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

Itaru HAYAMI and Ikuwo OBATA
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President:

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OBATA

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The fossil on the cover is an adult example (T. TAKAHASHI coil.) of

Mikasaites orbicularis MATSUMOTO (subfamily Marshallitinae, family
Kossmaticeratidae) from the Lower Cenomanian (Cretaceous) of theMikasa area, central Hokkaido. (photo by M. NODA, natural size)

All communications relating to this journal should be addressed to the
PALAEONTOLOGICAL SOCIETY OF JAPAN,
c/o Business Center for Academic Societies,
Yayoi 2-4-16, Bunkyo-ku, Tokyo 113, japan.

Trans. Proc. Palaeont. Soc. Japan, N. S., No. 123, pp. 139-158, pIs. 16-19, September 30, 1981

733.

SILURIAN CORALS FROM THE YOKOKURAYAMAFORMATION IN THE MT. YOKOKURA REG ION,
KOCHI PREFECTURE, SOUTHWEST JAPAN-PART 1. HALYSITIDAE-*HITOSHI NAKAI

Family House Apartment No.7, Shakujii·cho 2-31-27, Nerima·ku, Tokyo 177

Abstract. Eight species of halysitid corals, namely Schedohalysites kitakamiensis(SUGIYAMA), Falsicatenipora shikokuensis NODA and HAMADA, Halysites catenularius(LINNAEUS), H. suessmilchi ETHERIDGE, H. kuraokensis (HAMADA) and three indeterminable species, are described and figured from the Silurian deposits of Mt. Yokokura
region in Kochi Prefecture, Southwest Japan. Among them, Halysites spp. A and B
may represent new forms although they are imperfect in preservation. Halysites
catenularius (LINNAEUS) and H. kuraokensis (HAMADA) ate recorded from Mt. Yokokura region for the first time. Also Silurian geology in Mt. Yokokura region isbriefly described.

in the Silurian of Mt. Yokokura. And
not only halysitids, but also other tabulate
corals, heliolitids and rugose corals are
represented. Although, in general, thestate of preservation of these corals is
not favourable, their diverse feature isquite noteworthy, and they need description. Faunal aspects of corals of the
Silurian of Mt. Yokokura have been briefly
mentioned in KA TO et al. (in press).
The author has been engaged in a
stratigraphical and palaeontological studyof the Silurian of Mt. Yokokura since1976. He wishes to describe in a series of
papers the Silurian coral faunas obtained
from there, in order to grasp biostratigraphical distribution of various corals,
and to make use of them as palaeoenvironmental indicators. In the present
paper only halysitid corals are described
to begin with. Two of them may be new
species and two others are first described

Introduction

Since the discovery of "Halysites" by
YABE and SUGIYAMA (1942) from the
Silurian of Mt. Yokokura region in Shikoku, the area has been geologically investigated by a number of research
workers.
Fossils are abundant at places within
the Silurian there, and they include corals,
molluscs, bryozoan fossils, brachiopods,
trilobites, a graptolite and conodonts. As
for corals, however, only two descriptive
papers (HAMADA, 1956; 1958) are available,
in which four species of halysitid corals
are described; namely Schedohalysites
kitakamiensis (SUGIYAMA), Falsicatenipora
japonica (SUGIYAMA), F. shikokuensis NODAand HAMADA and Halysites siissmilchi
ETHERIDGE. In fact, corals are the mostcommon and conspicuous faunal elements* Received December 17, 1980.

139

Hitoshi NAKAI

140

from Mt. Yokokura region.
All the treated specimens are stored andregistered at the Department of Geology
and Mineralogy, Faculty of Science, Hokkaido University, Sapporo. They carry
numbers with the prefix UHR.
Outline of Geology

Almost vertically dipping Middle Palaeozoic strata are known to develop as ahuge lenticular body within a tectonic
zone called the Kurosegawa Structural
Belt in Mt. Yokokura region (Text-fig. 1).
A conformable succession from the Silurian
to Devonian was termed as the Yokokurayama Formation by SUYARI (1961), in
which HAMADA (1958) further recognized

four beds (=members), namely GJ, G2 , G3
and G4 in ascending order (Text-fig. 3).
The G1 member is about 250 m thick,consists of the alternation of acidic tuff,
tuffaceous sandstone and slate. Two thickbeds of welded tuff are intercalated in
the member. Fossils occur in the middle
part of G1 member. Brachiopods, trilobites and some moulds of rugose corals
have been obtained.
The Gz member is only 90 m thick, consists mainly of the thin alternation of tuffaceous sandstone and slate. In the lower
part of the member several thin beds ofacidic tuff are intercalated. While themember becomes calcareous in the upper
part where thin beds of impure limestoneor sandy limestone are intercalated. Fos-

9<:>oText·fig. 1.

1km

8 --,-

Simplified geological map of Mt. Yokokura region and showing the
mapped area (Text-fig. 2).
1: Terano Metamorphic Rocks, 2: Mitaki Granitic Rocks, 3: Yokokurayama
Formation, 4: Ochi Formation, 5: Upper Palaeozoic Strata, 6: Cretaceous
deposits, 7: serpentinite, 8: fault, 9: mapped area (see Text.fig. 2)

733.

Silurian halysitids from Mt. Yokokurasils are abundantly found in these calcareous strata. Halysitids, other tabulate
corals, heliolitids, rugose corals, stromatoporoids, brachiopods, trilobites and conodonts have been known to occur in themember.
The Ga member is 200 m thick at most,- we.

consists almost entirely of gray or pinkish
gray, massive limestone partly conglomeratic. Thin beds of fine-grained, redtuff are known to intercalate at places.
Fossils of halysitids, other tabulate corals,heliolitids, rugose corals, stromatoporoids,
brachiopods, molluscs, a graptolite, trilo-o'i--===--==:::::i200m

11; +161 A 661

o

71 °00 I

3\·.·1 81~::'~: 141

I 9 'Z..

51 ),/···.)1
Text-fig. 2.

141)

Geological sketch map of the eastern part of Mt. Yokokura
showing fossil localities.
1: :VIitaki Granitic Rocks, 2-8: Yokokurayama Formation (2: Acidic tuff,
3: Welded tuff, 4: Tuffaceous slate, 5: Tuffaceous sandstone, 6: Impure
limestone, 7: Limestone conglomerate, 8: \'\assive limestone) 9: Strikeand dip

Hitoshi NAKAI

142

bites and conodonts are commonly found.
The G4 member is more than 900 m
thick, consists of fine acidic tuff, lapilli
tuff and tuff breccia in alternation. Rhyolite lavas and beds of sandstone and slate
are occasionally intercalated in the se-

1\1\~Loc.C~Loc.B

t833
1<?:(~:14

~5

~6

G,

t!m7
~8

Text-fig. 3. Composite geological colu·
mnar section of the Yokokurayama Formation showing fossil horizons in the easternpart of Mt. Yokokura (Text-fig. 2).
1: Fine acidic tuff, 2: Coarse acidic tuff,
3: Welded tuff, 4: Tuffaceous sandstone,
5: Tuffaceous slate, 6: Pinkish gray, massive limestone, partly conglomeratic, 7: Dark
gray, conglomeratic, impure limestone, 8:
Greenish gray, sandy, impure limestone orlimy sandstonequence. No fossils have been obtained.
Kuw ANO (1976) suggested by his conodont research that the lower part of G2
is Llandoverian, the upper part of G2 andthe lower part of Ga belong to Wenlockian, while the rest of Ga member would
be Ludlovian in age.
The Silurian corals treated in the present study were collected from the four
localities, A, B, C and D in Mt. Yokokura
region (Text-fig. 2).
Locality A is a quarry called the Gomi
where the top G2 member and the lower
and middle part of Ga member are exposed (Text-figs. 2,3). Fossils were mostly
collected as scree specimens derived fromthe Ga member. Schedohalysites kitakamiensis (SUGIYAMA), S. sp., Halysites suessmilchi ETHERIDGE, H. sp. A and H. sp.
B were collected together with othertabulate corals, heliolitids, rugose corals,
stromatoporoids, molluscs, brachiopods,
trilobites and conodonts.
Locality B is an outcrop along the upper
tributary of Shiroishisawa valley where
the middle part of G2 member is exposed.
Falsicatenipora shikokuensis NODA and HAMADA, Halysites catenularius (LINNAEUS),
H. kuraokensis (HAMADA) and H. kuraokensis (HAMADA) variety were collected
together with other tabulate corals, heliolitids and rugose corals. Fossils are mostly
found abraded within limestone matrix
which is sandy.
Locality C is a small outcrop also in theupper stream of the Shiroishisawa valley,
where the top part of G2 member is exposed. Impure limestone is conglomeratic
in parts. The following fossils were obtained. Falsicatenipora shikokuensis NODAand HAMADA and F. shikokuensis NODAand HAMADA variety together with othertabulate corals, heliolitids, rugose corals,
stromatoporoids, brachiopods and trilobites.
In most coral specimens corallum shape isfairly well preserved within muddy matrix.

733.

Silurian halysitids from Mt. Yolcolcum

Although branches are often broken infasciculate forms, their surface characters
are preserved in detail. Before burial
corals must have been transported to fossilized position but only a small distancefrom where they grew.
Locality D is along the narrow mountain path on the northern slope of Mt.
Yokokura, where the top part of Gz member and the lower to middle part of Ga
member are exposed. The following fossils were collected from the lower part of
Ga member. Schedohalysites kitakamiensis(SUGIY AMA) together with other tabulate
corals, heliolitids and rugose corals. Actually gray coloured fossils are firmly
embedded in white-gray, massive limestone, so that habits are difficult toobserve in field.

Systematic description
Family Halysitidae MILNE-EDWARDS
and HAl ME, 1850
Suprageneric and generic classificationof chain corals by HAMADA (1957b, c;1958) is largely adopted in the following
description. Morphological terms are thosedefined by HAMADA (1957a, b, c; 1958),
and the evaluation of taxonomic weight
for each morphological character is after
KAWAMURA (1980).
Since fossils treated below were firmly
embedded in matrix, and were collected
as large or small fragments, it was usuallydifficult to know external features of corals.
Corals were also often strongly recrystallized and were sometimes crushed, so thenature of septal spinules or the nature ofwalls are usually not readily recognized.
The shape and size of corallum, surface
characters of corallites, for instance, cannot be ascertained with confidence as thepresent study has been made in thin sections. In some instances septal spinules

143

may have been obliterated by recrystallization, yet in other cases intergrowth of
sparry calcite will give an impression that
septal spinules are genuinely present insome forms.
So in the following description, thepresence or absence of micro- and/or
mesocorallites and the form and size ofmacrocorallites are considered to be themost important biocharacters in classifying halysitids.
As to the size of macrocorallites, halysitids in general may be grouped into 3
categories, namely large, intermediate andsmall ones. Large macrocorallites are over
2 mm in short diameter, intermediate ones
are around 1.5 mm, while small ones areless 1 mm. In the following description
the size of macrocorallites is referred in
the way herein described.
Subfamily Schedohalysitinae
HAMADA, 1957
Relilarks.- Two genera, Schedohalysites
and Falsicatenipora, have been placed
within the subfamily Schedohalysitinae.
The distinction between the above mentioned two genera is whether microcorallites are present or not. Mesocorallites
are present but sometimes not present inboth genera. It is noteworthy that thecharacter of septal spinules, whether they
are present or not, has not been taken
into account in the generic classificationof the subfamily Schedohalysitinae, inspite that the character has been employed
as important in the subfamilies Cateniporinae and Halysitinae.
The problem is that in a corallites ofHalysites Japonicus, the type species ofFalsicatenipora, a microcorallite does seem
present. See plate XVI, fig. 2 of SUGIYAMA (1940). Falscicatenipora Japonica,
illustrated from Gion-yama by HAMADA
in 1958 (pI. VI, fig. 1) clearly indicates144

Hitoshi N AKA!

the presence of microcorallites. In otherwords, it would be rather difficult to distinguish Falsicatenipora from Schedohalysites as far as their type species are concerned, although the author admits that
there is a group of schedohalysitids which
certainly has no microcorallites (e. g.
Halysites chillagoensis ETHERIDGE). Until
all the type materials for both genera arethoroughly restudied, the author provisionally followed the classification set by
HAMADA.
Genus Falsicatenipora HAMADA, 1958
1958. Falsicatenipora HAMADA, jour. Fac. Sci.,
Univ. Tokyo, ser. 2, vol. 11, p. 98.
Type species :-Halysites japonicus SUGIYAMA,
1940.

Remarks.-The following forms of Falsicatenipora have been described until now,
apart from the species assigned to thegenus by HAMADA (1958).
Falsicatenipora chillagoensis (ETHERIDGE):
STRUSZ, 1961
F. dazhubaensis LIN and YEI-I: LIN, 1975
F. shanxiensis LIN: LIN, 1975
F. wangjiawaensis LIN: LIN, 1975
F. shikokuensis NODA and HAMADA: KAWAMURA, 1980
F. sp. indet: KAWAMURA, 1980

Judged from figures, microcorallites arecertainly present in some specimens of
F. shikokuensis (HAMADA, 1958, pI. 7, fig.
6), F. dazhubaensis (LIN, 1975, pI. 57, fig.
2a), F. shanxiensis (pI. 70, fig. 1a) and F.
wangjiawaensis (pI. 70, fig. 2a). By definition all such forms should be classified
into the genus Schedohalysites. See remarks of the subfamily Schedohalysitinae.
Falsicatenipora shikokuensis NODAand HAMADA

PI. 16, Figs. 2-4; PI. 17, Fig. 3;
Text-fig. 4b
1958. Falsicatenipora shikokuensis NODA andHAMADA, in HAMADA, jour. Fac. Sci.,
Univ. Tokyo, ser. 2, vol. 11, p. 99-100,
pI. 6, figs. 4-5; pI. 7, figs. 1-7.
1980. Falsicatenipora shikokuensis: KAWAMURA, jour. Fac. Sci., Hokkaido Univ.,
ser. 4, vol. 19, no. 3, p. 280, text-fig.
5a, pI. 1. figs. 1-2.

Materials:- Twelve thin sections (UHR
30440a, c; 30445; 30451-30457) were prepared from ten colonies. Eight of themwere collected from the upper part of theG2 member of the Yokokurayama Formation, at Loc. C and two of them (UHR
30440, 30445) were collected from the
middle part of the G2 member, at Loc. B.
Description :-Corallum compound, cateniform but subcylindrical as a whole,and very small in size. Average corallum is about lOx 15 mm in width and 20
to 25 mm in height.
In transverse section fenestrules arecharacteristically small and polygonal but
their size and shape is variable. Fenestrules may be triangular, quadrangular,pentagonal, hexagonal or partly moreelongated in shape, the size of which
varies from 0.5 X 0.75 mm to 2.0 X 2.7 mm
in width. One side of each fenestruleconsists usually of only one, rarely two
macrocorallite. New macrocorallite occurs
at a free end of macrocorallite or at thejunction of chains. Macrocorallites are
small, sub-rectangular or suboval, barrel
shaped in transverse section. External
diameter of them is 0.4-0.6 mm in shortside, while it is 0.8-1.0 mm in long side.
Corallite wall is thin, being 0.1-0.15 mm
in thickness. Wall between corallites issomewhat thinner than those of outerwall. Under the microscope wall is uniform, composed of light coloured, fibrouslayer. One or two septal spinules are733.

Silurian halysitids from Mt. Yokokura

occasionally seen in some corallites, but
the presence of which is Quite certain,
because of the presence of fine dotts representing the axial ends of them in longitudinal sections. Mesocorallites are normally present, but are lacking in somechains. They are triangular or tetragonalin shape, and are 0.3-0.5 mm in the lengthof one side. They occasionally becomeas large as the size of smaller macrocorallites. Microcorallites are usually absent,
but in only one section (UHR30453, PI. 16,
Fig. 2; Text-fig. 4b) microcorallites areseen to develop.
In longitudinal section corallites arearranged in somewhat divergently. Tabulae in macrocorallites and mesocorallites
are complete and horizontal, or slightly
concave downwards. In macrocorallites
the vertical distance between adjacenttabulae is 0.3 to 0.45 mm. Tabulae inmesocorallites are more closely spaced
than those in macrocorallites. Axial cut
edges of septal spinules are to be seen
between tabulae as dotts arranged inthree or four vertical rows. These dotts
do appear to be horizontally lined but
somewhat irregularly.
Remarks:- The above description isbased on the specimens collected fromlocality C. They are much better preserved than the type materials of Falsicatenipora shikokuensis NODA and HAMADA in HAMADA (1958), and are only slightly different especially from the holotype.
The holotype of F. shikokuensis has closely
set tabulae in longitudinal section, while
the paratype and the specimen from Loc.
C reveal comparatively coarse tabulae.
Otherwise all the specimens mentioned
above show subcylindrical corallum, small,
polygonal fenestrules composed of one or
two, small, suboval macrocorallites. They
are thus specifically identical.
Two specimens from Loc. B are badly
recrystallized. They are similar to HA-

145

MADA'S material of F. shikokuensis (HAMADA, 1958, pI. 6, fig. 4; pI. 7, fig. 1) ingeneral appearance. Therefore they areprovisionally placed here under the same
category with F. shikokuensis, although
there remains uncertainty in the recognition of internal characters in detail as forthese two specimens.
A specimen of Falsicatenipora shikokuensis from the Kitakami Mountains
studied by KAWAMURA (1980) has a little
thicker wall compared to the specimensfrom Southwest Japan. The specimen isbadly crushed and recrystallized. Falsicatenipora hillae HAMADA (=Halysites cfr.
australis of HILL, 1954, p. 39, pI. 4, figs.
Sa-b) resembles F. shilwlmensis in general,but the former has slightly larger andmore rectangularly formed macrocorallites
compared to the latter. Falsicatenipora
dazhubaensis (LIN, 1975) Quite resembles
F. shilwkuensis in the form of fenestrules,
but possesses much larger macrocorallites
compared to the latter form. FalsicatenijJora sp. of KAWAMURA (1980, p. 280-2S1,
pI. 1, fig. 3; text-fig. 5b) also resembles
F. shikokuensis in general appearance, but
has large corallites. Falsicatenipora chillagoensis (ETHERIDGE, 1904; STRUSZ, 1961),
F. shamveiensis (LIN, 1975) and, F. wangjiau'aensis (LIN, 1975) and possibly F.
japonica (SUGIYAMA, 1940; HAMADA, 1958)
reveal a little elongate and somewhat
meandrine fenestrules and have large
macrocorallites. So they are readily distinguished from F. shikokuensis.
Falsicatenipora shikokuen~is NODAand HAMADA variety
PI. 16, Fig. 1

Material :-Only one specimen (UHR
30450) from the upper part of the Yokokurayama Formation, at Loc. C.
Remarks :-Compared to the above des-146

Hitoshi NAKAI

cribed specimens of Falsicatenipora shikokuensis, the present form reveals a little
smaller corallum which appears to behemispherical rather than cylindrical.
The size of fenestrules (0.7x1.6 to LOx
2.3 mm) and macrocorallites (0.45-0.5X
0.65-0.75 mm) is also smaller than that in
the above described specimens. Microcorallites are absent. Otherwise the present
specimen is quite identical with F. shiko/wensis, of which it must be a small
variety. The only comparable form ofschedohalysitids with the present variety
is Schedohalysites yarrangobillyensis HAMADA (=Halysites cfr. lithostrotionoides of
HILL, 1954, p. 38-39, pI. 4, figs. 6a-b) as
far as the size of fenestrules and macrocorallites are concerned. But this Australian form is provided with almost rectangular macrocorallites and distinct
microcorallites according to description(HILL. 1954, p. 39). Also fenestrules may
become irregular in S. yarrangobillyensis,
while they are polygonal in the present
variety. F. shikokuensis and S. yarrangobillyensis are thus easily distinguishable.
Genus Schedohalysites HAMADA, 1957
1957. Schedohalysites HAMADA, jour. Fac. Sci.,
Univ. Tokyo, ser. 2, vol. 10, p. 401.
Type species :-Halysites orthopteroides ETIIERIDGE, 1904.

