamada (1986) studied trilobite specimens collected by Sakagami from thebasal part of the Copacabana Group at Chirapaca, about
8 km north of Copacabana as shown in Figure 8. They
proposed a new genus, Bolivicrania, designating Paladinyampupatensis Arellano as the type species.
In our field work of 1984 (Sakagami et al., 1985; Sakagami ed., 1986), stratigraphic sections were made alongsome routes around Lake Titicaca, namely Cuyavi,
Yampupata, Ancoraimes and Matilde, where theCopacabana Group is well distributed.
Suarez-Riglos et al. (1987) reported on the conodont
biostratigraphy of the Copacabana Group and divided it
into four conodont assemblage zones, namely, Streptognathodus elongatus, Idiognathodus ellisoni, Neogondolella bisselli-Sweetognathus whitei and Neostreptognathodus pequopensis-Sweetognathus behnkeni
Assemblage Zones, in ascending order. They considered the lower two assemblage zones, which were previously recognized as lowermost Permian (Triticites zone;
Triticites nitens subzone) as uppermost Carboniferous(Virgilian) based on the conodont data.
Wilson (1990) described Permian corals from the
Copacabana Group in Bolivia and confirmed that they
belonged to the Cyathaxonid Coral Province, which is
restricted to South and Central America, Mexico and theTexas-Oklahoma-Midcontinent region, USA.
Sakagami et al. (1991) reexamined the CopacabanaGroup distributed along the above-mentioned routes andcollected rock samples for conodont analysis especiallyaround the boundary between the Triticites and Pseudoschwagerina zones. Suarez-Rig los et al. (1987) revised
the correlation of stratigraphic sections and the boundary
between the Carboniferous and the Permian was placedat the base of the Pseudoschwagerina zone. Sakagami
and Mizuno (1994) discovered fusulines (Profusulinella)and conodonts indicating an Atokan (early Middle Pennsylvanian) age for the lower part of the Copacabana.
This was previously considered to be Virgilian (latest
Pennsylvanian) to Leonardian (early Middle Permian) inage.
2.

Stratigraphic sections of the CopacabanaGroup exposed around Lake Titicaca

The geological map (scale: 1/1,000,000) made by
GEOBOL (Geological Survey of Bolivia, 1978) shows the
Copacabana Group divided into two belts with a NW-SE
trend diverging at Yaurichambi. One belt on the southwestern side is narrowly distributed from Yaurichambi tothe northeastern slope of Cumana-Cuyavi and then to thesouthwestern slope of Yampupata (northwestern part of
Copacabana Peninsula). Another belt on the notheasternside is in a complicatedly folded structure of Devonian,
Carboniferous, Permian and Mesozoic or Tertiary strata in
the northeastern part of Titicaca Lake. In addition to

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230

Cerro Jacha Khatawi where three stratigraphic sections
were made in 1982 (Sakagami ed., 1984), stratigraphic
sections at an original scale of 1: 100 were also madealong the following five routes where the CopacabanaGroup is well developed, namely, small Yaurichambi hill(Yt), Cuyavi, Yampupata, Ancoraimes and Matilde routes(Figure 1).
(1)

Yaurichambi
Cerro Jacha Khatawi in Yaurichambi (Figure 3) consistsof a monadnock situated at about 50 km WNW of La Paz
City and well known because of its abundant fossils(fusulines, brachiopods, bryozoans, gastropods, corals
and others) in many stratigraphic horizons. A geologicalmap of the hill at an original scale of 1 : 5,000 (Figure 4)
and measured stratigraphic sections (Figure 2) along threeroutes: Ya-, Yb- and Yc-routes show where many samples were collected.
Cerro Jacha Khatawi is subdivided geomorphologicallyinto two small hills. There are three major faults andsome minor faults, which are perpendicular to the generalstrike of the formation. Throws of these major faults areabout 10 m to 20 m. Devonian, Carboniferous, Permianand Tertiary stratigraphic units trend generally in a NW-SE
direction and dip to the southwest.
The Devonian Sica Sica Series consists of alternating
beds of pale gray to pale green, muscovite-bearing, fine tomedium-grained sandstone and shale with well developed
small-scaled crosslaminae. The series is more than 120

m thick and the lowest part is obscured. The Generalstrike and dip are N75·W and 35·S, respectively.
The Carboniferous Gondwana Series apparently overlies unconformably the Sica Sica Series, but the relationship between these two units cannot be observed. This
Gondwana Series consists mainly of pale purple sandstone. In contrast with the Sica Sica Series, it has lessmuscovite and greater quartz content. The crosslaminations of this series become larger in scale thanthose of the Sica Sica Series. The thickness is about 20
m, and the general strike and dip are N50· -60·W and 60·
S-90·, respectively. The relationship between the Gondwana Group and overlying Copacabana Group is considered to be disconformable.
The Copacabana Group consists mainly of alternating
beds of limestone and mudstone, with some dolostone
and nodular chert. Only two layers are shown in thegeological map (Figure 4). Unit Ya10 may correspond toYb11 in Vb-route and Yc08 in Yc-route. This is confirmedby the presence of a characteristic gastropod, Ompha/otrochus, at these three sites. It is also clear that
Ya36 corresponds to Yc23 in Yc-route (but obscure in
Vb-route) based on the occurrence of bryozoans including
Rhombotrypella and a brachiopod (Composita) at these
two sites (Figure 4). The upperrmost part of this group isintercalated with pale green or pale brown chert or cherty
limestone. Among the fossils, brachiopods predominate
in many horizons throughout the group; fusulines andbryozoans are rare in the lower part but become very~:!

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Sumio Sakagami

232

numerous in the upper part; and corals, gastropods, andbivalves are rare but crowded together in some horizons.
A bivalve, Aviculopinna, is predominant in Ya33 and Yc21,
and these two localities are considered to be at the same
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997.

Upper Paleozoic bryozoans from Bolivia, Part 1

stone. Dolomitization and silicification (chertification) of
limestone are striking. The dolostone and nodular chert
are regarded as final products of diagenetic processes,
because the original texture of the limestone can berecognized easily in thin sections. The dolostone ismade up of very fine- to fine- grained euhedral to subhedral interlocking dolomite crystals and the relics of original
skeletal grains. The chert consists of chalcedonic and/or microcrystalline quartz crystals. Both dolomite andchert are dominant in the upper part of the formation.
The dolostone assumes a reddish-purple color, because
dolomite crystals are rimmed with secondary iron minerals. The thickness of the Copacabana Group is about
215 m in Va-route, and the general strike and dip are
N40·-50·W and 60·-80·S, respectively. This group isoverlain unconformably by a conglomerate which has
been considered to be of Cretaceous age. However,
because the mode of formation of this conglomerate
differs distinctly from the Cretaceous developed in thisregion, we (Sakagami ed., 1984) have been inclined tothink it to be of Tertiary age. The conglomerate comprises mainly rounded and subangular pebbles of sandstone, rarely limestone and chert. The pebbles varies
from several millimeters to 20 cm in diameter. The matrix
is generally a red-colored sandstone. Brachiopod shellfragments derived from the Copacabana Group are rarely
found in the conglomerate.
A small hill, situated at about 2.5 km southeast of Cerro
Jacha Khatawi (Figure 3), is considered by us to be thetype locality of the brachiopods originally described by
D'Orbigny. Wilson (1990), however, reported that this hillcannot be D'Orbigny's locality, based on D'Orbigny's(1842) description. In this small hill, only the CopacabanaGroup crops out, and the base and top are obscured; thethickness is about 72 m. The general strike is N25·30·W and the dip is 50· -60·S in the lower part but gradually decreasing (20· -30·S) upward. Generally, wellstratified dolomitic limestone is predominant, with associated mudstone and shale beds. The dolomite is areddish purple or yellowish brown color. Many fossils,
such as fusulines, bryozoans, brachiopods, crinoids,
corals and gastropods, commonly occur throughout theformation.
(2)

Ancoraimes

At about 1 km north of Ancoraimes (village), Devonian
and Carboniferous strata and the Copacabana Group are
well exposed (Figure 5).
The Devonian consists of thick, hard, medium-grained,gray-colored sandstone with a strike and dip of N48·W
and 58·N, respectively, and is easily recognizable by its
topographically projected distribution.
The Carboniferous strata about 24 m thick overlie unconformably the Devonian beds with a strike and dip of
N45·W and 40· -54·N, respectively, and consist mainly ofgray or bluish-gray siltstone-shale with five horizons offine-grained sandstone beds, 20 cm to 30 cm thick.
The Copacabana Group is considered to overlie theCarboniferous strata with angular unconformity and its

233

upper limit is not exposed. We measured a 175 m-thickstratigraphic section. The strike and dip are about
N60·W and 50· -60·N in the lower part and N70·W--..-E-W
and 70·N--..-60· -80·S (reversed) in the upper part. This
group can be divided lithologically into two parts: thelower part (An01-An28; a m-75 m) consists mainly of
mudstone-shale beds associated with massive, gray tobrown limestone-marl beds in which many brachiopods
and rare fusulines are found; the upper part consists
mainly of massive, pale pink to reddish purple limestonemarl beds with some mudstone-shale and sandstone. In
the upper part of the group, siliceous nodules that may
have been produced by diagenesis are frequently observed and many fossils, such as fusulines, bryozoans,brachiopods and gastropods, are abundant.
(3)

MatildeDevonian, Carboniferous, Permian, Cretaceous andTertiary strata are well distributed along the road to
Matilde Mine from the lodging center situated at about 4
km southeast of the town of Carabuco (Figure 6).
The uppermost part of the Carboniferous Group near thebase of the Copacabana Group consists of fine- tomedium-grained, gray sandstone with well-developed
cross-laminae. The strike and dip are N20· -30·W and
60·E, respectively. The direct relationship between the
Carboniferous and Copacabana Group is not clear
because of lack of outcrops.
The Copacabana Group is about 203 m thick, with ageneral strike and dip of N30· -35·W and 55· -60·N,
respectively, and is unconformably overlain by Cretaceous
strata. Lithologically, this group is subdivisible into twoparts. The lower part (Ma01-Ma23; 0-75 m) consists ofsandstone, siltstone, shale, marl and cherty rock, in whichclastic rocks predominate. The limestone and marl areinterbedded only with shale (gray to dark gray) and containbrachiopods, fusulines, corals, and other fossils. In theupper part (Ma24-Ma78; 75-203 m), dolomite andsiliceous mudstone are predominant, with some sandstone, shale and limestone. The dolomite is reddishpurple and composed of fine- to medium-grained
dolomitic crystals, and is characterized by fossil remains.
The limestone alternates with shale or rather thickdolomite beds. The limestone between the dolomite
beds is reddish purple. These limestones are composedof very coarse calcareous grains and brachiopods,
bryozoans, fusulines, crinoids, and other fossils. The
siliceous mudstone contains green glauconite and/or
purple hematite and many trace fossils. There are slump
structures in the limestone beds (Ma12-Ma13) and ripple
marks in the limy sandstone layer (Ma60).
The Cretaceous overlies the Copacabana Group, andconsists of massive, reddish mudstone. The strike anddip are N-S and 28·E, respectively.
(4)

CuyaviCuyavi is a small village situated about 20 km west of
Yaurichambi and about 10 km northwest of the town of
Ayagachi (Figure 7). A poor road alongside the lake

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Geological map of the Carabuco area (by GEOBOL). showing the Matilde (Ma) section.

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Geological map of Cum ana Island (by GEOBOL), showing the Cuyavi (Cu) section.

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236

Sumio Sakagami

SERVICIO GEOLOGICO DE BOLIVIADEPARTAMENTO DE RECURSOS NATUUI.ES
DIVISION DE PAlEONTOLOGIA

MAPA GEOLOGICO DE LA ZONA DE YAMPUPATANt
La Paz

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Figure 8.
Chirapaca.

Geological map of the Yampupata area (by GEOBOL), showing the Yampupata (Yp) section and997.

Upper Paleozoic bryozoans from Bolivia, Part 1

connects Aygachi to Cuyavi, via a bridge between Hacienda Yayes and Hacienda Cumana. The CopacabanaGroup is well developed on the northeastern slope of themountain ridge. A synclinal axis runs parallel to the ridge
so the formation dips to the southwest. The Carboniferous Gondwana Series is considered to overlie unconformably the lower units, but the direct relationship cannot
be observed. The Gondwana Series consists mainly of
massive, grayish-white coarse sandstone (quartzosearenite) and grayish-green medium-graind sandstone, witha thin alternation of shale and marl (10 cm-30 cm thick) in
the uppermost part. Cross-bedding is well developed in
the sandstone member. No fossils are observed. The
relationship between the Carboniferous unit and the
Copacabana Group is not clear, but there may be a slight
angular unconformity.
The Copacabana Group consists mainly of limestone,marl, dolomite and mudstone-shale associated sandstone
and chert. The thickness of the group is about 380 m or
more but the upper limit is not exposed. This group canbe divided lithologically into three members. The lower
member (Cu01-Cu67; 0-180 m) is predominantly limestone and marl with some mudstone, shale and sandstone. The limestone and marl are generally gray to darkgray, and bear fusulines, brachiopods, bryozoans andgastropods in some horizons. The middle member(Cu68-Cu80; 180-260 m) consists of dolomite, mudstoneand shale, including marl layers in several horizons. The
dolomite is pinkish-brown to yellowish-brown, but occasionally it is white or grayish and consists of grains finer
than silt. The mudstone and shale are gray, yellowishbrown, purple, pale green and greenish-blue. This member lacks fossils. The upper member (Cu81-Cu117; 260380 m) is predominantly limestone and marl with somedolomite, sandstone, mudstone-shale and chert. The
limestone and marl are gray to dark gray and containbrachiopods, bryozoans, corals, crinoids and fusulines.
Corals are abundant in Cu81 , bryozoans in Cu113 andfusulines in Cu117. As a whole, the pale green to
greenish-blue mudstone-shale-sandstone beds whichcontain much quartz, feldspar, illite and glauconite grainsare characteristic of the Copacabana Group in this area.
Such mudstone-shale-sandstone beds are observed at
two horizons in the lower part, six horizons in the middle
part and four horizons in the upper part.
(5) Yampupata
As shown in the geological map (Figure 8), theDevonian, Carboniferous and Copacabana Groups are insuccession along the southwestern slope of the mountainridge. These strata occupy the southern limb of a
syncline with a NW-SE trend.
The Carboniferous Gondwana Series about 50 m thickconsists of medium- to coarse-grained, pale green sandstone with a general strike and dip of N45°-600W and
500N, respectively.
The Copacabana Group is more than 340 m thick, but
the upper limit is not confirmed; the general strike anddip are N45° -50 0W and 35° -400N, respectively. The rela-237

tionship between the Carboniferous Gondwana Series andCopacabana Group may be a slight angular unconformity.
This group consists of muddy limestone, marl, mudstoneshale and sandstone. The limestone and marl are mainly
gray to dark gray, but some beds are partly brown andthey contain many brachiopods, bryozoans, fusulines, etc.
The mudstone-shale is a pale green color and is commonly siliceous. Generally, fossils are limited in occurrence.
However, abundant bivalves associated with some brachiopods and rare bryozoans and ammonites occur in thegreen mudstone of the upper part of Yp26 bed. The
sandstone is pale green, fine- to medium-grained, rarely
coarse-grained, and without fossils. The Yp57 to Yp65
beds are fossiliferous, especially with fusulines in Yp57
and Yp62, and bryozoans and brachiopods in Yp65.

3. Faunal assemblages and age
The Copacabana Group in this region has four fusuline
zones, namely from lower to upper, the Profusulinella,
Triticites, Pseudoschwagerina and Eoparafusulina zones.
Eight stratigraphic sections are summarized in Figure 2.
The two sections at Cuyavi and Yampupata are different
in sedimentary characteristics, especially in the lower partof the group. In the Cuyavi and Yampupata sections,
Sakagami and Mizuno (1994) discovered fusulines andconodonts indicating an Atokan age but these fossils are
missing in other routes. The fusulines found at Cu46aand Cu46b horizons in the Cuyavi section and also in a
float collected around Yp10 horizon in the Yampupata
route include Profusulinella munda and Profusulinella sp.
indet. Conodonts are known from several horizons from
Cu04 to Cu46a in the Cuyavi section. The boundary
between this Profusulinella zone (Atokan) and the
Triticites zone (Virgilian) is still obscure, and the total
thickness of these two zones is about 280 m in the Cuyavi
section and 240 m in the Yampupata section.
The Triticites zone is recognized in three sections,
Cerro Jacha Khatawi, Ancoraimes and Matilde, and its
thickness is from 25 m to 40 m. This zone is poorly
developed in the Cuyavi and Yampupata sections
because fusulines and other fossils are very rare.
The Pseudoschwagerina zone is generally about 50 m
thick but it is estimated to be more than 90 m in the
Cuyavi section. The occurrence of the gastropod Ompha/otrochus near the base of the Pseudoschwagerinazone is most characteristic and it is widely distributed at
Yt10, Yc08, Yb11a, Ya10a, An12, Ma13, Cu96 and Yp61.
Fusulines, brachiopods and bryozoans commonly occur inmany horizons.
In the upper part of Cerro Jacha Khatawi (Ya, Vb. andYc routes), and Ancoraimes and Matilde sections, theEoparafusulina zone is thicker than the lower two fusuline
zones but the exact thickness of the zone is uncertain.
The thickness of the Eoparafusulina zone can be measured only in the Ya section at Cerro Jacha Khatawi,
where it is about 130 m thick from the base to the boundary with the Tertiary. In the Cuyavi section, the Eoparafusulina zone cannot be recognized within the area ofSumio Sakagami

238

our surveyed section. In this zone, a characteristic
autochthonous bivalve, Avicu/opinna, occurs in almost all
horizons, but has not yet been confirmed in this Yt-section
or Vb-section at Cerro Jacha Khatawi, Cuyavi and
Yampupata.
As mentioned above, the Copacabana Group distributed
around the Lake Titicaca may range in geological age
from Atokan (early Middle Pennsylvanian) to Leonardian(early Middle Permian).

4.

Analysis of bryozoan fauna

Chronic (in Newell et a/., 1949,1953) described 18
species of nine genera of bryozoans from the Upper
Paleozoic of Peru, of which 14 species of eight genera
were from the Copacabana Group and four species of two
genera were from the Pennsylvanian Tarma Group.
Except for Meekopora sp. cf. M. prosseri and Streb/otrypasp., twelve bryozoan species from the Copacabana Group

Table 1.

~
Species

Distribution of the bryozoans from the
Copacabana Group

L

M

Eo-Z

Ps-Z

Tr-Z

U

L

M

0

0

U

L

M

U

Genus Fistulipora
F. incrustans

F. cf. F. timorensis

0

F. carrascoi sp. nov.

0

F. titicacaensis sp. nov.

0

F. mu/tidiaphragma sp. nov.

0

F. sp. indet. A

0

F. sp. indet. B

0

F. sp. indet. C

0

F. sp. indet. D

0

Genus Meekopora
M. prosseri0

M. sp. indet.

0

Genus Gonioc/adia
G. peruviana

?

0

0

0

Genus Stenodiscus
S. a/tip/ana sp. nov.

0

Genus RhombotrypellaR. typica

000

R. aft. R. gigantea
R. ? sp. indet.

0
0

0

0
0

0

0

0

0

Genus Tabu/ipora
T. cf. T. carbonaria
T. sp. indet.

00Genus Dyscritella
D. tenuirama
D. aft. D. komukensis

Genus Pseudobatostomella
P. micropora sp. nov.
P. yanagidai sp. nov.
P. sp. indet.
Tr-Z: Triticites zone,

Ps-Z: Pseudoschwagerina zone,00

Eo-Z: Eoparafusu/ina zone,

?

997.

Upper Paleozoic bryozoans from Bolivia, Part 1

239

bryozoan species and six bryozoan species which areconspecific or have affinities with the North American
Midcontinent fauna.
This study reports the distribution of 15 genera and 45
species from the Copacabana Group in the Lake Titicaca
region, which is shown in Table 1. Bryozoans are absent
in the lower part of the Copacabana Group in theProfusulinella and lower part of the Triticites zones. Only
two species, Fistulipora sp. indet. D and Alternifenestella

were differentiated as new. However, all the specimens
identified and described by Chronic were etched silicified
specimens. Chronic compared the bryozoan fauna withthose of the North American Pennsylvanian to Lower
Permian. Rowett (1975) recognized a remarkably highdegree of similarity between Early Pennsylvanian and
Early Permian invertebrates of northwestern South America and the southern Midcontinent of North America. He
figured that in South America there are six endemic

Copacabana Group in the Lake Titicaca region.

~
Species

CopacabanaGroup
Tr-Z
L

M

Ps-Z
U

L

Eo-Z

M

U

0

0
0

L

M

Genus Rhombopora

R. /epidodendroides
R. eortieata
R. kawabei sp. nov.

0
0

0
0

Genus Streb/otrypa
S. sp. indet.

0

Genus A/ternifenestella
A. minor0

A. aft. A. pajerensis000

A. (C.) eervoides

0

A (C.) aspera

0

A. ? sp. indet.

0

Genus Mini/ya
M. binodata

0

Genus Fabifenestella
F. aft. F. huaseatayana

00

F. sp. indet.

0

Genus Po/ypora
P. elliptiea
P. eye/opora

?

0
0

0

?

P. aft. P. inimiea
P. ct. P. megastoma

00

P. sp. indet. A

0
0
0
0

P. sp. indet. B

0

P. sp. indet. C

0Genus Septopora
S. andeana sp. nov.

0

S. Iineata

00

S. ineaiea
L: Lower,

M: Middle,

U: Upper.

?

U

240

Sumio Sakagami

aff. A. pajerensis, are recognized in the middle part of
the Triticites zone.
Higher, the number of bryozoan species rapidly
increases. Nine species occur in the upper part of the
Triticites zone, 12 species in the lower part of thePseudoschwagerina zone, 10 in the middle part, and 12 in
the upper part. After reaching a climax (18 species) in thelower part of the Eoparafusulina zone, the number of
species rapidly decreases to six species in the middle
part, and only one species, Rhombotrypel/a typica?,
occurs in the upper part of the Eoparafusulina zone.
Among the nine species of the genus Fistulipora, F.
incrustans was originally described from the Pennsylvanian Graham Formation of north central Texas andlater also from the Wreford Megacyclothem (Wolfcampian)of Kansas. It is noteworthy that both Fistulipora cf. F.
timorensis and F. carrascoi sp. nov. are closely related to
the Tethyan species F. timorensis, described originallyfrom Timor Island, and F. hamadae, described from peninsular Thailand, respectively. The other two new species,
F. titicacaensis and F. ? multidiaphragma are readily
distinguished from the two previously described species.
The Bolivian specimens of Meekopora prosseri are
identical with the material which was originally describedfrom the Coal Measures of Nebraska and later from theUpper Pennsylvanian to Lower Permian in the Midcontinental region of North America. M. prosseri may becosmopolitan because it is known not only from the
Copacabana Group in Peru (Chronic in Newell et a/., 1949,
1953), but also from the Permian of the Tethyan province,for example the Mt. Everest (Chomolungma) region, southwestern China (Yang and Xia, 1981) and Afghanistan(Termier and Termier, 1971).
One species of the genus Goniocladia, G. peru viana,
described in the study, is identical to the original specimens which were described from the Copacabana Groupin Peru, and it may be related to G. americana from the
Guadalupian of Texas, U.S.A. (Girty, 1908) and G. timorensis from the Permian of Timor Island (Bassler, 1929).
Stenodiscus altiplana is a new species, but the genus
Stenodiscus had not previously been reported from theLower Permian of the Midcontinent province (Ross andRoss, 1990). Tabulipora carbonaria is widely distributed
from the Middle Pennsylvanian to Lower Permian in the
Midcontinent (Cuffey, 1967). The genus Rhombotrypel/aextends from the Russian platform via the North American
Cordillera into Bolivia in the Upper Carboniferous andLower Permian. The genera Oyscritel/a andPseudobatostomel/a are recorded for the first time fromthe Copacabana Group but they are very common in the
Tethyan province.
The genus Rhombopora is very common in the Carboniferous to Permian of the Midcontinent province, especially

Rhombopora lepidodendroides which is widely distributed
along with Fistulipora incrustans and Tabulipora carbonaria
in the Wreford Megacyclothem (Wolfcampian) of Kansas.
The genus Streblotrypa seems to be very limited in its
occurrence in the Copacabana Group of this region.
Eighteen species of fenestellid bryozoans are identified
including five species of Alternifenestel/a. Three ofthese species are indeterminable and the fourth species
was described by Chronic (in Newell et a/., 1949,1953) fromthe Copacabana Group in Peru. The other species, A.
minor, was originally described from the Russian Platform
province.
The species Minilya binodata described in this study
may be identical with the type binodata which was described by Condra (1902) from the upper Virgilian Shawnee
Group of Nebraska. Of two species of the genus
Fabifenestel/a, one has affinities with F. huascatayana
described originally by Chronic (in Newell et a/., 1949,
1953) from the Copacabana Group in Peru and the other isan indeterminable species.
Among seven species of the genus Polypora, three areindeterminable. Polypora aff. P. inimica may be identicalwith the originally described species from the
Copacabana Group in Peru, and Polypora el/iptica in the
study agrees with P. el/iptica (s.s.) described by Elias(1937) in meshwork measurements and essential characters. Polypora cyclopora was originally described fromthe European part of Russia and Polypora cf. P. megastoma is very similar to the specimens from the Middle
Productus limestone of Pakistan.
Of three species of Septopora, S. incaica is alreadyknown from the Copacabana Group in Peru. S. andeana
is a new species and Septopora lineata was originallydescribed from the Lower Guadalupian of Armenia.
Of the named 31 species, eight species are new, eight
are endemic Andean species, seven are common to thoseof the Midcontinent region and eight are in the Tethyan
province. The Tethyan association is considered to besignificant. Lohmann (1970) suggested that "TheCopacabana transgression may be regarded as part of the
major (eustatic?) post-Gondwana transgression which
spread from the warm equatorial Tethys sea over the
Gondwanaland margins, as evidenced by the presence ofcorals and Productus-bearing limestones. Similar transgressions are known elsewhere, for example, in the Salt
Range of Pakistan and India where the famous Productus
beds overlie the Gondwana glacial section".

Systematic paleontology
All specimens are deposited in the collections of the
Department of Earth Sciences, Faculty of Science, Chiba
University (DESC-). Symbols and numbers in parenth-

Figure 9. 1,2. Fistulipora incrustans Moore, longitudinal and tangential sections, x 20, DESC-95032 (Ya12a-21) and
DESC-95029 (Ya12a-17), respectively. 3,4. Fistulipora cf. F. timorensis Bassler, longitudinal and oblique sections, x 20,
DESC-95142 (Ma32-1a) and DESC-95145 (Ma32-4a), respectively. 5,8. Fistulipora sp. indet. B, oblique sections, x 20,
DESC-95019 (Ya12a-6b) and DESC-95022 (Ya12a-9a), respectively. 6. Fistulipora sp. indet. A, longitudinal section, x
20, DESC-95006 (Ya07-2a). 7. Fistulipora sp. indet. C, tangential section, x20, DESC-95093 (Yc16-1a).

997.

Upper Paleozoic bryozoans from Bolivia, Part 1

24 1

242

Sumio Sakagami

eses show the locations and horizons.
Order Cystoporata Astrova, 1964
Suborder Fistuliporina Astrova, 1964
Family Fistuliporidae Ulrich, 1882
Genus Fistulipora McCoy, 1949

Fistulipora incrustans Moore, 1929
Figures 9-1, 2
Fistulipora incrustans Moore, 1929, p. 3, 4, pI. 1, figs. 1, 2, 6, 8;
Warner and Guffey, 1973, p. 8-11, figs. 1-7.
Material.-DESC-95029 (Ya12a-17), DESC-95032(Ya12a-21), DESC-95227 (Yp65-24).
Horizon.-Lower to middle part of Pseudoschwagerinazone in Yaurichambi-a and Yampupata routes.
Oescription.-Zoarium may have been attached to aforeign object such as seaweed.
In tangential section, zooecial tube broadly ovate or
subcircular, longer diameter excluding lunarium ranges
from 0.256 to 0.384 mm and shorter diameter from 0.205 to
0.346 mm. Usually 4 zooecia per 2 mm diagonally.
Lunarium occupies about one third of zooecial circumference, its thickness from 0.064 to 0.102 mm. Vesicular
tissue consists of fine vesicles regular in size, one to threevesicles between adjacent zooecia. Usually 7 to 8 vesicles per mm horizontally.
In longitudinal section, zooecial tube parallel tocoenelasma for a short distance and curved gradually
upward, forming with outer surface of zoarium an angle ofabout 90°. Diaphragms absent. Interzooecial tissue
consists of regularly arranged vesicles which are usuallyquadrate but some are depressed, elongated, or irregularly
shaped. 11 to 14 vesicles per mm longitudinally.
Remarks.-Except for being slightly thicker, the colonies are identical with Fistulipora incrustans, which was
originally described from the Graham Formation (Pennsylvanian) of north-central Texas by Moore (1929) andlater from the Wreford Megacyclothem (Lower Permian) by
Warner and Cuffey (1973), in essential characters.

Fistulipora cf. F. timorensis Bassler, 1929
Figures 9-3, 4
Fistulipora timorensis Bassler, 1929, p.44, pI. GGXXVII(3), figs.
4-9.
Material.-DESC-95142 (Ma32-1a), DESC-95143 (Ma322a), DESC-95144 (Ma32-3a), DESC-95145 (Ma32-4a),
DESC-95146 (Ma32-5a).
Horizon.-Lower part of Eoparafusulina zone in Matilde
route. Associated fossils include Rhombotrypella,
Tabulipora, Oyscritella, Polypora and Aviculopinna.
Oescription.-Zoarium encrusts both sides of Polypora
sp. indet. C and is a thin layer, varying from 1.3 to 2.3 mm
in thickness; occasionally multiple layers present.
In tangential section, zooecial tube broadly ovate or
subcircular, longer diameter excluding lunarium from

0.218 to 0.230 mm and shorter diameter from 0.154 to 0.192
mm. Usually 5.5 to 6 zooecia per 2 mm diagonally.
Lunarium well developed, horseshoe-shaped, occupying
one-third to nearly one-half of zooecial circumference, its
thickness usually about 0.038 mm, but occasionally up to
0.064 mm. Vesicular tissue fine and regular in size, one
to three vesicles between adjacent zooecia. Usually 7 to
8 vesicles per 1 mm horizontally.
In longitudinal section, zooecial tubes parallel tocoenelasma for a short distance and then curved upward,
making a right angle to zoarial surface. Diaphragmabsent. Interzooecial tissue consists of regularly arranged vesicular tissue which is depressed quadrate. 10 to
13 vesicles per 1 mm longitudinally.
Remarks.-The colonies are similar to Fistulipora timorensis Bassler in many respects, but slight differences inzooecial and zoarial measurements have led me to only
compare these specimens with Bassler's species. Fistulipora timorensis was described originally by Bassler(1929) from the Permian of Timor Island, and subsequently
has been described from many places, such as Japan and
Thailand by Sakagami (1961, 1968), Khabarovsk region
and Primorskiy Kray of Russia by Morozova (1970) and
Xizang, China by Yang, Lu and Xia (1981). The colonies
also resemble those of Fistulipora incrustans, but are
distinguishable from the latter by the smaller size of thezooecial tube.

Fistulipora carrascoi sp. nov.
Figures 10-1-4; 11-1,2Material.-Holotype: DESC-95167 (Cu113-7); Paratypes: DESC-95163 (Cu113-1), DESC-95164 (Cu113-2),
DESC-95165 (Cu113-3), DESC-95166 (Cu113-6), DESC95214 (Yp65-10), DESC-95216 (Yp65-12), DESC-95218(Yp65-15), DESC-95220 (Yp65-17), DESC-95222(Yp65-19),
DESC-95223 (Yp65-20), DESC-95225 (Yp65-22), DESC95226 (Yp65-23).
Horizon.-Middle part of Pseudoschwagerina zone in
Cuyavi and Yampupata routes.
Oescription.-Zoarium ramose, diameter ranging from 6.
5 to 11 mm, and occasionally 13 mm.
In tangential section of mature zone, zooecial tubes
nearly circular, with two constricted parts which correspond to the edges of the lunarium. Longest diameter ofzooecium excluding lunarium ranges from 0.294 to 0.384
mm, shorter diameter from 0.256 to 0.333 mm. Usually 4
zooecia per 2 mm in diagonal direction.
In longitudinal section, zooecial tubes parallel to longitudinal direction in central region, but curved gradually
outward, making a right angle in mature zone. Thicknessof mature zone ranging from 1.0 to 1.5 mm. One or two
diaphragms observable near the boundary between
mature and immature zones. Interzooecial tissue in immature zone consists of very coarse vesicles, elongatedquadrate or polygonal and irregular in size, but generally
becoming fine and regular to outer region. Usually 6 to 7,
occasionally 8 vesicles per mm longitudinally, and 5 to 6

997.

Upper Paleozoic bryozoans from Bolivia, Part 1

Figure 10. 1- 4. Fistulipora carrascoi sp. nov., 1, 3 : transverse and longitudinal sections, x 10, paratype(DESC-95166 (Cu113-6)) and holotype (DESC-95167 (Cu113-7)), respectively, 2, 4: enlarged parts of 1 and 3,
x 20.

243

244

Sumio Sakagami

per mm horizontally.
In transverse section, the tangential part of the immature zone and the longitudinal section of the maturezone can be observed.
Remarks.- The colonies are similar to those of Fistulipora hamadae which was described by Sakagami(1966) from the Middle Permian limestone of Ko Muk,peninsular Thailand, especially in the internal structure of
the immature zones, however, they differ in the larger
diameter of the zooecial tubes.
The specific name is dedicated to Dr. Raul Carrasco C.,
the former Director of the Servicio Geologico de Bolivia(GEOBOL), who kindly helped us during our field surveys
in the Lake Titicaca region.
Fistulipora titicacaensis sp. nov.

Figures 11-3,4Material.-Holotype: DESC-95182 (Cu114-4); Paratypes: DESC-95184 (Cu114-6), DESC-95189 (Cu114-24),
DESC-95193 (Cu114-31).
Horizon.-Middle part of Pseudoschwagerina zone in
Cuyavi route.
Oescription.-Zoarium may have been attached to aforeign object such as seaweed.
In tangential section, zooecial tubes irregularly
polygonal, with rounded corners. Shorter diameter usually ranges from 0.256 to 0.307 mm, occasionally to 0.384
mm at its maximum. Usually 3.5 to 4 zooecia per 2 mm
diagonally. Lunarium present but occupying less than
one-fourth of zooecial circumference. Very thin lunarium, less than 0.020 mm.
In longitudinal section, zooecial tubes parallel tocoenelasma for a short distance and curved gradually
upward, meeting outer surface of zoarium at an angle ofabout 90'. Diaphragms absent. Zooecial wall zigzag
except for the side with lunarium which is straight.
Vesicular tissue consists of regularly arranged vesicles
which are usually depressed quadrate, 7 to 8 vesicles per
mm longitudinally.
Remarks. - The present form is characterized by theirregularly zigzag wall of zooecial tubes and the small
lunarium. It can be readily distinguished from the previously described species.
Fistulipora? multidiaphragma sp. nov.

Oescription.-Shape of zoarium uncertain but probablyramose, about 10 mm in diameter.
In tangential section, zooecial tubes nearly circular oroval, shorter diameter ranges from 0.256 to 0.384 mm,
usually 4 to 5 zooecia per 2 mm diagonally. Vesicular
tissue consists of coarse vesicles, usually one to twovesicles between adjacent zooecia. Lunarium indistinct.
In longitudinal section, zooecial tubes gradually curved
outward and outer surface of zoarium nearly at rightangles. Diaphragms abundant and regularly spaced
throughout tube. Interspaces between diaphragms usually 0.192 mm to 0.320 mm. Vesicular tissue bubble-like,irregularly and coarsely developed only in mature zone
and absent in immature zone.
Remarks. - The present form is characterized by lack ofvesicular tissue in the immature zone and abundant,
regularly spaced diaphragms throughout the tube. Thereis some doubt as to its generic assignment, however, thepresent form can be distinguished from any other described species.
Fistulipora sp. indet A

Figure 9-6

Material.-DESC-95006 (Ya07 -2a), DESC-95007(Ya08b-1).
Horizon.-Upper part of Triticites zone in Yaurichambi-aroute.
Oescription.-Obliquely longitudinal and fragmentary
tangential sections attached to sinoporid corals. Zoarium incrusting, composed of two layers in one specimen.
Thickness of each zoarial layer less than 1 mm.
In tangential section, zooecial tube broadly ovate,
shorter diameter from 0.256 to 0.333 mm. Usually 3 to 4
zooecia in 2 mm diagonally. Lunarium occupies about
one-third of zooecial circumference, 0.051 to 0.064 mm inthickness.
In longitudinal section, zooecial tubes parallel tocoenelasma for a very short distance and curved gradually
upward, meeting outer surface of zoarium at an angle ofabout 90'. One slightly convex diaphragm observed near
aperture of tube. Interspaces of zooecia consist of irregularly arranged vesicles.
Remarks.-Specific identification is not made becauseof the poorly preserved sections and insufficient material.
The present form somewhat resembles Fistulipora incrustans.

Figures 11-5-7
Material.-Holotype: DESC-95047 (Ya34-4); Paratypes: DESC-95052 (Ya35a-5), DESC-95053 (Ya35a-6).
Horizon.-Middle part of Eoparafusulina zone in
Yaurichambi-a route.

Fistulipora sp. indet B

Figures 9-5, 8Material.-DESC-95019(Ya12a-6a),

DESC-95022

Figure 11. 1,2. Fistulipora carrascoi sp. nov., tangential and longitudinal but slightly excentric sections, x20,
paratypes (DESC-95225 (Yp65-22a) and DESC-95223 (Ya65-20)). 3,4. Fistulipora titicacaensis sp. nov., longitudinal
and tangential sections, x 20, holotype (DESC-95182 (Cu114-4)) and paratype (DESC-95189 (Cu114-24)), respectively. 57. Fistulipora? multidiaphragma sp. nov., tangential, longitudinal and oblique sections, x 20, holotype (DESC-95047(Ya-34-4)), paratypes (DESC-95053 (Ya35a-6a and b)), respectively.

997.

Upper Paleozoic bryozoans from Bolivia, Part 1

245

246

Sumio Sakagami(Ya12a-9a).
Horizon.-Lower part of Pseudoschwagerina zone in
Yaurichambi-a route.
Description.- Two oblique sections attached to a brachiopod shell and zoarium of Polypora. Zoarium encrusting, consists of one layer; thickness not determinable.
Zooecial tube probably circular, 0.192 mm in average
diameter. Lunarium not strongly developed, occupies
about one-fourth of zooecial circumference, less than
0.050 mm in thickest part. No diaphragm.
Remarks.- There is no specific identification because
the specimens are fragmentary and poorly preserved.

Fistulipora sp. indet. C
Figure 9-7

Material.-DESC-95093 (Yc16-1a), DESC-95094 (Yc163a), DESC-95095 (Yc16-4).
Horizon.-Upper part of Pseudoschwagerina zone in
Yaurichambi-c route.
Description.- Three tangential sections from one fragmentary zoarium. Zoarium probably encrusting, but the
thickness not determinable. Zooecial tube broadly oval,
longer diameter excluding lunarium less than 0.384 mm
and shorter diameter from 0.256 to 0.307 mm. Usually 4
zooecia in 2 mm diagonally. Lunarium small and thin,about one-fourth of zooecial circumference. Usually one
row of vesicular tissue, occasionally two rows of vesicles
between adjacent zooecia.
Remarks.-Because of the poor presevation of the thinsections of the fragmentary zoarium, a specific identification is not possible.

