Bull. Tohoku Univ. Museum. No. 21, pp. 21‒38, 2022
© by The Tohoku University Museum

Middle Permian cephalopods of the Takakurayama
Formation in the Yaguki area, the southwestern margin of
the South Kitakami Belt, Northeast Japan
Masayuki Ehiro
The Tohoku University Museum, Sendai 980-8578, Japan
Abstract: Middle Permian coiled nautiloids and ammonoids are described from two horizons
belonging to the upper part of the Takakurayama Formation distributed in the Yaguki area,
Northeast Japan. The nautiloids consist of nine species belonging to four genera, and include one
new species: Tainoceras cf. abukumaense Hayasaka, Tainoceras sp., Pleuronautilus chisatoi sp.
nov., Pleuronautilus cf. gregarius (Miller), Pleuronautilus sp., Pleuronautilus? sp., Endolobus? sp.
and Domatoceras sp. The ammonoid fauna is composed of eight species belonging to eight genera
and an indeterminable Kufengoceratinae: Agathiceras sp., Stacheoceras sp., Kufengoceratinae
gen. and sp. indet., Waagenoceras sp., Jilingites cf. bidentus Liang, Roadoceras cf. roadense(Böse), Neopopanoceras cf. scrobiculatum (Gemmellaro), Propinacoceras sp., Propinacoceras?
sp. and Paraceltites cf. elegans Girty. Reexaminations of some existing ammonoid species are also
given. Including the known ones, the ammonoid fauna of the formation clearly indicates that the
Takakurayama Formation is Wordian in age.

Introduction
The Permian mudstone-dominated strata, theTakakurayama Formation, is narrowly distributed in the
Yaguki area, Iwaki City, in the southeastern margin of the
Abukuma Massif, Northeast Japan. It belongs to the South
Kitakami Belt and situated at the southwestern margin of
the belt. Rather rich cephalopod fossils have been known
from its upper part (Hayasaka, 1965; Yanagisawa, 1967;
Tazawa et al., 2005; Ehiro, 2008; Fujikawa and Suzuki,2011). Based on the ammonoid fauna, Hayasaka (1965)
correlated the Takakurayama Formation with the Middle
Permian Sosio Stage. Yanagisawa (1967) considered that
the Takakurayama Formation ranges in age from Early to
Middle Permian. Tazawa et al. (2005) dated the ammonoid
fauna as Middle Permian Wordian in age, but regarded themas reworked fossils, without showing any sedimentologicalevidences. Ehiro (2008) described some ammonoids
from the formation. He also reviewed the taxonomy of thepreviously reported ammonoids and the mode of occurrenceof fossils from the formation, and concluded that the
Takakurayama Formation is correlated with the Wordian. On
the other hand, Fujikawa and Suzuki (2011) reported some
Early Permian ammonoids, including Artinskia, in addition to
the Wordian ones.
R e c e n t l y, m a n y c e p h a l o p o d s a m p l e s f r o m t h e

Takakurayama Formation, collected mainly in the 1960’s
to the early 1970’s by Chisato Suzuki, were donated to the
Tohoku University Museum. They are important for dating
the Takakurayama Formation. This paper describes themand discuss on the age of the formation.

Stratigraphy of the Takakurayama Formationand fossil horizons
The Takakurayama Formation is distributed in anarrow area, elongated from north to south, east of Mt.
Takakurayama in the Yaguki area, the southeastern marginof the Abukuma Massif (Fig. 1). It was originally named
as the Takakurayama Series (Iwao and Matsui, 1961) or
Takakurayama Group (Yanagisawa and Nemoto, 1961), andsubdivided into the Iriishikura, Motomura and Kashiwadaira
formations, in ascending order (Yanagisawa, 1967). Later,
Onuki (1966) treated the group as a formation rank and theformations as members (Fig. 2). The Iriishikura Member
is more than 100 m thick and consists mostly of laminatedmudstone. The Motomura Member is 60 to 7 m in thickness,thinning to the south, and is mainly composed of sandstone
and alternating beds of sandstone and mudstone. In thenorthern area, it includes conglomeratic sandstone withlimestone pebbles-boulders and lenses. The Kashiwadaira
Member is rather thick (more than 250 m) and consists of

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Masayuki Ehiro

Figure 1. Geotectonic division
map of Northeast Japan showing
the study area (Yaguki Area) in
the South Kitakami Belt (A) andgeologic map of the Yaguki Area
(B). Longitude and latitude arefrom the International Terrestrial
Reference Frame.

laminated mudstone intercalated with thin sandstones andlenticular pebbly mudstones. Thickness of these sandstones
and pebbly mudstones are occasionally reaches 2 m, very
rarely 4 m, but usually less than 1 m. These strata trend
north-northeast and dip moderately to steeply west. Basedon the sedimentary structures such as cross beddings
and graded beddings in sandstone beds and laminas, nooverturned part exists.
Yanagisawa (1967) named small valleys in this area as
A-valley, B-valley, G2-valley, etc. for convenience (Figure 1).
He recognized eight fossil localities in the Takakurayama
Group (Formation) and named them as T1 to T8, and situatedT 1 Locality (B-valley) in the upper part of the Iriishikura
Formation, T3 (L2-valley), T4 (D3-valley) and T5 (F-valley) in
the Motomura Formation, and T2?, T6 (G1-valley), T7 (G2-valley) and T8 (H-valley) in the Kashiwadaira Formation.
Tazawa et al. (2005), Tazawa (2008) and Fujikawa andSuzuki (2011) used these Yanagisawa’s locality numbers (T1,
T7 and T8), and also positioned T1 in the Iriishikura Member
and T7 and T8 in the Kashiwadaira Member, but they did notshow any geologic map.
There is a large difference about the geologic map aroundA-, B- and L1-valleys between Yanagisawa (1967), and Ueno
(1992) and Ehiro (2008). In the geologic map of Yanagisawa(1967), the southern extension of the Motomura Member(Motomura Formation) is in the upper reaches of the L1and A-valleys, whereas Ueno (1992) and Ehiro (2008)
extended it to the middle reaches of the L1- and A-valleys.
According to my field survey, there is no thick sandstonedominated beds, correspond to the southern extension ofMiddle Permian cephalopods of the Takakurayama Formation, South Kitakami Belt, Northeast Japan23

are in the middle part of the member. The exact stratigraphic
relationship between the last two is not clear, because twoareas including these two localities are separated by themetamorphic rocks and not continuous (Yanagisawa, 1967).
The present ammonoid specimens were collected from theT1 and T7 localities (Fig. 2).