Remarks.-After the review of halysitids by HAMADA (1957b, c) the genus
Schedohalysites has been described by
STRUSZ (1961) and MIRONOVA (1965).
Schedohalysites laxus is introduced by
MIRONOVA (1965) from the Ludlovian of
Salair. For discussion on the genus see
the above remarks on the subfamily
Schedohalysitinae and on the genus
Falsicatenipora.
Schedohalysites kitakamiensis (SUGIYAMA)

PI. 17, Figs. 1-2; PI. 19, Fig. 1;
Text-fig. 4a1940. Halysites kitakamiensis SUGIYAMA, Sci.
Rep. Tohoku Imp. Uuiv., second ser.,vol. 21, p. 129-131, pI. 27 (15), figs. 4-9;
pI. 28(16), figs. 3-8; pI. 30(18), fig. 14;
text-fig. 6.
1956. Halysites kitakamiensis: HAMADA,japan.
jour. Ceol. Ceogr., vol. 27, p. 134-140,
pI. 9, figs. 1-6; text-fig. l.
1958. Schedohalysites kitakamiensis: HAMADA,
jour. Fac. Sci., Univ. Tokyo, ser. 2, vol.
11, p. 100-101, pI. 6, fig. 3; pI. 8, figs.
4-5.

Materials.- Ten thin sections (UHR
30458-30461, 30464, 30466) have been prepared from six colonies from the G3 limestone of the Yokokurayama Formation.
One sample (UHR30458) was collected at
Loc. D and the other at Loc. A.
Description.-Corallum is compound,
cateniform, irregular in shape, varies in
size.
The largest specimen obtainedshows block like appearance, and is 50x
60 mm in width with the height of 40 mm.
Other surface characters are unkown.
In transverse section fenestrules are
typically pentagonal or hexagonal in shape.
They are about 2.3x2.5 mm to 3.2x4.5
mm in size, the average being 2.5 X 3.0 mm.
However they may be irregular or open
where free, straight or curved chains arepresent. Each chain consists of one or
two macrocorallites in polygonal fenestrules. But in one fragmental corallum(UHR30446) as many as 12 macrocorallites
are observed in a single chain. Macrocorallites are small, slender, subrectangularor elongated oval in shape. Their external
size measures 0.6-0.7 mm X 1.0-1.3 mm.
Corallite wall is thin, being 0.1 mm at thecentre of its lateral side, but is thickened
towards the junction between two neighbouring corallites giving the externalsurface of a chain only a little crenulated.
Two or three, very short septal spinules

733.

Silurian halysitids from Mt. Yokoknra

are seen in some corallites (Text-fig. 4a).
Mesocorallites are usually present at thejunction of chains of corallites. They aretriangular, or partly tetragonal, being 0.3
to 0.4 mm long on one side of mesocorallite. Microcorallites are present, but they
are happened to be rather occasional in a
specimen herein illustrated (PI. 17, Fig. 1 ;Text-fig. 4a). The development of microcorallites is therefore variable. They areusually in slit form, and are 0.2 X 0.3 or
0.1 X 0.3 mm in size.
In longitudinal section macrocorallites
are arranged parallel with each other.
Tabulae in macrocorallites are complete
and horizontal. Ten to twelve tabulae arecounted in a vertical distance of 5 mm.
In mesocorallites more densely arranged
tabulae are seen. For microcorallites nosuitable oriented thin sections to reveal
tabulae are obtained. Secondary grownsparry calcite crystals often mask the true
nature of tabulae and septal spinules, thelatter of which are however definitely
seen as dot like cut edges in some corallites. True tabulae are observed as thindark lines of about 0.02 mm thick between
interspaces filled with sparry calcite.
Remarlzs:- The specimens treated here
are quite identical with Schedohalysites
kitakamiensis described and figured by
SUGIY AMA (1940) and HAMADA (1956, 1958),
apart from that the microcorallites areless well developed in the present specimens. See HAMADA (1956) for specificcomparison amongst various forms of
Schedohalysites. Schedohalysites laxus MIRONOVA (1965, p. 135, pI. 32, figs. la-b)
is clearly distinguishable from S. kitakamiensis in having much larger and oval
macrocorallites compared to the latter
species.
Schedohalysites sp.
PI. 16, Fig. 5; Text-fig. 4d

147

Material :-Single thin section (UHR
30462) collected from the G3 member of
the Yokokurayama Formation, at Loc. A.
Description :-Because of the imperfectnature of the specimen, the shape andsurface characters of corallum are unknown. Corallum is small, measures 20 X
30 mm in width as far as it is preserved.
Fenestrules are irregular in shape andsize. Although fragmentally preserved,
they are usually tetragonal or pentagonal,
from 0.75 X 1.5 mm to 4.3 X 5.0 mm in size,
but sometimes make imperfect fenestrules.
Each side of fenestrules is composed of
one or two macrocorallites. !'vIacrocorallites are rectangular or elongated oval inshape. Size of them measures 0.75-0.95
X 1.25-1.5 mm. Corallite wall is originallythin (about 0.1 mm), but partly thickened,
being about 0.3 mm. They are thin at thecentre of macrocorallites and are thickened
at the junctions of two corallites, so thatthe surface of corallite chains seems somewhat smooth. No definite septal spinules
are observed, but short, spinule like projections are occasionally seen on the innersurface of some macrocorallites. Mesocorallites are usually developed but sometimes lacking, when macrocorallites directly contact with each other. Mesocorallites are triangular in shape, 0.5-0.7 mm
in length of each side. l'vlicrocorallites
are partly developed (Text-fig. 4d), tetragonal and being 0.25 X 0.6 mm in size. Wallbetween corallites are divisible into threelayers. At the centre of that wall darkcoloured very thin layer (0.03-0.05 mm inthickness) is observed and then lightcoloured, fibrous, rather thick layers aredeveloped at both sides of the dark layer.
Corallite wall is 0.1-0.3 mm in thickness.
No longitudinal section is observed.
Remarks :-Although fragmentally preserved the present specimen belongs to
the genus Schedohalysites, because of its
definite possession of microcorallites. It

148

Hitoshi NAKAI·····f····

~M'-"
e.

.~ni:;':~'~':i({i';~~i{i(;....
... -....-..
~, ~ ." ,~.

-

--~

9.-

• 'i' <.

"~:af"~/" __ y_::.'e.....".. .,./

Text-fig. 4. Diagrams of halysitid corals collected from the Silurian of Mt. Yokokura region
showing such characteristic features appeared in transverse sections as the shape of fenestrules.
as the presence or absence of micro- and/or mesocorallites and septal spinules. and as "Balken"
like structure in some forms.
a: Schedohalysites kitakamiensis (SUGIYAMA) (UHR30460a)
b: Falsicatenipora shikokuensis NODA and HAMADA (UHR30453)
c: Halysites catenularius (LINNAEUS) (UHR30439a)
d: Schedohalysites sp. (UHR30462)
e: Halysites sp. B (UHR30467)
f: Halysites kuraokensis (HAMADA) (UHR30441a)
g: Halysites sp. A (UHR30464)
h: Halhsites suessmilchi ETHERIDGE (UHR30463a)
Black bar represents 1 mm.

733.

Silurian halysitids from Mt. Yokokura

is similar to Schedohalysites kitakamiensis
in general appearance. However it is distinguishable from the latter because of
having larger corallites. In the shape andsize of macrocorallites and fenestrules thepresent form closely resembles Falsicatenipora japonica (SUGIYAMA). Especiallythe specimen of F. japonica (SUGIYAMA)
figured by HAMADA (1958, pI. 6, fig. 1)
from the Kuraoka district rather closely
resembles the present form even in having occasional microcorallites. Microcorallites are said to be absent in theoriginal description of Halysites japonicus
by SUGIYAMA (1940, p. 131), but thischaracter has to be further confirmed bya restudy of original specimens. If microcorallites are proved to be present in thetype materials of Halysites japonicus.
Falsicatenipora based on Halysites japonicus would be considered as a juniorsynonym of Schedohalysites. The present
specimen together with other identicalforms may be called as S. japonicus. Thereis even a possibility that the nature of
microcorallites is so variable in Schedohalysites that the presence or absence ofthem cannot be taken as a reliable distinguishing character between genera.

Subfamily Halysitinae MILNE-EDWARDS
and HAl ME, 1850
Genus Halysites FISCHER von
W ALDHAIM, 1813
1940. Halysites: SCGIYAMA, Sci. Rep. Tohoku
Imp. Univ., second ser., vol. 21, p. 129.
(partim)1954. Halysites: HILL, Bull. Comm. Austr.,

Dept. Nat. Develop., Bureau Min.
Resour., Ceol. Ceophy., no. 23, p. 3738.
1954. Halysites:

THo~!AS and SMITH, Ann.
Mag. Nat. Hist., ser. 12, vol. 7, p. 766.
1955. Halysites: BCHELER, Bull. Peabody Mus.

149

Nat. Hist., no. 8, p. 21-22.
1956. Halysites: HILL and STUMM, Treatiseon Invertebrate Paleontology, part F, F.
469.
1957. Halysites: HA~'IADA, Jour. Fac. Sci.,
Univ. Tokyo, ser. 2, vol. 10, p. 402.
1957. Acanthohalysites HAMADA, Jour. Fac.
Sci., Univ. Tokyo, ser. 2, vol. 10, p. 402.
1961. Acanthohalysites: STRUSZ, Palaeontology, vol. 4, p. 353.
1962. Halysites (Acanthohalysites) Yu, "Geology of Chi-len-shan", p. 80.
1966. Halysites: KLAA~!ANN, "Incommunicate
Tabulata of Estonia", p. 59-60.
1967. Halysites: STAS!1':SKA, Palaeontologia
Polonica, vol. 18, p. 57.
1971. Acanthohalysites: SCRUTTON, Bull. British. Mus. (Nat. Hist.), geol., vol. 20,
p. 221.
1972. Halysites: LELES!IUS, "Silurian Tabulata
from Turkestan", p. 51.
1977. Halysites: JIA and Wu, "Palaeontologicalatlas of Central-South China", part 1, p.
23-24.
1978. Halysites: YA);G, KIM and CHO\,', "Palaeontological atlas of Southwest China,
Guizhou Volume", part 1, p. 228.
Type species:- Tubipora catenularius LIKNAEUS, 1767.

Remarks:- Within the subfamily Halysitinae, HAMADA (1957b) distinguishes thegenus AcanthohalY3ites from the genus
Halysites (s. str.) for cateniform species
with horizontal tabulae and septal spinules.
In other words he places taxonomic importance in the character whether septal
spinules are present or not in the classification of Halysitinae. However HAMADA(1958) pays little attention to this natureof septal spinules in the classification of
Schedohalysitinae. As discussed recently
by KAWAMURA (1980), it is still veryquestionable whether the character of
septal spinules is important as genericcriterion or not. For example in AcanHAMADA thethohalysites kuraokensis
degree of development of septal spinules

150

Hitoshi NAKAI

varies from individual corallite to theother, and from a colony to another. In
some corallites 4 or 5 long septal spinules
are present on one side of macrocorallites,
while one or two short spinules are only
to be seen in another corallites. The
author agree with KAWAMURA (1980) as
long as the nature of septal spinules isnever a stable biocharacter at least in thesubfamily Halysitinae. The genus Acanthohalysites is therefore considered here
as a junior synonym of Halysites.
Halysites catellularius (LINNAEUS)
PI. 16, Fig. 4; PI. 19, Figs. 2-3;
Text-fig. 4c

1954. Halysites catenularius: THOMAS and
SMITH, Ann. Mag. Nat. Hist., ser. 12,
vol. 7, p. 766-768, pI. 20, figs. la-c.
1955. Halysites catenularius: BUEHLER, Bull.
Peabody Mus. Nat. Hist., no. 8, p. 2425, 28-29.
non 1956. Halysites catenularius: STEARN,
Mem. Ceol. Surv. Canada, no. 281, p. 71.
1962. Halysites sp. cfr. H. catenularius, lULL,
Jour. Alberta Soc. Petroleum Ceol., vol.
10, no. 6, p. 327, fig. I-I.
1962. Halysites catenularius: FLUGEL, Jb.
Ceol. B. A., Bd. 105, s.316-317, taf. 22,
fig. 4.

Materials:- Twelve thin sections (UHR
30435-30440) are prepared from six colonies, from the middle part of the G2

member of the Yokokurayama Formation.
They are collected at Loc. B.
Description :-Corallum is compound,
cateniform, thick tabular or block like inshape. Specimens at hand are reletively
small, being 15-20x30-40 mm in widthand 10-15 mm in height. No external
characters are observed.
In transverse section fenestrules areusually labyrinthine (PI. 19, Fig. 2), but ina corallum they are more compressed
polygonal in shape (PI. 16, Fig. 4). A
few selected fenestrules measure 2.0 X 4.5,
1.5 X 12.0, 6.0 X 9.5 mm, etc. Each chain iscomposed of one to five (maximum 7)
macrocorallites. Macrocorallites are usually roundish oval or subcircular, and intermediate in size, being 1.45-1.85 X 1.52.0 mm. A verage external size is 1.6 X
1.75 mm. The size of visceral chamber is
1.1 X 1.4 mm. JUdging from calice ofmacrocorallite, which is filled with matrix,
inner side of macrocorallite wall is almost
smooth but very short spiny projections
are partly developed on that inner wall
(PI. 19, Fig. 2; Text-fig. 4c). Wall ismoderately thick, about 0.3 mm, but isrecrystallized in many corallites. Mesocorallites may be triangular or tetragonal,
0.3-0.6 mm in length in each side. Microcorallites are rectangular or slit like, 0.20.3 X 0.3-0.4 mm in size. External wall of
microcorallites and wall between microor mesocorallites and macrocorallites are

Explanation of Plate 16
Fig. 1. Falsicatenipora shikokuensis NODA and HAMADA variety
Transverse and partly oblique section (UHR30450a), Loc. C, x 5.
Figs. 2-3. Falsicatenipora shikokuensis NODA and HAMADA
2: Transverse section (UHR30453), Loc. C, x 5.
3: Longitudinal section (UHR30455), Loc. C, x 5.
Fig. 4. Halysites catenularius (LINNAEUS) and Falsicatenipora shikokuensis NODA and HAMADA
in limy sandstone matrix. Transverse section (UHR30440a), Loc. B, x 2.
Fig. 5. Schedohalysites sp.
Transverse section (UHR30462), Loc. A, x 5.

NAKAI:

Silurian Halysitids

Plate 16

733.

Silurian halysitids from Mt. Yokokum

somewhat thinner than that of macrocorallites and is 0.1-0.2 mm in thickness.
In longitudinal section tabulae in macrocorallites are complete and horizontal orslightly convex, 12-14 in number in a
vertical distance of 5 mm. Tabulae inmicrocorallites or mesocorallites are also
complete and horizontal. They are almost
equally developed with those of macrocorallites, being 12-15 in 5 mm. Septal
spinule like black dots are observable insome macrocorallites, but definite septal
spinules are not discovered.
Remarks :-Specimens from the Yokokurayama region are here assigned to
Halysites catenularius, although they reveal
thick corallite wall and less pronounced
labyrinthine in the shape of fenestrules
compared to the neotype of H. catenulariuschosen by THOMAS and SMITH (1954).
Otherwise they are quite identical with
H. catenularius. H. catenularius of STEARN(1956) is, according to his description,
provided with 12 rows of septal spinules,
flexuous tabulae and large macrocorallites.
STEARN'S form is definitely not assignable
to H. catenularius, but may be close to
Halysites agglomeratus. H. sp. cfr. H.
catenularius figured by JULL (1962) closely
resembles the present Japanese form, except that the shape of microcorallites in
the Canadian form is more elongated.
Probably the Canadian form is included
in broadly defined group of H. catenularius, to which H. catenularius of FLDGEL(1962) from Iran also belongs.
Halysites suessmilchi ETHERIDGE
PI. 17, Fig. 5; PI. 18, Figs. 3-4;
Text.fig. 4h
1904. Halysites siissmilchi ETHERIDGE, Mem.
Ceol. Surv., New South Wales, Palaeont.,
no. 13, pt. 1, p. 26-27, pI. 3, figs. 3-4;
pI. 7, figs. 1-3.

