Bull. Tohoku Univ. Museum, No.8, pp.1‑8, 2008
Ⓒ by The Tohoku University Museum

Two genera of Popanoceratidae (Permian Ammonoidea) from theSouth Kitakami Belt,Northeast Japan,with a note on the age ofthe
Takakurayama Formation in the Abukuma Massif
MASAYUKI EHIROThe Tohoku University Museum, Sendai 980‑8578, Japan
Abstract. Two genera of Permian ammonoid Popanoceratidae are described from the South Kitakami
Belt, Northeast Japan: Tauroceras from the uppermost part of the Hosoo Formation in the Southern
Kitakami Massif, and Popanoceras and Tauroceras, associated with Jilingites?, Waagenoceras andAgathiceras, from the upper part of the Takakurayama Formation in the eastern marginal part of the
Abukuma Massif. These ammonoid specimens are considered in situ occurrences and stronglysuggestthat these fossil horizons are both Wordian in age.
Introduction
Popanoceratidae is ratherrare in the Permian strata oftheJapanese Islands,although it is a common ammonoid family
in Permian deposits of the Urals, Tethys Province andsouthwestern United States. Only two specimens havepreviously been described from the South Kitakami Belt ofNortheast Japan: Popanoceras sp.(Hayasaka,1965)from the
Takakurayama Formation (Takakurayama Group) in theeastern marginal part ofthe Abukuma Massifand Tauroceras? sp.(Ehiro and Misaki,2005)from the Hosoo Formation in
the Kesennuma area of the Southern Kitakami Massif. In
addition to these specimens Hayasaka and Nishikawa (1962)
once reported the occurrence of Popanoceras bowmani(Bose)from unnamed strata in Miharanoro,Hiroshima Prefecture in Southwest Japan. This species has, however, notbeen described.
Genera belonging to Popanoceratidae are fundamental tothe biostratigraphy of Lower to Middle Permian strata(Glenister and Furnish, 1988). Among them, Tauroceras isalso important with respect to biogeography because it ismainly known from Tethys Province and the southwestern
United States. Recently one specimen of Popanoceras sp.
(from the Takakurayama Formation)and two of Taurocerassp. (from the Takakurayama and Hosoo Formations) wererecovered from the South Kitakami Belt (Fig.1). This paper
describes these of Popanoceratidae and some associatedammonoids,and discusses theirstratigraphic and biogeographic significance, especially with respect to the age of the
Takakurayama Formation in the Abukuma Massif.
Brief note on the ammonoid‑bearing formations
and their ammonoid faunas
The Hosoo Formation
The Hosoo Formation is in the Kesennuma area of theSouthern KitakamiMassif(Fig.2). The Permian strata ofthearea are divided into the Nakadaira, Hosoo, Kamiyasse,
Kurosawa and Nabekoshiyama Formations from the lowerto
upper positions (Misaki and Ehiro, 2004). The stratigraphic
relationships of these formations are all conformable. The
Nakadaira Formation, Sakmarian to Artinskian in age, consists predominantly of limestone intercalated with conglomerate, sandstone and mudstone. The thickness exceeds
300 m. The Hosoo Formation, 400‑500 m thick,is primarily
a mudstone unit with some lenticular sandstone and conglomerate beds. The Kamiyasse Formation ranges in thickness from 200 to 300 m and is dominated by calcareous
sandstone, calcareous mudstone and impure limestone.
This formation yields many fusulinoideans, corals, brachiopods,mollusks and other fossils,and can be correlatedwith the Wordian to Capitanian interval. The Kurosawa
Formation,Capitanian to Wuchiapingian in age,is composed
mainlyofmudstone and its total thickness exceeds 1,000 m.
The Nabekoshiyama Formation, more than 500 m thick, iscomposed of a sandstone‑dominated lower part and mudstone‑dominated upper part. Limestone intercalated in thelower part yields Changhsingian fusulinoideans and smaller
foraminifers.
The Hosoo Formation has long been considered to bealmost barren offossils,but Ehiro and Misaki(2005)reported
severalammonoid fossils from the middle and upperparts ofthe formation. The middle part yields Demarezites sp.,
Demarezites? sp., Agathiceras? sp. and Adrianites sp.
Ammonoids from the upper part are known from two localities. Waagenoceras sp., Cardiella sp., Agathiceras sp., andParaceltites elegans Girtywere collected on the eastern ridgeof the Ookadozawa valley,a tributaryof the Hosoo River in
Kamiyasse district. The other locality(localityH‑5 ofEhiro
and Misaki, 2005)is a road‑cut along a forest road in thesouthern basin of the Shigejizawa River in the same district
and yields Parastacheoceras bidentatus Ehiro and Misaki,
Tauroceras? sp.and Agathiceras sp. The present specimenof Tauroceras sp.was collected from the latter locality(loc.