Systematic description
Specimens described in this paper are housed in the
Tohoku University Museum (Institution abbreviation: IGPS
= Institute of Geology and Paleontology, Tohoku University,
Sendai). Morphological terminology basically follows Arkell
et al. (1957) and the classification of taxonomic ranks
higher than genus follows Teichert et al. (1964) for the order
Nautilida, Furnish et al. (2009) for the orders Goniatitida andProlecanitida, and Arkell et al. (1957) for the order Ceratitida.
The following abbreviations are used in the descriptions: D= diameter of whorl, H = height of whorl, W = width of whorl,
UD = diameter of umbilicus.
Subclass Nautiloidea Agasizz, 1847
Order Nautilida Agasizz, 1847
Superfamily Tainoceratoidea Hyatt, 1883
Family Tainoceratidae Hyatt, 1883
Genus Tainoceras Hyatt, 1883
Type species.—Nautilus quadrangulus McChesney, 1860
Tainoceras cf. abukumaense Hayasaka
Fig. 3.1

Figure 2. Generalized columnar section of the Takakurayama
Formation, showing the fossil horizons.

the Motomura Member, in the upper reaches of the L1- andA-valleys. Instead, thick sandstone-dominated beds (ca. 10
m in L1-valley and ca. 7 m in A-valley) expose in their middle
reaches, situated in the extended direction of the member
distributed in L2-valley, as shown in geological maps of Ueno
(1992) and Ehiro (2008). Although Yanagisawa (1967),
Tazawa et al. (2005), Tazawa (2008) and Fujikawa andSuzuki (2011) positioned the fossil locality T1 in the upper
part of the Iriishikura Member, according to Ueno (1992) andEhiro (2008), it is reasonable to consider that its stratigraphic
position is in the lower part of the Kashiwadaira Member.
The cephalopod specimens of the Takakurayama
Formation have been reported from three localities: T1, T7
and T8. As shown above, the first horizon is situated in thelower part of the Kashiwadaira Member, and the latter two

cf. Tainoceras abukumaense Hayasaka, 1957, p. 24, pl. 8,
figs. 1–3; Hayasaka, 1965, p. 13.
Tainoceras abukumense Hayasaka. Hayasaka, 1962, p.
137, pl. 11, figs. 1–3, text-fig. 1; Hayasaka, 1967, p. 1,
text-figs. A, B; Koizumi, 1975, p. 32, pl. 5, figs. 1–2.
Material examined.—One specimen, IGPS coll. cat. no.
112470.
Description.—An outer mold of left side is examined. The
sub-evolute shell attains more than 75 mm in diameter andthe ratio of UD/D is about 0.3. The flank is inclined to theumbilicus. The umbilical wall is moderately inclined. The
ventral shoulder is nearly perpendicular, although the venter
is not fully preserved. The shell surface is ornamented withsinuous growth lines. There are two rows of nodes on theflank, one along the ventral shoulder and the other along theumbilical shoulder. Both numbered 18–19 (partly estimated)
per volution. The former nodes are large and high, thecross section of which is circular to laterally elongated, andsometimes associated with short ribs diminishing their height
toward the umbilicus. The latter nodes are considerably

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Masayuki Ehiro

Figure 3. Nautiloids (Tainoceras, Endolobus? and Domatoceras) from the Takakurayama Formation.
1, Tainoceras cf. abukumaense Hayasaka, IGPS coll. cat. no. 112470, lateral view; 2, Tainoceras sp., IGPS coll. cat. no.
112471, lateral (2a) and ventral (2b) views; 3, Endolobus? sp., IGPS coll. cat. no. 112480, lateral view (3a) and suture line (3b);4 and 5, Domatoceras sp.; 4, IGPS coll. cat. no. 112481, lateral view (4a) and suture line (4b); 5, IGPS coll. cat. no. 12482,
lateral view. Scale bars are 1 cm, unless otherwise stated.
smaller than the former ones. The suture is not preserved.
Comparison.—The shape of the flank and its
ornamentation, especially the shape of two rows of nodes ofthe present specimen is similar to the holotype of Tainoceras
abukumaense Hayasaka collected from the Takakurayama
Formation, but I refrain from identifying it at the specificlevel because its shell cross section and suture lines are
unknown.
Occurrence.—From the middle part of the Kashiwadaira
Member at G 2 -valley (T 7 Locality), Yaguki, Iwaki City,
Fukushima Prefecture. Middle Permian (Wordian).
Tainoceras sp.
Figs. 3.2a–b
Material examined.—One specimen, IGPS coll. cat. no.
112471.
Descriptive remarks.—A fragmental inner mold, obliquely

deformed, are examined. The evolute shell attains morethan 24 mm in shell diameter. At the preserved end, theheight is ca. 14 mm and the width is ca. 16 mm. The flanks
are flat and the venter is broadly rounded. There are sharpradial ribs, run from the umbilical shoulder and end at theventral shoulder forming small nodes. Two fine ridges run on
the venter forming the shallow central groove. The suture is
not preserved.
Based on the general shell morphology, it is highly
probable that the present specimen belongs to the genus
Tainoceras Hyatt, 1883, but the specific identification isdifficult due to the poor state of preservation.
Occurrence.—From the middle part of the Kashiwadaira
Member at G 2 -valley (T 7 Locality), Yaguki, Iwaki City,
Fukushima Prefecture. Middle Permian (Wordian).
Genus Pleuronautilus Mojsisovics, 1882
Type species.—Pleuronautilus trinodosus Mojsisovics, 1902

Middle Permian cephalopods of the Takakurayama Formation, South Kitakami Belt, Northeast Japan
Pleuronautilus chisatoi sp. nov.
Figs. 4.1a–f
Etymology.—The species name is to honor Mr. Chisato
Suzuki, who collected the holotype and making it available
for study.
Material examined.—One specimen, IGPS coll. cat. no.
112472 (holotype).
Diagnosis.—A species of Pleuronautilus with thickly
discoidal and sub-evolute shell. The shell surface isornamented with prorsiradiate ribs on the flanks andlongitudinal lirae on both the flanks and venter.
Description.—The shell attains about 48 mm in maximum
diameter along the longest axis of the elliptically deformed
specimen, and the corresponding height and umbilical
diameter are 20.9 (H/D = 0.44) and 18.6 mm (UD/D = 0.39),
respectively. The shell width is apparently ca. 9.0 mm, but
this value is under tectonically flattened state and its exact
value is unknown. The flanks are slightly convex, with the
maximum shell width near the umbilical shoulder to umbilicalone-thirds of the flanks, and gently converge to the venter.
The umbilical wall is steep with acutely rounded umbilicalshoulder. The venter, with rounded ventrolateral shoulders,is nearly flat but its median part is slightly concave.
There are prominent lateral ribs on the flanks, numbered
24–25 per volution. The ribs are prorsiradiate and run fromthe umbilical shoulder, slightly strengthened ventrally, andend at the ventrolateral shoulder forming small nodes. Near
the umbilical shoulder, the ribs incline forward. In addition,
both the lateral and ventral shell surfaces are ornamented
with fine longitudinal lirae.
The external suture consists of very shallow? ventral lobe,
low ventrolateral saddle, and wide and shallow lateral lobe.
The dorsal suture seems to be nearly straight.
Comparison.—Pleuronautilus chisatoi sp. nov. is clearly
distinguished from all other species of Pleuronautilus inhaving longitudinal lirae on the shell surface.
Occurrence.—Lower part of the Kashiwadaira Memberof the Takakurayama Formation at B-valley (T1 Locality),eastern slope of Mt. Takakurayama, Yaguki, Iwaki City,
Fukushima Prefecture. Middle Permian (Wordian).
Pleuronautilus cf. gregarius (Miller)
Figs. 4.2–4.3
cf. Metacoceras gregarium Miller, 1945, p. 283, pl. 45, figs.
5–8.
Foordiceras gregarium (Miller). Miller and Youngquist,
1949, p. 98, pl. 36, fig. 5, pl. 38, figs. 5–8, pl. 39, figs. 1,
2, 6–9, pl. 40, figs. 1–4, pl. 41, figs. 5–9.
Pleuronautilus (P.) gregarium (Miller). Kummel, 1953, p.
36.