151

1955. Halysites siissmilchi: BUEHLER, PeabodyMus. Nat. Hist., no. 8, p. 52-53.
1958. Halysites siissmilchi: HAlvIADA, Jour.
Fac. Sci., Univ. Tokyo, ser. 2, vol. 11,
p. 102-103, pI. 9, figs. 1-4.
1962. Halysites sp. cfr. H. siissmilchi: JULL,
Jour. Alberta Soc. Petroleum Ceol., vol.
10, no. 6, p. 327, fig. 1- J.

Material :-Four thin sections preparedfrom only one colony (UHR30463a-d) collected from Gs limestone of the Yokokurayama Formation, at Loc. A.
Description :-Corallum compound, cateniform, thick tabular in form, measuresabout 30 X 50 mm in width and 20 mm inheight as far as it is preserved. Surface
characters are unknown.
In transverse section fenestrules are
irregular, mainly labyrinthine, but partly
polygonal. They vary in size from 1.5 X
3.3 mm to 2.0x 18.0 mm (PI. 17, Fig. 5).
Short side of fenestrules is composed ofusually one or two macrocorallites andlong side of fenestrules is composed of
two or three macrocorallites in polygonal
type. A single chain in labyrinthinefenestrules may be composed of as manyas 12 macrocorallites. Macrocorallites areelongated oval or elliptical, sometimes
nearly circular in shape, being 0.6-0.85 X
0.65-1.05 mm in external size. Corallite
wall is originally thin, 0.1-0.15 mm thick.
Although usually recrystallized, microcorallites are well developed, characteristically small, rectangular, being about 0.2
mm in length on each side. Mesocorallites
are always triangular, being 0.3-0.4 mm indiameter. Corallite wall is usually recrystallized and much thickened. Therefore
characters of inner side of wall are poorly
preserved. judging from some less recrystallized macrocorallites, inner side ofcorallite wall is usually smooth, besides
septal spinule like undulation may bepresent in few corallites (Text-fig. 4h).
In longitudinal section tabulae in macro-

152

Hitoshi NAKAI

corallites are complete and horizontal,
sometimes only slightly convex upwards.
Fourteen to seventeen tabulae are counted
in a vertical distance of 5 mm. Only one
longitudinal section of a microcorallite ora mesocorallite is available, in whichtabulae are horizontal and spaced equallywith those of macrocorallites.
Remarks:-The present from is quite
identical with the Australian Halysites
suessmilchi ETHERIDGE in having labyrinthine fenestrules with small, oval macrocorallites possessing no septal spinules.
However it is different from the Australian material provided with smaller corallites. The same species has been described from the Yokokurayama region by
HAMADA (1958), and that is provided withmacrocorallites whose size ranges justbetween the figures of the Australian
form and those of the present one. HAMADA'S form (pI. 9, fig. 1) is more labyrinthine than the present form and theAustralian one. In vertical section thenature of tabulae of the present form
closely resembles that of the Australianform. Therefore except for size differences the present form stands much closer
to the Australian form than to HAMADA'S
form.
Halysites sp. cfr. H. siissmilchi of JULL
(1962) is very close to and is in fact identical with H. suessmilchi ETHERIDGE especially with the present Japanese form.

Halysites bellulus HAMADA (1958) issimilar to the present form in the sizeand shape of macrocorallites. However it
has polygonal fenestrules compared torather meandrine fenestrules of the present
specimen. Halysites tenuis HAMADA (1958)
differs from H. suessmilchi in having
small, rectangular macrocorallites andsomewhat irregularly shaped fenestrules.
Halysites arisuensis KAW AMURA (1980)
closely resembles H. suessmilchi at a glance,
but is distinguished from the latter by
him only in having small and less oval
macrocorallites. Feature of fenestrules ofthe present specimen does not differ considerably from that of H. arisuensis. If
intraspecific variation should be recognized rather broadly in H. suessmilchi, H.
arisuensis would fall within the categoryof H. suessmilchi.
Halysites kuraokensis (HAMADA)
PI. 3, Figs. 1-2; Text-fig. 4f
1954. Halysites sp. HILL, Bull. Comm. Austr.,
Dept. Nat. Develop., Bereau Min. Resour.,Geol. Geophy., no. 23, p. 39, pI. 4, fig. 9.
1958. Acanthohalysites kuraokensis HA'vIADA,
Jour. Fac. Sci., Univ. Tokyo, ser. 2, vol.
11, p. 101, pI. 8, figs. 1-3.

Material :-Eleven thin sections (UHR
30441-30443, 30446-30449) are preparedfrom seven small colonies collected from

Explanation of Plate 17
Figs. 1-2. Schedohalysites kitakamiensis (SGGIYAlvIA)
1: Transverse section (UHR30460a) showing typically polygonal fenestrules, Loc. A. x 5.
2: Longitudinal section (UHR30459b), Loc. A, x 5.
Fig. 3. Falsicatenipora shikokuensis NODA and HAMADA
Oblique but nearly transverse section (UHR30445a), Loc. B, x 5.
Fig. 4. Halysites kllraokensis (HAMADA) variety
Transverse section (UHR30444a), Loc. B, x 5.
Fig. 5. Halysites sllessmilchi ETHERIDGE
Transverse section (UHR30463a) showing labyrinthine fenestrules, Loc. A, x 2.

NAKAI:

Silurian Halysitids

Plate 17

788.

Silurian halysitids from Mt. Yokokura

the middle part of the Gz member of the
Yokokurayama Formation, at Loc. B.
Description :-Corallum compound, cateniform and small. It may be tabulae orhemiglobular, judged from the arangements of corallites in longitudinal sections,which are subparallel or divergent (PI. 3,
Fig. 2). The size of corallum may attain
20-25 X 30-40 mm in width, and 15-30 mm
in height.
In transverse section fenestrules arecharacteristically small, pentagonal orhexagonal, but partly tetragonal or eventriangular in shape, being 1.0-1.5 mm X
1.5-3.0 mm in size. One side of a chain
consists of typically one, occasionally of
two macrocorallites. Macrocorallites are
small, round oval, being 0.7-0.8 X 0.8-1.0
mm in size. Three to five septal spinules
are observed on one internal side ofmacrocorallites. The long septal spinules
may extend towards the axis nearly onethird of the short diameter of macrocorallite. Mesocorallites are always present,
small and polygonal in shape, with thediameter of 0.25-0.3 mm. Microcorallites
are, when observed, slit like form, being
0.05 X 0.3 mm in size. No septal spinules
are obtained in microcorallites but one
distinct septal spinule is observed in amesocorallite (Text-fig. 4f). Corallite wall
is about 0.15 mm thick and the one between a macrocorallite and a micro- or amesocorallite is about 0.1 mm. When
recrystallization has gone too far thevisceral chamber of each corallite is completely filled with sparry calcite, leaving
almost no internal features in it. In somespecimens "Balken" like partition withlight colour is seen between corallites tosomewhat intrude into a little dark outerwall of corallite (Text-fig. 4f).
In longitudinal section corallites are either
subparallel or divergently arranged. Tabulae in macrocorallites and also in mesocorallites are complete, horizontal but

153

sometimes gently convex upwards anddownward. They are 0.25-0.3 mm apartin macrocorallites and 0.2 mm apart inmesocorallites. Tabulae in microcorallites
cannot be ascertained because of difficultyin obtaining well oriented, suitable thinsection to reveal them. Septal spinules
arranged in vertical series. And in transverse section of a few corallites, they areseen to be continuous as plates. Therefore
septal spinules may be platy at their bases,
while splitting and centrally projecting
towards the axis of corallite.
Remarks :-Conspicuous feature of Halysites kuraokensis is its possession of small
and polygonal fenestrules consist of one
or two beautifully oval macrocorallites.
All the present specimens are assignable
to H. kuraokensis with certainty. In themode of fenestrules Halysites encrustans
BUEHLER (1955) closely resembles H.
kuraokensis but the former has muchlarger macrocorallites, while septal spinules are much better developed in thelatter. In the size and shape of macrocorallites Halysites gamboolicus ETHERIDGE(1904) is quite comparable with H. kuraokensis. But this Australian species showsmuch wider fenestrules which are polygonal but sometimes meandrine, comparedto the Japanese form. In the size andshape of macrocorallites Halysites louisvillensis STUMM (1965) has some similarity
with H. kuraokensis. Presence of many
spinules in macrocorallites of the former
species is also similar to the state in H.
kuraokensis.
However the American
species reveals clearly meandrine fenestrules and is distinct from the Japanese
species.
Halysites kuraollensis (HAMADA) variety
PI. 17, Fig. 4

Material :-Only one specimen (UHR

Hitoshi N AKA!

154

30444) was collected from the middle partof the G2 member of the Yokokurayama
Formation, at Loc. B.
Remarks :-The specimen at hand isalmost identical with the preceding Halysites kuraokensis in detail. The only difference between the two is that theformer specimen reveals smaller size inevery respect compared to the latter. The
size of fenestrules in the present specimen
is 0.3-0.8 mm X 0.6-1.75 mm, the average
being 0.75 X 1.25 mm. External size ofmacrocorallites is 0.6-0.8 X 0.7-0.9 mm.
The present specimen is here considered
to represent a small variety of H. kuraokensis described above.

Halysites sp. A
PI. 19, Fig. 1; Text-fig. 4g

Material :-Only one fragmental specimen (UHR30464) was available from the
Ga member of the Yokokurayama Formation, at. Loc. A.
Description :-Because of fragmentallypreserved, corallum shape and size are notexactly observed. Corallum is cateniform,
very small, being 5.0 X 15.0 mm in width
as far as it is preserved.
In transverse section fenestrules are
distinctly very small, and polygonal inshape. They are tetragonal, pentagonal
and hexagonal, or partly triangular inform. Their size is somewhat variable

and measures 0.5-0.7 X 0.5-1.5 mm in width.
Each side of fenestrules consists of one
or two macrocorallites. Macrocorallites
are characteristically small and typicallyeye shaped, or rugby ball like in form,
being 0.45-0.55 X 0.65-0.8 mm in external
size. One or two very short septal spinules are often observed on each side ofmacrocorallite wall. Mesocorallites arewell developed, triangular or rectangular,
0.2-0.3 mm in length on each corallite
side. Microcorallites are also developed
and very small. They are subrectangularin shape and 0.1 mm in diameter. Wallis very thin and 0.05 to 0.07 mm in thickness. "Balken" like structure is usuallydeveloped at each junction of two corallites (Text-fig. 4g).
No longitudinal section is obtainable.
Remarks :-The present form is characterized by very small, polygonal fenestrules with very small macrocorallites
having less pronounced septal spinules.
No comparable forms with the present
one have been described in a group of
halysites without septal spinules (ETHERIDGE, 1904). In a group of halysitids
with characteristically polygonal shape ofsmall fenestrules the present form closely
resembles Halysites encrustans and H.
kuraokensis. H. encrustans differs howeverfrom the present form in having muchlarger macrocorallites. Halysites kuraokensis most resembles the present form
but is distinguishable from the latter in

Explanation of Plate 18
Figs. 1-2. Halysites kuraokensis (HAMADA)
1: Transverse section (UHR30441a), Loc. B, x 5.
2: Longitudinal section (UHR30443b), Loc. B, x 5.
Figs. 3-4. Halysites suessmilchi ETHERIDGE
3: Transverse section (UHR30463b), Loc. A, x 8.
4: Longitudinal section (UHR30463c), Loc. A, x 8.
Fig. 5. Halysites sp. B
Transverse section of fragmental specimen (UHR30467), Loc. A, x 5.

NAKAI:

Plate 18

733.

Silu1'ian halysitids from Mt. Yokokura

having larger macrocorallites with welldeveloped septal spinules. Another comparable species with the present one is
Halysites gamboolicus ETHERIDGE from
Australia, especially in respect to theirsize and shape of macrocorallites which
carries less developed septal spinules.
This Australian species differs from thejapanese form in having larger fenestrules
and macrocorallites which have more conspicuous septal spinules compared to thelatter.
The present form belongs to thesmallest member of the genus Halysites as far
as the size of macrocorallites are concerned. It may represent a new species
related to Halysites kuraolwnsis. Morespecimens are needed to clarify its naturein longitudinal section and the extent ofmorphological variation within the form,
before the author proposes a new species
for this type of coral.
Halysites sp. B
PI. 18, Fig. 5; PI. 19, Figs. 4-5;
Text- fig. 4eMaterial:- Three fragmental specimens represented by three thin sections(UHR30465-30467) have been collectedfrom the G3 limestone of the Yokokurayama Formation, at Loc. A.
Description :-All specimens are fragmentally preserved. Corallum shape andsize and fenestrule characters are notobserved. The largest specimen collectedby the author, is a gently curved. single
chain which consists of only six macrocorallites (PI. 19, Fig. 4).
In transverse section macrocorallites areroundish oval or circular, being 1.5 X 1.7
mm in external size. Corallite wall is
extremely thick, and measures 0.5 to 0.6
mm in thickness. In contrast, wall between macro- and microcorallite is very

155

thin, being 0.05-0.1 mm in thickness.
Mesocorallites are not preserved. Microcorallites are slit-like, being 0.05-0.1 X 0.3
mm in size (Text-fig. 4e). Because corallite wall is usually recrystallized and sometimes much thickened, inner characters ofmacro- and microcorallites cannot be examined.
In transverse section tabulae of macrocorallites are thin, complete and horizontal
or gently concave upwards. They distribute 0.3-0.4 mm apart. Tabulae of microcorallites are not observed.
Remarl?s :-No identical species with thepresent form is readily available, although
the latter is imperfectly preserved andpoorly represented.
Amongst forms of halysitids with roundand thick walled macrocorallites Halysites
cratus ETHERIDGE of HAMADA (1958, pI.
10, fig. 5), H. regularis FISCHER-BENZON
figured by KLAAMANN (1966, pI. 19, figs.
6-7), H. junior KLAAMANN (1966), H;
senior KLAAMANN (1966) described by
STASINSKA (1967, 1974), I-!. crassus STASINSKA (1974) and H. juni%rmis 'STASINSKA (1974) may be comparable withthe present japanese form.
Halysites
cratus of HAMADA (1958) is a badly crystallized form which shows thin and at thesame time much thickened corallite wall.
The present form has more round macrocorallite with much thicker wall, andmuch thinner microcorallites compared to
HAMADA'S form. Halysites junior KLAAMAN~ (KLAAMANN, 1966, pI. 18, figs. 1-4;
pI. 19, figs. 4-5; text-fig. 28a-b, STASI~SKA, 1967, pI. 8, figs. 1, 3a-b and STASIKSKA, 1974, pI. 18, figs. 4-5) and H.
senior KLAAMANN (KLAAMANN, 1966, pI.
19, figs. 2-3. STASINSKA, 1967, pI. 9, fig.
2a-b and STASINSKA, 1974, pI. 8, figs. 1,
3; pI. 9, fig. 2) and I-!. regularis FISCHERBENZ ON figured by KLAAMANN (1966) all
have decidedly larger macrocorallites than
the japanese form which has macrocoral-

Hitoshi NAKAI

156

lites of intermediate size. In the size ofmacrocorallites Halysites junioformis iscomparable to the present form. The
former has a little smaller macrocorallites
with less thick wall. Microcorallites arewider in H. junioformis than in thepresent form.
Halysites sp. A of KAWAMURA (1980,
p. 288-290, pI. 7, fig. 4, pI. 8, figs. 1-2;
text-figs.7a-b) is another ally to the present form. But this form has more oval,slightly larger macrocorallites which are
more distinctly spaced; while the present
form has round, closely spaced macrocorallites with much thicker wall.
The present form is unfortunately too
imperfect to treat as representing a newform.
Acknowledgement :-The author acknowledges Emeritus Professor Masao MINATO and Dr. Makoto KATO of Hokkaido
University, and Professor Masae OMORI of
Azabu University for their guidance,
supervision and encouragements.
Dr.
KA TO critically read the manuscript. Assistance has been rendered by the staff
and fellow students of the Department of
Geology and Mineralogy, Faculty of Science, Hokkaido University.
References
BUEHLER, E.]. (1955): The Morphology andTaxonomy of Halysitidae. Bull. PeabodyMus. Nat. Hist., no. 8, 75 p.,3 figs., 12 pIs.

ETHERIDGE, R. Jr. (1904): A Monograph of
the Silurian and Devonian corals of New
South Wales, part 1, the Genus Halysites.
Mem. Ceol. Surv. New South Wales,
Palaeontology, vol. 13, 39 p., 9 pIs.
FLOGEL, H. (1962): Korallen aus dem Silurvon Ozbak-kuh (NE-Iran). jb. Ceol. B.
A., Bd. 105, s. 287-330, abb. 1-4, tab. 1-4,
taf. 20-24.
HAMADA, T. (1956): Halysites kitakamiensis
SUGIYAMA from the Gotlandian Formation in the Kuraoka District, Kyushu,
Japan. japan. jour. Ceol. Ceogr., vol. 27,
no. 2-4, p. 133-141, text-figs. 1-2, pI. 9.
- - (1957a): On the septal projection of the
Halysitidae. jour. Fac. Sci., Univ. Tokyo,
ser. 2, vol. 10, p. 383-391, text-figs. 1-8,
pI. 6.
- - (l957b): On the classification of the
Halysitidae, l. jour. Fac. Sci., Univ.
Tokyo, ser. 2, vol. 10, p. 393-405.
- - (1957c): On the classification of the
Halysitidae, 2. jour. Fac. Sci., Univ.
Tokyo, ser. 2, vol. 10, p. 407-430, tabs.
1-2, text-figs. 1-2, maps. 1-2.
- - (1958): Japanese Halysitidae. jour. Fac.
Sci., Univ. Tokyo, ser. 2, vol. 11, p. 91114, tabs. 1-2, text-figs. 1-4, pIs. 6-10.
HILL, D. (1954): Coral faunas from the Silurian of New South Wales and the Devonianof Western Australia. Bull. Comm. Austr.,
Dep. Nat. Develop., Bureau Min. Resour.,Ceol. Ceophy., no. 23, p. 1-51, pIs. 1-4.
- - and STUMM, E. C. (1956): Tabulata. In:
MOORE, R. C. (ed.) , Treatise on Invertebrate Paleontology, part F. Coelenterata.
Geol. Soc. Amer. and Univ. Kansas Press,
F. 447-477.