Fistulipora sp. indet. D
Figures 12-1-4

Material.-DESC-95123 (Ma6-4a), DESC-95124 (Ma6(0.5 m up)-2}, DESC-95127 (Ma6 (0.5 m up)-6}, DESC95130 (Ma6 (0.5 m up )-9}.
Horizon.-Middle part of Triticites zone in Matilde route.
Description.-Zoarium encrusting, consisting of about a
3 mm thick layer, may have been attached to a foreign
object such as seaweed.
In tangential section, zooecial tubes nearly circular oroval, shorter diameter from 0.256 to 0.384 mm; usually 3
to 3.5 zooecia per 2 mm diagonally. Lunarium present
but not prominent. Vesicular tissue consists of finevesicles, regularly arranged, usually 2 to 3 vesicles
between adjacent zooecia and 5 to 7 vesicles per mmhorizontally.
In longitudinal section, zooecial tubes parallel tocoenelasma for a short distance, curved gradually upward
and then extending directly to outer surface of zoarium at
an angle of about 90·. Diaphragm absent throughout
tube. Vesicular tissue regularly arranged, usually quadrate, 6 to 7 vesicles per mm longitudinally.
Remarks.- This zoarium is closely similar to Fistulipora
incrustans in its main characters, but it can be distin-

guished from F. incrustans by the less developed lunariumand coarser accumulation of vesicles.
Family Hexagonellidae Crockford, 1947
Genus Meekopora Ulrich, 1889

Meekopora prosseri Ulrich, 1902
Figures 13-2-5
Meekopora prosseri Ulrich in Condra 1902, p.339, pI. 18, fig. 9,

pI. 19, figs. 1-6; Condra, 1903, p. 36, pI. 3, figs. 1-7; Moore
and Dudley, 1944, p.299, 300, pI. 37, figs. 3, 4, pl. 38, figs.
1,8, pI. 39, fig. 3, pI. 41, fig. 7, pI. 42,. figs. 1-3, pI. 44, figs. 1,
2, pI. 45, figs. 1, 2, 4, pI. 46, figs. 4, 8; Warner and Cuffey,
1973, p.14-19, pI. 3, figs. 1-6; Yang and Xia, 1975, p.45,
46, pI. 3, figs. 5-7.
Meekopora cf. prosseri Ulrich. Termier and Termier, 1971, p.
27, pI. 11, figs. 1-3.
Meekopora cf. M. prosseri Ulrich. Chronic in Newell et al., 1953,
p.111, pI. 21, figs. 1, 2.

Material.-DESC-95168 (Cu113-9), DESC-95169 (Cu11310), DESC-95170 (Cu113-11), DESC-95173 (Cu113-14),
DESC-95175 (Cu113-16a, b), DESC-95176 (Cu113-17),
DESC-95188 (Cu114-21), DESC-95194 (Cu114-33), DESC95203 (Cu115-11), DESC-95204 (Cu115-13), DESC-95205(Cu115-16), DESC-95207 (Cu115-18).
Horizon.-Upper part of Pseudoschwagerina zone in
Cuyavi route.
Description.-Zoarial features are only seen in thinsections: probably broad, parallel-sided, flattened, bifurcating frond, 1.5 to 2.0 mm in thickness.
In tangential section, zooecial tubes nearly circular tooval, diameter from 0.141 or 0.205 mm, occasionally 0.320mm at its maximum, usually 5 zooecia per 2 mm diagonally. Lunarium not observed. Interzooecial tissue isfine and regularly arranged, 7 to 8 vesicles per mmhorizontally in inner zone, but occasionally covered bydark dense fibrous tissue.
In longitudinal section, zooecial tubes proximally parallel to mesotheca for some distance, then gradually curved
upward, making a right angle with outer surface of zoarium. One to 2 diaphragms in inner part of zooecial tube.
Vesicular tissue fine and regularly arranged, about 10
vesicles per mm longitudinally in outer zone.
Remarks.-Chronic (in Newell et al., 1953) described
Meekopora cf. M. prosseri from two localities in the
Andean region of Peru, but this was only from surface
silicified specimens, and internal structure is unknown.
This species, widely distributed in time and space, wasdescribed originally from the Coal Measures of Nebraska
by Ulrich (in Condra, 1902), later from the Upper Pennsylvanian (Morrowan to Virgilian) to Lower Permian (Wolfcampian) of the Midcontinent region by Moore and Dudley(1944) and from the Wreford Megacyclothem (Lower Permian) of Kansas by Warner and Cuffey (1973). The
present species was reported also from the Permian of theEverest region (southwestern China) by Yang and Xia(1975) and of Afghanistan by Termier and Termier (1971).

997.

Upper Paleozoic bryozoans from Bolivia, Part 1

Figure 12. 1- 4. Fistulipora sp. indet. 0, 1, 3: obliquely longitudinal and tangential sections, x 10, DESC95130 (Ma6 (1 .5 m up)-9) and DESC-95124 (Ma6 (1.5 m up)-2), respectively, 2, 4 : enlarged parts of 1 and 3, x 20.
5,6. Meekopora sp. indet. , obliquely longitudinal and tangential sections, x 20, DESC-95068 (Ya39a-3) and
DESC-95119 (An40-5), respectively.

247

248

Sumio Sakagami

4
Figure 13. 1. Meekopora sp. indet. , longitudinal section , x 10, DESC-95067 (Ya39a-2). 2- 5. Meekopora
prosseri Ulrich, 2, 4 : longitudinal sections, x 10, DESC-95205 (Cu115-16) and DESC-95203 (Cu115-11) respectively, 3,5: enlarged parts of 2 and 4, x 20.

997.

Upper Paleozoic bryozoans from Bolivia, Part 1

Figure 14. 1- 5. Goniocladia peruviana Chronic, 1, 3, 5 : tangential sections, x 10, DESC-95208 (Yp65-1),
DESC- 95188 (Cu114-21) and DESC-95014 (Ya12a-1), respectively, 2,4: enlarged parts of 1 and 3, x 20.

249

Sumio Sakagami

250

Meekopora sp. indet.
Figures 12-5, 6; 13-1

Material.-DESC-95067 (Ya39a-2), DESC-95068(Ya39a-3), DESC-95079 (Ya44a (below)-1), DESC-95119(An40-5).
Horizon.-Lower to middle part of Eoparafusulina zone
in Yaurichambi-a and Ancoraimes routes.
Oescription.-Zoarium bifoliate, but exact mode ofbifurcation not known because the specimens are only
observed in thin section. Thickness of zoarium notdetermined.
In tangential section, zooecial tubes circular, diameterfrom 0.154 to 0.192 mm, usually 5 to 6 zooecia per 2 mm
diagonally. Lunarium indistinct or absent. Vesicular
tissue regularly arranged, usually 1 to 3 vesicles between
adjacent zooecia in inner zone, and covered by secondary
mineralization.
In longitudinal section, zooecial tubes proximally parallel to mesotheca for a short distance and curving rapidly
upward, and meeting surface of zoarium at an angle of90°. Vesicular material only in inner zone, with 10 vesicles per mm horizontally, and dense fibrous material inouter zone. Diaphragms usually 2 in inner zone, spaced
at about 0.25 to 0.32 mm.
Remarks.- These poorly preserved specimens are notdeterminable to species.
Family Goniocladiidae Waagen and Pichi, 1885
Genus Goniocladia Etheridge, 1876

Goniocladia peruviana Chronic, 1949
Figures 14-1-5
Goniocladia peruviana Chronic in Newell et a/., 1949, p. 135 ;Chronic in Newell et a/., 1953, p. 128, 129, pI. 25, figs. 4-8c.

Material.-DESC-95014 (Ya12a-1), DESC-95208 (Yp651), DESC-9521O (Yp65-6), ?DESC-95001 (Ya06a(1)-1).
Horizon.-Upper part of Triticites zone to lower part of
Pseudoschwagerina zone in Yaurichambi-a route andTriticites zone and middle part of Pseudoschwagerinazone in Yampupata route.
Oescription.-Zoarium consisting of anastomosing
branches. Fenestrules typically hexagonal or irregularly
polygonal with rounded corners. Width of fenestrule
varies from 1.5 to 2.5 mm, and length ranges from 3.2 to
4.1 mm. Number of fenestrules in 10 mm along longer
diameter 2 to 2.5 and a long shorter diameter about 4.
Width of branch ranges from 0.8 to 1.1 mm. Probably 3
alternating parallel zooecial rows on each side of zoarial
branch. Zooecial tubes circular in tangential section
near surface, diameter ranging from 0.128 to 0.154 mm,parallel to coenelasma for a short distance and curved

gradually upward, meeting outer zoarial surface at anangle of about 90°. Diaphragms absent. Interzooecial
tissue consists of vesicles in inner zone and dark fibrousmaterial from 0.25 to 0.30 mm thick in outer zone.
Remarks.-Although Goniocladia peruviana was originally described based on only surface features (Chronic in
Newell et a/., 1949), the present specimens are similar to
Chronic's specimens from the Copacabana Group in Peru
in the size of meshwork. As Chronic noted, this species
seems to be similar to Goniocladia timorensis Bassler(1929) from the Permian of Timor Island, and also to G.
americana Girty (1908) from the Guadalupian of U.S.A.
Among the four specimens at hand, the specimen (DESC95001 (Ya06(1)-01), obliquely oriented section) from theupper part of the Triticites zone in Yaurichambi-a route isquestionably included in the species.

Order Trepostomata Ulrich, 1882
Family Stenoporidae Waagen and Wentzel, 1886
Genus Stenodiscus Crockford, 1945

Stenodiscus altiplana sp. nov.
Figures 15-1-3
Material.-Holotype: DESC-95140 (Ma30-3HOb);
Paratypes: DESC-95049 (Ya35a-1b), DESC-95050(Ya35a-2), DESC-95054 (Ya35b-1), DESC-95066 (Ya38a7), DESC-95070 (Ya39a(2)-1), DESC-95071 (Ya39a(2)-2),
DESC-95072 (Ya43a-1), DESC-95073 (Ya43a-2a, b),
DESC-95074 (Ya43a-3), DESC-95075 (Ya43a-4), DESC95077 (Ya46 (below)-2), DSEC-95078 (Ya46 (below)-3),
DESC-95079 (Ya46 (below)-4), DESC-95080 (Ya46(below)-5), DESC-95081 (Ya46 (below)-6), DESC-95106(An36-1), DESC-95107 (An36-10), DESC-95111 (An36-14),
DESC-95114 (An38-5), DESC-95115 (An38-7), DESC-95133(Ma30-31-3), DESC-95134 (Ma30-31-4), DESC-95135(Ma30-31-5), DESC-95136 (Ma30-31-6), DESC-95138(Ma30-31-8), DESC-95139 (Ma30-31-9), DESC-95141(Ma30-31-11a), DESC-95147 (Ma32-6), DESC-95148(Ma32-7).
Horizon.-Lower part of Eoparafusulina zone in
Yaurichambi-a, Ancoraimes and Matilde routes.
Oescription.-Zoarium thick, cylindrical ramose stem, 8
to 12 mm, but occasionally 14 to 15 mm in diameter.
Branching mode of zoaria not observed in thin sections.
Thickness of exozone variable, ranging from 0.5 to 3.0mm, but reaches 4 to 5 mm in some cases.
In longitudinal section, zooecial tubes parallel to longitudinal direction in inner part, gradually curving outward inouter part of endozone, and rapidly bending at base of
exozone. Zooecia open almost at right angles to thesurface. Zooecial walls thin and slightly crenulate inendozone, and becoming rapidly thickened at base of

Figure 15. 1-3. Stenodiscus a/tip/ana sp. nov., 1,2: transverse and longitudinal sections, 3: tangential section,
x 20, paratype (OESC-95054 (Ya35b-1b)), holotype (OESC-95140 (Ma30-3HOb)) and paratype (OESC-95133 (Ma30-31-3)),
respectively. 4. Rhombotrypel/a? sp. indet., transverse section, x20, OESC-95006 (Ya07-2b). 5,6. Rhombotrypel/atypica (Bassler), longitudinal and tangential parts of the same zoarial section, x 20, OESC-95016 (Ya12a-3a).

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Upper Paleozoic bryozoans from Bolivia, Part 1

25 1

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252

mature exozone. This is composed of fine laminatedfibrous tissue and is strongly moniliform. Individual
monilae commonly short and closely strung together.
Diaphragms usually absent but occasionally present in
exozone and/or endozone tubes.
In a typical transverse section, zooecial tubes thinwalled, irregularly arranged, polygonal in central part ofendozone. Structures in exozone are the same as thosein longitudinal section.
In tangential section, zooecia circular to oval and irregularly arranged, the longer diameter varies from 0.190 to
0.358 mm, and averages 0.260 mm; shorter diameter
ranges from 0.141 to 0.256 mm, and averages 0.198 mm.
Mesozooecia also circular to oval and very rare, diameter
ranges from 0.064 to 0.128 mm, and averages 0.094 mm.
Well developed acanthoecia having concentric laminate
wall are usually located at the intersection of zooecial
walls. Outside diameter ranges from 0.064 to 0.154 mm,
and averages 0.104 mm.
Remarks.-This new species is closely similar to
Stenodiscus nicho/soni (Waagen and Wentzel, 1886),
originally described as a species of Stenopora from theUpper Productus Limestone. However, Waagen andWentzel in their explanation of P1. CIX placed it in the
Middle Productus Limestone from the mountain east of
Katwahi, Pakistan. S. nicho/soni should be included in
the genus Stenodiscus because the diaphragms are rarely
present in the zooecial tubes. S. altiplana is distinguished from S. nicho/soni in having few mesozooecia
which are common in S. nicho/soni.
Genus Rhombotrypella Nikiforova, 1933
Rhombotrypella typica (Bassler, 1936)

Figures 15-5,6; 16-1-4
Rhomboporella typica Bassler, 1936, p. 159, 160, figs. 9-12.
non Rhomboporella typica Bassler. Shulga-Nesterenko, 1955,

p. 98, pI. 13, figs. 7-9, text-fig. 8a.
Material.-DESC-95016 (Ya12a-3), DESC-95017 (Ya12a4a), DESC-95018 (Ya12a-5), DESC-95031 (Ya12a-20b),
DESC-95033 (Ya12a-26a), DESC-95049 (Ya35a-1a),
DESC-95055 (Ya35c-2), DESC-95056 (Ya35c-3), DESC95057 (Ya35c-4), DESC-95058 (Ya35c-5), DESC-95059(Ya36a-1), DESC-95060 (Ya36a-2), DESC-95061 (Ya36a3), DESC-95062 (Ya36a-4a, b), DESC-95082 (Ya47a-3),
DESC-95083 (Ya47a-4), DESC-95084 (Ya47a-6a), DESC95085 (Ya47a-8a), DESC-95088 (Yb20-1), DESC-95093(Yc16-1b), DESC-95098 (Yc21a-2), IESC-95102 (Yc23a-a),
DESC-95131 (Ma30-31-1a), DESC-95132 (Ma30-31-2a, b),
DESC-95137 (Ma30-31-7a), DESC-95140 (Ma30-31-10a),
DESC-95143 (Ma32-2b), DESC-95149 (Ma33-1), DESC95150 (Ma33-3), DESC-95171 (Cu113-12), DESC-95200(Cu115-5), DESC-95206 (Cu115-17), DESC-95213 (Yp65-9),
DESC-95214 (Yp65-10b), DESC-95216 (Yp65-12b), DESC95217 (Yp65-13a, b), DESC-95219 (Yp65-16a), DESC95221 (Yp65-18b).
Horizon.-Lower part of Pseudoschwagerina zone toupper(?) part of Eoparafusulina zone in Yaurichambi-a, -b,
and -c, Matilde, Cuyavi and Yampupata routes.
Oescription.-Zoarium cylindrical and ramose, branched at a wide angle, usually 2.5 to 4 mm diameter but
varies from about 2 mm to 5.5 mm in zoarial diameter.
Diameter of endozone also varying from 1.6 to 3.5 mm.
Width of exozone narrow, usually less than 1 mm, ranging
from 0.25 to 0.64 mm but reaching as much as 1.4 mm inpart.
In longitudinal section, zooecial tubes straight, parallel
to longitudinal direction in inner part of endozone and thenrapidly curving outward at right angles at base of exozone.
Zooecial walls thin and slightly crenulate in endozone,
and showing progressive bifurcations which occur at
definite curved levels across zoaria and become rapidly
thickened, composed of finely laminated fibrous tissue inexozone. Monilae present but not prominent. Usually
two kinds of diaphragms present in exozone of tube: one
is a centrally perforated diaphragm at the base andanother is a non-perforated, terminal diaphragm nearzooecial opening.
In typical transverse section, zooecial tubes thinwalled, regularly arranged, quadrate in central part, andencompassed by a rhombic or polygonal pattern in outerpart of end ozone.
In tangential section, zooecia oval, regularly arranged inlongitudinal and diagonal directions. 5 to 6, occasionally
7 zooecia per 2 mm longitudinally, and usually 7 per 2 mm
diagonally. Longer and shorter diameters of zooecia
range from 0.154 to 0.256 mm and 0.090 to 0.192 mm,
respectively, and their average diameters 0.208 and 0.126
mm, respectively. Mesoecia rarely present, circular tooval, their shorter diameter ranges from 0.013 to 0.102 mm,
and averages 0.062 mm. Megacanthoecia at the junctions of zooecial walls, composed of concentric fibrous
calcite, their outside diameter ranges from 0.048 to 0096
mm, and averages 0.063 mm. Their inner diameter verysmall, probably less than 0.001 mm. Micracanthoecia ina single series between megacanthoecia, their outside
diameter ranging from 0.020 to 0.032 mm.
Remarks.-The present species was originally described from the "Carboniferous" of Chulpapampa, Bolivia,
which may correspond to the Copacabana Group. Bassler (1936) designated it as the type species of the genus
Rhomboporella in the Order Cryptostomata. Subsequently, many researchers, such as Nikiforova (1939), Condra
and Elias (1944), Shulga-Nesterenko (1955), Dunaeva(1956), Ross and Ross (1962), Malecki (1968), and Boardman and Mckinney (1976), have referred it to this genus.
Boardman and Mckinney (1976) considered Rhomboporella a synonym of the genus Rhombotrypella Nikiforova(1939). In her systematic study of the Order Trepostomata, Astrova (1978) placed Rhomboporella Bassler insynonymy with Rhombotrypella Nikiforova.
This species is distributed widely in time and space in
the Copacabana Group in the Lake Titicaca region.
Bassler (1936) noted in his description of Rhomboporella
typica that the zoarium diameter is 3 mm, however, itvaries from 2 mm to 5.5 mm in the speCimens at hand;

997.

Upper Paleozoic bryozoans from Bolivia, Part 1

Figure 16. 1- 4. Rhombotrypella typica (Bassler), 1,2, 4 : longitudinal sections, 3 : transverse section, x
20, DESC-95059 (Ya36a-1), DESC-95083 (Ya47a-8a), DESC-95062 (Ya36a-4b and 4a), respectively.

253

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254

occasionally small branches (2 to 3 mm in diameter) arise
from larger branches. Shulga-Nesterenko (1955) described material as Rhomboporel/a typica from the
Gzhelian of the Late Carboniferous of Russian platform,
but these specimens are distinguished from the Bolivian
species by their thicker exozone.
The present species resembles Rhombotrypel/a holmensis Ross and Ross (1962) from the Desmoinesian(Pennsylvanian) of Northeast Greenland in most characters except for the difference in zoarial diameter as
mentioned by them.
Rhombotrypella aff. R. gigantea Rossand Ross, 1962

Figure 17-6
Compared Rhombotrypel/a gigantea Ross and Ross, 1962, p.
27 -29, pI. 6, figs. 2, 3, pI. 7, figs. 1, 3, 4, pI. 17, figs. 4, 5.
Rhombotrypel/a cf. gigantea Ross and Ross. Mafecki,19777,
p. 81, 82, pI. 4, figs. 1a-c.
Material.-DESC-95110 (An36-13).
Horizon.-Lower part of Eoparafusulina zone in Ancoraimes route.
Oescription.-A single longitudinal, partly tangential
section shows a zoarium that is thick cylindrical andramose; about 8 mm in diameter. Diameter of endozone
about 4 mm and width of exozone about 2 mm.
In longitudinal section, zooecial tubes parallel longitudinal direction, gradually curving outward in end ozone, andstraight and perpendicular to surface exozone. Zooecial
walls thin and straight, with arcuate rows of monilae inendozone, and curving strongly outward at proximal end of
exozone; thickening rapidly and showing well developed
monilae composed of finely laminated fibrous tissue inexozone. Perforated diaphragms usually lie between two
monilae, as many as 6 per 2 mm length of tube.
In transverse section, zooecial tubes thin walled, regularly arranged quadrate or rhomboidal in central part.
In tangential section, zooecia circular to oval, irregularly
arranged, longer diameter ranges from 0.154 to 0.256 mm,
and averages 0.205 mm; shorter diameter ranges from
0.128 to 0.179 mm, and averages 0.154 mm. Circularmesozooecia present but not numerous, diameter about
0.100 mm. Megacanthoecia located at intersections ofzooecial walls and a single series of micracanthoecia
arranged in outer part of zooecial walls. Outside diameters of megacanthoecia and micracanthoecia about
0.10 mm and 0.05 mm, respectively.
Remarks.-Although present in only one thin section,
this fragment may be compared with Rhombotrypel/agigantea Ross and Ross (1962) from the Wolfcampian? ofNortheast Greenland in the wide exozone, well developed
monilae and numerous perforated diaphragms, as well asother characters. The zoarial diameter of the present
form is a little smaller than that from Greenland, but
this may not be so important for specific identification.
Mafecki (1977) described Rhombotrypel/a cf. R. gigantea
from the upper Tokrossli>ya bed of Spitsbergen, andpointed out that the Spitsbergen specimen differed fromthe Greenland form in reduced zoarial dimensions andfewer perforated diaphragms.
Rhombotrypella? sp. indet.

Figure 15-4
Material.-DESC-95005 (Ya07-1, DESC-95006 (Ya072b).
Horizon.-Upper part of Triticites zone in Yaurichambi-aroute.
Oescription.-Zoarium is a cylindrical stem about 5 mm
in diameter, having a hollow axial tube; diameter ofcentral hollow about 2.5 mm; thickness of exozone 0.48
to 0.64 mm.
Zooecial walls thin in endozone and becoming rapidly
thickened, composed of finely fibrous laminae in exozone.
2 or 3 centrally perforated diaphragms in exozone. No
monilae present. Diameter of zooecia ranges from 0.230
to 0.256 mm, and averages 0.243 mm. No mesozooecia
present. Megacanthoecia at junctions of zooecial walls,
composed of concentric fibers, outside and inside diameters 0.080 to 0.096 mm and about 0.010 mm, respectively.
Micracanthoecia probably arranged in a single series
between megacanthoecia, outside and inside diameters
less than 0.032 mm and 0.003 mm, respectively.
Remarks.- This form can be distinguished from Rhombotrypel/a gigantea by having a hollow axial zoarial epithecate tube. The specific identification is not madebecause of insufficient material comprising only twotransverse sections.

Genus Tabulipora Young, 1883
Tabulipora cf. T. carbonaria (Worthen, 1875)

Figures 17-1-5
Chaetetes 7 carbonaria Worthen in Worthen and Meek, 1875, p.
526, pI. XXXII, Fig. 5.
Stenopora carbonaria (Worthen). Ulrich, 1890, p. 445, pI.
LXXIII, figs. 8-8a; Condra, 1903, p. 45, 46, pI. 4, figs. 9-13;
Condra and Elias, 1944, pI. 9, fig. 5.
Stenopora carbonaria var. macu/osa Ulrich, 1890, p.445, pI.
LXXIII, figs.10-10a.
Stenopora carbonaria var. conferta Ulrich, 1890, p. 446, p.
LXXIII, figs. 9, 9a; Condra, 1903, p.46, pI. 4, figs. 14, 15.
Tabulipora carbonaria (Worthen). Cuffey, 1967, p. 1-96, pls.19.
Tabu/ipora arcturusensis Gilmour, 1962, p. 1019, 1020, pI. 142,
fig. 1-9.
Material.-DESC-95065 (Ya38a(up)-2a), DESC-95069(Ya39a-6a), DESC-9569 (Ya39a-6b), DESC-95158 (Cu9798-1), DESC-95159 (Cu97-98-2), DESC-95160 (Cu97-98-3).
Horizon.-Lower part of Pseudoschwagerina zone (Omphalotrochus horizon) in Cuyavi route, and middle part of
Eoparafusulina zone in Yaurichambi-a route.
Oescription.-Zoarium cylindrical, ramose; branchingmode unknown, ranges from 6 to 9 mm in diameter.
Diameter of end ozone from 4.5 to 6 mm and width of997.

Upper Paleozoic bryozoans from Bolivia, Part 1

Figure 17. 1- 5. Tabulipora cf. T. carbonaria (Worthen), 1 : transverse section, 2,4 : longitudinal sections,
3, 5: tangential sections, x 20, DESC-95065 (Ya38a(up)-2a), DESC-95069 (Ya39a-6a), DESC-95069 (Ya39a6b), DESC-95160 (Cu97-98-3) and DESC-95158 (Cu97-98-1), respectively. 6. Rhombotrypella aft. R. gigantea
Ross and Ross, longitudinal section, x 20, DESC-95110 (An36-13).

255

256

Sumio Sakagami

exozone from 0.8 to 1.5 mm.
In longitudinal section, zooecial tubes parallel longitudinal direction in inner part and gradually curve outward inouter part of endozone, and are straight, perpendicular tosurface in exozone. Zooecial walls thin, slightly
crenulate, forming arcuate rows of monilae in endozone
and thickening rapidly with well developed monilae i~
exozone. Complete diaphragms at irregular intervals
which generally shorten to outer part in endozone. In
exozone of zooecial tubes, both complete and centrally
perforated diaphragms at very short interspaces. Intervals between diaphragms vary from 0.13 to 0.32 mm inexozone. Inner edges of many of perforated diaphragms
swollen and extending proximally.
In transverse section, zooecial tubes thin walled, irregularly arranged, polygonal in central part of endozone.
In tangential section, zooecia circular to polygonal withrounded corners and irregularly arranged, longer diameter
ranges from 0.218 to 0.307 mm, and averaging 0.260 mm ;shorter diameter ranging from 0.141 to 0.282 mm, andaveraging 0.216 mm. Mesozooecia circular and rarely
present, diameter ranges from 0.051 to 0.128 mm, andaveraging 0.097 mm. Acanthoecia well developed, having dense laminate wall and usually located at junction ofzooecial walls. Outside diameter of acanthoecia ranges
from 0.080 to 0.128 mm, and averages 0.098 mm; andinner diameter large, 0.032 mm up to 0.045 mm. In somecases, very small granulated structure and/or divisionallines observed in central part of zooecial walls.
Remarks.-This species was described originally by
Worthen (in Worthen and Meek, 1875), as a coral,
Chaetetes, based only on the external colony. The internal structures were later examined and identified with thebryozoan genus Stenopora by Ulrich (1890). Easton(1943, p. 142) placed this species in the genus Tabulipora.
A detailed study of Tabulipora carbonaria from the Wreford
Megacyclothem (Lower Permian in Kansas, U.S.A.) by
Cuffey (1967) showed that Tabulipora carbonaria is morpholog!cally a highly variable and long ranging species,
extending from the Middle Pennsylvanian through Early
Permian (he estimated it to have ranged approximately
25my). The present Andean form is closely similar to
Tabulipora carbonaria, but Cuffey does not recognize any
mesozooecia in Tabulipora carbonaria and believes that
unusually small zooecia seen externally and in tangential
sections are those of zooecia introduced into the zoarium
wthin .the exozone. However, in the present form, thezooecla and mesozooecia can be distinguished clearly by
their diameters. Cuffey (1967) included the following
three species in Tabulipora carbonaria: Tabulipora amsdenesis Perry and Gutschick (1959), Tabulipora arcturusensis Gilmour (1962) and Stenopora pauca Perkins andPerry (1962). However, only T. arcturusensis from theArcturus Formation (Permian) of eastern Nevada, U.S.A.,
may be synonymous. Gilmour (1962) observed that
Tabulipora arcturusensis occurs in association with agastropod, Omphalotrochus, in Nevada, and this is notablepaleogeographically.
Tabu/ipora sp. indet.

Figures 18-1-4
Material.-DESC-95051 (Ya35a-3), DESC-95094 (Yc163b), DESC-95096 (Yc16-5b), DESC-95175 (Cul13-16c, d),
DESC-95177 (Cul13-18), DESC-95178 (Cul13-19), DESC95179 (Cul13-24).
Horizon.-Upper part of Pseudoschwagerina zone in
Cuyavi route and middle part of Eoparafusulina zone in
Yaurichambi-a route.
Description.-Zoarium lamellate, occasionally multiply(3 to 4) layered, thickness of single layer ranges fromabout 1 to 3 mm. Thickness of exozone about 0.4 to 0.6mm.
In longitudinal section, zooecial tubes proximally parallel to zoarial base, and then bending rapidly perpendicular
to surface. Zooecial walls thin in endozone and rapidly
thickened in exozone, and consisting of fine fibers.
Monilae developed but not prominent. Centrally perforated diaphragms that usually appear in thin section, rare or
irregularly distributed, at intervals usually ranging from O.
320 to 0.640 mm.
In tangential section, zooecial tubes polygonal with thinzooecial walls in endozone; polygonal with rounded
corners or circular, and thick walls in exozone. Prominent acanthoecia usually at the intersection of zooecial
walls. Outside and inner diameters of acanthoecia range
from 0.064 to 0.112 mm and 0.005 to 0.032 mm, respectively.
Remarks.-This lamellate Tabulipora is characterized
by rare, centrally perforated diaphragms and poorly developed monilae. Moore (1929) described Tabulipora plummeri, an encrusting zoarium, from the Upper Graham
Formation (Pennsylvanian) of north-central Texas, however, no detailed comparison could be made because
there is no description or illustrations of the internal
structures.
Family Dyscritellidae Dunaeva and Morozova, 1967
Genus Dyscritella Girty, 1911
Dyscritella tenuirama Crockford, 1957

Figures 18-5, 6
Oyscritella tenuirama Crockford, 1957, p. 52, 53, pI. 13, figs. 1,

2; Sakagami, 1968, p. 54, 55, pI. VIII, figs. 4-8.

Figure 18. 1-4. Tabulipora sp. indet., 1,3,4: longitudinal sections, 2: tangential section, x 20, DESC-95051
5,6. Oyscritella
tenUirama Crockford, obliquely longitudinal and transverse sections, x 20, DESC-95090 (Yb20 (block)-4a) and DESC95088 (:b20 (block)-3), respectively. 7,8. Oyscritella aft. O. komukensis Sakagami, obliquely transverse and longitudinal sections, x 20, DESC-95145 (Ma32-4b) and DESC-95146 (Ma32-5b), respectively.
(Ya3~a-3), DESC-95178 (Cu113-19), DESC-95177 (Cu113-18) and DESC-95179 (Cu113-24), respectively.

997.

Upper Paleozoic bryozoans from Bolivia, Part 1

257

258

Sumio Sakagami

Dyscritella cf. tenuirama Crockford. Sakagami, 1970, p. 50, 51,
pI. VII, fig. 7.
Material.-DESC-95085 (Ya47a-8b, C), DESC-95089(Yb20(block)-3), DESC-95090 (Yb20(block)-4a, b), DESC95091 (Yb20(block)-5a, b, c), DESC-95229 (Yp92(up)-1ab), DESC-95230 (Yp92(up)-3), DESC-95231 (Yp92(uP)-6):
DESC-95117 (An39-2c, d).
Horizon.-Lower to middle part of Eoparafusulina zone
in Yaurichambi-a and -b, Yampupata and Ancoraimes
routes.
Description.-Zoarium slender, cylindrical ramose
branches, diameter ranges from 1.3 to 2.5 mm, averaging
ca. 1.7 mm measured on 15 specimens. No surface
spe~imens were obtained, but observation of a tangential
section near the surface suggests that zooecial aperturesprobably are regularly arranged longitudinally and diagonally. Number of zooecial apertures about 3 in 1 mm
longitudinally and 4 in 1 mm diagonally.
In longitudinal section, zooecial tubes parallel longitudinal direction of zoarium in inner part of endozone, but
gradually curve outward to meet outer surface of zoarium
at an angle of 90·. Zooecial walls straight, thin with ac~ntral black. line. in endozone, and becoming rapidly
thickened with finely laminated fibers in exozone.
Length. of mature tubes ranges from 0.32 to 0.60 mm,
averaging 0.45 mm measured on 14 specimens. Diaphragms absent.
In transverse section, zooecial tubes thin walled
polygonal in central part of endozone.
'
In tangential section near the surface, zooecial tubes
oval, I?nger diameter ranges from 0.179 to 0.256 mm,
averaging 0.186 mm measured on 9 specimens· shorter
diameter ranges from 0.090 to 0.154 mm, averaging 0.121
mm measured on 16 specimens. Mesozooecia oval andsporadic, 0.026 to 0.077 mm, averaging 0.044 mm measured on 9 specimens. Well developed acanthoecia
usually located at intersection of zooecial walls in innerpart of exozone, increasing in number in outer part.
?utside diameter ranges from 0.026 to 0.064 mm, averagIng 0.048 mm on 7 specimens; inner diameter ranges
from 0.003 to 0.010 mm, averaging 0.007 mm on the same
7 specimens.
Remarks.- The present form is closely similar to thespecimens described from the Noonkanbah and Liveringa
Formations of the Fitzroy basin, Western Australia.
Dyscritella tenuirama has been reported also from thePermian of the peninsular part of Thailand; one occurrence is from Khao Ta Mong Rai, considered to be
Artinskian or Leonardian in age, and another comparable
form from Ko Muk, is considered to be Late Artinskian toLate Kungurian in age.

Dyscritella aft. D. komukensis Sakagami, 1970
Figures 18-7,8Compared Dyscritella komukensis Sakagami, 1970, p. 49-51, pI.
XIII, figs. 1-5.

Material.-DESC-95142 (Ma32-1b), DESC-95145 (Ma324b), DESC-95146 (Ma32-5b).
Horizon.-Lower part of Eoparafusulina zone in Matilde
route.
Description.-Zoarium cylindrical ramose branches
diameters 4.2 to 4.3 mm measur~d on 3 specimens:
Based on a tangential section near the surface zooecial
apertures do not show any special regularity in either
longitudinal or diagonal direction.
I~ longi.tudi~al section, zooecial tubes parallel to longitudinal direction of zoarium in endozone and bending
gradually outward, but curving rapidly at the boundary
between immature and mature tubes so as to meet outersurface of zoarium at an angle of about 90·. Maturetu~es straight and long, ranging from 1.2 to 1.6 mm, averaging 1.4 mm on 3 specimens. Zooecial walls thin andnearly straight in endozone, but rapidly thickened andconsisting of laminated fibers in exozone. Diaphragms
lacking.
In transverse section, zooecial tube thin walled, irregularly arranged polygons in central part of endozone.
In tangential section, zooecia circular to oval and irregularly arranged; larger diameter ranges from 0.128 to
0.218 mm, averaging 0.186 mm measured on 2 specimens·
shorter diameter ranges from 0.102 to 0.154 mm, averagin~
0:136 mm on 3 specimens. Mesozooecia very common,
circular but occasionally irregularly shaped and variable insize ranging from 0.026 to 0.077 mm. Acanthoecia present but not prominent, surrounded by concentric dark
dense fibers, outside and inner diameters ranging from
0.032 to 0.050 mm and 0.003 to 0.005 mm, respectively.
Remarks.- The present form is identical with Dyscritella
komukensis Sakagami (1970), described from the Lower
Permian of Ko Muk, the peninsular part of Thailand, in all
characters and measurements except for the larger zoarium diameter.

Genus Pseudobatostomella Morozova, 1960

Pseudobatostomella micropora sp. nov.
Figures 19-1-4
Material.-Holotype: DESC-95045 (Ya33b-8b); Paratypes: DESC-95041 (Ya32c-3a, b), DESC-95042 (Ya32c4), DESC-95043 (Ya33b-4a), ?DESC-95063 (Ya36a'-2a),
DESC-95064 (Ya38a(up)-1a, b), DESC-95065 (Ya38a(up)2b), DESC-95092 (Yb24b-2), DESC-95103 (Yc25-1).
Horizon.-Lower to middle part of Eoparafusulina zone
in Yaurichambi-a, -b and -c routes.
Description.-Zoarium cylindrical ramose branches
diameter ranges from 1.1 to 3.2 mm, averaging 1.8 mm o~
10 specimens. A tangential section near the surface
suggests zooecial apertures do not show any specialalignment in either longitudinal or diagonal direction.
In longitudinal section, zooecial tubes parallel to longitudinal direction of zoarium in endozone, but curve gradually outward to be at an angle of about 90· to outer surfaceof zoarium. Length of mature tubes short, ranging from

997 .

Upper Paleozoic bryozoans from Bolivia, Part 1

Figure 19. 1- 4. Pseudobatostomella micropora sp. nov., longitudinal sections, x 20, paratypes (DESC95041 (Ya32c-3a and 3b)), holotype (DESC-95045 (Ya33b-8b)) and paratype (questionably referred, DESC-95063(Ya36a' -2a)), respectively. 5. Pseudobatostomella sp. indet., longitudinal but partly tangential section, x 20,
DESC-95151 (Ma35 (below)-1). 6,7. Pseudobatostomella yanagidai sp. nov., tangential and longitudinal parts ofthe same zoarial section, x 20, holotype (DESC- 95108 (An36-11)).

259

260

Sumio Sakagami

0.25 to 0.64 mm, averaging 0.39 mm on 10 specimens.
Zooecial walls thin and slightly crenulate in endozone,
then rapidly thickened and consisting of finely laminatedfibers in exozone. Usually 2 to 3 straight or slightly
concave diaphragms at irregular intervals in immature
tubes, and only one diaphragm, although partly absent, in
middle part of mature tube.
In transverse section, zooecial tubes thin-walled, irregularly arranged polygons in central part of endozone.
In tangential section near the surface, zooecial tubes
elongated circular to oval and irregularly arranged; longer
diameter ranges from 0.141 to 0.256 mm, averaging 0.212
mm on 8 specimens; shorter diameter ranges from 0.102
to 0.179 mm, averaging 0.131 mm on 10 specimens.
Mesozooecia sporadic and the diameters vary from 0.026
to 0.077 mm, averaging 0.054 mm on 8 specimens. Welldeveloped acanthoecia surrounded by concentric laminate wall, located usually at the intersection of zooecial
walls but occasionally at an intermediate point between
them; outside diameter ranges from 0.026 to 0.048 mm,
averaging 0.036 mm on 9 specimens; and inner diameter
large, ranges from 0.005 to 0.006 mm.
Remarks.- This new species is not unlike Pseudobatostomella spinigera (Bassler, 1929) and P. cylindrica (Crockford, 1941), both of which were described as Batostomella,but it can be distinguished from these two species by thesmaller diameter of the zooecial tube and the presence ofdiaphragms in the immature tube.

Pseudobatostomella yanagidai sp. nov.
Figures 19-6,7Material.-Holotype: DESC-95108 (An36-11); Paratypes: DESC-95109 (An36-12), ?DESC-95044 (Ya33b-6a).
Horizon.-Lower part of Eoparafusulina zone in Ancoraimes route and questionably in Yaurichambi-a route.
Description.-Zoarium cylindrical ramose branches, butbranching pattern is unknown; ranges from 3.3 to 3.9 mm
in diameter. A tangential section near the surface showsno special pattern in either longitudinal or diagonal direction. Diameter of endozone ranges from 2.3 to 2.5 mm
and width of exozone ranges from 0.8 to 1.0 mm.
In longitudinal section, zooecial tubes parallel to longitudinal direction in inner part, rather rapidly curved outward at the boundary between immature and mature
tubes, and straight and perpendicular to the surface inexozone. Zooecial walls thin, slightly crenulate in endozone, and rapidly thickened, consisting of coarse fibers
in exozone. Complete diaphragms rare in immature
tubes and absent in mature tubes.
In transverse section, zooecial tubes thin-walled, irregularly arranged polygons in central part of endozone.
In tangential section, zooecial tubes circular or rhomboidal with rounded corners but occasionally irregularly
shaped; longer diameter ranges from 0.179 to 0.218 mm,

averaging 0.199 mm; shorter diameter ranges from 0.102
to 0.141 mm, averaging 0.122 mm. Mesozooecia rare,rounded triangular to oval, shorter diameter ranging from
0.038 to 0.064 mm, averaging 0.051 mm. Acanthoecia
poorly developed, usually located at the junction ofzooecial walls. Outside and inner diameters about 0.032
mm and 0.006 to 0.010 mm, respectively. A whitish but
occasionally blackish divisional line observed in central
part of zooecial walls.
Remarks.- This species is characterized by the relatively large diameter of the zoarium, rare diaphragm only in
the immature tube and poorly developed acanthoecia near
the surface. This species is comparable with neither anyof the species listed by Astrova (1978) nor other described
species. The specific name is dedicated to Professor
Juichi Yanagida of Kyushu University, who has always
kindly helped me, not only in field surveys but also inlaboratory work.