25

Pleuronautilus gregarius (Miller). Shimanskiy, 1967, p.
93.
Material examined.—Two specimens, IGPS coll. cat. no.
112473 and 112474.
Description.—The specimens are obliquely deformed.
One specimen (no. 112473), consisting of phragmocone anda part of the body chamber, attains 55.7 mm in maximum
diameter along the elliptically deformed specimen, andthe corresponding height and umbilical diameter are 26.1
(H/D = 0.47) and 16.9 mm (UD/D = 0.30), respectively. The
shell width is apparently ca. 15 mm, but this value is under
tectonically flattened state and its exact value is unknown.
Another one (no. 112474) is a phragmocone. It attains 64.0
mm in maximum diameter along the longest axis of theelliptically deformed specimen, and the corresponding height
and umbilical diameter are 26.0 (H/D = 0.41) and 22.2 mm(UD/D = 0.35), respectively.
The flanks of the specimens are nearly flat. The venter,with rounded ventrolateral shoulders, is nearly flat, but there
is a shallow groove? on the median part of no. 112473.
There are slightly prorsiradiate lateral ribs on the flanks,
running from the umbilical shoulder to the ventrolateralshoulder. They curve slightly backward and become wide
ventrally. The specimen no. 112473 have 19-20 ribs pervolution, adoral ones of which are slightly depressed at the
middle part. The ribs of another specimen (no. 112474)
numbers 11-12 per half volution, but they are indistinct near
the adoral end.
The external suture consists of shallow ventral lobe, lowventrolateral saddle, and wide and shallow lateral lobe. The
dorsal lobe is very shallow to nearly straight.
Comparison.—The present specimens from the
Takakurayama Formation are similar to Pleuronautilus
gregarius (Miller) from the Wordian strata of USA, but the
precise identification is difficult because of their poor stateof preservation. Foordiceras gregarium (Miller) described by
Yanagisawa (1967) from the Takakurayama Formation (Loc.
T7: G2-valley) is very poorly preserved and fragmental, andhence difficult to identify not only at the species level but
also at the genus level.
Occurrence.—Lower part of the Kashiwadaira Memberof the Takakurayama Formation at B-valley (T1 Locality),eastern slope of Mt. Takakurayama (no. 112473) and middle
part of the Kashiwadaira Member at G2-valley (T7 Locality)(no. 112474), Yaguki, Iwaki City, Fukushima Prefecture.
Middle Permian (Wordian).
Pleuronautilus sp.
Fig. 4.4
Material examined.—One specimen, IGPS coll. cat.

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Masayuki Ehiro

Figure 4. Nautiloids (Pleuronautilus and Pleuronautilus?) from the Takakurayama Formation.
1, Pleuronautilus chisatoi sp. nov., IGPS coll. cat. no. 112472 (holotype); 1a and 1b, lateral (1a) and ventral (1b) views; 1c
and 1d, partial enlargements of lateral (1c) and ventral (1d) views showing longitudinal lirae; 1e and 1f, suture lines at H =10 mm (1e) and 17 mm (1f); 2 and 3, Pleuronautilus cf. gregarius (Miller); 2, IGPS coll. cat. no. 112473, lateral view (2a),ventral view (2b) and suture line (2c); 3, IGPS coll. cat. no. 112474; 3a, lateral view; 3b and 3c, suture lines at H = 15 mm(3b) and 22 mm (3c); 4, Pleuronautilus sp., IGPS coll. cat. no.112475, lateral view (4a), ventral view (4b) and suture line (4c);
5–8, Pleuronautilus? sp., all lateral views; 5, IGPS coll. cat. no. 112476; 6, IGPS coll. cat. no. 112477; 7, IGPS coll. cat. no.
112478; 8, IGPS coll. cat. no. 112479. Scale bars are 1 cm, unless otherwise stated.

no.112475.
Descriptive remarks.—A fragmental inner mold,tectonically compressed dorso-ventrally, is at hand. The shellis evolute and attains more than 55 mm in diameter. At thepreserved adoral end, the height and width are ca. 14 and
32 mm, respectively. The flat to slightly concave flanks, withacutely rounded umbilical and ventral shoulders, converge
toward the venter. The umbilical wall is nearly perpendicular.
The wide venter is flat to slightly concave. There are radialribs, curved backward, on the flanks. The venter is smooth.
The suture consists of a wide and shallow ventral lobe, small
and low ventrolateral saddle and a moderately deep laterallove. The dorsal suture is not well preserved.
Based on the shell outline, surface ornamentation andthe shape of the external suture, the present specimen isconsidered to belong to the genus Pleuronautilus, but the
specific identification is difficult because of its poor state ofpreservation.

Middle Permian cephalopods of the Takakurayama Formation, South Kitakami Belt, Northeast Japan
Occurrence.—Middle part of the Kashiwadaira Member
at G 2-valley (T 7 Locality), Yaguki, Iwaki City, Fukushima
Prefecture. Middle Permian (Wordian).
Pleuronautilus? sp.
Figs. 4.5–4.8
Material examined.—Four specimens, IGPS coll. cat. no.
112476–112479.
Descriptive remarks.—Four fragmental outer molds,
obliquely deformed, are examined. They are evolute andthe flanks are nearly flat. The largest specimen (no. 112478)
attains more than 55 mm in diameter. The maximum
shell diameter of the second one is about 55 mm and its
corresponding umbilical diameter is ca. 23 mm (UD/D =0.42). The third one is 43 mm in maximum diameter with theratio of UD/D = ca. 0.35. The smallest specimen attains adiameter of 29 mm. There are prominent prorsiradiate lateralribs on the flanks. The ribs run from the umbilical shoulder,slightly strengthened ventrally, and end at the ventrolateralshoulder forming longitudinal nodes. Near the umbilicalshoulder, the ribs incline forward.
The shell outline and surface ornamentation of thepresent specimens resemble those of the species of thegenus Pleuronautilus, such as P. gregarius (Miller). But
there remains some doubt on the generic position of them,because they are fragmental and their shell cross sections
are unknown.
Occurrence.—All specimens are from the middle part of
the Kashiwadaira Member at G2-valley (T7 Locality), Yaguki,
Iwaki City, Fukushima Prefecture. Middle Permian (Wordian).
Family Koninckioceratidae Hyatt in Zittel, 1900
Genus Endolobus Meek and Worthen, 1865
Type species.—Nautilus spectabilis Meek and Worthen,
1860
Endolobus? sp.
Figs. 3.3a–3bMaterial examined.—One specimen, IGPS coll. cat. no.
112480.
Descriptive remarks.—The small specimen is tectonically
deformed obliquely, and precise original shell shape is notknown. It consists of inner mold and probable natural castof the outer mold, and shows semi-evolute and probably
thickly discoidal shell outline. The maximum shell diameterattains about 18 mm along the elliptically deformed longest
axis, and the corresponding height and umbilical diameterare both about 7 mm (H/D and UD/D = 0.39), respectively.
The shell width exceeds 5 mm. The flanks converge to theumbilicus. The venter is estimated to be broadly rounded27