Explanation of Plate 19
Fig. l. Halysites sp. A, with fragments of Schedohalysites
thamnoporoid
Transverse section (UHR30464), Loc. A, x 8.
Figs. 2-3. Halysites catenularius (LINNAEUS)
2: Transverse section (UHR30439a), Loc. B, x 5.
3: Longitudinal section (UHR30439b), Loc. B, x 5.
Figs. 4-5. Halysites sp. B
4: Transverse section (UHR30465), Loc. A, x 5.
5: Tangential section (UHR30466), Loc. A, x 5.

kitakamiensis (SUGIYAMA) andNAKAI:

Silu'rian Halysitids

Plate 19

733.

Silurian halysitids from Mt. Yokohtra

JIA, H. and Wu, j. (1977): Anthozoa. In:"Palaeontological atlas of Central.south
China", Part 1, Early Palaeozoic. "Geology
Press", Beijing, p. 9-24, text-figs.6-1O, pIs.
4-9. (in Chinese)
JULL, R. K. (1962): Silurian Halysitidae of theRonning Group, Western Canada. jour.
Alberta Soc. Petroleum Ceol., vol. 10, no.
6, p. 326-330, figs. 1-3.
KATO, M., MINATO, M., NIIKA\\"A, I., KA\\'A:-'WRA, M., HAGA, S. and NAKAI, H. (inpress): Silurian and Devonian corals ofjapan. Acta Palaeont. Polonica.
KA WA:-'IURA, 1VI. (1980): Silurian Halysitids
from the Simoarisu district, Iwate Prefecture, Northeast japan. jour. Fac. Sci.,
Hokkaido Univ., ser. 4, vol. 19, no. 3, p.
273-303, tabs. 1-2, text-figs. 1-7, pIs. 1-8.
KJIAAMAHH, 3. (1966): YlHKOMMYHIlKaTHbl9
Ta6yJlHTbI 3CTOHIlIi. YlHCT. feoJl. AKa,ll.
HAYK ECTOH CKOI1 CCP, TAJIJIYlH,
96 CTp., 2 Ta6., 31 pIlC. 22 Ta6J1.
KUWANO, Y. (1976): Finding of Silurian
conodont assemblages from the Kurosegawa
tectonic zone in Shikoku, japan. Mem.
Nat. Sci. Museum, no. 9, p. 17-22, pI. 2.
(in japanese with English Summary)
JIEJIEllLYC, B. JI. (1972) : CiIJlypllllcKlle Ta6yHTbI Ta,ll)KIlKHcTaHa. YlHCT. feoJl. AKa,ll.
HAYK T AlI)KYlKCKOI1 CCP, Yl3,ll,llTeJl1>CTBO 1I.0HYllll, lI.YlllAH6E 85 CTp., 16
Ta6., 5 pIlC., 26 Ta6J1.
LIN, B. Y. (1975):
Tabulata. In: "Early
Paleozoic of western slope of Da-ba-shan".
"Geology Press", Beijing, p. 203-221, pIs.
51-70. (in Chinese)
MYiPOHOBA, H. B. (1965) : HeKOTopble HOBble
BIl,llbl Ta6yJlHT H feJleOJlHTIl 113 BepxHero
CHJIypa CaJIaHpa Ii fopHoro AJITaH. Ta6yJIHTOMopcjJHbIe KOpaJIJIbI
0p,llOBIlKa
H
CHJIypa CCCP (Tpy6bl 1 BcecOIoeHoro
CIlMHo31lYMa HO Yl3Yll,eHIlIO YlcKoHaeMbIx
KOpaJIJIOB, BblH 1). Yl3,llaTe1>CTBO HAYKA,
MOCKBA, CTp. 127-138, Ta6JI. 28-34.
SCRUTTON, C. T. (1971):
Palaeozoic coralfaunas from Venezuela, part I, Silurian
and Permo-Carboniferous Corals from the
Merida Andes. Bull. Britsh Mus. (Nat.
Hist.) , geol., vol. 20, no. 5, p. 183-227, 8
text-figs., 5 pIs.

157

. STASIl'>SKA, A. (1967): Tabulata from Norway, Sweden and from the erratic boulders
of Poland. Palaeontologia Polonica, vol.
18, p. 1-112, 14 text-figs., 6 tabs., 38 pIs.
- - (1974): Silurian Tabulata from Northeast Poland.
Acta Palaeont. Polonica,
vol. 19, no. 4, p. 501-517, fig. 1, tabs. 12, pIs. 18-21.
STEARN, C. W. (1956):
Stratigraphy andPalaeontology of the Interlake Group andStonewall Formation of Southern Manitoba.
Mem. Ceol. Surv. Canada, no. 281, 162
p., 2 maps., 5 figs., 16 pIs.
STRCSZ, D. L. (1961): Lower Palaeozoic corals
from New South Wales. Palaeontology,
vol. 4, p. 334-361, tab. 1, text-figs. 1-5,
pIs. 42-45.
STC:-'I:-'I, E. C. (1965): Silurian and Devonian
corals of the Fall of the Ohio. Mem. Ceol.
Soc. Amer., no. 93, 184 p., 80 pIs.
SCGIYA:-'LA,., T. (1940):
Stratigraphy andPalaeontological studies of the Gotlandian
deposits of the Kitakami Mountainland.
Sci. Rep. Tohoku Imp. Univ., second ser.
(Geology), vol. 21, p. 81-146, text-figs. 16, pIs. 13 (1) -32 (20).
SUYARI, K. (1961): Geological and Paleontological Studies in Central and Eastern
Shikoku, japan, Part I. Geology. jour.
Cakugei, Tokushima Univ., vol. 11, p. 1176, figs. 1-6, 1 map., 1 chart.
TIIO:VIAS, H. D. and S:VIITH, S. (1954): The
coral genus Halysites FISCHER von WALDIIEI:-'1. AnI!. Mag. Nat. Hist., ser. 12,
vol. 7, p. 765-774, pIs. 20-22.
Y ABE, H. and SUGIYA1\IA, T. (1942): A New
Occurrence of Fossiliferous Gotlandian
Limestone on Yokokura-yama, Ogiri-mura,
Takaoka-gun, Koti-ken. Proc. Japan Acad.,vol. 18, no. 2, p. 78-81, figs. 1-3.
YANG, S., KI?\I, C. and CHOW, X. (1978):Tabulata. In: "Palaeontological atlas ofSouthwest China, CUiZOll Volume", Part
1, Cambrian-Devonian. "Geology Press",
Beijing, p. 161-250, pIs. 56-93. (in Chinese)
YU, C. ;"'1. (1962): "Middle Silurian corals ofNorth Chi-lien-shan". In: "Ceology of
Chi-lien-shan". "Science Press", Beijing,
vol. 4, fasc. 3, p. 13-109, text-figs. 1-19,
tabs. 1-5, pIs. 1-42. (in Chinese)

Hitoshi NAKAI

158

Gomi 1i*, Kuraoka il'itc1f4l, Kurosegawa ~i'J!J[JII, Ochi ~9;J], Shiroishi BE, Gion-yama W,u;IlllILll,
Mt. Yo!co!cura (=Yo!co!curayama) tlfi:l%"Il1, Niyodo R. 1=lJEJII, Ogiri R. :k;j-jIi)JII
i\%J;IJ~~:fi'ltirl110):jji{:l%"I11J~mf"/ 1t.-It.-weT:/ ::tm-;cO) 1, Halysitidae-: ~~·It., :JJl.:fE, j:¥;J9;u~1HlIi~LllmfO)"/ 1t.-It.-weT:/ ::tmv;:' '?~'-C, ti"1:.*r~Il<.J1iIf~e>a::j!~-C~' QiJ~, ;:: ,:x~ Ullc L-c, [q)Jill~O) 4 Jl!l,~ J:f) mfl±\ Lt.: Halysitids, 8 f1l!:>a::~c.jl~ L, ;l;b-lt-C, Il'!jmf:!lliO):!llij~l);:. ,?~,
-CllltllC.T Q
GIYAMA),0*!f.jH~-c·ilCjlili: L t.::illHt.tJ,T O)jiJi I) -e;l; Q 0

Schedohalysites kitalwmiensis (Su-s. sp., Falsicatenipora shikokuensis NODA and HAMADA, Halysites catenu-

larius (LINNAEUS), H. suessmilchi ETHERIDGE, H. kumolwnsis (HAMADA), H. sp. A,
H. sp. B It, /f7'G3ttJ:t~*-c"l:t;l;QiJ~, :to;C
H. sp. B. ;:::I1-GO)? 0t;" Halysites sp. A
G <m1!c~x. GJcQo it.:, Halysites catenularius (LIN::-1AEUS) c H. lwraokensis (I-lA-

c:vIADA)

It., *:!lli~iJ'G!tfJJ~-CO)mfl±\-c';l;Qo

9='1f J;'y

Trans. Proc. Palaeont. Soc. Japan, N. S" No. 123, pp. 159-167, pis. 20,21, September 30, 1981

734.

STUDIES ON THE ONTOGENIC AND PHYLOGENICDEVELOPMENT OF TWO UPPER CAMBRIAN
TRILOBITES FROM SOUTH DAKOTA*
CHUNG-HUNG HU
Department of Physics, Taiwan Normal University, Taipei

Abstract. The ontogenic and phylogenic development of Parabolinoides contractus and Taenicephalus shumardi are described. The morphogenesis of thesetrilobite larvae are subdivided into three different metamorphic stages: paraprotaspid,
early meraspid, and late meraspid stages. These two trilobites were possibly the
direct descendants of the Elvinia-Irvingella stock due to the neotenic evolution oflate meraspis, and the progenitor of the later trilobite Ptychaspis-Prosaukia throughcontinuum orthogenetic neoteny of the early meraspis.

Introduction
The purpose of the present report is todescribe the ontogenic and phylogenie
development of two Upper Cambrian,Conaspis Zone trilobites from North America: Parabolinoides contractus FREDERICKSON and Taenicephalus shumardi(HALL). The ontogenic sequences of thespecies are subdivided into three different
morphologic stages: paraprotaspid, earlymeraspid, and late meraspid stages. Allof these stages are with distinct morphologic characteristics. In the paraprotaspid stage, the carapace is subroundor trapezoidal in outline, about 0.50-0.80
mm in length (sag.), and consists of alarge cephalic and a small transverse
protopygidial shield. The early meraspid
skeleton is often disassociated from thepygidium, the sagittal length of the
cranidium is about 0.75-1.20 mm long(sag.); the anterior border appears, andthe posterior fixigenal border broadens.

* Received February 27. 1981.

The late meraspid cranidium is 0.90-1.60
mm long (sag.), trapezoidal in outline witha narrow preglabellar field lying between
the frontal furrow and the preglabellar
margin, and with complete glabellar
furrows.
Quite a few ontogenic development of
pre-Conaspis Zone (=Elvinia Zone) trilobites are known. These include Elvinia
roemeri (SHUMARD), Cliffia typica Hu,
Irvingella major ULRICH & RESSER,
Cameraspis convexa (WHITFIELD) (Hu,1979), Housia ovata PALMER, Aphelotoxon
triangulata Hu, Pulchricapitus davisi
KURTZ (Hu, 1980), Ponumia obscura (LocHMAN), Housia canadensis (Hu, 1970) ... etc.
Within these species, the protaspis andmeraspis of Parabolinoides contractus andTaenicephalus shumardi both have morphologic characteristics similar to the latemeraspis and even early holaspis of
Elvinia-Irvingella, all possess the small
ocular lobe, narrow anterior border, broad
triangular fixigena, incomplete glabeIlar
furrows, and the same shaped pygidium.
159

160

Chung-Hung Hu

Thus, it might be postulated that thedirect progenitor of Parabolinoides andTaenicephalus was possibly the ElviniaIrvingella stock due to neotenic evolution.
A very well preserved ontogenic sequence of the post Conaspis Zone (=Ptychaspis-Prosaul<ia Zone) trilobite Ptychaspis bullasa LOCHMAN & Hu wasreported from Preston Quadrangle, Idaho
by Hu (1971). This trilobite has some morphologic similarities to the early meraspis
or even late protaspis of ParabolinoidesTaenicephalus. They all possess a narrowanterior border, medium-sized palpebral
lobe, segmented glabella, broad triangular
fixigena, and densely granulated skeletal
surface. The similarities of these species
may also be indicative of neotenic evolution of the early meraspis of Parabolinoides-Taenicephalus, i. e., the continuum
orthogenetic neoteny from the ElviniaIrvingella, thoughout the ParabolinoidesTaenicephalus to the Ptychaspis-Prosaukia
stocks.
Acl<nowledgements.- The author wishes
to express his thanks to Dr. C. LOCHMANBALK, New Mexico Institute of Mining
and Technology, for her guidance at thesummer field camp around the Black
Hills, South Dakota, 1962, on which thepresent studied materials were collected.
Thanks are also go to Dr. Kenneth E.
CASTER, University of Cincinnati forreading over the present manuscript. The
described specimens are all stored in the
Geology Museum, University of Cincinnati(GMUC), Ohio.
Paleontological Description
Genus Parabolinoides FREDERICKSON,
1949
Parabolinoides contractus FREDERICKSON
PI. 20, Fgs, 1-35; Text-fig. 1.

Parabolinoides contracus FREDERICKSON, 1949,
p. 311, pI. 71, figs. 4-10; BERG, 1953, p.
564, pI. 59, fig. 3; BELL & ELLIN\\"OOD,
1962, p. 399, pI. 56, fig. 12; LOCIIMAN,
1964, p. 49, pI. 12, figs. 1-14; Hu, 1969, p.
449, pI. 3, figs. 1-38 & text·fig. 5.
Parabolinoides hebe FREDERICKSON, 1949, p.
361, pI. 70, figs. 7, 8; pI. 71, figs. 1-3;
BERG, 1953, pI. 564, pI. 59, fig. 24; BELL
& ELLINWOOD, 1962, p. 400, pI. 56, figs. 611; KURTZ, 1975, p. 1040, pI. 4, figs. 38,39.

Remarks.- The present species is represented by very abundant immature andmature skeletal fragments. The adultskeletons are characterized by two different morphologic groups; one group has
a broad and short glabella, broad anterior
brim, broad librigena, and semicircularpygidium; and the other group has a narrower and longer glabella, narrower
anterior brim, narrower librigena, andsubtriangular pygidium. These differences
are here postulated as sexual dimorphism
within the same species population. The
first groups is briefly assigned to "male"and the second to "female" forms.
BELL & ELLINWOOD (1962) figured a
few cranidia and pygidia identified as P.
hebe (pI. 54, figs. 6-11) and P. contractus(pI. 56, fig. 12). The cranidia (=P. hebe;
pI. 56, figs. 6-9) are here identified as"female" forms, and those of cranidium
and pygidium (=P. contractus, pI. 56, fig.
12; P. hebe, pI. 56, figs. 10, 11) are correlated as "male" in the present report.
STITT'S (1971) P. contractus (pI. 2, figs. 11,12) and KURTZ'S (1975) P. hebe (pI. 4, figs.
38, 39) are synonymized as "female" and"male" forms, within the same species
population in the present text.
The ontogenic development of thepresent species are comparable with thosematerials reported from the same generalarea and the formation by Hu (1969), except that the earliest known immatureskeletons found in the present studied

734.

Two Upper Cambrian trilobitesmaterials are assigned to the para protaspid stage (PI, 20, Fgs. 1-6; Text-fig. 1A).
This instar is sub round with five axial
rings and possibly a small protopygidium ;the protopygidium is tilted sharply down-

A

o

161

ward, so that its characteristics are noteasily discerned. The skeletal surface iscoarsely covered by granules.
Thelarger instars are similar to occurrencesin the Bear Butte reported by~ Hu~ (1969).

B

c

E

F

G

~'~?;~~~~9~
J

K

L

Text-fig. 1. Parabolinoides contractus FREDERICKSON.
A-C, a growth sequence of paraprotaspid cranidia, showing the breadth of theposterior fixigenal border. x 60, x 55, x 50; D, an early meraspid cranidium, showing
the presence of the anterior border. x 30; E, F, two sizes of late meraspid cranidia;
notice the presence of the preglabellar field. x 24; G, H, "female" and "male" cranidia
associated with left librigena, showing the different shaped glabella and the incomplete last glabellar furrows. x4, 5; I, J, two different shaped thoracic segments.
x 4, x 5; K, L, "female" and "male" pygidia, showing the triangular and semicircularpygidial shapes. x 3, x 4; M, a small hypostoma.

162

Chung-Hung Hu

A small hypostoma from the present
studied materials is a bit longer andbroader than that of the Bear Butte assemblage and is assigned to an early orlate meraspid stage of the same species.
The ontogenic development of the present species is certaintly closely related
to Aphelaspis sp. (PALMER, 1962 ; Hu, 1969 ;Hu & TAN, 1971), Olenus, Dunderbergia,
Dytremacephalus (STRAND, 1927 ; ST0RMER,
1942; Hu, 1971), Elvinia, Irvingella,
Cameraspis (Hu, 1979), and Parabolinoides(Hu, 1969). The earliest progenitor of thegenus Parabolinoides was the AphelaspisOlenus stock and the most proximal progenitor was the Elvinia-Irvingella stock.
The adult cranidium of the genus Parabolinoides has some morphologic charateristics similar to those of the meraspid
cranidium of Elvinia ; i. e., the same shaped
glabella, an incomplete last glabellar furrow, broad triangular fixigena, and same
breath of preglabellar field, and a mediumsized palpebral lobe. These similarities
are possibly due to neoteny of the genus
Elvinia or Irvingella during its latemeraspid stage.
There are also quite a few genera whose
protaspides were similar to Elvinia; i. e.,
Housia, Ponumia, Clijfia, Aphelotoxon (Hu,
1970, 1979, 1980) etc., but it seems thatthese forms are unlikely to be the directprogenitor of the genus Parabolinoides,
because their meraspid cranidia all possessa conical glabella, unsegmented glabellarlobe, and shallow dorsal furrows.
Horizon and Locality.-Deadwood Formation, Upper Cambrian, Conaspis Zone;
White Canyon, about 5 miles, north-eastof Deadwood City, South Dakota.
Figured specimens.-GMUC. 43344, 43344
a-z, 43344a' -e'.