Pseudobatostomella sp. indet.
Figure 19-5
Material.-DESC-95151 (Ma35(below)-1), DESC-95152(Ma37(20 cm, below)-2c).
Horizon.-Lower part of Eoparafusulina zone in Matilde
route.
Description.-Zoarium cylindrical ramose branches,diameter 1.0 to 1.3 mm; a tangential section near thesurface shows that zooecial apertures do not show any
special pattern in longitudinal or diagonal direction.
In longitudinal section, zooecial tubes parallel to longitudinal direction of zoarium in endozone, but curved
gradually outward and outer surface of zoarium at anangle of about 90·. Zooecial walls thin and slightly
crenulate in endozone, rapidly thickened and consistingof finely laminated fibers in exozone. Length of mature
tubes ranging from 0.32 to 0.38 mm. Usually one straight
diaphragm located at boundary between mature and immature parts of tube.
In transverse section, zooecial tubes thin-walled, irregularly arranged polygons in central part of endozone.
In tangential section near the surface, zooecial tubes
circular to oval in shape and irregularly arranged; longer
and shorter diameters range from 0.154 to 0.179 mm and
0.090 to 0.141 mm, respectively. Small mesozooecia
commonly present; diameters range from 0.026 to 0.051
mm. Many acanthoecia surrounded by concentric laminate walls, lie usually at each point of intersection of azooecial tube and 5 to 8 surround each zooecial aperture.
Outside and inner diameters range from 0.026 to 0.048
mm and 0.003 to 0.005 mm, respectively.
Remarks.- The present form seems to differ from
Pseudobatostomella micropora sp. nov. by a larger numberof acanthoecia. The specific identification, however,must be postponed until more specimens are available.

Trans. Proc. Palaeont. Soc. Japan, N.S., No. 180, pp. 261-281, 8 Figs., December 3D, 1995

Upper Paleozoic bryozoans from the Lake Titicaca
region, Bolivia
Part 2.

Systematic paleontology

SUMIO SAKAGAMI
Konakano 48, Akiruno-shi, Tokyo, 190-01 Japan

Received 5 June 1995; Revised manuscript accepted 4 September 1995
Abstract. Part of the systematic paleontology of Upper Paleozoic bryozoans from the Lake Titicaca
region is found in Part 1 of the present article, Part 2 describes two remaining orders, Cryptostomata
and Fenestrata. Two new species, Rhombopora kawabei and Septopora andeana, are proposed in
the families Rhomboporidae and Septoporidae, respectively.
Key words: Bryozoans, biostratigraphy, Copacabana Group, Lake Titicaca region (Bolivia), Upper
Paleozoic
Introduction
This article is the second installment of a study ofUpper Paleozoic bryozoans from the Lake Titicaca region,
Bolivia, and gives systematic descriptions of two orders,
Cryptostomata and Fenestrata. Of the four orders ofbryozoans recognized in the Bolivian Upper Paleozoic
bryozoan fauna, two orders, Cystoporata and Trepostomata, were described in Part 1 of the present article.
Systematic paleontology
Order Cryptostomata Vine, 1883
Suborder Rhabdomesina Astrova and Morozova, 1956
Family Rhomboporidae Simpson, 1895
Genus Rhombopora Meek, 1872
Rhombopora lepidodendroides Meek, 1872

Figures 1-1-6
Rhombopora /epidodendroides Meek. Newton, 1971, p. 28, 29,

31-35, pI. 1, figs. 1-6, 11, 12, pI. 2, figs. 1-8, 11, 16 (see thesynonym list).
Material.-DESC-95002 (Ya06a (2)-la), DESC-95003(Ya06a (2)-2), DESC-95004 (Ya06a(2)-3a, b), DESC-95021(Ya12a-8a, b), DESC-95034 (Ya20a-3), DESC-95086(Ybl0a-l), DESC-95096 (Yc16-5), DESC-95097 (Yc16-6),
DESC-95105 (An22-4), DESC-95122 (An48-4a, b), DESC95174 (Cu113-15a).
Horizon.-Upper part of Triticites zone to upper part of
Pseudoschwagerina zone at Yaurichambi-a route, upper
part of Triticites zone at Yaurichambi-b route, upper partof Pseudoschwagerina zone at Yaurichambi-c route, andmiddle part of Pseudoschwagerina zone to middle part of
Eoparafusu/ina zone at Ancoraimes route.
Oescription.-Zoarium consists of cylindrical stem,
having small diameter, ranging from 1.0 to 1.6 mm among
14 specimens.
In longitudinal section, axial region formed by a nearlystraight axis; zooecial tubes straight, making a small
angle with longitudinal direction in endozone, but rapidly
bending outward at posterior end of tubes in exozone.
Diameter of endozone varies from 0.5 to 1.1 mm. Thickness of exozone ranges from 0.25 to 0.48 mm.
In tangential section of exozone, zooecial tubes oval,
longer diameter ranges from 0.167 to 0.320 mm, shorter
diameter ranges from 0.115 to 0.192 mm; arranged regularly longitudinally and diagonally, 3 to 4 zooecia per 2
mm longitudinally. Zooecial wall thin in endozone, but
sharply thickened in exozone. One or 2 acanthostyles
surrounded by concentric dark fibers; outside diameter
0.040 to 0.080 mm. One row of paurostyles between
acanthostyles; outside diameter 0.020 to 0.032 mm.
Inside diameter of acanthostyles and paurostyles is notmeasurable because they are too small.
Remarks.-Newton (1971) discussed in detail rhabdomesid bryozoans from the Wreford Megacyclothem(Wolfcampian, Permian) of the Midcontinental U.S.A.
especially Rhombopora /epidodendroides which is mostabundant in the Megacyclothem. He concluded that the
total range of R. lepidodendroides was from the Early
Pennsylvanian to Late Permian and that species varied
little or not at all in its average morphologic features from
Virgilian (Late Pennsylvanian) through Wreford (Early
Permian) time, and that the geographic and stratigraphic

Sumio Sakagami

262

variations of this species lacked any systematic pattern.
The present form appears to be identical with R. lepidodendroides redefined by Newton in its essential
characters, but there are some variations in the zoarial
and zooecial diameters of the Titicaca specimens.
Rhombopora corticata Moore, 1929
Figures 1-7,8; 2-1,2

Rhombopora corticata Moore, 1929, p.137, pI. 17, figs. 3, 4 ;text-figs. 4i, j.

Materia/.-DESC-95023 (Ya12a-10), DESC-95031(Ya12a-20a), DESC-95104 (Yto1-3), DESC-95154 (Cu82-1),
DESC-95155 (Cu82-2), DESC-95156 (Cu82-3), DESC95157 (Cu82-4), DESC-95162 (Cu103-2), DESC-95180(Cu114-2), DESC-95181 (Cu114-39, DESC-95183 (Cu114-5),
DESC-95185 (Cu114-7), DESC-95186 (Cu114-8).
Horizon.-Lower part of Pseudoschwagerina zone at
Yaurichambi-a and Yaurichambi- Yt routes, and upper
part of Pseudoschwagerina zone at Cuyavi route.
Oescription.-Zoarium consisting of cylindrical stem·
diameter varies from 1.1 to 2.6 mm among 12 specimens.'
In longitudinal section, axial region has irregularly linear
axis and straight zooecial tubes, making a small angle
with longitudinal direction in endozone, bending rapidly
outward at posterior end of tubes in exozone. Diameterof endozone ranges from 0.6 to 1.3 mm. Thickness of
exozone varies from 0.2 to 0.8 mm.
In tangential section of exozone, zooecial tubes oval;
longer diameter ranges from 0.205 to 0.320 mm, shorter
diameter ranges from 0.128 to 0.167 mm, regularly arranged in longitudinal and diagonal directions; 3 to 4 zooecia
per 2 mm longitudinally and 5 to 5.5 per 2 mm diagonally.
Zooecial wall thin in endozone, but sharply thickened in
exozone. One to 2 acanthostyles, surrounded by concentric dark fibers at each intersection of zooecial tubes;
outside diameter ranges from 0.064 to 0.096 mm. One
row of paurostyles between acanthostyles; outside diameter ranges from 0.032 to 0.064 mm. Inside diameter ofneither acanthostyles nor paurostymes is measurable
because they are too small.
Remarks.- The present form is assigned to Rhombopora
corticata which Moore (1929) described from the Upper
Graham Formation (Pennsylvanian) in north central Texas,
U.S.A. R. corticata is distinguished from R. lepidodendroides by the thicker exozone and larger zooecial tube
as noted by Moore.

Rhombopora kawabei sp. nov.
Figures 2-3-6

Materia/.-Holotype: DESC-95113 (An38-4a); Paratypes: DESC-95116 (An39-1), DESC-95117 (An39-2a, b),
DESC-95118 (An39-3), DESC-95120 (An43-1a), DESC95121 (An44-29).
Horizon.-Lower part of Eoparafusulina zone at Ancoraimes route.
Oescription.-Zoarium consists of cylindrical stem
varying from 1.8 to 3.2 mm in diameter as measured on -7
specimens.
In longitudinal section, axial region consists of a nearlystraight axis and straight zooecial tubes, making a small
angle with longitudinal direction in endozone, and rapidly
bending outward at posterior end of tubes in exozone.
Zooecial tube in exozone straight and perpendicular tosurface. Diameter of endozone ranges from 0.7 to 1.7mm and width of exozone ranges from 0.5 to 0.8 mm.
In tangential section of exozone, zooecial tubes oval,
longer diameter ranges from 0.192 to 0.256 mm, shorter
diameter ranges from 0.102 to 0.154 mm, regularly arranged in longitudinal and diagonal directions, usually 3.5 to 4
zooecia per 2 mm longitudinally and 5.5 to 6 zooecia per
2 mm diagonally. Zooecial wall thin in endozone, but
sharply thickened in exozone. Usually one, occasionally
two, acanthostyles at each corner of zooecial tube andsurrounded by concentric fibers; outside diameter ranges
from 0.064 to 0.096 mm. Inner diameters of acanthostyles and paurostyles very small, and not measurable.
Remarks.- The present species may be distinguishedfrom Rhombopora lepidodendroides by the larger diameterof the zoarium and wider exozone, and from R. corticata by
the smaller diameter of the zooecial tubes in exozone.
This species is named after Mr. Tetsuya Kawabe of
Chiba University for his kind assistance in the field, andcollecting and preparing bryozoan specimens.

Family Hyphasmoporidae Vine, 1886
Genus Strebotrypa Vine, 1885
Streb/otrypa sp. indet.
Figures 1-9,10

Materia/.-DESC-95090 (Yb20 (block)-4c), DESC-95091(Yb20 (block)-5d).
Horizon.-Upper part of Pseudoschwagerina zone at
Yaurichambi-b route.
Oescription.-Only two thin sections of fragmentary
specimens were examined. Zoarium slender, cylindricalramose branches, diameter 0.8 mm and 0.9 mm, respec-

Figure 1. 1, 2. Rhombopora /epidodendroides Meek, longitudinal and transverse sections, x 20, DESC-95002(YaO.6(2)-1a) and DESC-95003 (Ya06(2)-2), respectively. 3-6 Rhombopora /epidodendroides Meek, 3, 5, 6: longitudinal
sections, 4: transverse and oblique sections, x20, DESC-95021 (Ya12a-8a, 8b and Bc), DESC-95105 (An22-4) and
DESC-95174 (Cu113-15a), respectively. 7,8. Rhombopora corticata Moore, oblique and longitudinal sections, x20,
DESC-95023 (Ya12a-10) and DESC-95031 (Ya12a-20a), respectively. 9,10. Streb/otrypa sp. indet., obliquely transverseand longitudinal sections, x 20, DESC-95091 (Yb20 (block)-5d) and DESC-95090 (Yb20 (block)-4c), respectively.

998.

Upper Paleozoic bryozoans from Bolivia, Part 2

263

264

Sumio Sakagami

Figure 2. 1, 2. Rhombopora corticata Moore, longitudinal and transverse sections, x 20, DESC- 95181(Cu114- 3) and DESC- 95183 (Cu114- 5), respectively. 3 - 6. Rhombopora kawabei sp. nov., longitudinal but partly
tangential sections, x 20, paratypes (DESC- 95117 (An39- 2a), DESC - 95116 (An39-1)), holotype (DESC - 95113(An38- 4a (5, 6 are from the same zoarial section))), respectively.

998.

Upper Paleozoic bryozoans from Bolivia, Part 2

tively.
In longitudinal section, diameter of central bundle 0.15mm and 0.17 mm; number of tubes in central bundle
usually 3. Ratios of zoarial diameter to central bundle
about 5: 1. Zooecial tubes arise from central bundle atan angle of about 20", straight in endozone and curving
rapidly at inner edge of exozone. Width of outer region of
tube 0.13 mm and 0.18 mm. Metapores arise from base of
exozone, approximately parallel to endozone wall for avery short distance, then curving rapidly outward andparallel to zooecial tubes in exozone.
In tangential section of exozone, zooecial tubes oval,
longer diameter 0.115 to 0.141 mm and shorter diameter
0.090 to 0.102 mm, as measured on 2 specimens.
Zooecial apertures arranged regularly in longitudinal anddiagonal series. Superior hemiseptum at posterior end of
exozone, inferior hemiseptum opposite side to superior
hemiseptum. Usually two rows of metapores between
zooecial tubes and 3 in each longitudinal row; total
number of metapores usually 6. Diameter of metapore
0.026 to 0.032 mm. Diaphragms lacking. Because oflack of a true transverse section, number of tubes incentral bundle could not be counted distinctly, but probably about 10.
Remarks.-With only fragmentary zoaria, the specificidentification is deferred until better material is available.
Order Fenestrata Elias and Condra, 1957
Family Fenestellidae King, 1849
Genus AlternifenestellaTermier and Termier, 1971265

curved outward and becoming parallel to tangential direction of zoarium in upper level. Zooecial tubes nearsurface circular in tangential section, ranging from 0.080
to 0.090 mm in diameter, 16 to 18 zooecia per 5 mm
longitudinally, consistent pattern of apertures in relation todissepiments; 2 apertures per fenestrule. Nodes arranged regularly in one row on well-developed straightcarina, 0.050 to 0.060 mm in diameter, and spaced atabout the same interval as apertures, namely 17 to 18 per
5 mm length of branch. Stereom covering reverse side ofbranch consisting of inner semitransparent layer of colonial plexus and outer sclerenchyma of darker fine fibers
without spicules.
Meshwork formula.-17-20/16-18/ /16-18/17-18* (*1720 branches in 10 mm of zoarial width; 16-18 fenestrulesin 10 mm zoarial length; 16-18 zooecia in 5 mm of branch
length; 17-18 nodes in 5 mm of branch length).
Remarks.- The present form is closely similar to Alternifenestella minor, originally described as Fenestelladonaica (Levedev) a by Nikiforova (1927) and later named
F. donaica var. minor by Nikiforova (1933) from the middle
Carboniferous of the Donetz basin. A slight difference inthe meshwork formula between the original specimensfrom the Donetz basin and the present material is considered to be conspecific variation.
The narrower width of the branch in comparison to thatof the fenestrule, the arrangement of zooecial tubes instrongly alternating longitudinal series and their strong
curvature are distinctive characters of this species.
Alternifenestella aff. A. pajerensis (Chronic, 1949)

Alternifenestella minor (Nikiforova, 1933)

Figure 3-6

Figure 3-2

Fenestrellina pajerensis Chronic in Newell et al., 1949, p. 123 ;Chronic in Newell et al., 1953, p. 116, 117, pI. 22, figs.1, 2.

Fenestella donaica (Lebedev) a Nikiforova, 1927, p.249, pI. 12,
fig. 5.

Fenestella donaica var. minor Nikiforova, 1933, p. 13, pI. 3, figs.
1-3; Nekhoroshev, 1948, p. 21, pI. 2, figs. 1a, b, pI. 10, fig. 4.
Shulga-Nesterenko, 1951, p.89,
pI. 1, figs. 3, 6, pI. 17, fig. 1, pI. 18, fig. 5; Trizna, 1958, p.
146,147, pI. 42, fig. 1 ; Kodsi, 1967, p. 66, 67, pI. 2, figs. 14; Termier and Termier, 1971, p.42, pI. 27, fig. 1.

Fenestella minor Nikiforora.

Materia/.-DESC-95015 (Ya12a-2a), DESC-95025(Ya12a-13a), ?DESC-95087 (Yb1Oa-3).
Horizon.-Uppermost part of Triticites zone at Yaurichambi-b and lower part of Pseudoschwagerina zone at
Yaurichambi-a routes.
Oescription.-Zoarium consists of straight parallel
branches connected by dissepiments at regular intervals.
Branches bifurcate infrequently. Branches narrow, ranging from 0.154 to 0.192 mm and 17 to 20 branches in 10 mmhorizontally. Fenestrules quadrate with rounded corners,
wider than branches, width 0.282 to 0.488 mm, length
0.486 to 0.538 mm, 16 to 18 fenestrules per 10 mm lengthof branch. Width of dissepiment narrow, ranging from
0.064 to 0.090 mm. Zooecial tubes arranged in strongly
alternating longitudinal series, typically rhomboidal inlower level of branch, trigonal in middle level, and strongly

Material.-DESC-95007 (Ya08b-1a), DESC-95009(Ya08b-4b), DESC-95125 (Ma6, 1.5 m, up-4), DESC-95126(Ma6, 1.5 m, up-5), DESC-95128 (Ma6, 1.5 m, up-7),
DESC-95129 (Ma6, 1.5 m, up-8).
Horizon.-Middle part of Triticites zone at Matilde
route, and lower part of Pseudoschwagerina zone at
Yaurichambi-a route.
Oescription.-Zoarium consists of straight parallel
branches connected by dissepiments at regular intervals.
Branches probably bifurcated at very long intervals, but nobifurcating points observed on 13 mm branch length.
Branch wider or almost as wide as that of fenestrule,
ranging from 0.205 to 0.256 mm; 24 branches per 10 mmhorizontally. Fenestrules quadrate with rounded corners;
width ranging from 0.179 to 0.256 mm, length ranging from0.320 to 0.448 mm; 18 to 20 fenestrules per 10 mm branch
length. Dissepiments narrow, width ranging from 0.096 to
0.154 mm. Zooecial tubes arranged in strongly alternating longitudinal series; elongated trigonal at middle levelof branch, curved outward and circular at upper level ofbranch, 0.064 to 0.090 mm in diameter. Distance
between zooecial apertures from center to center ranges
from 0.192 to 0.256 mm; 22 to 26 zooecia per 5 mm

266

Sumio Sakagami

longitudinally, not consistently spaced in relation to dissepiments, usually 2.5 apertures per fenestrule. Welldeveloped nodes arranged regularly in one row on straightcarina. Nodes about 0.050 mm in outside diameter, andspaced at the same interval as apertures, namely 22 to 26
per 5 mm branch length. Stereom covering reverse sideof branch consists of inner semitransparent layer ofcolonial plexus and outer sclerenchyma of darker fibers
with minute spicules.
Meshwork formula.-24/18-20/ /22-26/22-26.
Remarks.- The present form may be identical with
Alternifenestella pajerensis (Chronic), described from the
Copacabana Group in Huanta, Peru because the meshwork formulae are very similar. However, detailed
comparison is impossible because Chronic (in Newell etaI., 1949, 1953) described only the silicified surface of thespecimens.
Alternifenestel/a (Cervel/a) cervoides(Chronic, 1949)

Figure 3-1
Cervel/a cervoides Chronic in Newell et al., 1949, p. 124;
Chronic in Newell et al., 1953, p. 118-119, pI. 23, figs. 3a-7.
Material.-DESC-95198 (Cu115-1), DESC-95199 (Cu1153), DESC-95202 (Cu115-9), DESC-95227 (Yp65-24c).
Horizon.-Middle part of Pseudoschwagerina zone at
Cuyavi and Yampupata routes.
Description.-Zoarium consists of straight parallel
branches connected by dissepiments at regular intervals.
Branches bifurcate at long intervals. Branch width
ranges from 0.256 to 0.320 mm; 21 to 26 branches per 10
mm horizontally. Fenestrules quadrate with rounded
corners, and with narrow width, usually less than half thewidth of a branch, ranging from 0.102 to 0.166 mm, length
ranging from 0.192 to 0.358 mm; 24 to 30 fenestrules per
10 mm branch length. Dissepiments narrow, width ranging from 0.102 to 0.141 mm. Zooecial tubes arranged inalternately intersecting longitudinal series, usually trigonalat middle level of branch, curved outward and circular at
upper level of branch, 0.090 to 0.115 mm in diameter.
Distance between zooecial apertures from center tocenter ranges from 0.192 to 0.256 mm; 20 to 25 zooecia
per 5 mm longitudinally per range, not consistently spaced
in relation to dissepiment; less than 2 apertures per
fenestrule. Well developed nodes arranged regularly in
one row on straight carina, ranging from 0.050 to 0.077
mm in outside diameter; spaced at about the same interval as apertures; namely 20 to 25 nodes per 5 mm ofbranch length. Stereom covering reverse side of branch
consists of inner semitransparent layer of colonial plexus
and outer sclerenchyma of darker fibers with abundant,

well-developed spicules.
Meshwork formula.-21-26/24-30/ /20-25/20-25.
Remarks.- The present form may belong to the GroupXII Fenestella spinulosa Condra (Elias and Condra, 1957).
It is nearest in principal measurements to Cervella cervoides which Chronic (in Newell et al., 1949) described asa member of his newly established genus Cervella fromthe Copacabana Group in Peru. Elias and Condra (1957)
provisionally accepted Cervella as a polyphyletic subgenus of Fenestella.
My examination of many thin sections prepared fromthe Copacabana Group shows that the typical Cervellahaving a "superstructure" is not present any where.
Although detailed comparison with the type which presents only surface features cannot be made, the present
form may be identical with Cervella cervoides. It resembles Alternifenestella aspera (Chronic), but differs from thelatter in the meshwork formula and the position of apertures in relation to dissepiment.
Alternifenestel/a (Cervel/a) aspera (Chronic, 1949)

Figure 3-3
Cervel/a aspera Chronic in Newell et al., 1949, p. 125; Chronic
in Newell et al., 1953, p.119, pI. 23, figs.1-2b.
Material.-DESC-95016 (Ya12a-3b), DESC-95024(Ya12a-12), DESC-95026 (Ya12a-14). DESC-95027(Ya12a-15), DESC-95030 (Ya12a-18), DESC-95195 (Cu11435), DESC-95196 (Cu114-38), DESC-95197 (Cu114-40).
Horizon.-Lower part of Pseudoschwagerina zone at
Yaurichambi-a and Cuyavi routes.
Description.-Form of zoarium is unknown but probably
fan-shaped. Zoarium consists of straight parallel
branches connected by dissepiments at regular intervals.
Branches bifurcate at 10 mm intervals. Branch width
ranges from 0.256 to 0.384 mm; 18 to 21 (26 branches in
special case) per 10 mm horizontally. Fenestrules quadrate with rounded corners, width ranging from 0.128 to0.230 mm and length ranging from 0.307 to 0.448 mm; 19
to 22 fenestrules per 10 mm of branch length. Width ofdissepiment ranges from 0.090 to 0.128 mm. Zooecial
tubes arranged in strongly alternating longitudinal series
and usually triangular but occasionally pentagonal atlower to middle levels of branch, curved outward, andcircular at upper level of branch; diameter ranges from
0.090 to 0.115 mm. Intervals between zooecial aperturesfrom center to center range from 0.230 to 0.282 mm.
Zooecial apertures 17 to 22 per 5 mm longitudinally,usually consistent in position in relation to dissepiments.
Two apertures per fenestrule. Well-developed nodes
arranged regularly in one row on straight carina. Nodes
about 0.050 to 0.077 mm in outside diameter, and spaced

Figure 3. 1. Alternifenestel/a (Cervel/a) cervoides (Chronic), tangential section, x 20, DESC-95202 (Cu115-9). 2.
Alternifenestel/a minor (Nikiforova), tangential section, x20, DESC-95025 (Ya12a-13a). 3. Alternifenestel/a (Cervel/a)aspera (Chronic), tangential section, x20, DESC-95030 (Ya12a-18). 4. Minilya binodata (Condra), tangential section, x
20, DESC-95019 (Ya12a-6b). 5. Fabifenestel/a sp. indet., tangential section, x 20, DESC-95224 (Yb65-2a). 6. Alternifenestel/a aff. A. pajerensis (Chronic), tangential section, x20, DESC-95007 (Ya08b-1a).

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Upper Paleozoic bryozoans from Bolivia, Part 2

267

268

Sumio Sakagami

at about the same interval as apertures, namely 18 to 21
per 5 mm of branch length. Stereom covers reverse sideof branch, consists of inner semitransparent layer ofcolonial plexus and outer sclerenchyma of darker fibers
with abundant, well developed spicules.
Meshwork formula.-18-21 (26)/19-22//17-22/18-21.
Remarks.-Although detailed comparison with the type,established on the surface features by Chronic (in Newell
et al., 1953), cannot be made, the present form is similar to
Cervella aspera in its principal measurements. The present species is characterized by prominent and regularly
arranged nodes on a well developed carina.
Alternifenestella?

sp. indet.

Figure 4-3

Material.-DESC-95013 (Ya08b-8).
Horizon.-Upper part of Triticites zone at Yaurichambia route.
Description.-Zoarium consists of straight parallel
branches connected regularly by dissepiments spaced atregularly long intervals. Branches bifurcate at long intervals. Branch width ranges from 0.256 to 0.320 mm and
14 to 18 branches per 10 mm horizontally. Fenestrules
elongate, quadrate with rounded corners, width variable,
ranging from 0.190 to 0.640 mm, length ranges from 0.960
to 1.120 mm; usually 8 fenestrules per 10 mm of branch
length. Dissepiments narrow, width ranging from 0.154 to
0.166 mm. Zooecial tubes arranged in alternating longitudinal series and trigonal to pentagonal at middle level ofbranch, curved outward and oval at upper level of branch,
0.115 to 0.128 mm in shorter diameter near the surface.
Distance between zooecial apertures from center tocenter ranges from 0.230 to 0.256 mm; 18 to 20 zooecia
per 5 mm longitudinally per range, probably consistentspacing of apertures in relation to dissepiment, usually 5
apertures per fenestrule. Straight carina present but
nodes obscure. Stereom covering reverse side of branch
consists of inner semitransparent layer of colonial plexus
and outer sclerenchyma of coarser fibers.
Meshwork formula.-14-18/8/ /18-20/?
Remarks.-Only one poorly preserved specimen isavailable and this is insufficient for specific ·identification.
Genus Minilya Crockford, 1944
Minilya binodata (Condra, 1902)

Figure 3-4
Fenestella binodata Condra, 1902, p.350-251, pI. 21, figs. 12,

13; Elias and Condra, 1957, p.90.

Material.-DESC-95019 (Ya12a-6b).
Horizon.-Lower part of Pseudoschwagerina zone at
Yaurichambi-a route.
Description.-Sample is a single tangential section
showing features at all levels. Zoarium consists ofstraight parallel branches connected by dissepiments atregular intervals. Branches bifurcate at very long inter-vals. Branch almost as wide as or wider than that offenestrule, ranging from 0.320 to 0.384 mm; 16 to 18
branches per 10 mm horizontally. Fenestrules elongate,
quadrate with rounded corners; width ranges from 0.256
to 0.358 mm, length ranges from 0.704 to 0.896 mm; 10 to
11 fenestrules per 10 mm of branch length. Dissepiments
range from 0.154 to 0.179 mm in width. Zooecial tubes
arranged in very weakly alternating longitudinal series,
kidney-shaped at middle level of branch, curved outward
and circular at upper level, range from 0.090 to 0.102 mm
in diameter. Intervals between zooecial apertures from
center to center range from 0.230 to 0.320 mm. Zooecial
apert~res 14 to 16 per 5 mm length of one range, usuallyconsistently spaced in relation to dissepiment, 3 apertures
per fenestrule. Two rows of zigzag nodes prominent on
well-developed broad carina. Total number of nodes
range from 28 to 32 per 5 mm of branch length. Nodes
range from 0.050 to 0.064 mm and are spaced at sameinterval as apertures, namely, one node to each zooecial
aperture. Stereom covering reverse side of branch consisting of inner semitransparent layer of colonial plexus
and outer sclerenchyma of darker fibers with very small
granules.
Meshwork formula.-16-18/10-11/ /14-16/28-32.
Remarks.- The present form belongs to Group VII,
Fenestella (Mini/ya) binodata Condra (Elias and Condra,
1957). In their systematic study of Fenestella, Condra
and Elias established three varieties of binodata, namely,
var. wolfcampensis from the Lower Wolfcampian, var.
leonardensis from the Leonardian and var. wordensis fromthe Wordian of Texas. The present form is nearest in its
measurements to the type binodata which Condra (1902)
described from the Upper Virgilian Shawnee Group of
Nebraska.
Genus Fabifenestella Morozova, 1974
Fabifenestella aff. F. huascatayana (Chronic, 1949)

Figure 4-2
Fenestrellina huascatayana Chronic in Newell et at., 1949, p.
120; Chronic in Newell et at., 1953, p. 114, 115, pI. 22, figs.

3a, b.

Material.-DESC-95007 (Ya08b-1), DESC-95010(Ya08b-5), DESC-95022 (Ya12a-9).
Horizon.-Upper part of Triticites to lower part of
Pseudoschwagerina zones at Yaurichambi-a route.
Description.-Zoarium consists of nearly straight parallel branches connected by dissepiments at long regularintervals. Branches bifurcate frequently. Branch width
narrower than that of fenestrule, ranging from 0.288 to
0.320 mm; about 12 branches per 10 mm horizontally.
Fenestrules elongate, quadrate with rounded corners;
width ranges from 0.480 to 0.640 mm, length ranges from
1.440 to 1.760 mm, 5 to 6 fenestrules per 10 mm of branch
length. Dissepiments narrow, ranging from 0.160 to 0.192
mm in width. Zooecial tubes form very limited alternating
longitudinal series, elongated pentagon or trapezoid with

998.

Upper Paleozoic bryozoans from Bolivia, Part 2269

Figure 4. 1. Fabifenestella sp. indet., tangential section, x 20, DESC - 95215 (Yp65-11). 2. Fabifenestella aff. F. huascatayana(Chronic), tangential section , x 20, DESC- 95010 (Ya08b- 5). 3. Alternifenestella? sp. indet. , tangential section, x 20, DESC95013 (Ya08b- 8). 4. Polypora elliptica Rogers, tangential section , x 20, DESC - 95038 (Ya29b- 6b).

Sumio Sakagami

270well developed hemiseptum at lower level of branch,
circular at upper level, range from 0.090 to 0.102 mm indiameter. Intervals between zooecial apertures from
center to center range from 0.282 to 0.320 mm. Zooecial
apertures 16 to 17 per 5 mm in a range; apertures usuallyconsistently positioned in relation to dissepiment, 6zooecia per fenestrule. Carina not prominent and nodes
indistinct. Stereom covers reverse side of branch, consists of inner semitransparent layer of colonial plexus andouter sclerenchyma of darker fibers with very small granules.
Meshwork formula.-12/5-6/ /16-17 /nothing.
Remarks. - The present form may be identical with
Fabifenestella huascatayana (Chronic), described from the
Copacabana Group in Pasaje-Picchu of Peru, because
the meshwork formulae are very similar. However,detailed comparison is impossible because Chronic described only the silicified surface specimens. The present form resembles Fabifenestella ajensis (Trizna, 1950)
described from the Lower Perminan of the Canadian
Arctic Archipelago by Morozova and Kruchinina (1986) ingeneral features, but it can be distinguished from the latter
species by the larger number of zooecial tubes per 5 mmof branch length (16-17 instead of 12-13).

Fabifenestella sp. indet.
Figures 3-5; 4-1

Material.-DESC-95015 (Ya12a-2b), DESC-95215(Yp65-11), DESC-95224 (Yp65-21a).
Horizon.-Upper part of Triticites zone at Yaurichambia route, and middle part of Pseudoschwagerina zone at
Yaurichambi-a and Yampupata routes.
Oescription.-Zoarium consists of nearly straightbranches connected by dissepiments at regular intervals.
Branches bifurcate frequently, at about every 3 fenestrules. Width of branch usually narrower than that offenestrule, ranging from 0.320 to 0.480 mm; 12 to 14
branches per 10 mm horizontally. Fenestrules quadratewith rounded corners, width ranging from 0.320 to 0.640
mm, length 0.800 to 1.280 mm; 7 to 9 fenestrules per 10
mm of branch length. Dissepiments narrow, range from
0.192 to 0.250 mm in width. Zooecial tubes in limited
alternating longitudinal series, usually trapezoid or
deformed pentagonal at lower to middle levels of branch,and circular at upper level, range from 0.115 to 0.128 mm indiameter. Zooecial apertures 16 to 18 per 5 mm in arange, not consistently positioned in relation to dissepiments but usually 4 to 5 zooecia per fenestrule. Nodespresent, but not distinct in arrangement. Stereom covering reverse side of branch consists of inner semitransparent layer of colonial plexus and outer darker fibers withsmall granules.
Meshwork formula.-12-14/7-9/ /16-18/?
Remarks.- The present form has some similarity to
Fabifenestella huascatayana in the meshwork formula, but
is distinguished by the number of zooecia per fene~trule,
namely 4 to 5 zooecia in the present form and 6 In thelatter species. The specific identification is postponed
until more specimens are available.
Genus Polypora McCoy, 1844

Polypora elliptica Rogers, 1900
Figures 4-4; 5-1
Polypora elliptica Rogers, 1900, p. 7, 8, pI. 4, fig.2; Moore,

1929, p. 23, 24, pI. 3, figs. 7, 8, 20.
Polypora elliptica (5.5.) Rogers. Elias, 1937, p. 327, 328, fig. 3m.

Material.-DESC-95038 (Ya29b-6), DESC-95064(Ya38a(up)-1c), DESC-95099 (Yc21a-7).
Horizon.-Lower to middle part of Eoparafusulina zone
at Yaurichambi-a and -b routes.
Oescription.-Zoarium consists of straight, parallel
branches connected by dissepiments at regular intervals.
Branches bifurcate infrequently. Branch width about
twice that of fenestrule, ranging from 0.320 to 0.576 mm ;usually 14 to 16 branches per 10 mm horizontally. Fenestrules oval in outline; width ranges from 0.192 to 0.320
mm; length from 0.352 to 0.480 mm; usually 12 to 14 per
10 mm of branch length. Dissepiments broad, width
ranges from 0.256 to 0.480 mm. Zooecial tubes usually 3
rows but occasionally 4 rows across a branch, and before
bifurcation 5 rows; just after bifurcation 2 rows; elongate
quadrate or elongate hexagonal zooecia at middle andlower levels of branch because of slightly alternatingintercalated zooecial tubes in longitudinal series.
Zooecial tubes circular in tangential section near surface,ranging from 0.102 to 0.128 mm in diameter. Number ofzooecial apertures ranges from 19 to 21 per 5 mm length of
one range, usually 3 apertures per fenestrule. Interspaces between zooecial apertures from center to center
range from 0.230 to 0.320 mm longitudinally. Stereom
covers reverse side of branch, consists of semitransparent
layer of colonial plexus with some capillary canals andouter sclerenchyma of darker fibers with well developed
fine granules.
Meshwork formula.-14-16/12-14/ /18-21/3(2-4) * (* 1416 branches in 10 mm of zoarial width; 12-14 fenestrulesin 10 mm of zoarial length; 18-21 zooecia in 5 mm ofbranch length; 3 (2-4) number of rows of zooecia):
Remarks.-Elias (1937) discussed the evolutionarychanges in the Polypora elliptica Group, which include a
range as homogeneous stretching of the zoarium in both
longitudinal and transverse directions. The present form
is closely similar to Polypora elliptica (s.s.) in its principal
measurements and features. Rogers (1900) described P.
elliptica from the Kereford limestone of the Oread Formation, which is now dated as the Middle Virgilian.

998.

Upper Paleozoic bryozoans from Bolivia, Part 2

Figure 5. 1. Po/ypora elliptiea Rogers, tangential section, x 20, DESC- 95099 (Yc21a- 7). 2 - 4. Po/ypora
cf. P. megastoma (Koninck), 2, 4 : tangential sections, x 10, DESC- 95011 (Ya08b- 6) and DESC- 95209 (Yp65- 3),
respectively. 3 : enlarged part of 2, x 20. 5. Po/ypora eye/op~ra Eic hwald , tangential section , x 20, DESC95043 (Ya33b- 4b).

271

272

Sumio Sakagami
Polypora cyclopora Eichwald, 1860

Figures 5-5; 6-1
Polypora eyelopora Eichwald, 1860, p. 375, pI. 30, fig. 1 ; Stuckenberg, 1895, p. 156, pI. 12, fig. 4; Nikiforova, 1938, p.140142,250, pI. 33, figs. 1-6, pI. 34, figs. 1, 2; Shulga-Nesterenko, 1941, p. 161, 162, pI. 44, figs. 1-3, text-figs. 125, 126.
Material.-DESC-95043 (Ya33b-4b), DESC-95112(An38-2), DESC-95187 (Cu114-14), DESC-95190 (Cu11426), DESC-95192 (Cu114-30).
Horizon.-Upper (?) part of Pseudosehwagerina zone at
Cuyavi route, and lower to middle part of Eoparafusulina
zone at Yaurichambi-a and Ancoraimes routes.
Deseription.-Zoarium consists of straight, parallel
branches connected by dissepiments at regular intervals.
Branches bifurcate infrequently. Branch width wider
than that of fenestrule, ranging from 0.640 to 0.960 mm, 6
to 7 branches per 10 mm horizontally. Fenestrules oval in
outline, width ranging from 0.576 to 0.800 mm, length from0.960 to 1.440 mm; usually 5 to 6 per 10 mm of branch
length. Dissepiments broad, width 0.480 to 0.800 mm.
Zooecial tubes usually in 6 to 7 rows on each branch, but
before bifurcation increasing to 7 to 9 rows, after bifurcation 5 rows; 16 to 18 per 5 mm length of one range,usually 6 to 7 apertures per fenestrule. Zooecial tubes
arranged in strongly alternating longitudinal series andusually rhomboidal or hexagonal at middle level of branch.
Diameter of zooecial tube near surface ranges from 0.102
to 0.128 mm. Distance between zooecial apertures from
center to center ranges from 0.230 to 0.256 mm longitudinally. Stereom covering reverse side of branch consistsof inner semitransparent layer of colonial plexus and outersclerenchyma of darker fibers with fine granules.
Meshwork formula.-6-7 /5-6/ /16-18/6-7.
Remarks.- The present form is similar to Polypora
eyelopora described from European Russia in the meshwork formula and internal structures. However, thenumber of fenestrules in 10 mm length are slightly different, namely, 5 to 6 in the present form and usually 4 in the
Russian form.