with angular ventrolateral shoulders. The adapical partof shell surface is ornamented with fine radial striae or
growth lines. There are also rows of small nodes along theventrolateral shoulders. The external suture consists ofvery shallow (nearly straight) ventral and lateral lobes withindistinct ventrolateral saddle.
Based on the estimated shell outline, presence ofventrolateral nodes and the shape of the external sutureline, the present specimen is considered to belong to thegenus Endolobus, but some doubt remains on the generic
identification because of its severe tectonic deformation.
Occurrence.—Middle part of the Kashiwadaira Member
at G 2-valley (T 7 Locality), Yaguki, Iwaki City, Fukushima
Prefecture. Middle Permian (Wordian).
Superfamily Trigonoceratoidea Hyatt, 1884
Family Grypoceratidae Hyatt in Zittel, 1900
Genus Domatoceras Hyatt, 1891
Type species.—Domatoceras umbilicatum Miller, Dunberand Condra, 1933
Domatoceras sp.
Figs. 3.4–3.5
Material examined.—Two specimens, IGPS coll. cat. no.
112481 and112482.
Description.—Two fragmental specimens, both preserved
only one side, are examined. They are laterally compressed,
sub-evolute and flattened, and shell cross section is subrectangular. One specimen (no. 112481) attains about 64
mm in diameter, and its corresponding height and umbilical
diameter are ca. 25 (H/D = 0.39) and ca. 19 mm (UD/D= 0.30), respectively. The width exceeds 10 mm, but the
precise value is not known because of its ill preservation.
The flanks are nearly flat to very broadly convex, andparallel to very slightly converge to the venter. The umbilicalshoulder is rounded and the umbilical wall is steeply dipping.
The ventrolateral shoulder is acutely rounded. The shellsurface is almost smooth, but the specimen 112481 hassome laterally elongated nodes with short radial ribs on theventral shoulder of the phragmocone to the beginning of the
body chamber. Only the lateral suture, which consists of alarge love, is preserved in the specimen 112481.
C o m p a r i s o n . — T h e p r e s e n t s p e c i m e n 11 2 4 8 1 i scharacterized by having small elongated nodes of the ventral
shoulder. Domatoceras sp. from the Wordian of Mexico(Miller and Youngquist, 1949, p. 47, pl. 45, fig. 8) somewhat
resembles in shell outline and having ventrolateral nodes.
Domatoceras sculptile (Girty) (Metacoceras sculptile
Girty, 1911, p. 148; Girty, 1915, p. 245, pl. 31, figs. 1-2a;
Pseudometacoceras sculptile, Miller et al., 1933, p. 226, pl.
6, figs. 9-12; Domatoceras sculptile, Miller and Youngquist,

28

Masayuki Ehiro

1949, p. 41, text-fig. 5) from the Upper Carboniferous of
Oklahoma, Domatoceras williami Miller and Owen (Miller
and Owen, 1934, p. 246, pl. 16, fig. 4, pl. 17, figs. 1-4, pl. 18,
fig. 1, text-fig. 6) from the Upper Carboniferous of the MidContinent region, Domatoceras hayi (Hyatt) (Metacoceras
Hayi Hyatt, 1891, p. 339, text-figs. 38-39; Hay, 1893, p. 38,
text-figs. 8-9; Miller et al., 1933, p. 173, text-fig. 25) from theLower Permian (Carboniferous?) of the Mid-Continent region
also have ventrolateral nodes. It is, however, difficult to
identify the present specimens at the specific level, because
they are fragmental and poorly preserved.
Occurrence.—Both specimens are from the middle part of
the Kashiwadaira Member at G2-valley (T7 Locality), Yaguki,
Iwaki City, Fukushima Prefecture. Middle Permian (Wordian).
Subclass Ammonoidea Zittel, 1884
Order Goniatitida Hyatt, 1884
Suborder Goniatitina Hyatt, 1884
Superfamily Agathiceratoidea Arthaber, 1911
Family Agathiceratidae Arthaber, 1911
Genus Agathiceras Gemmellaro, 1887
Type species.—Agathiceras suessi Gemmellaro, 1887
Agathiceras sp.
Figs. 5.1–5.5
Material.—IGPS coll. cat. no. 112483–112496.
Descriptive remarks.—Fourteen specimens, ellipticallyand obliquely deformed, are examined. Specimens are
small, the diameter of which ranges from 17 to 23 mmalong the elliptically deformed longest axis. The umbilicus
is very small and almost closed. The sides are convex
with broadly rounded umbilical and ventral shoulders. The
venter is rounded. The shell surface is ornamented by manyfine spiral lirae. The suture is poorly preserved in somespecimens, and five saddles and four lobes are present on
the lateral side. The crests of the saddles are rounded. The
bases of the lobes are also rounded, but slightly pointed at
the center.
Based on the general shell shape, surface ornamentationand the outline of the suture line, the present specimens
are considered to belong to the genus Agathiceras, but thestrong tectonic deformation makes it difficult to identify themat the species level.
Occurrence.—Specimens no. 112483–112485 arefrom the lower part of the Kashiwadaira Member of the
Takakurayama Formation at B-valley (T1 Locality), eastern
slope of Mt. Takakurayama, and no. 112486–112496
are from the middle part of the Kashiwadaira Member
at G 2-valley (T 7 Locality), Yaguki, Iwaki City, Fukushima
Prefecture. Middle Permian (Wordian).

Superfamily Cycloloboidea Zittel, 1895
Family Vidrioceratidae Plummer and Scott, 1937
Genus Stacheoceras Gemmellaro, 1887
Type species.—Stacheoceras mediterraneum Gemmellaro,
1887
Stacheoceras sp.
Figs. 5.6–5.7
Material.—IGPS coll. cat. no. 112497 and 112498.
Descriptive remarks.—Two fragmental specimens are
examined. One specimen (no. 112497) consists of anouter mold with a small fragmental inner mold. The shell
diameter attains more than 30 mm. It is involute with closed
umbilicus. The conch has convex sides and acutely rounded
to carinate venter with a lenticular cross section, although
the lenticular shape may be due to the tectonic flattening.
The shell surface seems to be smooth. The external sutureis partly preserved. The ventral lobe is wide and deep, but
its basal part is not preserved. On the side, at least four setof lateral saddles and lobes are recognized, all diminishingin size toward the umbilicus. The crests of all saddles arerounded. The first lateral lobe is bifid at the base. The
second to fourth are bi- or trifid at the base. Another one (no.
112498) is a tectonically flattened, fragmental phragmocone.
The apparent cross section is lenticular. The shell surface
seems to be smooth. A part of the lateral suture, consistingat least four saddles and lobes are preserved on the side.
They gradually diminish in size toward the venter. All saddles
have rounded crest. The lateral lobes are trifid, the central
branches of them are deepest.
Based on the general shell shape and suture line, thepresent specimens are considered to belong to the genus
Stacheoceras, but the specific identification is difficult
because of its poor state of preservation.
Occurrence.—The middle part of the Kashiwadaira
Member at G 2 -valley (T 7 Locality), Yaguki, Iwaki City,
Fukushima Prefecture. Middle Permian (Wordian).
Family Cyclolobidae Zittel,1895
Subfamily Kufengoceratinae Zhao,1980
Kufengoceratinae gen. and sp. indet.
Figs. 5.8a–b
Material.—IGPS coll. cat. no. 112499.
Descriptive remarks.—A small, elliptically deformed andflattened specimen is examined. It is involute to sub-involuteand apparently discoidal. The diameter of the shell attains
30.2 mm along the longest axis of the elliptically deformed
specimen, and the corresponding height and umbilical
diameter are ca. 14.0 (H/D = 0.46) and 4.4 mm (UD/D

Middle Permian cephalopods of the Takakurayama Formation, South Kitakami Belt, Northeast Japan

29

Figure 5. Ammonoids (Agathiceras, Stacheoceras and Kufengoceratinae gen. and sp. indet.) from the Takakurayama
Formation.
1–5, Agathiceras sp.; 1, IGPS coll. cat. no. 112483, ventro-lateral view; 2, IGPS coll. cat. no. 112484, lateral view; 3, IGPS
coll. cat. no. 112486, lateral view (3a) and suture line (3b); 4, IGPS coll. cat. no. 112487, lateral view; 5, IGPS coll. cat. no.
112488, lateral view; 6 and 7, Stacheoceras sp.; 6, IGPS coll. cat. no. 112497, lateral view of the outer mold and a part of theinner mold (6a) and suture line (6b); 7, IGPS coll. cat. no. 112498, lateral views of fragmental inner mold of the ventro-lateralpart (7a) and suture line (7b); 8, Kufengoceratinae gen. and sp. indet., IGPS coll. cat. no. 112499, lateral view (8a), ventral
view (8b) and suture line (8c). Scale bars are 1 cm, unless otherwise stated.