Genus Taenicephalus ULRICH& RESSER, 1924

Taenicephalus shumardi (HALL)
PI. 21, Figs. 1-28; Text·fig. 2.
Taenicephalus shumardi (HALL), LOCHMAN &Hu, 1960, p. 811, pI. 95, figs. 12-23, 31(synonymy to date).
Taenicephalus shumardi (HALL), KeRTZ, 1975,
p. 1041, pI. 4, figs. 44, 45 (synonymy todate) .

Remarks.- The present studied materials
are closely related to those from the Wind
River Mtns. reported by LOCHMAN & Hu
(1960). The similarities are especially indicated by the transverse pygidium andthe short marginal spines. GRANT (1965)
figured two triangular to round pygidia
from the Snowy Range Formation, Montana. These two different form pygidia
might not be Taenicephalus shumardi but
Parabolinoides contractus, since they are
distinctly different with those of typicalones.
The present species is represented by
two different morphologic groups as was
the case in Parabolinoides contractus. The
first group has a quadrate glabella andbroader pygidial marginal border, theother a truncatoconical glabella and narrower pygidial margin. These bimodal
phenomena are postulated as sexual dimorphism within the same species population.
The former is "female" and the latter"male", as commonly reported in various
species by the author (Hu, 1968, 1971...
etc.).
Taenicephalus shumardi (HALL),
ontogeny

The ontogenic development of the present species is incompletely known. However, the instars can be assigned to threedifferent stages: paraprotaspid, earlymeraspid, and late meraspid. The main
morphologic characteristics of these stages

734.

Two Uppel' Cambrian trilobites

A

163

8

C

o
E

G

H

J

K

L

M

Text-fig. 2. Taenicephalus shumardi (HALL).
A, B, paraprotaspides. x 35, x 25; C, early meraspis. x 20; E, G, two late meraspid cranidia. x 18, x 14; F, a librigena. x 3; D, a protaspid pygidium. x 24; I, ],"female" and "male" cranidia. x 4, x 6; H, K, two meraspid pygidia, showing theassociations of one or two thoracic segments. x 15, x 10; L, M, "female" and "male"pygidia. x 3, x 5.

are comparable to those of Parabolinoides

contractus FREDERICKSON.
Paraprotaspid stage (Pl. 21, Figs. 1-4;
Text-fig. 2A, B).-The shield is about 0.45
to 0.60 mm in sagittal length, trapezoidal
to sub round in outline, convex, divided
into a large cranidium and a small transverse triangular protopygidium; the cranidial shield is divided into axial and pleurallobes by deeply impressed furrows; theaxis is cylindrical, contains five annularrings-a round frontal lobe, three transverse oval segments, and a small terminal
portion; all are distinctly demarked byfurrows; the sides of the frontal lobe aredepressed by a pair of distinct triangularpits, and a pair of superciloid ridges extends laterally from the frontal lobe in164

Chung-Hung Hufront of the anterior pits; the fixigenal
area is broader than the axis on the midline of the cranidium (tr.), convex along
the free margin, and defined by a narrowmarginal border; the narrow elevatedpalpebral ridges are curved posterolaterally from the sides of the frontal lobe
behind the anterior pits and end at thesame level as the anterior second axial
ring (tr.); the posterior fixigenal borderis narrow, distinctly demarked by a borderfurrow, and is about the same width as
the occipital ring (tr.); the lateral end of
the fixigenal border is modified by a pairof short broad fixigenal spines which
projected posteriorly; the convex protopygidium slopes downward sharply frombehind of the posterior cranidial margin;
it is small, transverse lenticular, and contains one or two segments; no marginal
spines are observed. The surface of theskeleton is covered by coarse granules.
Early 71leraspid stage (PI. 21, Figs. 5, 810; Text-fig. 2C, E).-The cranidium istrapezoidal in outline, convex, and about

0.50-0. 80 mm in length (sag.) ; the glabella is deeply defined by a dorsal furrow,and divided into four glabellar segments
by deep furrows; the anterior glabellar
segment is roundly quadrate, and thesecond to fourth are similar in shape,
being convex, and transverse oval; theoccipital ring is subtriangular and convex,
bearing a tiny median node; a narrow
arched anterior border appears along the
cranidium; it is elevated and distinctly
delimited by furrows; the triangular fixigena is convex, and has a medium-sizedwell-delimited and narrow palpebral lobe
situated in front of the mid-line of theglabella (tr.); the elevated palpebral lobe
is arched and extends continuously fromthe anterior palpebral ridge, and ends on
the same transverse line as the second
glabellar segment; the posterior fixigena
is about the same width as the occipitalring between the fixigenal spine and thebase of the glabella; the fixigenal borderis narrow toward the occipital ring, broad
laterally, and ends in a short fixigenal

Explanation of Plate 20
Figs. 1-35; Parabolinoides contractus FREDERICKSON.
1-6, a growth sequence of paraprotaspides, showing the annular axial segments and the completion of the posterior fixigenal border. 1-4, x 60; 5, 6, x 55; GMUC. 43344, 43344a-d.
7-11, a growth series of early meraspid cranidia, showing the presence of the anterior borderand the slender conical glabella. x 23, x 30, x 25, x 28, x 24_ GMUC. 43344e-i,
12-16, a growth sequence of late meraspid cranidia, showing broadening of the preglabellar
field. 12, x 24; 13-15, x 13; 16, x 10; GMUC. 43344j-n.
18, 28, 31, dorsal and side views of small and large triangular "female" pygidia. 18, x 6.5;
28, x 3; 31, x 3.5; GMUC. 43344p, 43344a'.
19, 34, two small librigenae, showing the narrow ocular platform. x 8, x 6; GMUC. 43344q,
43344d'.
22, 23, two morphologically different thoracic segments. x 10, x 5; GMUC. 43344t, u.
17, 21, 25, 27, dorsal and side views of a few different sized "male" cranidia; showing thesubquadrate glabella. x7, x6, x5; GMUC. 433440, 43344s, 43344x.
24,33, "female" and "male" librigenae. x5; GMUC. 43344v, 43344c'.
26, 30, 32, three different-sized "female" cranidia, showing the cylindrical glabella. x 4;
GMUC. 43344w, 43344z, 43344b'.
20, 29, 35, three different-sized semicircular "male" Pygidia. x 5, x 3.5, x 6; 43344v, 43344y,
43344e' .

Hu:Trilobites ontogeny

2

Plate 20

5

3

6

11

12

16

32

33

34

35

734.

Two Upper Cambrian tl'ilobites

spine; the anterior facial suture is convergently convex, and the posterior one
is divergent posterolaterally and convex.
The surface of the shield is thickly
covered by coarse granules.
Late meraspid stage (PI. 21, Figs. 7, 11,
15; Text-fig. 2G).- The cranidium is trapezoidal in outline, convex, about 0.80-1.45
mm in sagittal length; the glabella isslenderly conical, tapering forward, anddivided into four segments by deep furrows; the first pair of glabellar furrows
are short and faint; the second to occipital
furrow are deepen laterally and shallow
across the central line; the occipital ringis transverse triangular, convex, and bearing a medium-sized median spine; thepreglabellar field is narrow and has amedian depression; the anterior border isnarrow, arches forward and has the outermargin pointed slightly posteriorly; thefrontal furrow is deep and distinct, withthe central portion behinding inwardly,
the fixigena is about one-half the widthof the glabella between the small palpebral
lobe and the dorsal furrow; the posterior
fixigena is broad and triangular, and its
elevated border is about the same width
as the occipital ring; the skeletal surface
is covered by medium-sized granules.
A few rather well preserved small andlarge pygidia are assigned to the present
species. The smallest pygidium (PI. 21,
Fig. 14; Text-fig. 2D) is roundly triangularin outline, convex, and made of six toseven segments without ankylosed pygidial plate; it is possibly a protaspid pygidium showing the initiation of the thoracic
segments. There are also two relatively
large pygidia (PI. 21, Figs. 7, 16, 24; Textfig. 2H, K) showing a well ankylosed
transverse plate and articulated with one
or two thoracic segments; these are arbitrarily assigned to the meraspid stage. It
is evident that the thoracic segments
originated from the anterior margin of165

the pygidium, which simultaneously theposterior pygidial margin gives rise to thepygidial segments from its terminal germinal region.
Remarks.- The ontogenic developmentof the present species is closely similar to
those of Parabolinoides contractus of thepresent text. No doubt, these two species
are generically related each other, bothbeing descended from the same progenitor; their furthest progenitor was
Aphelaspis-Olenus stock; both would appear have derived from the neoteny ofthe late meraspis of Elvinia or Irvingellaas discussion previously in the phylogenic
development of Parabolinoides.
The ontogenic development of Ptychaspis
bullasa LOCH,\IAN & Hu was reported by
Hu (1971). The adult cranidium of thisspecies is rather similar to those of theearly meraspis of Parabolinoideo-Taenicephalus; all lack a preglabellar field, andshow a narrow convex anterior border,
segmented glabellar lobe, small to mediumsized palpebral lobe, broad triangular
fixigenae, and coarsely granulated skeletal
surface. Obviously that this was again
due to the neoteny of the early meraspisof the Parabolinoides-Taeniceplwlus stock.
Presumably neotenic evolution was an
orthogenic continuum from the ElviniaIrvingella throughout the ParabolinoidesTaenicephalus to the Ptychaspis-Prosauhia
stocks.
Horizon and Locality.-Deadwood Formation, Upper Cambrian, Concaspis Zone;
east side of road cut. Brownsvill Junction,
about 6 miles south of Deadwood City,
South Dakota.
Figured speci7l1ens.-GMUC. 43343, 43343
a-x.
References
W. C. and ELLIl'WOOD, H. L. (1962)
Upper Franconian and Lower Trepealeauan

BELL,

166

Chung-Hung Hu

Cambrian trilobites and brachiopods, Willbern Formation, central Texas. jour.
Paleont., vol. 36, no. 3, pp. 385-423.
BERG, R. R. (1953): Franconian trilobites from
Minnesota and Wisconsin. jour. Paleont.,
vol. 27, pp. 553-568.
GRANT, R. E. (1965): Faunas and stratigraphyo(~the Snowy Range Formation (Upper
Cambrian) in southeastern Montana andnorthwestern Wyoming. Ceol. Soc. America, Mem. 96, 171 pp.
Hu, C. H. (1969): Ontogeny and sexual dimorphism of three Upper Cambrian trilobites.
jour. Nanyang Univ., vol. 3, pp. 438-462.
- - (1970): The ontogenies of Ponumia
obscura (LOCIIMAN), N. G., and of Housia
canadensis (WALCOTT) (Trilobita) fromthe Upper Cambrian of the Big Horn
Mountains, Wyoming. canadensis Paleont.
Soc. japan, Trans. Proc., N. S., no. 77, pp.
253-264.
- - .(1971): Ontogeny and sexual dimorphismof Lower Paleozoic Trilobita. Palaeontographica Americana, vol. 7, no. 44, pp.
31-135.
- - (1979): Ontogenic studies of a few Upper
Cambrian trilobites from the Deadwood
Formation, South Dakota. Paleont. Soc.

japan, Trans, Proc., N. S., no. 114, pp.
49-63.
- - (1980): Ontogeneis of a few Upper Cambrian trilobite from the Deadwood Formation, South Dakota. Paleont. Soc. japan,
Trans. Proc. N. S., no. 119, pp. 371-387.
Hu, C. H. and TAN, L. L. (1971): Ontogenyof two Upper Cambrian trilobites from
northeastern Black Hills, South Dakota.
Palaeont. Soc. japan, Trans. Proc., N. S.,
no. 82, pp. 61-72.
KURTZ, V. E. (1975) : Franconian (Upper Cambrian) trilobites faunas from the Elvinia
groups of southeast Missouri.
jour.
Paleont., vol. 49, no. 6, pp. 1009-1043.
LOCHMAN, C. (1964): Upper Cambrian faunas
from the subsurface Deadwood Formation,
Williston Basin, Montana. jour. Paleont.,
vol. 38, no. 1, pp. 33-60.
LOCHMAN, C. & Hu, C. H. (1960-1962) : Upper
Cambrian faunas from the northwest Wind
River Mountains, Wyoming (Part I, II, III).
jour. Paleont., vol. 34, no. 5, pp. 793-834;
vol. 35, no. 1, pp. 125-146; vol. 36, no. 1,
pp. 1-28.
P ADlER, A. R. (1962): Comparative ontogeny
and some Opisthoparian, Gonatoparian, andProparian Upper Cambrian trilobites. jour.

Explanation of Plate 21
Figs. 1-28; Taenicephalus shumardi (HALL).
1-4, four different-sized paraprotaspides, showing the axial segments and the completion of
the posterior fixigenal border. x 32, x 31, x 24, x 16; GMUC. 43343x. 43343w, 43343v,
43343u.
5, 8-10, four different-sized early meraspid cranidia, showing the appearence of the anteriorborder and the dorsal facial sutures. x 22, x 18, x 14, x 18; GMUC. 43343t, 43343q,
43343p, 433430.
6, 19, 22, three different-sized librigenae; notice the small ocular ring and the short genal
spine. x6; GMUC. 43343s, 43343g, 43343d.
7, 16, 24, three meraspid pygidia, showing the segmentation of the thoracic segments andthe short marginal spine. x 15, x 12, x 10; GMUC. 43343r, 43343i, 43343c.
14, a protaspid pygidium, showing the thoracic segmentation. x 24; GMUC. 43343k.
11, 15, two late meraspid cranidia; notice the presence of the preglabellar field and the completion of the glabellar furrows. x 12, x 16; GMUC. 43343n, 43343j.
13, 18, 25, dorsal and lateral views of a "female" cranidium and a pygidium; notice the subquadrate glabella and the broad pygidial margin. x 4, x 2.5, x 5; GMUC. 433431, 43343b.
12, 17, 20, 21, 23, 26-28, dorsal and lateral views of a few "male" cranidia and pygidium;notice the truncatoconical glabella and the narrow elevated pygidial margin. 12, x7; 17,x5; 20, x8; 21, x4; 23, x10; 26, x4; 27,28, x4; GMUC. 43343m, h, f, e, a. 43343.

Hu .'

Trilobites ontogeny

Plate 21
•

F'

/IJ

.....

.'

2

8

7

9

6
11

10

12

13

14

15

16

18

20
17

19

22

25

24

23

26

27

~

:. .. t- .~
5

4

3

..,.
.,-

28

734.

Two UP1Je1" Cal1~brian trilobites

Paleont., vol. 36, no. 1, pp. 87-96.
STITT, J. (1971): Late Cambrian and earliest
Ordovician trilobites, Timbered Hills andLower Arbuckle groups, western Arbuckle
Mountains, Murray County, Oklahoma.
Oldanhoma Geol. SUl'v., Bull. 110, 83pp.