Polypora aff. P. inimica Chronic, 1949

Figures 6-3, 4Polypora inimiea Chronic in Newell et al., 1949, p. 127; Chronic
in Newell et al., 1953, p.121, pI. 26, figs. 1a, b.
Material.-DESC-95168 (Cu113-9b), DESC-95172(Cu113-13), DESC-95191 (Cu114-28), DESC-95196 (Cu11438), DESC-95211 (Yp65-7), DESC-95228 (Yp67-2).
Horizon.-Middle to upper (?) part of Eoparafusulina
zone at Cuyavi and Yampupata routes.
Deseription.-Zoarium consists of straight, parallel
branches connected by dissepiments at regular intervals.
Branches bifurcate infrequently. Branch width wider
than that of fenestrule, ranging from 0.480 to 0.800 mm ;usually 8 to 10 branches per 10 mm horizontally. Fenestrule oval in outline; width ranging from 0.384 to 0.640

mm; length from 0.800 to 1.120 mm, usually 7 to 8 per 10
mm of branch length. Dissepiments of moderate width incomparison to branches, ranging from 0.384 to 0.416 mm.
Zooecial tubes arranged usually in 5 rows on eachbranch, but before bifurcation 6 rows, after bifurcation 3
rows; rhomboidal at middle level of branch because ofstrongly alternating, intercalated zooecial tubes in longitudinal series. Zooecial tubes circular in tangential section
near surface, ranging from 0.115 to 0.128 mm in diameter.
Number of zooecial apertures ranges from 17 to 18 per 5mm length of one range, usually 5 apertures per fenestrule. Interspaces between zooecial apertures from center to center range from 0.230 to 0.256 mm longitudinally.
Nodes less than 0.050 mm in outside diameter, at eachintersection of zooecial apertures. Stereom covers
reverse side of branch, consists of semitransparent layerof colonial plexus with many capillary canals and outersclerenchyma of dark coarser fibers with fine granules.
Meshwork formula.-8-10/7-8/ /17-18/5.
Remarks.- The present form may be identical with
Po/ypora inimiea Chronic, described from the CopacabanaGroup in Peru in terms of the meshwork formula, but adetailed comparison cannot be made because the typespecimens were described only for their surface features.
The present form resembles Po/ypora eye/op~ra, but differs in the meshwork formula and by the presence of one
node beside each zooecial tube. In the specimens fromYp65-7 and Yp67-2 the nodes are obscure but the
specimens are similar in the meshwork formula and othercharacteristics to the Cuyavi specimens.
Polypora cf. P. megastoma (Koninck, 1863)

Figures 5-2-4Fenestella megastoma Koninck, 1863, p. 5, pI. 2, fig. 3.
Polypora megastoma (Koninck). Waagen and Piehl, 1885, p.
785,786, pI. 88, figs. 3, 5-7, pI. 89, fig. 3; Stuckenberg,
1895, p. 238, pI. 23, fig.7; Fritz, 1932, p. 101 ; Nikiforova,
1938, p.146, pI. 33, fig. 10; Crockford, 1957, p.61, pI. 16,
figs. 2, 3.
Materia/.-DESC-95007 (Ya08b-1c), DESC-95008(Ya08b-3), DESC-95009 (Ya08b-4), DESC-95011 (Ya08b6), DESC-95012 (Ya08b-7), DESC-95019 (Ya12a-16),
DESC-95201 (Cu115-6), DESC-95209 (Yp65-3), DESC95212 (Yp65-8), DESC-95219 (Yp65-16a, b), DESC-95226(Yp65-23).
Horizon.-Upper part of Tritieites zone to lower part of
Pseudosehwagerina zone at Yaurichambi-a route, andmiddle to upper (?) part of Pseudosehwagerina zone at
Cuyavi and Yampupata routes.
Deseription.-zoarium consists of straight, parallel,robust branches connected by dissepiments at regularintervals. Branches bifurcate frequently. Branch width
ranges from 0.800 to 1.280 mm; 4 to 8 branches per 10
mm horizontally. Fenestrules elongate, oval to ellipticalin outline; width ranges from 0.576 to 1.280 mm; length
ranges from 2.240 to 3.840 mm; 2 to 4 per 10 mm lengthof branch. Width of dissepiments varies from 0.416 to998. Upper Paleozoic bryozoans from Bolivia, Part 2273

Figure 6. 1. Polypora cyclopora Eichwald, tangential section, x 20, DESC - 95187 (Cu114- 14). 2. Polypora sp. indet. A,
tangential section, x 20, DESC- 95101 (Yc21a- 9). 3,4. Polypora aft. P. inimica Chronic, tangential sections, x 20, DESC- 95168(Cu113- 9b) and DESC- 95211 (Yp65- 7). 5. Polypora sp. indet. B, tangential section, x 20, DESC- 95161 (Cu98- 1).

274

Sumio Sakagami

0.900 mm. Zooecial tubes arranged in strongly alternating longitudinal series usually rhomboidal at middle levelof branch, 6 to 7 rows on each branch, before bifurcation
8 rows, after bifurcation 5 rows; 13 to 15 per 5 mm lengthof one range, usually 10 apertures per fenestrule. Diameter of zooecial tube near surface ranges from 0.115 to 0.141
mm. Distance between zooecial apertures from center tocenter ranges from 0.320 to 0.384 mm longitudinally.
Thick stereom covers reverse side but on obverse side
relatively thin, consists of inner semitransparent layer ofcolonial plexus and outer sclerenchyma of dark coarser
fibers with fine granules.
Meshwork formula.-4-8/2-3/ /13-15/6-7.
Remarks.- The present form, characterized by verylarge meshwork, falls undoubtedly under the group of
Polypora megastoma (Koninck) described from the Middle
Productus limestone of Pakistan by Waagen and Pichi(1885) and Polypora sugiyamae Sakagami (1961) describedfrom the Parafusulina zone in Japan. Although there areslight differences between these Tethyan species, thepresent form is conspecific with Polypora megastoma,
which has a wide distribution.
Polypora sp. indet. A

Figure 6-2

Materia/.-DESC-95101 (Yc21a-9).
Horizon.-Lower part of Eoparafusulina zone
(Aviculopinna horizon) at Yaurichambi-c route.
Description.- This single zoarium consists of straight,
parallel branches connected by robust dissepiments atregular intervals. Bifurcation of branches not observed inca. 15 mm length. Branch width about twice that offenestrule, ranging from 0.800 to 0.960 mm; about 8
branches per 10 mm horizontally. Fenestrules oval in
outline; width ranging from 0.320 to 0.480 mm, lengthfrom 0.800 to 0.960 mm; usually 6 per 10 mm of branch
length. Dissepiments very strong; width ranges from0.580 to 0.960 mm. Zooecial tubes arranged in 5 to 6
rows on each branch, and rhomboidal at middle level ofbranch because of arrangement of very strongly alternating intercalated zooecial tubes in longitudinal series.
Zooecial tubes circular in tangential section near surface,ranging from 0.102 to 0.115 mm in diameter. Number ofzooecial apertures ranges from 18 to 20 per 5 mm lengthof range, usually 6 apertures per fenestrule. Interspaces
between zooecial apertures from center to center range
from 0.243 to 0.282 mm longitudinally. Thick stereom
covers reverse side of branch, consists of semitransparent
layer of colonial plexus with many capillary canals andouter sclerenchyma of dark coarser fibers with many
prominent spicules about 0.025 mm in maximum diameter.
Meshwork formula.-8/6/ /18-20/5-6.
Remarks.- The present form is characterized by robust
dissepiments and many large spicules in the outer sclerenchyma. However, comparison with previously described species is not possible until better preserved
specimens are found.

Polypora sp. indet. B

Figure 6-5

Material. -DESC-95161 (Cu98-1).
Horizon.-Middle part of Pseudoschwagerina zone at
Cuyavi route.
Description.- This single zoarium consists of straight,
parallel branches connected by dissepiments at regularintervals. Bifurcation of branches not observed in thisspecimen. Branch width ranges from 0.576 to 0.640 mm ;12 to 13 branches per 10 mm horizontally. Fenestrules
elongate, elliptical in outline, width very narrow, from 0.160
to 0.256 mm, length from 0.640 to 0.800 mm, usually 9 to
10 per 10 mm length of branch. Dissepiments very short
but wide for the branch, ranging from 0.320 to 0.384 mm.
Zooecial tubes arranged in 4 rows on each branch, moreor less elongate hexagons at middle level of branchbecause zooecial tubes in longitudinal series are not sostrongly alternatingly intercalated. Each row of zooecial
tubes divided distinctly by meandering longitudinal striations. Zooecia circular in tangential section near surface, ranging from 0.102 to 0.115 mm in length, usually 4
apertures per fenestrule. Interspaces between zooecial
apertures from center to center range from 0.281 to 0.320
mm longitudinally. Stereom covers reverse side ofbranch, consists of semitransparent layer of colonial
plexus with several capillary canals and outer sclerenchyma of dark coarser fibers with fine granules.
Meshwork formula.-12-13/9-10/ /18-20/4.
Remarks.- The characteristics of the present form are:each row of zooecial tubes is distinguished by meandering striations; very short dissepiments; and accordingly
very narrow fenestrule.
Polypora sp. indet. C

Figures 7-1,2

Materials.-DESC-95142 (Ma32-1c), DESC-95144(Ma32-3b), DESC-95145 (Ma32-4c), DESC-95146 (Ma325c).
Horizon.-Lower part of Eoparafusulina zone
(Aviculopinna horizon) at Matilde route.
Description.-Zoarium consists of straight, parallel,robust branches connected by dissepiments at regularintervals. Bifurcation of branches not observed. Branchwidth wider than that of fenestrule, ranging from 0.960 to
1.120 mm; usually 6 to 7 branches per 10 mm horizontally.
Fenestrules nearly circular to oval in outline, width ranging
from 0.640 to 0.960 mm, length from 1.120 to 1.280 mm,
usually 6 per 10 mm of branch length. Dissepiments
robust for the branch, ranging from 0.576 to 0.704 mm inwidth. Zooecial tubes arranged usually in 7 rows oneach branch, more or less deformed rhomboids at middle
level of branch because of arrangement of strongly alternating intercalated zooecial tubes in longitudinal series.
Zooecial tubes circular in tangential section near surface,ranging from 0.115 to 0.128 mm in diameter, 20 to 22 per 5mm length of range; usually 6 to 7 per fenestrule. Inter-998. Upper Paleozoic bryozoans from Bolivia, Part 2

Figure 7. 1,2. Polypora sp. indet. C, tangential and transverse sections, x 20, DESC- 95145 (Ma32- 4c)
and DESC- 95146 (Ma32- 5c), respectively. 3,4. Septopora lineata Nikiforova, tangential sections, x 20,
DESC - 95044 (Ya33b- 6) and DESC- 95039 (Ya32b -1), respectively.

275

276

Sumio Sakagami

spaces between zooecial apertures from center to center
range from 0.230 to 0.282 mm longitudinally. Stereom
covers reverse side of branch, consists of semitransparent
layer of colonial plexus with many fine capillary canals
and outer sclerenchyma of rather thin, dark fibers with finegranules.
Meshwork formula.-6-7 /6/ /20-22/7.
Remarks.-The present form can be distinguished by
the nearly circular to oval form of the fenestrules.
Polypora macrops described from the Permian of Timor
Island by Bassler (1929) has also rounded fenestrules, but
it can be easily distinguished from the present form by thelarger number of branches and fenestrules in 10 mm. The
number of zooecial rows across the branch is quite
different; 7 in the present form and 4 in P. macrops.

Family Septoporidae Morozova, 1962
Genus Septopora Prout, 1859
Septopora andeana sp. nov.

Figures 8-1,2Material.-Holotype: DESC-95035 (Ya20a-4); Paratypes: DESC-95036 (Ya20a-5), DESC-95037 (Ya21b-2).
Horizon.-Upper part of Pseudoschwagerina zone at
Yaurichambi-a route.
Oescription.-Zoarium probably fan-shaped, consists ofstraight, nearly parallel branches connected by dissepiments at regular intervals. Branches bifurcated at longintervals. Branch width usually ranges from 0.512 to0.640 mm, occasionally 0.800 mm; 6 to 8 branches per 10
mm horizontally. Fenestrules usually irregular quadrangles with rounded corners or somewhat crescentic, aswide as or wider than branches, width ranging from 0.480
to 0.960 mm; 1.280 mm occasionally, length ranging from
0.640 to 0.800 mm; usually 8 to 9 fenestrules per 10 mm
length of branch. Dissepiments have zooecial tubes,
narrower than those of branches, width ranging from 0.480
to 0.640 mm. Zooecial tubes arranged in 2 rows on eachmain branch, 20 to 22 per 5 mm length of range, parallelogram or elongated quadrate in outline at lower to middle
levels of branch because of no intercalateQ zooecial
tubes in longitudinal series; 5 zooecia per fenestrule.
Usually 10 to 14 zooecial tubes in 2 to 3 rows on eachdissepiment. Diameter of zooecial tubes near surface
ranges from 0.128 to 0.154 mm. Distance between
zooecial apertures from center to center 0.230 to 0.256
mm longitudinally. Nodes in one row on straight carina
and distance between nodes ranges from 0.282 to 0.384
mm; number of nodes per 5 mm unknown. Stereom
covers reverse side of branch and is thin; detailed structures obscure because of secondary mineralization.
Outer sclerenchyma of obverse side consists of coarse
fibers with fine granules.
Meshwork formula.-8/8-9/ /20-22.
Remarks.-This new species seems to be similar to
Septopora subquadrans, described by Ulrich (1890) fromthe upper limestones of the Chester Group in Kentucky

and Illinois, U.S.A. However, the new species can be
distinguished from the latter species in the meshwork
formula (namely 10/10.5//21 in S. subquadrans).
Septopora lineata Nikiforova, 1933

Figures 7-3, 4; 8-3
Septopora subquadrans var. lineata Nikiforova, 1933, p. 28, 29,
pI. 6, fig. 7, text-figs. 9,10.
Septopora diamorpha Loo, 1958, p. 297, 303, pI. 2, fig. 4.
Material.-DESC-95039 (Ya32b-1), DESC-95040(Ya32b-5), DESC-95044 (Ya33b-6b), DESC-95048(Ya34a-8), DESC-95100 (Yc21a-8).
Horizon.-Lower part of Eoparafusulina zone
(Aviculopinna horizon) at Yaurichambi-a and -c routes.
Oescription.-Zoarium fan-shaped, consists of straight,
parallel branches connected by dissepiments having
zooecia at regular intervals. Branches bifurcate at longintervals. Branch width ranges from 0.384 to 0.544 mm ;12 to 16 branches per 10 mm horizontally. Fenestrules
variable in form and size, circular where small in size andirregularly polygonal with rounded or somewhat crescentic
corners when larger; width varying from 0.192 to 0.800
mm, length from 0.384 to 0.576 mm; 11 to 14 fenestrules
per 10 mm of branch length. Dissepiments have zooecial
tubes, are about as wide as the branches, from 0.384 to
0.448 mm. Zooecial tubes arranged in 2 rows on eachmain branch, 21 to 25 per 5 mm length of one range,
parallelogram or elongated quadrate in shape at lower to
middle levels of branch because of no intercalated
zooecial tubes in longitudinal series; usually 3 to 4
zooecia per fenestrule. Usually less than 10 zooecial
tubes in 2 rows on each dissepiment. Diameter ofzooecial tubes near surface ranges from 0.115 to 0.128 mm
and distance between zooecial apertures from center tocenter 0.205 to 0.230 mm longitudinally. Nodes in one
row on well developed straight carina; distance between
nodes ranges from 0.384 to 0.448 mm; 11 to 13 (but 7-8?
in Yc21a-8) per 5 mm of branch length. Stereom covers
reverse side of branch, consists of inner semitransparent
layer of colonial plexus with some capillary canals andouter sclerenchyma of darker fibers with coarse granules.
Meshwork formula.-12-16/11-14/ /21-25.
Remarks.-The present form is similar to Septopora
lineata in its principal measurements and characters. S.
lineata was described originally from the Djulfa region ofArmenia by Nikiforova (1933) from the Gnishik horizon(Lower Guadalupian), and was also described from theLower Permian Chihsia limestone in South China as S.
diamorpha Loo (1958) (Morozova in Ruzhentsev and Sarycheva, 1965).
Septopora incaica (Chronic, 1949)

Figures 8-4, 5Silvaseptopora incaica Chronic in Newell et al., 1949, p. 132;
Chronic in Newell et al., 1953, p. 125-127, pI. 26, figs. 2-8b.

998.

Upper Paleozoic bryozoans from Bolivia, Part 2

Figure 8. 1,2. Septopora andeana sp. nov., tangential sections, x 20, holotype (DESC- 95035 (Ya20a- 4))
and paratype (DESC- 95037 (Ya21b- 2)), respectively. 3. Septopora lineata Nikiforova, tangential section, x 20,
DESC- 95100 (Yc21a- 8c). 4,5. Septopora incaica (Chronic), tangential sections, x 20, DESC- 95041 (Ya34- 1)
and DESC- 95153 (Ma37 (20 cm below)- 3b), respectively.

277

278

Sumio Sakagami

Material.-DESC-95046 (Ya34-1), DESC-95153 (Ma37(20 cm, below)-3b).
Horizon.-Lower part of Eoparafusulina zone at Yaurichambi-a and Matilde routes.
Oescription.-Zoarium widespread, fan-shaped, consists of nearly straight branches connected by dissepiments at regular intervals. Pinnate branches with primaryand secondary patterns. Branch width varies from 0.576
to 0.800 mm; 8 to 10 branches per 10 mm horizontally.
Fenestrules of irregular shape such as polygons withrounded corners, crescentic corners in some cases, narrower than branches, width ranging from 0.320 to 0.480
mm, length from 0.576 to 0.800 mm; usually 7 to 9 fenestrules per 10 mm of branch length. Dissepiments haveusually less than 10 but occasionally more than 10
zooecial apertures in 3 intersecting rows, ranging from0.576 to 0.800 mm in width. Zooecial tubes arranged in
2 rows, occasionally 3 on each branch, 21 to 23 per 5 mm
length of range, elongate quadrate or parallelogram atlower to middle level of branch, because of no intercalated zooecial tubes in longitudinal series; 5 to 6 zooecia
per fenestrule. Diameter of zooecial tubes near surface
ranges from 0.115 to 0.128 mm. Distance between
zooecial apertures from center to center ranges from0.230 to 0.256 mm longitudinally. Nodes in one row on
prominent straight carina; distance between nodes
ranges from 0.576 to 0.768 mm; 7 to 8 nodes per 5 mm
length. Stereom covers reverse side of branch, consistsof inner semitransparent layer of colonial plexus withsome capillary canals and outer sclerenchyma of darker,
coarse fibers with fine granules.
Meshwork formula.-8-10/7-9//21-23.
Remarks.-Chronic (in Newell, 1949, 1953) erected thegenus Silvaseptopora having zoarial characters of Septopora but with the obverse surface heavily covered witherect spines of various sizes. Although the prominent
spines are not observed in the specimens at hand, thepresent form can be identified with the type species of thegenus, namely Silvaseptopora incaica, described from the
Copacabana Group in Peru, in principal measurements
and other characters, especially the zooecial arrangement
in dissepiments. Silvaseptopora is now considered ajunior synonym of Septopora because the generic characteristics described by Chronic do not seem to have taxonomic significance. The present species is not unlike
Septopora robusta, described from the Upper Coal Measures in Illinois by Ulrich (1890), in morphological appearance, but the principal measurements of meshwork are
different, the meshwork formula of the Illinois specimens
being 5-8/7-8//22-23.

Acknowledgments
I would like to express my sincere thanks to Ing. Drs.
Raul Carrasco C., Jorge Arellano L. and Angel Escobar D.,
former staff members of Servicio Geologico de Bolivia, fortheir kind assistance in making the research successful,and to my excellent collaborators: Prof. Juichi Yanagida
and Dr. Takeshi Ishibashi of Kyushu University, Mr. Tet-suya Kawabe and Dr. Yoshihiro Mizuno of Chiba University, Dr. Koichi Nagai of Ryukyu University, Dr. Tomoki
Kase of the National Science Museum (Tokyo) and Mr.
Kiyoshi Okamoto, a former staff member of Agencia de
Cooperacion Internacional del Japon en Bolivia (JICA), fortheir kind help in the field and laboratory work. Special
thanks are due to Prof. June R. Phillips Ross of Western
Washington University for her kindness in reviewing andimproving this manuscript, and to Prof. Tsunemasa Saito
of Tohoku University for his kind help in the preparation of
the manuscript.
The field work in 1980, 1982, 1984 and 1990 of the
Andean region was financed by the Overseas Scientific
Research Fund of the Ministry of Education, Science andCulture of Japanese Government. My sincere thanks arealso extended to the government officials of the Ministry.

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Upper Paleozoic bryozoans from Bolivia, Part 2

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Marsh foraminiferal and vegetation distributions in
Nemuro Bay wetland areas, eastern Hokkaido
DAVID B. SCOTTl, SHIRO HAS EGAWA2 , TSUNEMASA SAIT03, KOJIITO\ and ERIC COLLINS l'Centre for Marine Geology, Dalhousie University, Halifax, NS B3H 3J5, Canada
2Graduate School of Environmental Earth Science, Hokkaido University, Sapporo, 060 Japan
31nstitute of Geology and Paleontology, Graduate School of Science, Tohoku University, Sendai, 9ao Japan
4Department of Biosystem Management, Graduate School of Environmental Science, Hokkaido University, Sapporo,
060 Japan

Received 26 June 1995; Revised manuscript accepted 4 September 1995
Abstract. Although much work has been done on brackish water foraminifera, this is the first reportof modern marsh foraminifera from Japan. Two transects were sampled in marshes of eastern
Hokkaido for salt marsh foraminifera. Although these marshes were tidal, salinities were very low
as evidenced by the freshwater plants that dominated the transects. Foraminifera present were low
in diversity but extremely high in abundance-some of the highest ever recorded for a salt marsh.
Miliammina fusca dominated lower areas together with Trochammina macrescens f. macrescens
which dominated at all levels in both trasects. In the upper elevations of both transects, Haplophragmoides manilaensis became prominent and thecamoebians occupied the upland regions. Vertical
zonation was generally poorly developed in both the foraminiferal and vegetation distributions which
is typical of very brackish regions with low tidal ranges. Many typical brackish foraminiferal species
observed in the Atlantic marshes are either rare or completely absent here.
Key words: Marsh foraminifera, eastern Hokkaido, vegetation zones, foraminiferal zones
Introduction

Previous work

Although a sizeable amount of information on salt
marsh foraminifera is now available from a wide variety of
localities, to our knowledge, no one has previously
examined modern salt marsh foraminifera from Japan.
Many studies have been done on all shallow water environments in Japan by many Japanese workers starting in
the last century but in most cases there was no marsh
associated with the adjacent estuaries. Only in theeastern tip of Hokkaido in rather remote areas, are there
still marshes left in their original state.
Because marsh deposits are now being used extensively to study rapid coastline changes associated with major
earthquakes (Atwater, 1987), we thought it would be
important to document marsh foraminifera in Japan where
major earthquakes have caused significant coastalchanges (Ota, 1992). Marsh foraminiferal zonations may
prove useful in helping to define periodiCity of large
earthquakes in fossil deposits even though there arepresently few living marshes existing on the mainland ofJapan.

As discussed above, Japanese workers have done alarge body of work over the last 100 years. The bestsummary of these works is either in Takayanagi and
Hasegawa (1987) or Nomura (1982). Scott et al. (in press)
have summarized all the Pacific Rim marsh studies, including the data in this paper, and compared marsh
foraminiferal assemblages around the Pacific Rim withthose in the Atlantic.
At the time we sampled this marsh, a group led by M.
Umitsu (Nagoya University) was also working in this marsh
studying diatoms, but we are unaware of any publishedwork from these studies yet.
In terms of overall marsh distribution, Ito et al. (1982)
produced a complete vegetation map of Hokkaido which
we used to locate our sample sites.
Physiography of wetland areas
These salt marshes are located on the eastern tip of
Hokkaido inside Nemuro Bay in the Furen Lagoon (Figure1). The marshes we sampled were on the inside upper
part of Nemuro Bay and had restricted connection to the999.

Modern marsh foraminifera of eastern Hokkaido

283

HOKKAIDO

Figure 1.

Regional map of Hokkaido, northern Japan with the area of Nemuro Bay indicated.

ocean. Although they are tidal, they are almost exclusively freshwater (see vegetation section). We did notmeasure salinities at the time, but Hasegawa returned thisarea in the winter of 1995 and measured salinities of 2.0%0(trans. 1, stn. 1, at lowest marsh), 3.3%0 (6.3 m from stn. 1 intransect 2), 16.9%0 (stn. 1, transect 2), and 16.8%0 (stn 14 intransect 2). These readings were done under ice, so theywould be different than summer values. Tidal ranges at
nearby Kushiro are 0.5 m to 0.8 m (spring) and 0.2 m to 0.3
m (neap). Transect 1 (Figure 2) was the most open of thetwo transects, being located on a large channel that
opens into Nemuro Bay but transect 2 was positioned at
the head of a long channel and was almost at the mouthof the small creek that fed into the area. There weremore marine marshes on the outer edge of Nemuro Bay
but these were inaccessible to us in the time we had
available.

Methods
Samples were collected with a small 3.5 cm diameter
corer-only the upper 1 cm of sediment was collected toobtain a 10 cm 3 sample.
Material was wet sieved within one week using a .063
mm sieve (mesh 230) as the lower size to retain foraminifera and 0.5 mm as the upper size to catch roots andlarge plant fragments. Samples were preserved in buffered formalin and Rose Bengal (to detect living specimens).

284David B. Scott et a/.

Samples were retained in liquid suspension and examinedin liquid under a dissecting microscope (20 to 40 x).
Large samples were split to aliquots of 300-500 specimens using a modified plankton splitter (Scott and Hermelin, 1993).
Organic material was not decanted away as in someearlier studies (e.g., Scott and Medioli, 1980); in somecases, most of the living specimens would have been
washed away by decanting.
Photos of specimens were taken on a Bausch-Lombscanning electron microscope in the Biology Department
at Dalhousie. Plus-x 35 mm film was used.
1 - - - - - - - - - - . . - - - - - - - - - + - 4 3 °16'

Vegetation

145 °20'

Gnerally all the dominant plants were freshwater plants
with some small occurrences of common marsh plants
such as Potentilla sp., G/aux maritima and Triglochinmaritima.
Some of the freshwater species are known from brackish marshes elsewhere (Eleocharis in marshes of theMississippi Delta, Scott et a/., 1991) so it is not too
surprising to see them in what was a tidal situation in the
Hokkaido marshes. Because of access problems, wewere not able to sample the more saline marshes in theouter part of Nemuro Bay (Figure 4) but only upper estuarine areas on the inner part of the Bay (Figures 2, 3).
Transect 1: Characteristic of extremely brackish
marshes like this (e.g. brackish marshes in Louisiana,
Scott et a/. 1991), vegetation patterns followed almost no
pattern with elevation as do saline marshes (Table 1,
Figure 4). Eleocharis kamchatica was dominant in boththe lowest and highest parts of this transect, with varying
amounts of Scirpus, Juncus, Carex, and low percentagesof Potentilla. The only vertical zonation is that trees andupland plants are restricted to the upper marsh.
Transect 2: This transect is similar to transect 1 exceptthat the lowest marsh is dominated by Carex, not Eleocharis, while the highest marsh is again dominated by
Eleocharis (Table 1, Figure 5). The plant diversity of thistransect is higher than in transect 1, notably containing

Figure 3.

Location of Transect 2.

traces of more true salt marsh plants (G/aux and Triglochin) as well as more Scirpus species. Again the only
notable veritcal zonation is in the upper marsh where trees
and other upland plants come in.
Foraminifera

In keeping with the brackish nature of this marsh, theforaminiferal diversity is very low here, and there arepoorly developed vertical zones (Tables 2, 3, Figures 4,5).
Transect 1: This transect was the longer of the twotransects with 31 sample locations (Tables 1,2, Figures 2,4). Sampling for foraminifera started just below thelowest plants and continued into the tree line. In stations
1-20, Miliammina fusca was the most abundant overall,alternating occasionally with Trochammina macrescens f.
macrescens. Living populations follow total abundancesof T. macrescens with greatest numbers of living specimens usually being dominated by T. macrescens. There
are some very high numbers of living specimens at somestations (e.g. Stns. 3, 10 and 23, with over 10,000 living in
a 10 cc sample) and these living populations are invariably
dominated by T. macrescens. From Station 21 to 29, the43 °21' N

43 °20'145 °13" E

Figure 2.

Note coordinates.

145 ° 14"145 °15"

Location of Transect 1.

Note coordinates.

999.

285

Modern marsh foraminifera of eastern Hokkaido

Table 1. Vegetation distributions for Transects 1 and 2.

Transect 2

Transect 1
Stations 1-5 :

50%-80% Eleocharis kamchatica
20%-50% Scirpus sp.
(Station 5 has traces of Juncus andStations 1-3:

85% Garex subspathacea
10% Eleocharis kamchatica
plus Triglochin maritima and Potentilla (5%)

Potentilla)

Stations 4, 5 :Stations 6-9 :

30%-100% Carex subspathaceawith varying %'s of Scirpus, Potentilla,
E. kamchatica (station 6 only), and Juncus
50% E. kamchatica
Station 10:
40% Scirpus sp.
10% Juncus sp.
Trace Potentilla sp.
Stations 11, 12: 50% Scirpus
50% Juncus

Stations 13-20: 0%-60% Scirpus takemaemontani
0%-30% E. kamchatica
10%-100% Juncus (100% at Stn. 16)
0%-50% Scirpus sp.
0%-50% Potentilla sp.
Stn. 18 end of Juncus; First dead trees at
Stn.19Stations 21-23: 85%-95% E. kamchatica
5%-15% Potentilla

50%-80% Calamagrantis epigeious
15%-50% C. subspathacea
Stations 6-10: 50%-95% C. subspathacea
5%-10% E. kamchatica with G/aux maritima
Potentilla sp. and Scirpus sp. also occurring

Stations 11, 12: 40%-50% C. subspathacea
15%-50% Scirpus sp. plus some E. kamchatica and Carex epigeious
Stations 13, 14: 100% Scirpus sp. and S. takemaemontani
Stations 15, 16: 10%-50% C. subspathacea
20%-40% E. kamchatica
plus Poamacrocalyx trautu, Potentilla, Stellaria humifusca, Miscanthus sinensis

Stations 17, 18: 50%-90% E. kamchatica
10%-50% Upland Plants

Plus some Upland Plants; Sediment dry
Station 19:
Station 24:

100% Upland Plants

25% E. kamchatica
70% Scirpus
5% Potentilla

Stations 25-31: 25%-90% E. kamchatica plus Scirpus, etc.
and Upland Plants; Edge of Forest at Stn.
31

fauna changes to one dominated by T. macrescens andHaplophragmoides manilaensis with M. fusca still being

Comparison with other marsh areascommon. At Stations 30 and 31, the fauna becomes
freshwater, dominated by Centropyxis aculeata; thisfauna has low living numbers, as well as lower totals.
Overall total numbers vary from 2 to 19,872/10 cc withliving varying from 0 to 10,908/10 cc.
Transect 2: This transect was shorter and in a more
restricted area than transect 1 (Tables 1,2, Figures. 3, 5).
This is reflected in the foraminiferal fauna which isdominated by T. macrescens throughout its length up to
Station 16 where H. manilaensis becomes prominent.
Above Station 16, C. aculeata is dominant as the upland
plant zone is reached. Together with the dominance ofT. macrescens, numbers of living specimens are generally
higher and fluctuate less than in transect 1. Overall total
numbers are also higher with three stations having over
20,000 individ./10 cc. Ranges are 1 to 9776 individ./10
cc for living and 342 to 27,968 individ./10 cc for total
populations.

The species diversity in the Hokkaido marshes is much
lower than other marsh areas that have been reported,even those with lowered salinities. Several species thatmight have been expected such as Ammotium salsum,
Tiphotrocha comprimata, Ammostauta inepta, Ammobaculites spp., and Haplophragmoides wilberti areeither not present or rare. These have been reported inother brackish marshes (Scott and Medioli, 1980; Scott etal., 1990,1991) but are not here. Scott et al. (in press)
note that some of these species (T. comprimata, A.inepta
and H. wilberti) are not common in any Pacific Rim
marshes, possibly as a result of being away from the main
migratory waterfowl flyways which are probably the mostimportant dispersement mechanisms for marsh foraminifera. However, the Hokkaido marshes are evenmore isolated, lacking the common Pacific species suchas A. salsum. One reason for this might be the generalabsence of salt marsh wetlands in Japan as a whole
which would attract less waterfowl although the nearby
Kushiro area does have a substantial freshwater wetland

286David B. Scott et at.

lRANSECT1
PLANT ZONES

111 2 111

50
40

(%)

3

1

4

6

Hap/ophragmiodes manilaensis

30

20
10
O~---d~-=~

80

(%)

(%)

__~~~~~~~~~~~~~__~~~~~

Miliammina fusca~~

I~tJl_f"Ti~~_en_s--,--,-_~. . ...Och_am......m....lin...a.....;m=ac=<ii"es...

..........-,--,-.......--'--r--"--......-........

......--,...------,NUMBER OF LIVE INDIVIDUALS/1Occ

~~d1
O~

~i

i

15000~TOTALNUMBEROFINDIVIDUALS/1Occ
10000
5000

o

I

o

~

I

100

Ii

150

I

I

200

240

DISTANCE ALONG TRANSECT (m)Figure 4. Foraminiferal and vegetation distributions along Transect 1. Elevations shown are approximate-they are based on .8 m spring tide range with higher high water at the treeline. Vegetation is detailedin Table 1 and foraminiferal data in Table 2. Vegetation zones by number: 1) Eleocharis/Scirpus, 2) Carex +others, 3) Scirpus, Juncus, 4) S. takemaemontani+others (first tree at Stn. 19), 5) Eleocharis+upland plants,
dry soil, 6) Eleocharis+others+upland (forest starts at Stn. 31)

999.

287

Modern marsh foraminifera of eastern Hokkaido
TRANSECT 2
5,JIJ1l I I[[Jill
Trochammina macrescens

(%)

(%)

'~nrI1J]

I~

;~~~I

i

~

10000~NUM8EAOFLiVEINDIVIDUALS/10cc
7500
5000
2500

O~~~--~~~~---r----~~~~~~-r----~~?--------,:=:f[lJ'Nl~
o

10

20

30

40

50

i
60

DISTANCE ALONG TRANSECT (m)Figure 5. Foraminiferal and vegetation distributions along transect 2. Elevations shown are as forTransect 1. Vegetation is detailed in Table 1 and foraminifera in Table 3. Vegetation zones are as follows:
1) CarexjEleocharis, 2) CalamagrantisjCarex, 3) CarexjScirpus, 4) Scirpus, 5) Eleocharisjupland, 6) upland
plants.

288David B. Scott et al.
Foraminiferal abundances and relative percentages for

Table 2.
STATION NUMBER

1

2

3

4

5

6

ELEVATION em ABOVE MSL

-15

0

20

0

0

0

DISTANCE ALONG TRANSECT (m)(live/total)

0
L

NO. OF SPECIESNO. OF INDIVIDUALS

0.5
T

L

1
T

1.5

L

T

L

5.5
T

8.5

L

L

T

T

4

7

4

5

4

4

3

5

3

4

3

3

1314

6588

4464

8688

10896

16872

752

4512

1176

2296

1520

3448

5.5

17.2

4.3

6.1

1.1

2.4

32.9

24.0

33.3

34.3

8.4

11.8

55.3

73.0

40.8

44.6

32.1

38.5

Ammobaculites exiguus
Haplophragmoides manilaensis
Miliammina fusca
Pseudothurammina limnetis

2.2

Tiphotrocha comprimata

0.5

Trochammina inflata

0.3

T. macrescens f. macrescens

56.2

38.3

T. macrescens f. polystoma

43.1

60.2

0.3

89.4

76.8

42.6

49.0

27.2

63.2

37.4

10.2

27.9

4.7

24.1

0.3

Planktonies

Centropyxis aculeata

14.5

0.4
19.4

5.5

14.4

2.2

1.1

2.1

9.0

11.3

C. constricta
Difflugia oblonga

0.7

D. proteiformis
Nebel/a col/aris
Tinnitinnopsis rioplatensis

STATION NUMBER

17
0

50

DISTANCE ALONG TRANSECT (m)

94.5

106.5

(live/total)
NO. OF SPECIESNO. OF INDIVIDUALS

T

L

20

21

22

55

60

65

70

110.5

118.5

125.5

129.5

18

ELEVATION em ABOVE MSL

19

T

L

L

T

L

T

T

T

L

3

4

5

4

5

4

4

3

4

4

5

104

1680

276

1048

316

1012

336

844

1908

15840

1896

3996

1.4

1.9

3.8

4.0

1.2

1.9

0.9

35.4

42.9

43.5

52.7

45.6

53.8

47.6

51.7

0.6

1.2

0.4

Ammobaculites exiguus
Haplophragmoides manilaensis
Miliammina fusca

L

3

46.2

68.6

9.4

1.8

29.8

Pseudothurammina limnetis
Tiphotrocha comprimata
Trochammina inflata
T. macrescens f. macrescens

30.8

1.9

52.2

23.3

44.3

20.9

29.8

22.3

64.2

17.7

62.7

39.6

23.1

29.5

2.9

21.4

6.3

20.9

21.4

24.2

26.4

51.6

1.3

14.4

T. macrescens f. polystoma
Planktonies

Centropyxis aculeata

C. constricta
Difflugia oblonga
D. proteiformis
Nebel/a col/aris
Tinnitinnopsis rioplatensis

0.8

999.
Transect 1.

289

Modern marsh foraminifera of eastern Hokkaido

Also shown are elevation (not accurate) and distance along transect.

7

9

8

11

10

12

15

14

13

16

0

0

0

0

0

0

0

0

0

0

9.5

12.5

17.5

23.5

30

40

53.5

68.5

80.5

86.5

L

L

T

L

T

L

T

3

4

3

5

3

680

3216

152

1224

200

L

T

L

T

5

3

5

3

5

2

1060 10752 17280

584

2256

272

5280

104

5

3

L

T

L

T

L

T

L

T

T

4

4

6

4

4

3

5

1688

2160

5568

5808

7728

88

2176

0.6

9.4

11.2

28.1

53.2

5.5

7.7

63.6

72.1

0.7

0.3

2.4

65.2

28.2

84.8

78.9

9.1

1.8

33.6

5.9

17.5

0.3

2.3

27.3

25.4

0.4

0.6

30.6

36.3

73.3

49.3

84.0

45.3

0.9

3.1

9.4

11.7

0.4

0.6

1.2
63.0

57.8

70.6

37.9

76.9

62.6

0.4

49.4

13.2

15.8

2.3

12.0

3.4

87.1

74.4

31.5

9.9

23.5

4.5

20.0

50.2

10.5

47.7

4.0

51.3

2.2

10.3

5.5

31.6

5.9

55.8

23.1

0.3
0.2

0.3

1.4

0.4
0.3

0.4

23

24

25

26

27

28

29

30

31

45

20

30

40

50

60

70

80

90

133.5

143.5

T

L

4

L

149.5
L

T

4

3

4

10908 19872

416

1872

159.5
L

T
4

169.5
L

T

184.5

T

209.5

198.5
L

T

L

L

T

4

4

5

4

5

4

5

3

4

2

5

0

2

2416

5968

688

1584

520

1704

136

1656

32

1240

0

384

52.9

33.3

13.0

3.8

1.7

17.1

19.5

13.2

18.6

2.3

10.1

6.2

9.9

6.6

16.8

42.3

38.5

2.1

4.6

13.9

14.5

77.9

54.0

18.5

23.5

0.7

12.1

53.8

4.2
0.6

0.3

58.0

T

4480 10000

10.9

81.8

231.5
L

T

0.5

22.2

76.4

68.2

68.2

52.8

16.3

13.1

67.7

37.6

29.4

15.0

37.6

4.3

7.7

4.6

15.8

3.5

22.2

7.7

28.6

17.6

51.2

0.5

25.0

0.5

94.8

1.9
0.6
75.0

1.9

95.8

290

David B. Scott et al.