= 0.15), respectively. The sides of the shell are broadly
rounded. The umbilical wall is steep with sharply roundedumbilical shoulder. The venter is acutely rounded withbroadly rounded ventral shoulders. There are faint, rather
widely spaced, slightly prorsiradiate ribs or striations on theshell surface. There are some variations in the thickness,height and interspaces of the ribs. The fragmental lateral
suture consists of four saddles and three to four lobes.
The crests of saddles are all rounded. The lobes are rather
strongly serrated up to the upper part of the sides. The baseof the first lateral lobe has deep serrations, but bases of theother lobes are not well preserved.
Based on the general shape of the suture line, thepresent specimen is considered to belong to the subfamily
Kufengoceratinae, probably a species of the genus
Guiyangoceras Zhou, 1985, Liuzhouceras Zhao, 1980
or Paratongluceras Zhao and Zheng, 1977. The present
specimen has a discoidal conch shape and differs fromthose of these kufengoceratids, which have pachyconic
to globular conch. This is, however, due to the tectonic
deformation. It is difficult to identify it at the generic level

because of its poor state of preservation, especially ill
preserved suture line.
Occurrence.—From the middle part of the Kashiwadaira
Member at G 2 -valley (T 7 Locality), Yaguki, Iwaki City,
Fukushima Prefecture. Middle Permian (Wordian).
Subfamily Cyclolobinae Zittel,1895
Genus Waagenoceras Gemmellaro, 1887
Type species.—Waagenoceras mojsisovicsi Gemmellaro,
1887
Waagenoceras sp.
Figs. 6.1–6.4
Material.—IGPS coll. cat. no. 112500–112503.
Descriptive remarks.—Four specimens, elliptically
deformed, are examined. They are fragmental, except for thelargest specimen (no. 112500). The last specimen attains
a shell diameter about 120 mm in the obliquely deformed
state, and its corresponding height, width and umbilical
diameter are ca. 80, ca. 40 and ca. 15? mm, respectively.

30

Masayuki Ehiro

The shell flanks are broadly rounded with rounded umbilicaland ventral shoulders. The venter is also rounded. The shellsurface looks like smooth. The suture is partly preserved inall specimens. It is typical Waagenoceras-type as shown in
Figure 6.1b, 6.2b, 6.3b and 6.4b.
Based on the general shell shape and the suture line,
the present specimens undoubtedly belong to the genus
Waagenoceras, but the species level identification is difficult
because of its poor and severely deformed preservation.
Occurrence.—All specimens are from the middle part of
the Kashiwadaira Member at G2-valley (T7 Locality), Yaguki,
Iwaki City, Fukushima Prefecture. Middle Permian (Wordian).

The present species is similar to the type species Jilingites
bidentus in the shell shape and smooth shell surface, but the
specimens are rather poorly preserved and deformed, andsome doubt remains in the specific identification.
Occurrence.—Specimens no. 112504 and 112505 arefrom the lower part of the Kashiwadaira Member of the
Takakurayama Formation at B-valley (T1 Locality), eastern
slope of Mt. Takakurayama, and specimens no. 112506–
112510 are from the middle part of the Kashiwadaira
Member at G 2 -valley (T 7 Locality), Yaguki, Iwaki City,
Fukushima Prefecture. Middle Permian (Wordian).

Superfamily Marathonitoidea Ruzhentsev, 1938
Family Marathonitidae Ruzhentsev, 1938
Genus Jilingites Liang, 1982
Type species.—Jilingites bidentus Liang, 1982,

Superfamily Neoicoceratoidea Hyatt in Zittel, 1900
Family Paragastrioceratidae Ruzhentsev, 1951
Subfamily Pseudogastrioceratinae Furnish, 1966
Genus Roadoceras Zhou, 1985
Type species.—Gastrioceras roadense Böse, 1919

Jilingites cf. bidentus Liang
Figs. 6.5–6.8

Roadoceras cf. roadense (Böse)
Fig. 6.9

cf. Jilingites bidentus Liang, 1982, p. 651, pl. 1, figs. 10–13,
text-fig. 6.

cf. Gastrioceras roadense Böse, 1919, p. 85, pl. 2 figs. 28–
47.
Paragastrioceras roadense (Böse). Plummer and Scott,1937, p. 227, pl. 22, figs.15–17; Hayasaka, 1947, p.
27, pl. 1, fig. 4, pl. 2, fig. 3, text-fig. 4.
Pseudogastrioceras globulosissmum Plummer and Scott,1937 (parts), p. 279, pl. 18 fig. 10.
Pseudogastrioceras roadense (Böse). Miller and Furnish,
1940, p. 89, pl. 16, figs.1–7, pl. 17, fig. 5, pl. 18 fig. 10,
11, pl. 28 figs. 1–3; Miller in King et al., 1944, p. 89, fig.
8, pl. 24, figs. 2, 3, pl. 25, figs. 1–6; Miller, 1945, p. 16,
pl. 6, figs. 3–5, pl. 7, figs. 1–3; Clifton, 1946, p. 558,
pl. 85, figs. 1, 2; González-Arreola et al., 1994, p. 215,
pl.1, figs. i–k.
Altudoceras roadense (Böse). Ruzhentsev, 1960, fig.
34a; Liang, 1982, p. 649, pl. 2, figs. 3–4, pl. 3, figs.
3–6, text-figs. 4a, 4b.
Roadoceras roadense (Böse). Zhou, 1985, p. 196; Zhou,
1987, p. 327; Glenister et al. in Furnish et al., 2009, p.
172, text-figs. 106.6a–6c.
Pseudogastrioceras zittelli Gemmellaro. Tokai Fossil
Society, 1995, p. 50.

Material.—IGPS coll. cat. no. 112504–112510.
Description.—Seven elliptically deformed specimens are
examined. The shell is small and its maximum diameter
ranges from 20 to 45 mm, but the largest specimen attains
at least 60 mm. Six specimens are consists of phragmocone.
The living chamber, occupying more than three quartersof the last whorl, is only preserved in one specimen (no,112507). The conch has convex sides with a rounded
venter and a very small to closed, shallow? umbilicus.
The ventral and umbilical shoulders are broadly rounded.
Although the original shell shape is not precisely known due
to the tectonic deformation, its cross-section is presumably
thickly discoidal and the maximum shell width is near theumbilical two-thirds. The ornamentation of the shell surface
is not known, but the surfaces of inner molds are smooth.
The suture lines are partly preserved. The broad ventral
lobe is divided into two bifid prongs by rather high mediansaddle, which is about four-fifth of the ventrolateral saddle.
On the lateral sides, there are four to five bifid lateral lobes
and rounded saddles, but the suture near the umbilicus is
not preserved. The lateral lobes are all similar shape anddiminish in size towards the umbilicus.
Comparison.―Two species of Jilingites have beenreported: Jilingites bidentus Liang, 1982 from the Wordian of
Jiling, North China and J. kesennumensis Ehiro and Araki,
1997 from the Capitanian of South Kitakami Belt, Northeast
Japan. One questionable specimen of Jilingites was also
reported from the Takakurayama Formation (Ehiro, 2008).

