ISSN 0031-0204

Transactions and Proceedingsof thePalaeontological Society of Japan
New SeriesNo. 130

Palaeontological Society of JapanJul y 30, 1983

Co-Editors!taru HAY AMI and Ikuwo OBATA

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Trans. Proc. Palaeont. Soc. Japan, N. S., No. 130, Pp. 61-78, July 15, 1983

760. PALEOENVIRONMENT OF THE PLIO-PLEISTOCENEDAISHAKA FORMATION, TSUGARU BASIN,NORTHEAST JAPAN*
RYOICHI TABUKI
Department of Earth Sciences, College of Education,
University of the Ryukyus, Nishihara, Okinawa 903-{)1

Abstract. This paper presents a brief discussion on the relationship between
the molluscan assemblages and the sediments of the Daishaka Formation, and theinferred sedimentary environment. The stratigraphy and the lithological change
in time and space were studied in detail through the eorrelation using several tuff
and pumice conglomerate layers as key beds. The molluscan assemblages of theDaishaka Formation, which belong to the "Omma-Manganjian fauna", are grouped
into seven categories, judging from the molluscan fossils regarded as actually ornearly autochthonous. These autochthonous assemblages seem to be very consistent
with the sediments representing both the substratum and the water depth at thattime. Almost all the sediments were deposited in the sublittoral zone. Generally
speaking, the finer sediments, prevailing in the lower parts of the lower and upper
units of this formation, were deposited in the lower sublittoral zone, and theremaining coarser sediments in the upper sublittoral zone.

In this paper, the writer intends to give brief
description on the molluscan fauna which occurs
in various kinds of sediments at many horizonsof the Daishaka Formation, and to discuss thesedimentary environment at that time. This work
is completed by going through the following
steps of study.
(1) Exact correlation by using several tuff
layers as key beds.
(2) Analysis of depositional environment
based on the nature of the sediments.
(3) Representation of distribution of molluscan assemblages in terms of species
association.

Introduction
The Plio-Pleistocene Daishaka Formation,
distributed in the northeastern part of the
Tsugaru Basin, Aomori Prefecture, contai!ls
many well-preserved marine fossil invertebrates.
Paleontological studies were published on molluscs (Nomura and Hatai, 1935; Iwai, 1962,1965), brachiopods (Kotoh, 1957) and bryozoa(Kataoka, 1957). Molluscan fossils of the Daishaka Formation are characterized by cold andshallow water species and have been assigned tothe "Omma-Manganjian fauna" by Otuka (1939),
which is known mainly from the Plio-Pleistocene
sediments distributed on the Japan Sea side of
Honshu and Hokkaido.

Acknowledgements* Received April 13, 1982; revised manuscript

The writer expresses his deep appreciation toreceived April 1, 1983.

61

Ryoichi TABUKI

62

Professor Tetsuro Hanai of the University ofTokyo for his valuable suggestions and constantencouragement. The writer is deeply indebted toDrs. Kiyotaka Chinzei and Itaru Hayami of the
University of Tokyo and Toshiyuki Yamaguchi
of Chiba University for their valuable advice andfor their critical reading of the manuscript.
Thanks are also due to Dr. Tomowo Ozawa of
Hyogo University of Education for his constantadvice and encouragement. Gratitude is also
expressed to Professor Takehiko Iwai of Hirosaki
University for providing invaluable informations
on the geology of the area studied.
Outline of geology of the area studied
The Late Cenozoic deposits are extensively
distributed in the marginal area of the Tsugaru
Basin. The surveyed area occupies the northeastern part of this basin and can be divided
into two areas, northern and eastern areas(Text-fig. 1). Stratigraphic successions proposedby previous authors are shown in Table 1 incomparison with the writer's view.
Foldings and faultings trending approximately
N-S direction prevail over the entire area. Elongate dome structure with an axis plunging
south is known in the northern area. The Late
Cenozoic deposits in this area are divided into
the Umanokamiyama, Toyamoriyama, Kareizawa,
Daishaka, Tsurugasaka, Maedanome Formations,
Towada-Hakkoda volcanic ejecta and terrace
deposits in upward sequence.
Table 1. Stratigraphy of the study area: a comparison with previous works.
T. IWAI

I. KATO et 01.
(1959)(1965)

Hongo Fm.
Tsurugasaka Fm.
(Tsurugasaka Fm.)
Ylrlosawa Fm.
Daishaka Fm.
Aizawa Fm.
Otakizawa Fm.
O.P.T.M.

1\

Kareizawa Fm.

Kareizawa Fm.

Toyamoriyama Fm. Toyamori Fm.
Nyunai Fm.

R. TABUKI
this paper
Tsurugasaka Fm.
Daishaka Fm.

I\H.T~

KareizawaFm.
/TC¥lmoriyamaFm.

~manokamiyama Fm.~anokamiyama Fm.
O. P.T. M. : Otakizawa Pumice Tuff Mbr.
H.T.M.: Hitotsumori Tuff Mbr.

The Umanokamiyama Formation: This formation is the lowest strata in this area andconsists of andesitic volcanic breccia, palegreen to grayish white tuff and grayish to blacksiliceous shale. The thickness is more than 300
meters.
The Toyamoriyama Formation: This formation conformably overlies the Umanokamiyama Formation and consists of well-stratified
hard siltstone. The thickness is approximately
380 meters.
The Kareizawa Formation: This formationis composed of grayish massive diatomaceous
siltstone. The uppermost white fine tuff withapproximately 10 meters in maximum thickness
is separable from the main part of this formationand is here designated as the Hitotsumori Tuff
Member. Iwai (1965) regarded it as belonging
to the Otakizawa Pumice Tuff Member, but as
the result of the writer's field survey, the member at Otakizawa (type locality) should be included in the lower unit of the Daishaka Formation. The Kareizawa Formation conformably
overlies the Toyamoriyama Formation on theeast flank of the Mizugasawa Syncline. On thewest flank, however, the Kareizawa Formation
conformably overlies the Umanokamiyama Formation with the lack of the Toyamoriyama
Formation. The Toyamoriyama Formation on
the east flank and the lower part of the Kareizawa Formation on the west flank, both ofwhich are composed of siltstone, are stratigraphically lateral equivalents, because theseoverlie the Umanokamiyama Formation composed of siliceous shale and pyroclastics. The
thickness attains a maximum of 500 meters.
In general, fossils are very rare from the
Kareizawa and the underlying formations, but
Makiyama chitanii is found commonly fromshale and siltstone of the above-mentioned threeformations. Diatoms occur from siltstone of
the Kareizawa Formation and molluscan fossils
are found rarely from siltstone of the Toyamoriyama and Kareizawa Formations.
The Daishaka Formation: This formation ismostly composed of medium to coarse-grainedsandstone, with intercalations of siltstone, fine

760. Paleoenvironment of Daishaka Formation

63

B'

f:-ygj 2
IVVVl 3

LcL.U
~4
~

[~:J 5aI

2Km
I

Text-fig. 1. Index map and geological map.
1: Towada-Hakkoda volcanic ejecta, 2: Maedanome Fonnation, 3: Tsurugasaka Fonnation, 4:
Daishaka Fonnation, 5: Kareizawa Fonnation, 6: Hitotsumori Tuff Member, 7: Toyamoriyama
Fonnation, 8: Umanokamiyama Fonnation, 9: extrusive rock (andesite).
a: fold, b: fault.

64

Ryoichi TABUK!
OTAKIZAWA ANTICLINE--: .' "":::".:'.>..7:-.::-::: ...: ......: .......................... .
U

U'

TORIYAMOR~ FAULTVV7W:"'::~MAGONAI SYNCLINE'f<m _--......."':;;,;.........-:. .'"':/. ,./....,. . ~IV. I __

IV''<)f......:: ..:.<.<.;p; lCemtmuUJ~:I

KAREl ZAWA ANTICLINE~MIZUGASAWA, SYNCLINE~::..::...:.............:~_:::~'::-:_- __ >0>V~

V

-r

V'

~
VI'
• "?N/;~;:/··+·· ..~C>-----'-C~~• • • • 'A;ZAWA ANTICLINE

VI
VU~':'>::"'::::"::::"'::::"::::::'::':::::::.::::.:::.:::::.::::.:.... :.:.::.::::::::.::::::....:.:_VU'

Text-fig. 2. Cross sections.
1: Towada-Hakkoda volcanic ejecta, 2: Maedanome Fonnation, 3: Tsurugasaka Fonnation, 4:
Daishaka Fonnation, 5: Kareizawa Fonnation, 6: Hitotsumori Tuff Member, 7: Toyamoriyama
Fonnation, 8: Umanokamiyama Fonnation, 9: extrusive rock (adesite).
The positions of cross sections are indicated in Fig. 1.
to medium-grained sandstone and conglomerate
layers. Its lower unit consists mainly of sandstone, in which fossils are rare. Its upper unit
shows remarkable lateral and vertical changes
in lithology. Marine inverte brates are especiallyabundant. In the southern part of the easternarea, this formation conformably overlies the
Hitotsumori Tuff Member. However, this formation unconformably overlies the underlying
formations in the northern part of the easternarea. The thickness attains a maximum of 730
meters.
The Tsurugasaka Formation: This formationis composed of grayish white pumice tuff containing subangular andesitic rock fragments.
It overlies conformably the Daishaka Formationin the area around the Namioka River and southof the river, whereas an unconformity is ob-

servable in the area north of the river. The
thickness attains a maximum of 150 meters in
the area just between the eastern and northernareas.
These formations are covered with, in upward
sequence, the Maedanome Formation (mud, sandand gravel, occasionally intercalating peat andpeaty mud, 60 meters thick) and the TowadaHakkoda volcanic ejecta (grayish white pumic
tuff containing subangular andesitic rock fragments).
Extrusive andesite is found in the upperstream of the Magonai River and the upperstream of the Takizawa River, though smallin scale. The extrusion is inferred to have takenplace after the deposition of the Umanokamiyama Formation and before the deposition of
the Daishaka Formation.

760. Paleoenvironment of Daishaka Formation

Stratigraphy and lithologyof the Daishaka Formation
The exposures of the Daishaka Formation
are separated into the eastern and northern areasby the Tsurugasaka Formation which lies between the two areas. The Daishaka Formation is
stratigraphically divided into two units. The
lower unit mainly consists of sandstone, and theupper unit mainly consists of sandstone, conglomerate and siltstone. The boundary between
the lower and upper is somewhat arbitrary but
can be drawn along the lower limit of the key
bed DT-3, which can be traced widely both in
the eastern and northern areas. In addition, theupper part of the lower unit and the entire
upper unit of the Daishaka Formation areinterbedded with tuff layers and pumice conglomerate, which consists of pumices of pebble
and cobble size, cemented by the matrix ofsand or sandy silt. Some of them (DT-1 to DT-7
(D=Daishaka, T=Tuff) are of practical use forcorrelation.
In the eastern area, the formation attains amaximum thickness of 730 meters along theroute of the Shoheizu River, but becomesthinner toward the north to 110 meters thickin the neighborhood of the Tsurugasaka Spa,the northern end of the eastern area. In thenorthern area, the thickness of this formation
attains more than 720 meters.
Descriptions of the stratigraphy and lithologyof this formation are given as follows.
The lower unit: In the eastern area, the lower
unit of the Daishaka Formation conformably
overlies the Hitotsumori Tuff Member of the
Kareizawa Foramtion. The exposure showing
the conformable relation between the twoformations are found in the upper stream of
the Shoehizu River and the upper stream of
the Namioka River. Toward the north fromthese areas, successively the upper horizon of
the Daishaka Formation abuts against the massof the underlying formations, the Umanokamiyama Formation and the Kareizawa Formation,with low-angle clino-unconformity in both flanksof the Aizawa Anticline north of the Namioka

65

River. Therefore, the northern extention of the
distribution of the lower unit is con fiend to thesouthern area, south of the route of a tributaryof the Magonai River. Thickness of the lower
unit attains 440 meters at the route of the
Shoheizu River, and decreases to the north tobecome 30 meters along the upper stream of
the Takizawa River. However, along the upperstream of the Otanizawa River and the upperstream of the Gogasawa River, north of the
Takizawa River, the thickness of the lower
unit again increases to attain more than 90
meters and, to the north, abruptly decreases
to thin out.
The lower unit is subdivided into two, thelower and upper parts. The lower part of thelower unit is restricted in distribution to the areaaround the Namioka River and south of the river.
The lower part is mainly composed of dark grayto gray fine to medium-grained sandstone containing abundant carbonaceous matter. Manysilt-walled burrows exist densely in the fine tomedium-grained sandstone exposed along the
middle stream of the Namioka River. In the
middle stream of the Namioka River, the granule
to pebble-bearing coarse-grained sandstone of
30 meters thick is found in the basal part of theDaishaka Formation just above the unconformity. The sandstone contains sporadicallycobbles and boulders of grayish white tuff ofabout 10 to 200 centimeters in diameter which
are probably originated from the underlying
Umanokamiyama Formation.
The upper part of the lower unit of theDaishaka Formation is distributed extensively
in both flanks of the Aizawa Anticline along
the Gogasawa River and south of the river. The
upper part lies over the lower part conformably
in the area south of the Namioka River but
unconformably in the middle stream of theriver, and finally, to the north, it lies directly
over the underlying formations without intercalation of the lower part of the lower unit.
The upper part is mainly composed of pumicebearing conglomeratic medium to coarse-grainedsandstone and frequently exhibits cross lamination and cross stratification of large scale. It isenen,...------ NORTHERN AREA

2EASTERN AREA
Tsu

17

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o
::r-

1')'

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Uma

"

'.'

IJ:j

~
.....

--1

.-.-... !i!.;- i:, o
•
.:t
O
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· ."""'i<~' fillj'"~-'- B-'
~Vv
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be
de
f
9
.v.v
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II
rEill""""ffi]v[8]'';
0]:.... ~++
·v·y·
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.~,·.:"L,""A'..!

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760. Paleoenvironment of Daishaka Formation

67

R.(6 )~TANOSAWA R. (4 )N-l1

SHOHEIZU R.(I4-IS)

o__________~I

L -________

2km

~I

SUGI NOSAWA R.

(16)

Text-fig. 4. Map showing fossil localities.
The route numbers in parentheses correspond to those shown in Fig. 3.

Text-fig. 3. Columnar sections of the Daishaka Formation with the stratigraphic positionsof fossil localities.
1-17 indicate the routes along which columnar sections are obtained, and which are shown in the
map where the dotted area indicates the distribution of the Daishaka Formation.
1: a tributary of Sawauchizawa River, 2: Sawauchizawa River, 3: Shinjo River, 4: Tanosawa River,
5: Kujirasawa River, 6: Otakizawa River, 7: the neighborhood of Tsurugasaka Spa, 8: a tributaryof Magonai River, 9: Gogasawa River, 10: Otanizawa River, 11: Takizawa River, 12: Magonai
River. 13: Namioka River, 14: lower stream of Shoheizu River, 15: upper stream of Shoheizu
River, 16: Suginosawa River, 17: Yunosawa River. Uma: Umanokamiyama Formation, Ka: Kareizawa Formation, Hi: Hitotsumori Tuff Member, Da: Daishaka Formation, Tsu: Tsurugasaka
Formation. a: conglomerate, b: medium to coarse-grained standstone, c: fine to medium-grainedsandstone, d: massive siltstone, e: stratified siltstone, f: fine tuff, g: pumice tuff, h: "pumiceconglomerate", i: thin tuff key bed, j: alternation of siliceous shale and fine tuff, k: alternationof sandstone and fine tuff, I: alternation of pumice tuff and fine tuff, m: extrusive rock, n: slumping deposits, 0: cross lamination.

68

Ryoichi TABUKI

interbedded with many layers of tuff and pumiceconglomerate. Among them, two sets of pyro·
clastics are useful for key beds, DT·1 and DT·2.
DT·1 is restricted in distribution to the easternarea and DT·2 is traceable over the whole areastudied. DT·1 is situated at the lower horizonof the upper part and has variable thickness
ranging from 4 to 17 meters. It consists of white
to light gray fine tuff with intercalations ofconglomeratic medium to coarse.grained sand·stone and sandy pumiceous tuff. DT·2 strati·
graphically occupies the middle portion of theupper part and attains a maximum thicknessof 73 meters at the route of the Shoheizu River.
It is mainly composed of white to gray pumi·
ceous tuff, accompanying pumiceous sandstone
and white to gray fine tuff of several metersin thickness. The lowest portion of the upper
part in the area south of the Magonai River ischaracterized by the slumping deposits con·taining "tom off" beds of sandstone and silt·stone with abundant carbonaceous matter.
These clastic rocks with abundant carbona·
ceous matter are characteristic of the lower
part of the lower unit, and these "tom off'
beds are probably derived from the lower part.
Pebbles and cobbles of fine tuff and andes·
ite are also abundant in this portion. The slump.
ing deposits conformably overlie the fine·grainedsandstone of the lower part in the middle streamof the Shoheizu River. The deposits rest upon
the eroded surface of the lower part in the mid·dIe stream of the Namioka River. In the upperstream of the Magonai River, north of the
Namioka River, the slumping deposits are also
observed at almost the same horizon as in theabove two routes, lying over the basal con·glomerate which unconformably overlies the
extrusive andesite without intercalation of thelower part. However, they are mainly composedof the angular cobbles and boulders of fine tuff,
accompanying the pebbles and cobbles of andes·
ite with sandy matrix, and lack in the clastics
containing carbonaceous matter. In the area
north of the Magonai River, the slumping de·posits are absent.
In the northern area, the lower unit of theDaishaka Formation is distributed in the central
part of the Otakizawa Anticline which actuallyshows dome structure. The lowest part of theformation is hidden under the anticlinal dome.
The inferred thickness is more than 220 metersat the route of the Shinjo River and more than
440 meters at the route of the Sawauchizawa
River. The lower unit is mainly composed of
medium to coarse·grained sandstone, bearing
granules and pebbles of fine tuff, andesite andpumice, and exhibits cross lamination.
The lower unit is poor in the occurrenceof molluscan fossils except for the uppermost
part. Most of molluscan fossils are discovered
as molds and casts. The molluscan fossils occur
sporadically in fine to medium·grained sandstone
and bivalves are often articulated, whereas
molluscan fossils found densely in the con·glomeratic rp.edium to coarse·grained sandstone
are fragmental, suggesting allochthonous modeof occurrence.
The upper unit: In the eastern area, the upper
unit is distributed in the west flank of the
Aizawa Anticline, forming a monocline dippingto the west. The upper unit conformably overlies
the lower unit in the Gogasawa River and in
the area south of the river. In the area north of
the river, the upper unit lies directly over theunderlying Kareizawa Formation without inter·calation of the lower unit. The thickness attains
a maximum of 330 meters along the route of
the Namioka River, and a minimum of 110
meters in the neighborhood of the Tsurugasaka
Spa. The upper unit is mainly composed ofconglomeratic medium to coarse·grained sand·stone. Tuff and pumice conglomerate are fre·quently found in the lower part of the upper
unit, of which five sets of tuff and pumice con·glomerate, DT·3 to DT·7, are characteristic torecognize and are traceable over the whole area
stUdied. The lower limit of DT·3 is defined tobe the boundary between the lower unit andthe upper as mentioned above. DT·3 is composedof the lower pumice conglomerate of 1 to morethan 2 meters thick and the upper pale brownfine tuff with considerably variable thicknessof 0.02 to 3 meters. Both parts are separated by760. Paleoenvironment of Daishaka Formation

pumiceous medium to coarse-grained sandstoneof 1.5 to 4 meters thick, except at the route of
the Namioka River where the intervening sandstone is absent. The total thickness of DT-3
ranges from 2.5 to 8 meters. DT-4 is the set
composed of the white fine pumice layer of 0 to
15 centimeters thick and the overlying volcanic
breccia of 30 to 80 centimeters thick, composedof andesite, scoria and pumice. The total thickness decreases to the north from 95 centimetersat the route of the Shoheizu River to 30 centimeters at the route of the Otakizawa River
where the pumice layer is absent. DT-5 consistsof the pumice conglomerate composed of pumiceand scoria of granule to cobble size with thematrix of medium to coarse-grained sand, frequently intercalating the laminae of pumiceous
medium to coarse-grained sand. At some routes,
light brown fine tuff lies over, or below thispumice conglomerate. The overlying fine tuff
ranges from 15 to 450 centimeters thick andthe underlying tuff from 30 to more than 600
centimeters thick. The thickness of the conglomerate attains a maximum of 8 meters at
the route of .the Shoheizu River and a minimumof 3 meters at the route of the Shinjo River.
DT-6 is assigned to the light brown fine tuff
which consists of the alternation of coarsergrained and finer-grained layers of 3 to 20
centimeters thick, and intercalates the laminaeof pumice. At the two routes of the Shoheizu
River and the Magonai River, pumice conglomerate of 70 to 200 centimeters thick is interbedded in the fine tuff. The total thickness
attains a maximum of 24 meters at the routeof the Magonai River and decreases to the northand to the south and attains a minimum of 3
meters at the route of the Otakizawa River.
DT-7 consists of the pumice conglomeratecomposed of pumice of 1 to 10 centimeters indiameter, containing the granules and pebblesof andesite and siltstone, with the matrix of
medium to coarse-grained sand, and intercalates
several beds of pumiceous medium to coarsegrained sandstone.
The total thickness attains a maximum of 20
meters at the route of the Magonai River. In

69

the lower part of the upper unit, dark gray togray fine to medium-grained sandstone andsiltstone predominate in several horizons, but
generally change laterally into medium to coarsegrained sandstone. In the area south of the
Takizawa River, the conglomerate is foundaround the boundary between the lower andupper units, and it becomes thick toward thesouth. The conglomerate contains many subangular granules and pebbles of andesite of 0.2
to 3.0 centimeters in diameter, accompanying
granules and pebbles of pumice, scoria andtuffaceous siltstone, cemented by relatively
small amount of sand. To the north of theMagonai River, the conglomerate changes laterally into medium to coarse-grained sandstone.
The upper part of the upper unit is mainly composed of pumice-bearing conglomeratic medium
to coarse-grained sandstone with cross lamination. In the upper part of some localities,
molluscan shells occur abundantly, and bivalves
are commonly disarticulated. The uppermost
part of the upper unit is occasionally interbeddedwith several beds of peat and peaty mud.
In the northern area, the upper unit is distributed so as to surround the lower unit. The
sequence attains 280 meters along the route of
the Sawauchizawa River and 230 meters along
the route of the Shinjo River. The lithology ofthe lower part of the upper unit is different
between in the west flank of the Otakizawa
Anticline and in the east flank. In the west
flank, conglomeratic medium to coarse-grainedsandstone with cross lamination predominates.
Thick coquina beds containing molluscan shells,
mostly fragmental, are present in the middle
portion of the lower part. In the east flank, on
the contrary, fine to medium-grained sandstone
predominates in several horizons, as is seen in
the eastern area. Similar lithology to the lower
part of the west flank is found in the upper partof the upper unit throughout the northern area.
At some places, however, the upper part is interbedded with thin beds of pumice and silt, andcontains abundant molluscan and brachipod
shells of allochthonous occurrence. Peat beds
are occasionally found in the uppermost part

Ryoichi TABUKI

70

of the upper unit.
In the upper unit, abundant marine inverte·
brate fossils are found in various kinds of sedi·ments. The relationship between the sediments
and the modes of occurrence of molluscan shells
is generally similar to that recognized in thelower unit.
Analysis of molluscan fossils fromthe Daishaka Formation
The following six types of sediments whichcontain molluscan fossils are recognizable in the
Daishaka Formation:(A) Sandy silt(B) Silty fine-grained sand(C) Granule to pebble-bearing ill-sorted fine tomedium-grained sand(D) Granule to pebble-bearing calcareous sandy
silt or silty sand(E) Conglomeratic medium to coarse-grained
sand(F) Gravel
In the sediments (A) and (B), molluscan shells
occur at some places. The majorithy of bivalves
are disarticulated. They occur sporadically,
densely in lenticular beds or lying parallel tothe bedding plane along the laminae of relatively
coarse-grained sand. A few articulated bivalves
are also found. In the sediments (C), molluscan
shells occur relatively densely and form shell
beds at some places. The sediments (D) is characterized by the grayish white colour, reflecting
their sediment grain dominated by shell fragments. Molluscan shells occur densely to formshell beds. Most of bivalves are disarticulated,
lying parallel to the bedding plane. In the sediments (A) to (D), shells are found in various
modes of occurrence, but as a whole, shells do
not suffer from destruction or abrasion. In thesediments (E), however, shells show an allochthonous occurrence and form shell beds atsome places. Shells are generally ill-preserved,
fragmental and remarkably abraded, suggesting
the effect of transportation over much distance.
In some cases, however, well-preserved shells
are found abundantly, and some of them arefound even in living position. In Loc. OT-4, theindividuals of Panomya arctica occur at uprightposition and apart from one another with a relatively constant distance. Shells in gravel (F) arevery rare. In general, shells are ill-preserved andat some places most of them are fragmental
and abraded.
Theoretically, reconstruction of paleoenvironment should be based only on the ecological
data of the molluscs which are proved to be
autochthonous in occurrence. The term, assemblage here used, do not necessarily mean to haverelationship among the constituent species. Two
species occurring together may be a result oftransportation, accidental in terms of the ecology. However, the shells with scarce destruction
and abrasion may suggest that they were nottransported for long distance, thus are taken
into account as one of the informative data at
the time of discussion to reconstruct paleoenvironment. Under such a precondition, sevenassemblages of fossil molluscs, whose constituents are mostly autochthonous (or if not strictly
autochthonous, their habitats are expected near
the present localities), are recognized. Eachassemblage is named after the dominant species
in the number of individuals. The mode of life
and the feeding type of the constituent speciesof these assemblages are to considerable extent
related to the nature of the sediments in whichthese fossils are embedded. The importance ofbottom character as controlling factor on the
distribution of molluscs is recognized in many
recent faunal studies of molluscs. Thus it isnatural that these assemblages of species havea certain relation with the lithology. Most of
the constituents of the above-mentioned assemblages in sandy silt and silty fine-grained sandare composed of infaunal species and are deposit
or suspension feeders. However, the constituentsof other assemblages in coarser sediments arecommonly composed of both of infauna andepifauna, and are mostly suspension feeders.
In general, it may be said that as the sediments
containing molluscs get coarser, infauniu. species
become fewer both in the numbers of species
and individuals.