167

STORMER, L. (1942):
Studies on trilobites
morphology (Part II). Norsl1. Geol. Tids·
shift, Bd. 21, pp. 49-164.
STRAND, T. (1927): The ontogeny of Olenus
gibbosus. NOl'sk. Geol. Tidssh., Bd. 9, no.
3-4, pp. 320-329.

~~~·V~~~~$~Y~Y7~~.~28~OO~~~t*.~~~M~:*~mv~~
1+Ij]iLI::frf)~ Y ~Y7*c~~m~ Parabolinoides contractus :t".l: lY Taeniceplwlus shumal'di~OO~~~~&.L, *.~~~~.Lko ~hG~~.~~~~~~~~,

*••

m·.~

~j!1J • IjjEr.p~m~ 3 j!1Ji:::.7.i"t'10 ~ t iJ'-C·~ 00 $I*Wj\!l~~~i:tjjj'(illit JJJ(kiij{!,t!U I) nJi: I), •~~j!1JI:::.IDWf,;1ltr~iJ'~I'Lbh, 1!!E~~mf:::' iiijliJ{l{!f,;fiIiiJ; -C. ~ 00
P. contractus :J:o.l: lY T. shumal'di ~,FiX;~~:t Elvinia-hvingella ~1!!Er.~I~jW~)jJ~~

neotenic evolution ~ 1 fJU t;it X. G h 0 i fe., Pa rabolinodes- Taenicephalus
Ptychaspis-Prosaullia ~:t Elvinia-hvingella ~.9"~JVJ~)jJ~~JT1w'~~ L,

M~~~ L,~1&~~h~~~®~~M~~~M*t5bh00

0

M &fi

Trans. Proc. Palaeont. Soc. Japan, N. S., No. 123, pp. 168-178, pIs. 22-26, September 30, 1981

735. NOTE ON PRA VITOCERAS SIGMOID ALE Y ABE(CRETACEOUS HETEROMORPH AMMONITE) *TATSURO MATSUMOTOll, YOSHIRO MOROZUMF), YUH BAND0 3 ),HISAO HASHIMOT04) and A TSUSHI MA TSUOKN)

Abstract. Pravitoceras sigmoidale YABE (1902) was established on several
fragmentary specimens. Based on better preserved specimens of subsequent collections, we have made clear the characters of this peculiar heteromorph ammonite,giving a redefinition. This species has an affinity with and was probably derived
from a species of Didymoceras, with an increase in the apical angle of the helicalphragmocone so that it lies almost in one plane on which the uncoiled and then retroversed body-chamber also lies. Therefore, it should be assigned to the family Nostoceratidae. It occurs at a particular horizon of the Izumi Group above the part containing Didymoceras awajiense YABE and below the beds containing Inoceramus(Endocostea) shikotanensis NAGAO et MATSUl\WTO. This horizon can be ascribed tothe uppermost part of the Lower Hetonaian Stage [K6aJ of the Japanese scale, i. e.
approximate correlative of the Campanian.
Some discussions are given on the habitat and mode of life of this peculiar ammonite.

Introduction
Pravitoceras sigmoidale YABE, a Cretaceous ammonite species of a peculiar form,
was described by YABE (1902, 1915) on anumber of specimens, which were, however, more or less incompletely preserved.
Therefore, its true features may not havebeen properly understood. Fortunately,
several better preserved specimens are1) c/o Department of Geology, Kyushu University, Fukuoka 812
2) Osaka Museum of Natural History, Osaka
5463) Department of Geology, Kagawa University,
Takamatsu 760
4) 88 Ohteratsuji, Itano, Tokushima Prefecture779-01
5) Department of Earth Science, Osaka City
University, Osaka 558* Read at Toyama, Oct. 10, 1980; received
March 15, 1981.

168

at our disposal. In this paper we redescribe this species on these as well as
previous specimens and discuss its taxonomic position, geological age and habitat.
Before going further, we thank Dr.
Yasuo MAEDA and Messrs. Isamu SHINOHARA, Hideo ITO, and Shigeki NANKO,
who have provided the specimens of theircollections for this study. Thanks areextended to Professor K. NAKAZA w A and
Dr. D. SHIMIZU of the University of Kyoto[KU.], Dr. I. HAYAMI of the University
Museum, the University of Tokyo[UMUT.], Professor T. KOTAKA of Tohoku University [IGPS], Dr. I. OBATA of
National Science Museum [NSM.], Dr. Y.
KANIE of Yokosuka City Museum [YCM.],
Professor K. KANMERA of Kyushu University [GK.] and Dr. M. CHIn of the
Osaka Museum of Natural History[OMNH.], who gave us facilities to study

735.

Pravitoceras sigmoidale Y ABE

the collections of the respective institutions. We also owe thanks to Dr. C. W.
WRIGHT for his kindness in criticallyreading the typescript, Professor K. ICHIKA W A for his kind help and Messrs. Y.
MIZUNO and Y. YASUI for giving valuable
information. Miss Kazuko HARA assisted
us in preparing the typescript. The repositories of the described specimens arein the above institutions and also Kagawa
University [GLKU.], with abbreviations
indicated in square brackets.

Palaeontological Description

Pravitoceras sigmoidale YABE
PI. 22, Fig. 1; PI. 23, Figs. 1, 2;
PI. 24, Fig. 3; PI. 25, Figs. 1, 2;
PI. 26, Fig. 1; Text·fig. 1
1902. Pravitoceras sigmoidale Y ABE, Jour.
Ceol. Soc. Tokyo, vol. 9, p. 6, pI. 1,
figs. 2-4.
1915. Pravitoceras sigmoidale YABE; YABE,
Sci. Rept. Tohoku Imp. Univ., 2nd ser.,vol. 4, no. 1, p. 19, pI. 2, figs. 1-4 (nonpI. 3, fig. 1).

Material :-Although YABE (1902) indicated a number of syntypes, only thefollowing two are accessible at present:
UMUT. MM7478 (YABE, 1902, pI. 1, fig. 2),
from Minato, internal mould, coiled part(incomplete)
UMUT. MM7479 (YABE, 1902, pI. 1, fig. 3),
from Minato, internal mould, a part ofthe body-chamber
The hypotype of S. YEHARA'S collection,
described by YABE (1915, pI. 2, fig. 1)
from Anaga, internal mould, last part ofthe body-chamber, and that of H. SASAI
mentioned by SASAI (1936, p. 593) [UMUT.
MM7961], from Minato have been also
examined.
The specimens which well supplement

169

the above for the present description are
as follows:
OMNH. M2177 (PI. 22, Fig. 1; Text-fig.
1), a fairly well preserved specimen
with test, and OMNH. M2178 (PI. 23,
Fig. 2), both obtained by A. ~[A TSUOKA(1976-4-1), from the same rock at Minato
S. NANKO'S private collection (PI. 24, Fig.
3), from Minato, internal mould withwell exposed sutures
GLKU. IZ-80003 (PI. 26, Fig. 1), from Komori, internal mould, somewhat secondarily compressed
H. ITO'S private collection (PI. 23, Fig. 1),
from Minato, secondarily deformed
KU. JM1l321 (PI. 25, Fig. 2) and KU. JM
11322 (PI. 25, Fig. 1), both from Anaga,
internal mould (collector unrecorded)
KU. JM1l323, retroversal last part of bodychamber and another unnumbered specimen (body chamber) for general education (no record of colI.)
NSM. PM7385, from Nakano, collected by
K. SABURI, T. SAWAKI and T. OTA(1972-5-4)
YCM. GP557, from Anaga, collected by
Y. Y ASUI, deformed as in H. ITO'S collection
GK. H. 5913, collected by Y. MAEDA, from
MinatoThere are many other specimens in thecollection of H. HASHIMOTO from the
Naruto area, but they are mostly deformed.
Other fragmentary specimens from A waji
island (Minato, Anaga, etc.) are omitted
from the list.
Diagnosis :-The phragmocone is nearly
planispiral, consisting of polygyral, evolute
whorls, which are circular in cross-sectionand enlarge rather slowly. The bodychamber at first follows the coiling of thephragmocone for nearly or slightly morethan a quarter whorl, then is gradually
separated from the coiled part to form a170

Tatsu1'o MATSUMOTO et al.

gently sigmoid arc and finally twisted toform a retroversal hook of U- or rather
C- shape. The last part of the bodychamber is subelliptical and higher thanbroad in section, with the aperture facing
obliquely upward to the venter of theearly part of the body-chamber. The
entire shell, thus, seemingly takes a Sshape, whose length is normally 225-240mm and the diameter of the coiled partat the last septum 130-140 mm. Occasionally the dimensions may deviate fromthese normal values (see remarks).
The shell is ornamented with numerous
radial ribs and two rows of tubercles.
The ribs on the whorls of early growthstages are rather coarse, separated bywider interspaces; and all or alternate
ribs are provided with ventrolateral tubercles. On the rest of the main part ofthe shell the ribs are numerous, dense
and gently flexuous, while the tubercles
occur rather irregularly at every third or
fourth rib or sometimes at every fifth or
sixth. On the earlier shaft of the hooked
part the rows or tubercles are shifted inaccordance with the twisting of the bodywhich finally takes the position of its
hyponome (i. e. venter) on the outer (i. e.
external) part of the hook. Along withthe shifting, one row of the tubercles on
the twisted portion may be bullate andweakened or even obsolete, but on thelast part of the hook the tubercles in two
rows become again distinct and aresituated at the ventrolateral shoulders,occurring at every fourth to second rib
and finally at every rib. On this andearlier parts the ribs form loops at sometubercles. The tubercles are nodose at
the base and shortly spinose at the top,
except for the weakened bullate ones
mentioned above.
Periodic shallow constrictions occur at
irregular intervals. There is a flared ribat the last constriction, in front of which
there are two or three dense ribs without
tubercles. This last portion is slightly
narrower than the preceding part. The
apertural margin is rather simple, with apair of shallow (probably ocular) sinuses
at the inner lateral corner.
Suture is quadrilobate, consisting of E,
L, U and I, which are finely and deeply
incised, leaving narrowed stems. All theelements, except I, are bifid. L is thelargest, and U somewhat smaller than L
but may have a broader stem; E and I
much shorter than the adjacent L or U.
Remarks:- The S-shaped shell-form isfairly constant among the individuals
examined. Even the shape of the retroversa I hook does not vary much.
The variation in size is significant. Oneof the specimen examined (OMNH. M2178,
PI. 23, Fig. 2) is exceptionally small,measuring 184 mm in length of the Sform, whereas larger examples, as represented by the NANKO'S specimen (PI. 24,
Fig. 3) and KU. JM11322 (PI. 25, Fig. 1),
measure 284 mm and 295 mm in length
respectively. Examples of normal size arerepresented by OMNH. M2177 (PI. 22, Fig.
1) (L=235 mm), GLKU. IZ-80003 (PI. 26,
Fig. 1) (L=225 mm), KU. JM11321 (PI. 25,
Fig. 2) (L=238 mm) and several others.

Explanation of Plate 22
Fig. 1. Pravitoceras sigmoidale YABE
OMNH. M2177, fairly well preserved specimen \yith test, from Minato, Awaji island (coIl.
A. MATSUOKA).
Lateral (a), frontal (b) and lower (c) views, x 2/3(All the photos of PIs. 22-26 by Y. MOROZUMI)MATSUMOTO et al.:Pravitoceras sigmoidale

Plate 22

1b

735.

Pr avitocems sigmoidal e Y ABE

T ext ·fig. 1. Sketch of Pravitoceras sig11loidaie Y ABE . Latera l v iew of OM NH.
M2177 (see PI. 22, Fig. la) . S : Position of the las t sept um.
Y. M O RO Z UM I D E LI N .

171

172

Tatsuro MATSUMOTO et al.

Therefore, the exceptionally small individual mentioned above is not the microconch of a dimorphic pair, but probably
an individual dwarf.
For some reasons the initial stage is
not preserved in any specimen listed under
Material. There are, however, two small
specimens with helical coiling embeddedin the same nodule as OMNH. M2177 and
OMNH. M 2178. Possibly they represent the
young stage of the present species. Pending a conclusion, we will describe themin an appendix under a separate heading.
The main part of the phragmocone
sometimes shows a nearly but not strictly
planispiral coiling. Whether this is reminiscent of a very low helical coiling oran effect of secondary deformation is notdetermined with certainty. Possibly there
could be variation from a very low helicalcoiling to strictly planispiral one in thisstage. Anyhow, the whorls are just touching in the main part of the phragmocone.
In the observable early part of thephragmocone the ribs are comparatively
coarser than the rest main part. This
coarsely ribbed stage continues for avariable duration, sometimes up to 30 mm
or so in diameter but in other times up
to 50 mm. In this stage the ribs number
5 or 6 within the interval as large as thewhorl height. In later stages the ribs aredenser, numbering 10 to 12 in the sameinterval. They are simple for the mostpart, except for looping at some tubercles.
In the strongly curved portion of the bodychamber, intercalated or branched shorter

ribs may occur. The ribs along the constriction are somewhat stronger thanothers.
The tubercles vary in strength andfrequency with growth and also amongindividuals, but we have not seen any
specimen which has no tubercle at all,although YABE'S (1902, 1915) descriptions
may have given the mistaken idea that
there were some individuals without tubercle. In fact, IGPS. 4524, from Toyajo(Wakayama Prefecture), which was described by YABE (1915, pI. 3, fig. 1) as an
example of Pravitoceras sigmoidale, has
no tubercles. It is unusually large, about
190 mm in diameter of the coiled part,and the ribs are denser and more numerous than in unmistakable specimens of
P. sigmoidale. It is probably a coiled partof a Diplomoceras sp. which is allied to,
if not "identical with, "D. notabile (WHITEA VES)" of KILIAN and REBOUL (1909,
pI. 5, fig. 1) [=D. lambi SPATH, 1953J.
Another specimen of YABE (1915, pI. 2,
fig. 1), from Anaga, does have ventrolateral tubercles on the last part, although
they were somewhat eroded. It is aslarge as and shows nearly the same shape
as KU. JM1l323, being regarded as the
body-chamber (later part) of a comparatively larger individual.
When we look at carefully the positionof the two rows of tubercles on the twistedpart of the body-chamber, we notice that
there are two forms, which can be called
dextral, as represented by OMNH. M2177(PI. 22, Fig. 1), and sinistral, as represented by GLKU. IZ-80003 (PI. 26, Fig. 1),

Explanation of Plate 23
Figs. 1, 2. Pravitoceras sigmoidale YABE
1. H. ITo's ColI., fairly deformed shell, from Minato, Awaji island. Lateral view, x2/3.
2. OMNH. M2178, exceptionally small shell with the length of 184 mm, from Minato (colI.
A. MATSUOKA). Lateral view, x 2/3.

MATSUMOTO et al. :P1·avitoceras sigmoidale

Plate 23

7'35.
Table 1.

Pravitoceras sigmoidale Y ABE

173

Measurements (in mm) of Pravitoceras sigmoidale.
(1)

(2)

(3)

(4)

(5)

(6)

(7)

(8)

OMNH. M2177

235.0

117.0

39.2*

35.0*

132.0

77.0

30.0

31. 0

~110. 057.0

Specimen

OMNH. M2178

185.0

87.0

34.0

NANKO'S

284.0

130.0

42.0**

GLKU. IZ-80003

225.0 -110.0

KU. ]M11321

238.0

115.0

40.0

KU. ]M11322

295.0

144.0

48.0

144.0

46.0

KU. ]M1l323

39.0**

154.0

94.0

35.-

123.0

74.0

29.0

-142.0

79.0

33.0

160.0

90.0

38.0

33.5

(1) length of S·shape [L], (2) width of U· or C·shape of the body·chamber, (3) height of
the last shaft, (4) breadth of the last shaft, (5) diameter of the shell at the last suture,(6) umbilicus, (7) whorl-height, (8) whorl-breadth at the same position.
* 42.0 and 36.0 near the apertural end** 51.0 and 37.0 at the apertural end

Seto Inland Sea

o....
5km
' ---'-----'''---"'---'-....,j,
Text-fig. 2. J\!ap showing the localities of Pravitoceras sigmoidale (with solid black
circle) and those of Didymoceras spp. (with empty circle). Inset at the upper left corner
is an index map, in which the dotted area indicates the distribution of the Izumi Group.

174

Tatsuro MATSUMOTO et al.

respectively.
Occurrence,' - The localites where wehave confirmed the occurrences of thisspecies are as follows (Text-fig. 2):(1) Minato (about 2 km southwest fromthe streets of Minato).
a. The fossils occur mostly in calcareous nodules within a nearly 10 m unitof fine sandy shale. OMNH. M2177 and M
2178 were found within the same nodule
together with several poorly preserved onesof the same species and Solenoceras (Oxybeloceras) d. humei (DOUVILLE). Several
shells of Anomia (?) sp. are attached tothe shell of P. sigmoidale. This unit isprolific and most of the specimens inprevious collections with locality record"Minato" may have come from here.
b. The described specimen of NANKO'S
CoIl. came from the unit of alternating
shale and sandstone immediately below
the above described unit (a). (a) and (b)both belong to the Minato Shale Memberin the lower part (above the Tsui Basal
Conglomerate) of the Izumi Group (SASAI,
1936).
(2) Anaga (about 1 km northwest of the
Anaga harbour). The fossils occur in the
sandy shale with some interbeds of sandstone. This part belongs to the upper partof the Minato Shale. Didymoceras spp.
have been found in the underlying partof the shale exposed on the tidal zone of
the coast.
(3) Nakano, southern part of Tsui. At

the point indicated by empty circle wehave found Didymoceras sp. According
to the locality record, NSM. PM7385 was
found, together with some other specimens, from another locality of Nakano
stratigraphically above this locality ofDidymoceras.
(4) Uchihara, Tsui, half way between(1) and (3).
Fragmentary specimens.
These four localities are in the southwestern part of Awaji island.
As has been recently made clear (SuYARI, 1973; MATSUMOTO and MOROZUMI,1980) in Shikoku and in the Izumi Mountains, the lower shale member of the
Izumi Group is eastward time-transgressive. The same relationship would probably be applied to the Minato Shale in
the island of A waji. In other words the
Subzone of Pravitoceras sigmoidale runs
through different lithological subdivisonsof the Minato Shale from southwest tonortheast.
In the area belonging administratively