Masayuki Ehiro

Figure 1. Map showing the studyareas with the
pre‑Tertiary tectonic division of Northeast Japan.
H‑5 in Fig.2).
The Takakurayama Formation
The Takakurayama Formation is in east of Mt.Takakurayama in the Yaguki area, the southeastern margin of the
Abukuma Massif (Fig.3). It was first proposed as the
Takakurayama Series (Iwao and Matsui,1961). Yanagisawa
and Nemoto (1961)called it the Takakurayama Group andsubdivided it into the Iriishikura,Motomura and Kashiwadaira
Formations, in ascending order. However, Onuki (1966)
treated the group as a formation rank and the formations as
members. The Iriishikura Memberis more than 100 m thickand consists mainlyoflaminated mudstone. The Motomura
Memberis 60‑7 m,thinning to the south,and is composed ofsandstone,conglomeratic sandstone with limestone pebbles,and mudstone. The Kashiwadaira Member,more than 200
m thick, consists of laminated mudstone occasionally associated with thin sandstones and lenticular pebbly mudstones. The strata trend is north‑northeast and moderately
to steeply dip west. Cross beddings and graded beddings,
commonly observed in sandstone beds and laminas, showthat no overturned part exists.
Popanoceras sp. and Tauroceras sp. described in thispaperwere collected from the upperpart ofthe Kashiwadai-ra Member in the G2 River (loc.T of Yanagisawa,1967)in
association with some ammonoids, such as Jilingites? sp.,
Waagenoceras sp., Agathiceras sp. (many specimens), andsome unidentifiable specimens. Many ammonoid species
from this localityhave previouslybeen reported byHayasaka(1965), Yanagisawa (1967), and Tazawa et al. (2005). They
are as follows :Hayasaka (1965):
Agathiceras cf.suessi Gemmellaro
Popanoceras sp.
Stacheoceras aff.grunwaldti Gemmellaro
Waagenoceras cf. dieneri richardsoni Miller andFurnishPseudogastrioceras? sp.
Propinacoceras sp.
Medlicottidae? gen.et sp.indet.
Paraceltites aff.elegans Girty
Yanagisawa (1967):
Agathiceras cf.suessi Gemmellaro
Waagenoceras cf.dieneri Miller and Furnish
Propinacoceras aff.knighti Miller and Furnish
Medlicottia cf.costellifera Miller and Furnish
Paraceltites elegans Girty
P. aff.elegans Girty
Paraceltites sp.
Cibolites cf.uddeni Plummer and Scott.
Tazawa et al.(2005):
Agathiceras sp.
Roadoceras sp.
Mexicoceras? sp. (＝Waagenoceras cf. dieneri of
Yanagisawa (1967))
Propinacoceras sp.
Of these ammonoids, Waagenoceras dieneri richardsoni
Miller and Furnish was treated as Newellites richardsoni(Miller and Furnish)by Davis et al. (1969). Hayasaka (1965)
described two specimens of Pseudogastrioceras? sp. andnoted that one of them might be P.zittelli Gemmellaro.
Species previously considered members of Pseudogastrioceras Spath, 1930 are placed in three genera :Altudoceras Ruzhentsev, 1940, Pseudogastrioceras Spath,and Roadoceras Zhou, 1985. Pseudogastrioceras zittelli istreated as a species of Altudoceras (Zhou, 1987).
Hayasakaʼ
s (1965)two specimens ofPseudogastrioceras?sp.,
however, are fragmental or very poorly preserved, and are
difficult to identify on the generic level.
Cibolites sp.described byYanagisawa (1967),reexaminedby the present author, is not an ammonoid but probably agastropod because it has a spiral shell.
In addition to those described,three ammonoid specimens
collected by C.Suzuki from the same locality are known.
Koizumi(1975,p 73,pl.16,fig.2)identified one as Timorites?
sp. This specimen,having a diameterofabout 45 mm,hasa small umbilicus (UD/D is about 0.24). Prominent sinuous
fine ribs are present on the flanks,and radiallyelongated pits
occur in the central part of the lateral side. From thesecharacters, this specimen probably belongs to Tauroceras,
although a specific identification is difficult. The rest wereidentified as Pseudotirolites? sp. and Pseudogastrioceras
zittelli (Tokai Fossil Society, 1995, p.50). The former is anPopanoceratidae from South Kitakami