760. Paleoenvrionment of Daishaka Formation

Various neontological infonnations on theecology of living molluscs are used to estimate
the paleoenvironments. These infonnations aremainly derived from Yamamoto and Habe (1958,
1959, 1962), Habe and Ito (1965), Oyama(1973) and Habe (1975a, 1975b, 1977).
The seven assemblages are briefly describedas follows:
A. Acila nakazimai-Macoma calcarea assemblage
This assemblage is found in sandy silt (A) andsilty fine-grained sand (B) of the lower part of
the upper unit in the eastern area (Loc. M-1 andT A-2). Articulated individuals of Adla nakazimai
overwhelm those of other species. The assemblage is characterized by the inhabitants of muddy and sandy bottom of the lower sublittoralzone, probably ranging from approximately
50 meters to more than 100 meters in depth.
B. Portlandia japonica-Yoldia notabilis-Macoma
calcarea assemblage
This assemblage is confined to silty finegrained sand (B) of the lower part of the upper
unit in the northern area (Loc. S-1, S-2, S-3, S-4,
S-5, S-6, S-7, 0-1, 0-2 and 0-7). In most cases,
Portlandia japonica or Yoldia notabilis dominates. But, one of these two species dominateswith the rare occurrence or the absence of theanother in the same locality, probably reflecting
delicate difference of ecological requirementsof these species. Cryptonatica janthostomoides,
Nuculana ikebei and Robaia robai are commonly
found in this assemblage. The assemblage ischaracterized by the inhabitants of muddy andsandy bottom of the lower sublittoral zone.
C. Nuculana pemula sadoensis-Portlandia japoinica-Limopsis tokaiensis assemblage
This assemblage is found in silty fine-grained
sand (B) of the lower part of the upper unit in
the northern and eastern areas (Loc. S-8, N-3,
N-4 and N-5). This assemblage is similar to theabove-mentioned B assemblage, but is different
in the occurrence of Nuculana pemula sadoensis
and the absence of Yoldia notabilis, Nuculana
ikebei and Robaia robai. The constituent speciesof this assemblage are mostly the inhabitantsof muddy and sandy bottom of the lower sublittoral zone.

71

D. Astarte borealis-Venericardia ferrug;nea-Nu-

cUlana pemula sadoensis-Polynemamussium
alaskense assemblage
This assemblage is found in granule to pebblebearing ill-sorted fine to medium-grained sand(C) of the uppennost part of the lower unit in
the eastern area, and of the lower part of theupper unit in the northern and eastern areas(Loc. K-1, 0-3, 0-4, 0-5, OT-9, TA-1, N-6, N-7,
N-8, N-9, SH-2 and SH-3). A species questionably
assigned to the Veneridae and Limopsis tokaiensis are other common constituents. Particularly,
at all localities in the northern area (Loc. K-1,
0-3, 0-4 and 0-5), Veneridae? species are foundabundantly. The occurrence of Polynemamussium alaskense is limited only to this assemblage,
and Turritella fortilira ta is also characteristic
species of this assemblage, though the individualsof the species are relatively few. The assemblage
includes muddy and sandy bottom dwellers of
the lower sublittoral zone.
E. Acesta goliath-Ezocallista brevisiphonataAstarte borealis assemblage
This assemblage is confined to granule topebble-bearing sandy silt or silty sand (D) of
the uppennost part of the lower unit and thelower part of the upper unit in the eastern area
(Loc. OT-2, OT-5, OT-8, N-10, SH-4, SH-5, SH-6
and SG-1). Besides the above-mentioned three
species, Nuculana pemula sadoensis, Chlamys
cosibensis and Monia macroschisma are commonly found. The assemblage contains epifaunal
species abundantly. Here, the epifauna is mainlycomposed of sessile molluscs, lacking in such
scallops as Mizuhopecten. The living fonns of
the constituent species of this assemblage aremostly mown from the upper sublittoral zone,
ranging approximately from 0 to 50 meters in
depth, although Acesta goliath is living below
100 meters deep.
F. Ezocallista brevisiphonata-Glycymeris yessoensis-Chlamys cosibensis assemblage
This assemblage is found in conglomeratic
medium to coarse-grained sand (E) of the upper
unit in the eastern area (Loc. OT-3, OT-7, SH-8
and SH-9). Mizuhopecten yessoensis yokoyamae
is commonly found in conglomeratic sand.

72

Ryoichi TABUKI

Table 2. List of representative molluscan fossils from the Daishaka Formation.

o rare to common,@

abundant~
Assemblage

Species

Silty fine sand

AcilaMacoma

Locality

Acila nakazimai OTUKA

A.

sand:1
silt

:l:

N.

, , , , ,~Robaia rabai (KURODA)
Yoldia notabilia YOKOYAloIA
Portlandia japonlca (A.ADAMS '" REEVE)

~

~

0

0

@@

M

'"

~

@

0
0

0 0

.

, b , z, z, z,~~" '" '" '" '" '" '" '" bvigilia SCHENCK

yokoyamai (KURODA)
ikebel (SUZUKI , KANEHARA)

NuculanaPortlandia-

Portlandia-Yoldia-Macoma

7 ~
, N,

Ennucula tenuis (MONTAGU)
Nuculana pernula sadoensis (YOKOYAMA)
N.

I

0 0

0
0 o@ @
0

0 0
00 0
0 0
0 o@
0
@ 0 @
@@ 0
@o 0 0 @@ 0 0 @ 0 @ @o0 0Area boucardi JOUSSEAUME

Glycymeds yessoensis(SOWERBY)

00

Limopsis tokaiensis YOKOYAMA0 0 0

My til us crassitestus LISChKE

Modiolus margari taceus (NOMURA&- HATAI)

Solamen spectabilis {A. ADAMS)
Polynemamussium alaskense (DALL)

0

0
0 0

@

0

0

Chlamys cosibensis (YOKOYAMA)C.
C.

daishakaensis (MASUDA
swiftii (BERNARDI)'" SAWADA)

Hizuhopecten yessoensis yokoyamae (MASUDA)
Monia macroschisma (DESHAYES)
Accsta goliath (SOWERBY)
Limar ia hakodatensis (TOKUNAGA)
Limatula vladivostokensis SCARLATa
Lucinoma annulata (REEVE)
Thyasira tokunagai KURODA .. HABE0

0 0 0 0000Venericardia ferruginea (CLESSIN)0

Miodontiscus nakamurai (YOKOYAi"..A)
Astarte borealis (SCHUMACHER)

0alaskensis DALLClinocardium chikagawaense KOTAKA

A.

0 0

Serripes groenlandica IBRUGUIERE)
Spisula voyi alaskana DALL
Cadell a lubrica (GOULD)
Macoma calcarea (GHELIN)000 0

0 @0 @0 0 0

0Macoma contabulata (DESHAYES)
Mercenaria stimpsoni (GOULD)
Callithaca adamsi (REEVE)
Ezoca 11 ista brevis iphona ta (CARPENTER)
Mya japonica JAY
Caryocorbula venusta (GOULD)

0

Panomya beringiana DALLP.

arctica (LAMARCK)

Pholadidea peni ta CONRAD
Puncturella nobilis (A.ADAMS)
Homalopoma amu8sitatum (GOULD)
Cocculina japonica DALL

0'l'urritella fortilirata SOWERBY
Eittiwn yokoyamai OTUKA
Neverita reiniana (DUNKER)
Cryptonatica janthostomoides (KURODA .. HABE)
Neptunea arthritica hirosakiensis IWAI
Mohnia YO!lnamii (YOKOYAMA)

0 0 000 0
0

@ 0

0

00

Fusitriton oregonensis (REDFIELD)
Crepidula turugasakana NOMURA" HATAI
Cancellaria kobayashii (YOKOYAMA)
Antiplanes contraria (YOJ(OYAMA)
Turbonilla shigeyasui YOKOYAMA
Cadulus opportunus (KURODA " HABE)
Dentalium rhabdotum (PILSBRY)

@

0
0

@ 0

0

0
0

0

73

760. Paleoenvironment of Daishaka Formation

Gra.-bearing fine to medium Band

Gra.-bearing sandy sitt

Medium toor s1 1ty sand
Acesta-Ezocallista-coarse sandAstarte-Venericardia-NuculanaPolynemamussium
~

"1 ~

"

~

I

~

I

b b !> ~

~

I
Z

... m
I
Z

I
Z

~

:l.

Astarte"other assemblages·

Chlamys-type 1. . ~ ~ ~ .,:, . .:l: ~ ~ S ~ ffi . . m .. Z

N

~

I

I

0

~

~

I

I

...

~

m

00
0
OOO@OOO@@@
0
0

~

"'~N

~

z

00

0

EzocallistaGlycymeria-

Gravel

:'=

I

N

~

0

0

OO@O@
0

~

@O

0
@

0

type 2"1 ...

Z " ~ ~ ~ z . ffi :l. z ~
N

~

I

I

@O
000

0

@
0
O@OO@
@@
00

0
00
0
0

~

0

N

I

0

0

0

O@

@
0

0
00

1000
00 00

0

10
0
@@@
0
0
000
00
0
0

00

@

@0
@O

0
O@@OOOO@@@O@@O@O @OOO @OOO@O
00
0000
O@O
0
000
00
0
000
0
00
@
0
10000
@O
0
0
0
0
0
OO@
0
0
0000
@@@@
@@
0
0
0
0
0
0
OO@OO
00
0000
00
0
@@
O@O@O
0
O@@O@@O@OOO
00
000 00
@
@O
@ 0
0
0
0
0
0
0
00000
0
0
@OOO@ @@@@OOO
OOOO@@
00
@ 00
00
@ 0
0
0
0
0
@
0
0
0
0
00
00
0
0
00
0
0
00
00
@
@oog@o@o @~@@
0
0
@

0
00

0

0

0000
0
0
00

0
0

@

000

0

000

0

0

0

0

@

0
0

0

000
0

0
0

00

0
0
OO@O
00

0

000
0

0

10
0000

0

0

00

0
0

0

00
0

00
0

0

0

0

0

@O

0

0

0

0

0
0

0

0
0

RyoichiTABUKI

74

EASTERN AREA

5

N
7

9

8

Tsu

+ . ..
+
Da

"

. ~'.

.

10

14-15

11

16

17

.. . ...
',,.

~~,.~.D.,r::::P,.t:=I.~, • "

. ,'

..

•

"

DT-7

Ka

"
m

200

100

o

2Km

~D~0~
abc

d

e

o

t>

o

II!!

A

B

C

D

•E •F

''\.,

A

G

Uma

"

'

".'- .'. ....

+ . . '--'
Ka

-'---

Text-fig. 5. Schematic stratigraphic section, including the distribution of the molluscan
assemblages. (Fig. 5-1: eastern area, Fig. 5-2: northern area)
The route numbers and the abbreviations of formations correspond to those shown in Fig. 3.
a: conglomerate, b: medium to coarse-grained sandstone, c: fine to medium-grained sandstone,
d: siltstone, e: pyroclastic rock. A: Acila nakazimai-Macoma calcarea assemblage, B: Portlandia
japonica-Yo ld ia notabilis-Macoma calcarea ass., C: Nuculana pernula sadoensis-Portlandia japonicaLimopsis tokaiensis ass., D: Astarte borealis-Venericardia ferruginea-Nuculana pernula sadoensisPolynemamussium alaskense ass., E: Acesta goliath-Ezocallista brevisiphonata-Astarte borealisass., F: Ezocallista brevisiphonata-Glycymeris yessoensis-Chlamys cosibensis ass., G: Chlamys
cosibensis-Chlamys swiftii ass.

Nuculana pernula sadoensis occurs where sandgets muddy. The constituents are the inhabitants
living on sandy and gravely bottom of the upper
sublittoral zone.
G. Chlamys cosibensis-Chlamys swiftii assemblage
This assemblage is found in gravel (F). It isso far found from only one locality, Loc. SW-3
which is situated near the uppermost horizonof the upper unit in the northern area. The
assemblage is dominated by pectin ids shells.

The members of this assemblage seem to be
the inhabitants of gravely bottom of the upper
sublittoral zone.
H. Other assemblages
Various assemblages not assignable to any
one of the above seven assemblages are includedin this category. A type of assemblage assignable
to this category may be composed exclusivelyof allochthonous molluscs which are mostly
contained in conglomeratic medium to coarsegrained sand and are suffered remarkably from

760. Paleoenvironment of Daishaka FormationW

NORTHERN AREA

1-2

5

.

DT-3

0J1!f"VV v ','
".'
v v
' .•.
DT-2 v v .'. "" . ""
'.

. v/

m
200

"'

Paleoenvironment of the Daishaka Formation":~: ·"":·"···v ": .::, . ' v v :"E75·•• •. ·tJ· ' .

-.. -~
vvv
vv.

----,-'.
:

.

100

o

destruction and abrasion (Loc. SW-l, SW-2, S-9,
T-l, T-2, T-3, K-2, 0-6, OT-l, OT-6, N-ll, SH-l
and SH-7). These assemblages are usually characterized by the molluscs derived from various
environments of upper sublittoral zone. Anothertype of assemblage of this category may becharacterized by the small number of individuals(Loc. N-l, N-2 and OT-4). Two species, Arcaboucardi and Macoma sp., occur from coarsegrained sand of Loc. N-l, and three species,
Macoma calcarea, Crenella columbiana andNuculana yokoyamai from fine to mediumgrained sand of Loc. N-2. Molluscs from both
localities occur sporadically and, particularly,
those from Loc. N-2 are relatively well-preserved,
indicating nearly autochthonous mode of occurrence. Molluscan fossils from Loc. OT-4 arecharacteristic in the occurrence of three articulated individuals of Panomya arctica, standing
upright in the silty medium-grained sand. In thistype, rareness does not necessarily correspondwith the poorness in informative source forenvironment at that time.

On the basis of the analysis on the stratigraphy, lithology and molluscan assemblages,
the writer attempts to infer synthetically the
paleoenvironment at the time of the depositionof the Daishaka Formation.
The lower unit: The lower unit of the Daishaka
Formation is poor in molluscan fossils, andtherefore, only a few data are actually available
for analysis on the sea level change at the timeof deposition. In fact, no fossils allowing species
identification have so far been found from thenorthern area.
In the eastern area, the lower unit overlies
conformably the Kareizawa Formation in thesoutheastern part and, to the north, successively
abuts the underlying Umanokamiyama andKareizawa Formations, and is absent in thenorthernmost part. It indicates that at the
beginning of the deposition of the Daishaka
Formation, the depositional area was confined
only to the southeastern part, and, thereafter,
was extended to the north, except the northernmost part which was subjected to subaerial
erosion and remained to be land area throughout
the time of deposition of the lower unit.
In the middle stream of the Namioka Riverof the eastern area, the coarse-grained sandstone
at the lowermost part of the lower unit contains
two species of molluscs, Arca boucardi and
Macoma sp. (Loc. N-l), indicating a relatively
shallow upper sublittoral water at the beginningof the deposition of the Daishaka Formationin the area around the middle stream of theriver. Along the same river, the fine to mediumgrained sandstone overlying the coarse-grainedsandstone mentioned above contains sporadicallythree species of molluscs, Macoma calcarea,
Crenella columbiana and Nuculana yokoyamai(Loc. N-2). The occurrence of three species may
indicate that the sea at the time was under lower
sublittoral environment.
The fine to medium-grained sandstone of thelower part of the lower unit abruptly changes
upward into the conglomeratic medium to

76

Ryoichi TABUKI
Table 3. Recent ecological data of some molluscan species.
1: Oyama (1973),2: Habe and Ito (1965), Habe (1975a, 1975b, 1977).
Bathymetric

BottomSpeciesGeographical distribution

range

Acila vigilia

2 Choshi to KurU Is., Japan Sea

100 to SOOm

Ennucula tenuis
Nuculana pernula sadoensis
N.
yokoyamai

2 northward from Choshi, Japan Sea

intertidal to 250m

sand

2 northward from Sagami Bay, Japan Sea

100 to 200m

sand, mud1 P 33-40, J 32-41

N3-4B2-4

N.

ikebei2 Kyushu to southwestern Hokkaido

50 to 450m

cS
sand, mud

2 Sagami Bay to Hokkaido

100 to I030m

mudsand, mudRobaia rabai

2 western Hokkaido, Japan Sea

100 to 250m

Yoldia notabilis

1 P 37-45, J 32-46

N1

2 Tohoku to Okhotsk Sea

Portlandia japonica
Area boucardi
Glycymeris yessoensis

charactersand, mud20 to 200m
2 Kyushu to Honshu, Japan Sea, East China Sea 10 to 300m
2 Taiwan to Hokkaido
intertidal to 20m
1 P 34-44, J 347-46
N1

sand, mud

2 Tohoku to Kuril Is., Japan Sea

sand

5 to 30m

sandrock. gravel

Limopsis tokaiensis

I P 35-40, J 32-41

Mytilus crassitestus

1 P 31-42, J -42

NO-l

2 Kyushu to southern Hokkaido

intertidal to 20m

rock

Modiolus margaritaceus

2 Kyushu to Hokkaido, Japan Sea

30 to 450m

gravel, shell, sandSolamen spectabilis

1 P 32-36, J 33-41

N2

Monia macroschisma

2 Kyushu to Tohoku, Japan Sea, East China Sea 30 to 300m
2 northward from Tohoku, Japan Sea
50 to 560m
2 northward from Tohoku
intertidal to 20m
2 northward from Tohoku
shallow sea

Acesta goliath

I P 34-41, J 35-42

Polynemamussium alaskense
Chlamys swiftii

Limaria hakodatensis
Lim-atula v1adivostokensis

rock, gravel
rock, gravel

N4B

R, 5

100 to 1390m

sand. mud1 P 25-42

NI-2

gS, 5, M

2 Kyushu to southern Hokkaido

5 to 100m

sand

2 northward from Sagami Bay, Japan Sea

50 to 350m

sand, mud

Lucinoma annulata

1 P 31-42, J -41
1 P 31-64, J 32-41

2 northward from Kyushu
2 Kyushu to Hokkaido, Japan Sea
I P 33-42, J

32-42

2 Kyushu to southern Hokkaido
Miodontiscus nakamurai
Astarte borealis

sand, mud2 Shikoku to southern Hokkaido. Japan Sea

Thyasira tokunagai
Venericardia ferruginea,/Isand, mud10 to 150m

mud

5 to SOm

mud

[N3l

151

50 to 400m

sand, mud2 Nemuro (Hokkaidol
1 P 37-50, J 35-46
2 northward from Tohoku

10 to 360m

sand, mud2 northward from Hokkaido. Japan Sea

100 to 200m

sand, mud

Serripes groenlandica

2 northward from Hokkaido, Japan Sea

10 to BOrnsand. mudA.

a1askensis

Spisu1a voyi alaskana

2 northward from Choshi

intertidal to 120m

sand, mudCadella lubrica

2 Tohoku to Hokkaido

subtidal to Sam

sand

Macoma calcarea

2 northward from Shikoku

intertidal to 1000m sand, mudM.

2 Kyushu to Hokkaido

intertidal

1 P 37-45, J 34-46

N1

2 Tohoku to Kuril Is.

subtidal to 20m

sand

I P 38-45. J 35-46
2 Tohoku to KurU Is.
1 P 36-45, J 38-46
2 Tohoku to Kuril Is.

Nl-3

mS. sMsubtidal to 20m
Nl-2

sand, mudcontabulata

Hercenaria stimpsoni
Call ithaca adamsi
Ezocallista brevisiphonata

subtidal to 30m

mudgravel. sandMya japonica

2 northward from Tohoku

subtidalsand. mud

Caryocorbula venusta

1 P 31-42, J -43

NO-4B2S, mS

2 Kyushu to Hokkaido

intertidal to 200m

sand

2 northward from Hokkaido, Japan Sea

50 to 200m

mud

Panomya beringianaP•

arctica.Puncturella nobilis

2 northward from Hokkaido
I P 39-46, J 36-46

N1

2 northward from Tohoku

intertidal to 50m

gravel, sand

Homalopoma amussitatum1 P 38-51, J 36-46

Cocculina japonica

2 Choshi to Sakhalin
2 northward from Tohoku, Japan Sea

subtidal to 20m
50 to 200m

wood fragment etc.

Turrite11a fortilirata

2 Tohoku to Kuri1 Is., Japan Sea

Neverita reiniana

1 P 26-35, J -37

50 to 200m
NI-3

,M

10 to 30m

sand, mud

Cryptonatica janthostomoides

2 southward from Boso Pen.
1 P 31-42, J -43

N1-2

5, mS

2 Kyushu to Hokkaido

gravel, sandsand, mud10 to Samsand, mudMohnia yanamii

2 Japan Sea (200m)

Fusitriton oregonensts

2 northward from Sag ami Bay, Japan Sea

30 to 300m

mud

Antiplanes contraria

2 Boso Pen. to Okhotsk Sea

50 to 200m

Turbonilla shigeyasui
Cadulus opportunus

1 P 34-35, J 33-34(NO-I)

Dentalium rhabdotum

2 Sag ami Bay to Sea of Kashima

100 to 700m
2 Kyushu to Honshu, Japan Sea, East China Sea 50 to 620m

ImSlsand, mud
mud

760.

Paleoenvironment of Daishaka Formationcoarse-grained sandstone of the upper part, andthe slumping deposits are characteristically foundat the lowermost horizon of the upper part. In
the upper stream of the Otanizawa River of theeastern area, molluscan fossils occur abundantlyin the conglomeratic medium to coarse-grainedsandstone of the uppermost part of the lower
unit. The molluscs thought to be nearly autochthonous belong to the members of E assemblage (Loc. OT-2) and are mostly the inhabitantson sandy and gravely bottom of upper sublittoralzone. Molluscs occurring in the fine to mediumgrained sandstone at almost the same horizonin the middle stream of the Shoheizu River are
mostly the species of D assemblage, suggestingthat the sea became deeper in the area aroundthe Shoheizu River.
The upper unit: In the west flank of the
Otakizawa Anticline of the northern area andin the area south of the Shoheizu River of theeastern area, the lower part of the upper unitof the Daishaka Formation is dominated bycoarse sediments (medium to coarse-grained
sand and gravel). On the contrary, in the eastflank of the Otakizawa Anticline of the northernarea and in the area around the Shoheizu Riverand north of the river of the eastern area, finesediments (silt and fine to medium-grained sand)are sometimes found in the lower part of thisunit.
In the area around the Magonai River andnorth of the river of the eastern area, fine sediments are dominant stratigraphically between
the key beds DT-6 and DT-7, and coarse sediments predominate between DT-3 and DT-6; andvice versa in the area south of this river. The
molluscs in the coarse sediments are dominatedby the species belonging to the upper sublittoral
E and F assemblages. On the other hand, thefine sediments are deposited in relatively deep
lower sublittoral sea. This is indicated by theoccurrence of the A, C and D molluscan assemblages in such fine sediments. This indicates
that, before the deposition of DT-6, the area
south of the Magonai River was covered withthe relatively deep sea, and thereafter turned
into the area where upper sublittoral environ-77

ment predominated, and that, on the contrary,in the area around the Magonai River and northof the river, before the deposition of DT-6, therelatively shallow sea existed, and the Tsurugasaka Spa and its environs, where the sediments
corresponding to DT-6 and the lower horizon
are absent, might have been an area of denudation at that time, but after the deposition of
DT-6, as depositional area spreaded to the north,
the sea became deeper.
In the northern area, in the east flank of the
Otakizawa Anticline, during the period between
the deposition of DT-3 and DT-7, fine sediments
were accumulated, alternating with coarse
sediments, in relatively deep lower sublittoral
sea represented by the B, C and D assemblages.
In the west flank of the anticline, all the molluscan fossils were found as allochthonous shell
beds. These molluscs are the inhabitants of
the intertidal and upper sublittoral zones (ex.
Mytilus crassitestus and Ezocallista brevisiphonata) (Loc. SW-l). The sediments are coarse
and gravely, also indicative of very shallow
environmet. Therefore, as a whole, at that time,
the sea which covered the northern area became
deeper from the west to the east.
The upper part of the upper unit overlying
DT-7 is composed of the medium ot coarsegrained sandstone both in the eastern and northern areas. The molluscan fossils contained areallochthonous in many cases, but are mostly a
mixture of upper sublittoral molluscs such as
Glycymeris yessoensis and Area boucardi, indicating that the sea became shallower after thedeposition of DT-7. Coarseness of the sedimentsin this part also supports the conclusion. In theuppermost part of the formation, peat and peaty
mud are found at many places both in the easternand northern areas. It suggests that the sea atthat time became much shallower, and eventhe change of depositional environment, frommarine to brackish or freshwater, might haveoccurred.
Thereafter, in the area around the Na~iokaRiver and south of the river, deposition of theDaishaka Formation was succeeded conformably
by the pyroclastic sediments of the TsurugasakaRyoichi TABUKI

78

Formation. However, the area north of the
Namioka River turned into the erosional area
and the Tsurugasaka Formation unconformably
overlies the Daishaka Formation.
References
Habe, T. (1975a): Mollusca I, chiefly from Japan.
301 pp., 74 pIs. Gakken Co., Ltd. Tokyo. (inJapanese)--(1975b): Mollusca II, Chiefly from Japan.
294 pp., 80 pis. Gakken Co., Ltd. Tokyo.
(in Japanese)--(1977): Systematics of Mollusca in Japan.
Bivalvia and Scaphopoda. 372 pp., 72 pis.
Hokuryukan Tokyo. (in Japanese)--and Ito, K. (1965): Shells of the world incolour. Vol. 1, The northern Pacific. 164 pp.,
56 pis. Hoikusha Osaka. (in Japanese)Iwai, T. (1962): The Pliocene dep'osits andmolluscan fossils from the northeast marginof the Tsugaru Basin, Aomori Prefecture,
Japan. Saito Ho-on Kai Mus., Res. Bull.,no. 31, p. 35-46.
--(1965): The geological and paleontologicalstudies in the marginal area of the Tsugaru
Basin, Aomori Prefecture, Japan. Bull. Educ.
Fac., Hirosaki Univ., no. 15, p. 1-68, pis.
12-20.
Kataoka, J. (1957): Bryozoa from the Daishaka
Formation (Pliocene), Minami-Tsugaru-Gun,
Aomori Prefecture. Trans. Proc. Palaeont.
Soc. Japan, N.S., no. 28, p. 143-153, pI. 22.

Kato, 1. and Taguchi, K. (1959): The Geologyof the southwest part of Aomori City. Publ.
Aomori Pref. Govern. (in Japanese)
Koto, J. (1957): Brachiopoda from the Daishaka
and Tsurugasaka fossil zones, MinamiTsugaru-Gun, Aomori Prefecture. Trans.
Proc. Palaeont. Soc. Japan, N.S., no. 25,
p.7-10.
Nomura, S. and Hatai, K. (1935): Pliocene Mollusca from the Daishaka shell-beds in thevicinity of Daishaka, Aomori-ken, Northeast
Honsyu, Japan. Saito Ho-on Kai Mus., Res.
Bull., no. 6, p. 83-142, pis. 9-13.
Otuka, Y. (1939): Mollusca from the Cainozoic
System of eastern Aomori Prefecture, Japan.
Jour. Geol. Soc. Japan, vol. 46, no. 545,
p. 23-31, pI. 2.
Oyama, K. (1973): Revision of Matajiro Yokoyama's Type-Mollusca from the Tertiary and
Quaternary of the Kanto Area. Palaeont.
Soc. Japan, Spec. Pap., no. 17, p.1-147,
pis. 1-57.
Tabuki, R. (1980): The Ostracode Fauna fromThe Daishaka Formation. 55 pp., (Master
Thesis)Yamamoto, G. and Habe, T. (1958): Fauna ofshell-bearing molluscs in Mutsu Bay. Lamellibranchia (1). Bull. Marine Bioi. Sta. Asamushi, Tohoku Univ., vol. 9, no. 1, pis. 1-5.
--and - - (1959): Ditto. Lamellibranchia(2). Ibid., vol. 9, no. 3, p. 85-118, pis.
6-14.
- - a n d - - (1962): Ditto. Scaphopoda and
Gastropoda (1). Ibid., vol. 11, no. 1, p.
1-20.