to Naruto City at the northeastern cornerof Shikoku, several localities of Pravitoceras sigmoidale have recently been foundat first by Mr. SHINOHARA and then by
one of us (H. H.). They belong to themember of a turbidite facies consisting ofshale, sandstone and conglomerate, whichlies on the shale member, i. e. the lithostratigraphic (but diachronous) extensionof the Minato Shale (BANDO and HASHIMOTO, 1981).

Explanation of Plate 24
Figs. I, 2. Pravitoceras sigmoidale Y ABE (juvenile) (?)
1. OMNH. M2179, sinistrally coiled shell, from Minato, Awaji island (colI. A. MATSUOKA).
Apical (a), basal (b) and three lateral (c, d, e each 90° rotated) views, x 2.
2. OMNH. M2180, dextrally coiled shell, from Minato (colI. A. MATSUOKA).
Upper (a) and two lateral (b, c 90° rotated) views, x 2.
Fig. 3. Pravitoceras sigmoidale Y ABE
S. NANKO'S ColI., internal mould of a large example from Minato.
Lateral (a) and frontal (b) views, x 1/2.

MATSUMOTO et al.:Pravitoceras sigmoidale

1a1cPlate 24

2a

1b

1d

1e

2b

2c

735.

Pravitoceras sigmoidale Y ABE(5) Omoi-zaki, Seto (northern part of
Naruto). Several deformed specimens of
P. sigmoidale were embedded in school inthe sandstone and also the shale of theturbidite facies. There are two otherlocalities on the coast to the west of
Omoi-zaki.
(6) Komori (a pit), Oasa (eastern partof Naruto). Here alternating sandstoneand shale are exposed. GLKU. IZ-80003
was clinging to the top surface of a turbidite sandstone. Some other examples
were found in the shale and the sandstone.
(7) Shimoda (about 2.5 km west of Komori), Oasa. Again from the sandstone
and the shale of the turbidite facies.
(8) Hidono-dani (about 1 km northwestof Shimoda). An impression of Pravitocerason the top of a sandstone bed.
In the northwestern branch of theBando-dani (western part of Oasa), there
are localities with Didymoceras awajiense.
They are of lower stratigraphic level than
the Pravitoceras bearing part. Still westward, i. e. at still lower levels than the
Didynwceras-bearing beds, there are localities with Baculites kotanii MATSUMOTO,HASHIMOTO et FURUICHI and then Metaplacenticeras subtilistriatum (jIMBO) (seeMATSUMOTO et aI., 1980). On the other
hand, at a locality in Naruto, SUYARI(1973) recorded Inoceramus (Endocostea)
shikotanensis NAGAO et MATSUMOTO, an
index of the lower Upper Hetonaian[K6b1J. This locality is stratigraphicallyhigher than the Pravitoceras-bearing beds.
In short, Pravitoceras sigmoidale occurs
characteristically in a limited part within
the thick sequence of the Izumi Group in
the island of A waji and in northeastern
Shikoku. It represents a local subzone in
the uppermost part of the Lower Hetonaian Stage [K6aJ of the Japanese scale,i. e. the approximate correlative of the Campanian in terms of the international scale.
This species, however, has not yet been

175

found in Hokkaido, where the reference
scale of the Hetonaian [K6J (the approximate correlative of the Campanian plus
Maastrichtian) has been established.
Affinity: -Pravitoceras sigmoidale isunique in its S-shaped shell-form. Its
retroversal body-chamber with evidence ofa twisted, instead of a simply hooked body,
two kinds of coiling which correspond to
dextral and sinistral, mode of ribbing,bituberculation and particular pattern ofsutures, as well as the stratigraphic occurrence, suggest that it was probably
derived from a species of Didymoceras,
with lowering of the helical phragmocone.
The ancestor is probably D. awajiense(Y ABE). There seem to be more than
one species of Didymoceras in the unit
underlying the Subzone of P. sigmoidale.
D. awajiense needs revision. So far, wehave noticed some variation (e. g. in themode of retroversion from the helical part)in D. awajiense but we have not yet
obtained an example which could be
regarded as precisely transitional. In
other words, at least seemingly P. sig11loidale appeared rather suddenly.
So far as the available evidence is concerned, Pravitoceras sig11loidale is endemic
and has a short vertical range, without
leading to a descendant. At present itis the monotypic representative of thegenus.
In short, Pravitoceras has an evident
affinity with Didymoceras and should be
assigned to the family Nostoceratidae. It
is probably a short, dead-end offshootfrom Didynwceras. An analogous, if not
identical, form of coiling is shown by
Nostoceras (Planostoceras) LEWY, 1967,
which also is a member of the Nostoceratidae.
Further remarks
We attempt here to give preliminary

176

Tatsuro MATSUMOTO et al.

remarks on the habitat and the mode oflife of this peculiar ammonite.
Pravitoceras sigmoidale has a fairly long
dody-chambdr. Should the U-shaped partbe assumed to follow the normal coiling,
the body-chamber would occupy almost afull whorl. In the case of evolute ammonites of normal coiling, the bodychamber is generally long, occupying
nearly a full whorl or more to take thefavourable condition of buoyancy. In thisrespect there is no significant difference
between Pravitoceras and normally coiled,evolute ammonites, although the centerof buoyancy must be at different position.
As to the center of buoyancy Pravitoceras
may be comparable to but not quite identical with Macroscaphites, since in Pravitoceras the last quarter of its coiled partis occupied by a part of the body-chamber.
Although we mention the body-chamber,the buoyancy is concerned with thephragmocone in proportion to the entire
shell.
The aperture of the retroversed bodychamber is facing fairly closely to theventral surface of the last part of thecoiled whorl. The space to produce thefunnel and tentacles must have been
limited and these frontal part of the body
were so situated that they were normallyconcealed or protected underneath themain part of the shell. In other words,
Pravitoceras in the adult stage may havebeen less active than most of the normallycoiled ammonites.
There is, however, sufficient space tolet the water stream out from the funnel
at the outer portion of the shell aperture.
Therefore, Pravitoceras may have beenable to swim, when necessary. Judging
from the position of the last septum andthat of the aperture, Pravitoceras may
have moved with its curved part of U
forward, although locomotion may havebeen slow. Normally its S-shape was not
upright but must have been in some oblique attitude.
Fossils of Pravitoceras are found often
in groups from the same bed or evenfrom the same nodule. If we take this
into consideration, together with thepeculiar shell-form and the less activity
mentioned above, we can presume that
Pravitoceras took primarily a benthic
mode of life and that it may have moved
in the water occasionally. At what depthof the sea bottom the animal preferred
to live is a problem yet to be worked out,
but the finely and deeply incised suturesuggest that the favourable condition
may not have been so shallow. Thismay be compatible with the particularnature of the sedimentary trough of the
Izumi Group, as discussed by TANAKA(1965).
AppendixPossibly juvenile shell of Pravitoceras
Two tiny specimens of helical coilingare embedded in the same nodule as
OMNH. M2177 and M2178, unmistakable

Explanation of Plate 25
Figs. 1, 2. Pravitoceras sigmoidale YABE
1. KU. ]M11322, internal mould of another large example, from Anaga, i\waji island.
Lateral view, x 0.45.
The specimen is so fragile that the shell is surrounded with cement.
2. KU. ]M11321, incomplete internal mould, from Anaga.
Lateral view, x 1/2.

MATSU MOTa et al.:Pravitoceras sigmoidale

Plate 25

735. Pravitoceras sigmoidale Y ABE
adult specimens of Pravitoceras sigmoidale. They are described here, as wehave mentioned in remarks of the maintext.
Pravitoceras sigmoidale Y ABE(juvenile) (?)
PI. 24, Figs. 1, 2; Text-fig. 3

Material :-OMNH. M2179 and OMNH.
M21S0, obtained by A. MATSUOKA from
Minato.
Description :-OMNH. M2179 (PI. 24,
Fig. 1) is sinistral and OMNH. M21S0 (PI.
24, Fig. 2) dextral. The former is better
preserved. It shows rather low helicalcoiling with a slight overlap of the whorls.
It is 10.3 mm in diameter and S.2 mm inheight, although the very initial stage isun preserved. The observable earliest part
below 5 mm in diameter is smooth. The
succeeding main part is ornamented withribs which are separated by wider interspaces. There are 25 ribs per whorl.
They are mostly simple, somewhat flexuous, but branching occur occasionally(4 times within the last whorl preserved)
on the basal surface. Every rib is bituberculate; the tubercles of the upper row
are distinctly visible on the side and thoseof the lower row are weak and discernible on the basal surface. The whorl issomewhat angulated at the tubercles.

177

OMNH. M21S0 is somewhat taller than
OMNH. M2179, about 9.5 mm in diameterand 9.0 mm in height (of the helix).
Again the observable first stage is smoothand the rest main part is ornamented
with the same type of ribbing and bituberculation as OMNH. M2179.
Remarks:- The mode of ornamentation
described above is similar to that of theobservable early part of unmistakablespecimens of P. sigmoidale described in
the main text.
It is too bad that we have not yet
obtained a good specimen which shows
both the very early part as large as theabove two examples and also the mainpart of P. sig71loidale. KU. JM1l321,
however, seems to suggest that theearliest part may be helical.
DidY7710ceras spp., including D. awaiiense, occur commonly in the subzone
below the Subzone of P. sigmoidale, but
we would not deny the possibility thatsome species of Didymoceras or Nostoceras
could be found, although rarely, together
with P. sigmoidale. In other words, thetwo tiny specimens described here might
be early parts of Didymoceras sp. or
Nostoceras sp. We should search forbetter preserved specimen to give thefinal decision. Unmistakable examples of
Nostoceras are actually found at higher
levels (see MATSUMOTO and MOROZUMI,
19S0).
References Cited

a

1 ern
Text-fig. 3. Sketch of a possibly juvenile
shell of Pravitoceras sigmoidale Y ABE. Lateral(a), upper (b) and basal (c) views of thehelical shell, OMNH. M2179 (see PI. 24. Fig.
Ie, a, b). Y. MOROZU~1l delin.

BA:-'-DO, Y. and HASHIMOTO, H. (1981): Noteon the Izumi Group (Upper Cretaceous) inthe eastern part of the Asan Mountain
Range. Mem. Fac. Educ., Kagawa Univ.,
part 2, vol. 31. (in press)
KILlAi\", W. and REI30L:L, P. (1909): Les cephalopodes neocretaces des lIes Seymour et
Snow Hill. Wiss. Ergebn. Schwed. SudPol. Exp. 1901-3, vol. 3, no. 6, p. 1-75,
pIs. 1-20.

Tatsuro MATSUMOTO et al.

178

LEWY, Z. (1967): Some late Campanian nos·
toceratid ammonites from southern Israel.
Israel jour. Earth Sci., vol. 16, p. 165173.
MATSUMOTO, T., HASHI:VIOTO, H. and FURmCHI, M. (1980): An interesting species of
Baculites (Ammonoidea) from the Creta·
ceous Izumi Group of Shikoku. Proc.
japan Acad., vol. 56, ser. B, p. 408-413.
MATSUMOTO, T. and MOROZUMI, Y. (1980):
Late Cretaceous ammonites from the Izumi
Mountains, Southwest Japan. Bull. Osaka
Mus. Nat. Hist., no. 33, p. 1-31, pIs. 1-16.
SASAI, H. (1936): The Izumi Sandstone Series
in Awaji. jour. Ceol. Soc. japan, vol.
43, p. 590-602, pIs. 28-29 (in Japanese).
SPATH, L. F. (1953): The Upper Cretaceous
cephalopod fauna of Graham Land. Falkland lsI. Depend. Surv., Sci. Rep. no. 3,
p. 1-60, pIs. 1-13.
SUYARI, K. (1973): On the lithofacies andthe correlation of the Izumi Group of the
Asan Mountain Range, Shikoku. Sci. Rept.
Tohoku Univ., 2nd ser., Spec. Vol., no. 6,
p. 489-495 (in Japanese with English abstract) .
TANAKA, K. (1965): Izumi Group in thecentral part of the Izumi Mountain Range,
Southwest Japan, with special reference
to its sedimentary facies and cyclic sedimentation. Rept. Ceol. Surv. japan, no.
212, p. 1-34, pIs. 1-8 (in Japanese withEnglish abstract).
YABE, H. (1902): Note on three Upper Cretaceous ammonites from Japan, outside of
Hokkaido (continued). jour. Ceol. Soc.
Tokyo, vol. 9, p. 1-7, pI. 1.
- - (1915): Note on some Cretaceous fossils
from Anaga on the island of A waji and
Toyajo in the province of Kii. Sci. Rept.
Tohoku Imp. Univ., 2nd ser., vol. 4, no.
1, p. 13-24, pIs. 1-3.

*r6,

Anaga 1lPJ1JlI:t!l, Awaji
Bando-dani jjj[*:fr, Fukura t;N, Hidono-dani jljjj~:fr, Izumi fjJ;iR,
Komori 'H'*, Minato ~, Nakano {'!>!Il.f, Naruto ~1.l;r9, Oasa ::k)ff;, Omoi-zaki '\!!'JIF.f, Seto it!{p,Shimoda TEEI, Tsui ~j:j:, Uchihara rfj~
El!IE*C~m-;@;~7 :/-'f::j-1 I-

Pravitoceras sigmoidale YABE V:::'--:>O'L: *:fmO)~~:'lqt.

ltfT }h'8t-: -:> t-:b:, :to)f&tr<~ ~ tct-:~*v:::.*f¥O)N o'o)b;~7.>
tc G~~1f; L, :fmO)~~cJl'~~Lt-:o ;:: < fJJltlHt.:tLf*!ijlntU':-:>t-:G LH1tf4b;~7.>o :to)ml7tcfiYi~;g~O)fJJM-C:'ft., JlJJ
b:t§Mi¥Jvcffl.<, %JlJJv:::'~J8lb:~7.>o i±mft.:Ili:<, fJJObfi~;g~~~vt, l'Xo'-c:'~Hf.[[~@i~t.(:b; GlXf*mlft.:i;l Ctc, 1&J!ili" 7.>O)~ I) 7Jv:::.::(:j;g ~tc:;gv:::.t§ ~i" 7.> 2 ~b:~:ZOb Gtc7.>271j0)~J8lvt.!Jifj/JtvVG!IH{ljt.(:ii: G c· O)~*v:::' t ;5 I), :i;l Ctc 7.> ml7t-c:'vt.1iI17ti¥Jv:::.:g).htct.(: 0' ;:: C
b:~7.>o *:fmfi*~et;O)mg§mI ~ ~oo~t:lIr1mO)jflUR~ll'f 0) TmI 0) -n:~& (Didymoceras
awajiense !IE*O)i" <-1:&) vOflfi!!&i¥Jv:::.i!il'L, Lfi Lfill'f1=.i" 7.> 7J:/ /{ =- 7 :/:/&1:mlO)!IE*~1f;i"o Pravitoceras vi Didymoceras ii, G83* L t-: C m~ L, Nostoceratidae v:::'Atct-:o
tdo1=.f.§t!R:;:!;;v:::. --:>O'L t ~~~Bit""ko
0

0

;::

;::

0

0

Explanation of Plate 26
Fig. 1. Pravitoceras sigmoidale YABE
GLKU. IZ80003, internal mould, from a pit at Komori, Naruto City, northeastern Shikoku(colI. I. SHINOHARA).
Lateral view, 2/3.

MATSUMOTO

et al.:

Pravitoceras sigmoidale

Plate 26

Trans. Proc Palaeont. SOl". japan. N. S., No. 123, pp. 179-185, pIs. 27-29, September 30, 1981

736.

THREE SPECIES OF LITHOSTROTION FROM THE ICHINOTANIFORMATION (UPPER PALEOZOIC CORALS FROM FUKUJI,
SOUTHEASTERN PART OF THE HID A MASSIF, PART 5)*
HISA YOSHI IGO and SHUKO ADACHI
Institute of Geoscience, The University of Tsukuba, Ibaraki 305

Abstract. The Lower ~'Iember of the Ichinotani Formation distributed in Fukuji,
Gifu Prefecture yields many well.preserved corals. We describe three species of
Lithostrotion, such as Lithostrotion (Lithostrotion) decipiens (M'Coy) , L. (Sip/wno.
dendron) nipponalpinum IGO and ADACHI, n. sp. and L. (S.) hidense IC\TO yieldedfrom the Lower Member of the Ichinotani Formation. These corals indicate Late
Visean in age, but L. (L.) decipiens extends to slightly upper levels characterized
by the Lower Namurian microfossils.

YD, Palaeosmilia murchisoni EnvVARDS and
HAl ME, Lithostrotion (5iplzolJodendron)hidense KATO, Neokoninckophyllum nipponense KATO, Lonsdaleia duplicata (MARTIN), "Chienchangia" minatoi (KATO), Carcinophyllum lonsdaleiforme SALEE andothers.
Besides them, there are some undescribed coral species in IGO'sCO llection.
We describe two species of Litlzostrotion(s.l.) and redescribe L. (5.) hidense KATO
came from the Lower Member of the
Ichinotani on this occasion.
A large colony of Lithostrotio71 (Litlzostrotion) decipiens (M'Coy) was found fromthe upper part of Unit 1 (lGO and ADACHI,
1981). This colony is hemispherical tomound-like and attains 50 to 70 cm indiameter. Small gibbous colonies of thesame species, about 10 to 20 cm in diameter, were also obtained from this leveland slightly higher levels of Unit 2. Someof the specimens came from Unit 2 aresilicified.
Lithostrotion (5iphonodendron) nipponal-

Introduction
The Ichinotani Formation distributed in
Fukuji, Kamitakara Village, Yoshiki County, Gifu Prefecture consists mainly offossiliferous limestones and intercalated
thin shales. Stratigraphical and paleontological studies of this formation weredone by IGO (1957 and others). He elucidated that the formation is one of themost complete sequences ranging from theuppermost Lower Carboniferous to thebasal Permian in the Japanese Islands.
Coral faunas of this formation were reported by KAMEl (1957), MINA TO andKATO (1957), FUJIMOTO and IGO (1958),
KATO (1959), IGO (1958, 1959, 1961),
KATO and NIIKAWA (1977), NIIKAWA(1979),
and IGO and ADACHI (1980). Corals arecommonly yielded from various levels of
the Ichinotani Formation, but these areparticularly prolific in the lower part of
the Lower Member. Characteristic corals
from this unit are Kueichouphyllulll sinense* Received Marrh 26, 1981

179

180

Hisayoshi leo and Shuko ADACHI

pinum IGO and ADACHI, n. sp. was obtained from almost the same level with
Lithostrotion (L.) decipiens of Unit 1.
This new species is represented by afairly large colony that was collectedalong with Syringopora. This colony isplaty in shape with the length of 50 cm,
width of 30 cm and height of 20 cm.
Lithostrotion (Siphonodendron) hidense
KATO was found in Unit 1 as a rather
small colony.
As already discussed by the aforementioned authors, Unit 1 yielding thesecorals is correlated with the Upper Visean
based upon the various paleontological