Material.—IGPS coll. cat. no. 112511.
Description.—The shell is discoidal with rounded venter.
The sides are broadly convex, with acutely roundedumbilical shoulder and broadly rounded ventral shoulder.
The maximum shell width is about the center of the flank.
The umbilicus is small with steep umbilical wall. The shellattains about 30 mm in diameter with a ratio of UD/D = ca.
0.24. The shell surface is ornamented with fine spiral ribs. In

Middle Permian cephalopods of the Takakurayama Formation, South Kitakami Belt, Northeast Japan

31

Figure 6. Ammonoids (Waagenoceras, Jilingites and Roadoceras) from the Takakurayama Formation.
1–4, Waagenoceras sp.; 1, IGPS coll. cat. no. 112500, lateral view (1a), ventral view (1b) and part of the suture line (1c);2, IGPS coll. cat. no. 112503, lateral view of the fragmental inner mold (2a) and suture line (2b); 3, IGPS coll. cat. no.
112501, cross section (3a) and ventral lobe (3b); 4, IGPS coll. cat. no. 112502, lateral view (4a) and suture line (4b); 5–8,
Jilingites cf. bidentus Liang; 5, IGPS coll. cat. no. 112505, ventral view (5a) and ventro-lateral suture line (5b); 6, IGPS coll.
cat. no. 112507, lateral view (6a) and suture line (6b); 7, IGPS coll. cat. no. 112508, lateral view (7a), ventral view (7b) andsuture line (7c); 8, IGPS coll. cat. no. 112504, lateral view of the outer mold and a part of the inner mold; 9, Roadoceras cf.
roadense (Böse), IGPS coll. cat. no. 112511, lateral view. Scale bars are 1 cm, unless otherwise stated.

addition, there are 16-17, fine and short, radial ribs per half
volution, along the umbilical shoulder. They are prorsiradiate
and extend to the inner one-thirds of the flank, but become
indistinct forward. The suture line is not preserved.
Discussion.—This specimen is probably the same
specimen reported as Pseudogastrioceras zittelli

Gemmellaro, 1887 by Tokai Fossil Society (1995, p. 50).
Based on the general shell shape and ornamentation, thepresent specimen is considered to belong to the genus
Roadoceras Zhou, 1985, and comparable with the typespecies Roadoceras roadense (Böse, 1919). However,I refrain from identifying it at the specific level precisely

32

Masayuki Ehiro

because of its ill state of preservation and lacking the sutureline.
Occurrence.—Lower part of the Kashiwadaira Memberof the Takakurayama Formation at B-valley (T1 Locality),eastern slope of Mt. Takakurayama, Yaguki, Iwaki City,
Fukushima Prefecture. Middle Permian (Wordian).
Genus Neopopanoceras Schindewolf, 1939
Type species.—Popanoceras scrobiculatum Gemmellaro,
1887
Tauroceras Tumanskaia, 1938, non Hope, 1840 (modern
insect)Neopopanoceras Schindewolf, 1939, non Spath, 1951
(Triassic ammonoid); Glenister et al., 2009
See “Nomenclatorial note” by Zhou and Glenister inFurnish et al., 2009, p. 218.
Neopopanoceras cf. scrobiculatum (Gemmellaro)Figs. 7.1–7.4
cf. Popanoceras scrobiculatum Gemmellaro, 1887, p. 25, pl.
3, figs. 22–26, pl. 8, fig. 26; Gemmellaro, 1888, p. 14,
pl. B, figs. 2–4, pl. C, figs. 9, 10; Frech, 1902, pl. 59a,
figs. 7a–7e; Ruzhentsev, 1951, text-fig. 56d; Miller etal., 1957, L. 52, text-fig. 2-8; Termier et al., 1972, p.
114, pl. 17, figs. 5–8
Tauroceras scrobiculatum (Gemmellaro). Tumanskaia,
1938, p. 145, text-figs. 1–4; Ruzhentsev, 1960, p. 111,
text-fig. 1g; Glenister and Furnish, 1988, p. 45, pl. 3,
fig. 8, pl. 4, fig.12–13, text-fig.1; Leonova, 2002, S 95,
text-fig. 59; Zhou and Yang, 2005, p. 387, text-figs. 5.1,
5.2, 11.
Neopopanoceras scrobiculatum (Gemmellaro). Glenister
et al. in Furnish et al., 2009, p. 181, text-figs. 115.1a–
1f.
Material.—IGPS coll. cat. no. 112512–112515.
Description.—Four small specimens, elliptically deformed,
are examined. They are mostly outer molds, but somefragmental inner molds are also preserved. The maximum
conch diameters range from ca. 12 to 35 mm.
The shell is narrowly discoidal and evolute, with amedium-sized umbilicus (the UD/D ratios are about onethirds). The flanks and venter are flattened with abruptly
rounded ventrolateral shoulders. Fine and dense radial ribs
are prominent on the umbilical wall to the venter, but are
rather inconspicuous on the flanks of the inner volution.
They are sinuous on the flanks and form a deep U-shaped
ventral sinus. At the midpoint of the flanks of the inner
volution, there are remarkable pits, which change in outline
from circular or longitudinally elongated to become radiallyelongated as they grow. The suture is not preserved.
Discussion.—From the shell shape and ornamentation,
the present specimens undoubtedly belong to the genus
Neopopanoceras Schindewolf, 1939, and most probably
identified as N. scrobiculatum (Gemmellaro). But the precise
identification at the specific level is difficult since they arepoorly preserved and lacking the suture line.
Occurrence.—Middle part of the Kashiwadaira Memberof the Takakurayama Formation at G2-valley (T7 Locality),eastern slope of Mt. Takakurayama, Yaguki, Iwaki City,
Fukushima Prefecture. Middle Permian (Wordian).
Order Prolecanitida Miller and Furnish, 1954
Superfamily Medlicottitoidea, Karpinsky, 1889
Family Medlicottidae Karpinsky, 1889
Subfamily Propinacoceratinae Plummer and Scott, 1937
Genus Propinacoceras Gemmellaro, 1887
Type species.—Propinacoceras Beyrichi Gemmellaro, 1887
Propinacoceras sp.
Figs. 7.5–7.8
Material.—IGPS coll. cat. no. 112516, 112519–112522.
Descriptive remarks.—Five fragmental specimens are athand. The conch is thinly discoidal and involute with almost
closed umbilicus. The sides are flat and almost parallel toeach other, but slightly converge toward the umbilicus. The
venter is also flat, but bears two rows of prominent nodes
or short ribs, which are separated by a median groove.
The umbilical and ventral shoulders are acutely rounded.
The suture is only poorly preserved in one specimen (no.
112516). The ventrolateral saddle seems to be low and widewith some serrations, but the precise shape is not known.
Lateral lobes are bifid or rounded at the base. All saddles
are rounded.
Based on the shell shape, shell ornamentation andgeneral shape of suture line, the present specimens seem tobelong to the genus Propinacoceras Gemmellaro, 1887. But
it is difficult to identify at the specific level, because of theirpoor state of preservation.
Occurrence.—Lower and middle part of the Kashiwadaira
Member of the Takakurayama Formation at B-valley (T 1
Locality: no. 112516) and G2-valley (T7 Locality: no. 112519–
112522), eastern slope of Mt. Takakurayama, Yaguki, Iwaki
City, Fukushima Prefecture. Middle Permian (Wordian).
Propinacoceras? sp.
Figs. 7.9–7.11
Material.—IGPS coll. cat. no. 112517, 112518, 112523–
112536.
Descriptive remarks.—Many fragmental specimens areMiddle Permian cephalopods of the Takakurayama Formation, South Kitakami Belt, Northeast Japan