*

I$R~~ (7) *~~lfi (fftJr-:l!!tJrkVC) (7) ti~Jj!:~~lfi t~ ~ 'i .n ~ ft {tEn(7) n~mnx::to
J: l1:1lfff'lJj!~~1fU t:. t.::.o t 'b~ ~ "*~nP~~ilJ4'kIn" (7) El1:3<.ft El1:t~~t ,n~ c l.. -C,
rlllli:lti'la*(7).lt~i¥J$~t.(Jft.'i(t~1:,~, l.. -Ct ,t.::. c ,~hh~ 4 ,,?(7)n~ c J:lllli:lti'la*(7).lttl'ti¥Jm
fJit.(Jft.'i(t~1:,~, l.. -c~,t.::. c,~b.n~ 3 ,,?(7)n~~~l6t.::.o *R!!ir~llllt~"?~ '-C Itft{tE(7) T-

j1ltz U, t (7)(7), rllllt~.lji~-t ~$~:IlfJ{4'kIItrlllli:lti'la*t~. J:llll(7)R4~JI113l1!(7)ge~ u.::.mrllll
i:lti'la* t~:IlfJ{ u.::. c ~ ~ & .n ~ ;\1IlfJi:ll.4'kI1.l ~Je~-t ~ 0 *llll~jjj!G-eft. .: (7) $~:Ilfif4'kl (7):Ilfif
U.::..lt~i¥J~~ 'i'lajjj!G1.l~. .: (7)~j!1l(7) ? 'l::> t~. ,*,:!k:llll1.l' & ~tllll"''f$iIJ U'::' o -1], ~tllll~jjj!G-e
ft, *llll-erlllli:lti'la*(7);\1IlfJi:llfJ{4'kI1.l~.lji~ l... g§llll-eftitlJF,,'*. J:lllli:lti'la*(7) JUii~~trm~~:Il.4'kI~J:lllli:lti'la*K:IlfJ{l..~c~~&.n~0J:~llll(7)rllllK~, i'Ia~M(7):IlfJ{4'kI~:IlfJ{4'kI1.l;Je~-t~0 -tt.(b'l::>. ~tllll~jjj!G-C:·lti'la1.l~g§I.1,&*t~r"JI.1'-:> -C(:kmt~~(7)1&. *1\1i7t;fpjjj!G~,*I.1;~i'Ia{t l.. -ctit~o<t.(-:> -c~,t.::.-t
m'!k?'Ii-

Trans. Proc. Palaeont. Soc. Japan, N. S., No. 130, pp. 79-84, pl. 15, July 15, 1983

761. SOME BIVAL YES FROM THE LOWER JURASSICKURUMA GROUP OF CENTRAL JAPAN*
MICHIHARU GOTO
Toyama Science Museum, Toyama 930-11

Abstract. Several bivalve fossils were newly obtained from the Lower Jurassic
Kuruma Group in the eastern part of Toyama Prefecture, north-central Japan. The
followi.n g species are described in this article: Nuculana (Dacryoma) konishii
Hayaml, Nuculana (Dacryomya) cf. konishii Hayami, Pteroperna kitadaniensis
Goto n. sp., Bakevellia (Neobakevellia) sp.

Introduction

confined to Early Jurassic. The abundant bivalvesof Crenotrapezium and Eomiodon are generally
found from the Jurassic-Cretaceous sediments
but not from the Triassic (Hayami, 1958).
There are lower Jurassic sediments in several
scattered areas of the Inner Zone of Japan. They
are, from the east to the west, the Iwamuro
Formation in Gunma Prefecture, the Yamaoku
Formation in Okayama Prefecture, the Higuchi
Group in Shimane Prefecture and the Toyora
Group in Yamaguchi Prefecture. Among them
the Iwamuro Formation is found about 150 km
to the east of the present area on the opposite
side of the Fossa Magna, and is regarded as was
deposited under similar sedimentary condition.
Nuculana konishii was originally describedfrom a marine bed (Y 2 member) of the Yamaoku
Formation (Konishi, 1954; Hayami, 1961).
Therefore, the present discovery seems to indicate that not only brackish water but also marine
bivalves are intimately related between the
Kuruma Group and the Yamaoku Formation.
The Kuruma Group, as noticed above, isbrackish water sediments in general, but theupper part, at least, the Teradani Formation isthought to be neritic, as indicated by the occurrence of ammonites and such purely marine
bivalves as Plagiostoma and Nuculana.
Doctor Itaro Hayami of the University of

The Kuruma Group is a thick series of clastic
sediments consisting of sandstones and mudstones
together with some layers of conglomerates, andcovers an area of more than 180 square kilometers. It exceeds 6,000 m in thickness, and isdivided, in ascending order, into the Jogodani
Kitamatadani, Negoya, Teradani, Shinatani',
Otakidani and Mizukamidani Formations (Kobayashi et al., 1957; etc.). In some cases the sediments are carbonaceous, and thin seams of coal
are intercalated.
Among the fossils contained neomiodontids
are ubiquitous, while the bakevelliids are locallyabundant in argillaceous sediments. They showthat the series of sediments was deposited
generally under brackish water conditions.
Fossils of land plants such as Cladophlebis
and Dictyophyllum are also known at various
horizons.
Important is the occurrence of the ammonites
from the Teradani and Otakidani Formations.
According to Sato (1955), Amaltheus sp. andCanavaria sp. from the Teradani Formation showa late Pliensbachian age, while Grammoceras sp.
from the Otakidani Formation suggests a latest
Toarcian age. The other formations are almost
barren of index fossils, but their ages may be* Received June 18, 1982
79

Michiharu GOTO

80

"+
,

-

Toyama- - - - , - - -Pref.

- - .,.. .... -

-._-\
"

,

"

o

MATSUMOTO

O_ _ _ _1Km

Text-fig. 1. Index map of the localities of Early Jurassic bivalve
fossils in northeast Toyama Prefecture

Tokyo instructed the author in the identificationof specimens and read through the manuscript.
Professor Noboru Yamashita of the Shinshu
University supervised the field survey of theauthor and read through the manuscript of thisintroduction. Mr. Takashi Fujita of the same
University prepared the photographs of thefossils here described. The author expresses his
sincere gratitude to them.

Subgenus Dacryomya Agassiz, 1840

located at about one-third of length from front(P. 3114, 29.8 mm long, 11.5 mm high, 4.8 mm
thick); anterior margin short and rounded, while
postero-dorsal one is unusually long; posterior
rostrum elongated, gently tapered backwards,
scarcely bending upwards; surface marked with
subvertical striae which are especially wellmarked on the anterior part of posterior rostrum.
Main body marked with close striae; escutcheon
narrow. Only a specimen is at hand. In the outline and characteristic surface ornaments, this isprobably identical with Nuculana konishii fromthe Yamaoku Formation (Hayami, 1961).
Occurrence:-Mudstone of the upper part of
the Teradani Formation at the Teradani, Asahimachi, Shimoniikawa-gun, Toyama Prefecture.

Nuculana (Dacryomya) konishii Hayami

Nuculana (Dacryomya) cf. konishii Hayami

Plate 15, Figure 1

Plate 15, Figure 2

1961. Nuculana (JJacryomya) konishii Hayami,
p. 116, pI. 16, fig,. 1.

An external mould is at hand. This is very
similar to the preceding species in the surface
ornamentation and outline (P. 1106, 40.8 mm *long, 15.8 mm + high, 6.0 mm thick), but theumbo is located more posteriorly. The shell size
is somewhat larger in comparison with the type

Description
Family Nuculanidae
Genus Nuculana Link, 1807

Shell spoon-shaped, highly rostrated, cuspidated backwards. Main body Is ~ubelliptical andmoderately inflated; umbo is not very prominent,

761. Bivalves from the Jurassic Kuruma Group81

J A PANSEALEGEND
Ichiburi

1

.3
k«d2
4

7

8

··· · · 9··········ca.... ..... ".........

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

oText-fig . 2.

2km

Geological map of northeast Toyama Prefecture

1. Shiratoriyama Formation, 2. Kurobishiyama F., 3 . Shiritakayama F., 4 . Mizukamidani F ., 5. Otakidani F., 6 . Shinatani F ., 7. Teradani F ., 8 . Negoya F., 9 . Porphyrite, 10 . Green schist, 11. Fault

82

Michiharu GOTO

Table 1:Stratigraphic classification of the Kuruma Group
Formation".

0......

Shiritakayama F.

0
E-t
r:<I
E-t

Shiratoriyama F.

~

Rock facies

conglomerate
sandstone
mudstone

Kurobishiyama F.

Mizukamidani F.
700 m +

sandstone
mudstoneconglomerate
sandy mudstone

Onychiopsis

Otakidani F.
450 m

mudstonesandy mudstonesandstone

Grammoceras
Hammatoceras
Belemnites
Gera trigon ia

Shinatani F.
700 m +

sandstone
mudstoneBakevellia
Isognomon
Protocardia
Mytilus
Crenotrapezium
EomiodonPleuromya
Equisetites

Teradani F.
250 m

sandy mudstone

Negoya F.
1,000 msandstone
mudstoneBakevellia
Mytilus
EomiodonCrenotrapezium

Kitamatadani F.
2,000 m?

sandstone
mudstone

Chlamys
Bakevellia
Crenotrapezium
Cardinioides
Eomiodon

Jogodani F.
700 m?

conglomerate
sandstone
mudstone

d

<
::g
::>
~
::>
~

Fossils?
Renge
metamorphics

green schist

Amaltheus
Canavaria

761. Bivalves from the Jurassic Kuruma Groupof Teradani specimens.
Occurrence:-Mudstone of the middle part of
the Negoya Formation at the Kitadani, Asahimachi, Shimoniikawa-gun, Toyama Prefecture.

83

that the present species belongs to Pteropema.
Occurrence:-Black mudstone at the lower (?)
Pliensbachian Negoya Formation of the Kitadani,
Asahi-machi, Shimoniikawa-gun, Toyama Prefecture.

Family Pteriidae
Family Bakevelliidae King, 1850

Genus Pteropema Morris and Lycett, 1853

Genus Bakevellia King, 1848

Pteropema kitadaniensis Goto, new species

Subgenus Neobakevellia Nakazawa, 1959

Plate 15, Figures 3-4

Description:-Shell is small, inequivalve, pteriform, left valve more strongly convex than right.
Hinge-margin is straight, fairly long. Anterior
wing is large, triangular in right valve, subtriangular with a rounded anterior extremity in left
valve. Posterior wing with three longitudinalridges is long, sharply pointed backwards, withremarkably sinuated posterior margin; umbo
located at about a fifth of hinge-line from theanterior end, fairly protruded above hinge-margin
in left valve, but not in right; surface marked
with fluctuated concentric lamellae.
Observation and Comparison:-Two specimens, each of which is represented by internaland external moulds, are at hand. In the outline,
these specimens are similar to some immature
specimens of Bakevellia. Judging from theligament structure, they are different from
Bakevellia which is characterized by multivincular ligament pits. The development of
longitudinal ridges on the posterior wing indicate

Bakevellia (Neobakevellia) sp.
Plate 15, Figure 5

An internal mould of left valve is at hand.
Shell large (P. 0092, 77.2 mm long, 66.5 mm
high, 13.2 mm thick, Obliquity 40), pteriform;
anterior wing is relatively small; posterior one
extends backwards; posterior margin remarkably
sinuated below posterior wing; umbo located atabout one-fifth of hinge-line from the anterior
end, not protruded above hinge-margin in the left
valve; anterior margin nearly straight; the left
valve convex strongly; ligament area wide, withmultivincular ligament pits numbering six orseven at least. This is different from hitherto
described species of Bakevellia from the Kuruma
Group (Hayami, 1957) in the shape, but it may
be safely referable to the genus.
Occurrence:-Sandy mudstone of the Teradani
Formation near the mouth of Kawagurodani,
Asahi-machi, Shimoniikawa-gun, Toyama Pre-

Table 2. Measurements in mm, Pteroperna kitadaniensis Goto. n. sp.
Specimen

LengthHeightThickness

Obliquity

Holotypeleft in. mould

23.6

13.1

4.4

45°

Holotypeleft ex. mould

23.6

13.1

4.4

45°

Paratyperight in. mould

25.4+

13.2

3.4

45°

Paratyperight ex. mould

23.1+

14.1

3.4

45°

84

Michiharu GOTO
References

Hayami, I. (1957): Liassic Bakevellia in Japan.
Japan. Jour. Geol. Geogr., vol. 28, no. 1-3,
p. 47-59, pIs. 2, 3.
- - (1958): A review of the so-called Liassic
cyrenoids in Japan. Japan. Jour. Geol.
Geogr., vol. 29, no. 1-3, p. 11-27, pI. 2, 3.
--(1961): Pelecypods from the Liassic Yam aoku Formation in west Japan. Trans. Proc.
Pa/aeont. Soc. Japan. n.5., no. 43, p. 113116, pI. 16.
Kobayashi, T., Konishi, K., Sato, T., Hayami,
I. and Tokuyama, A. (1957): On the Lower

Jurassic Kuruma Group. Jour. Gecil. Soc.
Japan, vol. 63, p. 182-194. [in Japanesewith English abstract]
Konishi, K. (1954): Yamaoku Formation (aJurassic deposit recently discovered in
Okay am a Prefecture). Jour. Geol. Soc.
Japan, vol. 60, no. 707, p. 325-332. [inJapanese with English abstract]
Sato, T. (1955): Les ammonites recueillies dansIe groupe de Kuruma, nord du Japon central.
Trans. Proc. Palaeont. Soc_ Japan, n.s.,
no. 20, p.111-118, pI. 18.

Negoya w,IJf.:fr, Teradani ~:fr, Kawagurodani JII~:fr, Shinatani til:fr. Otakidani *~:fr.
Agero J:K~. Ichiburi m~, Tomari iE!, Asahi-machi iWJ E lilT, Shimoniikawa-gun "ftrJllt'll"ftlll ~ "- '7 **.~F~~Jt:O)=&Yl1Jl: '/i{LlJ~~~t*tlllzo.p·L.' c L -c. tr~!Pr<, ~!J!T!Pr<O)~~~fHt
JliI;::11"f$ ~ "- '7 **.~~~/M:t;(fi L. M!f'-I.o{t:ozoI1 CID. illi1#aj!l=&JHl'iil~~Jt:-t G .: c I:ttJlliiil'l?~ I?n -n ,t.:.o 4-@)'liH1J~;rftr}II:/lIlljiJJ E lHJ*fJIIJ:VfEO)~:fr Ut:fr J: I) *,1iifa~zo15tr
3 fi1JlO)=&~iI;Je5! ~nt.:.o 1 fJTfi~15tr.:cO) 3 Jiij 3 fizo~c~-t Go Nucu[ana (Dacryomya)
konishii, Nucu[ana (Dacryomya) d. konishii, Pteroperna kitadaniensis n. sp .• Bakevellia(Neobakevellia) sp. .: 0) Je5! I;:: J: I). *.~~~iI'G 11iJ!J'iifaj!l=&~Mt-=ft"(,f1f.l:t<l!#a~=&~ >bJt:I±l-t G .: c iI~1J)3 GiI'IUJ:"? t.:.o ~ I? KUli1i J: I) IlUJLlJ~~O)LlJ~@ c *.~@~ c 11{t:o~O);I1<ill1f1:J: I) W~tJ:l*lffiiJ;;l;G c~.n -C*t.:.iI~. Nucu[ana (Dacryoma) konishii O)Je5!11<.

.:c.nzo~#ftG-~0)~~c~~G~6?0~~~~

Explanation of Plate 15
Nuculana (Dacryomya) konishii Hayami
Fig.1. Right valve (P. 3114), x1.2. Loc. 1
Nuculana (Dacryomya) cf. konishii Hayami
Fig. 2. Left valve (P. 1106), x1.2
2a: external mould, 2b: Rubber cast from the external mould. Loc_ 3.
Pteroperna kitadaniensis Goto n. sp.
Fig. 3. Left valve (P. 1102), holotype, x1.2
3a: internal mould, 3b: external mould_ Loc.2
Fig. 4. Right valve (P. 1102), paratype, x1.2
4a: internal mould, 4b: external mould. Loc_ 2.
Bakevellia (Neobakevellia) sp.
Fig. 5. Left valve (P. 0092), x1.2. Loc. 4.

GOTO : Bivalves from the Jurassic Kuruma Group

Plate 15

Trans. Proc. Palaeont. Soc. Japan, N. S., No. 130, pp. 85-95 pis. 16-20, July 15, 1983

762. CRETACEOUS NAUTILOIDS FROM HOKKAIDO - II
PART 2. THREE NAUTILOID SPECIES FROM THE SANTONIAN
AND CAMPANIAN OF HOKKAIDO*TATSURO MATSUMOTO
c/o Department of Geology, Kyushu University 33, Fukuoka 812
and
KIKUWO MURAMOTO
Mikasa Museum, Mikasa, Hokkaido 068-22

Abstract. This is Part 2 of a monograph of the Cretaceous Nautiloids from
Hokkaido being published in series. It contains the description of three species, ofwhich the first is new and assigned to Kummeloceras (established in Part 1 *), thesecond is identified with Cymatoceras pseudoatlas (Yabe et Shimizu), originally described on a specimen from Kyushu, and the last is a new species of Cymatoceras
allied to and possibly evolved from C. saussureanum (Pictet) of an earlier age.
The first two occur in the Lower Santonian Zone of Inoceramus amakusensis
and the last in the Middle Campanian Zone of Sphenoceramus schmidti and seems
to range down to the Lower Campanian Zone of Sphenoceramus orientalis. Someremarks are given on the Cymatoceratidae, proposing a new genus.

meloceras but different from the two species ofthe same genus from the Turonian and theConiacian of Hokkaido which were described inPart I. The second is identified with the speciesof Cymatoceras described years ago from Kyushu.
These two occur in the Lower Santonian Zoneof Inoceramus amakusensis. The last is a new
species of Cymatoceras and of Lower (?) to
Middle Campanian age.
In connexion with Cymatoceras one of us(T. M.) will give general remarks on the family
Cymatoceratidae.

Introduction
As is well known, ammonoid cephalopods
occur abundantly in the Santonian and theCampanian of Hokkaido. In contrast with this,nautiloids have been found rather rarely from thesame sequences. This is probably due to collection failure and does not necessary mean theabsolute scarceness. We hope that the descriptions of three species in this paper would becomea start towards an intensive study of morematerial in the future.
One of the three species is referred to Kum-

Palaeontological Description* Part 1 is in T. Matsumoto (1983): Cretaceous

Family Eutrephoceratidae Miller, 1951

Nautiloids from Hokkaido - 1. Trans. Proc.
Palaeont. Soc. Japan, n.s., no. 129, p. 9-25,
pis. 4-9.
* Received July 2, 1982

Genus Kummeloceras Matsumoto, 1983

Remarks:-See Part I for the definition and85

86

Tatsuro MATSUMOTO and Kikuwo MURAMOTO

the phylogenetic position of this genus.

t

Kummeloceras kamuy sp. nov.

PI. 16, Fig. 1; Text-figs. 1, 2
Material:-Holotype

Me. Hbo-2015, consist-ing of the phragmocone and a part of the bodychamber. Another specimen, GK. H5925, is
probably a secondarily distorted example of thepresent species.
Description:-The shell is fairly large. The
holotype is about 132 mm in diameter, but it
has only a part of the body-chamber for about
90 0 • Should the body-chamber assumed to be as
long as 150 0 , the shell diameter would exceed
150 mm. Another specimen, GK. H5925, is 150
mm in diameter at the end of the phragmocone,
although it is measured under distorted state.
The whorl is rounded in cross-section, somewhat broader than high, with B/H=1.17 in theholotype. The maximum breadth is somewhat
below the mid-height. The umbilicus is narrow,nearly 10 per cent of the diameter, surrounded
by a steeply inclined, slightly incurved wall anda rounded shoulder.
The outer surface of the shell is smooth,
except for fine growth-lines, which show arather gentle ventral sinus.
The septa are widely spaced; 6 or 6.5 being
counted in a half whorl. The suture is fairly
sinuous. The last suture has almost imperceptible
ventral lobe, being nearly straight on the venter,but the earlier ones (e.g. the last 5th or 6th)
show a very shallow and broad ventral lobe. The
lateral lobe, though shallow and broad, is more
distinct in the latter. The saddle at the umbilicalshoulder is indistinct or incipient and the sutureline runs nearly radially on the umbilical wall.

Text-fig.!. Kummeloceras kamuy sp. nov.
Diagrammatic whorl-section (body chamber);the last and the last 6th external sutures of theholotype. Bar = 10mm.
(T. Matsumoto delin.)oText-fig. 2. Kummeloceras kamuy sp. nov.
Restored whorl-section of paratype, GK. H5925,
showing the position of siphuncle. Bar = 10 mm.
(T. Matsumoto delin.)

The siphuncle is subcentral, passing througha point slightly below the midst of the dorsoventral median-line of a septum, as shown in GK.
H5925.
Comparison:-The present species is similar to

Explanation of Plate 16
Fig. 1. Kummeloceras kamuy sp. nov. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Page 86
Holotype, MC. Hbo-2015, ventral (a) and lateral (b) views, xl.
Photos (pIs. 16-20) by courtesy of Dr. M. Noda.

762. Cretaceous Nautiloids

87

Table 1. Measurement (in mm), Kummeloceras kamuy sp. nov.
Specimen
Holotype

DiameterUmbilicus

131.5 (1)13.0 (.098)

GK. H5925 (deformed)
E. kobayashii

140.0 (1)

13.4 (.095)

Eutrephoceras sUblaevigatum (d'Orbigny, 1850)[=Nautilus laevigatus d'Orbigny (1840, p. 84,
pI. 17, figs. 1-4)] in the broadly rounded whorlsection and the subcentral siphuncle but distinguished by its more sinuous and more distantsutures and opened instead of almost closed
umbilicus.
With respect to its somewhat sinuous sutures,
this species differs considerably from the typical
species of Eutrephoceras, such as E. dekayi(Morton), E. sublaevigatum (d'Orbigny), E.
sloani Reeside, 1924 (see Miller, 1947, textfig. 6) and is closer to Kummeloceras yamashitai
Matsumoto and K. splendens (Blanford) (seePart 1). Therefore we refer it to Kummeloceras
rather than to Eutrephoceras.
Kummeloceras kamuy is distinguished fromK. yamashitai Matsumoto and K. yezoense
Matsumoto (both described in Part 1), from the
TUronian and Coniacian of central Hokkaido
respectively, by its more rounded, broader whorl
and much more distant septa.
The holotype of the present species resembles
that of E. kobayashii Matsumoto (1967, p. 164,
pI. 3, fig. 1; text-figs. 1, 2), from an uncertain
horizon of Urakawa (southern Hokkaido) in thegeneral aspects, but the fonner has distinctly
more sinuous and more distant septa (6.5 perhalf-whorl as compared with 11 or 12 in thelatter) and the lower position of the siphuncle(somewhat below, instead of above, the midstof the dorso-ventral median-line). The whorl issomewhat broader in the fonner than in thelatter, but the difference of B/H between thetwo (1.17 as compared with 1.08) is not great.
Although the available specimens are few in both
species, the sinuosity and the density of the
septa and the position of the siphuncle at thecorresponding growth-stage should be consider-

HeightBreadth

B/H
1.17

77.8 (.59)

91.0 (.69)

84.0

95.0

1.13

83.0 (.59)

90.0 (.64)

1.08

ably reliable criteria. Therefore, this species isdistinguished from E. kobayashii. For the same
reasons, GK. H5925 is better regarded as a
distorted example of the present species.
The present species is similar to E. darupense(Schluter) (1876, p. 176, pI. 49, figs. 4, 5)(Wiedmann, 1960, p. 157, pI. 21, figs. C, D;
pI. 23, figs. F, P; text-fig. 2), from the Upper
Cretaceous of Gennany, in the distant sutures,but is distinguished by its more sinuous sutures,subcentral (instead of ventral) position of thesiphuncle, more rounded whorl-section and anarrowly opened (instead of closed) umbilicus.
Incidentally, Wiedmann (1960) regarded the
SchlUter's (1876, pI. 48, figs. 3-5) specimen of"Nautilus neubergicus" from the Emscher-Mergel
as identical with E. darupense. This is, in our
opinion, doubtful, because it has denser septa.
It is more closely allied to, if not identical with,
E. kobayashii, although it is smaller than theholotype of the latter. There is a similarly small
specimen in the Collection of Mr. Y. Kawashita
from the Coniacian of the Ikushumbets area,
central Hoddaido, which can be provisionallycalled E. sp. aff. E. kobayashii. Anyhow. weagree with Wiedmann (1960) in regarding that
SchlUter's N. neubergicus as distinct from N.
neubergicus Redtenbacher (1873, p. 97, pI. 22,
fig. 4) [=N. sowerbianus of Hauer (1858, p. 14,
pI. 1, fig. 12) (non d'Orbigny)], from the Gosau
Group of Austria, the latter of which should be
assigned to Angulithes.
Occurrence:-The holotype was obtained by
one of us (K. M.) from the Pisshiri-zawa, abranch of the Deto-futamata, a tributary to theRiver Haboro, northwestern Hokkaido. According to Ueda et al. (1962), the locality can be
assigned to the Santonian. Ueda et al. listed
Eutrephoceras sp. at their loco CK. 63 of the88Tatsuro MATSUMOTO and Kikuwo MURAMOTO

Deto-futamata, Unit A of their subdivision,
which is Lower Santonian (Zone of Inoceramus
amakusensis). Their specimen is unfortunately
missing at present.
GK. H5925 was obtained by Mr. Hiroharu
Kokubu in one of the floated nodules in thestream called Sanushibe, under the bridge ofSanushi at Inasato, Hobetsu area, central Hokkaido. The lithology (calcareous mudstone) of
the nodule suggests the derivation from theSantonian part of the Upper Cretaceous in thatarea (see a geological map of fig. 1 in Matsumoto
et al., 1979). Mr. Kokubu kindly presented thespecimen to one of us (T. M.), which is now
kept in the Geological Collections of Kyushu
University.
The specimen in Mr. Mitsutoshi Nihongi'sCollection (MN. 201), donated to and exhibitedat the City Hall of Sapporo, is possibly an
example of this species. It is cut longitudianally,
showing distant septa. It was obtained by M.
Nihongi from the Santonian of the Obira area.
Etymology:-Kamuy means god in the Ainus.
Family Cymatoceratidae Spath, 1927
(Remarks down to p. 89 by T. Matsumoto)
Nautiloids of the Cymatoceratidae are characterized by their own particular ribs which appear
in more or less late growth-stages. The ribs are
distinct on the outer surface of the shell but
weak or scarcely impressed on the internal mould.
As far as the available material is concerned, theearly immature shell of the cymatoceratids showa finely reticulate ornament just as those of
Nautilus, Kummeloceras and Eutrephoceras.
The sutures of Cymatoceras vary considerablyfrom a species to another. The type species,
Nautilus pseudoelegans d'Orbigny (1840, p. 70,

pI. 8, figs. 1-4; pI. 9, figs. 1, 2) (see also Kummel,
1956, pI. 16, figs. 1, 2; Miller and Harris , 1945 ,text-fig. 1), whose shell form is globose, hasgently sinuous sutures which are similar to thoseof Cenoceras or early Kummeloceras (e.g. K.
turcicum mentioned in Part I). The majority ofthe species of Cymatoceras shows somewhat
more sinuous sutures, which are essentially similar
to those of typical species of Kummeloceras.
Examples are C. atlas (Whiteaves) (1876, p. 17)[=N. elegans of d'Orbigny, 1840, p. 87, pI. 19,
figs. 1-4], C. saussureanum (Pictet) (1847, p.
273, pI. 1, figs. 3a-c), C. tourtiae (SchlUter)(1876, p. 170, pI. 46, figs. 1-4) (which has a
Procymatoceras-like subtrapezoidal outer whorl),
C. pseudoneganum (Spengler) (1910, p. 133,
pI. 12, figs. la, b; 7d), C. semilobatum (Spengler)(1910, p. 133, pI. 11, figs. 4a, b), C. patens(Kner) (see SchlUter, 1876, p. 178, pI. 50,
figs. 1-4), etc. The small dorsolateral saddle atthe umbilical shoulder becomes more distinct insuch species as C. cenomanense (SchlUter) (1876,
p. 168, pI. 45, figs. 1, 2). In this connexion I
should propose Eurocymatoceras gen. nov., designating Nautilus deslongchampianus d'Orbigny(1840, p. 90, pI. 20, figs. 1-4) [also Sharpe,
p. 12, pI. 3, figs. 1, 2; p. 15, pI. 5, fig. 3 underN. neocomiensis (non d'Orbigny)], from theCretaceous of Europe, as its type species. This
species has been assigned to Cymatoceras (seeKummel, 1956, p. 424), but is distinct in theshell form with angular umbilical shoulder, the_reticulate structure persisting to the shell of late
growth-stage and the presence of a small but
distinct saddle at about the umbilical shoulder.
Its suture is somewhat similar to that of C.
cenomanense and resembles more closely that ofAngulithes triangularis (Montfort) (see Kummel,
1956, pI. 26, figs. 1, 2).