Figure 2. Geologic map around the Shigejisawa River, north of Kesennuma (from Ehiro and Misaki,2005). H‑5 is the ammonoid locality.

outer mould of evolute conch,the side of which is flattened
and has some radiallyelongated pits at the midpoint,and isalso Tauroceras. The shell of the latter specimen is small(D＝35 mm) with a small umbilicus (UD/D＝about 0.25).
Fine longitudinal ribs are present on the broadly roundedsides and venter, and fine, short radial ribs occur on theumbilical edge. From these characters this specimen isconsidered to be a species of Roadoceras, but specificidentification is impossible.
Therefore,the Kashiwadaira ammonoid fauna consists ofthe following 12 genera: Agathiceras, Popanoceras, Tauroceras,Stacheoceras,Mexicoceras?,Waagenoceras,Newellites, Altudoceras, Roadoceras, Propinacoceras, Medlicottia,
and Paraceltites.
Age of the fauna and ammonoid‑bearing formations
Popanoceras Hyatt, 1884 ranges from the Artinskian toRoadian (Leonova,2002)and is abundant in the Artinskian to
Kungurian of the Southern Urals, Timor, Tumara RiverMasayuki Ehiro

Figure 3. Geologic map of the Yaguki area. Valley names are from Yanagisawa (1967).

basin,west and central Texas,and common in the Roadianstrata in western Australia,and the Canadian arctic(Glenisterand Furnish,1988). Tauroceras Toumanskaya,1938 ranges
from the Roadian to Wordian (Leonova,2002)but dominatesin the Wordian. It is widely known from Tethys Province,
including Sicily, Tunisia, Cremea, Pamir, Oman, Iraq, Afghanistan, Malaysia, Timor, Xizang and Zejiang (Kullmann etal., 2000). It has also been reported from Texas and Jilingin Inner Mongolia.
Ehiro and Misaki (2005), based on the ammonoid fauna,correlated the middle and upper parts of the Hosoo Formation with the Roadian and Wordian, respectively. The
present Tauroceras sp.specimen from the upper part supports this correlation.
Hayasaka (1965) correlated the Takakurayama Formation
with the Socio Stage (Roadian? ⎜ Wordian). Yanagisawa
considered the Motomura Member to be Early Permian inage based on such Early Permian fusulinoideans as