33

Figure 7. Ammonoids (Neopopanoceras, Propinacoceras, Propinacoceras? and Paraceltites) from the Takakurayama
Formation.
1–4, Neopopanoceras cf. scrobiculatum (Gemmellaro), all lateral views; 1, IGPS coll. cat. no. 112513; 2, IGPS coll. cat. no.
112512; 3, IGPS coll. cat. no. 112515; 4, IGPS coll. cat. no. 112514; 5–8, Propinacoceras sp.; 5, IGPS coll. cat. no. 112516,
lateral view (5a), ventral view (5b) and suture line (5c); 6, IGPS coll. cat. no. 112519, lateral (6a) and ventral (6b) views; 7,
IGPS coll. cat. no. 112520, lateral (7a) and ventral (7b) views; 8, IGPS coll. cat. no. 112521, lateral (8b) and ventral (8b)views; 9–11, Propinacoceras? sp.; 9, IGPS coll. cat. no. 112523, lateral (9a) and ventral (9b) views; 10, IGPS coll. cat. no.
112524, lateral view; 11, IGPS coll. cat. no. 112525, lateral (11a) and ventral (11b) views; 12–14, Paraceltites cf. elegans
Girty, all lateral views; 12, IGPS coll. cat. no. 112537; 13, IGPS coll. cat. no. 112538; 14, IGPS coll. cat. no. 112539 (14a)and 112540 (4b). Scale bars are 1 cm, unless otherwise stated.
at hand. Most specimens are small fragment of the ventral
part. The fragmentation is considered to be almost occurred
during the sampling process. The conch is thinly discoidal
with flat and parallel sides. The venter is also flat, with tworows of prominent nodes or short ribs, which are separated
by a median groove. The ventral shoulders are acutely
rounded.
The present specimens are likely to belong to the genus
Propinacoceras Gemmellaro, 1887, because they yieldedwith Propinacoceras specimens and having the same shell
shape and shell ornamentation with the genus. There is,however, another possibility that these species belong
to any genera of subfamily Propinacoceratinae, such as
Bamyaniceras Termier and Termier, 1970 and Difuntites
Glenister and Furnish, 1988 by their shell shape andornamentation.
Occurrence.—Lower and middle part of the Kashiwadaira
Member of the Takakurayama Formation at B-valley (T 134

Masayuki Ehiro

Locality: no. no. 112517, 112518) and G2-valley (T7 Locality:
no. 112523–112536), eastern slope of Mt. Takakurayama,
Yaguki, Iwaki City, Fukushima Prefecture. Middle Permian(Wordian).
Order Ceratitida Hyatt, 1884
Superfamily Xenodiscoidea Frech, 1902
Family Paraceltitidae Spath, 1930
Genus Paraceltites Gemmellaro, 1887
Type species.—Paraceltites elegans Girty, 1908
Paraceltites cf. elegans Girty
Figs. 7.12–7.14
cf. Paraceltites elegans Girty, 1908, p. 499, pl. 25, figs.
12–14; Plummer and Scott, 1937, p. 367, pl. 37, figs.
1–8; Miller and Furnish, 1940, p. 67, pl. 22, figs. 1–10,
text-fig. 17B; Yanagisawa, 1967, p. 103, pl. 3, fig. 11;
Spinosa et al., 1975, p. 249, pl. 1, pl. 2, figs. 1–7, pl.
3, figs. 1–9, text-figs. 3, 4, 5C, 10A, 11, 12; Zhao andZheng, 1977, p. 248, pl. 5, figs. 11, 12; Liang and Guo,
1982, p. 278, pl. 106, figs. 8, 9; Zheng, 1984, p. 191,
pl. 1, figs. 1–7, text-figs. 8a, 8b; Misaki and Ehiro,
2004, p. 136, fig. 8.3; Ehiro and Misaki, 2005, p. 11,
figs. 6.8–6.9.
Material.—IGPS coll. cat. no. 112537–112540.
Descriptive remarks.—Four elliptically deformed
specimens are examined. They are mostly outer mold andthe maximum shell diameter ranges from 14 to 29 mm. The
shells are evolute, with the ratios of UD/D about 0.5, andthinly discoidal with nearly flat to slightly convex sides. The
umbilicus is shallow and the umbilical shoulder is acutely
rounded. The venter seems to be rounded with roundedventral shoulders. The shell surface is ornamented by finesinuous ribs, which fade out near the ventral shoulder. The
suture is not preserved.
Based on the shell shape and the surface ornamentation,
the present specimens are comparable with Paraceltites
elegans Girty, 1908. The precise specific identification,
however, is difficult, because they are rather poorly
preserved and the suture is unknown.
Occurrence.—Middle part of the Kashiwadaira Memberof the Takakurayama Formation at G2-valley (T7 Locality),eastern slope of Mt. Takakurayama, Yaguki, Iwaki City,
Fukushima Prefecture. Middle Permian (Wordian).