Explanation of Plate 17
Fig. 1. Cymatoceras pseudoatlas (Yabe et Shimizu) . . . . . . . . . . . . . . . . . . . . . . .. Page 90
Hypotype from loco Ik1506r, lateral (a) and ventral (b) views, xO.6.

MATSUMOTO and MURAMOTO :Cretaceous Nautiloids II

Plate 17

762. Cretaceous Nautiloids

The almost linear suture as shown in C.
loeblichi Miller et Harris (1945, p. 6, pi. 2,
figs. 1-4; pI. 3, figs. 3, 4; text-fig. 2C) is exceptional for the genus and can be interpreted
as a reduced rather than a primitive original
character.
It should be noted that in the Cymatoceratidae
the folded sutural pattern like that of Nautilus
or Cimomia was developed already in the Jurassic
to Cretaceous genus Paracymatoceras Spath,
1927, which is represented by the type species
Nautilus asper (Oppel) Zittel, 1868 (p. 48, pi. 3,
fig. 1) (also Miller and Harris, 1945, p. 9, pI. 4,
figs. 1-3), N. texanus Shumard, 1860 (see Miller
and Harris, 1945, p. 10, pi. 3, figs. 1, 2; pI. 5,
figs. 1-3; text-figs. 3A, B) and P. tunghaicum
Matsumoto et Amano (1964, p. 175, pi. 26,
fig. 1; text-figs. 2, 3). Heminautilus Spath, 1927,
represented by the type species Nautilus saxbii
Morris (see Kummel, 1956, pI. 10, figs. 1, 2) andothers, has likewise folded sutures and is characterized by a trapezoidal whorl with more or lesssharpened ventrolateral shoulders.
Deltocymatoceras Spath, 1927, represented
by the type species Nautilus leiotropis Schli.iter(1876, p. 175, pl. 48, figs. 1,2), is characterized
by an Angulithes like subtrigonal whorl-shape,with a keel on the venter, and moderately
sinuous sutures with a small but distinct saddle
near the umbilical margin like those ofAngulithes
triangularis.
Procymatoceras Spath, 1927, with the typespecies Nautilus subtruncatus Morris et Lycett(1850, p. 10, pl. 1, fig. 2), from the Jurassic
Great Oolite of England, is characterized by athickly subtrapezoidal whorl-section and fineribbing. As is better shown in P. baberi (Morris
et Lycett) (1850, p. 10, pl. 1, fig. 1), anotherspecies from the Great Oolite, the suture is
weakly sinuous, resembling that of Cenoceras.
Cymatonautilus Spath, 1927, established on
Nautilus julii (Baugier MS) d'Orbigny, 1850
(see Kummel, 1956, p. 430, pl. 18, figs. 1-4),
from the Jurassic of Europe, is characterized bya subquadrate whorl-section and a ventral andalso lateral grooves. Its suture is similar to but
somewhat more sinuous than that of Cenoceras.

89

Eucymatoceras Spath, 1927, represented by
the type species Nautilus plicatus Fitton (seeKummel, 1956, pI. 21, figs. 1, 2), has a characteristic ribbing of multiple Vs. Its suture is also
gently sinuous.
Epicymatoceras Kummel, 1956, represented
by the type species Nau tilus vaelsensis Binckhorst,
1861 (p. 15, pl. 5c, fig. 2) (see also Schli.iter,
1876, p. 177, pl. 51, figs. 1, 2), from the Maastrichtian of Europe, is characterized by acompressed subrectangular whorl-section with aflattened venter and a compratively wider
umbilicus. Its suture is as moderately sinuous asthat of Kummeloceras but has a shallow ventral
lobe.
Anglonautilus Spath, 1927, represented by
the type species Nautilus undulatus Sowerby(see Kummel, 1956, pi. 26, figs. 1, 2) and several
others, has a subquadrate body-chamber andfold-like major ribs in the adolescent stage. The
suture of the type species is described as slightly
sinuous but there is a species from Hokkaido
which shows somewhat more sinuous sutures(see Part 4).
To sum up, Cymatoceras is interpreted tohave been derived from some Cenoceras directly
or by way of early Kummeloceras and haveoffshooted variously specialized genera of theCymatoceratidae. The somewhat sinuous sutural
pattern like that of Kummeloceras seems tohave been the fundamental framework in the
Cymatoceratidae and it may have been modified
to a slightly sinuous or almost linear sutural
pattern in some (but not many) species ofCymatoceras, kept with little or minor change
in Epicymatoceras, Eucymatoceras and Anglonautilus, which are specialized in shell-form
and ribbing respectively, and evolved to somewhat more sinuous pattern in Deltocymatoceras
and Eurocymatoceras and to still more sinuous,folded patterns in Paracymatoceras andHeminautilus. Deltocymatoceras of the Cymatoceratidae
is in parallel with Angulithes of the Nautilidae,
whereas Heminautilus shows another specialization in shell-form.
In some species of Paracymatoceras, Cymatoceras and Anglonautilus, a shallow median groove

90

Tatsuro MATSUMOTO and Kikuwo MURAMOTO

is developed on the venter of the body-chamber.
This is a character which must have been related
to a particular mode of life. The ventral grooveof Cymatonautilus is the most distinctive. Asidefrom this, a rather irregular groove may be seen
occasionally on the venter. This can be interpreted as a kind of injury.
Genus Cymatoceras Hyatt, 1884
Type species:-Nautilus pseudoelegans d'Orbigny, 1840.
Remarks:-The genus has been comprehensively redescribed by Kummel (1956, p. 418427), and some additional remarks are given
above. In addition to "C. " deslongchampsianum
mentioned above (under Eurocymatoceras nov.),
C. tskaltsithelensis (Rouchadze) (1931) from theAptian of Koutais (USSR), is peculiar in having
a folded sutural pattern (see Kummel, 1956,
text-fig. 24G) and a comparatively evolute
shell. A new generic or subgeneric name may
be required for it, but I would not propose iton this occasion.
Numerous species of Cymatoceras are mostly
from the Cretaceous in various regions of theworld. Kummel (1956, p. 426) listed an Upper
Jurassic species, C. perstriatus (Steuer), from
Argentina. I agree with Kummel in the assignment of Neocymatoceras tsukushiense Kobayashi(1954), from the Oligocene of Fukuoka (Kyushu),
to Cymatoceras. I should add "Entrephoceras"japonicum (Shimizu), from the Eocene of
Kyushu as another example of Cymatoceras who
survived from Cretaceous species. Shimizu's(1929, p. 25, pI. 8, figs. 1, 2) holotype is aninternal mould which show somewhat sinuous
sutures like those of Kummeloceras. The specimens subsequently described by Kobayashi and
Kamada (1959) (e.g., UMUT. CM 8497, CM

8498, CM 8500) have Cymatoceras type ribson the body-chamber, although the ribs are
weakened by erosion. It is interesting to see thata lew species of Cymatoceras occur in the Lower
Tertiary of Japan, representing the survival of thegenus.
In this connection I notice another possible
survivor from the Mesozoic nautiloid in Indonesia. That is Nautilus butonensis Martin (1933,
p. 30, pI. 5, figs. 34, 34a), from the Oligocene of
Buton island. It was referred to Eutrephoceras
by Kummel (1956, p. 381), but its shell shows
longitudinal lirae, especially distinctly on theouter surface of the shell. It resembles Cenocerasof the Jurassic period and could be either aderived fossil or a rare survivor.
Cymatoceras pseudoatlas (Yabe et Shimizu)

PI. 18, Fig. 1
1924. Nautilus (Cymatoceras) pseudo-atlas Yabeet Shimizu, Japan. Jour. Geol. Geogr., vol.
3, no. 2, p. 42, pI. 5.
1956. Cymatoceras pseudoatlas Yabe et Shimizu;
Kummel, Bull. Mus. Compo Zool. Harvard,
vol. 114, no. 7, p. 426.
Holotype:-A single specimen described by
Yabe and Shimizu (1924, indicated above),
IGPS. 8044, kept in the Palaeontological Collections, Tohoku University, Sendai. The type
locality is a point 1 km north of Himenoura in
Amakusa, Kumamoto Prefecture (western central
Kyushu). It was collected by the late Dr. T.
Nagao. The locality is assigned to the Santonianpart of the Himenoura Group (Ueda, 1962).
Material: -MC. Ik-1506r, probably an adultshell as large as the holotype; a still larger specimen in Satoru Yamaguchi's Collection, now
displayed at the Museum of Mikasa (54719-2);

Explanation of Plate 18
Fig.1. Cymatoceras pacificum sp. nov. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Page 92
Holotype, Me. TS-3025, two lateral (a, b) views, xl.

91762. Cretaceous Nautiloids
GK. H5919, smaller, probably inner whorl.
Description:-The adult shell, represented by
the holotype and MC. Ik 1506r, is fairly large,
with a diameter over 200 mm. Another incompletely preserved specimen (S. Yamaguchi CoIl.)
is still larger, about 250 mm in diameter under adistorted condition.
The living chamber occupies about two thirdsof the last whorl, as seen in MC. Ik 1506r, which
has the last septum at about the diameter of 150mm.
The whorl enlarges fairly "rapidly" (i.e., witha fairly large rate). It is subrounded reniform in
section, a little broader than high in the adultstage, with the maximum breadth in the lower
part at two fifths of the whorl-height. The venteris semicircular in the late stage but more narrowly arched in earlier stages. The umbilicus isvery narrow, seemingly closed when it is coveredby callus, as seen on the right side of MC. Ik
1506r (and on the holotype), but measured atabout 7 per cent of the entire shell diameter,
as seen on the left side of the same specimen(MC. Ik 1506r). It is deep and surrounded by asomewhat overhanging wall and a roundedshoulder.
The surface of the shell on the outer whorl
is marked by numerous ribs of Cymatoceras
type. They are dense, about 25 within the
distance along the mid-venter as long as thewhorl-height. Bifurcation of the ribs takes placeat various distances from the umbilicus. It occurs
more frequently on the lower part of the flank
more or less near the umbilicus but sometimes
seen on the ventrolateral part or even on theventer.

Table 2.
SpecimenOn the well preserved part fine lirae run on
the ribs in parallel to the latter. The ribs areslightly prorsiradiate on the inner (Le. lower)part of the flank and gradually curved backward
on the ventrolateral part, crossing the venter witha moderate backward curvature. On the venter inthe last part of the adult body-chamber, the rib
is about 5 mm in breadth, whereas the interspace(or furrow between the ribs) is much narrower,
about 1.0 to 1.5 mm in breadth.
The surface of the imm'ature shell on the inner
whorl, as represented by GK. H5919, shows afine lattice ornament which consists of radial andspiral lirae in combination. The curvature of theradial lirae is similar to that of the ribs on theouter whorl.
The septa are fairly frequent. The suture has
a shallow and broad lateral lobe on the flank anda low and small saddle at the umbilical shoulder,showing a sinuosity. The siphuncle is not observable in MC. Ik 1506r. It is described to be subventral in the holotype.
Comparison:-We agree with Yabe and Shimizu(1924) in separating this species from C. atlas(Whiteaves) (1876, p. 17) [= Nautilus elegansof d'Orbigny, 1840, pI. 19, figs. 1--4] (non J.
Sowerby). The ribs are bifurcated not only near
the umbilical margin but also on the flanks andon the venter in the former, whereas they are
not bifurcated on the outer part of the whorl
in the latter. We notice, however, that the two
species are closely allied to each other in viewof the resemblance in shell-form, density andfineness of the ribs, rib curvature, frequency
and sinuosity of the sutures and position of
the siphuncle. It can be possibly presumed that

Measurements (in mm), Cymatoceras pseudoatlas

Diameter

Holotype (Y. & S.)

211

MC. Ik 1506r

215

GK. H5919

38.2

Umbilicus

16 (?) (.07)

BreadthB/H

157 (.74)

165 (.76)*[.78]

1.05

130 (.60)

138 (.64)

1.06

24.2 (.63)

29.2 (.76)

1.20

Height* There is discrepancy between the absolute value and the percentage in the measurements ofYabe and ShimiZU (1924).

91762. Cretaceous Nautiloids
GK. H5919, smaller, probably inner whorl.
Description:-The adult shell, represented by
the holotype and MC. Ik 1506r, is fairly large,
with a diameter over 200 mm. Another incompletely preserved specimen (S. Yamaguchi CoIl.)
is still larger, about 250 mm in diameter under adistorted condition.
The living chamber occupies about two thirdsof the last whorl, as seen in MC. Ik 1506r, which
has the last septum at about the diameter of 150mm.
The whorl enlarges fairly "rapidly" (Le., witha fairly large rate). It is subrounded reniform in
section, a little broader than high in the adultstage, with the maximum breadth in the lower
part at two fifths of the whorl-height. The venteris semicircular in the late stage but more narrowly arched in earlier stages. The umbilicus isvery narrow, seemingly closed when it is coveredby callus, as seen on the right side of MC. Ik
1506r (and on the holotype), but measured atabout 7 per cent of the entire shell diameter,
as seen on the left side of the same specimen(MC. Ik 1506r). It is deep and surrounded by asomewhat overhanging wall and a roundedshoulder.
The surface of the shell on the outer whorl
is marked by numerous ribs of Cymatoceras
type. They are dense, about 25 within the
distance along the mid-venter as long as thewhorl-height. Bifurcation of the ribs takes placeat various distances from the umbilicus. It occurs
more frequently on the lower part of the flank
more or less near the umbilicus but sometimes
seen on the ventrolateral part or even on theventer.

Table 2.

Measurements (in mm). Cymatoceras pseudoatlas

Specimen

Diameter

Holotype (Y. & S.)

211

MC. Ik 1506r

215

GK. H5919

On the well preserved part fine lirae run on
the ribs in parallel to the latter. The ribs areslightly prorsiradiate on the inner (Le. lower)part of the flank and gradually curved backward
on the ventrolateral part, crossing the venter witha moderate backward curvature. On the venter inthe last part of the adult body-chamber, the rib
is about 5 mm in breadth, whereas the interspace(or furrow between the ribs) is much narrower,
about 1.0 to 1.5 mm in breadth.
The surface of the immature shell on the inner
whorl, as represented by GK. H5919, shows afine lattice ornament which consists of radial andspiral lirae in combination. The curvature of theradial lirae is similar to that of the ribs on theouter whorl.
The septa are fairly frequent. The suture has
a shallow and broad lateral lobe on the flank anda low and small saddle at the umbilical shoulder,showing a sinuosity. The siphuncle is not observable in MC. Ik 1506r. It is described to be subventral in the holotype.
Comparison:-We agree with Yabe and Shimizu(1924) in separating this species from C. atlas(Whiteaves) (1876, p. 17) [= Nautilus elegansof d'Orbigny, 1840, pI. 19, figs. 1-4] (non J.
Sowerby). The ribs are bifurcated not only near
the umbilical margin but also on the flanks andon the venter in the former, whereas they are
not bifurcated on the outer part of the whorl
in the latter. We notice, however, that the two
species are closely allied to each other in viewof the resemblance in shell-form, density andfineness of the ribs, rib curvature, frequency
and sinuosity of the sutures and position of
the siphuncle. It can be possibly presumed that

38.2

Umbilicus
16 (?) (.07)

HeightBreadthB/H

157 (.74)

165 (.76)*[.78]

1.05

130 (.60)

138 (.64)

1.06

24.2 (.63)

29.2 (.76)

1.20* There is discrepancy between the absolute value and the percentage in the measurements ofYabe and Shimizu (1924).

92

Tatsuro MATSUMOTO and Kikuwo MURAMOTO

C. pseudoatlas may have been derived from C.
atlas, acquiring multiple bifurcation of the ribs.
Occurrence:-MC. Ik1506r was obtained by
Mr. Tatsuo Muramoto with Matsumoto's fieldwork. It was from the mudstone of loco Ik1506r(indicated by a solid circle to the right of letter
Ia at the left center of text-fig. 4 in Matsumoto
et al., 1981) which was exposed when the roadon the left side of the River Ikushumbets wasunder construction. The mudstone contains
Inoceramus (Platyceramus) amakusensis Nagao
et Matsumoto and Anapachydiscus deccanensis
yezoensis Matsumoto, among others. It is referred to the Zone of Inoceramus amakusensis, approximately Lower Santonian in terms of
the international scale.
GK. H5919 was obtained by Mr. Ohmi, a
student of Mikasa High School in 1955, at theconfluence of the Yoshiyachi-zawa with the mainstream of the Ikushumbets. This is again in
the Zone of Inoceramus amakusensis.
Cymatoceras pacificum sp. nov.
PI 18, Fig.1;PI. 19, Fig.1;PI. 20,
Figs. 1, 2; Text-fig. 3

Material:-Holotype, MC. TS-3025, probably
adult specimen, in which shell layers are preserved on the body-chamber but the visible partof the phragmocone is devoid of the outer shelllayer or partly the internal mould. Paratype,
MC. TS-3010, smaller, probably immatureshell. There is another paratype, GK. H5918 ofmoderate size, collected by S. Nagaoka over
40 years ago from South Sakhalin.
Description:-The holotype is about 130 mm
in diameter at the preserved end. The preserved
body-chamber is slightly less than a half whorl,
about 160°.
The whorl is broadly rounded in section,with a well rounded venter and inflated flanks.

It is broader than high, broadest somewhat

below the middle of the whorl-height, withthe proportion of B/H about 1.2 to 1.3. The
umbilicus is narrow, about 9 per cent of theentire shell diameter in the adult holotype andGK. H5918, but almost closed in the smaller
paratype. The umbilical shoulder is rather
abruptly rounded.
On the late· part of the phragmocone andthe body-chamber there are numerous ribs ofCymatoceras type, which are scarecely impressed on the internal mould. Shorter ribs are
sometimes branched or intercalated at about
the umbilical shoulder, on the flank and at
about the ventrolateral shoulder. As a result
the ribs number about 10 to 12 in a distanceon the median part of the venter as long as
the whorl-height. They can be described asfairly coarse or of moderate density comparedwith the cases in other species of Cymatoceras.
On the well preserved part the ribs and theinterspaces are covered with fine lirae which
are nearly parallel to the ribs. They are somewhat
prorsiradiate on the main part of the flank andcurved backward at about the ventrolateralshoulder, forming a moderate backward curvature on crossing the venter.
The immature shell shows at first a characteristic lattice ornament by the combination ofradial and spiral lirae and then, at the diameterof about 30 mm, weak radial ribs begin to appear
at first on the inner half of the flank and thenwholly. In GK. H5918 the Cymatoceras type
band like ribs separated by groove-like narrowinterspaces begin to appear at the diameter ofabout 50 mm, i.e. at about the last quarter ofthe phragmocone.
The suture, which is well exposed on theholotype (Text-fig. 3) and on a part of GK.
H5918, shows some sinuosity. The ventral lobe

Explanation of Plate 19
Fig. 1. Cymatoceras pacificum sp. nov. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Page 92
Holotype, Me. TS-3025, ventral (a) and frontal (b) views, xl.

i::1
{l

]

:;::
;:!
t:j

~

'"

;:!

0
~
<.>

.s
~

II

aE-<
a

~
'<1!

§
~
"lj
~
<:l

~

a

~
~

~

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""""

762. Cretaceous Nautiloidsl'Text-fig. 3. Cymatoceras pacificum sp. nov.
The last 5th external suture of holotype, MC.
TS-3025, at whorl-height = 45 mm. Bar = 10mm.
(T. Matsumoto delin.)

is very broad and shallow or almost negligible;
the lateral lobe is distinct but broad, passing
to an indistinct saddle at the umbilical shoulder.
The septa are fairly close-set, numbering about
10 per half whorl.
The position of the siphuncle is not observable in the holotype. It is clearly shown in GK.
H5918 at some distance below the midst of
the dorso-ventral median-line. The same is forthe smaller paratype, though indistinctly shown.
Remarks:-In GK. H5918 the body-chamberis preserved only for about 90°. Should it bepreserved completely for about 160°, then its
diameter would be about 90 mm. This is, however, still smaller than the holotype. The specimen may represent a shell of middle-growth
age or an unusually small adult shell.
Comparison:-1fhe present species resembles
Cymatoceras saussureanum (Pictet) (1847, p.
273, pI: 1, figs. 3a-c), from the Albian of Europe,with respect to the rounded whorl, rather coarse
ribs, mode of bifurcation or intercalation ofshorter ribs and fairly close-set sinuous sutures.
Especially GK. H5918 resembles closely theillustrated type of Pictet. Our species, however,93

has a somewhat broader whorl, with B/H 1.21
(to.05) as compared with 1.14 in the latter,slightly more numerous ribs in the corresponding
part (10 as compared with 8 in the latter within
the distance on the venter as long as the whorlheight) and less pronounced saddle at the umbilical shoulder than the latter. A still clearer
distinction is in the siphuncle position: somewhat dorsad of the center in the present species
and somewhat ventrad of the center in thatspecies (the center means the midst of thedorso-ventral median line of the whorl-section).
The holotype of the present species is somewhat similar to that of Cymatoceras atlas(Whiteaves) (1876, p. 17) [= Nautilus elegansof d'Orbigny, 1840, pI. 19, figs. 1-4] (non J.
Sowerby), from the Cenomanian of France, inthe general aspects of the shell arid the sutural
pattern and frequency, but the former has morerounded whorl and less numerous, somewhat
coarser ribs, which show some intercalation orbifurcation. So far as d'Orbigny's illustrationis concerned, there occurs no bifurcation orintercalation of the ribs on the outer half of
the whorl, although it can be seen near theumbilical shoulder. The umbilicus is closed andthe siphuncle is more ventrad in C. atlas.
For the same reasons, Nautilus eiegans of
Sharpe (1853, p. 12, pI. 3, fig. 3; pI. 4, fig. 1),
from the Cenomanian of England, is betterreferred to C. atlas, as Wright and Wright (1951,
p. 11) have already pointed out.
The present species resembles C. sharpei(Schliiter) (1876, p. 171, pI. 46, figs. 5-7),
from the Lower Cenomanian [Tourtia] of West
Germany, with respect to the outline of whorl-

Table 3. Measurements (in mm), Cymatoceras pacificum sp. nov.
Specimen

DiameterUmbilicus

HeightBreadthB/H

Holotype (end)Holotype (-90°)
Holotype (last sept.)
Paratype 1
GK. H5918

130.0 (1)107.0(1)90.0 (1)44.0 (1)63.0 (1)12.0 (;09) 80.0 (.62) 97.0 (.75)
10.0 (.09) 62.0 (.58) 78.0 (.73)
7.8(.09) 53.0 (.59) 64.0 (.71)
28.0 (.64) 33.0 (.75)
6.2 (.10) 35.0 (.55) -44.0 (.70)

1.21
1.26
1.21
1.19
1.26

94

Tatsuro MATSUMOTO and Kikuwo MURAMOTO

section and the position of siphuncle, but thelatter has a still narrower (almost closed) umbilicus and more distant sutures (8 per half
whorl), which show shallower, less distinct
lateral lobe but a more pronounced saddle atthe umbilical shoulder.
The present species is similar to C. madagascarense (Yabe et Shimizu, 1924) [= N. eiegansof Boule et ai., 1907, p. 66, pI. 15, figs. 4,5],
from the Senonian of Madagascar, in the shellform and mode of ribbing, but the siphuncle ishighly ventrad in the latter.
C. pacificum is distinguished from C. pseudoatlas in its broader whorl, coarser ribs andrather dorsad instead of ventrad siphuncle.
Occurrence :-The holotype was obtained ata point on the stream of the Wakkawembets,
in a place now called Yamato, upper reachesof the Abeshinai, a tributary to the River Teshio,
northwestern Hokkaido (see Matsumoto, 1942,
pI. 10 for the geological map of the area). It is
associated with Sphenoceramus schmidti Michael
and Tetragonites popetensis Yabe, being evidently referable to the Zone of Sphenoceramus
schmidti, substage K6a2 in the Japanese province, approximately Middle Campanian interms of the international scale. The smaller
paratype (MC-TS3010) was also from the Wakkawembets, close to the type locality. GK.
H5918 has no precise record of occurrence
but probably from the Upper Cretaceous of
the "Kawakami Colliery", south of the Naibuchi.
The lithology of the rock matrix, dark grey
siltstone, containing several immature shellsof Sphenoceramus, suggests its derivation from
Zone Mh7 (uppermost part of the Miho Group),i.e. the Zone of Sphenoceramus orientalis, aproximately Lower Campanian in terms of theinternational scale.