Table 3. Foraminiferal abundances and relative percentages for
STATION NUMBER

1

2

3

4

ELEVATION IN em ABOVE MSL

0

15

23

31

1

2.5

4.5

DISTANCE ALONG TRANSECT (m)(live/total)

0
L

NO. OF SPECIESNO. OF INDIVIDUALS

T

L

T

L

T

L

T

4

8

3

6

2

7

3

6

1632

11712

3792

11216

944

11312

4224

27968

1.5

0.2

Ammobaculites exiguus

0.8

Haplophragmoides manilaensis

2.0

1.1

Miliammina fusca

3.9

7.1

0.4
0.4
2.5

3.1

3.5

Polysaccammina ipohalina
Pseudothurammina limnetis

0.7

Quinqueloculina seminulum
Tiphotrocha comprimata

0.3

Trochammina inflata
T. macrescens f. macrescens

93.1

86.2

0.5

2.1

1.4

11.9

21.5

36.4

31.1

95.4

92.9

88.1

71.0

62.1

65.2

2.3

T. macrescens f. polystoma
Centropyxis aculeata

1.2

1.6

1.8

C. constricta

0.3

0.6

1.4

Difflugia globulus
D. proteiformis
Lesquereusia spiralis
Nebel/a col/aris
Ammonia beccarii

0.3

Trochammina inflata (sipho-type)

1.0

3.0

STATION NUMBER

11

12

13

14

ELEVATION IN em ABOVE MSL

45

50

55

60

32.8

DISTANCE ALONG TRANSECT (m)(live/total)
NO. OF SPECIESNO. OF INDIVIDUALS

L

L

L

T

L

T

T

3

5

4

5

4

6

5

5

5136

16736

3904

10304

596

6454

9776

16064

50.0

24.8

2.0

3.2

4.3

0.3

1.0

28.6

18.2

78.4

72.2

14.3

45.5

18.7

20.8

5.6

0.7

2.8

Ammobaculites exiguus
Haplophragmoides manilaensis

5.7

14.9

85.1

91.8

67.1

Centropyxis aculeata

2.1

0.8

13.0

C. constricta

0.4

1.6

4.7

2.2

2.4

Trochammina inflata

8.7

10.0

T. macrescens f. macrescens

89.1

Miliammina fusca

40.3

37.3

35.3
T

Polysaccammina ipohalina
Pseudothurammina limnetis
Quinqueloculina seminulum
Tiphotrocha comprimata

0.3

T. macrescens f. polystoma

Difflugia globulus
D. proteiformis
Lesquereusia spiralis
Nebel/a collaris
Ammonia beccarii
Trochammina inflata (sipho-type)

7.1

1.7

999.
Transect 2.

Also shown are elevations (not accurate) and distance along transect.

5

6

7

8

9

10

40

20

25

30

35

40

5

9

12.5

16

26

31.5

L

L

T

291

Modern marsh foraminifera of eastern Hokkaido

L

T

L

T

L

T

L

T

T

2

5

7

7

3

7

3

6

4

7

2

4

2048

14272

5776

11056

4864

25344

6528

31872

4032

11856

9664

21120

0.9

0.3

0.3

0.3

1.0

2.8

2.2

2.5

9.0

2.0

1.8

98.0

93.0

1.3

0.7

4.4

3.3

8.3

20.1
0.1

0.4

0.3

0.3

0.3

0.1

0.3
0.4

0.1

28.1

25.1

1.4

1.6

2.6

4.5

10.8

7.6

1.2

2.3

71.9

71.3

95.0

84.5

96.1

86.4

88.2

74.1

90.1

75.6

0.3

4.2

5.1

10.2

0.3

0.8

1.1

15

16

17

18

19

65

70

80

90

100

45.3
L

48.8
L

T

50.8
L

T

55.8

T

L

59.8
L

T

T

3

6

6

6

3

6

1

4

1

5

5664

10464

1400

2976

66

498

6

828

72

342

5.1

13.4

10.6

40.0

28.2

3.7

9.7

11.8

42.3

33.3

0.6

0.3

2.3

12.9

1.2
5.9

27.3

0.8

73.9
11.0

1.8

1.2

0.5
93.2

6.0

1.2
54.5

9.6

18.2

80.7

100

1.4

1.8

97.1

63.2
1.8

0.5
0.7
0.7

100

31.6

0.6

4.5

David B. Scott et a/.

292

system.
Vertical zonation of marsh foraminiferal assemblages isalso weak here; however Haplaphragmoides manilaensis
does occur mostly in the higher elevations as it does inother locations (Scott and Medioli, 1980; Collins et a/.,1995). Lack of well defined zonations was also observedin the Louisiana brackish marshes where salinities wereless than 10%0 and plant species were largely freshwater
species as they are here (Scott et a/., 1991). However it
is important to note that there is a clear delineation in
Hokkaido between the upland and highest marsh as there
is in every other reported marsh situation.

Ammobacu/ites exiguus (Cushman and Brbnnimann)
Figure 6-1
Ammobaculites exiguus Cushman and Brbnnimann, 1948, p.

38, pI. 7, figs. 7, 8.
Ammobaculites dilatatus Cushman and Bronnimann.

Scott

and Medioli, 1980, p.39, pI. 1, figs. 6-8.

Centropyxis aculeata (Ehrenberg)
Figure 6-9
Arcel/a aculeata Ehrenberg, 1832, p. 91.
Centropyxis aculeata (Ehrenberg). Stein, 1859, p. 43.

Discussion

Haplophragmoides manilaensis Andersen

To our knowledge, this is the first study of recent marsh
foraminifera in Japan; this may in part be due to the totallack of marshes in Japan except for the ones we sampled
in Nemuro Bay. This is also ignoring any work done in
Okinawa on marsh-mangrove systems. However,
although there are very few marshes in Japan presently,
presumably there were extensive marsh systems in thepast before they were reclaimed for agriculture and residential purposes over the last few hundred years. Hence
it is important to know what foraminiferal species to
expect if core or drill hole material in coastal deposits has
salt marsh peats incorporated into the section. As inother areas, the foraminiferal zones can be used toaccurately relocate former sea levels although in thesebrackish marshes the zonation is not as accurate as innormal marine marshes. However it is possible to differentiate tidal marshes from freshwater marshes simply withthe presence of large numbers of foraminifera, somethingthat would not be possible by looking at plants only.
With marsh foraminifera as a tool, it may be possible tolook at coastal deposits in Japan with respect to determining rapid base level changes that result from earthquakes. This technique is already being applied in the
United States and Canada (e.g. Atwater, 1987; Jennings
and Nelson, 1992). Atwater has actually suggested aperiodicity for major quakes in the Washington State
coastline and similar techniques might be very useful tocoastal planners in Japan.

Figure 6-3,4
Haplophragmoides manilaensis Andersen, 1953, p. 22, pI. 4, fig.

8
Haplophragmoides banplandi Todd and Bronnimann, 1957, p.

23, pI. 2, fig. 2: Scott and Mediali, 1980, p. 40, pI. 2, figs. 4,
5.

Miliammina fusca (Brady)
Quinqueloculina fusca Brady, 1870, p.47, pI. 11, figs. 2, 3.
Miliammina fusca (Brady). Phleger and Walton, 1950, p. 280,

pI. 1, figs. 19a, b.
We did not illustrate this species since it has beenreported several times before from Japan (e.g., Takayanagi, 1955).

Nebela collaris (Ehrenberg)
Figure 6-5
Difflugia cal/aris Ehrenberg, 1848, p. 218.
Nebela cal/aris (Ehrenberg). Leidy, 1879, p. 145, 146, pI. 22, pI.

23, figs. 1-7, pI. 24, figs. 11, 12.

Pseudothurammina limnetis (Scott and Medioli)
Figure 6.2
Astrammina sphaerica (Heron-Allen and Earland). Zaninetti etal., 1977, pI. 1, fig. 9
Thurammina? limnetis Scott and Medioli, 1980, p. 43, 44, pI.

1, figs. 1-3.

Systematic taxonomy

limnetis (Scott and Medioli). Scott,Medioli and Williamson, In Scott et al., 1981, p. 126, 127.

Pseudathurammina

For generic distinctions, we follow Loeblich and Tappan(1964,1987). Only the original references are listed here.

Figure 6. Scale bars are by each specimen. 1. Ammobaculites exiguus (Cushman and Bronnimann), side view.
2. Pseudathurammina limnetis (Scott and Medioli), side view. 3, 4. Haplaphragmoides manilaensis Andersen, 3: Side
view, 4: Edge aperture view. 5. Nobel/a col/aris (Ehrenberg), side view. 6-8. Trochammina macrescens Brady, 6: f.
macrescens, ventral, 7: f. polystama, ventral, 8: dorsal. 9. Centropyxis aculeata (Ehrenberg), side view. 10-17.
Trochammina inflata (Montagu), 10: Regular T. inflata, dorsal, 11 : "Sipho" type, dorsal, 12: Regular T. inflata, ventral, 1317: "Sipho" types, ventral showing various degrees of "Sipho" aperture from strongly developed (Figures 16, 17) to lessdeveloped (Figures 14, 15). Except for test composition, specimen 14 would be indistinguishable from "regular" T. inflata(Figure 12).

999. Modern marsh foraminifera of eastern Hokkaido

293

294

David B. Scott et al.

Trochammina inflata (Montagu)
Figure 6-10-17
Nautilus inflata Montagu, 1808, p.81, pI. 18, fig. 3.
Trochammina inflata (Montagu). Parker and Jones, 1859, p.

347.
Illustrations here include "Sipho" type T. inflata (Figures
11, 13-17) which have an extended aperture into the umbilical area. We show a range of specimens here which we
believe shows the intergradation into T. inflata (Figures 10,12). Also note the smaller size of the "Sipho" types; thetexture and size are reminiscent of the microspheric T.
inflata reported in Scott and Medioli (1980).

Trochammina macrescens Brady
Figures 6-6-8
Trochammina inflata (Montagu) var. macrescens Brady, 1870, p.
240, pI. 11, figs.5a-c.
Jadammina polystoma Bartenstein and Brand, 1938, p.381,
figs. 1a-c, 2a-1.
Trochammina macrescens Brady. Phleger and Walton, 1950,
p. 281, pI. 2, figs. 6, 7.

This species includes two forms-forma polystoma (Figure 7) and forma macrescens (Figures 6, 8)-both of which
are illustrated here. As Scott and Medioli (1980) show,
the only difference between the two forms are absence orpresence of supplementary apertures which appears to bea response to salinity. Forma polystoma is very rare inthese Hokkaido marshes.

Acknowledgments
We wish to thank Taro Misumi of the Institute ofGeology and Paleontology, Tohoku University, whohelped with field work. Funding from an NSERC Bilateral
Exchange Grant, with additional support provided by theJapan Society for the Promotion of Science, enabled
Scott to carry out work in Japan and another NSERC
Research Grant to Scott facilitated the completion of thepresent study.

References cited
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Andersen, H.V., 1953: Two new species of Haplophragmoides from the Louisiana Coast. Contributions
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giana, vol. 20, no. 5, p.381-385.
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to marsh floral zones and sea level. Journal of
Foraminiferal Research, vol. 22, p.13-29.
Leidy, J., 1879: Fresh-water Rhizopods of North America.
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Report, vol. 12, p. 1-324, 48 piS.
Loeblich, A.R.Jr. and Tappan, H., 1964: Sarcodina chiefly"thecamoebians" and foraminifera. In, Moore, R.C.
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benthonic foraminifera of Japan, 1925-1981.
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Montagu, G., 1808: Testacea Britannica, supplement, 183
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Parker, WK and Jones, T.A., 1859: On the nomenclatureof the foraminifera, part 2, on species enumerated byWalker and Montagu. Annual Magazine of Natural
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Phleger, F.B. and Walton, W.A., 1950: Ecology of marshand bay foraminifera, Barnstable, Mass. American
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Modern marsh foraminifera of eastern Hokkaido

marsh foraminiferal distributions in Nova Scotia andcomparison with those in other parts of the world:
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no. 17, 58 p.
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M.A., Kuhnt, W. and Scott, D.B. eds., Paleoecology,
Biostratigraphy, Paleoceanography, and Taxonomy ofAgglutinated Foraminifera. p.717-738. NATO ASI
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Trans. Proc. Paiaeont. Soc. Japan, N.S., No. 180, pp. 296-302, 4 Figs., December 30, 1995

"Shelly softground" colonized by an endobyssate
bivalve, Modiolus kurilensis: an example oftaphonomic feedback from the Pleistocene ofKanazawa, JapanYASUO KONDO and NAOKI KIKUCHI
Department of Geology, Faculty of Science, Kochi University, Kochi, 780 Japan
Received 11 January 1995; Revised manuscript accepted 18 September 1995
Abstract. Colonization by an endobyssate bivalve Modiolus kurilensis was possible only in shelly
softground conditions, that is, on a soft bottom with the shells being Slightly buried with fine sediment.
The Pleistocene Omma Formation, Kanazawa, generally exhibits a shelly bottom carpeted by shells(shell pavement) or a shelly bottom covered by soft sediment too thick to allow colonization by
Modiolus. The described Modiolus colony was found in the lower unit of the Om rna Formation, where
sealevel change was relatively small and where shelly softground conditions were present. In
contrast, Modiolus is much less common in the shell beds in the cyclothemic middle unit of theformation. An important environmental factor accounting for the uncommon occurrence of Modiolus
in cycle-bounding shell beds is their repeated physical reworking followed by deposition of soft
sediment too thick to be colonized by Modiolus.
Key words: Shelly softground, taphonomic feedback, bivalve, Modiolus kurilensis, Modiolus modiolus
difficilis, Omma Formation, Pleistocene
Introduction
This note originated from a find of a well-preserved
endobyssate bivalve colony underlain by a shell lens in
the early Pleistocene Omma Formation. Establishmentof the bivalve colony described herein was most probably
facilitated by the presence of shell material on an otherwise barren silty sand bottom which was "difficult forendobyssate bivalves to colonize. In our experience,
gregarious colonies of endobyssate bivalves are notuncommon, an example being those found in the Pleistocene Jizodo Formation, Boso Peninsula. There is,however, no published taphonomical and paleoecologicaldescription of such bivalve colonies. Taphonomicallysimilar examples have been studied by Ziegler et al.
(1966), Walker and Parker (1976), Johnson (1977) andWilson (1982), but for much older Paleozoic brachiopod
colonies.
Kidwell and Jablonski (1983) proposed a concept of
taphonomic feedback for such fossil occurrences, whereby dead hard parts facilitate or inhibit the colonization of asubsequent community. They used the term taphonomic
to emphasize the postmortem processes that figure in theavailability of dead hard parts , and the term feedback toemphasize that not only does the life assemblage influ-

ence the death assemblage (as in conventional taphonomy), but the death assemblage in turn affects thelife assemblages. The concept of taphonomic feedback
is distinguished from "ecological succession" in emphasizing that not only living organisms but also dead hard parts influence subsequent life assemblages. Recognitionand description of such taphonomic feedback are actuallycommon in earlier studies of modern communities or fossil
assemblages. For example, as early as the 1930's,
Powell (1937) discussed substratum modification by accumulating shell and its effect on the distribution ofmarine benthic communities in his study of animal communities in Auckland Harbor in New Zealand. As anancient example, Aigner (1982) discussed modified substratum conditions as an inferred consequence of highenergy events in Triassic shallow marine deposits ofSouthwest Germany, and classified them under softground, firmground and hardground.
Kidwell (1989) thoroughly reviewed the literature describing taphonomic feedback from ancient and modern
marine environments. Also, she tested taphonomic feedback in thick shell beds in the Miocene of Maryland, by
examining relative abundance of shell-gravel dwellers
and shell content in the sediments, and concluded thatthe correlation between them was statistically significant.

1000.

Shelly softground colonized by Modiolus

This paper describes a simpler, but unambiguous example of taphonomic feedback which acted to establish acolony of an endobyssate bivalve in a shallow-marine
environment in the Early Pleistocene of Japan. We also
discuss a characteristic substratum condition termed ashelly softground.
Acknowledgments
We thank R. Majima of Yokohama National University,
T. Kamiya and K. Konishi of Kanazawa University for theirassistance in the sampling of the large fossil concretionused in this study. A. Kitamura· of Shizuoka University
kindly gave us useful information related to this study. I.
Hayami and T. Kase are also thanked for providing information on living Modiolus. Bob Carter of James Cook
University and R. Majima improved this manuscript.
Geologic setting and observation
The bivalve colony was found at the type locality of the
Early Pleistocene Omma Formation, along the River
Saikawa in a suburb of Kanazawa City, on the Japan Sea
coast of central Japan. The Omma Formation is about
200 m thick, and is characterized by at least ten shell-bed
bounded sedimentary cycles, which originated from early
Pleistocene glacio-eustatic sea-level changes (Kitamura
and Kondo, 1990; Kitamura et al. 1994). The middle,
cyclic part of the Omma Formation comprises alternating
shallow (upper sublittoral) and deep (lower sublittoral)
molluscan fossil associations. Also, most of the species
in the upper sublittoral associations are cold sea type andall the constituents of the lower sublittoral associations
are warm sea type, common in the Kuroshio. Such linked changes between water depth and marine climate
clearly suggest a glacio-eustatic origin for the cyclic
environmental change. In contrast, the lower unit of theformation consists of relatively monotonous bluish-gray,partly brown, fine-grained sandstone with sporadic mollusc and echinoid remains and occasional shell lenses
consisting of articulated or disarticulated valves of
Anadara amicula. The Modiolus colony was preserved
resting on one of these shell lenses, stratigraphicallylocated 2.5 m above SB3 (fig. 5, Kitamura, 1991a). In theupper transitional unit to the middle unit of the Omma
Formation, dense shell beds showing characteristics ofstormy condition are present (Kitamura, 1991a). The inferred depositional environment for most of the lower unit
is upper sublittoral, within a cold-water oceanographic
regime.
A concretionary block sample containing the bivalve
colony and of 40 x 50 x 20 cm size was extracted, andbiostratinomic observation of shell orientation and disarticulation ratio was made in the laboratory. The block
sample is deposited in the Department of Geology, Kochi
University.

297

Description of the colony and theunderlying shell lensFigure 1 shows horizontal and cross-sectional views of
the bivalve colony. The bivalve is identified as a living
species, Modiolus kurilensis Bernard 1983. The wellknown synonyms include Modiolus difficilis and Modiolus
modiolus difficilis, and the species is known as "ezohibarigai" in Japanese. Fossils of this species have beenreported from the Pleistocene of South Kanto (Oyama,
1973, and many other papers), e.g. the Miyata Formation in
the Miura Peninsula and the Jizodo, Yabu and Kiyokawa
Formations in the Boso Peninsula, the Pleistocene of
Hokuriku including Omma Formation (Kaseno and Matsuura, 1965), and the Pleistocene of Hokkaido (Sakagami
et al. 1966; Suzuki, 1989). Lenticular concentrations ofmostly unabraded shells of Anadara amicula, an extinct
infaunal arcid bivalve, underlie the Modiolus colony. All
the shell lenses are only one layer thick. Some of theshells are still articulated, but commonly they gape andare stacked with similar orientation or with opposed
postures. No in-situ preserved Anadara specimen was
found in this block (Figure 1), nor in other Anadara shelllenses. The shell lenses of Anadara amicula in the lower
unit of the Omma Formation are, therefore, current-or
wave-worked shell concentrations, rather than an in-situ
occurrence, despite the presence of common articulated
valves and well-preserved shells.
In the sampled block, two individuals (four valves) of
Anadara amicula are articulated among 29 detachedvalves (disarticulation ratio is 86.2%; Figure 2). Shells of
M. kurilensis are often found in the upper part of or justabove the Anadara shell lenses. Thirty-three articulated
specimens and nine detached valves were found. Manyof the Modiolus shells in the block are preserved in life
position with commissure planes roughly vertical and shelllong axes inclined at 60-70 degrees to the bedding plane(Figure 3). The shell surfaces are pristine, with no encrustation or boring.
Lenticular shell concentrations of Anadara amicula areconsidered to have served as the stable substrata on
which the M. kurilensis colony developed. The presenceof Anadara shells made bottom scouring and resultant
reworking less common, thereby permitting colonization
by Modiolus. Just above the Anadara lens, both articulated and detached specimens of Modiolus are scatteredthrough the sediment. Articulated specimens do not
retain their life orientation, and post-mortem disturbanceis inferred at this stage (Figure 4-11), which preceded
formation of the gregarious colony. This is probably
because the Anadara shells were almost exposed on thesea floor or only very shallowly buried, so that Modiolus
individuals were easily reworked on the sea floor.
In the following stage (Figure 4-111), a well-developedcolony consisting of about 20 individuals was established.
Most of the individuals in the colony are preserved in life
orientation, as described above. The underlying shelllayer was buried to a depth of c. 5-6 cm when the colony
was formed, as inferred from the stratigraphic distance298

Yasuo Kondo and Naoki Kikuchi

Figure 1. Photograph of the colony of Modiolus kurilensis .
Scale : the width of the photograph is about 35 cm.

between the shell layer and the reconstructed sea floor
surface from the preserved life positions. This colony did
not, however, continue to grow further (Figure 4- IV).
Modiolus shells do not appear to facilitate successive
colonization of the animal , probably because of the physical instability of a colony which is only supported bybyssal threads. This is a major structural and taphonomic difference with much stable, cement- attachedbivalve colonies formed by bivalves such as oysters.
Several other shell lenses in the same horizon occur
nearby to the colony studied here. These shell lenses
consist similarly of Anadara amicula and M. kurilensis, but
Modiolus specimens were mostly detached and we could
not find in - situ preserved specimens.
Discussions
Ecology of living individuals

According to Habe and Ito (1965) and Okutani (1986), M.
kurilensis is usually found byssally attached to rocksurfaces. Okutani et al. (1989) reported collecting M.
kurilensis with a dredge from a gravelly sandy bottom, butthese authors also considered M. kurilensis to be a
byssally attached , rocky-bottom dweller.
However, the shell morphology of M. kurilensis suggests
otherwise. The shell has a moderately reduced anterior

A: plan view.

B : cross - sectional view.

adductor, and a cylindrical shell form with an anterior lobe,
showing clearly that this species is a soft- bottom endobyssate species, as demonstrated by Stanley (1970,1972) and Seed (1980). Epibyssate species, in contrast,
have a highly reduced anterior adductor inside, a triangular shell form and no anterior lobe. Stanley (1970 ; 1972)
stated that Modiolus modiolus normally lives with
between half to two thirds of its shell buried in stable
gravelly sand. Specimens sampled from the gravelly
bottom reported by Okutani et al. (1989) further confirm
this observation. Judging from Stanley's observation andhis functional analysis, an epifaunal life habit on rocks as
observed by Habe and Ito (1965) and Okutani (1986) is
probably a fortuitous example, and the normal life habit of
the species must be endobyssate. The presence of
encrustation on the postero- dorsal surface of shells of
extant specimens of M. kurilensis stranded on the beachnear Usu- wan, Hokkaido (senior author's personal collection) also supports this interpretation. Specimens dredged from off Wakkanai, near the northern end of Hokkaido,
show sim ilar localized encrustation, suggesting an endobyssate life habit. Stanley (1972) stated that five out of
the eight species of Modiolus which he studied live withpartial or complete burial in a soft substratum, but may
also occasionally be found attached epifaunally to hardsubstrata because of the vagaries of larval settlement,

CONJOINED

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ef
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INCLINATION OF
LONG AXIS

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~

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0

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o
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@horl

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COMMISSURE PLANE@n,..., nnnn~~L" •••• , •••••

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:::J

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UU convex-downFigure 2. Spatial distribution of individuals and their mode of occurrence of Modiolus kurilensis and Anadara amicula. Inclinations ofcommissure plane of conjoined specimens are shown as vertical, tilted and horizontal. For vertical specimen, inclination of the long axis isshown. Distribution of detached specimens is also illustrated. Note the convex-up shell orientation is common for Anadara amicula specimens. M.: a juvenile specimen of Mizuhopecten tokyoensis hokurikuensis, L.: an in-situ specimen of Lucinoma annulata, G.: Gastropoda, M.
k. : Modiolus kurilensis, A.a. : Anadara amicula
N
\D
\D

300

Yasuo Kondo and Naoki Kikuchi

N=18
bedding plane
Figure 3.

Preserved life orientation of Modiolus kur-ilensis.

I

II

III

IV

Figure 4. Schematic representation of stages of theestablishment of the Modiolus kurilensis colony. I: shell
pavement with only one layer thick shells, II: shelly substrate too shallowly covered by soft substrate to be colonized by Modiolus, III: shelly softground, most preferable
condition for colonization by Modiolus, IV: shelly substrate
too thickly covered by soft sediment to be colonized by
Modiolus.

usually tending to lodge in crannies and crevices.
From the above discussion and our observation of thefossil colony, it is concluded that M. kurilensis is basicallya soft-bottom dweller but that establishment of the colony
required the initial presence of stable hard material in thesubstrata. The mode of life of this animal may thus beregarded as a transitional one between soft- and hardbottom dwellers, and it is referred to as a shelly softbottom dweller or shell-gravel dweller.

Environmental conditions for and against colonization,and preservation of Modiolus kurilensis
Modiolus kurilensis is not common in the Omma Formation, according to the stratigraphic distribution chart ofmolluscs in the Omma Formation by Kitamura (1991 b).
This was also confirmed by our observation. Four different environmental factors are discussed below to explain
this.
Modiolus kurilensis is a cold-water species. Climaticchanges concomitant with the eustatic sedimentary
cycles have therefore undoubtedly limited its distribution;
the warmer periods represented by the middle unit of eachcycle probably did not allow colonization by M. kurilensis.
It is thus expected to occur only in cycle-bounding shell
beds for which the marine climate is inferred to have beenreasonably cold (Kitamura and Kondo, 1990).
Also ambient energy level may have affected the distribution of M. kurilensis. Kitamura (1991) reconstructedthat the Anadara-Clinocardium associations in which the
Modiolus colony was included were deposited in a cold
water regime of water depth shallower than 20-30 m in an
embayment. The environmental setting of the middle
unit of the Omma Formation is inferred to have been of
higher energy, as shown by the generally sandier sediment texture and common occurrence of open coast
species such as Macoma sectior and Peronidia venulosa.
Though there is little direct information, it is likely that M.
kurilensis prefers a sheltered environment, because of its
endobyssate mode of life which needs substratum stability.
The physical condition of the substrate is considered
important in the establishment of the Modiolus colony.
Two different shelly substrata may be distinguished:shell pavement (Figure 4-1) and shelly softground (Figure
4-111). Shell pavement refers to a substratum carpeted bya layer of shells. This does provide a stable basis formany epibionts, but it is not suited for moderately large
endobyssate bivalves like M. kurilensis. A shelly softground includes sufficient shell material within the soft
substratum to allow colonization by M. kurilensis. We
need, therefore, to distinguish these two different substratum conditions.
In relation to the above discussion, the mechanism ofdeposition of different shell beds may have determined
the physical characteristics of the substrate and thus
explain the relatively uncommon occurrence of M. kurilensis is the cycle-bounding shell beds of the middle Omma
Formation.
Kitamura and Kondo (1990) demonstrated that the shell
beds bounding sedimentary cycles in the Omma Formation were formed during low stands of sea level during 41
thousand-year glacio-eustatic cycles of the early Pleistocene. Formation of the shell beds is, therefore, theresult of relatively long periods of deposition. However,
Kondo and Kitamura (1988) have pointed out that the shell
beds are often dominated by infauna, which only rarely
show weathering or damage due to Cliona boring or
encrustation by calcareous algae, barnacles or bryozoan.
They therefore concluded that the formation of shell beds

1000.

Shelly softground colonized by Modiolus

involved rapid burial events. These observations are
however not consistent with the general model for shell
accumulation resulting from low rates of sedimentation.
Perhaps the cycle-bounding shell beds were formed byrepetitious storm deposition, and long-term environmental
changes during lowstand of sea-level were thereby stillrecorded.
Accumulated shells were buried in well sorted very finesand immediately after the emplacement event. Reworked shells were buried too deeply to be used as a basis toattach to with a byssus. Consequently, a shelly soft
bottom condition was not available for Modiolus duringformation of the shell beds. In contrast, the shell lensesof Anadara in the lower unit of the Omma Formation are
not associated with a rapid burial event and colonization
was possible.
Kidwell and Jablonski (1983) recognized two types ofshell concentration associated with low net sedimentation; (i) undisturbed reduced sedimentation, which permits nearly continuous maintenance of a shelly substratum (low total sedimentation), and (ii) repeated physicaldisturbance, producing a shell concentration containing
both epifaunal and infaunal taxa (high total sedimentation). The basal shell bed in the middle unit of the Omma
Formation is understood as a further extreme type ofhigher total sedimentation, in which almost no shelly
substratum appeared on the surface during formation of
the shell bed (highest total sedimentation).
In summary, it is concluded that a shelly softgroundwhich could be colonized by endobyssate bivalve wasonly rarely available on the inner shelf muddy sand bottom
during deposition of the Omma Formation.
Lastly preservation is considered to be important inproducing the observed pattern of stratigraphic distribution of Modiolus shell and colonies. Even if a Modiolus
colony was successfully established during deposition ofa cycle-bounding shell bed, it is unlikely to have beenpreserved in situ, because bottom sediment reworking toa depth of 10-20 cm constantly occurred. In fact,
reworking may have reached 50 cm depth, as inferredfrom the analysis of preservation of bivalve life positions.
The relatively uncommon scattered shells of M. kurilensis
which occur in the Omma Formation may represent
reworked and transported shells during such high energy
events.

References cited
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Trans. Proc. Palaeont. Soc. Japan, N.S., No. 180, pp.303-320, 7 Figs., December 30, 1995

Fossil Mollusca of the Lower Miocene Votsuyaku
Formation in the Ninohe district, Iwate Prefecture,
Northeast Japan
Part 1.

General consideration of the fauna

TAKASHIMATSUBARA
Institute of Geology and Paleontology, Graduate School of Science, Tohoku University, Sendai, 980-77 Japan
Received 9 August 1995; Revised manuscript accepted 16 October 1995
Abstract. The fossil Mollusca of the Lower Miocene Yotsuyaku Formation in Iwate Prefecture werestudied and 20 species of Bivalvia, 15 species of Gastropoda and 1 species of Scaphopoda werediscriminated. They are divided into Type I and II assemblages from a paleoecological viewpoint;
Type I is composed of brackish to shallow embaymental elements; Type II indicates middle to lower
sublittoral muddy bottom environments. The assemblage generally changes from Type I to II in
ascending order. Dosinia (Phacosoma) kawagensis Araki, Ruditapes miyamurensis (Itoigawa),
Trapezium (Neotrapezium) modiolaeforme Oyama and Saka, Tateiwaia sp. nov. and Vicaryella"bacula" (Yokoyama) are reported for the first time in the formation. These species seldom occur
in Northeast Japan although they have often been reported from the lower part of the First Setouchi
Miocene Series. Comparison of Type I with brackish to intertidal elements of the Kadonosawa Fauna
of Northeast Japan reveals that characteristic elements of the "Arcid-Potamid fauna" such as
Anadara (Hataiarca) spp. are not found in the formation, and several genera are represented bydifferent species. The Kadonosawa Fauna of Southwest Japan has been divided into the Akeyo andKurosedani Faunas in ascending order. Similar stratigraphic differences in the shallow warm water
marine molluscan fauna from upper Lower to lower Middle Miocene sequences have also beenrecognized in several districts in Northeast Japan. These facts support the conclusion that themolluscan fauna of the Yotsuyaku Formation corresponds to the Akeyo Fauna of Southwest Japan,·and the Kadonosawa Fauna in Northeast Japan is also divided into lower and upper portions.
Key words: Yotsuyaku Formation, Lower Miocene, Northeast Japan, Akeyo and Kadonosawa Faunas
Introduction
Tertiary sequences which yield a lot of molluscs arewidely and thickly distributed in the northwestern marginof the Kitakami Mountains, and many geological andpaleontological studies have been carried out (e.g., Otuka,
1934; Hatai, 1936,1940; Hayakawa et al., 1954; Chinzei,
1958a, b, 1966; Aoki, 1960; Chinzei and Iwasaki, 1967;
Samata, 1976; Maruyama, 1984; Irizuki and Matsubara,1994). As a result, it is well known that the Lower
Miocene sequences have a warm water shallow marine
molluscan fauna, whereas the Middle Miocene
sequences yield a colder fauna. The former is wellknown as the Kadonosawa Fauna (Otuka, 1939,1941;
Chinzei, 1963) which represents tropical to subtropicalenvironments around the Japanese Islands, except fornorthern Hokkaido, around 19.0- or 16.5-15.0 Ma in age(Chinzei, 1978, 1981a, b, 1983, 1986a, b; Tsuchi, ed., 1981 ;Tsuchi and IGCP-114 National Working Group, 1984;
Itoigawa, 1987,1988; Ogasawara, 1988).
The Yotsuyaku Formation is the oldest Neogene in the
district and previous investigators have reported marine
molluscan fossils from its lower part. The molluscan
fossils from the formation were first reported by Yabe
(1921) making reference to the Tertiary geology of Shimizu(1919 MS) (Figure 3). He noted the occurrence of molluscs in Shimizu's "Black Soft Shale" of the Yotsuyaku
Group. Subsequently, Otuka (1934), who studied thegeology and paleontology of the district, introduced the"Koiwai Shell Beds" for the horizon yielding molluscs in
his Yotsuyaku Series. Thereafter, Hayakawa et al. (1954)
and Chinzei (1958a, b) listed some molluscan fossils fromthe formation, but they were neither illustrated nor described. Chinzei (1963,1979) included these molluscs inaddition to those from the overlying Tate Conglomeratic
Sandstone Member of the Kadonosawa Formation as the304

Takashi Matsubara

type Kadonosawa Fauna.
Although the occurrence of molluscan fossils in thisformation is known, the constituents of the fauna are notfully understood. During the present study, it became
clear that the components of the Yotsuyaku Formation are
different from those of the "Kadonosawa Fauna". The
aim of the present study is to describe the molluscan
fauna of the Yotsuyaku Formation and determine thestratigraphic differences from the Kadonosawa Fauna ofNortheast Japan.
Geological setting and age

Tertiary sequences of the Ninohe and Sannohe districts
are divided into two groups, namely, the Shiratorigawa
and Sannohe Groups in ascending order (Chinzei, 1958a,b). These sequences unconformably overlie pre-Tertiary
basement rocks that are distributed on a NW-SE axis in
the eastern and western parts of the study area, andbroadly, they form a gentle synclinal structure plunging
NW (Figure 1). The Yotsuyaku Formation (Hayakawa eta/., 1954) is the oldest Neogene sequence in the district(Figure 2), unconformably overlying or in fault contact withthe pre-Tertiary basement rocks which are composed ofchert, schist and limestone along with plutonic rocks suchas gabbro and granodiorite. In general, this formation iscovered by the Kadonosawa Formation conformably.
The Yotsuyaku Formation consists mainly of irregularalternating beds of mudstone, sandstone and conglomerate with intercalated pyroclastic rocks in its lower andmiddle portions. The formation is divided into five members in ascending order: Matsukura Mudstone, Sandstone and Conglomerate, Nisatai Dacite, Koiwai Mudstone, Sandstone and Conglomerate, Keiseitoge Andesite, and Sugohata Mudstone, Sandstone and Conglomerate Members. Among them, only the Koiwai
Mudstone, Sandstone and Conglomerate Member is ofmarine origin, containing molluscan fossils, while theother members are non-marine, yielding erect stumps andplant leaves; the Nisatai Dacite Member contains nofossils. The thickness of the formation is about 380 m inthe upper course of the Shiratori River. It increases
toward the south and east where the pre-Tertiary basement is distributed. The Sugohata Mudstone, Sandstone
and Conglomerate Member unconformably covers thebasement and the Nisatai Dacite Member, without the
Keiseitoge Andesite and lower members being present, inthe northern and western areas.

The Matsukura Mudstone, Sandstone and Conglomerate Member here proposed is the lowermost unit of the
Yotsuyaku Formation and consists of non-marine clastic
deposits. It corresponds to the "Lower Plant Beds" ofOtuka (1934) or the lower half of the "Koiwai Mudstone,
Sandstone and Conglomerate Member" of Chinzei (1958a).
The member consists of alternating beds of light graymudstone, tuffaceous sandstone and pebble to cobble
conglomerate sometimes with intercalated thin lignite
beds. The type locality of this member is a riverside
exposure on the Shiratori River south of Matsukura,
Ninohe City. The thickness of the member is about 80 m
in the type locality.
The Nisatai Dacite Member here defined consists ofdacitic lava, massive welded tuff and light gray pumicetuff, rich in biotite. This member is mainly distributed in
the northern part of the study area apart from the othermembers, and therefore the stratigraphic position of thisdacitic mass has been controversial (Otuka, 1934; Hayakawa et a/., 1954; Chinzei, 1958a, 1966; Samata, 1976)(Figure 3). However, the present writer could find that the"Nisatai Dacite" overlies the Matsukura Member (column
A in Figure 4), while the basal part of the Koiwai Mudstone, Sandstone and Conglomerate Member includes
cobble to boulder derived from the dacite (column C in
Figure 4). Consequently, the "Nisatai Dacite" is intercalated in the lower part of the Yotsuyaku Formation asshown in Figure 2.
The Koiwai Mudstone, Sandstone and Conglomerate
Member, here redefined, corresponds to the "Koiwai Shell
Beds" of Otuka (1934), or the upper half of the Koiwai
Mudstone, Sandstone and Conglomerate Member ofChinzei (1958a). The name of the member was originallyused for clastic facies overlain by the Keiseitoge Andesite
Member (Chinzei, 1958a), but it is here used for marine
deposits in the lower part of the formation. The member
is composed of dark gray mudstone and bluish graysandstone with conglomerate in the basal part consistingof subrounded to rounded pebbles to cobbles of basement
rocks and dacitic rocks derived from the Nisatai Dacite
Member. The thickness of the member is about 120 m at
the type locality on the bank of the Shiratori River, about
500 m south of Koiwai, Nihohe City. Molluscan fossils
do not occur in the basal conglomerate, but they are
frequently found in mudstone and sandstone, where there
are shell beds.
The Keiseitoge Andesite Member (Hayakawa et a/.,1954) conformably overlying the Koiwai Mudstone, Sand-

Figure 1. Geological map of the study area. Legend; 1-2. Pre-Tertiary Basement Rocks (1. sedimentary andmetamorphic rocks; 2. plutonic rocks); 3-8. Yotsuyaku Formation. (3. Matsukura Mudstone, Sandstone and Conglomerate Member; 4. Nisatai Dacite Member; 5. Koiwai Mudstone, Sandstone and Conglomerate Member; 6-7.
Keiseitoge Andesite Member (6. pyroclastic rocks; 7. intrusive rocks); 8. Sugohata Mudstone, Sandstone and Conglomerate Member), 9-10. Kadonosawa Formation (9. Tate Conglomeratic Sandstone Member; 10. Shikonai Siltstone
Member); 11-14. Suenomatsuyama Formation (11. Anaushi Conglomeratic Sandstone Member; 12. Itsukamachi Sandstone Member; 13. Aikawa Andesite Member; 14. Maisawa Sandstone Member); 15-17. Quaternary deposits (15.
terrace deposit; 16. Towada Volcano ejecta; 17. alluvial deposit); 18. Fault (full line = observed, dashed liQe=inferred); 19. dip and strike; 20. boundary of county.

1001.

1m;
11/,'~\112L:::j3~~

Miocene Mollusca of Yotsuyaku Formation, Part1

5.
····
EJ

LEGEND
6b~:~:~J 7~~~~~~~~~~~~~~

14','...
:".': :

: , . " .,'

305

306

Takashi Matsubara

PL 2)
FORAM.

w

N.9

zw

1 (K-Ar)

0

0

--?-

~

W
...J

C
C

~

u.:
~

N.B

~

~
w

u.