Discussion
Faunal composition of cephalopods from the
Takakurayama Formation

As discussed in the stratigraphic section, cephalopod

fossils of the Takakurayama Formation came from threehorizons: the lower part (T1: B-valley) and middle part (T7:
G2-valley, and T8: H-valley) of the Kashiwadaira Member.
The T8 Locality is isolated and its exact stratigraphic relation
with T 7 Locality is unknown. In this paper, eight species
belonging to four genera of coiled nautiloids, including
some questionable ones, and nine species belonging
to eight genera of ammonoids and an indeterminable
Kufengoceratinae are described from the T 1 and T 7
localities. In the ammonoid fauna, Propinacoceras (including
questionable ones) is most abundant (more than twenty
specimens) and Agathiceras is the second (eleven). Others
are less than six specimens each. The faunal compositionsof the two horizons are as follows:
T1 Locality:
N a u t i l o i d s : P l e u r o n a u t i l u s c h i s a t o i s p . n o v. ,Pleuronautilus cf. gregarius (Miller)
Ammonoids: Agathiceras sp., Jilingites cf. bidentus
Liang, Roadoceras cf. roadense (Böse),Propinacoceras sp., Propinacoceras? sp.
T7 Locality:
Nautiloids: Tainoceras cf. abukumaense Hayasaka,
Tainoceras sp., Pleuronautilus cf. gregarius (Miller),
Pleuronautilus sp., Pleuronautilus? sp., Endolobus?
sp., Domatoceras sp.
Ammonoids: Agathiceras sp., Stacheocerassp., Kufengoceratinae gen. and sp. indet.,
Waagenoceras sp., Jilingites cf. bidentus Liang,
Neopopanoceras cf. scrobiculatum (Gemmellaro),
Propinacoceras sp., Propinacoceras? sp.,
Paraceltites cf. elegans Girty
In addition, some coiled nautiloid species have been
described from the Takakurayama Formation. Hayasaka(1957, 1965) described Tainoceras abukumaense Hayasaka,
T. aff. unklesbayi Miller and Youngquist and Tylonautilus
p e r m i c u s H a y a s a k a . Ya n a g i s a w a ( 1 9 6 7 ) r e p o r t e d
Foordiceras gregarium (Miller) (= Pleuronautilus gregarius).
The last specimen is, however, very poorly preserved, andfragmental, so its specific identification seems to be difficult.
These species are collected from the T7 Locality.
Ehiro (2008) described five genera of ammonoids fromthe T 7 Locality: Agathiceras, Jilingites?, Waagenoceras,
Popanoceras and Tauroceras (= Neopopanoceras). He also
reviewed and arranged the ammonoid fauna previously
reported from the Takakurayama Formation by Hayasaka(1965), Yanagisawa (1967), Koizumi (1975), Tokai Fossil
Society (1995) and Tazawa et al. (2005), and recognized
17 species belong to 13 genera and a questionable
Medlicottidae from the formation. They are:
T1 Locality: Roadoceras sp., Paraceltites aff. elegans
Girty
T 7 Locality: Agathiceras cf. suessi Gemmellaro,Middle Permian cephalopods of the Takakurayama Formation, South Kitakami Belt, Northeast Japan
Agathiceras sp., Popanoceras sp., Tauroceras sp.
(= Neopopanoceras), Stacheoceras aff. grunwaldti
Gemmellaro, Waagenoceras sp., Mexicoceras?
sp., Newellites richardsoni (Miller and Furnish),
Jilingites? sp., Altudoceras sp., Propinacoceras
aff. knighti Miller and Furnish, Propinacocerassp., Medlicottia cf. costellifera Miller and Furnish,
Medlicottidae? gen. and sp. indet., Paraceltites sp.
T8 Locality: Paraceltites elegans Girty
H o w e v e r, s o m e d o u b t r e m a i n s o n t h e s p e c i f i c
assignments of the genera Agathiceras, Stacheoceras andMedlicottia, because they are ill preserved and severely
deformed. And, moreover, the generic assignment ofMedlicottia by Yanagisawa (1967) is questionable, since it isfragmental, deformed specimens without suture line.
Later, Fujikawa and Suzuki (2011) reported someammonoids from the T1 Locality, such as Thalassoceras?
sp., Agathiceras sp., Paragastrioceras? sp. and Artinskia sp.
This generic identification has, however, some problems.
The specimens assigned to Thalassoceras? sp. andParagastrioceras? sp. are rather ill preserved to identify itat the generic level. Moreover, generic identification of their
Artinskia specimens is questionable. Because, according totheir figures, 1) these specimens have two rows of nodes
on the venter to ventral shoulder, and they do not extend to
the lateral part. 2) Although it is only partly preserved, theventrolateral saddle of the external suture is simple and low.
These features, especially the shape of the ventrolateralsaddle of the suture, completely differ from those of thegenus Artinskia, and, instead, indicate that these specimens
belong to any genera of subfamily Propinacoceratinae,
such as Bamyaniceras Termier and Termier, 1970,
Difuntites Glenister and Furnish, 1988 and Propinacoceras
Gemmellaro, 1887.
Therefore, the generic compositions of each cephalopod
locality in the Kashiwadaira Member of the Takakurayama
Formation are as follows:
T 1 Locality: Pleuronautilus, Agathiceras, Jilingites,
Roadoceras, Propinacoceras and Paraceltites.
T7 Locality: Tainoceras, Pleuronautilus, Endolobus?,
Domatoceras, Agathiceras, Stacheoceras,
Kufengoceratinae, Waagenoceras, Mexicoceras?,
Newellites, Jilingites, Popanoceras,
Neopopanoceras, Altudoceras, Propinacoceras,
Medlicottia? and Paraceltites.
T8 Locality: Paraceltites.
Of the cephalopod faunas from the Takakurayama
Formation, the fauna of the T7 Locality is rather diverse,
whereas the rest are less variety. Genera of the T1 and T8
localities are, except for Roadoceras, included in the faunaof the T7 Locality, and there is no remarkable difference ingeneric compositions in these faunas.

Age of the cephalopod fauna and Takakurayama
Formation

35

Of the nautiloid genera of the Kashiwadaira Member,including the previously described ones, Tainoceras,
Pleuronautilus and Domatoceras are long ranging from Late
Carboniferous to Permian or Triassic. Tylonautilus is rather
rare genus and only known from the Lower Carboniferous
and from the Takakurayama Formation. The stratigraphic
range of the genus Endolobus is generally considered tobe restricted in the Kungurian. Occurrences of Endolobus,
however, have also been reported from the Wuchiapingian ofSouth China (Zhao et al., 1978) and from the Changhsingianof South China and Iran (Korn et al., 2019). They were notdescribed, but their conch parameters were shown in table
S1 of Korn et al. (2019).
The present paper confirmed the occurrences ofeight genera of ammonoid (Agathiceras, Stacheoceras,
Waagenoceras, Jilingites, Neopopanoceras, Roadoceras,
Propinacoceras and Paraceltites) and added
Kufengoceratinae gen. and sp. indet. in the ammonoid
fauna of the Takakurayama Formation arranged by Ehiro(2008). In addition, five genera have also been known fromthe formation: Mexicoceras?, Newellites, Popanoceras,
Altudoceras and Medlicottia?
As discussed by Ehiro (2008), the ammonoid fauna fromthe Takakurayama Formation is Wordian in age. Additional
Kufengoceratinae does not conflict with this conclusion,
because it ranges from the Roadian to Capitanian(Lopingian?). Fujikawa and Suzuki (2011) reported someammonoids from the T1 Locality, including Artinskia sp.,and concluded that this fauna indicates an Early Permian(Sakmarian–Artinskian) age. As discussed above, however,their generic identification of their Artinskia specimens
is incorrect, and it belongs to any genera of subfamily
Propinacoceratinae, most probably Propinacoceras, whichranges up to the middle–upper Permian.
Among the Takakurayama ammonoids, Jilingites (ranges
from Wordian to Capitanian), Waagenoceras (Wordian to
Capitanian), Newellites (Wordian), Mexicoceras (Roadian to
Wordian), Altudoceras (Roadian to Capitanian), Roadoceras(Wordian to Wuchiapingian) and Neopopanoceras (Wordian)strongly support the Wordian age of the fauna.
On the other hand, Tazawa et al. (2005, 2015) regarded
almost all fossils from the Takakurayama Formation are
reworked, except for very few brachiopod specimens which
are considered to be Lopingian in age. As discussed by
Ehiro (2008), this interpretation has no sedimentologicalevidence. The Takakurayama Formation includes some
pebbly mudstone, but the fossil horizons are composed of
massive or sharply laminated mudstone. Almost all fossils,
such as trilobites, brachiopods, gastropods, bivalves,nautiloids and ammonoids, except for some fusulinoideans

36

Masayuki Ehiro

Figure 8. Stratigraphic ranges of
the cephalopod genera known fromthe Takakurayama Formation. Data
from Arkell et al. (1957), Furnish et al.
(2009), Kummel (1953), Miller et al.
(1957) and others.

and corals from the limestone pebbles and boulders in
the Motomura Member, have similar state of preservation.
They are usually well preserved, although suffered severe
tectonic deformation. Some specimens are fragmental,
but this is mainly due to the damage during the sampling
process. Therefore, the age of the Takakurayama Formation(Kashiwadaira Member) is Wordian as shown by theammonoid fauna. I think there is a large possibility that these“Lopingian” brachiopods actually range down into the Middle
Permian.
The Takakurayama fauna, comprising four genera ofnautiloid and fourteen genera of ammonoid, is the mostdiverse Wordian cephalopod fauna in Japan. It is far morethan a next diverse fauna from the uppermost part of the
Hosoo Formation, which is composed of six ammonoid
genera (Ehiro, 2010) with some nautiloids, distributed in thesouthern part of the Kitakami Massif, also belongs to theSouth Kitakami Belt.

Acknowledgments
I am greatly indebted to Mr. Chisato Suzuki for donating
cephalopod specimens from the Takakurayama Formationand help in the field. I also thank to the board of education,
Iwaki City for allowing to conduct a geological survey inthe area designated as a natural monument of Iwaki City
(Takakurayama Paleozoic Strata). Sincere thanks areextended to Tatyana B. Leonova for her careful review.

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