References Cited(For brevity the references listed at theend of Part 1 are not repeated here.)
Binckhorst, J. T. (1861): Monographie desgasteropodes et des cephalopodes de lacraie superieure de Limbourg. Bruxelles et
Maastricht, p. 1-83, pis. 1-6; p. 1-44,
pis. 5b-d, 7, 8, 8a, 9 (reprinted in 1873).
Boule, M., Lemoine, P. and Thevenin, A. (19061907): Pallflontologie de Madagascar, III Cephalopodes cretaces des environs deDiego-Suarez. Ann. Paleont., vol. 1, p. 173192, pis. 14-20 (1906); vol. 2, p. 1-56,
pis. 1-8 (1907).
Hauer, F. von (1858): Uber die Cephalopoden
der Gosauschichten. Beitr. Palaeontogr.
Osterr., vol. 1, no. 1, p. 7-14, pIs. 1-3.
Kobayashi, T. (1954): A new cymatoceratid
from the Palaeogene of northern Kyushu
in Japan. Japan. Jour. Geol. Geogr., vol. 24,
p. 15-21, pis. 4,5.
Kobayashi, T. and Kamada, Y. (1959): An
Eocene nautiloid from Kyushu, Japan.
Japan. Jour. Geol. Geogr., vol. 30, p. 105114, pI. 9.
Martin, K. (1933): Eine neue Tertiiire Molluskenfauna aus dem Indischen Archipel. Leidsche
Geol. Meded., vol. 6, pt. 1, p. 7-32, pIs.
1-5.
Matsumoto, T. (1942): Fundamentals in the
Cretaceous stratigraphy of Japan. Part 1.
Mem. Fac. Sci., Kyushu Imp. Univ., ser.
D, vol. 1, no. 3, p. 129-280, pis. 1-20.
Matsumoto, T., Kanie, Y. and Yoshida, S. (1979):
Note on Pachydiscus from Hokkaido. Mem.
Fac. Sci., Kyushu Univ., ser. d, vol. 24, no. 2,
p. 47-73, pis. 8-13.
Matsumoto, T., Muramoto, K., Hirano, H. andTakahashi, T. (1981): Some Coniacianammonites from Hokkaido. Trans. Proc.

Explanation of Plate 20
Figs. 1, 2. Cymatoceras pacificum sp. nov. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Page 92
1. Paratype, MC. TS-3010, two lateral (a, b), frontal (c) and ventral (d) views, xl.
2. Paratype, GK. H5918, right lateral (a) and. ventral (b) views and natural longitudinal
section of outer whorl with left lateral view of inner whorl (c), xl.

MATSUMOTO and MURAMOTO:

Cretaceous Nautiloids II

Plate 20

2b

1a

1b

95

762. Cretaceous Nautiloids
Palaeont. Soc. Japan, n.s., no. 121, p. 5173, pIs. 6-8.
,
Miller, A. K. and Harris, R. A. (1945): North
American Cymatoceratidae (Mesozoic Nautiloidea). Jour. Paleont., vol. 19, p. 1-13,
pIs. 1-6.
Morris, J. and Lycett, L. (1850): A monographof the Mollusca from the Great Oolite,
chiefly from Minchinhampton and the coastof Yorkshire. Palaeontogr. Soc. (London),
4 parts, viii + 130 + 147 + 129 p., 45 pIs.
Pictet, F. J. (1847) in Pictet, F. J. and Roux, W.
(1847-1853): Description des mollusquesfossiles qui se trouvent dans les Gres Vertsdes environs de Geneve. Mem. Soc. Phys.
Hist. Nat., Geneve, vol. 11, no. 2 (1847),
p. 257-412; vol. 12 (1849), p. 157-287;
vol. 13, no. 1 (1853), p. 73-173;489-558,
pIs. 1-51.
Redtenbacher, A. (1873): Die Cephalopoden
fauna der Gosauschichten in den nordostlichen Alpen. Abhandl. Geol. Reichsanst.,
vol. 5, p. 91-140, pIs. 22-30.
Reeside, J. B. Jr. (1924): A new nautiloid
cephalopod, Eutrephoceras sloani, from the
Eocene of South Carolina. U. S. Nat. Mus.
Proc., vol. 65, art. 5, p. 1-4, pIs. 1-3.
Rouchadze, J. (1931): Notice sur les Belemnites
et les Nautilus de l'Aptien de Koutais. Bull.
Mus. Georgie, vol. 6 (1929-1930), p. 125138, pIs. 1-3.
Shimizu, S. (1926): On two species of Nautiloi-

dea from the Tertiary of Japan. Sci. Rept.
Tohoku Imp. Univ., ser. 2, vol. 9, p. 25-27,
pI. 8.
Shumard, B. F. (1860): Descriptions of new
Cretaceous fossiIs from Texas. St. Louis
Acad. Sci. Trans., vol. 1, p. 590-610 (inaccessible here).
Ueda, Y. (1962): The type Himenoura Group.
Mem. Fac. Sci. Kyushu Univ., ser. D, vol.
12, no. 2, p. 129-178, pIs. 22-27.
Ueda, Y., Matsumoto, T. and Akatsu, K. (1962):
The Cretaceous deposits in the Chikubetsu
area, Hokkaido. Sci. Rep. Dept. Geol.
Kyushu Univ., vol. 6, no. 1, p. 15-32 (inJapanese with English abstract).
Wright, C. W. and Wright, E. V. (1951): A surveyof the fossil Cephalopoda of the Chalk ofGreat Britain. Primarily a nomenclatorial
revision of Daniel Sharpe's "Descriptionof the fossil remains of mollusca found in
the Chalk of England, Part I. Cephalopoda"(1853-1857). Palaeontogr. Soc., London(1950), p. 1-40.
Zittel, K. A. von (1868): PalaeontologischeStudien fiber die Gremzschichten der Juraund Kreide-Formation im Gebiete der
Karpathen, Alpen und Apenninen, I. Abtheilung, Die Cephalopoden der Stramberger
Schichten. Mus. K. Bayer. Staates Palaeont.
Mittl. (begonnen von Oppel, forgesetzt vonZittel), vol. 2, p. 33-118, pIs. 1-24 in
an atlas.

Abeshinai (7 ~ -/:T 1 =:t(.:iJZitpg), Amakusa C:R.1fi) , Deto-futamata (7' r .:::1llt), Haboro C;j;J~)
Himenoura (/IJ:!im) , Hobetsu (~}JIJ), Ikushumbets (~~}JIJ), Inasato (ffflillJ, Kawakami OllJ:)
Kumamoto (Jm*) , Miho (~f*), Mikasa C=~), Naibuchi (pgiJllD, Obira (/PiL), Pisshiri-zawa(I::." '" -/ !! rR), Sanushi ({£±) , Sanushibe (-If":;t -/~), Sapporo (;fL~.lil), Teshio (xl;\!) , Urakawa(rrllfoJ) , Wakkawembets ('7", 7J?;r. ;/~:;t), Yamato Cj(fll), Yoshiyachi-zawa (3 -/i'-rrR)~tlfljill~B!IUc*? A 7f 1 ~- JI. .:to) 2 c L. -C,~tlli.imO) -If";/ r .::. 7;/ C ;I];/ .. ~ =- 7 ;/(-mn iI-l?.i!iK L.t.: 3 ffra-Ilcltt • IZI~ L.t':o 3;fil!0)? '1;,0) 11;J:}J'II~10)rllll~)-;/ r =- 7 ;/g[0) tcO)-cf-t*~.h, Eutrephoceras sublaevigatum Cd'Orbigny) I:' {.);.l7.J iI~, *~8-~iJ; t.., ilIi;[k-C Kummeloceras (.:to) 1 -C~lL) 0) H'fr;fil!c L.t.:. 2 jH~ 1t.~{f:}]1j0)-H11~)-;/ I, .::. 7 ;/g[0)XI} 211P1>-C t\':~ ~.h, vt*:fLmx1fi 0) /lJ:!rm~tWO) r{ffl-lf";/ r .::. 7;/ ii-I? ¥fl-lfi?.h -C~ ,t.:Cymatoceras pseudoatlas CYabe et Shimizu) t:.liiJ)E ~.h7.Jo 311J: 9 It. x~7 ~ -/:T 1 O)<=P{ffl7J ;/ .. {.::. 7 ;/g[O)X/J' 211P1>c, 1rO)m~* (J11J:O)rfffl 7J ;/ .. { =- 7 ;/?) ii-I? l*1&~.h-C~ ,t.:'*'{fto)X~ ~ 0) t O)-Ct\':~~.h, Cymatoceras O)lifrfll! c L.t.:o ;: .hIt. C. saussur~anum(pictet) I:' {.);.l7.J iI~, -If"1 77 ;/? Ivil'~~!J!I~Uf:.ti4mt-t 7.J ;: c t.c c-CIK}Jlj ~.h7.Jo t.c:totl~Jtt:j.:l(t'.i:*.lji'i') -C, Cymatoceratidae lkrY- Cymatoceras I:."?~~~i!ll L., llifrA~a-tJl!PQ L.
t'.i:*~Jl~ • t1*l'if~~t.::.o0)-$Trans. Proc. Palaeont. Soc. Japan, N. S., No. 130, pp. 96-116, pI. 21-27, July 15,1983

763. MIDDLE PALAEOZOIC PALAEOSCENIDIIDAE(RADIOLARIA) FROM MT. YOKOKURA, SHIKOKU,
JAPAN. PART IHIROSHI FURUTANIDepartment of Earth Sciences, Nagoya University, Chikusa, Nagoya 464

Abstract. Palaeoscenidiidae have most basically a bar-centered, eight-spined
and polarized spicule. The eight spines consist of four shorter apical spines and four
longer basal spines, although the apicals may be reduced to as few as one. It is
widely recognized in many species of palaeoscenidiids that one of the apical spines
is distinctively developed. Each spine is distinguished by comparative location withthe distinctive apical spine and the median bar. Skeletal construction and systematics of palaeoscenidiids are easily understandable in terms of these identifications.
Palaeoscenidiidae are composed of Palaeoscenidiinae and Pentactinocarpinae.
Palaeoscenidiinae contain the following genera; Palaeoscenidium, Archaeosemantis,
Parentactinia, Pactarentinia n. gen. and Tlecerina n. gen., and probably Sepsagon
and Parasepsagon.
Five new and two indeterminable species of Palaeoscenidium?, Parentactinia,
Pactarentinia and Tlecerina are described. Genera of Parentactinia, Pactarentinia
and Tlecerina may be simply termed a lattice-shelled Palaeoscenidium. They are
distinguished by degree of development of the shell. Each shell is situated underthe basal spines in Parentactinia, covers a part of each basal spine';'n Pactarentinia,
and involves the whole of the spicule in Tlecerina.
These radiolarians were obtained from a specimen of siliceous shale in the
middle part of the G 4 of Mt. Yokokura. The geological age of it is estimated earlyor middle Devonian on the basis of the stratigraphic relationship between the G 4
and associated fossil-bearing formations and comparisons with known Palaeozoic
radiolarians.

unit! recently. The systematic position of thisfamily at suborder rank had remain,:d as incertae
sedis. Holdsworth (1977) somewhat emended
it and supposed that it might relate to Haplentactinia, and he tentatively assigned it to the superfamily Entactiniacea, the suborder Spumellaria.
Moreover, he found Silurian occurrence from
Cornwallis Islands, Arctic Canada. Dumitricl{(1978) proposed the subfamily Pentactinocarpinae, which contain five genera, four of them
are new, on the basis of the material obtained
from Middle Triassic rocks of Italy and Romania.
Recently occurrence of middle or late Ordovician

Introduction
The family Palaeoscenidiidae was establishedby Riedel (1967) on the basis of the genus
Palileoscenidium Deflandre, 1953 as a spicularform consisting of two to four apical spines andfour basal spines proximally connected by flat
lamellae. Palaeoscenidium was the only component of the family at first. It had been known
only from the Lower Carboniferous of France(Deflandre, 1953) and Turkey (Holdsworth,1973), and the Upper Devonian of Ohio (Foreman, 1963) and Kazakhstan (Nazarov, 1975)96

763. Middle Palaeozoic Palaeoscenidiidae (Radiolaria)

97

comparison with previously known radiolarians.
Evolution of this family are briefly remarked
also. Other assemblages will be described innear future.
The sample was mainly dissolved for 24 to
30 hours in HF and HC1 diluted 1 part HF (45%)
and the same volume of HC1 (36%) to 8 or 7 partsof waters. Subsequently the residues were sieved
with a piece of bolting cloth of mesh opening
6011, and cleaned by boiling in diluted H2 0 2 •Acknowledgemen ts

Text-fig. !. Location of Y-19(X). Base map
is the 1 :25,000 "Osaki" topographical map
issued by the Geographical Survey Institute.
Palaeoscenidium was reported by Igo et al.
(1980) with no illustrations, although the age remains uncertain as pointed out by me (Furutani,1981).
In the summer of 1980, I discovered fairly
well-preserved radiolarian assemblages in siliceous
shale of the G4 Formation in the Gionyama
Group exposed on the southern slope of Mt.
Yokokura (=Yokokurayama), Ochi-cho, Kochi
Prefecture, Shikoku, Japan (Text-fig. 1). Oneof them which is named Tlecerina horrida
assemblage consists of Palaeoscenidium? sp. A,
Parentactinia vetustum n. sp., Pactarentinia
holdsworthi n. gen. n. sp., Tlecerina horrida n.
gen. n. sp., T . exilis n. gen. n. sp., T. fenestrata
n. gen. n. sp. and T. sp. A with minor elements
such as Haplentactinia (s. I. ) sp., Ceratoikiscum
sp ., some other forms of palaeoscenidiids andindeterminable spumellarians. Above-mentioned
major species extracted from a rock sample no.
Y-19 are described herein and the constructionof the skeletons of them are fully examined.
Extent of the Palaeoscenidiidae is discussed in

I am much indebted to Dr. Paulian Dumitrica
of Institutul de geologie ~i geofizica, Romania,
Dr. Brian K. Holdsworth of the University of
Keele, England and Dr. Kojiro Nakaseko of
Osaka University for critical reading of the typescript of this paper and giving me valuable suggestions. I am grateful to Prof. Akira Morishita
and Dr. Junji Itoigawa of Nagoya University
for kind reviewing an early typescript andhelpful suggestions. I wish to thank Dr. Shigenori
Maruyama of Toyama University for persuading
me to study the radiolarians of Mt. Yokokura
and assistance in field work. Thanks are also due
to Mr. Atsushi Takemura of Kyoto University
for giving me valuable discussion, and to Mr.
Hiroaki Ishiga of Osaka City University forthe information on the Permian palaeoscenidiid.
Geologic setting and age
Hamada (1961) gave a general name "Gionyama Series" to Middle palaeozoic rocks scattered in the Kurosegawa Tectonic Zone, Outerzone of Southwest Japan. He divided the series
into four stages in ascending order; G 1 (thickness
is unknown) tuffaceous sandstone, G2 (25m+)
fossiliferous limestone, calcareous sandstone andso on, early-middle Wenlockian in age, G 3(240m) fossiliferous limestone , early Ludlovian,G4 (llOOm) acid volcanic rocks with occasional
occurrence of radiolarian remains, and subordinate amounts of tuffaceous sandstone and conglomerate, late Ludlovian to ?middle Devonian.
Mt. Yokokura is one of the best locality of the

98

Hiroshi FURUTANI

series cropping out. Afterward Hirata (1966a)
discovered late Devonian plant remains andbrachiopods including Leptophloeum rhombicum
Dawson, Lepidodendropsis sp. and Orbiculoidea
sp. from the overlying pelitic rocks named the
Ohira Formation by him. Subsequently thename of the formation was revised to the Ochi
Formation by the same author (1966b), who
considered the Ochi Formation occupies theupper part of the G4 • However according to
Yoshikura (1982) it is incorrect. According toHamada (1961) the G 4 conformably overlies
the G 3 , whereas exact stratigraphic relationshipbetween the G 4 and the Ochi Formation isin determined. Although no reliable index fossils
occur from the G 4 , the geological age of it canbe estimated between late Ludlovian and middle
Devonian times by its stratigraphic relationshipwith the G 4 and the Ochi Formation. The
present material was collected from roughly
middle part of the G 4 • Therefore, it is presumed
to be early or middle Devonian in age.
In general, determination of geological age of
Palaeozoic rocks only by radiolarians is· very
difficult, because our knowledge of biostratigraphy about Palaeozoic radiolarians is very
poor. It is only possible to estimate period, atthe best, especially before the Late Devonian.
In this case co-occurrence of conodonts is expected as a time indicator. However, they havenever been detected until the present. The
Tlecerina horrida assemblage described herein
is quite unique among known Palaeozoic assemblages. Therefore, it is impossible to assume theage of this assemblage by itself. However anotherslightly older assemblage, which consists of
Palaeoscenidium spp., Parentactinia sp., Haplentactinia (s. I.) sp., Ceratoikiscum spp. and unnamed spumellarians, may somewhat relate to
known Devonian radiolarians (Hinde, 1899;
Foreman, 1963; Nazarov, 1975) in general
aspect except the occurrence of Parentactinia.
Radiolarians of after Middle Devonian time arecomparatively well known than older fauna.
The complete absence of albaillellids in theseassemblages excludes possibility of Carboniferous
and Permian ages. Previously known Ordovician(Fortey and Holdsworth, 1972; Nazarov, 1975;
Nazarov and Popov, 1980; Igo et al., 1980) andSilurian (Holdsworth, 1977; Furutani, 1981)
radiolarians are far apart from these assemblages.
Thus the geological age of the Tlecerina horrida
assemblage is assumed to be Devonian. This is
not contradictory with the preceding estimationfrom the stratigraphy.
Construction of the skeletons
Palaeoscenidiidae are characterized by a polarized, five- to eight-spined and bar- or pointcentered spicule. Amongst those variations of
the spicule the eight-spined and bar-centered
one is regarded as the most fundamental type.
It consists of a short median bar and eight spines;
a pair of shorter apical spines and a pair of longer
basal spines radiate from each end of the medianbar. The basal spines usually have spinules.
Imperforate lamellae may connect with themedian bar and proximal parts of the basal
spines, thus forming the "tent-like shell" ofHoldsworth (1977). When the tent-like shelldevelops the median bar is not recognized asa distinct bar. The skeleton of the genus Palaeoscenidium Deflandre (Text-fig. 2a) consistsof the six- to eight-spined spiCUle and usually
the tent-like shell. When the spicule has eightspines, it is widely recognized in many speciesof Palaeoscenidium from the Ordovician (PI. 21,
Fig. 6) and Silurian of Fukuji, Central Japan,
in addition to the species of Mt. Yokokura, that
one of the four apical spines is distinctively
longer and thicker than the others. For convenience of descriptions I term the distinctive
apical spine principal apical spine (PA spine inabbreviation). Each spine is discriminated bycomparative situation with the PA spine andthe median bar. Other apical spines are also
termed as follows (PI. 21, Fig. 1);
counter apical apine: an apical spine situatedopposed to the P A spine (CA spine in
ab brevia tion)
lateral apical spine: an apical spine paired with
the P A spine (LA spine in abbreviation)
counter lateral apical spine: an apical spine

763. Middle Palaeozoic Palaeoscenidiidae (Radiolaria)

a

c

b

d

Text-fig. 2. Schematic profiles of genera of
Palaeoscenidiidae from Mt. Yokokura viewing
from the lateral side of the median bar.
a, Palaeoscenidium; b, Parentactinia; c, Pactarentinia; d, Tlecerina.
paired with the CA spine (CLA spine inabbreviation).
The basal spines are termed as follows;
PB spine: a basal spine underlying to the PA
spine
CB spine: a basal spine underlying to the CAspine
LB spine: a basal spine underlying to the LA
spine
CLB spine: a basal spine underlying to the CLA
spine
The number of the apical spines is essentially
four, but it may be redu\!ed to three or even
two. Holdsworth (1977) reported Siluria.n
Palaeoscenidium having two or three apicalspines from Cornwallis Islands, Arctic Canada.
In my collection almost all specimens of Palaeo-

99

scenidium have four apical spines. However,some specimens seem to have only two oreven one apical spine at a glance. When thenumber of apicals seems to be two, it is owing
to the minute LA and CLA spines. In the lattercase it is due to the minute CA, LA and CLA
spines. Foreman (1963) found two specimensof cf. Palaeoscenidium cladophorum having
only three basal spines, and Holdsworth (1977)
stated the number of the basals was three orfour in his specimens from Cornwallis. The
number of the basal spines, however, is invariably
four in my specimens obtained from Mt. Yokokura and Fukuji. I suppose Palaeoscenidium
originally had four basal spines, and such forms
having three basals are freaks or specialized
species.
Such genera as Parentactinia, Pactarentinia
and Tlecerina may be simply termed a latticeshelled Palaeoscenidium. The skeleton of Parentactinia Dumitrica, 1978 (Text-fig. 2b) is composed of a short median bar, four or three apicalspines, four basal spines and an incomplete
sphaerical lattice shell. Medial part of the basals
participates in construction of the shell lattice.
The apical spines are invariably four in number
as far as I could observe in the specimens from
Mt. Yokokura. The PA spine is not very distinct.
Degree of differentiation of the PA spine israther different from specimen to specimen.
When it is discriminated, other spines are termed
like Palaeoscenidium.
Pactarentinia n. gen. (Text-fig. 2c) is composed of Palaeoscenidium-like eight-spined spicule and complete globular lattice shell. The
number of the apical and basal spines is invariably four respectively. The shell covers
medial part of the basal spines. The basal spines
bear spinules on the covered part by the shell.
The median bar is situated slightly above thelevel of the shell surface. A small tent-like shell,
consisting of the median bar, proximal partsof the basal spines and imperforate lamellae,
penetrates the lattice shell from the inner toouter side. The PA spine is distinct. Other spines
are named in the same rule as Palaeoscenidium(Pl. 23, Fig. 1a).

100

Hiroshi FURUTANI

Tlecerina n. gen. (Text-fig. 2d) is a single
sphaerical lattice·shelled form with eight-rayedpolarized spicule in the shell. The internal spicule
is just like Palaeoscenidium. It is composed ofa short median bar, four shorter rays bearing
very small spinules and four longer rays bearing
longer spinules and a lamellate tent-like shell
which is made up of the median bar, proximal
parts of the longer rays and imperforate lamellae.
The median bar is not recognized as a distinct
bar by the development of the tent-like shell.
Tlecerina has six to eight main spines in themeaning of Foreman (1963). Each spine connects with one of the rays of the internal spicule.
One of the main spines is four-bladed and more
massive than any other main spines. The thickest
main spine always connects with one of theshorter "apical" rays, commonly with the thickest apical ray, of the spicule. The thickest spine
plus the connected ray obviously homologous
to the principal apical spine of other genera.
The thickest apical· spine is termed principal
apical spine (PA spine in abbreviation), andthe rays connecting with the PA spine is termedprincipal apical ray (PA ray in abbreviation).
Other rays are termed as follows, however,"ray" is used instead of "spine" (PI. 24, Figs. 1,
3a);counter apical ray: an apical ray situated opposed to the PA ray (CA ray in abbreviation)
lateral apical ray: an apical ray paired with the
PA ray (LA ray in abbreviation)
counter lateral apical ray: an apical ray pairedwith the CA ray (CLA ray in abbreviation)
PB ray: a basal ray underlying to the PA ray
CB ray: A basal ray underlying to the CA ray
LB ray: a basal ray underlying to the LA ray
CLB ray: a basal ray underlying to the CLA ray
Four of the main spines except the PA spine
always connect with the basal rays of the internal
spicule. They are less massive than the PA spine
and ususally three-bladed or rod-like. Remaining
one to three spines are generally weakly developed and connect with the rest of the apicalrays. When the remaining spine is one in number,it always connects with the CA ray. The main
spines except the PA spine are termed as follows(PI. 24, Figs. 1, 3a; Pl. 26, Fig. 3a);counter apical spine: a spine connecting with the
CA ray (CA spine in abbreviation)
lateral apical spine: a spine connecting with the
LA ray (LA spine in abbreviation)
counter lateral apical spine: a spine connectingwith the CLA ray (CLA spine in abbreviation)
PB spine: a spine connecting with the PB ray
CB spine: a spine connecting with the CB ray
LB spine: a spine connecting with the LB ray
CLB spine: a spine connecting with the CLB ray
In general, extending directions of the spines
more or less reflect the direction of the spicular
rays.
Above discrimination of each spine or ray
will be good aid for understanding skeletal
construction and systematics of Palaeoscenidiinae, and phylogenetic relationship between
Palaeoscenidiinae and other groups.
The next problem is whether the PA spine
would seem to extend to the right or left fromthe end of the median bar, if we stood on theapical side of the median bar, although biologicalsignificance of it is unknown. In the herein
described species of Pactarentinia and Tlecerina,
the right extending and the left extending forms
are almost equally observed even in a species.
In Palaeoscenidium of Fukuji, in contrast, theright extending form apparently exceeds theleft extending one.
In some species of palaeoscenidiins, the angle
between the PB and LB spines, or the CB and
CLB spines is larger than the angle between the
PB and CLB spines, or the CB and LB spines.
This phenomenon is commonly observed amongmy specimens of Palaeoscenidium and Parentactinia vetustum. However the spicule of Pactarentinia holdsworthi has not such character.
In Tlecerina it is not confirmed.
In a species of Telecerina (T. (enestrata)
usually one large pore opens above the medianbar. The apical spines are disposed round thepore. The pore is termed apical window. On
the detail of the apical window, see a descriptionof Tlecerina {enestrata.
Pentactinocarpinae, another subfamily of

763. Middle Palaeozoic Palaeoscenidiidae (Radiolaria)

Palaeoscenidiidae, contain five genera such as
Palacantholithus? Deflandre [=Triassothamnus
by Kozur and Mostler, 1981], Pentactinocarpus
Dumitrica, Pentactinocapsa Dumitrica, Pentactinorbis Dumitrica and Lobactinocapsa Dumitrica.
They are throughout described and illustratedby Dumitrica (1978) on the basIs of the excellently preserved specimens from the Middle
Triassic of Italy and Romania. Palacantholithus?
is a pentactin spicular form and other four genera
are a lattice-shelled form in some kinds ofmanner. They are all characterized by having
a pentactin spicule consisting of an apical spineand four basal spines without the median bar.
The apical spine is most probably homologous
to the principal apical spine of Palaeoscenidiinae.
Extent of Palaeoscenidiidae
Palaeoscenidiidae are characterized by having
a five- to eight-spined and strongly polarized
spicule, while Entactiniidae, which are one of
the best known group amongst Palaeozoic
radiolarians, have a typically six- to four-spined
spicule with no strong polarity in itself. Generally they are easily distinguishable by strong
polarity in the spiCUle of the former and thenumber of the spines. However, more or lesseccentrically located median bar of the internal
spicule is observed in the medullary shells of
many known species of the Entactiniidae. Hence,
when palaeoscenidiids have six-spined spicule,they may seem to be confusing with entactiniids.
If the typical spicule of palaeoscenidiids is
projected to a perpendicular plane to the medianbar as viewed along the median bar, the projection becomes tetraradiate (Text-fig. 3a) byoverlapping one spine upon the other. The four
pairs are the PA and CLA, the CA and LA,
the PB and CLB, and the CB and LB spines.
On the other hand in the typical spicule ofentactiniids, such as Haplentactinia a rrhinia
Foreman, the projection becomes hexaradiateby radiations of each spine from the centerwith an interval of 60° (Text-fig. 3b). Whenan apical spine degenerates at each end of themedian bar of palaeoscenidiids, the LA and101

CLA spines are expected to extinct, the projection of the spicule becomes tetraradiate if
the two apicals preserve the original extending
direction, or triradiate if the apicals extend
in a plane containing the median bar (Text-fig.
3c). In the forms having a six-spined spicule,whether the projection of the spicule is tetraradiate or triradiate, or hexaradiate may be a good
criterion for discrimination between palaeoscenidiids and entactiniids.
Some of the known entactiniids, which havea six-rayed spicule, actually seem to be able torefer to Palaeoscenidiidae. For example Entactinosphaera {rederic ki Foreman, which waswell illustrated by Foreman (1959, 1963), hasa six-rayed spicule made up of a distinct medianbar, four longer rays bearing a group of spinules
on the each ray and two shorter rays having no
spinules, and the thickest spine among six main
spines connects with one of the shorter rays.
The polarity in the spicule seems to be evident.
Another example is Entactinosphaera unimana
Nazarov in Kruchek and Nazarov (1977). It has
also a polarized six-rayed spicule and a heavier
main spine arising from a shorter ray of the
spicule. The morphology of them reminds usof palaeoscenidiids. However, I assume here they
are entactiniids because the projection of the
spicule of them are supposed to be hexaradiate.
Foreman (1963) presumed that Haplentactinia
arrhinia, with two groups of the spinules on theeach of the spines and without a lattice shell,
Haplentactinia rhinophyusa Foreman, some ofthe proximal groups of the spinules form thebase for a rudimentary lattice shell, and Entactinosphaera fredericki represent three consecutive early stages in the development of theradiolarian lattice shell. If it is correct, the spicule of E. fredericki has originally no polarity,and hence it is not a palaeoscenidiid in accordance with the above assumption. Moreover, thespicule, which seems to be polarized owing to theeccentrically located median bar in the medullaryshell, of many other species of entactiniids may
also originate from the unpolarized entactiniid
spiCUle.
Besides the above-mentioned species, a heavier

102

Hiroshi FURUTANI

from Mt. Yokokura and Fukuji, and presenceof some forms of lattice-shelled palaeoscenidiids
including a species of Parentactinia is clarified by
the present study. Moreover, the projection as
viewed along the median bar is apparently tetraradiate in the Triassic Parentactinia in likemanner of the Devonian species describedherein. It is reasonable to remove Parentactinia
from Entactiniidae to Palaeoscenidiidae andPalaeoscenidiinae, based on the essentially same
spicular system and strong polarity in the spicule.
Archaeosemantis, also described as a entactiniid by Dumitricli (1978), is a curious form
which consists of two apical and four basal
spines with a short median bar. It is apparently
allocated to Palaeoscenidiidae and Palaeoscenidiinae by the strong polarity in its spiCUle.
Dumitricli (1978) regarded it to be a degenerate
form from Parentactinia. His view is highly
acceptable for me.
The Triassic genus Sepsagon Dumitricli, Kozur
and Mostler, 1980 has a spicule consisting of
three apical rays, four basal rays and a medianspine, like that of Tlecerina, than the otheris observed in many species of known entactiniids such as Entactinia cometes Foreman, Entactinia monalloea Foreman, Entactinia? additiva
Foreman, Entactinia. diversita Nazarov, Entactinosphaera riedeli Foreman, Entactinosphaera
euthlasta Foreman, Entactinosphaera palimbola
Foreman, and Entactinosphaera? diplostraca
Foreman. However, origin of the heavier spine
is unknown. Since, unfortunately, detailed
morphology of the internal spicule of them is
not clear, it is impossible to discuss more about
the relationship between Palaeoscenidiidae andthem.
Dumitric~ (1978) proposed the genus Parentactinia and assigned it to the family Entactiniidae,
on the grounds that Triassic forms are morecommonly bar-centered than Palaeozoic Palaeoscenidium and have a globular lattice shell.
However, Holdsworth (1977) defined the family
Palaeoscenidiidae to have most commonly ashort median bar, actually bar-centered Palaeoscenidium is very common in my collectionb
Text-fig. 3. Projections of idealized spicules of Palaeoscenidiinae and Entactiniidae to aperpendicUlar plane to the median bar as viewed along the median bar. Solid lines are the projections of the spines on this side of the median bar, and broken lines are the projections of thespines on the other side of the median bar.