0

.:.:

~

::J

Z
W

0

::J

IV

>
...J
a::

«
W

>-

uncertain

uncertainII)

Matsukura

Mst., Sst & Cg.
Mem.

Figure 2. Stratigraphy of the Shiratorigawa Group in the eastern part of the Ninohe district, Iwate
Prefecture. Biostratigraphic and radiometric data are based on the following studies; lldiatom: Akiba (1977),
Koizumi (1979), Oda et a/. (1983,1984), Maruyama (1984), Irizuki and Matsubara (1994); 21planktonic foraminifera: Samata (1976), Oda et a/. (1983, 1984), Irizuki and Matsubara (1994); 31radiometric age: Kawano and Ueda
(1965), Kimura (1986,1988), Kubo (1987).

stone and Conglomerate Member consists of andesitic
pyroclastic rocks. The lithofacies changes laterally into
volcanic breccia to water-worn tuff breccia and lapilli tuff
and decreases in thickness towards the north of the study
area. Therefore, it is considered that the eruptive vent for
the andesite existed in the southeast of the study area.
The Sugohata Mudstone, Sandstone and Conglomerate
Member (Chinzei, 1958a) occupies the upper part of theformation. It is composed of irregular alternating beds oflignitic mudstone, tuffaceous mudstone and sandstone,
and pebble to cobble conglomerate, consisting of andesite gravels derived from the Keiseitoge Andesite
Member. The conglomerate beds increase in frequency
and thickness towards the south, whereas in the vicinityof the Shiratori River they are rarely found. Maximum
thickness of the member is about 150 m.
The geological age of the Yotsuyaku Formation is still
unclear from a biostatigraphic point of view, althoughsome radiometric ages have been reported. Kimura(1986,1988) reported K-Ar and fission track ages of the
Nisatai Dacite and Keiseitoge Andesite Members are 21.8
and 22.5 Ma for the former, and 15.9 Ma for the latter. In
addition, Kubo (1987) studied the K-Ar age of an andesitic"tuff breccia" correlated to the Keiseitoge Andesite
Member, and obtained a dating of 16.2±2.0 Ma. Further,
the Kadonosawa Formation, covering the formation conformably, is referred to the Crucidenticula kanayae andDenticulopsis praelauta Zones of Akiba (1986) (Akiba,
1977; Koizumi, 1979, 1986b; Maruyama, 1984; Irizuki
and Matsubara, 1994). Judging from these data, theKoiwai Mudstone, Sandstone and Conglomerate Member
with its contained Mollusca is considered to be upper
Lower Miocene. In this study, although diatom fossils
are for the first time obtained from the member, the diatom
zone has not been determined because of the lack ofindex species, poor preservation and lesser frequency

Figure 3. Stratigraphic comparison between the present and previous studies. Two hatched lines in Yabe (1921),
Otuka (1934) and Hayakawa et a/. (1954) indicate formation boundary between the Kadonosawa and Suenomatsuyama
Formations and the upper limit of the Suenomatsuyama Formation of the present study.

1001.

Miocene Mollusca of Yotsuyaku Formation, Part 1: IIIII~aga'l<=~ LUI k I
sands I

F-rm'q;,,;;-.. ····--.A/"~~h'~~

::-

Q)

: Itukamati

ca
3:
ca
II)

Kadonosawa
Gr.

"Ai-

I~SiiiliS be~"c:IA.!!.a~~~ =~ 00 i---~'"0"0ca
Kadonosawa beds~--.-.--- ------TIi:. s& &shaIe:J

MIOOle agglOmerate
TIc. sst. shale & c .
Lower agglomerate
Black soft shale_ ~..!..cg..;,.6.~.~:-. _

~

ca

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:J
II)

0

>-

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Sandstone Mem.

J""'''.AN'.AN'''~E
0c:,,..-JMem.

If ","Mm"'" l~Shl""'"TIc. Sst. Mem.

IMr.mlIsult Meml
ca Q)
~
3: en
~S!&~Memlca

Cs. Sst.
Mem.

fIK~FS~rM
agrton . .-& 1tst. em

Cl

....

-1

Shlkonal Siltstone Mem.

u.:

Nlsiltai LlparHe:J~
upper agglomera eca
5>ca unaceous sanastone OMS :J
Kelseltoge>Lower agglomerate:J.SB Hyperstlne Andesite Mem.
0
Kolwai shell beds0>>- _ _L~e':f'~~!.. .- 1-._

~

:J

ca

~

>-

Sukohata Alternation 01
Mst., Sst. & Cg. Mem.

:J

.SB
0

>-

Kolwal Mst., Sst. &Cg. Mem.

Nisatai liparite

Samata (1976)

This study

f

/~-

~

j ~;~fij= il-~" :~: ka~ ~: " ~.Js~!. . :-~-tN-:-:-.'-d~. .I:-:",.~M: e=:m~'-+. J.,rl~_[J.:~A~nd_AC_:Jks_a-ilW_eJ.a_M-_el_m~\C_J_-_Jc-,sJ.M_a-:_MJ. dsa_:J_~C_:~(9ca

i T~~t_~--.~ ~.8 m ~~JI

sst.

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Shikonai siltstone
Tate sandstone
Sukohata alternation
Keiseltoge~____ .-.-

Q)....:J

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(J)

g

I

~ u.:

Z~

:= )-

'_.-.

n-T rllTTlllTr

M
em.

£?

Shlnaen Md.Sst.
Mem.

Anaushl Cgl. Sst. Mem.

Tate Cgl. S!l~~n_Nisatai F.
Figure 3.

!

Itsukamachl Sst. Mem.

3: 1-+_..,....f~A.;,;.n;;.aus;;;;;;.;h;.,;1c;,,;g:;,;.I..;;S;;.st;;.'M;;,;,;;em.:.:;"J'ca u.:

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Shlkonal Siltstone Mem.

--._--T-at-e-C-g-I.-S-st-.Mem--.-....

fh

t-

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If

~

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II)

.... '"'"'01...1_

Sugohata

I ',..Mst., Sst. &~And. Mem.

Ito.._ _-_-_-_-_-

....,

u.:

l~e,seltoge>-,.ca·. .

.~

u.:
~

andesite
1- ' -Mem~~~ 1

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C:Q)

3: ~
ca en

J
~

Kelseltoge
Andesite & pYroclastic
Mem.

•
-J
- --.---~--- ------ TllTrnlTf
r Tf llrnlT 'nT

Jumonji ( Kawaguchi
sst.
hd. sh.

Eo)Tate Sst. & Cg. Mem.

<~t::.~t.1.I~: ~ ~ N~:::.a:~~ ~ ~:wsa~~~m.
~a~~ g ~ Jumonjl Metokl . , .
<sst. ~ t5
Md. Sst. Calc. Md. Sst. Mlyazawa

\

J

0

ca
....
.(J)

u.:
:J

Chinzei (1966)

i~

Mem.

Shlratorl Sandstone Mem . .c

Upper plant beds

Q)

(J)

'n

(9

TlM~usShikonat Shale Mem.

-. ..!a!!, O!f~ ~d!. .-'.-.--...: ~-------<.9Kadonosawa

TaE&3i CIUlhed tiD mDs-..iTi~T~"'&.l-~~.... 1U~

Sikonai alternation beds

Nakuidakeu.: Andesite
AIM~~
Sst. Mem. Andesiteca&01
Pyroclastic Voe Frcg. Pyro~lastic
Ul

I
I
I

c:

-._..:,--.-...-.
ca...-.----Yuda Gr.
...-.-.- - - ..

F.N'NP~'''''''''''''.·.·

Q)

ArdesIe&IsJlgj

I

0

0

Q)

T~

I

ca
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II)

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ca Sli'nd!::m<i ptrOO. Mem~~d. Sh.
.s:::. II)
0

Tori9Oe

I
I

u.:

-

3"i1TJdanfi Dn.S1st Mem IKawaguchi<5 u.:
32 '~-~.~-~

c:Jumonjl
Mem.
c: E
r
ca
Sst. Mem.
en
H Yuda-Jumonillault I (::. Metoki Shell Sst. Mem. Sst.Iyazawa
Mem.

I KallirrBmiMlaI aggl.

...:

c::--

I JOrni BasaIi: ArDlsIe

Nagarmesam;1 kawa----.------- - - - - - - en-- -~u~nomatsuyama Gr.

Im

MaIOOSaWa
I sands'1

Takamori Gr.

Iu:

Zyumonzl· Yuda
lault

minel

Chinzei (1958a, b)

Hayakawa et al. (1954)

Otuka (1934)

Yabe (1921)

307

1...1...

eg.

Mem.~

KelseltOge
And. Mem.
KolwaiMst.,&t&Cg.Mem

I...: .A:
~ ' - MaIsukura Mst,>-[~~~~~~~""'1"'" ~ 1'1. Sst. & Cg. Mem.

308

Takashi Matsubarac

50m

Keiseitoge

i

f

k

m

9

40

Andesite Member

30
20

Koiwai Mudstone,
7
Sandstone
andConglomerate
Member

10

o

d

17

a

b
. '· :,:· ·Matsukura
Mudstone, Sandstone
and Conglomerate

Basement

MemberFigure 4. Columnar sections for the selected sites in the lower part of the Yotsuyaku Formation (a to m
in Figure 5). Legend: A. tuff braccia; B. volcanic breccia; C. pumice tuff; D. fine tuff; E. dark graymudstone; F. siltstone; G. alternating beds of mudstone and sandstone (mudstone dominant); H. alternating
beds of mudstone and sandstone (sandstone dominant); I. sandstone; J. conglomeratic sandstone; K.
conglomerate; L. talus breccia; M. lignite bed; N. key tuff bed; O. dacite; P. chert; Q. schist; R. fault;
S. fossil horizon.

(Table 1).
Molluscan assemblages and paleoenvironment
Twenty species of Bivalvia belonging to 19 genera, 15
species of Gastropoda belonging to 12 genera, and one
species of Scaphopoda have been identified from 21
localities in the Koiwai Mudstone, Sandstone and Conglomerate Member of the Yotsuyaku Formation (Figure 5,
Table 2). Among them, one species of Bivalvia and twoof Gastropoda are new to science. These molluscs areto be described in Part 2.
a.

Molluscan assemblages
Two types of molluscan assemblage groups are recognized based on co-occurrences and frequency of thecharacteristic species. The first is subdivided into sevenand the other into two assemblages (Figure 6). Of thelocalities, 1, 3 and 16 must be excluded from consideration
because at these localities the molluscs show an allochthonous mode of occurrence.
Type I: Type I is characterized by the following
species: Nipponomarcia nakamurai (Ikebe), Raditapes
miyamurensis (Itoigawa), Hiatula minoensis (Yokoyama),
Vicaryella otukai (Nomura), Tateiwaia sp. nov. and Crassostrea gigas (Thunberg).
la. Nipponomarcia Assemblage: The Nipponomarcia
Assemblage is characterized by the greatly predominantoccurrence of Nipponomarcia nakamurai (Ikebe). Associated species are much less common. This assemblage is often recognized in dark gray mudstone forming
shell beds with thickness of 30 cm to 1 m. It is considered to be the same as the Nipponomarcia Assemblage of
Shibata (1978).

1001.

Miocene Mollusca of Yotsuyaku Formation, Part 1

Figure 5. Locality map of molluscan collections from the Yotsuyaku Formation. (Base map adopted from
Quadrangle "Ichinohe" and "Ibonaj", 1 : 25,OOO-scale topographic map of Japan, Geographical Survey Institute).
Lower left figure indicates the study area illustrated in Figure 1 with dotted areas (A to C) that are enlarged on
the upper (A), middle right (B) and lower right (C) figures, and showing columnar section lines (a to m).

309

310

Takashi Matsubara

Table 1. Diatoms from the Koiwai Mudstone, Sandstone and Conglomerate Member of The Yotsuyaku Formation (identified by Dr. Yanagisawa). Sample number is thesame as locality number of molluscs. + = occurrence.
Species name I Sample nwnber

14a

19

Arachnoidiscus spp.

++

Aulacoseira spp.

+

Coscinodiscus spp.

(fragments)+

lb. Hiatula Assemblage: The Hiatula Assemblage isrecognized by the common occurrence of Hiatula minoensis (Yokoyama) associated with Nipponomarcia nakamurai(Ikebe), Ruditapes miyamurensis (Itoigawa) and Trapezium(Neotrapezium) modiolaeforme (Oyama and Saka) occurring in muddy sandstone.
Ic. Tateiwaia Assemblage: This is the most characteristic assemblage in Type I. It is found in gray tuffaceous muddy sandstone and characterized by thecommon occurrence of Tateiwaia sp. nov. in association
with Nipponomarcia nakamurai (Ikebe) and Ruditapes
miyamurensis (Itoigawa). Difference from the Hiatula
Assemblage is indicated by the frequent occurrence of
Tateiwaia sp. nov. and the higher species diversity.
Id. Dosinia-Cyclina- Vicaryella Assemblage: This
assemblage is characterized by the abundant occurrenceof Dosinia (Phacosoma) kawagensis Araki, Cyclina japonica Kamada and Vicaryella "bacula" (Yokoyama) in association with Meretrix arugai Otuka, Hiatula minoensis(Yokoyama) and others. It comes from tuffaceous muddy
fine to medium-grained sandstone forming shell beds. In
the shell bed, many bivalves are conjoined, their commissure lines are arranged parallel to bedding and they areless water-worn. These features suggest that theassemblage was transported, even though the originalcomposition is preserved. This assemblage corresponds+

Dip/oneis sp.

+

Grammalophora spp.
~-------------------------

Hyalodiscus obsolelus Sheshukova-Porezkaya+

lkebea lenuis (Bnm) Akiba

+

+

---

Paralia sulcata (Ehrenberg) Oeve++

Slephonopyxis spp.

+

+

+

+
---

+

+

(fragments)

Tholassionema nitzschioides (Grunow) H. et M. Peragallo~----------------------

Resting spore of Chaeroceros

IYPE DF A <;t<;tJOMR A

r---

I

I

ASSEMR".AGR
Ia
I
SPECIES NAME I LOCAUfY
Nipponomarcia nalwmurai
Searlesia kurodai
Ruditapes miyamurensis
Crassostrea gigas
Hiarula minoensis
Tareiwaia n. sp.
t-Trapezium (Neorrapezium ) modiolaeforme-Solen sp.
Vicaryella orukai"Ocenebra" n. sp.
Dosinia (Pluu:osoma) kawagensis
Vicaryella "bacula"
Cyclina japonica
Macoma (Macoma) incongrua
Nassarius (Zeuxis) sp.
Yoldia (Yoldia) aff. omorii Aoki
Boreotrophon sp.
Cultellus izumoensis izumoensis
Mya sp.
Miv.dwpecren aff. chichibuensis mitsuganoensis

Ib

~4

I-R

I 2

Id
10

Ie
Jl~

If

8a

19
9

IT
ITa
14a 114b I 19

lIb
17

I--

-

-

~

-

I--

I--

-

I--

LEGEND_FIe
7 I 12 I 18 I 11_C

_AFigure 6. Molluscan assemblage of the Matsukura Mudstone, Sandstone and Conglomerate Member of
the Yotsuyaku Formation. See text for explanation of the assemblages (Ia to g and lIa to b). Abundance data
as for Table 2.

1001.

Miocene Mollusca of Yotsuyaku Formation, Part 1

311

Table 2. Molluscan fossils from the Koiwai Mudstone, Sandstone and Conglomerate Member of the
Yotsuyaku Formation. Abundance data: R=rare (1-3 specimens); F=few (4-9); C=common (10-19); A=
abundant (20-29); VA=very abundant (>29). .: these new species are to be proposed in Part 2.
Species name I Locality

I

2

3

4

5

7

6

8a

8b

9

10

11

12

13

14a

14b

F

F

15

16

17

18

19

BIVALVIA
Yoldia (Yoldia) aIr. omorii Aoki
MkuMp«~nC

R

aIr. chkhiblUlllSis miLsugtl1UWlSis (Shibata)Anomia chinensis Philippi
CnusoS1n4 gigas (l"bunberg)
Lucinoma cr. tJCIIli/iMaIa (Cauad)~-------------------Pillucino (WtJlbu:ino) cr. striata (I"okuoaga)

R

F

-

F

-

F

-

F

F

R

R

C

R

F

F

- - - R- - -

F
F

-

R

R

R
R
-t-- t-- t-- f - - ; - -R-- -- - - --R

F.umwJa,",""inDID (Makiyama)
ClJnocardIum .p.

RR

Mocoma (Macoma) iN:ongl'lllJ (v. MaIIens)

R

R

HioJuItJ miIIoMJis (Yokoyama)~-------------------Sow. .p.

-

-

F

R

R
R

-

R

F

R

- R- -

R

R

R

R

C

C

-

R

-

F

-

R

F

- R-

F

C

-

R

R
~-

R

TrtIpo:ium (Nl!Olrt1{J01.iMm ) modiDlMfo,."", Oyama and Sska

CF~-------------------RudJtiJpa mi)VJlfUU'....is (iroigawa)-R -R R- R- C- R- F- R-

N"1{J(1OfIOtIIIUC naItumurai (Ikebe)

A

F

F

R

R

R

F

R

R

C

VA

F

-

R

R

-

R

R

R
C

R

R

F

C

F

--- -- -C
R

A

C

VA

VA

- f - - f-- f-- f-- - -

R

C

R

R

R

R

-- -- -- -- -- - - --F
R

R

F

C

F

R

cu/t.uus kUlfUH!nsis iVUftO<!nsis Yokoyama
TrtJ{1<1ium (/'I1!01rtlp<dum ) D. sp.'

Do.iNa (Phocosoma) kawagMSis AIlIki

F

F

R

R

F

Muetrixaragai 0Iuka
CydinojtJpollica KamadaCC

Mya sp.

F

R

F

R

GASTROPODA
HomoIopoma aIr. .,.. (iroigawa)

R

CtmIIta1idJu ap.

R

R

LiIIoriNJ sp.
Crl!pidldajiJrl/JooNJ Yokoyama

TdIeIwaia D. ap.'~-------------------~ aIf. ~nsis (itoigawa)RA- - - -

Vit:aryflla "bacula" (Yokoyama)F

VIaJrydla sp.

R

1f00000000Jl D. &p.•--------------------

R

-

-

R

F

s.mIaia I;urldai
NtU.rDriMS (Zew:I.r) sp.

R

R

-

VA

A

A
R

-

F

- - - R-F

VIctIryolla DIMkDi (Nomura)

Plio. (Plio.) nolOellSis Masuda

R

R

R

R

F

C

R

R

C

-

F

C

VA

A

F

R

VA

-t-- t-- t-- t-- -- -- -- -- -- R

C

R

R

R

F

R

F

R

R

R

R

F

R

F

- - - - - - - R- R- f--- -- -- -- -- -- -R
F
R

R

~-

R
R

R

R

R

R

R

R

R
C

lkJrootrop/rorI sp.

R

R

AdtImnmia ap.

R

R

F

R

F

R

R

C

F

C

R
R

SCAPHOPODA
c-.idmItJliwft7 sp.

to the Vicaryella bacula-Cyclina or Cyclina Assemblage of
Shibata (1978).
Ie. Cyclina Assemblage: The Cyclina Assemblage isdefined by the common occurrence of Cyclina japonica
Kamada in situ, and associated with Vicaryella "bacula"(Yokoyama), Tateiwaia sp. nov., Hiatula minoensis (Yokoyama) and CerithideopsiIJa aff. minoensis (ltoigawa).
Difference from the Dosinia-Cyclina- Vicaryella Assemblage is indicated by the lack of Dosinia (Phacosoma)
kawagensis Araki.
If. Vicaryella- Tateiwaia Assemblage: This assem-

Fblage is characterized by abundant occurrences of suchgastropods as Vicaryella "bacula" (Yokoyama), Tateiwaia
sp. nov. and Vicaryella otukai (Nomura), associated with afew other bivalve species. These species are crowded indark gray mudstone.
Ig. Cerithideopsilla-Dosinia Assemblage: This
assemblage consists of CerithideopsiIJa aff. minoensis(ltoigawa), Dosinia (Phacosoma) kawagensis Araki, Hiatulaminoensis (Yokoyama) and Trapezium (Neotrapezium)
modiolaeforme Oyama and Saka and comes from muddy
coarse-grained sandstone showing conspicuous biotur-

Takashi Matsubara

312

bation and included plant remains.
Type 1/: Type II is indicated by the occurrence of Mya
sp., Yoldia (Yoldia) aff. omorii Aoki and Boreotrophon sp.
in a massive muddy facies and by the lack of the main
constituents of Type I.
lIa. Nassarius- Yoldia Assemblage: The NassariusYoldia Assemblage is characterized by the common
occurrence of Nassarius (Zeuxis) sp. in association withYoldia (Yoldia) aff. omorii Aoki, Mya sp., Boreotrophon sp.
and Cultel/us izumoensis izumoensis (Yokoyama).
lib. Macoma Assemblage: This assemblage is indicated by the sporadic occurrence of only three species;
Macoma (Macoma) incongrua (v. Martens), Mizuhopecten
aff. chichibuensis mitsuganoensis (Shibata) and Mya sp.
b.

Paleoenvironment

The assemblages forming Type I involve Ruditapes
miyamurensis (ltoigawa), Nipponomarcia nakamurai(Ikebe), Hiatula minoensis (Yokoyama), Tateiwaia sp. nov.,
and Crassostrea gigas (Thunberg) in addition to Vicaryel/aspp., Cyclina japonica Kamada, Dosinia (Phacosoma)
kawagensis Araki and Cerithideopsil/a aff. minoensis(Itoigawa). They are considered to have inhabited brackish to intertidal environments in an embayment. Of theseassemblages, the Nipponomarcia and Vicaryel/a- Tateiwaia Assemblages are found in dark gray mudstone andthe Cyclina Assemblage comes from tuffaceous siltstone,
while the other assemblages are obtained from tuffaceous
muddy sandstone.
On the other hand, Type II is characterized by Mya sp.,
Yoldia (Yoldia) aff. omorii Aoki and Boreotrophon sp.,occurring in dark gray mudstone, and by lower richness
and diversity than Type I. Except for Nassarius (Zeuxis)sp., Macoma (Macoma) incongrua (v. Martens) andClinocardium sp., components of Type I are not found in
Type II fauna. Therefore, it is evident that the elementsof Type II lived at greater depth than Type I. Judging
from the occurrences of Mizuhopecten aff. chichibuensis
mitsuganoensis (Shibata), Cultel/us izumoensis izumoensis Yokoyama and Macoma (Macoma) incongrua (v. Martens) in this type, the elements of Type II are likely torepresent a middle to lower inner sublittoral muddy bottom
environment.
The molluscan assemblages change from·, Type I to II
vertically, except in the vicinity of the type locality of the
Koiwai Mudstone, Sandstone and Conglomerate Member,where the change is not recognized. These facts indicate that the depositional environment of the member
changes from brackish-intertidal to shallow sublittoral
marine embayment environments in ascending order.
Subsequently, the member was completely covered bypyroclastic deposits of the overlying Keiseit6ge Andesite
Member.
Characteristic of the molluscan fauna of the
Yotsuyaku Formation and its significanceThe molluscan fauna of the Yotsuyaku Formation has
been considered equivalent to the Kadonosawa Fauna, as

already mentioned. Otuka (1939) first designated as its
type the molluscs from the lower part of his "Kadonosawa
Series" studied by him (1934), and discussed its temporaland spatial distribution. He considered that the fauna
was lower Miocene in age. The name "Kadonosawa
Fauna" was used for the first time by Kanehara (1936), who
discussed the temporal and spatial distribution of the"Ennichi (Yeongil) Fauna" of Korea, and pointed out thatthe fauna closely resembles the molluscan fauna of the·"Kadonosawa Series" studied by Otuka (1934). Chinzei(1963,1978, 1981a, b, 1983, 1986a, b), Tsuchi, ed. (1981) and
Tsuchi and IGCP-114 National Working Group of Japan(1984) reviewed the distribution of the fauna with reference
also to planktonic microfossil biostratigraphy andradiometric ages, and the Kadonosawa Fauna was considered to be restricted in its occurrence to the interval
16.5-15.0 Ma, or latest Early to early Middle Miocene.
Thereafter, Itoigawa (1987,1988) and Ogasawara (1988)
revised the geological distribution of the fauna and suggested that the lower limit of the fauna may attain 19.018.5 Ma in several Pacific coast regions based on planktonic microfossil biostratigraphic and radiometric data.
In addition, Chinzei (1983, 1986a, b) revealed the northward succession of the Kadonosawa Fauna. He subdivided the distribution into three biogeographic provinces
based on sublittoral taxa; tropical, subtropical and amixed area with the temperate- to cold-water Chikubetsu
Fauna. According to him, the first is characterized by
Telescopium, Geloina and Littorinopsis, considered to be
representatives of mangrove swamp dwellers as reported
by Oyama (1950). The second is represented by the"Arcid-Potamid Fauna" (Tsuda, 1965; Noda, 1973), consisting of such genera as Anadara (Hataiarca), Vicarya,
Tateiwaia, Cerithideopsil/a and Cerithidea, with Hiatula
and Cyclina. These genera also occur in the tropicalprovince.
In the Tate Conglomeratic Sandstone Member of theKadonosawa Formation, the type formation of the fauna,
Chinzei and Iwasaki (1967) recognized Batil/aria, Ostrea,
Dosinia-Clinocardium, Felaniel/a-Conus and Macoma
Assemblages and discussed their paleo~cology. In addition, Matsubara (1995) reported on the occurrence of the"Arcid-Potamid Fauna" such as Anadara (Hataiarca) kakehataensis Hatai and Nisiyama, Megaxinus khataii (Otuka),
Cyclina japonica Kamada, Hiatula minoensis (Yokoyama),
Vicaryel/a otukai (Nomura), and Tateiwaia cf. yamanarii(Makiyama) from the member in Nisatai, Ninohe City.
These components are included in the Batil/aria Assemblage (Chinzei, 1981a, b). The Batil/aria (= Tateiwaia; thewriter's taxonomical ranking) Assemblage of Chinzei andIwasaki (1967) is composed mainly of Tateiwaia tateiwai(Makiyama) or T. yamanarii (Makiyama), Macoma(Macoma) cf. incongrua (v. Marten), Hiatula minoensis(Yokoyama), Megaxinus khataii (Otuka), and Ringicula
ninohensis Otuka. It occurs in a black muddy sandstonefacies and is considered to inhabit a brackish lagoon or
tidal flat environment. Consequently, it is believed thatthe Hiatula, Tateiwaia, Dosinia-Cyclina- Vicaryel/a andCerithideopsil/a-Dosinia Assemblages in Type I of the1001.

313

Miocene Mollusca of Yotsuyaku Formation, Part 1

Table 3. Specific comparisons of the constituents of the "Kadonosawa Fauna" between lower (left) andupper (right) horizons in selected districts. Data for each district is based on the following studies: Mizunami
district; Itoigawa (1960), Itoigawa et al. (1974,1981,1982), Joban Coalfield; Kamada (1962,1972), Takahashi(1984), Noda et al. (1989), Ninohe district; Otuka (1934), Chinzei and Iwasaki (1967), Chinzei (1979), Matsubara(1995 and unpublished data), Southwest Hokkaido; Uozumi and Fujie (1966), Kanno et al. (1988) and Suzuki etal. (1992,1994).
GENUS!
RlRMATiON
Tateiwaia

TSUKIYOSHIsp.

SHUKUNOHORANINOHEJOBAN COAL-FIEI.D

MIZUNAMI

DISTRIcr

KUNUGIDAIRANAKAYAMA

yamanorii

yanrtJ1IQrii(=n. sp.)

n. sp.
"bocuIa""

ishiiana

nolDensis (1)KADONOSAWA
yanrtJ1IQrii
taleiwai

Ialeiwai

ant:isa (1)~-(~i-

SOl.J"ffiWEST HOKKAIDOYOSHIOKA
cf. yanrtJ1IQrii

KUNNUJ
yanrtJ1IQrii------------- ~--------

notoensis;,;.;,,-g;;;;is- --- -- s-"t~;';"is- -----j------------- d~ ;.d;j·o;;;"is- --- ';;'-;';;'i;,;.,t; ----- ------- ------ -- --- ---- ---- ------ --- --otukai

otukai~-(p~~-)-

YOfSUYAKU

nomurainomurainomurainomuraiotukainorruuai

nonuuai------------- ------------~;;~~~~~~~ ~{~~~~~ ;;~~~~~~1~~~~~~~ ~~~~~~~~~~~ ~~~~~~~ ~!~~~~~~~~ ~~~~~~~~~~~~~ g~~~~~~~
CyclinajDponica

jDponica

jDponica

jDponica

jDponica

Iunu/ata

jDponica

jDponica

Iunu/ata-------------- arugoi------------- arugoi------------ ------------------------- arugoi------------ ------------------------- -----------arugoi
arugoiarugoiM<ntrix

ninoMnsis

VicaryayokoyamtJi

yokoyamtJi-------------- ------------- dDito/cudoensis------------

Anodtua(Hak1iorca)

yokoyomoj

yokoyomoj
cf. kokeluztaensis""~""

Yotsuyaku Formation faunas from the muddy sandstonefacies correspond to the Batillaria Assemblage of theKadonosawa Formation based on lithology and components.
Considering the comparison, the components of the
Yotsuyaku Formation are characteristic in lacking not only
tropical elements but also Anadara (Hataiarca) spp., characterizing the "Arcid Potamid Fauna", and composed ofdifferent species constituents to the Kadonosawa Fauna
of Northeast Japan. For example, different species arerecognized in such genera as Tateiwaia, Vicaryel/a and
Ruditapes, whereas Hiatula minoensis (Yokoyama), Meretrix arugai Otuka, Vicaryel/a otukai (Nomura), and Cyclina
japonica Kamada are found in both formations (Table 3).
In addition, it is noteworthy that Nipponomarcia nakamurai (Ikebe), Dosinia (Phacosoma) kawagensis Araki,
Ruditapes miyamurensis (Itoigawa), Trapezium (Neotrapezium) modiolaeforme Oyama and Saka, Tateiwaia
sp. nov. (=Batillaria yamanarii of Mizuno, 1964, from the
Isomatsu Formation of Aomori Prefecture and Tateiwaia
sp. of Itoigawa et al., 1981 and 1982, from the Tsukiyoshi
Member of the Akeyo Formation of Gifu Prefecture), andVicaryel/a "bacula" (Yokoyama) are for the first timereported from the Yotsuyaku Formation, because these
species show a pronounced resemblance to those of thelower part of the First Setouchi Miocene Series of Southwest Japan. They have been seldom reported from theJapan Sea side, nevertheless upper Lower-lower Middle
Miocene deposits with the Kadonosawa Fauna are widelydistributed (Figure 7-1). For example, in addition toreports from Southwest Japan, Dosinia (Phacosoma)

kawagensis Araki has been reported only from the Ajiri
Formation of Miyagi Prefecture and the Shiote Formationof Fukushima Prefecture (Masuda, 1963) in addition to the
Sinhyeon Formation of Eoil district, Korea, where thespecies is associated with the "Arcid-Potamid Fauna"(Yoon, 1979) (Figure 7-2). However, co-occurrence ofthe present species in the "Arcid-Potamid Fauna" was notreported in the First Setouchi Miocene Series (Shibata,1978; Itoigawa et al., 1974,1981,1982), and its geographic
areas very little overlap that of the "Arcid-Potamid Fauna"(Figures 7-1,2).
Itoigawa (1987) proposed the Akeyo Fauna and emphasized that it is distinguished from the Kadonosawa Fauna(s.s.) (=the Kurosedani Fauna in his usage) on differencesin its constituents, lacking typical tropical elements, andin its older geological age. He considered that thesuccession from the Akeyo to the Kurosedani Faunas
occurred by shifting of warm currents around Southwest
Japan, producing a change from subtropical to tropicalmarine conditions with migration in tropical elements.
Detailed geological age determination of sequences in theFirst Setouchi Miocene Series yielding such molluscs isstill unclear biostratigraphically in many districts. Saito(1963), Koizumi (1981) and Ibaraki (1981) studied the biostratigraphy of the upper part of the Mizunami Group andsuggested that it correlates with the upper half of Zone
N. 8 of Blow (1969) and the Denticulopsis lauta Zone.
Yoshida (1987a, b, 1991) revealed that the age of the Awa,
Ichishi, and Fujiwara Groups and the Chikusa Formation
corresponds to Zone N. 7 and the lower half of Zone N. 8
based on planktonic foraminiferal biostratigraphy. In

314

Takashi Matsubara

Figure 7. Comparison of the geographic distribution of the "Arcid-Potamid Fauna" and characteristic species of the
Yotsuyaku Formation.
Fig. 7-1. Geographic distribution of Anadara (Hataiarca) spp. in latest Early-early Middle Miocene terms (modified
from Noda and Takahashi, 1986). 1. Kunnui F. (Noda and Takahashi, 1986; Kanno et al., 1988), 2. Babagawa F. (Suzuki
et al., 1994), 3. Tsurikake F. (Uozumi and Fujie, 1966), 4. Maenokawa F. (Iwai, 1960, 1965), 5. Kadonosawa F. (this study),
6. Oyama F. (Ogasawara and Nagasawa, 1992), 7. Myozawabashi F. (Sato et al., 1989), 8. Iwafune F. (Tsuda, 1965), 9.
Tsukinoki F. (Ogasawara and Noda, 1978), 10. Nakayama F. (Takahashi, 1984), 11. Asagawa F. (Noda, 1973), 12.
Tamagawa F. (Noda, 1973; Noda et al., 1994), 13. Orito F. (Kobayashi and Ueda, 1991), 14. Higashiinnai F. (Masuda, 1955,
1966),15. Kurosedani F. (Hatai and Nisiyama, 1949; Tsuda, 1960), 16. Sunakozaka F. (Sasaki and Ogasawara, 1986), 17.
Kawaminami F. (Bito et al., 1980), 18. Kunimi F. (Kaseno, 1956; Nakagawa, 1989), 19. Shimo F. of Uchiura Gr. (Nakagawa
and Takeyama, 1985; Ozawa et al., 1986), 20. Yoshino F. of Katsuta Gr. (Taguchi, 1981), 21. Bihoku Gr. (Okamoto andTerachi, 1974; Taguchi et al., 1979), 22. Toyoda F. of Masuda Gr. (Takayasu, 1981), 23. Shukunohora Facies of Akeyo
F. of Mizunami Gr. (Itoigawa et al., 1974,1981,1982; Okumura, 1983), 24. Kanayama F. (Yokoyama, 1923), 25. Kawachi
F. of Kukinaga Gr. (Hayasaka, 1969), 26. Pyonryug F. of Meongcheon Gr. (Makiyama, 1926), 27. Cheongogsa F. in
Pohang district (yoon, 1976a, b; Lee, 1992), 28. Songjeon F. in Eoil district (Kim et al., 1974; Lee, 1992), 29. Sinhyeonand Hwabongri Fs. in Uisan district (Yoon, 1979; Lee, 1992).
Fig. 7-2. Geographic distribution of Dosinia (Phacosoma) kawagensis Araki.
1. Yotsuyaku F. (this study), 2. Ajiri F. (Masuda, 1963), 3. Shiote F. (Masuda, 1963), 4. Tomikusa Gr. (Shibata, 1978),5. Toyama F. of Mizunami Gr. (Shibata, 1978), 6. Akeyo F. of Mizunami Gr. (Itoigawa, 1955,1960; Itoigawa et al., 1974,
1981,1982), 7. Shitara Gr. (Shibata and Ina, 1983), 8. Okazaki F. (Hayashi and Miura, 1973), 9. Chikusa F. (Hata, 1967;
Shibata, 1978), 10. Awa Gr. (Shibata, 1978), 11. Ichishi Gr. (Araki, 1960; Shibata, 1970,1978), 12. Ayugawa Gr. (Shibata,1978; Muramatsu, 1992), 13. Tsuzuki Gr. (Itoigawa, 1956; Shibata, 1978), 14. Yam abe Gr. (Shiida and Shibata, 1968), 15.
Shimosato F. of Kumano Gr. (Honda et al., 1995), 16. Sinhyeon F. in Uisan district, Korea (Yoon, 1979).

addition, Hayashida and Ito (1984) and Hayashida (1986)
studied the paleo-magnetostratigraphy of the Ichishi and
Mizunami Groups. They correlated the middle to upper
part of the Ichishi Group and the Hongo and Akeyo
Formations of the latter group to Epoch 16.
In Northeast Japan, similar stratigraphic differences inthe shallow marine molluscan fauna of the upper Lowerlower Middle Miocene sequences have been pointed out
in the Joban Coalfield of Fukushima Prefecture andsouthwest Hokkaido. For instance, in the Joban Coalfield, it is well known that Vicarya and Vicaryella species
have been reported from two horizons separated by thickmarine deposits. Kamada (1960,1962,1972) recorded
these genera in the Kunugidaira Formation of the
Yunagaya Group and the Nakayama Formation of the"Shirado Group" in ascending order, with each formation
containing a different species of Vicaryella; Vicaryellajobanica Kamada in the former formation and Vicaryellaishiiana (Yokoyama) in the latter. Later, Takahashi (1984)
for the first time reported the occurrence of the "Arcid-

Potamid Fauna" in the Nakayama Formation. He also
concluded that the Vicarya species occur in exactly the
Kunugidaira and Nakayama Formations, and that themolluscs of the Kunugidaira Formation, lacking Anadara
species, should be included in the "Ashiya Fauna".
Masuda (1973) believed that the two formations accumulated in a short time and may be correlated with theformations yielding the Kadonosawa Fauna in other district. As a result of the development of planktonic
microfossil biostratigraphy, the lower limit is still unidentified, but the geological age of the Yunagaya, "Shirado"and Takaku Groups in the Joban Coalfield is estimated to
be 20 or 18 to 15 Ma (Koizumi, 1986a; Yanagisawa et a/.,1989; Taketani et a/., 1990; Yanagisawa, 1993). Noda
et a/. (1989) examined molluscs from the Taki Formation(= the Kunugidaira Formation) and pointed out that theelements of this formation correspond to shallow embayment assemblages of the Kadonosawa Fauna, althoughlacking anadaran species. The Shiote Formation, noted
above, is considered to be a correlative of the Kunugidaira

100l

Miocene Moll usca of Yotsuyaku Formation, Part 1

Formation (Fujita and Tsujikawa, 1960; Suzuki, 1963;
Kubo et al., 1990).
Recently, Suzuki et al. (1992) briefly discussed themolluscan fauna of southwest Hokkaido and recognized
three Miocene molluscan fossil stages; Yoshioka (18-17Ma), Kunnui (16-15 Ma) and Yakumo Stages (12-7 Ma) inascending order (Table 3). They considered the molluscan fauna of the first stage to be comparable with the
Akeyo Fauna of Itoigawa (1987,1988) and to indicate awarm to temperate climate based on the lack of subtropical elements such as Vicarya and Vicaryella, while thesecond stage is characterized by the "Arcid-Potamid
Fauna".
The shallow marine molluscan fauna of the lower
horizon of these two districts is characterized by lacking
the "Arcid-Potamid Fauna" which is found only in theupper horizon as in the case of the First Setouchi Miocene
Series and the Ninohe district. In addition, such changes
have not been recognized in the reverse order. Considering these facts, the molluscan fauna of the Yotsuyaku Formation corresponds to the Akeyo Fauna of Southwest Japan and the Kadonosawa Fauna of Northeast
Japan is also divided into the Akeyo and Kadonosawa
Faunas (s.s.) stratigraphically.