data. Lithostrotion (Lithostrotion) decipiens
is also yielded from Unit 2 that is characterized by the occurrence of Lower
Namurian conodonts and smaller foraminifers. The present paper is a new additional contribution to our serial study of
the Upper Paleozoic corals from Fukuji.
Systematic Descriptions
Order Rugosa EDWARDS
and HAl ME, 1858
Family Lithostrotionidae
GRABAU, 1927
Genus Lithostrotion FLEMING, 1828
Subgenus Lithostrotion FLEMING, 1828

Li thost rotiol! (Lit host rotion) decipiens(M'CoY, 1849)
PI. 26, Figs. 1-3, Text-figs. la-d.

Lithostrotion decipiens, ED\\'ARDS and HAIME,
1851, p. 441; HILL, 1940, p_ 178-180, pI.
10, figs. 2-4, 5?, 6?; FAN, 1974, p. 267, pI.
136, figs. 14, 15; ZAHANG, 1977, p. 193,
pI. 75, fig. 6; WANG, 1978, p. 127, pI. 37,
fig. 5.
Petalaxis portlocki, EDWARDS and HAIME,
1851, p. 453 ; EDWARDS and HAIME, 1852,
p. 204, pI. 38, figs. 4, 4a; EDWARDS andHAIME, 1860, p_ 441; SEMENOFF-TIANCHANSKY and NUDDS, 1979, p. 255, pI. 1,
figs. 6, 7; pI. 4, figs. 4, 5.
Stylaxis portlocki, EDWARDS and HAIME, 1851,
p.453.
Lithostrotion portlocki, GORSKY et aI., 1975,
p. 85, pI. 26, fig. 3; ZAHANG, 1977, p. 194,
pI. 72, fig. 2; WANG, 1978, p. 128, pI. 38,
fig. 1.
Lithostrotion heptagonale KAMEl and iGO(MS) nomen nudum, (n FUJIMOTO and iGo,
1958, p. 159, 162, (listed).

Corallum compound, cerioid, large, hemispherical to mound-like in shape and attains about 50 to 70 cm in maximum diameter.
Corallites are unequal in size, about 5.0
mm in average diameter. Large corallites attain 8.5 mm in diameter. Maturecorallites are mostly heptagonal or hexagonal in transverse sections. New corallites arise at corner of mature corallites
and have three or four sides. In marginal
part of corallum, corallites are frequently
circular in transverse sections, phaceloid
as in Siphonodendron. Corallite wall israther thin and straight.
Septa are of two orders, major andminor. There are 15 to 17 septa of eachorder in mature corallites. Septa are moreor less stroflgly thickened by secondary

Explanation of Plate 27
Figs. 1-3. Lithostrotion (Lithostrotion) decipiens (M'Coy)
1. Transverse section of a partly silicified specimen collected from Unit 2, IGUT 5364, x 4.
2. Transverse section of a specimen collected from Unit 1;
3. Longitudinal section of the same specimen as 2, iGUT 5363, x 4.

Jeo and ADACHI:

Three species of Lithostrotion

Plate 271

736.

Three species of LithostrotioncdText-figs. la-d. Lithostrotion (Lit;wstrotion) decipiells (M'Coy)la, ld. Transverse sections;lb, lc. Longitudinal sections, IGUT 5363,
scale bar 0.5 cm.

deposits. Major septa are long, straightor slightly flexuous. Counter septum
usually joints with columella. Some ofmajor septa are occasionally discontinuousin dissepimentarium. Minor septa areslightly shorter than major septa in fullygrown corallites, but 3/4 or 1/2 as longas major septa in young corallites.
Columella is continuous with counter
septum and some major septa, elongate
elliptical in transverse sections. Dissepi-

181

mentarium occupies about or slightly more
a half radius of corallites. Dissepiments
are rather large, arranged in two or threerows, rarely one row, facing upwards but
those of inner series are facing inwards.
Tabulae are of two series, inner andouter. Inner ones are steeply arching andreinforcing axial structure. Outer ones
are narrow and mostly concave but rarely
flat.
Comparison: -The present specimens
are similar to the specimens which wereidentified by many authors with both
Lithostrotion port/oclli (EDWARDS and
HAIl\IE) and Litlwstrotion decipiens(M'Coy).
Recently, SEMENOFF-TIAN-CHANSKY andNUDDS (1979) pointed out that the former
species is considered to be a synonym of
the latter species based upon the detailed
observation of the type specimen preserved at Institut de Paleontologie, Museum
national d'Histoire naturelle, Paris.
The present form resembles the lectotype of Lithostrotioll decipiens (M'Coy)
which was fully described by HILL (1940).
However, the former has more commonly
heptagonal corallites and fewer series ofdissepiments than the latter. Lithostrotion
decipiens described by WANG (1978) from
Guzihou, Southwestern China is very
similar to the present specimens, but the
Chinese specimens have horizontal tabulaeand more numerous rows of dissepiments.
Lithostrotion port/oelli introduced from thesame district resembles the present specimens, but the latter has larger corallites
and longer minor septa than the former.
Lithostrotion decipiens described by FAN(1974) is also similar to the present form.
Lithostrotioll po rt/oell i described from
Urals by GORSKY et al. (1975) is also
related with our present ones.
Occurrence :-Upper level of Unit 1 andthe middle level of Unit 2, Lower Memberof the Ichinotani Formation.
Reg. nos. IGUT 5363-5367.

182

Hisayoshi IGO and Shuko ADACHI

Subgenus Siplzonodendron M'CoY, 1849

Litlzostrotion (Siplzonodendron)nipponalpinwll IGO and ADACHI, n. sp.
PI. 27, Figs. 1, 2, Text-figs. 2a, b.

?Lithostrotion proliferum (THOMSON andNICHOLSON), DOBROLYUBOVA, 1958, p. 158160, pI. 24; DOBROL YUBOV A and KABAKOVITSH, 1966, p. 160-163. pI. 31, figs. 2-5,
pI. 33, fig. 1.

Corallum fasciculate, dendroid to phaceloid and its external shape is platy withlength of about 50 cm, width of 30 cm andheight of 20 cm. Corallites closely arranged and often in contact. Corallite
wall is rather thin and has no pronounced
septal grooves.
Diameter of corallites is variable, ranging from 4 to 16 mm, but in most of corallites is 8 to 9 mm. Septa are of twoorders, major and minor. Number of

Text-figs. 2a, b. Lithostrotion (Siphonodendron) nipponalpinum IGO and ADACHI,
n. sp.
2a. Transverse section of the holotype;2b. Longitudinal section of the holotype,
IGUT 5368, scale bar 0.5 cm.

septa is also variable according to corallite diameter, 18 to 20 each in diameterof about 5 mm; 21 to 29 in 7 to 9 mm ;36 to 41 in 15 to 16 mm. The third ordersepta very rarely and sporadically appear
in some large corallites.
Major septa are straight or flexuous,
subequal in length, attain about one half
radius of corallite. Counter septum islonger than other major septa and sometimes connected with columella. Minor
septa are short, about 2/3 length of major
septa, and alternate with major septa.
Columella is simply constructed, thin andlath-shaped, anastomosed by axially elevated tabulae. It is straight or sinuous
in longitudinal sections.
Dissepimentarium is narrow, consists ofvarious-sized two rows of dissepiments.
Three to five rows of dissepiments are
partly appeared in some large corallites.
They are gently inclined facing inward
as well as upward. Two series of tabulae
are present. Outer peripherial ones are
narrow and horizontal. Inner ones comprise mostly complete, conical to gently
domed series, and are rather densely disposed, 9 to 10 in distance of 5 mm.
Comparison:- This new species is similar to Litlzostrotion (Siplzonodendron) affine(FLEMING) which was fully redescribedby KATO (1971). He further noted thatthe species is a senior synonym of wellknown species, Litlzostrotion (Siplzonodendron) proliferum (THOMSON and NICHOLSON) reported from Europe and Asia.
The present species differs from Litlzostrotion (Siplzonodendron) affine in having moreclosely disposed corallites, larger corallites, more strongly arched tabulae andExplanation of Plate 28
Figs. 1, 2. Lithostrotion (Siphonodendron) nipponalpinum iGO and ADACHI, n. sp.
1. Transverse section of the holotype, IGUT 5368, x 2.
2. Longitudinal section of the holotype, IGUT 5368, x 2.

leo and ADACHI: Three spec?,es of Lithostrotion

Plate 28

1

2

736.

Three species of Lithostrotion

183

fewer series of dissepiments. It also
closely resembles Lithostrotion (Sip/wnodendron) proliferum described by DOBROL YUBOVA (1958) and DOBRoL YUBOV A andKABAKOVITSH (1966) from Soviet Union.
As already pointed out by KATO (1971),
these Russian specimens differ from both
Lithostrotion (Siplwllodendron) affine andL. (5.) proliferum. The present new
species slightly differs from these Russian
specimens in its shorter major septa andmore simply constructed columella, but
the Russian specimens seem to be thesame species with the present new species.
Occurrence :-Uppermost level of Unit 1,
Lower Member of the Ichinotani Formation.
Reg. no. IGUT 5368 (Holotype).
Lithostrotion (Siphonodendron) hidense
KATO, 1959

PI. 28, Figs. 1-3, Text·figs. 3a-d.

b

c

d

Siphonodendron hidense KATO, 1959, p. 277279, pI. 3, fig. 5; MI:-':ATO and KATO, 1957,
p. 548, fig. 2, (listed).
Lithostrotion asiatica Y ABE and HAYASAKA,
FUJI:-lOTO and leo, 1958, p. 159, 162,
(listed) .

Text-figs. 3a-d. Lithostrotion (Siphonodendron) hidense KATO
3a. Transverse section, IGUT 5369;
3b-d. Longitudinal sections, IGUT 5369,
scale bar 0.5 cm.

Corallum compound, fasciculate, dendroid to phaceloid. Increase of corallite
is lateral. Corallites are cylindrical, subparallel, rather closely arranged and occasionally in contact.
Corallites are circular to subcircular intransverse sections and 3.0 to 4.0 mm indiameter. Corallite wall is comparatively
thick for size of corallite and has distinct
septal grooves. Septa are in two orders.
Major septa are straight or slightly flexuous, long and 15 to 18 in number, reachcentral part of corallite, and some of themjoint with columella. Counter septum isusually continuous with columella. Minor
septa alternate with major ones. These

are slightly shorter than major septa andattain about 2/3 to 4/5 length of major
septa.
Columella is distinct, elliptical to thickfusiform in transverse sections and connected with counter septum and also withsome major septa. It is stout and straightor flexuous in longitudinal sections.
Dissepimentarium is narrow, composedof one or two, rarely three rows of subequal dissepiments. Their convex sides
are generally facing upward. Interthecal
dilation is developed along inner side ofdissepimentarium and forms inner wall.
Tabulae are rather densely disposed, mostly complete, gently arched to flat in longi-

184

Hisayoshi lco and Shuko ADACHI

tudinal sections. There are 8 to 10 tabulae
in a vertical distance of 2 mm.
Comparison: -The present specimens
have essentially identical biocharacterswith KATO'S holotype of L. (5.) Izidense,but their corallites are more separately
disposed. KATO'S specimens have two or
three rows of dissepiments, but our specimens generally have one or two rows ofdissepiments. Tabulae of our specimens
are more crowded than those of the holotype. KA TO listed several similar species
for comparison. Besides them, Litlzostrotion (5iphonodendron) cerifasciculatum Xu
which was described from ]unnan, South
China (in ZAHANG, 1977) is also similar tothe present species, but the Chinese species has fewer and longer major septathat extend to the columella, a wider dissepimentarium and less dense tabulae.
Reg. nos. IGUT 5369-5371.
Repository:-All specimens describedherein are kept at the Institute of Geoscience, the University of Tsukuba.
References Cited
DOBROLYUBOVA, T. A. (1958) : Lower Carboniferous colonial tetracorals from the Russian platform. Trudy Paleont. Inst., vol.
70, p. 1-216, pis. 1-38.
- - and KABAKOVITSH, N. V. (1966): Lower
Carboniferous corals of the Kuznetsk Basin.
Ibid., vol. 111, p. 1-276, pis. 1-45.
EDWARDS, H. M. (1860): Histoire naturelle desCoralliaires on Polypes proprement dits.
vol. 3, p. 1-560.
. - and HAIME, J. (1851): Monographie despolypiers fossiles des terrains paleozoiques.
Arch. Mus. Hist. Nat., Paris, vol. 5, p.

1-502, pis. 1-20.
- - (1852): Monograph of the British fossil
corals. pt. 3, p. 147-210, pis. 31-46.
FAN, Y. (1974): Corals; in Atlas of fossilsof Southwest China. Nanking Inst. Geol.
Pal., Acad. Sinica Ed., p. 265-275, pis.
134-139.
FUJIMOTO, H. and IGo, H. (1958): Stratigraphic position of the corals in the Ichinotani
Formation (Carboniferous), Fukuji district,Hida Massif, Central Japan. Proc. japan
Acad., vol. 34, p. 159-163.
GORSKY, I. I. et al. (1975): Tetracoral; in
Paleontological atlas of Carboniferous
deposits of Urals. STEFANOV, D. L. Eds.,
p. 1-358, pis. 1-100.
iGo, H. (1957): Fusulinids of Fukuji, southeastern part of the Hida Massif, Central
Japan. Sci. Rep. Tokyo Kyoiku Daigaku,
sec. C, vol. 5, p. 153-246, pis. 1-15.
- - (1958): On the occurrence of Koninckocarinia from the Ichinotani Formation.
jap. jour. Ceol. Ceogr., vol. 29, p. 209222, pis. 15, 16.
- - (1959): Note on some Permian corals
from Fukuji, Hida Massif, Central Japan.
Trans. Proc. Pal. Soc. japan, n. s., no. 34,
p. 79-85, pI. 8.
- - (1961): Middle Carboniferous corals fromthe Ichinotani Formation (Upper Paleozoic
corals from Fukuji, southeastern part of
the Hida Massif, Part 3). Ibid., n. s., no.
43, p. 127-137, pis. 18, 19.
- - and ADACHI, S. (1980): Two new interesting corals from the Ichinotani Formation (Upper Paleozoic corals from Fukuji,
southeastern part of the Hida Massif, Part4). Prof. S. KANNO Mem. Vol., p. 309316, pis. 36-38.
- - and - - (1981): Foraminiferal biostratigraphy of the Ichinotani Formation (Carboniferous-Permian), Hida Massif, Central
Japan. Part I-Some foraminifers from the

Explanation of Plate 29
Figs. 1-3. Lithostrotion (Siphonodendron) hidense KATO
1. Longitudinal section, IGUT 5369, x4.
2. Transverse section, IGUT 5369, x4.
3. Transverse section, IGUT 5370, x4.

leo and ADACHI:

Three species of Lithostrotion

Plate 29

2

1

3

736.

Three species of Lithostrotion

upper part of the Lower Member of the
Ichinotani Formation. Sci. Rept. Inst.
Geoscience, Univ. Tsukuba, sec. B, vol. 2,
p. 101-118, pIs. 4-6.
HILL, D. (1940): A monograph on the Car·
boniferous rugose corals of Scotland. Part
3. Paleontogr. Soc. (Monogr.) , p. 115204, pIs. 6-1l.
KA~IEI, T. (1957): Two Permian corals from
the Mizuyagadani Formation. jour. Shinshu
Univ., no. 7, p. 29-35, pIs. 1-4.
KATO, M. (1959): Some Carboniferous rugose
corals from the Ichinotani Formation,
Japan. jour. Fac. Sci., Hokkaido Univ.,
ser. 4, vol. 10, p. 263-287, pIs. 1-3.
- - (1971): J. FLE:-'IING'S species of British
Lower Carboniferous corals. Trans. Proc.
Pal. Soc. japan, n. s., no. 81, p. 1-10, pI. l.
- - and NIIKAWA, I. (1977): Kueichouphyl.
lum from Central Japan. Earth Science,
vol. 31, p. 243-249, pIs. 1, 2.
MI:"'IATO, M. and KATO, M. (1957): On the

185

Carboniferous coral zones at Fukuji, Gifu
Prefecture, Central Japan. Proc. japan
Acad., vol. 33, p. 547-552.
NIIKAWA, l. (1979): Carcinophyllum from the
Ichinotani Formation in Fukuji, Central
Japan. jour. Fac. Sci., Hokkaido Univ.,
ser. 4, vol. 19, p. 235-240, pI. l.
SE~·IE:\"OFF.TIA:\"-CHANSKY, P. and ~l'DDS, ]. R.
(1979): Revision de quelques especes deLithostrotion des iles Britanniques decrites
par MILi'E-EDWARDS et HAI~IE (Tetracoralliaires carboniferes). Bull. Mus. natn.
Hist. nat., Paris, 4e ser., 1, sect. C. n 0 3,
p. 245-283, pIs. 1-6.
WANG, H. D. (1978): Anthozoa; in Atlas offossils of Southwest China, Guzihou
Volume. Guzihou Inst. Geol. Pal. Ed.,
p. 106-187, pIs. 29-6l.
ZAHANG, T. (1977): Anthozoa; in Atlas offossils of South-central China, 2, Late
Paleozoic.
Hubei Inst. Geol. Sci. andother Ed., p. 109-241, pIs. 39-92.

-(7);frJii1i£: Lithostrotion '=::fil! (m!~ihl./:!tHJ¥.j*flIlm:!tHi£:G7)J:flIlil~3'f."lf" :/::t{r.E, .:c(7) 5) :-(7);frJii1TifflJii1g[G7) Lithostrotion .=:::ftJ!, Lithostrotion (Lithostrotion) decipiens (1\1'Coy),
L. (Siphonodendron) nipponalpinum [GO and ADACHI, n. sp., L. (Siphonodendron)hidense K.HO ~~c$,X: L. t~o ::.h G(7) -If" :/ ::z-f:t t: -l{ -t!tj~:Jt1l~mffii" Q ° L. (L.) deci piens
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ISHIJIMA Wataru (1980): On the Calcareous Algae from the
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Nagasaki Prefecture. Bulletin of the National Science
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5, No.4, pp.131-l37, Plates 1-4.
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Transactions and Proceedings of the PalaeontologicalSociety of Japan

New Series No. 123

September 30, 1981

CONTENTS
TRANSACTIONS
733.

NAKAI, Hitoshi: Silurian Corals from the Yokokurayama Formation in the
Mt. Yokokura Region, Kochi Prefecture, Southwest Japan-Part I. Haly-sitidae .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 139
734. Hu, Chung-Hung: Studies on the Ontogenic and Phylogenie Development of
two Upper Cambrian Trilobites from South Dakota .................... 159
735. MATSUMOTO, Tatsuro, MOROZUMI, Yoshiro, BANDO, Yuji, HASHIMOTO, Hisao
and MATSUOKA, Atsushi: Note on Pravitoceras sigmoidale YABE (Cretaceous heteromorph ammonite) .......................................... 168
736. IGo, Hisayoshi and ADACHI, Shuko: Three Species of Lithostrotion from the
Ichinotani Formation (Upper Paleozoic Corals from Fukuji, SoutheasternPart of the Hida Massif, Part 5) ...................................... 179