763. Middle Palaeozoic Palaeoscenidiidae (Radiolaria)

bar. The spicule seems to be like that of the
Palaeoscenidiinae, although the exact positionof the median bar is obscure. Thus this genus
very probably belongs to the Palaeoscenidiinae,
and is assumed to relate to Parentactinia, because
the medullary portion is comparable to Parentactinia in respect of the number of the apicalrays and the relationship between the basal rays
and the latticed medullary shell. Parasepsagon
Dumitrici, Kozur and Mostler, 1980 also probably belongs to the Palaeoscenidiinae, as it has
a similar medullary shell to that of Sepsagon
according to the description by the authors.
Dumitrici et al. (1980) stated that in some
Triassic forms such as Styloshpaera? andHindeosphaera by Kozur and Mostler (1979), and asArchaeospongoprunum? or Actinommid group
A by De Wever et al. (1979) seemed to belong
to the same group with Triassic "entactiniids"
including Sepsagon. Amongst them Hindeosphaera Kozur and Mostler, 1979 has a strong
spine and seven, at the maximum, weak spines.
The external aspect of the genus reminds usof Tlecerina. However, recent work by Kozur
and Mostler (1981) revealed that the innershell resembling that of Pentactinocarpus has apentactin spicule, thus it might relate rather toPentactinocarpinae.
Foreman (1963) proposed the genus Polyentactinia consisting of an irregular lattice shelland a six- to eight-rayed internal spicule. According to her excellent illustration (pI. 9, fig.
5a) and description of Polyentactinia craticulata
Foreman, the type species of this genus, thespicule is very eccentrically located and composed of four spinule-bearing rays and three flatrays. It seems to be clear this genus is referred to
Palaeoscenidiidae. However, I hesitate to do so,
because the supposed projection of the internal
spicule may not be necessarily palaeoscenidiidlike. Nazarov (1975) erected the subfamily
Polyentactiniinae in the family Entactiniidae,
employing Polyentactinia as the type genus,
which are sphaerical-shelled forms having sevenor more-rayed internal spicule radiating fromboth the ends of a median bar or corners of apolyhedron. It may become nomen dubium, if

103

Polyentactinia is allocated to Palaeoscenidiidae.
According to Nazarov (1975), Polyentactiniinae
include such genera as Astroentactinia Nazarov,
Helioentactinia
Nazarov, Spongentactinnella
Nazarov, and Somphoentactinia Nazarov besides
Polyentactinia. Although many species, whichhave the polyhedron in the center of the spicule,of these genera cannot be allocated to either
Palaeoscenidiidae or Entactiniidae, as Holdsworth
et al. (1978) suggested, some species, at least,
possibly belong to Palaeoscenidiidae on accountof their definition. However, it is impossible
to judge precisely whether they are members of
Palaeoscenidiidae or not, owing to a lack ofknowledge on the detail of the internal spiCUle ofthem. I exclude them from Palaeoscenidiidae forthe time being. (See remarks on the Tlecerina.)
A species of "Spumellaria family and genus
indet." illustrated by Holdsworth et al. (1978,
figs. 2v, w), which has at least a single sphaericallattice shell, a strong four-bladed spine and aweaker spine, may relate to Tlecerina. Holdsworth et al. (1978) remarked it has only two
opposed spines, but fig. 2v seems to show threeor more spines. If my view is correct, it is difficult to distinguish this species from Tlecerina,
at least, only by the external aspect. "Aff.
'Cenosphaera' cf. 'C.' cabrierensis Group" by
Holdsworth et al. (1978) may also be in thesame condition.
A species of "aff Entactinia sp." by Fortey
and Holdsworth (1972, pI. 10, fig. 1) possesses
an eccentric six-rayed spicule and a loose
sphaerical shell. Four of the rays generate theshell by terminal bifurcations, and remaining
two emerge immediately the shell. The projection of the spicule is assumed to be triradiate,
and the polarity is apparent. Therefore, thisspecies probably relates rather to Palaeoscenidiidae than to Entactiniidae.
Nazarov in Nazarov and Popov (1980) tentatively assigned Bissylentactinia Nazarov, 1975
to Palaeoscenidiidae. Bissylentactinia is a spicularform having six to twelve spines radiating froma center with spinules on one or two levels of
the each spine. The type species of the genus(B. rudicula Nazarov) has apparently no polarity

104

Hiroshi FURUTANI

in itself. Therefore, the genus Bissylentactinia
should be excluded from Palaeoscenidiidae.
However, Bissylentactinia quadriramosum, which
was first described by Foreman (1963) as Palaeoscenidium? quadriramosum, clearly shows
natures of palaeoscenidiids. Namely it consistsof eight-spined spicule, and four spines of it
bear spinules on one side of the spicule. Thus
it is included into Palaeoscenidiinae.
Deflandre (1960) illustrated many species ofradiolarians from the Lower Carboniferous ofMontagne Noire, France without descriptions.
One of the illustrations (fig. 15, "Lithocannosphaeropsis fallax") shows a somewhat palaeoscenidiid-like internal spicule with one or two
sphaerical shell without external spines. It might
relate to Palaeoscenidiidae.
Some kinds of spicular radiolarians were
described by Deflandre (1973a, b). Among them,although the type species of Palhindeolithus(P. ambiguus) has two groups of four spines
radiating from both ends of the median bar, it
has no trace of the polarity, hence it cannot be apalaeoscenidiid.
Palacantholithus Deflandre, to which Dumitril1(1978) tentatively allocated the Triassic Palacantholithus?, consists of four or five radiating
spines and a perpendicular spine. I can recognize
five spines in the illustration (Deflandre, 1973a,
pI. 3, fig. 2) of the holotype of Palacantholithus

stellatus, which is the type species of the genus,
but the spines do not seem to have the palaeoscenidiid disposition. Moreover, a spicule
possessing five basal spines is totally absent
in palaeoscenidiids. Therefore, the genus Palacentholithus is probably excluded from Palaeoscenidiidae. However, a specimen of pI. 3, fig.
5 is not impossibly a palaeoscenidiid, whereas
Triassic Palacantholithus? belongs to Palaeoscenidiidae without doubt.
Xiphachistrella is also described by Deflandre(1973a, b), and has a strong perpendicular
apical spine and four divergent basal spines
with some arches arising from the apical spine.
Although Deflandre (1973a) considered it might
relate to Ceratoikiscidae, I am of the opinion
that it is rather comparable to Pentactinocarpinae
in the disposition of the five spines. But myconclusion is reserved, because the medial
portion of the spicule remains obscure.
Pylentonemidae Deflandre, 1963 have a barcentered, seven-rayed spicule. The spicule may
rather relate to that of Nassellaria in homology.
Eight-rayed spicular forms have never been
known in it, and the pylome, which all pylentonemids characteristically have, is entirely absent
in Palaeoscenidiidae. Therefore, they are evidently discriminated from each other.
The spicule of Palaeoscenidiidae and that of
Cainozoic Orosphaeridae Haeckel, 1887, which

Explanation of Plate 21
Fig. 1.
1.

Palaeoscenidium sp.
Apical view indicating terms of spines. This specimen was obtained from an older horizon
than Y-19.
Figs. 2, 3. Palaeoscenidium sp. A
2. ESN 144001; a, oblique view; b, apical view.
3. ESN 144002; a, view along the median bar; b, oblique view.
Figs. 4, 5. Parentactinia vetustum n. sp.
4. Paratype (ESN 144003); apical view showing a verticil on an apical spine.
5. Holotype (ESN 144004); a, side view; b, oblique view.
Fig. 6. Palaeoscenidium (s. I.) sp.
6. This specimen was obtained from the Yoshiki Formation (middle or late Ordovician) of
Fukuji, Central Japan.
Scale = 100J,Lm.

FURUTANI: Middle Palaeozoic Radiolaria

Plate 21

763_ Middle Palaeozoic Palaeoscenidiidae (Radiolaria)
was comprehensively described by Friend andRiedel (1967), are closely resembling each otherin having an eight-spined, bar-centered spiculewith strong polarity in itself, as pointed out by
Dumitric! (1978), although the shells of thelatter are far larger than those of the former_
However, I tend to distinguish them for thepresent, because Jurassic and Cretaceous recordof both the family is lacking and the size ofthe skeletons is remarkably different between
them.
Very recently, Takemura and Nakaseko(1982) described two new genera such as Hilarisirex and Diceratigalea from the Jurassic ofCentral Japan under the new subfamily Hilaricirecinae, and they considered this subfamily
belongs to the fa~ily Palaeoscenidiidae basedon their cephalic skeletal structure. Judging
from their descriptions and illustrations, theprojections of their six-rayed spicules become
triradiate. The median bar of their spicules isdistinctively long, although that of previously
known palaeoscenidiids is short. Moreover,a specimen (pI. 70, fig. 2) of Hilarisirex quadrangularis Takemura and Nakaseko, the type speciesof the genus, has a slight protuberance at thesa.me spots as the dozsal and the axial spines of
Nassellaria. Diceratigalea hemisphaera Takemura
and Nakaseko, the type species of the genus,
also has a slight protuberance at the same spot
as the dozsal spine of Nassellaria. These facts
suggest that the "basal spines" of Hilaricirecinae
do not homologous to the basal spines of thefamily Palaeoscenidiidae. Therefore, the Hilaricirecinae are assumed to be excluded from thefamily Palaeoscenidiidae.
It is concluded from above discussions that
Palaeoscenidiinae contain Archaeosemantis andParentactinia, and Sepsagon and Parasepsagon
with slight question, besides Palaeoscenidium,
Pactarentinia n. gen. and Tlecerina n. gen.
Pentactinocarpinae include the five genera
described by Dumitricli (1978). Familial assignment of many other genera or species having
the confusing spicule cannot be decided forcertain owing to a lack of knowledge on thedetailed morphology of the spicule. It is ex-

105

pacted that the morphology of the spicule isstudied in more detail.
Additional remarks
There was a long interval between the latest
records, the Toumaisian of France by Deflandre(1953) and Turkey by Holdsworth (1973), of
Palaeozoic palaeoscenidiids and Middle Triassic
ones. Very recently, however, Ishiga et al. (1982)
discovered Palaeoscendidium? sp. possessing
perforate lamellae between the proximal partsof the neighbouring basal spines, from the upper
Permian of the Tamba Belt, Southwest Japan,
although the median bar and the apical portion
are not preserved. It may be regarded as a link
between the Carboniferous and Triassic records.
Although older occurrences of unshelled
Palaeoscenidium are known from the Japanese
Ordovician (Igo et al., 1980) and the lower
Silurian of Arctic Canada (Holdsworth, 1977),
the present occurrence is the oldest record of
the definitely lattice-shelled Palaeoscenidiinae.
Thus it is assumed that Palaeoscenidiinae acquired the shell between late Silurian and middle
Devonian, at the latest, ages.
In Pentactinocarpinae, if Carboniferous Palacantholithus described by Deflandre (1973a, b)
is a true member of Pentactinocarpinae, although
it is fairly questionable as already discussed,
the spicular form also precedes Triassic shelledforms. Dumitricli (1978) supposed this acquisition had occurred somewhere between late
Carboniferous and Permian ages. Such sequence
shown in both the subfamilies as from the spicular forms to the lattice-shelled forms strongly
suggests evolutional trend of this family. Furutani(1982) briefly discussed the evolution of thisfamily. I will discuss this problem in more detailin a forthcoming paper which will describe
primitive lattice-shelled palaeoscenidiinae from
Mt. Yokokura.
Systematic palaeontology
Subclass RADIOLARIA Muller
Order POLYCYSTINA Ehrenberg

Hiroshi FURUTANI

106
Suborder SPUMELLARIA Ehrenberg

Superfamily Entactiniacea Riedel, 1967
Family Palaeoscenidiidae Riedel, 1967
(emended herein)
1967. Palaeoscenidiidae, Riedel, p. 149.
1971. Palaeoscenidiidae, Riedel, p. 658.
1977. Palaeoscenidiidae, emended, Holdsworth,p.168.
1981. Palaeoscenidiidae, Kozur and Mostler,
p.17.
1981. Pentactinocarpidae, Kozur and Mostler,
p.18.
1981. Parentactiniidae, Kozur and Mostler,
p.34.
1981. ?Sepsagonidae, KozUr and Mostler, p. 35.

Typegenus:-Palaeoscenidium Deflandre, 1953
Diagnosis:-Palaeozoic and Mesozoic radiolarians having bar- or point-centered spicule
which comprises of four to one shorter apicalspines and four, rarely three, longer basal spines.
The median bar is short or absent. A pair of theapical spines and that of the basal spines radiatefrom both ends of the median bar, when the
spicule has eight spines and the median bar. A
lamellate tent-like shell, made up of the medianbar, the proximal parts of the basal spines andimperforate lamellae, is common. The principal
apical spine generally develops. The basal spines
frequently have spinules. The projection of the

spicule to a perpendicular plane to the medianbar becomes tetraradiate or triradiate. Many
genera have one or more lattice shells.
Contained subfamily:-Palaeoscenidiinae Riedel, 1967, Pentactinocarpinae Dlo!-,mitrica, 1978.
Remarks:-Systematic position of this family
at suborder rank had remained as incertae sedis
since the establishment by Riedel (1967) until
recently. Holdsworth (1977) tentatively assigned
this family to the suborder Spumellaria, thesuperfamily Entactiniacea on the basis of thepresence of intermediate forms between Haplentactinia and Palaeoscenidium in Cornwallis.
Dllmitrica (1978) proposed Pentactinocarpinae
as a new subfamily of Palaeoscenidiidae. It ischaracterized by having a pentactin spicule,which is composed of an apical spine and fourbasal spines without the median bar, and includes
some kinds of the lattiGe-shelled forms. It wasendorsed that Palaeoscenidiidae belonged to thesuborder Spumellaria by his study. Holdsworth(1977) stated that the suborder assignment of
Entactiniacea was probably incorrect although
it is a tradition. However, because the external
aspect of the lattice-shelled palaeoscenidiidsshows strong resemblance to typical spumellarians, it is the best treatment to assign Palaeoscenidiidae, at least, to Spumellaria in the present
circumstances.
This family is distinguished from the Entactiniidae in the nature of the spicule. The number

Explanation of Plate 22
Figs. 1-4. Parentactinia uetustum n. sp.
1. Paratype (ESN 144005); a, side view showing a long apical spine and a spinule on a basal
spine; b, enlargement of the lattice shell.
2. Paratype (ESN 144006); a, oblique view showing a verticil on basal spines; b, apicalview showing small angles between the PB and CLB spines and the CB and LB spines.
3. Paratype (ESN 144007); a, oblique view showing nodes on the outer surface; b, apicalview.
4. Paratype (ESN 144008); a, oblique view; b, enlargement of the opposite side of the a.
Figs. 5, 6. Pactarentinia holdsworthi n. gen., n. sp.
5. Paratype (ESN 144009); apical view.
6. Paratype (ESN 144010); side view.
Scale = 1001lm.

FURUTANI: Middle Palaeozoic Radiolaria

Plate 22

763. Middle Palaeozoic Palaeoscenidiidae (Radiolaria)of the spines of the spicule is five to eight andthe apical-basal polarity is evident in the former,
while the number is four to six or rarely more
and the polarity is not clearly recognized in
the latter. Moreover, the projection of the spicule
is tetraradiate or triradiate in the former, whilethat of the latter is not so and it becomes hexaradiate in the most common six-spined spicule.
Subfamily Palaeoscenidiinae Riedel, 1967
(emended herein)
1967. Palaeoscenidiidae, Riedel, p. 149.
1971. Palaeoscenidiidae, Riedel, p. 658.
1977. Palaeoscenidiidae, emended, Holdsworth,p.168.
1981. Palaeoscenidiidae, Kozur and Mostler,
p.17.
1981. Parentactiniidae, Kozur and Mostler,
p.34.
1981. ?Sepsagonidae, Kozur and Mostler, p. 35.
Type genus:-Palaeoscenidium Deflandre,
1953
Diagnosis:-Palaeoscenidiidae which have a
spicule possessing two to four apical spines, withor without one or more lattice shells.
Remarks:-Palaeoscenidiinae are distinguishedfrom Pentactinocarpinae by the character of the
spicule. The spicule of the latter is composed ofan apical and four basal spines without a medianbar, whereas that of the former made up of
two to four apicals and four basals usuallywith a median bar.
Contained genera:-Palaeoscenidium; Archaeosemantis Dumitrica, 1978; Parentactinia Dumitrica, 1978; Pactarentinia Furutani n. gen.;Tlecerina Furutani n. gen.; ?Sepsagon Dumitrica,
Kozur and Mostler, 1980; ?Parasepsagon Dumitrica, Kozur and Mostler, 1980.
Genus Palaeoscenidium Deflandre, 1953
1953. Palaeoscenidium Deflandre, p. 408.
Type species:-Palaeoscenidium cladophorum
Deflandre, 1953
Diagnosis:-Palaeozoic Palaeoscenidiinae usu·
ally with straight basal spines and the tent·like107

shell and without rings formed by the basal
spines.
Remarks:-Palaeoscenidium differs from Archaeosemantis in having no rings formed by
the basals and disposition of the spinules.
Although only two species of Palaeoscenidium
have ever been described, some distinctive forms
are recognized amongst only illustrated Palaeoscenidium, which conform to the above diagnosis, by Holdsworth (1977) and in this paper(PI. 21, Fig. 6). When such forms are described,
it will be needed to erect new genera for them.
Contained species:-Palaeoscenidium cladophorum; Palaeoscenidium (s. I.) quadriramosum
Foreman, 1963.
Palaeoscenidium sp. A
PI. 21, Figs. 2, 3
Materia/:-Two specimens were examined bya scanning electron microscope (SEM).
Description:-Eight-spined form, two apicaland two basal spines arise from each end ofa short median bar. The PA spine is distinct,
needle-like, thickest and longest of the four
apical spines. The CA and LA spines are also
needle-like, well developed. The CLA spine may
only be a trace. The basal spines are four innumber, longer than the PA spine, and needlelike. Spinules arise from the lateral sides of theproximal portion of each basal spine towards
the neighbouring basal spines. The length of the
spinules is unknown owing to destruction ofthem. Proximal ends of the basal spines andthe median bar are connected by imperforate
lamellae which thus make a small tent-like shell.
The angle between the PB and LB spines, or
the CB and CLB spines is larger than the angle
between the PB and CLB spines, or the CB andLB spines.
Dimensions:-Length of the PA spine 50J1,
as far as preserved; length of the basal spines
100J1; angle between the PB and LB, or the CB
and CLB spines 80° and 51° (ESN 144001), and68° (ESN 144002); angle between the PB and
CLB, or the CB and LB spines 55° (ESN 144001)

108

Hiroshi FURUTANI

and 35° (ESN 144002).
Remarks:-This species rarely occurs in the
Tlecerina horrida assemblage. Presence or abo
sence of the lattice shell is not confirmed owing
to ill·preservation, thus exact generic positionof this species is obscure. This species differsfrom Palaeoscenidium cladophorum in thesmaller size of the skeleton and the number ofthe spinules, and the arising position of the
spinules. A proposal of a new specific name forthis species is reserved because of ill·preservationand the poverty of the specimens.
Genus Parentactinia Dumitricii, 1978
1978. Parentactinia Dumitrica, p. 49.

Type species:-Parentactinia pugnax Dumi·
tricii, 1978
Diagnosis:-Palaeoscenidiinae with single, im·perfect, sphaerical and irregularly latticed shellunder the basal spines. A part of each basal
spine lies in the thickness of the lattice shelland forms a part of the shell lattice. Apicalportion of the shell is usually opened.
Remarks:-Nevertheless no occurrence ofPare~tactinia is recorded during Carboniferous
and Permian times, strong affinity of the Devoni·an form to the Triassic forms does not permit
an erection of a new genus for the Devonian
form. Parentactinia differs from Pactarentinia

n. gen. on the grounds that a part of each basal
spine of the latter is covered by the shell, andthe sphaerical shell of the latter is complete
unlike the former.
Contained species: Parentactinia pugnax; P.
inerme Dumitricii, 1978; P. vetustum Furutani
n. sp.
Parentactinia vetustum n. sp.
PI. 21, Figs. 4, 5; PI. 22, Figs. 1-4

1982. Parentactinia sp. A Furutani, pI. 1, fig. 5.

Holotype:-Reg. No. ESN 144004.
Material:-Twenty·five specimens were ex·amined by the SEM.
Diagnosis:-Parentactinia with eight straightneedle· or rod·like spines, a tent-like lamellate
shell and small lattice shell. The basal spines
have a verticil of two or three spinules. The
similar verticil is frequently observed on theapical spines.
Description:-Eight.spined and bar·centeredspicule with single incomplete sphaerical lattice
shell under the basal spines. The spicule com·prises of a short median bar, invariably fourneedle· or rod·like apical spines and four straightslightly tapered rod·like basal spines. The PA
spine is indistinct. The basal spines have a verticilof two or three spinules at a distance of 10012011 from the median bar. The apical spines

Explanation of Plate 23
Figs. 1-u. Pactarentinia holdsworthi n. gen., n. sp.
1. Paratype (ESN 144011); a, apical view indicating terms of spines; b, side view.
2. Paratype (ESN 144012); apical view showing the long PA spine.
3. Holotype (ESN 144013); a, slightly oblique view showing a curved basal spine; b, apicalview; c, side view.
4. Paratype (ESN 144014); a, apical view showing comparatively well developed the CA,
LA and CLA spines; b, oblique view.
5. Paratype (ESN 144015); broken specimen showing internal structure.
6. Paratype (ESN 144016); broken specimen showing internal structure.
Fig. 7. Tlecerina horrida n. gen., n. sp.
7. Paratype (ESN 144017); specimen showing the PA and CA spines (upper two) and threebasal spines (lower three), note extending directions of them.
Scale = 10011m.

FURUTANI : Middle Palaeozoic Radiolaria

Plate 23

763. Middle Palaeozoic Palaeoscenidiidae (Radiolaria)
also frequently have a similar verticil. A tent·likeshell, which consists of the proximal parts ofthe basal spines, the median bar and imperforate
lamellae, develops with concave under margins.
The angle between the PB and LB spines, or
the CB and CLB spines is larger than. the angle
between the PB and CLB spines, or the CB andLB spines. Medial portion of each basal spine
takes part in the construction of the shell lattice.
The lattice shell is small, opened in apical region.
Pores are very variable in size and shape, large
and circular near to the basal spines, subcircularor subrectangular in other parts. Small conicalby-spines arise from the intervening bars of thepores. Numerous minute nodes are distributedon the outer surface of the latticed and tentlike shells.
Dimensions:-Diameter of the lattice shell
100-13011; length of an apical spine 20011 basedon a specimen (ESN 144005, PI. 22, Fig. 1);
angle between the PB and LB, or the CB and
CLB spines 60°-65°; angle between the PB and
CLB, or the CB and LB spines 45°-60°
Remarks:-Parentactinia vetustum n. sp. iscommonly found in the Tlecerina horrida assemblage. This species is distinguished from
Parentactinia pugnax in having the tent-likeshell, invariably straight basal spines, verticillate
spinules on the basal spines or apical spines andlonger apical spines.
Etymology:-Latin vetustus -a - um, means
old.
Genus Pactarentinia n. gen.