Acknowledgments
The present writer would like to express his deep
appreciation to Prof. Kei Mori of the Institute of Geology
and Paleontology, Graduate School of Science, Tohoku
University, for his supervision of this study and continuous
encouragement. Sincere appreciation is also due to Prof.
Kenshiro Ogasawara, Institute of Geoscience, the University of Tsukuba, for his valuable suggestions on the EarlyMiddle Miocene molluscan faunas, and to Prof. JA
Grant-Mackie of the Department of Geology, the University of Auckland for his critical review of the manuscript.
The writer is also deeply indebted to Dr. Yukio Yanagisawa of the Geological Survey of Japan for identificationsand valuable suggestions on diatom fossils. Drs.
Masanori Shimamoto and Osamu Sasaki gave manysuggestions in the course of the field survey, and thepresent writer also wishes to thank them.
In the course of the field survey, the writer used 1 : 5,000
scale "Kitakami-sankei Kaihatsu Chosa-Zu" (Maps for
Exploration of Kitakami Mountains) presented by the
Iwate Prefectural Government.

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Tsuda, K., 1965: Neogene molluscan assemblages in the
Inner Zone of northeast Japan; with special reference to the Middle Miocene assemblages. Fossils(Palaeontological Society of Japan), no. 10, p. 18-23.

Akeyo Ejiji!t, Awa JlOJ11tl, Chikubetsu ~5jU, Fujiwara JIii*, Hongo ;2fs:*Illl, Ichinohe -p, Ichishi;6;, Joban Coalfield m-~ ER EEl, Kadonosawa r~ tR, Keiseitoge jlJj:iJilttllt, Koiwai IN5/., Kunnui wI[$i, Kunugidaira ff'FjZ, Kurosedani ~JjfiJj:e-, Matsukura t.t}~, Mizunami lffiiiN, Nakayama 9=I ill,
Ninohe =]5, Nisatai 1={tl!Z, Sannohe =]5, Setouchi Miocene Series JjfiJj]5P'39=I~*1t, Shiote:tg=.F, Shiratorigawa B,~JII, Sugohata ){)(:I:IH, Takaku fl'ij~, Tate ti'i, Tenmyosan ~Ejijill, TsukiyoshiFl]§", Yakumo J\~, Yoshioka ]§"/lilj, Yotsuyaku 1Z9'/1~, Yunagaya ~~:e-.

/Postscript: After the manuscript was completed, the following studies treating the late Early to early Middle
Miocene warm water molluscan fauna were publi-

shed.
Yabe, A., Ogasawara, K, Uemura, K. and Obuse, A., 1995:

320

Takashi Matsubara
Plant and molluscan fossil assemblages from theLower Miocene Kunugidaira Formation in the southern part of the Joban Coal-field, Japan. Journal of
the Geological Society of Japan, vol. 101, no. 7, p.
532-548. (in Japanese with English abstract)

Ozawa, T., Inoue, K., Tomida, S., Tanaka, T. and Nobuhara, T., 1995: An outline of the Neogene warm-watermolluscan faunas in Japan. Fossils(Palaeontological Society of Japan), no. 58, p.20-27.
(in Japanese with English abstract)Trans. Proc. Palaeont. Soc. Japan, N.S., No. 180, pp. 321-335, 5 Figs., December 30, 1995

Fossil Mollusca of the Lower Miocene Yotsuyaku
Formation in the Ninohe district, Iwate Prefecture,
Northeast Japan
Part 2 (1).

Bivalvia and Scaphopoda

TAKASHIMATSUBARA
Institute of Geology and Paleontology, Graduate School of SCience, Tohoku University, Sendai, 980-77 Japan
Received 9 August 1995; Revised manuscript accepted 16 October 1995
Abstract. Twenty species of Bivalvia and 1 species of Scaphopoda, obtained from the Koiwai
Mudstone, Sandstone and Conglomerate Member of the Yotsuyaku Formation, are first describedherein. Of these, one bivalve, Trapezium (Neotrapezium) ichinohense, is new to science.
Key words: Yotsuyaku Formation, Lower Miocene, Bivalvia, Scaphopoda, systematic description,
Trapezium (Neotrapezium) ichinohense sp. nov.
Introduction
In this article and the following Part 2 (2), the writerdescribes molluscs from the Yotsuyaku Formation listed
in Part 1 with revision of some species. The descriptions
provide fundamental data for the conclusions reached inpart 1. All specimens described and illustrated here aredeposited in the Institute of Geology and Paleontology,
Graduate School of Science, Tohoku University, under the
IGPS (abbreviation for the institute) collection catalogue
numbers.
Systematic descriptions and remarks
Class Bivalvia
Subclass Paleotaxodonta
Order Nuculoida
Family Nuculanidae
Genus Yo/dia Moller, 1842
Subgenus Yo/dia s.s.
Yo/dia (Yo/dia) aft. omorii Aoki, 1954
Figures 1-2-4
Resembles. Yoldia omorii Aoki, 1954, p.30, 31, pI. 2, fig. 18.
"Nuculana omorii" (Aoki). Uozumi, 1957, pI. 7, fig. 11.
Yoldia (Yo/dia) omorii Aoki. Kamada, 1962, p.59, pI. 2, figs.

gated, small and poorly inflated shell with smoothly
rounded anterior and slightly upturned, acutely angled
rostrate posterior margins; shell surface sculptured withclose, fine concentric growth lines; poorly elevated beakis situated at about the anterior two-fifths. The specimens closely resemble Yoldia omorii Aoki, 1954, originallydescribed from the early Middle Miocene Kabeya Formation (=Numanouchi Formation of Kamada, 1962), Fukushima Prefecture. However, Y. omorii difters in having abeak situated centrally.
Locality.-14a (No. 102564), 14b, 19 (No. 102565).
Measurements (in mm).IGPS Coil.
Cat. No.

Height

Bp'

Bp/Length

16.5
7.5
102564102565-1
19.2
8.7
102565-2
24.8
11.0
22.1
102565-3'beak position fro anterior end

6.5
7.5
9.8
8.9

0.394
0.391
0.395
0.403

Valve
Right
Left
Left
Right

Subclass Pteriomorphia
Order Pterioida
Family Pectinidae
Genus Mizuhopecten Masuda, 1963
Mizuhopecten aft. chichibuensis mitsuganoensis(Shibata, 1970)
Figures 1-11, 17a, b

17,18.
Remarks.-Many poorly preserved specimens wereobtained. They are characterized by a transversely elon-

LengthResembles. Patinopecten kobiyamai Kamada.

11. [not of Kamada, 1954J

Araki, 1960, p. 83, pI. 5, fig.

322

Takashi Matsubara

Patinopecten (Mizuhopecten) chichibuensis mitsuganoensis
Shibata, 1970, p. 63, 64, pI. 1, figs. 14a, b, pI. 2, figs. 1a, b.

Oescription.-Shell small in size, suborbicular, higher
than long, subequilateral except for auricles, weakly inflated; apical angle about 70 on younger part, increasing
to 90 with shell growth; shell surface sculptured withradial ribs and fine concentric growth lines; right valve
with seven low, rounded radial ribs; interspaces nearly
equal to or slightly narrower than ribs and flat-bottomed;
fine distinct radial striae on crest and flanks of ribs;
anterior and posterior ribs fine and bifurcated; anteriorauricle longer than posterior and sculptured with five toseven radial threads and concentrical growth lines;
byssal notch deep; posterior auricle inclines to anteriorand sculptured by two or three radial ribs and fine concentric growth lines; left valve has five nearly flat-topped
radial ribs that are narrower that their interspaces; interspaces sculptured with obtuse microscopic network;
crest and flanks of ribs and interspaces ventrally carry fineradial threads; auricles as for right valve except for lackof byssal notch. Inner side of shell is not observed.
Remarks.-Single left and two right valves without shellmaterial were obtained.
Comparison.-Mizuhopecten chichibuensis mitsuganoensis (Shibata, 1970), originally described from the
Mitsugano Tuffaceous Sandstone and Shale Member ofthe Katada Formation, Ichishi Group of Mie Prefecture,
resembles the present species, but is distinguished bypossessing more elevated radial ribs on the left valve, anobtuse microscopic network over the whole of both
valves, and smaller anterior auricles. The present
species is similar to "Kotorapecten" egregius (Itoigawa,1956) in having large anterior auricles and a deep byssal
notch, but is distinguished by having fewer radial ribs. It
also resembles Mizuhopecten chichibuensis chichibuensis (Kanno, 1957), described from the Nenokami Sandstone Member of the Ushikubit6ge Formation in Saitama
Prefecture, but differs in its smaller size, larger anteriorauricle, deeper byssal notch on the right valve, andmicroscopic network only on interspaces of the left valve.
0Mizuhopecten kobiyamai (Kamada, 1954) is distinguishedfrom the present species by possessing a larger shell,
more inflated right valve, roof-topped radial ribs on the left
valve, and imbricated radial threads on the ventral area.
Locality.-17 (No. 102568).

0

Measurements. IGPS Call.
Length Height Apical angle Number of Valve
(mm)
(mm)
radial ribs
Cat. No.
nRight102568-1
32.5
36.1
92
7
Left
102568-2
32.5
33.9
90
5
95
7
Left
17.8
16.4
102568-3

Family Anomiidae
Genus Anomia Linnaeus, 1758

Anomia chinesis Philippi, 1849
Figures 1-7a, b, 16a, b
Anomia chinensis Philippi. Kuroda, 1932, appendix p. 120 ;Habe, 1953, p. 198, 199, pI. 27, fig. 12, pI. 28, fig.21;
Hayasaka 1961, p.33, pI. 3, fig.7; Matsushima, 1969, pI.
10, fig. 4; Hayasaka, 1969, p. 42, pI. 2, figs. 3a, b; Kuroda
et al., 1971, p.590, pI. 84, figs. 12-14, p. 378; Shibata in
Itoigawa et al., 1974, p.71, pI. 15, figs. 5-7b; Ogasawara,
1976, p. 46, 47, pI. 1, fig. 19, pI. 4, fig. 9; Itoigawa et al.,
1981,1982, p.50, pI. 9, figs. 7a, b; Shibata and Ina, 1983,
p.42, pI. 4, fig. 8; Masuda et al., 1983, p.11, pI. 1, fig. 21 ;Ogasawara et al. eds., 1986, pI. 31, figs. 9a, b; Shibata etal., 1987, pI. 1, fig. 3; Kobayashi, 1987, pI. 2, fig. 6; Saba,
1990, p.257, pI. 28, fig 4; Masuda et al., 1990, pI. 1, figs.
4A, S; Nakagawa et al., 1993, p. 33, pI. 15, figs. 2a, b;
Noda et al., 1993, p. 143, 145, figs. 16-9a, b; Okumura andTakei, 1993, p.167, pI. 35, fig. 7; Noda et al., 1995, p.59,
figs. 7, 15 and 17-19.
Anomia cytaeum Gray. Yokoyama, 1920, p.146, pI. 11, figs.
17a, b; Kuroda, 1932, appendix p.120, fig. 122; Nomura,
1935a, p.107, pI. 11, figs. 5, 6; Nomura and Hatai, 1936, p.
121; Nomura, 1938, p.251, pI. 35, fig. 7; Nomura andHatai, 1938, p. 49, 50; Nomura, 1940, p. 21, 22, pI. 2, fig. 14.
Anomia lischkei Dautzenberg and Fischer. Makiyama, 1927,
p. 37; Kuroda, 1932, appendix p. 119, fig. 121; Ozaki,1958,

Figure 1. (All figures natural size, unless otherwise stated).
1a-b,5. Pi/lucina (Wal/ucina) cf. striata (Tokunaga), Loc.7, IGPS coil. cat. no. 102571, x1.5, right valves. 2,3,4.
Yoldia (Yoldia) aff. omorii Aoki, 2: Loc. 14a, IGPS coil. cat. no. 102564, silicon rubber cast, right valve, 3: Loc. 19, IGPS
coil. cat. no. 102565, left valve, 4: Loc. 19, IGPS coil. cat. no. 102565, silicon rubber cast, left valve (internal surface). 6,
22. Solen sp., 6: Loc.18, IGPS coil. cat. no. 102581,22: Loc. 11, IGPS coil. cat. no. 102580, right valves. 7a-b,16a-b.
Anomia chinensis Philippi, Loc.13, IGPS coil. cat. no. 102569, left valves. 8. Felaniel/a ferruginata (Makiyama), Loc.15,
IGPS coil. cat. no. 102574, left valve. 9,10,14, 15a-b. Macoma (Macoma) incongrua (v. Martens), 9: Loc. 19, IGPS coil.
cat. no. 102596, left valve, 10: Loc.3, IGPS coil. cat. no. 102581, left valve, 14: Loc.18, IGPS coil. cat. no. 102582, left
valve, 15a-b: Loc. 12, IGPS coil. cat. no. 102583, 15a: Right valve, 15b: Left valve. 11,17a-b. Mizuhopecten aff.
chichibuensis mitsuganoensis (Shibata), Loc.17, IGPS coil. cat. no. 102568, 17a: silicon rubber cast, right valve, 11 and17b: Left valves. 12,18. Clinocardium sp., Loc.14b, IGPS coil. cat. no. 102576, silicon rubber cast, 12: Left valve, 18 :Right valve. 13. Lucinoma cf. acutilineata (Conrad), Loc. 14a, IGPS coil. cat. no. 102572, silicon rubber cast, right valve.
19. Cultel/us izumoensis izumoensis (Yokoyama), Loc.14a, IGPS coil. cat. no. 102578, left valve. 20,21. Hiatulaminoensis (Yokoyama), 20. Loc.10, IGPS coil. cat. no. 102587, left valve, 21: Loc.11, IGPS coil. cat. no. 102586, rightvalve. 23. Crassostrea gigas (Thunberg), Loc.lO, IGPS coil. cat. no. 102566, left valve.

1002.

1aMiocene Mollusca of Yotsuyaku Formation, Part 2 (1)

2

1b

3

323

4
5
6

7a

8

7b

9

10

11

12

13

16a

16b

14

15a

15b

18
17b

22

23

324

Takashi Matsubara

p.119, pI. 24, fig. 5; Kamada, 1962, p. 71, pI. 3, figs. 8-11.
Anomia nipponensis Yokoyama, 1920, p. 146, pI. 11, figs. 18a, b.
Remarks.-Several well preserved specimens were
examined. Anomia chinensis from the Yotsuyaku Formation is characterized by its rather small size, suborbicularthin shell with the left valve moderately inflated. Innerside of left valve has an orbicular plug scar below thebeak and two suborbicular adductor muscle scars arranging obliquely below the plug scar (as illustrated by Habe,
1953).
Locality.-5, 8a, 8b, 13 (No. 102569).
Distribution. Recent: South Hokkaido and more southern northeast
Pacific coast.
Quaternary: Otanoshike F. in Hokkaido, Sasaoka F. in
Akita Pref., Dainenji F. in Miyagi Pref., Omma F. in
Ishikawa Pref., Kazusa Gr. in Chiba and Kanagawa
Prefs., "Kozakai Mud" in Aichi Pref., Takahama Shell
Bed in Fukui Pref.
Pliocene: Daishaka F. in Aomori Pref., Tatsunokuchi F. in
Miyagi Pref., Hitachi and Kume Fs. in Ibaraki Pref.,Kakegawa Gr. in Shizuoka Pref.
Middle Miocene: Utsuno F. in Yamagata Pref., Kubota F.
in Fukushima Pref.
Upper Lower-lower Middle Miocene: Taira F. of the
Yunagaya Gr. in Fukushima Pref., Oshimoj6 and Arakida Fs. of the Tomikusa Gr. in Nagano Pref., Sunakozaka F. in Ishikawa Pref., Akeyo F. of the Mizunami Gr.
in Gifu Pref., Kawakado and Shimoda Fs. of the Shitara
Gr. in Aichi Pref., Nenobi Granule Conglomerate andHiramatsu Sandstone and Siltstone Fs. of the Awa Gr. in
Mie Pref., Okuyamada and Yuyantani Fs. of the Tsuzuki
Gr. in Kyoto Pref., Kurokawa F. of the Ayugawa Gr. in
Shiga Pref., "lower formation" of the Bihoku Gr. in
Okayama and Hiroshima Prefs., Kawachi F. of the
Kukinaga Gr. in Tanegashima Island, Kagoshima Pref.

Family Ostreidae
Genus Crassostrea Sacco, 1897
Crassostrea gigas (Thunberg, 1793)

Figures 1-23; 4-12
Ostrea gigas Thunberg. Tokunaga, 1906, p. 68, pI. 4, figs. 5a,b; Yokoyama, 1920, p.162, pI. 15, figs. 1, 2; Otuka, 1934,
p. 610; Otuka, 1935, p. 885; Makiyama, 1936, p. 206,
207; Nomura and Onisi, 1940, p. 182; Iwai and Siobara,
1969, pI. 1, figs. 14a, b, pI. 2, fig. 1.
Ostrea (Crassostrea) gigas Thunberg. Kuroda, 1930, appendix
p. 55, 56, fig. 56; Nomura and Hatai, 1937, p. 126, 127, pI.
18, fig. 3; Hirayama, 1954, p. 57, 58; Habe, 1955, p. 8, 9,
pI. 4, figs. 15, 16; Ozaki, 1958, p. 118, 119, pI. 21, fig. 7 ;Fujie, 1958, p.35, pI. 27, figs. 22, 32; Hayasaka, 1960, pI.
38, figs. 1a, b, 2; Habe, 1960, p. 5, pI. 5, figs. 14, 15; Araki,
1960, p. 81, 82, pI. 11, figs. 1a, b; Hayasaka, 1961, p. 34, 35 ;Oyama, 1973, p.89, pI. 29, figs. 1, 4, pI. 30, figs. 2a, b;
Noda, 1973, pI. 5, fig. 6.
Ostrea gravitesta Yokoyama. Nomura, 1938, p. 248, 249, pI.
33, fig. 15. [not of Yokoyama, 1926b]

Crassostrea gigas (Thunberg). Habe, 1960, p. 5, pI. 5, figs. 14,
15; Matsushima, 1969, pI. 10, fig. 5; Kuroda et al., 1971, p.
596, pI. 86, fig. 1, p. 382; Torigoe, 1981, p. 304, 305, pl.2,
fig.1, pI. 14, figs.1-7b, pI. 32, figs. 1, 2; Matsushima,
1982a, pI. 3, figs. 1, 2; Matsushima, 1982b, pI. 2, fig. 6, pI.
3, fig. 3; Amano, 1983, p.43, pI. 2, figs. 2, 5; Masuda etal., 1983, p. 11 ; Matsuura, 1985, pI. 33, figs. 9a, b; Takayasu, 1985, pI. 2, figs. 11, 12a, b; Takahashi, 1986, pI. 13,
fig. 3; Kobayashi, 1987, pI. 2, fig. 18; Matsushima andNara, 1987, pI. 1, figs. 1a, b, pI. 2, figs. 2a, b; Matsukuma
et al., 1988, pI. 3, fig. 6; Nakagawa et al., 1989, p. 33, 34,
pI. 16, figs. 1a-d; Baba, 1990, p. 262, pI. 29, fig. 9 ;Masuda et al., 1990, pI. 1, fig. 3; Noda et al., 1993, p.145,
147, fig. 16-8; Amano, 1994, pI. 1, fig. 19.
Remarks.-Many well preserved specimens wereobtained. Although those from the Yotsuyaku Formation
are of medium size with a less inflated right valve possessing less elevated radial ridges compared with Recent
specimens, these differences are considered to fall within
the range of intraspecific variation for C. gigas.
Comparison. -Crassostrea mundana (Yokoyama, 1924),
originally described from the Oligocene Iwaki Formation in
the Joban Coalfield, closely resembles the present material, but is distinguished by possessing a broader
ligamental groove and numerous finely undulating radialstriae on the left (upper) valve. Crassostrea gravitesta(Yokoyama), a well known Miocene oyster from Japan and
Korea, differs in its much larger size and robust, thickshell.
Locality.-1, 3, 4, 5, 6, 7, 8a, 8b, 10 (No. 102566), 11 (No.
102595), 12,13,15,18 (No. 102567).
Distribution.- This species is distributed throughout thecoast of Sakhalin, Japan, Korea, China and Southeast
Asia in the Recent (Trigoe, 1981), and there are many fossil
records from Lower Miocene and younger strata around
Japan and in several districts of Korea. From upper
Lower-lower Middle Miocene sequences, it is known fromthe following: Kadonosawa and Suenomatsuyama Fs. in
Iwate Pref., Kanagase F. in Miyagi Pref., Kobana F. of the
Arakawa Gr. in Tochigi Pref., Oshimoj6 and Arakida F~. ofthe Tomikusa Gr. in Nagano Pref., Ochiai Facies and Oi F.
of the Ichishi Gr., Hiramatsu Sandstone and Siltstone F. of
the Awa Gr. in Mie Pref., Okuyamada and Yuantani Fs. of
the Tsuzuki Gr. in Kyoto Pref., Lower Manhondong (Mankod6) F. of the Meongcheon (Meisen) Gr. in North Korea.

Subclass Heterodonta
Order Veneroida
Family Lucinidae
Genus Pillucina Pilsbry, 1921
Subgenus Wallucina Iredale, 1930
Pillucina (Wallucina) cf. striata (Tokunaga, 1906)

Figures 1-1a, b, 5; 2Compared with.Lasaea striata Tokunaga, 1906, p. 53, 54, pI. 3, figs. 14a, b.
Lucina contraria Dunker. Yokoyama, 1920, p. 134, pI. 10, fig. 8? Pillucina contraria (Dunker). Otuka, 1934, p. 616, pI. 48, figs.

1002.

Miocene Mollusca of Yotsuyak u Formation , Part 2 (1)325

Genus Lucinoma Dall , 1901

Lucinoma cf. acutilineata (Conrad, 1849)
Figure 1-13

Figure 2. Hinge area and inner margin of right valve of
Pillucina (Wallucina) cf. striata (Tokunaga) from the Yotsuyaku Formation (IGPS coil. cat. no. 102571). Same specimen
as Figures 1- 1a, b. Scale bar = 2 mm.

37, 38.
"Lucina " contraria Dunker. Otuka, 1935, p. 892, pI. 57, figs.
190, 191
Wallucina lamyi Chavan. Yamamoto and Habe, 1959, p. 91 , pI.
6, figs. 28, 29; Hayasaka, 1961 , p. 40, pI. 4, figs. 4a, b ;Yoon, 1988, pI. 1, figs. 18- 20; Ogasawara et al. eds., 1986,
pI. 72, figs. 2a- c.
Pillucina (Wallucina) lamyi (Chavan). Kaseno and Matsuura
1965, pI. 13, fig. 3.
'
Pillucina (Wallucina) striata (Tokunaga). Kuroda et al. , 1971, p.
611, pI. 118, fig . 15, p. 392; Oyama, 1973, p. 69, pI. 40, figs.
3a, b; Matsuura, 1977, pI. 3, fig. 15; Ogasawara et al.
eds., 1986, pI. 72, figs. 3a, b.
Pillucina striata (Tokunaga). 8aba, 1990, p. 263, pI. 29, fig . 12.
Remarks. - The specimens from the Yotsuyaku Formation are characterized by the following features: shell ofsmall size, suborbicular or subtrigonal in form, inequilaterai , moderately inflated ; rather distinct keel extends frombeak to posteroventral margin ; anterior margin wellrounded ; posterior margin subtruncate; shell surface
sculptured with concentric growth lines and numerous
microscopic radial threads over the whole surface; lunule
small but well impressed; inner margin finely crenulated
e~cept along hinge plate. As shown in Figure 2, thehinge area of the right valve possesses a strong
subtrigonal tooth and nodulous, strongly elevated anterior
and posterior lateral teeth .
Comparison . -The specimens closely resemble Pillucina (w.) striata (Tokunaga, 1906), a living species , but
are distinguished by having a more inflated shell. Pillucina (Wallucina) habei (Itoigawa, 1955b), originally described from the Kubohara Sandstone Member of the
Toyama Formation of the Mizunam i Group in Gifu Prefecture, resembles the present species, but is distinguishedby possessing a higher.shell with a less produced anterior
margin. Pillucina (Wallucina) okumurai proposed by Itoigawa (1957) may be distinguished from the present species
by having a less truncated posterodorsal margin.
Locality.- 2 (No. 102570), 7 (No. 102571).

Compared with .Lucina acutilineata Conrad. Otuka, 1934, p. 614 ; Hatai, 1940,
p. 125 ; Nomura and Onisi, 1940, pI. 17, figs. 9- 12.
Lucina (Myrtea) acutilineata Conrad . Nomura, 1935a, p. 7679 ; Nomura 1935b, p. 109, 110, pI. 5, figs. 1, 2 ; Nomura
and Zimbo, 1935, p. 10 ; Nomura, 1935c, p. 53 ; Nomura,
1935d, p. 210, 211; Nomura and Hatai, 1936, p.123.
Lucina (Lucinoma) acutilineata Conrad. Otuka, 1935, p. 892.
Lucinoma acutilineatum (Conrad). Shikama, 1954, pI. 5, fig . 2 ;Aoki , 1959, p. 268, pI. 1, fig. 14; Iwai, 1961, pI. 1, fig. 10;
Kamada, 1962, p.95 - 97, pI. 9, figs. 10- 16, pI. 10, figs. 1- 3;
Ogasawara, 1976, p. 48, 49, pI. 4, fig . 12; Yoon, 1976a, p.
10,11, pI. 3, figs. 10, 11 , 14; Kim and Yoon, 1978, p. 6, 7, pI.
1, figs. 1, 2; Ogasawara and Yash ima, 1981, pI. 3, figs. 7a,b; Itoigawa et al., 1981 , 1982, p. 68, pI. 12, figs. 13a, b;
Educ. Comm . Fukushima Pref. eds., 1983, pI. 1, figs. 9-13 ;Shibata and Ina, 1983, p. 46, pI. 5, fig. 9 ; Tsuru , 1983, p.
59, 60, pI. 9, figs. 11, 12 ; Matsuura, 1985, pI. 34, fig. 15 ;Takahashi, 1986, pI. 14, fig. 2 ; Ogasawara et al. eds.,
1986, pI. 12, figs. 4, 7, 10, pI. 14, figs. 10, 12a- c, 14; Kobayashi, 1986, pI. 21 , fig. 14; Ogasawara et al., 1989a, pI. 1, fig.
10 ; Ogasawara et al., 1989b, pI. 2, figs. 7a- b.
Lucinoma acutilineata (Conrad). Hirayama, 1954, p. 60- 62,
figs. 2- 7; Itoigawa, 1955, pI. 6, fig . 4 ; Hirayama, 1956, p.
108, pI. 6, fig. 8 ; Itoigawa, 1956, pI. 2, fig. 2; Itoigawa,
1957, p. 4, 5, pI. 1, figs. 9-11 ; Ozaki , 1958, p. 125, pI. 18,
figs. 11, 12, 7 pI. 21 , fig . 3, pI. 23, fig. 4 ; Kanno and Akatsu,
1972, pI. 8, fig . 16 ; Itoigawa in Itoigawa et al. , 1974, p.76,
77, pI. 19, figs. 6- 10c; Amano, 1983, p.45, pI. 5, fig. 5, pI.
9, figs. 11 , 12 ; O'Hara and Nemoto, 1984, pI. 1, fig. 10 ;Matsui, 1985, p. 230, pI. 32, fig . 10; Itoigawa and Shibata,1986, pI. 17, fig. 12; Noda and Amano, 1986, pI. 4, figs. 1a2, pI. 5, figs. 9, 10 ; Marincovich, 1988, p. 10, 11 , pI. 1, figs.
2a, b ; Kanno et al., 1988, pI. 2, figs. 5, 6 ; 8aba, 1990, p.
264, pI. 30, fig. 1 ; Matsui, 1990, fig. 5- 2 ; Noda, 1992, p.
65, pI. 1, figs. 20- 23; Muramatsu, 1992, pI. 49, fig. 5; Lee,
1992, p. 81, fig. 26- 19 ; Noda and Hoyanagi, 1993, fig. 9- 4;
Noda et al., 1995, p. 61, 62, figs. 9- 5,6 and 16- 18- 21 (7 fig.
16,17).
not Lucina (Myrtea) acutilineata Conrad . Nomura and Hatai,
1935, p. 9, 10, pI. 2, figs. 3, 4. [Lucinoma annulata (Reeve)]not Lucina (Lucinoma) acutilineata Conrad. Nomura, 1938, p.
253, pI. 35, fig . 5. [Lucinoma annulata (Reeve)]
Remarks . -Several poorly preserved, compressed specimens were obtained. They have a small suborbicularshell with subtruncated posterior ; the surface is sculptured with fine and lamellar concentric ribs and a few finestriae on each interspace. Features of the lunule andshell interior were not observed.
Locality. - 14a (No. 102572), 14b (No. 102573), 16.

Takashi Matsubara

326

Family Ungulinidae
Genus Felaniella Oall, 1899
Felaniella ferruginata (Makiyama, 1926)

Figures 1-8; 3Diplodonta ferruginata Makiyama, 1926, p. 157, 158, pI. 12, figs.
12, 13 ; Makiyama, 1936, p. 208 ; Araki, 1960, p. 89, pI. 6,
figs. 8, 9 ; Mizuno, 1964, pI. 2, fig. 6 ; Uozumi and Fujie,
1966, p. 150, pI. 6, figs. 8, 9 ; Itoigawa in Itoigawa et al.,
1974, p. 76, pI. 19, figs. 5a- c ; Itoigawa et al., 1981, 1982, p.
70, pI. 12, figs. 8a, b, 11a, b ; Ogasawara and Nagasawa,
1992, p. 1233, 1235, figs. 7- 6a- c, -7a- c, - 8.
Taras ferruginata (Makiyama). Otuka, 1934, p. 616, pI. 47, fig.
35, pI. 38, figs. 39, 40.
Felaniella (Felaniella) ferruginata (Makiyama). Yoon, 1976a, p.
11, pI. 2, figs. 15, 16; Yoon, 1979, p.12, pI. 4, fig. 2 ; Lee,
1992, p. 83, 84, figs. 24- 23- 28.
Felaniella ferruginata (Makiyama). Sasaki and Ogasawara,
1986, pI. 5, fig . 10; Kobayashi and Ueda, 1991, p. 134, 135,
pI. 3, figs. 7, 8.
? Diplodonta ferruginata Makiyama. Nakagawa and Takeyama, 1985, pI. 17, fig . 1 ; Ozawa et al., 1986, pI. 14, fig .
1. [? Cycladicama takeyamai (Otuka)]? Felaniella ferruginata (Makiyama). Nakagawa, 1989, p. 37,
pI. 1, fig. 9.
not Cycladicama ferruginatum (Makiyama). Oyama et al.,
1994, p. 23, 24. [Cycladicama takeyamai (Otuka)]
Remarks .-A small articulated specimen was obtained.
Felaniella ferruginata is characterized by its small size,
slighty longer than high, anteriorly inclined inequilateral
inflated shell with short and narrowly arcuate anterior
margin, straight posterodorsal margin which is parallel tothe posteroventral margin, and a subtruncated posterior.
Although the generic position of this species has been
controversial , the writer considers that it belongs to thegenus Felaniella Oall (1899) because of the morphology of
the anterior adductor muscle scar, whose inner margin is
irregularly undulating (Figure 3), as revised in Yoon
(1976a).

Comparison .-Felaniella usta (Gould), a Miocene to
Recent species, differs in having a more orbicular, moreequilateral shell. Recently, Oyama et al. (1994) considered Cycladicama takeyamai (Otuka, 1938) to be a synonym of the present speCies as a result of their reexamination of topotype specimens. They were unfortunately notillustrated, but it seems that that species is less inflated
and more orbicular. Furthermore, the morphological features of the anterior adductor muscle scar of C. takeyamai
have not been described or illustated. Consequently, thepresent writer regards these two species as not conspecific.
Locality.-15 (No. 102574).
Distribution. - Tsurikake F. in Hokkaido, Isomatsu F. in
Aomori Pref., Kadonosawa F. in Iwate Pref., Nakayama F.
in Fukushima Pref., Oyama F. in Yamagata Pref., Orito F.
in Niigata Pref., Higashi - innai and Sunakozaka Fs. in
Ishikawa Pref., Shimo F. of the Uchiura Gr. in Fukui Pref.,Akeyo and Oidawara Fs. of the Mizunami Group in Gifu
Pref., Kaisekizan F. of the Ichishi Gr. of Mie Pref., Korematsu F. of the Bihoku Gr. in Hiroshima Pref., Japan.
Cheongogsa, Sinhyeon and Manhongdong (Mankod6) Fs.,
Korea.

Family Cardiidae
Genus Clinocardium Keen, 1936
Clinocardium sp. indet.

Figures 1-12, 18
Remarks .-Although Clinocardium in the Yotsuyaku
Formation was listed by Hayakawa et al. (1954) andChinzei (1958a) as Clinocardium shinjiense (Yokoyama,
1923a), this writer does not consider this to be a soundidentification because Clinocardium from this formation
has quadrate radial ribs whose width is nearly equal to orslightly narrower that their interspaces and numbering
more than 23, while C. shinjiense has roof - topped orrounded ones. Specific identification is difficult because
the number of ribs is uncertain.
Locality.-1, 2, 14a, 14b (No. 102576), 19 (No. 102577).
Family Tellinidae
Genus Macoma Leach, 1819
Subgenus Macoma s.s.
Macoma (Macoma) incongrua (v. Martens, 1865)

Figures 1- 9,10,14, 15a, b

Figure 3. Inner surfaces of Felaniella ferruginata (Makiyama) from the Tate Conglomeratic Sandstone Member ofthe Kadonosawa Formation at Nisatai, Ninohe City, Iwate
Prefecture (IGPS coli . cat. no. 102575). Note especially themorphology of the anterior adductor muscle scars. Scalebar = 10 mm.

Tel/ina incongrua v. Martens, 1865, p. 430 (non vidi, fide
Oinomikado, 1934).
Macoma dissimilis (v. Martens). Yokoyama, 1920, p. 116, 117,
pI. 7, figs. 19a- 20.
Macoma inquinata Oeshayes. Yokoyama, 1920, p. 117, pI. 8,
figs. 1,2.
Macoma incongrua (v. Martens). Oinomikado, 1934, text-figs.
8, 9, pI. 8, figs. 16, 17 ; Nomura, 1935c, p. 61, 62 ; Nomura,
1935d, p. 218, 219 ; Nomura and Hatai, 1936, p. 130 ; Habe,
1955, p. 18, pI. 3, fig. 6 ; Yamamoto and Habe, 1959, p. 104,

1002.

Miocene Mollusca of Yotsuyaku Formation, Part 2 (1)105, pI. 9, fig. 3, pI. 14, figs. 25, 26; Chinzei, 1959, textfigs. 3, 4; Kanno and Ogawa, 1964, pI. 1, fig. 12; Matsushima, 1969, pI. 11, fig. 9; Iwasaki, 1970, p. 410, 411, pI. 1,
fig. 14; Oyama, 1973, p. 113, pI. 52, figs. 9, 11-13; Kobayashi, 1987, pI. 3, figs. 7a, b; Okumura and Koyanagi, 1989,
p.77, pI. 8, fig. 11; Baba, 1990, p. 286, pI. 35, fig. 2; Noda,
1992, p. 80, pI. 6, figs. 4a, b.
Macoma (Macoma) incongrua (v. Martens). Hayasaka, 1961, p.
58; Amano, 1980, p.109, pI. 13, fig. 25; Amano, 1983, p.
55, pI. 7, figs. 1a, b; Matsuura, 1985, pI. 33, fig. 16; Takahashi, 1986, pI. 14, fig. 8; Nakagawa et a/., 1989, p.40, pI.
28, fig. 4; Nakada and Amano, 1991, pI. 5, fig. 21; ? Lee,
1992, p. 86, figs. 28-6-9.
Remarks.-Macoma (Macoma) incongrua is characterized by its small size, with the beak situated rather
posteriorly, and with a very weakly rounded posterodorsal
margin.
Comparison.-Macoma (Macoma) tokyoensis Makiyama, 1927, a living species, rather resembles thepresent species, but is distinguished by its larger shellwith a straighter posterodorsal margin and a more elevated and produced umbonal area.
Loca/ity.-3 (No. 102581), 5,6,7,10,12 (No. 102583), 17,
18 (No. 102582), 19 (No. 102596).
Distribution. Recent: China, Korea, Japan, Maritime Provo of Russia,
and Alaska (Habe, 1955).
Quaternary: Otanoshike F. of Hokkaido, Kazusa Gr. in
Chiba and Kanagawa Prefs., "Toshima Sand" of the
Toyohashi Gr. in Aichi Pref., Takahama Shell Bed in
Fukui Pref.
Pliocene: Kume F. in Ibaraki Pref., Seguchi F. in Nagano
Pref., Ashigara Gr. in Kanagawa and Shizuoka Prefs.
Middle-Late Miocene: Togeshita F. in Hokkaido, Kubota
F. in Fukushima Pref.
Late Early-early Middle Miocene: Chikubetsu, Yudoro
and Takinoue Fs. of Hokkaido, Tanosawa F. in Aomori
Pref., Ajiri F. in Miyagi Pref., Japan. Duho and Cheongog sa Fs. in the Pohang district, Korea.

Family Psammobiidae
Genus Hiatula Modeer, 1793

Hiatula minoensis (Yokoyama, 1926)
Figures 1-20,21
So/etellina minoensis Yokoyama, 1926a, p. 221, pI. 28, figs. 1316; Otuka, 1938, pI. 2, figs. 14, 18; Masuda, 1955, pI. 19,
fig.9; Araki, 1960, p.100, pI. 8, fig. 1 ; Kamada, 1962, p.
126,127, pI. 14, fig. 7; Mizuno, 1964, pI. 4, figs. 3, 4 ;Mizuno, 1965, p.332, pI. 1, fig. 3; Uozumi and Fujie, 1966,
pI. 12, fig. 12; Hayashi ana Miura, 1973, pI. 2, figs. 19, 20 ;Kim et a/., 1974, p. 278, pI. 3, fig. 4; Okamoto and Terachi,
1974, pI. 47, fig. 9; Yoon, 1979, p.14, pl. 4, figs. 5, 7, 9;
O'Hara and Nemoto, 1984, pI. 1, fig. 17; Kanno et a/., 1988,
pI. 1, fig. 10.
Sanguino/aria (So/etellina) minoensis (Yokoyama). Otuka,
1934, p. 619, pI. 49, figs. 65a, b; Otuka, 1938, p. 34 ;Oyama and Saka, 1944, p.141, pI. 15, figs. 17, 18 (misspelled as Sanguinorari).