Type species:-Pactarentinia holdsworthi Fufutani n. sp.
Diagnosis:-Palaeoscenidiinae with single sphaerical lattice shell and rod- or needle·like spines.
A part of each basal spine covered by the shell.
The median bar is situated above the shell.
Remarks:-Pactarentinia somewhat resembles
Parentactinia in the location of the lattice shell,
but differs from the latter in the following
respects. The lattice shell of the latter does notcover the basal spines, and is not complete unlike
the former. This genus is distinguished from109

Tlecerina n. gen. by the location of the medianbar, inside of the lattice shell in Tlecerina, andhaving rod-like spines unlike the bladed spinesof Tlecerina. "Parentactinia pugnax?" illustratedby Dumitrica (1978, pI. 4, fig. 4) might be
an intermidiate form between this genus andTlecerina.
Contained species:-Pactarentinia holdsworthi
n. sp.
Etymology :-Pacterentinia (feminine) is ananagram of Parentactinia.
Pactarentinia holdsworthi n. sp.
PI. 22, Figs. 5, 6; PI. 23, Figs. 1-6
1982. Pactarentinia (MS), sp. A Furutani, pI. i,
fig. 6.
Holotype:-Reg. No. ESN 144013.
Material:-Forly-four specimens were exmined by the SEM.
Diagnosis:-Pactarentinia with a prominent
PA spine, weak other apical spines and, usually,
numerous small by-spines.
Description:-Eight·spined and bar-centeredspicule with single sphaerical lattice shell. The
spicule comprises of a short median bar, four
downward rod·like basal spines, a prominent
rod-like PA spine and three conical or needlelike other apical spines. The PA spine is long. In
a specimen having perfectly preserved PA spine,
it measures 30011 (PI. 23, Fig. 2). The basal
spines are also long. The angle between the PB
and LB spines, or the CB and CLB spines isapproximately the same with that betweeen
the PB and CLB spines, or the CB and LB spines.
A small tent·like shell, which is formed bylamellae connecting proximal portions of thebasal spines and the median bar, penetrate
the lattice shell from inner to outer side. Spinules
arise from the covered parts of the basal spines
by the lattice shell. Some of the spinules fuseto the shell. Rarely the basal spines directly fuseto the shell to form the shell lattice. The basal
spines frequently have a support at the justemerged part from the lattice shell. The lattice
shell sometimes slightly compressed in the apicalbasal direction. Pores are variable in shape, as
circular to subangular, and in size. In many

Hiroshi FURUTANI

110

specimens, small needle-like by-spines arise
from the intervening bars especially from thejunctions of the bars. The shell surface seems
to be smooth in some specimens.
Dimension:-Diameter of the lattice shell
11O-140ll.
Remarks:-Pactarentinia holdsworthi is oneof the most abundant species in the Tlecerina
horrida assemblage.
Etymology:-This species is named for Dr.
Brian K. Holdsworth in honour of his great
contributions to the study of Palaeozoic radiolarians.
Genus Tlecerina n. gen.

Type species:-Tlecerina horrida Furutani
n. sp.
Diagnosis:-Palaeoscenidiinae containing the
spicule in single sphaericallattice shell with six toeight, commonly bladed, main spines connectingwith rays of the spicule. The principal apicalspine is distinct and bladed.
Remarks:-Although Nazarov's (1975) descriptions and illustJ;,ations are, unfortunately,
not enough for full understanding of the internal
spicule of Astroentactinia, Tlecerina is somewhat
similar to Astroentactinia in the number ofthe spicular rays. An illustration (fig. 11) of theinternal spicule of Astroentactinia by Nazarov(1975) seems to be Palaeoscenidium-like, butanother one (fig. 5-V) does not so. Therefore,
Astroentactinia may be a member of Palaeoscenidiidae as already remarked. However, if so,

Tlecerina is distinguished from Astroentactiniain having the distinct PA spine and very rudimentary by-spines.
Contained species:-Tlecerina horrida n. sp.;T. exilis Furutani n. sp.; T. fenestrata Furutani
n. sp.
Etymology:-Tlecerina (feminine) is a nameformed by an arbitrary combination of letters.
Tlecerina horrida n. sp.
PI. 23, Fig. 7; PI. 24, Figs. 1-3; PI. 25, Figs. 1-3
1982. Tlecerina (MS) sp. A Furutani, pI. 1, figs.
7-9.

Holotype:-Reg. No. ESN 144021.
Material:-Sixty-two specimens were examinedby the SEM.
Diagnosis:-Tlecerina with a large lattice
shell (180-210ll), usually six main spines andnumerous thorn-like nodes on the shell surface.
The PA spine is thick.
Description:-Eight-rayed spicule contained ina sphaerical lattice shell with usually six topossibly eight main spines. The internal spicule
is composed of a short median bar, four apicalrays, the PA, CA, LA and CLA rays, and fourbasal rays, the PB, CB, LB and CLB rays. The
PA ray is very commonly the thickest of all .
the apical rays. Numerous minute spinules aredisposed at random on the surface of the apicalrays. All the rays are rod-like and round in thetransverse section. Larger spinules, which haveminute subspinules, arise from the basal rays,

Explanation of Plate 24
Figs. 1-3. Tlecerina horrida n. gen., n. sp.
1. Paratype (ESN 144018); broken specimen indicating terms of rays of the internal spiculeand three main spines.
2. Paratype (ESN 144019); a, side view; b, apical view, note the oblique PA spine; c, enlargement of right side of the a and b showing minute probable CA spine.
3. Paratype (ESN 144020); a, broken specimen showing internal structure and main spines;b, enlargement showing four apical rays and basal view of the tent-like shell; c, note thethick PA spine, thin rod-like CA spine and absence of the LA and CLA spines.
Scale = 100llm.

FURUTANI: Middle Palaeozoic Radiolaria

Plate 24

763. Middle Palaeozoic Palaeoscenidiidae (Radiolaria)

111

and their length proximally increase on the basal
rays. The median bar and proximal parts ofthe basal rays are connected by imperforate
lamellae which thus form a tent-like shell withconcave under margins. Near the inner surfaceof the lattice shell, the basal rays may ramify
some branches which distally amalgamate to
the lattice. The PA, CA, PB, CB, LB and CLB
spines are always present. The CLA spine isobserved in one specimen (PI. 24, Fig. 1). The
LA spine is not yet observed, but may exist.
Extending· directions of the spines more or lessreflect the directions of the spicular rays. The
main spines are fairly variable in shape. The PA
spine is distinct, thickest, gently tapered andusually four-bladed, or very rarely three-bladed,and distally becomes unbladed. Blades of it havea swollen edge. An additional ridge rarely develops in the grooves of the PA spine. Sometimes
the grooves may slightly be spirally disposed.
The CA spine is slender, rod-like or sometimes
three-bladed at the base. The CLA spine isslender when it is present. The basal spines aretapered, three-bladed or sometimes rod-like,and more slender than the PA spine, and distally
become round in the transverse section. They
are rarely four-bladed, but easily distinguishedfrom the PA spine by the slender blades. The
sphaerical lattice shell is large and thick. Poresof the shell are circular or subcircular in shapeand rather irregular in size. Numerous small
thorn-like nodes are disposed on all over theouter surface of the lattice shell. Inner surfaceof the shell is smooth.
Dimension:-Diameter of the sphaerical shell180-21011.
Remarks:-Tlecerina horrida is the mostabundant species in the Tlecerina horrida assemblage. This species resembles Tlecerina sp.
A, but the former differs from the latter inhaving generally thicker spines and no distinct
by-spines.
Etymology:-Latin horridus -a -um, meansrough.

Holotype:-Reg. No. ESN 144024.
Material:-Fifty-two specimens were examinedby the SEM.
Diagnosis:-Tlecerina with a thin mediumsized (150-18511) sphaerical lattice shell andinvariably six slender main spines. Small byspines arise form junctions of the intervening
bars. Numerous small nodes are disposed on
the lattice shell.
Description:-Eight-rayed, bar-centered spicule contained in a sphaerical lattice shell withinvariably six main spines. The internal spicule
consists of a short median bar, four apical rays,
the PA, CA, LA and CLA rays, and four basalrays, the PB, CB, LB and CLB rays. Imperforate
lamellae connecting with the median bar andproximal parts of the basal rays make a tent-likeshell with concave under margins. The rays are
rod-like and round in the transverse section.
The basal rays have perpendicular spinules,
bearing very small subspinules, especially on
the proximally two third part of them. The
apical rays may have minute spinules. The main
spines are the PA, CA, PB, CB, LB and CLB
spines. The LA and CLA spines are absent. The
PA spine is four-bladed, slender and not very
tapered. Other main spines are three-bladed,more slender than the PA spine, and also notvery tapered.
Pores are circular, subcircular or oval in shapeand variable in size. Th intervening bars are
slender and have a weak edge. Small needle-likeby-spines arise from the junctions of the intervening bars. Numerous small nodes are observed
upon the outer side of the lattice shell. The
inner side of the shell is smooth.
Dimension:-Diameter of the lattice shell
150-18511.
Remarks:~Tlecerina exilis is an abundantspecies in the Tlecerina horrida assemblage.
This species differs from Tlecerina horrida inhaving slender and not so tapered spines, thinintervening bars, and well developed by-spinesfrom the junctions of the intervening bars.
Etymology:-Latin exilis -e, means thin.

Tlecerina exilis n. sp.

Tlecerina fenestrata n. sp.

PI. 25, Figs. 4-8; PI. 26, Fig. 1

PI. 26, Figs. 2-4; PI. 27, Figs. 1-4

112

Hiroshi FURUTANI

1982. Tlecerina (MS) sp. B, Furutani, pI. 1,
fig. 10.
Holotype: -Reg. No. ESN 144031.
Material:-Forty-four specimens were examined by the SEM.
Diagnosis:-Tlecerina with a small lattice shell(1l0-1351l), eight main spines and the apicalwindow. The PA spine is outstandingly devel·
oped. Other apical spines are minute.
Description:-Eight-rayed spicule containedin a sphaerical lattice shell with eight main
spines. The internal spicule is made up of a short!Iledian bar, four apical rays, the PA, CA, LA
and CLA rays, and four basal rays, the PB, CB,
LB and CLB rays. At and near the junctions of
the median bar and the basal rays, they areconnected by imperforate lamellae which thus
make a tent-like shell with concave under mar·gins. The apical rays are generally short androd-like, but fairly variable in the length andshape. They may be flattened and proximallytapered when very short. The basal rays arealways rod-like. They have spinules which bear
very small subspinules. Spinules are not observedon the apical rays. The main spines are the PA,
CA, LA, CLA, PB, CB, LB and CLB spines.
Extending directions of them fairly well reflect
the directions of the spicular rays. The apicalspines are disposed around the apical window.
The PA spine is outstandingly developed, fourbladed, gently tapered, and proximally becomes
unbladed. Additional grooves or ridges may
develop on the proximal part of the PA spine.
Other apical spines are minute, not bladed, andsometimes obscure. They are usually not directly
connected with the apical rays. The basal spines
are slender, tapered, always three-bladed at thebase but soon become rod-like, and may slightly
curve to the basal trend. The apical window
opens above the median bar. When the !Iledianbar locates very near to the shell, in other words
apical rays are very short, the apical window
becomes a primary pore, in the meaning of
Baumgartner (1980), of the PA spine. The apic~
winodw is very variable in shape, circular, oval,tear-shaped or gourd-like. It is rarely divided
into two parts (PI. 27, Fig. 4). The lattice shellis small and thin. Pores are fairly variable inshape and size. Short by·spines arise from thejunctions of the intervening bars. NU!Ilerous
minute nodes are distributed on the outersurface of the lattice shell.
Dimension:-Diameter of the lattice shell
11Q-1351l.

Remarks:-Tlecerina fenestrata is very abundant in the Tlecerina horrida assemblage. This

Explanation of Plate 25
Figs. 1-3. Tlecerina horrida n. gen., n. sp.
1. Holotype (ESN 144021); a, side view; b, apical view showing the PA spine and bases of
the CA, PB, LB and CLB spines, note the oblique PA spine.
2. Paratype (ESN 144022); a, side view; b, apical view showing the PA spine and bases of
the CA, PB, LB and CLB spines, note the oblique PA spine.
3. Paratype (ESN 144023); specimen showing base of the PA spine and fine structure ofsurface of the lattice shell.
Figs. 4-8. Tlecerina exilis n. gen., n. sp.
4. Holotype (ESN 144024); a, side view; b, apical view, note the four-bladed PA spine.
5. Paratype (ESN 144025); broken specimen showing the internal spicule.
6. Paratype (ESN 144026); specimen showing the PA, CA and three of basal spines.
7. Paratype (ESN 144027); a, note the strong PA spine; b, fine structure of surface of thelattice shell.
8. Paratype (ESN 144028); broken specimen showing the internal spicule and the PA, CA
and CB spines.
Scale = 1001lm.

FURUTANI: Middle Palaeozoic Radiolaria

Plate 25

763. Middle Palaeozoic Palaeoscenidiidae (Radiolaria)

species is easily distinguished from any otherspecies of this genus by the smaller lattice shelland the presence of the apical window.
Etymology:-Lain fenestra means a window.
Latin suffix -atus -a -um, is added to nounstems to form adjective meaning provided with.
Thus fenestratus -a -um, means provided with awindow.
Tlecerina sp. A
PI. 27, Figs. 5-7

Material:-Six specimens were examined by
the SEM.
Description:-Eight-rayed spicule contained ina sphaerical lattice shell with six main spines.
The internal spicule is composed of four apicalrays and four basal rays. Presence of the medianbar is not confirmed. A "tent-like shell" ispresent. Spinules having very small subspinules
arise from the basal rays. The apical rays also
have minute spinules. All the rays are rod-like.
One of the six main spines which is probably
the PA spine is four-bladed and the thickestof all. Other main spines are slender, and threebladed or ro.d-like. The sphaerical lattice shell
medium to large in size. Pores are rather irregularin size and shape. Needle-like by-spines arise
from the junctions of the intervening bars.
Numerous small nodes are disposed on the wholeof the outer surface of the shell.
Dimension:-Diameter of the lattice shell
15O-190~.

Remarks:-Tlecerina sp. A is tare in the
Tlecerina horrida assemblage. This species differsfrom Tlecerina horrida in having thinner main
spines and distinct by-spines. This species issomewhat similar to Tlecerina exilis in having
slender main spines and distinct by-spines.
However, the former differs from the latter inhaving thicker PA spine and weakly bladed
other main spines. A proposal of a new specificname is reserved, since the specimens are scarcein number.

All specimens registered with the ESN number
are deposited in the Department of Earth Sciences, Nagoya University.

113

References
Baumgartner, P. O. (1980): Late Jurassic Hagiastridae and Patulibracchiidae (Radiolaria)
from the Argolis Peninsula (Peloponnesus,
Greece). Micropaleontology, vol. 26, no. 3,
p. 274-322, pis. 1-12.
Deflandre, G. (1953): Radiolaires fossiles. In
Grasse, P. P. ed., Traite de Zoologie. vol. 1,
pt. 2, p. 389-436, Masson et Cie., Paris.
--(1960): A propos du developpement desrecherches sur les Radiolaires fossiles. Revue
Micropaleont., vol. 2, no. 4, p. 212-218,
pI. 1.
--(1973a): Sur quelques nouveaux types
de Radiolaires Polycystines viseens, d'attribution systematique ambigue, certains
evoquant it la fois des Plectellaires et desSpumellaires. Comptes Rendus Acad. Sci.
Paris, Ser. D, Vol. 276, p. 289-293, pis.
1-4.
--(1973b): Complements historiques et taxinomiques sur les Radiolaires viseens. Remarques critiques sur les Plectellaires. Ibid.,ser. D, vol. 276, p. 497-500.
De Wever, P., Sanfilippo, A., Riedel, W. R. and
Gruber, B. (1979): Triassic radiolarians from
Greece, Sicily and Turkey. Micropaleontology, vol. 25, no. 1, p. 75-110, pIs. 1-7.
Dumitrica, P. (1978): Triassic Palaeoscenidiidae
and Entactiniidae from the Vicentinian Alps
(Italy) and Eastern Carpathians (Romania).
Difri de seamif ale ~edintelor, vol. 64, p. 3954, pis. 1-5.
- - , Kozur, H. and Mostler, H. (1980): Contribution to the radiolarian fauna of the Middle
Triassic of the Southern Alps. Geol. PalCiont.
Mitt. Innsbruck, vol. 10, no. 1, p. 1-46,
pis. 1-15.
Foreman, H. P. (1959): A new occurrence ofDevonian Radiolaria in calcareous concretions of the Huron member of the Ohio
shale. Jour. Paleont., vol. 33, no. 1, p. 7680, pI. 15.
--(1963): Upper Devonian Radiolaria fromthe Huron member of the Ohio shale.
Micropaleontology, vol. 9, no. 3, p. 267304, pis. 1-9.
Fortey, R. A. and Holdsworth, B. K. (1972):
The oldest known well-preserved Radiolaria.

114

Hiroshi FURUTANI

Boll. della Soc. Paleont. Italiana, vol. 10,
no. 1, p. 35-41, pIs. 10-11.
Friend, J. K. and Riedel, W. R. (1967): Cenozoic
orosphaerid radiolarians from tropical Pacificsediments. Micropaleontology, vol. 13, no.
2, p. 217-232, pIs. 1-3.
Furutani, H. (1981): Ordovician and Silurianof the Fukuji area, Gifu Prefecture, withspecial reference to the radiolarian fossils.
In Kano, H. ed., Some geological and petrological problems on the Lower Palaeozoic
and Upper Proterozoic in the JapaneseIslands and its adjacent area., p. 13-16(in Japanese).
--(1982): Skeletal construction and phylogeny of Palaeoscenidiidae. News of Osaka
Micropaleontologists, spec. vol., no. 5,
p. 11-16, pI. 1 (in Japanese' with English
abstract).
Hamada, T. (1961): The Middle Palaeozoic groupof Japan and its bearing on her geologicalhistory. Jour. Fac. Sci. Univ. Tokyo, sec. 2,
vol. 13, pt. 1, p. 1-79.
Hinde, G. J. (1899): On the Radiolaria in the
Devonian rocks of New South Wales. Quat.
Jour. Geol. Soc. London, vol. 55, p. 38-64,
pls.8-9.
Hirata, M. (1966a): On the Upper Devonian
Ohira Formation in the Outer zone of
Shikoku, Japan. Chigakukel1kyu, vol. 17,
no. 4, p. 102-105 (in Japanese with English
abstract).

--(1966b): Mt. Yokokura, Kochi Prefecture.
Ibid., vol. 17, nos. 10-12, p. 258-273,
pls. 1-3 (in Japanese).
Holdsworth, B. K. (1973): The Radiolaria of theBaltalimani Formation, Lower Carboniferous, Istanbul. In Kaya, O. ed., Paleozoic
of Istanbul; Ege Universitesi Fen Fakultesi
Kitaplar Seresi, no. 40, p. 117-134, pI. 1.
- - (1977): Paleozoic Radiolaria; stratigraphic
distribution in Atlantic borderlands. In
Swain, F. M. ed., Stratigraphic micropaleontology of Atlantic basin and borderlands,
p. 167-184, pls. 1-2, Elsevier, Amsterdam.
- - , Jones, D. L. and Allison, C. (1978): Upper
Devonian radiolarians separated from chertof the Ford Lake Shale, Alaska. Jour.
Resear. U. S. Geol. Surv., vol. 6, no. 6,
p.775-788.
Igo, H., Adachi, S., Furutani, H. and Nishiyama,
H. (1980): Ordovician fossils first discoveredin Japan. Proc. Japan Acad., ser. B, vol. 56,
no. 8, p. 499-503.
Ishiga, H., Kito, T. and Imoto, N. (1982): Late
Permian radiolarian assemblages in theTamba district and an adjacent area, Southwest Japan. Earth Science, vol. 36, no. 1,
p. 10-22, pls. 1-5.
Kozur, H. and Mostler, H. (1979): Beitriige zur
Erforschung der mesozoischen Radiolarien.
Teil III: Die Oberfamilien Actinommacea
Haeckel 1862 emend., Artiscacea Haeckel

Explanation of Plate 26
Tlecerina exilis n. gen., n. sp.
Paratype (ESN 144029); a, broken specimen showing the internal spicule; b, basal viewof the internal spicule.
Figs. 2-4. Tlecerina fenestrata n. gen., n. sp.
2. Paratype (ESN 144030); a, side view; b, enlargement of the lattice shell, note three weakapical spines.
3. Holotype (ESN 144031); a, terms of the skeleton are indicated; b, side view showing
seven main spines except the PB spine; c, apical view showing the PB spine at the bottom,
this specimen is probably depressed; d, enlargement of the apical window and three
weak apical spines; e, enlargement of the LA spine, note the internal LA ray.
4. Paratype (ESN 144032); a, oblique view, note the apical window becoming a primarypore of the PA spine; b, enlargement of the apical window, note four apical rays andthe median bar of the internal spicule.
la, 1b, 2a, 2b, 3a, 3b, 3c, 4a; Scale = 100J..Lm.
3d, 3e, 4b; Scale = 10J..Lm.
Fig. 1.
1.

FURUTANI: Middle Palaeozoic Radiolaria

Plate 26

115

763. Middle Palaeozoic Palaeoscenidiidae (Radiolaria)
1882, Multiarcusellacea nov. der Spumellaria
und triassische Nassellaria. Geol. Piilaont.
Mitt. Innsbruck, vol. 9, nos. 1-2, p. 1-132,
pis. 1-21.
- - and --(1981): Beitriige zur Erforschungder mesozoischen Radiolarien. Teil IV:
Thalassosphaeracea Haeckel, 1862, Hexast~!acea Haeckel, 1882 emend. Petrusevskaja,
1979, Sponguracea Haeckel, 1862 emend.
und weitere triassische Lithocycliacea,
Trematodiscacea, Actinommacea und Nassellaria. ibid., Sonderbd., p. 1-208, pis. 1-69.
Kruchek, S. A. and Nazarov, B. B. (1977): Late
Devonian radiolarians from the Russian
Platform. Dokl. Akad. Nauk SSSR, vol. 237,
no. 6, p. 1445-1449 (in Russian).
Nazarov, B. B. (1975): Lower and Middle Paleozoic radiolarians of Kazakhstan. Akad. Nauk
SSSR, Geol. Inst., Trudy, vol. 275, p. 1203, pis. 1-21 (in Russian)--and Popov, L. Yeo (1980): Stratigraphy andfauna of Ordovician siliceous-carbonate deposits of Kazakhstan. Ibid., vol. 331, p. 1190, pIs. 1-32 (in Russian).
Riedel, W. R. (1967): Some new families ofRadiolaria. Proc. Geol. Soc. London, no.
1640, p. 148-149.
--(1971): Systematic classification of polycystine Radiolaria. In Funnel, B. M. andRiedel, W. R. eds., The Micropalaeontologyof Oceans, p. 649-661, Cambridge Univ.
Press, London.
Takemura, A.and Nakaseko, K. (1982): Two
new Jurassic genera of family Palaeoscenidiidae (Radiolaria). Trans. Proc. Palaeont. Soc.
Japan, N. S., no. 128, p. 452-464, pIs.
70-73.
Y oshikura, S. (1982): The geology of the Y okokurayama Lenticular Body and the Usuginu
Conglomerate. Mem. Geol. Soc. Japan,
no. 21, p. 213-229 (in Japanese withEnglish abstract).

Fukuji fIji:ljg, Mt. Yokokura tltft III , Ochi-cho ~~IBJ

i\1lj;;D~'IHtl~1rlllip Gf4Ght-.:q:,WlE1: ~O) Palaeoscenidiidae H (1JJd!x.'R) --to) 1 : Palaeoscenidiidae Hfl. :/& ~ ~;;j.qf9v;::'fl median bar 0) jiIil itlifi 1.1> G :l&M-t" 0 8 *0) spine iJ' G t.r. 0.
,jjUE~t#"':,f-.: spicule '"('!fH1lt-::ivtGh00 8*0) spine I14*f'"?0)Bi:l' apical spine H<l:l' basal spine iJ' G t.r. 00 I-.:/!. L. apical spine III * v;::' ~ '"('l1'}(:}'-t" 0':' C iJ~i!0 00 Palaeoscenidiidae HO)~ O):fifi'"(' apical spine 0) 5 t;, 1 *iJ~!f.'fI;::' J: Je~-t" 0':' C iJ~ ~I>b Gll0 0
7c h::fhO) spine 11, -t O)!f.'f I;::' J: <Je~ L/-.: apical spine c median bar I;::.M-t" 0&iii~(,f­iJ'G, -th::fh~~5J1j-t"0':'CiJ~'"('~00 .:.O)~5JIM Palaeoscenidiidae flfO)'~':f*t~~t~J:~7}<<~~~~t-t" 0J:"t:~)fj'"('i!0 00

Palaeoscenidiidae H 11 Palaeoscenidiinae jffifJr t~ J: ~ Pentactinocarpinae jffiH~~tro
lifj;I!Hl Palaeoscenidium, Archaeosemantis. Parent,actinia, Pactarentinia n. gen" Tlecerina n. gen. 0)4.t~~1!;,;z,... :bfiJ'l;::' ~n~lli!00 {,O)O), Sepsagon, Parasepsagon O)j,fJ

kll ~1!;trc ~*-Gh00
Palaeoscenidium? Parentactinia. Pactarentinia t-; J: ~ Tlecerina 0) 5 ~i1illc 251~:<E1ll!
~llaJlix: L 1-':0 Parentactinia, Pactarentinia, Tlecerina 0) 3 j~fl ffJj~v;::' B *- ff 1l'r'fj&~t-;J."0

1-.: Palaeoscenidium '"(', -thGIlf'I't'f'i&0)5G~0):filgtv;::'J:"0-CIK5JIj~h00 '"?~ '), Parentactinia '"('flt/l'fjfl1:k;t basal spine O)r v;::' & lEt L. Pactarentinia '"('lltl't'fri!l:iJ: basal spine0)-JlI)>:rtil50 "i 1-.:, Tlecerina "t:ll spicule ~{if;iJ::f*'f'i&I;::.m:bh00

lla~~1'Lt-.:1&1IX.'R11~1rlllO) G4 q:,JlI)iJ\G~Ght-.:l;111tJ{:EO) 1 ~*iJ'Gjl~1±l ~ht-.:o :ljg'(!{lIif~fl G4

C J:rO)1!;11:;:fi~ c O)JllllFf~{'f,.

f~~ec*:<E~h00

t-; J: LYJ.l!t9;D 0) E1:ft1&lIX.'R c O)J:t~i;bJ' Glf'-~q:,WJ

~~

m

116

Hiroshi FURUTANIExplanation of Plate 27
Figs. 1-4. Tlecerina fenestrata n. gen., n. sp.
1. Paratype (ESN 144033); broken specimen showing the internal spicule, note the broken
apical window.
2. Paratype (ESN 144034); specimen showing four apical rays.
3. Paratype (ESN 144035); a, side view; b, enlargement of the apical window.
4. Paratype (ESN 144036); a, side view; b, enlargement of the divided apical window.
Figs. 5-7. Tlecerina sp. A
5. ESN .144037; a, oblique view; b, base of the PA spine and fine structure of surface ofthe lattice shell.
6. ESN 144038; note distinct by-spines.
7. ESN 144039; a, broken specimen showing the internal spicule; b, base of the PA spineand fine structure of surface of the lattice shell.
Scale = 100J.lm.

FURUTANI: Middle Palaeozoic Radiolaria

Plate 27

Trans. Proc. Palaeont. Soc. Japan, N. S., No. 130, PP. 117-122, July 15, 1983

764. URANIUM-SERIES AGES OF SOME SOLITARY CORALSFROM THE RIUKIU LIMESTONE ON THE KIKAI-JIMA ,R YUKYU ISLANDS*AKIO OMURA
Department of Earth Sciences, Faculty of Science,
Kanazawa University, Kanazawa 920

Ab st ract. 230Th/234 U ages averagIng. 82,000±2,000 years old were determined
for .t~ee sp.ecies of ahermatypic solitary corals (Trochocyathus hanzawai, Micrabacia japomca and Flabellum rubrum) from the Riukiu Limestone of grainstonefacies in the northern area of Kamikatetsu, Kikai-jima, Ryukyu Islands. It is most
likely that this type of limestone was deposited at the water depth of 120 m or lessas a forereef sediment, in front of the reef which has been elevated up to 184 m inpresent altitude by the vertical tectonic movement and is now forming a marine
terrace developing to the south of Gusuku. The surface of terrace including thedated grainstone is thought to be partly constructional and partly erosional. Because two types of limestone, coralline limestone and this grainstone formed
separately during times of two interstadial high sea stands (approximately 60,000
and 82,000 years ago, respectively), are recognized in the terrace deposit distributed at the same altitude.

Introduction
230Th/ 234 U ages for some solitary corals fromthe Riukiu Limestone on the Kikai-jima, Ryukyu
Islands, are dealt with in this paper. These are
not only the first dates from the other type oflimestone than that formed as a reef itself, butalso one of the most valuable informations toreconstruct the paleoenvironment under whicha coral reef was developed and to discuss thetectonic history of the island.
The staircase morphology of the Kikai-jimais essentially due to the mutual relationshipbetween the construction of coral reefs during
times of Pleistocene high sea stands and thetectonic movement, vertical displacement up
to the present time. The Pleistocene reefs are* Received July 5, 1982; read Jan. 24, 1982 at
Chiba.

occurred landward, developing five or probably
more marine terraces bounded by the remarkableterrace scarps, while the Holocene reefs are
surrounding the whole island in the maximum
width of about 1.2 km, forming topographicallydistinctive four terraces. They have been chronologically studied in some detail by means of
the uranium-series dating techniques like 230Th/
234U and 231 Pa/ 23S U methods and the radiocarbon method of dating, as shown in works of
Konishi et al. (1974) and Ota et al. (1978).
So far, the Pleistocene limestone (Riukiu
Limestone of Hanzawa, 1935) on the Kikaijim a has been thought to be an assortment ofseveral reef complexes, each of which was dated
to be 35,000-45,000, 55,000-65,000, 80,000100,000 and 120,000-130,000 years (Konishi
et al., 1974). The individual reef complex has
been correlated with the elevated Pleistocene
reefs in other areas, e.g. Barbados, West Indies

117

AkioOMURA

118

Tanega:~himat....

Yaku-shima•,

Amami-o-shima
On. Onotsu
Sh. Shitooke
No. Nakaguma
So. Somachi
Ak. Akaren
Wa. Wan
Tk. Takigawa
Gu. Gusuku
Kd. Kadon
Kw. Kawamine
Ar. Araki
Km. Kamikatetsu.-~ Tokuno-shima" Okierabu- j ima

Inawa-jima
3km:

Fig. 1. Index map showing the localities of samples stated in the present paper.
(Black arrow shows the sampling site of solitary corals examined in this study. See
text for details.)(Bender et al., 1979; and others) and the Huon
Peninsula, New Guinea (Bloom et al., 1974;
and others). However, details of stratigraphic
relations among those reef complexes andtheir distribution remain still equivocal. The
major reasons of it seem to be that only hermatypic corals from the reefy limestone have been
dated before and that stratigraphy has not been
completely resolved, because of limited numbersof outcrops on the island.
Radiochemical analyses for uranium andthorium isotopes were carried out on three
species of ahermatypic solitary corals, Trochocyathus hanzawai, Micrabacia japonica andFlabellum rubrum, selected out of many species
from an outcrop along a road which lies approximately 650 m north of Kamikatetsu (Fig. 1).
The locality is situated at a height of about
40 min lat. 28°17.1' N. and long. 129°57.2' E.
Because of its unique lithologic nature, thelimestone near by the sampling site has been
attracted the notice of some paleontologists and!
or geologists since the 1930s. It is moderately
sorted, unconsolidated to weakly cemented,
and grain-supported limestone made up of awide variety of small-sized (less than 10 cm indiameter) bioclastics. This limestone can be
regarded as the typical grainstone defined by
Dunham (1962). Foraminifers, brachiopods,
bryozoans, molluscs, echinoids, solitary corals
and fragmental calcareous algae are included
as main bioclastic components, while larger
bioclastics such as hermatypic corals and coralline algae in growth position are seldom or neverseen in this grainstone facies. The bryozoan andcoral faunas in this type of limestone werestudied by Kataoka (1961) and Yabe and Eguchi(1932). They found conclusions independently
upon each full description that this grainstone
was probably deposited at a depth of from 40

764. Radiometric Ages of Solitary Corals
to 100 m or approximately 100 m, respectively.
The details of separation and purification
methods for uranium and thorium isotopes incarbonate samples are omitted here. The overallchemical yields of uranium and thorium isotopes
were checked by using two kinds of 232U_228Th
spikes (Table 1), as yield tracers in the repeatedanalyses for each sample, separately. Alpha
spectrometries were employed by a 4096 channel
multichannel analyzer coupled with four solidstate silicon detector systems.
Table 1. 232U concentration and 228Th/232U
activity ratio of the 232U_228Th spikes usedas yield tracers for checking overall chemicalyield of uranium' and throium isotopes.
(Measurements were carried out on August
26,1981.)

Name of Spike

232U(dpm/g)

228 Th/ 232 U(activity ratio)"Harwell"

22.53±0.20

0.990±0.010"KU (Kanazawa
Univ.)"

17.30±0.10

0.999±0.012

119

X-ray powder diffraction patterns revealed
that all of the s~ples examined in this study
are free of the secondary calcite. This evidence
suggests that they have not been altered mineralogically throughout their diagenetic history.
Results of the alpha spectrometries arepresented in Table 2, in which the 230Th/234U
age of each sample also is shown. The quoted
errors are standard deviation derived fromcounting statistics.
The follOwing equation and half-lives (T1/2)
of objective radionuclides, which were arrangedin the Uranium-Series Intercomparison Project(USIP; Hannon et al., 1979), were used here
in order to calculate the 230Th/234U age:
230Th = 238U [1 - exp (- hot)]+ 34 U - 238U) [Ao/(Ao - ~)] [1- exp (A4t - Aot)]e

238U : Tl/2 = 4.468 X 10 9 years
234U : Tl/2 = 2.48 X 105 years
232U : T1I2 = 7.2 X 10 1 years
230Th : T 112 = 7.52 X 104 years
228Th : T 112 = 1.913 years
224Ra : T 112 = 3.64 days

Table 2. Isotopic composition and 230Th/234U ages of fossil solitary corals from the
Riukiu Limestone on the Kikai-jima.
(*T.h., Trochocyathus hanzawai; M.j., Micrabacia japonica; F.r., Flabellum rubrum:
For the same sample, the results in upper and lower rows were obtained by use of"Harwell" and "KU" spikes, respectively.)
Material *

T.h.

M.j.

F. r.

238U
(ppm)

Isotope Concentration
234U
232Th
(dpm/g)
(ppm)

230Th
(dpm/g)234UP38U 230Th/234U

3.56± 0.082.92± 0.061.57± 0.031.10± 0.020.521± 0.01579 ± 43.46± 0.062.92± 0.051.49± 0.031.11± 0.020.521± 0.01479 ± 34.42±·0.123.72± 0.101.91± 0.051.13± 0.020.513± 0.02077 ± 41.99± 0.041.09± 0.020.539± 0.01783 ± 4<0.02

Activity Ratio

230Th/234U
Age(x 10 3 yrs)

4.46
± 0.113.69± 0.093.77± 0.103.22± 0.081.78± 0.041.15± 0.020.553± 0.01485 ± 54.34± 0.083.59± 0.061.94± 0.041.11± 0.020.540± 0.01483 ± 3

120

Akio OMURA

where AO and A4 are decay constant of 230Th
and 234 U, respectively.
The 230Th/234U activity ratios in Table 2
are characterized by the limited range of 0.513±0.020 to 0.553±0.014, and accordingly the
230Th/234U ages are in agreement within thestatistical error. The mean age is calculated to be
82,000±2,000 years.
This 230Th/234U age is most reliable for somereasons itemized below:(1) All samples are entirely free of recrystalli·zation, as shown by the absence of thesecondary calcite.
(2) It can be safely assumed from the repro·
ducibility in the analyses repeated by using
two sorts of 232U·228Th spikes that all of theanalytical values in the table are truthworthy.
(3) 238U concentration of each sample almost
equals those which have appeared in litera·ture for ahermatypic corals to date.
(4) The assumption of negligible initial 230Th
is supported by the observation that 232Th
concentration does not exceed the analyticallimitation (0.02 ppm in this study).
(5) The average 234U/238U activity ratio of
1.12±0.01 is consistent with the mean valueof 230Th/234U ages.
The 230Th/234U age of 82,000 years fits inthe time of an interstadial phase after the lastinterglacial stage. The reef complex including
the grainstone facies is correlative with theterrace deposit composed of the Barbados terrace
I of Mesolella (1968) and the Worthing terraceof Bender et al. (1979) on Barbados, West Indies,
and with the reef complex V on the Huon
Peninsula in New Guinea (Bloom et al., 1974).
Konishi et al. (1974) proved the existence ofthe reef which was formed at that time andstratigraphically separated it as the Middle
Limestone Member from their former Younger
Limestone Member of Riukiu Limestone (Konishi
et al., 1970), because the same 230Th/234U dates
were obtained from two hermatypic coral
samples (CK·24, Favia sp., 81,000±3,000 yrs.;
CK-29, Porites sp., 86,000±4,000 yrs.). However,the details of this uplifted reef complex on theisland, namely the distribution and the lithologic

nature of its fore reef sediment, are not yet
definitely solved.
The Riukiu Limestone of the grainstonefacies can be traced also in the eastern area ofthe locality where the samples analyzed in thepresent study were collected. The maximum
height of the area is about 70 m. The present
elevation of the reefy limestone dated as ap·
proximately 80,000 years old is 184 m at the
maximum. The difference in distributing height
between the reefy limestone and the grainstoneof the same age is 114 to 144 m. Assumingthat both facies have undergone the verticaldisplacement of the same extent up to thepresent time, this difference may be roughly
taken as the depth of water where the grainstone
was deposited. The actual depth of sedimentation, however, may be less than 120 m, becauseof local difference in vertical displacement
expected from the existence of some faults asseen in the geologic map of Konishi et al. (1974).
Such an inference seems to be well-matchedwith the conclusions drawn from the faunalanalyses for bryozoans and solitary corals by
Kataoka (1961) and Yabe and Eguchi (1932),
respectively. In any case, there is very little
doubt that the Riukiu Limestone near by the
locality, where the samples dated here werecollected, was deposited as a forereef sediment.
Besides the grainstone, some different typesof limestone are occurred as the terrace deposits
on the same terrace. In other words, the lateralchange of limestone facies is obviously recog·
nized in the terrace deposit. The 230Th/234U agesof 55,000 to 65,000 years have been previously
reported on two hermatypic corals (CK-5,
Acanthastrea echinata, 59,000±5,000 yrs.; CK21, Cyphastrea sp., 54,000±2,000 yrs.) fromthe coralline limestone (Younger Limestone
Member of Riukiu Limestone) by Konishi et al.
(1974). The author also has once dated a fossil
hermatypic coral sample (CK·22, Porites sp.)and got the respective 230Th/234U and 231 Pa/ 235 U .
ages of 52,000±3,000 and 61,000±3,000 years.
Those samples were collected at the spot which
is very close to the locality of the solitary coral
samples examined in this study and which is121764. Radiometric Ages of Solitary Coralsof the same height, 40 m above sea level. Allsuch dates are in accord with the age of anotherinterstadial phase, being represented by thereef complex IV on the Huon Peninsula, New
Guinea (Bloom et al., 1974).
The evidence stated above may imply thata couple of limestone units formed separately
during times of two interstadial high sea stands
are now seen on the same terrace. The sea levelof 55,000 to 65,000 years B.P. is thought tohave been apparently attained up to 40 m or
more in present altitude, regardless of the subsequent tectonic movement. A part of the terrace
surface, therefore, appears to have been eroded
at that time or in process of upheaval to thepresent elevation. After all, it can be safely said
that the surface of terrace extending to the northof Kamikatetsu is partly constructional andpartly erosional.
In conclusions, the author can briefly summarize as follows:(1) Six 230Th/234U ages, the mean of which is
82,000±2,000 years, were obtained for three
species of ahermatypic solitary corals fromthe Riukiu Li~estone of grainstone facies
distributed in the northern area of Kamikatetsu, Kikai-jima, Ryukyu Islands.
(2) Such a grainstone was deposited as theforereef sediment while the reefy limestone
occurred in Gusuku and its vicinity wasformed during a time of interstadial highsea stand, about 82,000 years ago.
(3) The surface of terrac"e, which is extending
at a height of 40 m to the north of Kamikatetsu, is very likely to be partly constructional and partly erosional.
Acknowledgements
The author wishes to thank Dr. Kei Mori of
the Institute of Geology and Paleontology,
Faculty of Science, Tohoku University, for
his identification of coral specimens used in
the present paper. This study was financed by
the Grand-in-Aid (No. 56540481) from the
Ministry of Education, Science and Culture.

References
Bender, M. L., Fairbanks, R. G., Taylor, F. W.,
Matthews, R.K., Goddard, J.G. and Broecker.
W. S. (1979): Uranium-series dating of
the Pleistocene reef tracts of Barbados,
West Indies. Geol. Soc. Amer. Bull., Part I,
vol. 90, p. 577-594.
Bloom, A L., Broecker, W. S., Chappell, J. M. A,
Matthews, R. K. and Mesolella, K. J. (1974):
Quaternary sea level fluctuations on atectonic coast: New 230ThF34U dates fromthe Huon Peninsula, New Guinea. Quaternary Res., vol. 4, p. 185-205.
Dunham, R. J. (1962): Classification of carbonate rocks according to depositional texture.
Amer. Assoc. Petrol. Geol., Memoir 1,
p.108-121.
Hanzawa, S. (1935): Topography and geologyof the Riukiu Islands. Sci. Rep. Tohoku
Univ., 2nd Ser. (Geol.), vol. 17, p. 1----U1.
Harmon, R. S., Ku, T. L., Matthews, R. K. andSmart, P. L. (1979): Limits of U-series
analysis: Phase 1 results of the UraniumSeries Intercomparison Project. Geology,
vol. 7, p. 405-409.
Kataoka, J. (1961): Bryozoan fauna from the"Riukiu Limestone" of Kikai-jima, Kagoshima Prefecture, Japan. Sci. Rep. Tohoku
Univ., 2nd Ser. (Geol.), vol. 32, p. 213-272.
Konishi, K., Schlanger, S. O. and Omura, A(1970): Neotectonic rates in the Central
Ryukyu Islands derived from 230Th coralages. Marine Geol., vol. 9, p. 225-240.
_ , Omura, A and Nakamichi, O. (1974):
Radiometric coral ages and sea level records
from the Late Quaternary reef complexesof the Ryukyu Islands. Proc. 2nd Int. Coral
Reef Symp., vol. 2, p. 595----U13.
Mesolella, K. J. (1968): The uplifted reefs ofBarbados: Physical stratigrphy, facies relationships, and absolute chronology (Ph.
D. dissert.). Providence, R.I., Brown Univ.,
701 pp.
Ota, Y., Machida, H., Hori, N., Konishi, K. andOmura, A (1978): Holocene raised coral
reefs on Kikai-jima (Ryukyu Islands) - Anapproach to Holocene sea level study

122

Akio OMURA

Geogr. Rev. Japan, vol. 51, p. 109-130.
(in Japanese with English abstract)
Yabe, H. and Eguchi, M. (1932): Deep-watercorals from the Riukiu Limestone of Kikaijima, Riukiu Islands. Proc. Imp. Acad.
Tokyo, vol. 8, p. 442-445.

ir.Ji!.~O)!mJ;j(::fiJjl(:B J: I) iiEl±l Lt-:ljif*-Ij- /' ::z·O)1itMiF~: ~Ji!.~O)~fjfki1t!mRIC::fiJjl(:BO) ?~,l:~~O)~t:n~ 650 m· iWilt 40 m O):tm,r!;;:fTi!l)::.7j-;{fii" G t O)li,-t:0)4It&tl¥.JtJ::B;.f:§ (~~a~tJ:Dunham, 1962, O)grainstone) c, eHfO)J:\,'~<O):fillmO).llif*-Ij-/'::z·~iiEi"GcctJ:c-e, il < tJ, I? iE § ~.n -C ~t-::o *liIf~-C"li, -t:.nl? O).ptJ'l? 3:fi11 (Trochocyathus hanzawai,
Micrabacia japonica :f.; J: ry Flabellum rubrum) ~~Iv -e, 230Thj 234 U i*~.:. J: G 1itMiF~
ilItl5EHJtolj., :lJZ~ 82, 000±2, 000 iFO):¥~(j!i:~~t-::o c O)(j!i:li, 1ltJi!.~:tm ({71Jx.lf, l1§1 /' r
Mj~ Barbados ~~=-,,--¥=-7 Huon ~~tJ:c) -Co, -t:O)fftEtJ~li'!lire~.n-CI,'G -!Ili:r",:71C
WJO)iF~ c -3&i" Go-:n, ~llij'O)l(\l\::fiJjl(:Bli, mtE~~mffil~.:.~~i"Gi'iaJ1l(J.lt:.li:O)t~St¥.8C L--C, i"-C"~.:.Iit~~~.n-CI,'G (Konishi et al., 1974)0 i"td?~, ~~Mffilv,:,olj.l?.nGli«\::fiJjl(:GtJ~-Ij-/'::z·li«\c L--C
MSt~.n-CI"t-::~llij', l:iz!l0) grainstone li-t:O)l(\l\litr~;.f:§c L--c:lltmL-t-':tO)c~x.I?.nGo-t: L- -C, cO) grainstone c l(\l\::fiJjl(:€f c O)mtEO)7j-;{fiiWilttfe: (114-144 m) Ii, t L-jiljj~tJ~ c.n i -C"I.:.~:liO)t1U!f)nb (~IHff~JIb) ~? 11"-C f!t-:: c i".nlf, *- J: -t: grainstone 0) :lltftt~1t~jf- L- -C 1" Gel" x. Go U' L-, ~P'I-C"Iit~~ ~;h G ItfilllitJ, I? Jijj:tml¥.JtJ:~mb:i:O)JtI,' t~!t: UJ:
11".n~~I?~ ~~0):lltftt~lttl1Wm~mcm5E~;hGo cO):tt5E.tl, ljif*-Ij-/'~:f.;J:
ry~!RJ"iO)liIf~tJ'l? Yabe and Eguchi (1932) ~ Kataoka (1961) ~.:.J:"'J-C:ti5E ~.nt-::
grainstone O):lltftt~1t c i'JI: L- -C;f ~ L- tJ: I, '0 i t-::, 1:) litr Konishi et al. (1970, 1974) tJ~*
11f L- t-:: 55,000-65,000 iFlitro) Younger Limestone Member of Riukiu Limestone 0)l(\l\i1:-tr/'::z·~.:.1irtr::fiJjl(:BO)7j-;{fi:tm,r!;;:tJ~, cO) grainstone O)7j-;{fi:tmll.iXbli~L-, MStllij'~c:lltftt~
flttJ;3t< iiVJ:G c,l!l:b.nGjiIjj:i!ttJ;W:.li:f~St~c L--Colj.l?.nG c ctJ'l?, l:l1i~~t:nv.:.J1;;tJ;Gi%
It 40 m O):lJZ:§lHili, -$tJ;:lltfttilii-ffiltJ;ffe1ltlID-c";'!; G c ~ x. I? ;h G 0*tt~Ui

123
PROCEEDINGS OF THE PALAEONTOLOGICALSOCIETY OF J AP AN

B *"2i~~!':F~M 131 @]f§lJ~

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K, ~.~*"f:~~.tL~M.~hk~~~

10015)0

A new Carboniferous schizophoriid genus
from the Akiyoshi Limestone Group ..... .
.............................. Yanagida, j.
Ostracode faunas from the Pliocene Ananai
Formation, Shikoku ............ Ishizaki, K.
~m~~~~~~~n~§~.(7)~~~~%~

11 A.

~

M!ff .............................. :pjI~I!i*~(rtliill1:~I;::t~vt 7.> ~% ~M*~~, ~~*~~$~9mGhk~AAB~~1i!I:/t'(!R{t15MI;:"?t,~................. .

.............. *g!:j~::::. tljm,w~· ~m~ifit!W.1:.Jlt1=.11tL.!uJ!&(7) ~/J\~r"'7t;fri I;:"?t'~ (k(7) 2) .................. ~tm fr'.. +t'r1i3*
The Oligocene Series in the island of java,Indonesia ........................ Saito, T.
Additional data on coelenterate affinity ofstromatoporoids .................. Mori, K.
m$7*7~7~~~.(7)~~~a.~~~~{t15 r'm1{:A· ~m~± • *I.gi'lil'l~' <=J:lJlJ1la.ljf\lfj;w))~Mc7)m:<\~I;::t~'rr 7.>:pj:~~......... .

. .. .. ... 'Htmtt::ggl'l~' tT~IlJJ::::l'l~ • ~*~i't;
Turrids from the Cabatuan Formation in Tambac Bay. III Mangellinae and Clavinae ....
................................ Shu to, T.
~tififm: 13 i*i~lKiJ' G(7) !F~~~ {t15ib~llf....

.................................. iWi*~~~mmm~(7)*~n~~~~Mc7)M~mlfr("?
-::i~) ............................ f'l'@~-l'l~Limopsis tokaiensis I;: "?t,~ ...... f'l'@~-l'l~......... .
........................ m~.iIz· flmti!''f*:J:BBlIl!~~fiiJ~(7)JffilJf.t1:.,@,~Jf[

A Middle Triassic Ammonite from Amanatung, Timor .................. Ishibashi, T.
TtfflBlIl!*jj~'fflMgg (7) 7 ~ -'E- ~ -1 ~ Leptoceras (7)fJJAA)1Il:c7)!/'fil& .............. ~)'I.iI#i-t
On jurassic Ammonites from Maktinath,
Nepal ........ Matsumoto, T. and Sakai, H.
Cretaceous ammonites from the leru Formation, Western Papua-New Guinea ..... .
. .. .. ... Skwarko, S.K. and Matsumoto, T.
Three interesting Carboniferous bryozoans
from the Akiyoshi Limestone Group, japan. . . . . . . . . . . . Sakagami, S. and Sugimura, A.

Keijella bisanensis (7)1~

Lt ................................ !'"J$,wB=mtgg~7~'~3~~15t=mtflM(7)~••................................ )JiJlJ*~
Y Metacrinus ~ t Saracrinus kit
I;:"?t,~ .......................... *~j\¥f1:.
gg it Rli gg~ffl{t15 (7) gg tf:\l;: "? t ' ~ ........... .
· ................... lE}f.fm~j\¥f· :ff<~)'I~lHll
ggitRli gg~ffl{t15 (7) ggt±lfli\fi t .~I;: "?t, ~ ..
· ................. jLJlJ~IJJ3' *m1B$ • ~tt m· ll'd~i&1lB • jung, Kyu-Kui. i§#~~~~!W.1:. ~ ~;:J..

Brachyoxylon d. nonakai (Shimakura) fromthe jurasso-Cretaceous Ojika Group ..... .
· . Yamazaki, S., Tsunada, K. and Park, H.S .
On the classification of Xenoxylon Gothan ..
· . Yamazaki, S., Tsunada, K. and Park, H.S.
~::k' ~tififm:i£:BlIl!*cl~E1tilli~ I;:"?t'~, I. -/............................ g§m~)c*J\1(7)-1 ~ 3 ~{t15 ................... .
· ........... *tt~IJJ3' f*l)Jii!iil::kM • *:tt~'f~ lJ ~7<~iJIJ;flM#Il / *fli£:fJI!'fillif<v (7) -fill;: "?
t, ~ ............................ f*l)Ji$(::k?I'illi~#~/

AA·*tt*~·~~)C~·15m~~·~mti&~

Tetracentron fossil leaves from the Plioceneof japan ....................... . Ozaki, K.
Pleistocene pollen and spores from the Shiobara Group in Tochigi Prefecture, japan ..
.................................. Onoe, T.
Taxonomic notes on the diatom genus Denticulopsis . ......................... :J;LJlJ~1JJ3Abundance of Florisphaera profunda (cal.
careous nannoplankton) as a possible indio
cator of sea level change ........ Okada, H.
Distribution of calcareous nannoplankton in
confined waters and marginal seas ..... .
................................ Okada, H.

124
l5L~ ............... ~i§ifl'i\i!i. /UIlB3fbiJit·

m:tN.L1{t:fi': '1".!!!:1't**O)5C~UgnX; ......... .
. .. .. .. .. . .. tKLlIfx· ~B3&±m • i§lJUlt9'l~B3*~ • ::k~1it',Ji:l: • ~t;.lI!.

D'l,1:. Nautilus pompilius O)~O)rJiU~lfiIfftf*Jt~*.=M·~tl~r'F·.~.*M·~ •••r'F. 'Hx m·......... .

. . .. ::kJt}l!"jg· #JJlilll-nX; • !j!:!1J[f¥= • 'hljtm1:.
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...... , ................. ~rm$iEI· 4'~ mJ

New members approved by the Council Meeting heIa on June 18, 1983
Ordinary Members
FUSE, Keisuke; GUNZI, Yukio; HATTORI, Ikuo; IRYU, Yasufumi; JUNG, Kyu-kui;
KANO, Akihiro; MIZUNO, Yoshiaki; NIKO, Shuji; NODA, Yoshikazu; OYAMA, Naomi;
SA TO, Yoichi; SHIMIZU, Katsumi; TAKAGI, Atsushi; TANAKA, Hirokazu; UEDA,
Hitoshi; WATANABE, Akiyasu; YAHAGI, Horoyuki; ZHEN, Bai-Ming

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Transactions and Proceedings of the PalaeontologicalSociety of Japan
New Series No. 130

July 30, 1983

CONTENTS
TRANSACTIONS
760. TABUKI, Ryoichi: Paleoenvironment of the Plio-pleistocene Daishaka formation,
Tsugaru basin, northeast Japan •.•....•..•... . . • . • . . . . . . • • . . . .. 61761. GoTO, Michiharu: Some bivalves from the lower Jurassic Kuruma group fo central
Japan .....•....•.•..••......•...•.............•.....•. 79
762. MATUMOTO, Tatsuro and MURAMOTO, Kikuwo: Cretaceous Nautiloids from Hokkaido - II Part 2. Three Nautiloid Species from the Santonian and Campanianof Hokkaido ...•..••...........•••...•....•............. 85763. FuRUTANI, Hiroshi: Middle Palaeozoic Palaeoscenidiidae (Radiolaria) from Mt.
Yokokura, Shikoku., Japan. Part I .••.•..........•.•...•........ 96764. OMURA, Akio: Uranium-series ages of some solitary corals from the Riukiu Limestone on the Kikai-Jima, Ryukyu Islands .•....••.................. 117
PROCEEDINGS .•..............•.•.•....••.•.....•.•......••..••. 123