327

Sanguino/aria minoensis (Yokoyama). Makiyama, 1958, pl. 39,
figs. 13-16.
Hiatu/a minoensis (Yokoyama). Itoigawa in Itoigawa et a/.,1974, p.96, pI. 28 figs. 10-11b; Itoigawa and Nishikawa,
1976, pI. 34, fig. 10 ; Taguchi et a/., 1979, pI. 3, fig. 4;
Taguchi, 1981, pI. 2, fig. 12; Itoigawa et a/., 1981,1982, p.
20, pI. 20, figs. 1a, b; Shibata and Ina, 1983, p. 51, pI. 7, fig.
4; Okamoto et a/., 1983, pI. 23, figs. 31, 32; Nakagawa
and Takeyama, 1985, pI. 17, fig. 11; Ozawa et a/., 1986, pI.
14, fig. 4; Nakagawa, 1989, pI. 2, figs. 3a, b; Okamoto eta/., 1989, pI. 6, figs. 17, 18; Iwamura Research Group, 1989,
pI. 21, fig. 4; Shibata and Kato, 1988, pI. 3, fig. 14 ;Okamoto et a/., 1990, pI. 9, fig. 29; Lee, 1992, p.86, figs.
31-4,5, -14: Ogasawara and Nagasawa, 1992, p.1241,
figs. 8-1a, b, -2a, b, -5, -6a, b, 9-27; Amano, 1992, pI. 57,
fig. 14; Noda et a/., 1994, figs. 6-8, -11, -16.
So/etellina cf. minoensis Yokoyama. Kaseno, 1956, p. 6, pl. 3,
figs. 14a-c.
Remarks.-Hiatu/a minoensis is characterized by amoderate-sized shell which is moderately inflated andtransversely elongate-oval in form with a weakly elevatedbeak situated rather anteriorly.
LocaJity.-2 (No. 102586), 4,5 (No. 102585), 7, 8a, 8b, 9,
10 (No. 102587), 11 (No. 102588), 12, 18 (No. 102610).
Distribution.-Kunnui and Tsurikake Fs. of Hokkaido,
Isomatsu and Nagane Fs. in Aomori Pref., Kadonosawa F.
in Iwate Pref., Shimonagasawa F. in Akita Pref., Myozawabashi, Hondoji and Oyama Fs. in Yamagata Pref.,Ajiri and Tsukinoki Fs. in Miyagi Pref., Shiote F. andKunugidaira and Goyasu Fs. of the Yunagaya Gr. andNakayama F. in Fukushima Pref., Tamagawa F. in Ibaraki
Pref., Kozono F. in Saitama Pref., Orito F. in Niigata Pref.,Kurosedani F. in Toyama Pref., Kawaminami, Sunakozaka
and ~igashiinnai Fs. in Ishikawa Pref., Aoki and Omi Fs.,and Oshimojo and Arakida Fs. of the Tomikusa Gr. in
Nagano Pref., Kawakado F. of the Shitara Gr. and Okazaki
F. in Aichi Pref., Toyama and Akeyo Fs. of the Mizunami
Gr. in Gifu Pref., Hiramatsu Sandstone and Siltstone F. of
the Awa Gr. and Kaisekizan F. of the Ichishi Gr. in Mie
Pref., Okuyamada F. of the Tsuzuki Gr. in Kyoto Pref.,Kunimi F., and Shimo F. of the Uchiura Gr. in Fukui Pref.,Yoshino F. of the Katsuta Gr. in Okayama Pref., Bihoku
Gr. in Hiroshima Pref., Hirashima Conglomerate F. of theSusa Gr. in Yamaguchi Pref., Japan. Cheongogsa andHagjeon Fs. in the Pohang district, Sinhyeon F. in the
Ulsan district, Eoil and Songjeon Fs. in the Eoil district,and Pyonryug (Heiroku) F. of the Meongcheon (Meisen) Gr.
in the Meongcheon district, Korea.

Family Solenidae
Genus So/en Linnaeus, 1758
So/en sp. indet.

Figures 1-6, 22
Remarks.- This species is characterized by its compressed elongated cylindrical shell with straight andparallel postumbonal dorsoventral margins and rounded
anterior and posterior corners. The features of obliquely

328

Takashi Matsubara

truncated anterior end and vertically subtruncated posterior one closely resemble Solen krusensterni Schrenk, aliving species, which differs from the present species inhaving an upwardly recurved posterior margin.
Locality.-1, 2, 5, 7, 10, 11 (No. 102580), 12,18 (No.
102581).
Family Cultellidae
Genus Cultellus Schumacher, 1817

Cultellus izumoensis izumoensis Yokoyama, 1923
Figure 1-19
Cultellus izumoensis Yokoyama, 1923a, p.5, pI. 2, figs. 1a, b;
Nomura, 1935d, p. 220, pI. 16; Nomura and Hatai, 1936, p.
132; Otuka, 1941, p. 23, 24, fig. 4; Kanno, 1956, p.213,
214, pI. 5, fig. 8; Iwai, 1961, pI. 1, fig. 19; Iwai, 1965, p.45,
pI. 12, fig. 15; Uozumi and Fujie, 1966, p. 153, pI. 121, fig. 7 ;Hata, 1967, pI. 4, fig. 17; Hayashi and Miura, 1973, pI. 1, fig.
22; Itoigawa in Itoigawa et al., 1974, p. 101, pI. 31, figs. 4,
5; Shibata and Kato, 1975, pI. 16, fig. 23; Ogasawara,
1976, p.57, pI. 14, figs. 16, 18; Yoon, 1979, p.13, pI. 4, fig.
8; Taguchi et al., 1979, pI. 3, fig. 5; Ogasawara andNomura, 1980, p.89, pI. 11, figs. 5a, b, 9; Bito et al., 1980,
pI. 3, fig. 19; Taguchi, 1981, pI. 2, figs. 13, 14; Takayasu,
1981, p. 102, 103, pI. 3, figs. 10, 11 ; Itoigawa, 1981, 1982, p.
104, pI. 20, figs. 3a, b; Shibata and Ina, 1983, p. 52, pI. 7,
fig. 2; Chijiwa and Tomita, 1985, pI. 41, fig.1; Nakagawa
and Takeyama, 1985, pI. 18, fig. 5; Shibata et al., 1987, pI.
1, fig. 15; Shibata and Kato, 1988, p. 28, 29, pI. 3, figs. 10,
11 ; Nakagawa, 1989, pI. 1, fig. 10; Noda et al., 1989, pI. 25,
fig. 10; Ogasawara and Nagasawa, 1992, p. 1241, figs.89a-c, -10, -13a-c, 9-29; Noda, 1992, p. 77, 78.
Phaxas cf. izumoensis (Yokoyama). Masuda, 1955, pI. 19, figs.
14a, b.
Cultellus izumoensis izumoensis Yokoyama. Amano, 1980, p.
110,111, pI. 13, fig. 23.
Cultel/us (Cultel/us) izumoensis Yokoyama. Lee, 1992, p.87,
figs. 31-8, -16.
Cultel/us otukai Ogasawara and Tanai, 1952, p. 211, pI. 19, fig.
19; Kanno, 1956, p.216, pI. 6, figs. 9-12; Aoki, 1959, p.
274, pI. 3, figs. 33, 34; Kanno, 1960, p. 306, 307, pI. 44,
figs. 12a, b, 13.
? Cultel/us izumoensis Yokoyama. Katto and Masuda, 1978,
pI. 3, figs. 8,9. [? Adulomya sp.]
? Cultel/us (Cultel/us) otukai Ogasawara and Tanai. Lee,
1992, p.87, fig. 31-6.
Remarks.-Several specimens lacking shell material
were examined. Specimens from the Yotsuyaku Forma-tion possess rather smaller shells with the posterodorsal
and posteroventral margins parallel, a rounded posterior,and the beak at the anterior three-tenths.
As already pOinted out by Ogasawara and Nagasawa(1992), C. otukai, described by Ogasawara and Tanai(1952) from the Oyama Formation in Yamagata Prefecture,
is considered to be conspecific with C. izumoensis
izumoensis.
LocaJity.-14a (No. 102578), 14b, 19.
Distribution.-Chikubetsu, Takinoue, Yudoro and Tsurikake Fs. of Hokkaido, Sunakose, Tanosawa and Takahoko Fs. in Aomori Prefecture, Kadonosawa and Suenomatsuyama Fs. in Iwate Pref., Ajiri F. in Miyagi Pref., Oyama
F. in Yamagata Pref., Kunugidaira F. in Fukushima Pref.,? Higashiinnai F. in Ishikawa Pref., Uchiyama F. in Gumma
Pref., Ushikubitoge and Nagura Fs. in Saitama Pref.,Akamata Sandstone and Towata Mudstone Fs. of theKurami Gr. and Oga F. in Shizuoka Pref., Aoki and Omi
Fs., Neba, F., and Nukuta F. of the Tomikusa Gr. in
Nagano Pref., Kawakado and Shimoda Fs. of the Shitara
Gr. and Okazaki F. in Aichi Pref., Toyama and Akeyo Fs.
of the Mizunami Gr. in Gifu Pref., Kunimi F., and Shimo F.
of the Uchiura Gr. in Fukui Pref., Toyoda F. of the Masuda
Gr. and Fujina F. in Shimane Pref., ? Uematsu F. of the
Muro Gr. in Wakayama Pref., "lower formation" of the
Bihoku Gr. in Hiroshima Pref., Japan. Sinhyeon F. in the
Ulsan district and Hagjeon F. in the Pohang district, Korea.
Measurements ( in mm).IGPS Coil.
LengthHeightCat. No.
10257856.8
16.6*Beak position from anterior end*Bp

Bp/Length

Valve

17.0

0.299

Left

Family Trapeziidae
Genus Trapezium Megerle v. MOhlfeld, 1811
Subgenus Neotrapezium Habe, 1951

Trapezium (Neotrapezium) ichinohense
sp. nov.
Figures 4-1, 7a, b, 8a-c
Type specimens.-IGPS Coil. Cat. NO.102605 (Holotype), No. 102606 (Paratypes).
Type locality.-Loc. 18; upper reaches of the Nesori
River about 3 km east of Nosokei, Ichinohe town, Ninohe
County, Iwate Prefecture.
Description.-Shell medium to large for the genus

Figure 4. (All figures natural size).
1, 7a-b, Sa-c. Trapezium (Neotrapezium) ichinohense sp. nov., 1, 7a-b: Loc.18, IGPS call. cat. no. 102606, Paratypes, left valves, 8a-c: Lac. 18, IGPS call. cat. no. 102605, Holotype, right valve. 2a-c, 3, Sa-c. Nipponomarcia
nakamurai (Ikebe), 2a-c, 5a~c: Lac. 15, IGPS call. cat. no. 102600, 2a and 5b: right valves, 2a and 5c: left valves, 2cand 5a: apical view. 3: Lac. 3, IGPS coil. cat. no. 102598, left valve. 4,6. Trapezium (Neotrapezium) modiolaeforme
Oyama and Saka, 4: Lac. 18, IGPS call. cat. no. 102607, right valve, 6: Lac. 4, IGPS coil. cat. no. 102608, left valve. 9a~b, 10, 11. Dosinia (Phacosoma) kawagensis Araki, 9a~b, 11: Loc. 10, IGPS coil. cat. no. 102590, 9a~b: right valve, 11 : left
valve, 10: Lac. 9, IGPS coil. cat. no. 102592, inner mould, right valve. 12. Crassostrea gigas (Thunberg), Loc.10, IGPS
call. cat. no. 102566, right valve.

1002.

1

Miocene Mollusca of Yotsuyaku Formation, Part 2 (1)

2a

Sa

2b

2e

5b

329

3

4

5e

6

7a

8a

8b

7b

8e

330

Takashi Matsubara

Trapezium, elongate-trapezoidal in from, inequilateral,
equivalve, thick, moderatey inflated; beak at about anterior one-ninth of shell length; anterior margin narrow,short, smoothly rounded; posterodorsal margin nearlystraight in the young stages (shorter than about 30 mm),becoming gently curved downward with shell growth;posterior end of smaller specimens obliquely truncated,becoming rounded with growth; escutcheon narrow but
distinct; shell surface undulates along concentrical
growth lines that become lamella-like on escutcheon;blunt rounded ridge extends from beak to posteroventral
margin, and ventromedial area of shell is broadly andshallowly depressed. Hinge area of right valve withsingle nodular cardinal tooth and a posterior lateral tooth;left valve has two stong teeth; pallial line and anterior
adductor muscle scar distict and well impressed; posterior adductor muscle scar indistinct and ovate in form.
Remarks.- This species is characterized by its rather
large size, thick shell, surface undulating along growthlines, obliquely truncated posterior end which becomesrounded with shell growth, and gently curved posterodorsal margin.
Comparison. - Trapezium (Neotrapezium) lira tum Reeve,a Recent species, resembles T. (N.) ichinohense, butdiffers in having a smaller shell with a rather strong plate
extending along the escutcheon. The new species differs from T. (N.) isomatsuense, originally described fromthe Isomatsu Formation in Aomori Prefecture by Kotaka(1955), in having a more elongate shell with a nearlystraight posterodorsal margin and a narrower anterior
area. Trapezium (Neotrapezium) isoharense Kamada,
1962, from the Kunugidaira Formation is distinguishedfrom the present species by its smaller size, less rounded
and shorter anterodorsal margin, and more strongly curved
posterodorsal margin. Trapezium (Neotrapezium)
modiolaeforme Oyama and Saka differs in having a thinner shell with a rather smooth suface and a less developed escutcheon. T. (N.) ichinohense is easily distinguished from T. (N.) chonbugense Yoon, 1976, by having
a broader posterior area and curved posterodorsal margin.
Loca/ity.-4, 10, 18 (No. 102605, 102606).
Measurements (in mm).IGPS Coil. Length Height Depth
Cat. No.
10260529.3
9.5(Holotype) 54.4
102606-1
24.7
8.1(Paratype) 45.8
102606-2
22.2
8.5(Paratype) 44.4
102606-3
12.0
3.5(Paratype) 22.6
102606-4
11.2
3.2(Paratype) 20.7
"Beak position from anterior end.

Trapezium (Neotrapezium) modioiaeforme
Oyama and Saka, 1944
Figures 4-4, 6
Trapezium modiolaeformis Oyama and Saka, 1944, p.141, pI.
15, figs. 12a, b, 13a, b; Itoigawa in Itoigawa et al., 1974, p.

80, pI. 20, figs. 8, 9.
Trapezium modiolaeforme Oyama and Saka. Itoigawa andNishikawa, 1976, pI. 33, fig. 10; Itoigawa et al., 1981, 1982,

p. 73, 74, pI. 13, figs. 11a, b; Shibata and Ina, 1983, p.47,
pI. 5, fig. 8; Shibata et al., 1987, pI. 1, fig. 5; Iwamura
Research Group, 1989, pI. 12, fig. 1; Okamoto et al., 1990,
pI. 9, fig. 4; Muramatsu, 1992, pI. 49, fig. 4.

Remarks. - T. (N.) modiolaeforme is characterized by its
rather thin, high and moderately inflated shell, the surfaceof which is smooth in the younger stage and becomes
sculptured with fine concentric growth lines with shell
growth, and by its less well developed escutcheon.
Loca/ity.-4 (No. 102608), 5, 9, 13, 18 (No. 102607).
Distibution.-? Furanui F. of Hokkaido (Uchimura andMajima, 1992), Neba F., and Arakida F. of the Tomikusa
Gr. in Nagano Pref., Kawakado F. of the Shitara Gr. in
Aichi Pref., Akeyo F. of the Mizunami Gr. in Gifu Pref.,"lower sandstone formation" of the Bihoku Gr. in Hiroshima Pref.
Measurements (in mm).IGPS Coil. Length Height Depth"Bp Bp/Length Valve
Cat. No.
Right
102507-1
17.0
0.133
30.0
5.5 4.0102507-2
Left
48.3
24.0+
Right
102507-3
9.1
34.8+ 25.8+"Beak position from anterior end.
Family Venerida~
Genus Dosinia Scolpi, 1777
Subgenus Phacosoma Jukes-Brown, 1912

Dosinia (Phocosoma) kawagensis Araki, 1960
Figures 4-9a, b, 10, 11
Dosinia nomurai Otuka.

Itoigawa, 1956, pI. 2, fig. 3. [not of

Otuka, 1934J"Bp Bp/Length Valve

Dosinia japonica kawagensis Araki, 1960, p.95, pI. 7, fig. 3.
Dosinia (Phacosoma) kawagensis Araki. Masuda, 1963b, pI. 4,

0.114

figs. 1-8; Yoon, 1979, p.15, pis. 7, 9, 10.
Itoigawa in Itoigawa, et al.,
1974, p. 87, 88, pI. 23, figs.1a-6.
Phacosoma kawagensis (Araki). Itoigawa et al., 1981,1982, p.
80,81, pI. 14, figs. 6a, b; Shibata and Ina, 1983, p.48, pI. 5,
fig. 12; Itoigawa and Shibata, 1986, pI. 16, fig. 13; Muramatsu, 1992, pI. 49, fig.6.
? Dosinia kawagensis Araki. Hayashi and Miura, 1973, pI. 1,
fig. 12.
Dosinia (Phacosoma) nomurai Otuka. Lee, 1992, p. 92, figs.
31-3, -9. [not of Otuka, 1934J
Dosinia anguloides Nomuma. Hata, 1967, pI. 4, figs. 2, 3. [notof Nomura, 1935dJ

6.2

Right

Dosinorbis kawagensis (Araki).

5.7

0.124

Left

6.5

0.146

Right

2.4

0.106

Left

2.8

0.135

Right

Remarks.- This species was originally described by

1002.

331

Miocene Mollusca of Yotsuyaku Formation, Part 2 (1)Araki (1960) from the Miocene Kaisekizan Formation of
the Ichishi Group in Mie Prefecture as a subspecies of o.
(P.) japonica Reeve, a living species, and was based on asingle poorly preserved left valve. Subsequently,
Masuda (1963b) redescribed it from well-preserved specimens from the Akeyo Formation of the Mizunami Group,from the Ajiri Formation of Miyagi Prefecture, and from the
Shiote Formation of Fukushima Prefecture and raised it tospecific rank. The species is characterized by its
medium-sized, suborbicular and rather inflated shell witha rounded swollen beak area, upwardly curved anterior
margin, sculpture of regular flat-topped concentric growthlines that become lamellate near the antero- andposterodorsal margins, and obliquely subtruncatedposteroventral margin.
Comparion.- The living Oosinia (Phacosoma) japonica
Reeve is similar to O. (P.) kawagensis, but is distinguishedby having a less inflated shell with a less swollen beakarea.
Oosinia anguloides Nomura, 1935, described from the
Ajiri Formation in Miyagi Prefecture, is distinguished by its
higher, less inflated shell with a more pointed beak.
Loca/ity.-1, 2, 7, 9 (No. 102592), 10 No. 102590), 11,18(No. 102591).
Oistribution.-Ajiri F. in Miyagi Pref., Shiote F. in Fukushima Pref., Kawakado, Shimoda and Kuroze Fs. of the
Shitara Gr., and? Okazaki F. in Aichi Pref., Toyama andAkeyo Fs. of the Mizunami Gr. in Gifu Pref., Chikusa F.,
and Tsuchiyama and Kurokawa Fs. of the Ayugawa Gr. in
Shiga Pref., Okuyamada F. of the Tsuzuki Gr. in Kyoto
Pref., Nenobi Granule Conglomerate and Hiramatsu Sandstone and Siltstone Fs. of the Awa Gr., and Oi and Katada
Fs. of the Ichishi Gr. in Mie Pref., Japan. Sinhyeon Formation in the Ulsan district, Korea.

Measurements (in mm).IGPS Coil.
Length Height Thickness
Cat. No.
102590-1
45.2
42.8
12.4
102590-2
42.8
40.3
11.0
102590-3
45.8
40.0
12.4
102590-4
48.9
45.2
15.5
102590-5
25.1
24.4
6.3
102591-1
41.4
41.4
11.0
102591-2
36.7
9.0
34.6
102591-3
29.3
27.1
7.5
102592
45.5
41.0
13.9
*Beak position from anterior end

Bp!
Length
14.5 0.321
11.2 0.262
14.0 0.306
15.8 0.323
7.0 0.279
11.7 0.283
10.2 0.278
7.5 0.256
13.9 0.305
*Bp

Valve
Right
Left
Left
Right
Right
Right
Left
Left
Left

Oescription.-Shell of medium to large size, transversely elongate, with rounded subtrigonal outline in younger
stages becoming subtrapezoidal with shell growth, inequilateral, equivalve, moderately inflated, moderately
thick; posterodorsal margin long; anterior marginsmoothly rounded, posterior margin gently rounded andsubtruncated or subangular; beak low, small, prosogyrate, situated at about anterior one-third of shell length;
lunule shallow, very small, elongate oblong in form,
defined by fine furrow; escutcheon narrow; shell surface
sculptured with many radial threads and concentric
growth lines; radial threads broader than their interspaces, much stronger than growth lines, and imbricatedin latero-dorsal areas; inner ventral margin smooth;pallial sinus oblique linguiform, and up to three-seventhsof shell length in depth.
Comparison.- This species closely resembles
Ruditapes philippinarum (Adams and Reeve), a living
species, but is distinguished by its more strongly subtruncated posterior and greater number of radial threads.
Ruditapes takagii (Masuda, 1956), originally described fromthe Higashi-innai Formation in Ishikawa Prefecture, differsin having a smaller shell with a more rounded posterior
end and less promient umboal area.
Locality.-1, 2, 3, 4, 5 (No. 102601),6,7, 8a, 8b, 11 (No.
102602), 12,13,15,18 (No. 102603).
Oistribution.-Okuyamada F. of the Tsuzuki Gr. in Kyoto
Prefecture, Akeyo F. of the Mizunami Gr. in Gifu Pref.,Tsuchiyama and Kurokawa Fs. of the Ayugawa Gr. in
Shiga Pref., Nenobi Granule Conglomerate and Hiramatsu
Sandstone and Siltstone Fs. of the Awa Gr. (Shibata,1978).
Measurements (in mm).IGPS Coil.
Length Height
Depth *Bp
Cat. No.
102603-1
54.2
40.3 11.7
18.1
24.5
102603-2
57.5+ 40.4+ 10.4
20.2
102603-3
61.3
46.8 12.6
19.8
102603-4
57.8+ 40.8 11.5
102603-5
61.8+ 45.0+ 12.7+
102603-6
56.1+ 42.2+ 13.5+
102603-7
16.5
52.1+ 39.0 13.0102603-8
22.8
63.0+ ca43.112.2
5.3
7.5102603-9
21.5+ 15.8102603-10
41.6 11.6
19.7
59.4*Beak position from anterior end.

Bp!
Length
0.334
0.330

0.332

Valve
Right
Left
Right
Right
Left
Left
Left
Right
Left
Left

Genus Ruditapes Chiamenti, 1900

Genus Nipponomarcia Ikebe, 1941

Ruditapes miyamurensis (Itoigawa, 1956)

Nipponomarcia nakamurai (Ikebe, 1941)

Figures 5-4,5,7,10

Figures 4-2a-c, 3, 5a-c

Tapes (Amygdala) miyamurensis Itoigawa, 1956, p.189, pI. 1,

Katelysia (Nipponomarcia) nakamurai Ikebe, 1941, p.50-53, pI.

figs. 2, 3.

? Ruditapes miyamurensis (Itoigawa).

Itoigawa in Itoigawa eta/., 1974, p.89, pI. 25, figs. 9, 10a-b.
Ruditapes miyamurensis (Itoigawa). Itoigawa et a/., 1982, p.
83.

2, figs. 1-8.

Nipponomarcia nakamurai (Ikebe).

Itoigawa, 1955a, p. 176184; Itoigawa, 1955b, pI. 6, fig. 6; Itoigawa, 1956, pI. 1, fig.
4; Kamada, 1962, p. 118, pI. 13, figs. 10-12; Mizumo,1964,
p. 605, pI. 3, figs. 2-6; Uozumi and Fujie, 1966, p. 152, pI.
12, figs. 1, 2; Itoigawa in Itoigawa et al., 1974, p. 88, 89, p.

332

Takashi Matsubara

1

2

3

6

Figure 5. (All figures natural size unless otherwise stated).
1,2,3. Mya sp. , 1,2: Lac. 19, IGPS call. cat. no. 102609,1: left valve, 2: right valve, 3 : Lac. 17, IGPS call.
cat. no. 102611, right valve. 4,5,7,10. Ruditapes miyamurensis (Itoigawa), 4: Lac. 11 , IGPS call. cat. no.
102602, left valve, 5, 7,10 : Lac. 18, IGPS call. cat. no. 102603, 5: right valve, 7, 10: right valve. 6 .
Laevidenta/ium? sp., Lac. 19, IGPS call. cat. no. 102637, x 1.5. 8,9,11. Meretrix arugai Otuka, Lac. 10, IGPS
call. cat. no. 102604, 8, 11 : left valves, 9: right valve (showing cardinal teeth). 12,13. eye/ina japoniea
Kamada, Lac. 10, IGPS call. cat. no. 102649, right valves.

1002.

25, figs. 5a-6b; Itoigawa et al., 1981, 1982, p. 86, 87, pI. 16,
figs. 1a, b; Itoigawa and Shibata, 1986, pI. 16, fig. 10 ;Shibata et al., 1987, pI. 1, fig. 8; Kanno et al., 1988, p. 380,
381, pI. 1, fig. 11; Okamoto et al., 1989, pI. 6, figs. 13-15;
Okamoto et al., 1990, pI. 9, fig. 23; Muramatsu, 1992, pI.
49, fig. 7.
? Caryocorbula saikawai Kotaka, 1955, p. 27, 28, pI. 2, figs. 5, 6.
Nipponomarkia nakamurai (Ikebe). Hayashi and Miura, 1973, pI.
1, fig. 8 (misspelling of Nipponomarcia).
?Nipponomarcia "nakamurai" (Ikebe). Taguchi et al., 1979, pI.
2, fig. 16.
not Nipponomarcia nakamurai (Ikebe). Nakagawa and Takeyama, 1985, p. 16, fig. 4; Ozawa et al., 1986, pI. 14, fig. 7.
[Nipponomarcia imobarensis Itoigawa and Nishikawa,
1976J

Remarks.-Nipponomarcia nakamurai from the Yotsuyaku Formation is characterized by a small, well inflated,
subtrigonal shell with a rounded ridge extending from thebeak to the posteroventral margin. In young stages, theshell surface is nearly smooth, with a small lunule definedby a distinct fine line, thereafter fine growth lines become
distinct and irregular and the lunule becomes indistinct
with shell growth. Caryocorbula saikawai, originally described by Kotaka (1955) from the Isomatsu Formation,
Aomori Prefecture, based on a single right valve, isconsidered from its shell morphology to be a synonym of
the present species.
Nipponomarcia nakamurai, figured by Nakagawa and
Takeyama (1985) and Ozawa et a/. (1986) from the Shimo
Formation of the Uchiura Group in Fukui Prefecture, is notthis species, but Nipponomarcia imobarensis Itoigawa andNishikawa, 1976, from the radial threads on the posterodorsal area of the shell.
Locality.-1, 2, 3 (No. 102598),4,5,6 (No. 102597), 7, 8a,10,11,12,13 (No. 102599), 15 (No. 102600), 16.
Distribution.- Tsurikake and Kunnui Fs. of Hokkaido,
Isomatsu F. in Aomori Pref., Kunugidaira F. of the
Yunagaya Gr. in Fukushima Pref., Okazaki F. in Aichi
Pref., Neba F. in Nagano Pref., Toyama and Akeyo Fs. of
the Mizunami Gr. in Gifu Pref., Tsuchiyama and Kurokawa
Fs. of the Ayugawa Gr. in Shiga Pref., Nenobi Granule
Conglomerate F. of the Awa Gr. in Mie Pref., Okuyamada
and Yuantani F. of the Tsuzuki Gr. in Kyoto Pref., "lower
sandstone formation" of the Bihoku Gr. in Hiroshima Pref.
Measurements (in mm).IGPS Call.
Cat. No.
102600-1
102600-2
102600-3
102600-4
102600-5102600-6102600-7102600-8102600-9102600-10102600-11102600-12'Both valves

333

Miocene Mollusca of Yotsuyaku Formation, Part 2 (1)LengthHeight'Depth

Valve

26.8
17.9
26.0
23.2
26.0
20.0
28.1
18.6
27.0
21.8
24.7
21.6

18.4
12.1
21.2
17.0
18.0
15.4
21.1
13.6
20.9
15.9
18.0
14.8

14.4
12.0
16.9
12.5
13.3
11.3
17.8
10.3
15.1
12.3
13.7
11.0

Both
Both
Both
Both
Both
Both
Both
Both
Both
Both
Both
Both

Genus Meretrix Lamarck, 1799
Meretrix arugai Otuka, 1938
Figures 5-8, 9, 11

Meretrix arugai Otuka, 1938, p. 30, 31, figs. 11, 12; Hatai, 1940,
p. 129; Araki, 1960, p. 93, 94, pI. 7, fig. 5; Itoigawa in
Itoigawa et al., 1974, p. 86, pI. 22, figs. 5a-8; Itoigawa andNishikawa, 1976, pI. 34, fig. 31; Taguchi et al., 1979, pI. 3,
fig. 8; Itoigawa et a/., 1981,1982, p.89, pI. 17, figs. 4a, b,
5a, b; Takahashi, 1984, pI. 1, fig. 2; Itoigawa and Shibata,1986, pI. 17, fig. 5; Sasaki and Ogasawara, 1986, pI. 5,
figs. 7a, b; Nakagawa, 1989, pI. 1, fig. 8; Okamoto et al.,
1989, pI. 6, fig. 12; Noda et al., 1989, pI. 25, figs. 5a, b ;Noda et al., 1994, figs. 6, 10, -14a, b, -18.
? Meretrix arugai Otuka. Ogasawara and Noda, 1978, p. 3537, pI. 3, figs. 17, 20, 22a, b. [? Meretrix ninohensis HataiJ
not Meretrix arugai Otuka. Hatai, 1940, p.129. [Meretrix
ninohensis HataiJ
not Meretrix arugai Otuka. Ogasawara et al. eds., 1986, pI. 1,
fig. 20 [Meretrix ninohensis HataiJ
Remarks.-Hatai (1940) described Meretrix meretrix
ninohensis from the latest Early-early Middle Miocene
Kadonosawa Formation of Iwate Prefecture, noting that M.
meretrix ninohensis is distinguished from M. arugai bypossessing a less produced and rounded beak area andless well differentiated anterior and posterior margins.
Subsequently, Ogasawara and Noda (1978) claimed thatthese two species are conspecific as a result of measurements of height and length. Using only these two parameters, it is difficult to establish morphological differences
between the Recent species. Based on comparison
between M. ninohensis (topotype specimens) and M.
arugai from the Kadonosawa Formation by the writer, it isconsidered that the two species are not conspecificbecause M. ninohensis has a distinctly more rounded andblunter beak area than M. arugai, as noted by Hatai (1940).
Specimens from the Yotsuyaku Formation have a rather
narrow beak area and are therefore referable to M. arugai
Otuka.
Locality.-10 (No. 102604).
Distribution.-Kadonosawa F. in Iwate Pref., ? Tsukinoki F. in Miyagi Pref., Kunugidaira F. of the Yunagaya Gr.
and Nakayama F. in Fukushima Pref., Tamagawa F. in
Ibaraki Pref., Sunakozaka F. in Ishikawa Pref., Akeyo F. of
the Mizunami Gr. in Gifu Pref., Kunimi F. in Fukui Pref.,Bihoku Gr. in Hiroshima and Okayama Prefs.
Measurements (in mm).IGPS Call. Cat. No.
102604-1
102604-2
102604-3
102604-4

Length
48.8
47.8+
52.8+
45.1+

Height
38.7
45.1
51.7
34.2+

Depth
13.8
13.3
16.8
17.7

Valve
Left
Left
Right
Right

334

Takashi Matsubara
Genus Cye/ina Deshayes, 1850
Cye/ina japonica Kamada, 1952

Figures 5-12,13
Cyclina chinensis (Chemnitz). Yokoyama, 1926a, p. 222, pl. 28.
Cyclina sinensis (Gmelin). Otuka, 1934, p. 168; Makiyama,
1958, pI. 39, fig. 7.
Cyclina (Cyclina) japonica Kamada, 1952, p. 168, 169, pI. 15, figs.
1a, b, 2; Kamada, 1962, p.115, pI. 13, fig. 4; Kim et at.,1974, p. 277, pI. 38, fig. 9; Itoigawa in Itoigawa et at., 1974,
p.88, pI. 25, figs. 11a, b, 12a-c; Ogasawara and Noda,
1978, p. 32, pI. 3, figs. 6, 13, 18, 21a, b; Itoigawa et at., 1981,
1982, p. 90, 91, pI. 17, figs. 7a, b; Noda et at., 1989, pI. 25,
figs. 6a, b, 12; Lee, 1992, p. 95, figs. 32-7-9; Muramatsu,
1992, pI. 49, fig. 8.
? Cyclina mitsuchii Oyama (MS). Ogasawara and Tanai, 1952,
p.208, pI. 19, figs. 6a, b, 7. [nomen nudum]
Cyclina japonica Kamada. Kaseno, 1956, p. 6, pI. 2, figs. 8ad; Iwai, 1965, p. 41, 42, pI. 12, figs. 3, 4; Shibata and Ina,
1983, p. 50, pI. 6, fig. 1; Itoigawa and Shibata, 1986, pI. 16,
fig.7; Nakagawa, 1989, pI. 1, figs. 4a-c; Kobayashi andUeda, 1991, p. 135, 136, pI. 1, figs. 4, 5; Suzuki et at., 1994,
pI. 49, fig. 8.
Cyclina (s.s.) japonica Kamada. Tanaka, 1961, p. 76, pI. 1, figs.
39,40; Yoon, 1976a, p.15, pI. 1, figs. 15, 16; Yoon, 1979,
p.17, pI. 1, fig. 14.
? Cyclina japonica Kamada. Nakagawa and Takeyama, 1985,
pI. 18, figs. 4a-c; Ozawa et at., 1986, pI. 14, fig. 5. [?
Cyclina tunutata Makiyama, 1926]
Remarks.- This species was originally described fromthe lower Middle Miocene Higashi-innai Formation in
Ishikawa Prefecture, characterized by its slightly higher
than long, rather inequilateral, well inflated andsubtrigonal or suborbicular shell with surface sculpture ofnumerous fine, distinct concentric growth lines and radialstriae, and by its rather produced anterior margin andsubtruncated posterior margin.
Ogasawara and Tanai (1952) discussed and figured
Cyclina mitsuchii Oyama (MS) from the lower Middle
Miocene Oyama Formation in Yamagata Prefecture without designation of a holotype specimen or type locality,
but the species was neither described nor figured by Dr. K.
Oyama subsequently. Consequently, the present writer
regards this species as a nomen nudum. In addition,
judging from the morphological characters of the species
as reported by Ogasawara and Tanai (1952), C. mitsuchii
is a synonym of C. japonica.
Comparison.-Cyclina sinensis (Gmelin), a living
species, closely resembles C. japonica, but is distinguished by possessing a more strongly incurved andelevated umbonal area. Cyclina takayamai, named by
Oyama (1950) for Cyclina sinensis (Gmelin) of Otuka (1938)
from the Bihoku Group in Okayama Prefecture, is distinguished by its more circular, equilateral and smaller sizedshell, as pointed out by Kamada (1952). The present
species rather resembles Cyclina lunulata Makiyama,
which however possesses stronger concentric growthlines and more weakly developed radial striations than C.

japonica and has partly crenulated inner ventral margin.
Cyclina "hwabongiensis" Yoon and Noda, 1978, may be
distinguished from the present species by possessing
stronger radial threads only on the anterior half of theshell. In addition to these, one should consider Cyclina
yatsuoensis Tsuda, 1959, and C. kamadae Araki, 1959,
which have been described from upper Lower-lower
Miocene strata. Specimens of the genus Cyclina areeasily deformed even if the shell material is completely
preserved, and the synonymy between these and C.
japonica must be examined.
Locality.-8b (No. 102593), 10, (No. 102594).
Distribution.- Takinoue and Kunnui Fs. of Hokkaido,
Kadonosawa F. in Iwate Pref., Sugota F. in Akita Pref., Ajiri
and Tsukinoki Fs. in Miyagi Pref., Oyama F. in Yamagata
Pref., Shiote F., Kunugidaira F. of the Yunagaya Gr. andNakayama F. in Fukushima Pref., Asagawa F. in Ibaraki
Pref., Tsugawa and Orito Fs. in Niigata Pret., Kurosedani
F. in Toyama Pret., Sunakozaka and Higashiinnai Fs. in
Ishikawa Pref., Moriya F., and Oshimojo and Arakida Fs. of
the Tomikusa Gr. in Nagano Pret., Kawakado F. of the
Shitara Gr. in Aichi Pret., Toyama and Akeyo Fs. of the
Mizunami Gr. in Gifu Pref., Okuyamada F. of the Tsuzuki
Gr. in Kyoto Pret., Tsuchiyama and Kurokawa Fs. of the
Ayugawa Gr. in Shiga Pret., Oi F. of the Ichishi Gr. in Mie
Pret., Kunimi F., and Shimo F. of the Uchiura Gr. in Fukui
Pret., Japan. Cheongogsa F. in the Pohang district, Sinhyeon F. in the Ulsan district and Songjeon F. in the Eoil
district, Korea.
*Measurements (in mm).IGPS Coil.
LengthHeightCat. No.
102594-1
49.4
49.5
102495-2
40.9
39.9
102495-3
46.0
45.5
102594-4
42.8
48.5• All specimens are slightly deformed.

Depth

Valve

ca. 27.4
22.1
ca. 27.7
ca. 27.3

both
both
both
both

Family Myidae
Genus Mya Linnaeus, 1758
Mya sp. indet.

Figures 5-1-3
Remarks.-Several imperfect specimens have beencollected. The species is characterized by its small size,transversely elongate shell with rounded anterior androundly subtruncated posterior margins, and the shellsurface being sculptured with tine, low concentric growth
threads. Although its hinge area can not be examined,
the species is referable to the genus Mya, on the basis of
the shell features and morphology of the pallial sinus.
Locality.-14a, 14b, 17 (No. 102611), 19 (No. 102609).

1002.

Miocene Mollusca of Yotsuyaku Formation, Part 2 (1)Class Scaphopoda
Order Dentaloida
Family Laevidentaliidae
Genus Laevidentalium Cossmann, 1888
Laevidentalium? sp. indet.

tures; shell small in size, slender, dentaloidal in form andweakly curved dorsally; circular in section; surface
smooth; apex truncated; apical notch not observed.
These features show the specimens to be referable to thegenus Laevidentalium provisionally.
Locality.-19 (No. 102637).

Figure 5-6
Remarks.-Many compressed specimens have beenobtained. They show the following morphologic fea-

335

References cited

Full references are to be presented in the following Part 2
(2).

336

Erratum

The typification of specimen described in the Ohana and Kimura paper (Transactions andProceedings of the Palaeontological Society of Japan, N.S., No. 178, p.140, line 25) is given
incorrectly as the lectotype.

The specimen should have been disignated as the hypotype.

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-

Transactions and Proceedings of ·the Pal.aeontologicalSociety of Japan
December 30, 19~5

New Series No. 180
CONTENTS-

TRANSACTIONS
995. Isao Sarashina : Genetic variation within a dimorphic species, Cryptopecten vesiculosus(Bivalvia, Pectinidae).. .... .. ...... .. .... .. ........ .. .. .. .............. .. .......... 203

996. Satoshi Funakawa: Intrageneric variation and temporal change in the internal skeletal
structure of plagiacanthids (Radiolaria) from Hokkaido, Japan........ .. .. .. .......... 208

997. Sumio Sakagami : Upper Paleozoic bryozoans from the Lake Titicaca region, Bolivia,
Part 1.

Introductory remarks, stratigraphy and systematic paleontology .. .. . . .. .. .. .. .. 226

998. Sumio Sakagami: Upper Paleozoic bryozoans from the Lake Titicaca region, Bolivia,
Part 2.

Systematic paleontology. . .. .. . . . . .. .. .. . . . . .. .. .. .. .. . . .. .. .. .. . . .. .. .. .. . . 261

999. David B. Scott, Shiro Hasegawa, Tsunemasa Saito, Koji Ito and Eric Collins : Marshforaminiferal and vegetation distributions in Nemuro Bay wetland areas, eastern Hokkaido. . ..... .. .. .. .. . ... . .. . . . ...... ..... ....... . .. . .... . . .. . ..... .... . ........ .. 282

1000. Yasuo Kondo and Naoki Kikuchi: "Shelly softground " colonized by an endobyssate
bivalve, Modiolus kurilensis : an example of taphonomic feedback from the Pleistoceneof Kanazawa, Japan.. .... .... .. .. .... ........ ...... ........ .... ...... ...... .... .. 296

1001. Takashi Matsubara: Fossil Mollusca of the Lower Miocene Yotsuyaku Formation in the
Ninohe district, Iwate Prefecture, Northeast Japan, Part 1.
fauna

General consideration of the. .. . . .. .... . . .. .. . .. . ..... .. .. . .. .. . ... ....... ... .... . . .. ....... .. ....... ... 303

1002. Takashi Matsubara: Fossil Mollusca of the Lower Miocene Yotsuyaku Formation in the
Ninohe district , Iwate Prefecture, Northeast Japan, Part 2 (1).
... . . . . ...

- ,Bivalvia and Scaphopoda... . ... , ..... .. . - . , ... . . . . . , .... . . . .. . ... .....

, .

,. .... ..

,.. . .. . . . . . . . .

321