Pseudofusulina cf. ambigua, P. cf. fusiformis, and Chalaroschwagerina cf. vulgaris from limestone pebbles in themember. These fusulinoideans are, however, derived fossils,because some limestone pebbles yield Middle Permian
fusulinoideans (Ueno, 1992). Ueno (1992) correlated theMotomura Member with the late Murgabian on the groundsof the occurrence of Colania sp.Tazawa et al. (2005) considered the ammonoid fauna from the Kashiwadaira Member
to be Wordian in age, but identified these ammonoids asderived and concluded that the age of the Kashiwadaira
Member is Late Permian, because the Capitanian
fusulinoidean genus Lepidolina was reported from the basal
part of the member (Murata, 1964).
The ammonoid fauna of the Kashiwadaira Formation isrich in Agathiceras,which ranges from the Moscovian (Carboniferous) to Wordian. Stacheoceras is known from Artinskian to Changhsingian strata. Waagenoceras is an index
fossilofthe Wordian,although it ranges up to the Capitanian.

Popanoceratidae from South Kitakami
The monospecific genus Newellites is Wordian in age.
Altudoceras ranges from Roadian to Capitanian andRoadoceras from Wordian to Wuchiapingian. Propinacoceras is an Artinskian ⎜ Wordian and Medlicottia is a Sakmarian ⎜ Wordian genus. Paraceltites predominates in
Roadian ⎜ Wordian strata, although a few specimens are
known from the Wuchiapingian. The range ofMexicoceras
is from Roadian to Wordian.
In addition to these data the occurrence of Tauroceras
strongly suggests that this ammonoid fauna is Wordian.
Onlythe traditional range of the genus Popanoceras (Artinskian to Roadian)conflicts with this age assignment. Therefore, the upper part of the Kashiwadaira Member is mostcertainly early Wordian of the Middle Permian. This age
assignment is consistent with Hayasaka (1965), but differs
greatlyfrom Tazawa et al.(2005). Tazawa et al.(2005)also
considered the age of the ammonoid fauna from the Kashiwadaira Member to be Wordian, but interpreted theseammonoid fossils and otherfossils from the memberto be all
reworked and the Kashiwadaira Memberto be Late Permianin age.
I do not accept Tazawa et al.ʼs (2005)interpretation thatthe ammonoid fossils from the Kashiwadaira Member are
reworked for the following reasons.
1) Tazawa et al.ʼs (2005)interpretation is mainlybased on
the occurrence ofCapitanian fusulinoidean fossils such as
Lepidolina multiseptata Deprat and Lepidolina sp. from ahorizon about 70 m belowthe ammonoid horizon (Murata,
1964). In this case, the fusulinoidean age is certainlyinconsistent with the age ofthe ammonoid fauna. Thesefusulinoideans,however,have neither been described nor
figured and need more consideration.
2) Naturalcasts ofthe ammonoid fossils (and otherfossils
such as trilobites and bivalves) consist ofblack mudstone
having exactly the same lithology as the fossil‑bearing
bed.
3) Most ammonoid specimens are not fragmented and arein a rather good state of preservation, although some ofthem are tectonicallydeformed. Trilobite fossils from thesame localityare also betterpreserved compared to otherlocalities such as Kamiyasse and Imo in the South Kitakami Belt.
4) Some pebbly mudstone beds are intercalated in the
Kashiwadaira Member, but there are no exotic pebbles
occur in the ammonoid‑bearing bed.
5) A ratherlarge numberofammonoid specimens,at least
30 specimens having a common stratigraphic range,havebeen collected from the locality,which is one ofthe mostproductive ammonoid localities from the Permian of theSouth Kitakami Belt. Are these all reworked?
The points in items 2,3,4 and 5 stronglyindicate that theammonoid fossils from locality T of the Kashiwadaira
Member are in situ and the ammonoid‑bearing stratum iscorrelatable with the Wordian.
Ueno (1992)dated the underlying Motomura Member aslate Murgabian based on the occurrence of late Murgabianfusulinoideans such as Minojapanella (M.) parva Sheng andWutuella cf.wutuensis (Kuo)from the limestone pebbles andColania sp.from the calcareous matrix of the conglomeratic

sandstone. The Tethyan standard stage Murgabian isgenerally correlated with the Wordian Stage. In this case,the ammonoid‑ and fusulinoidean‑based age assignmentsof the Kashiwadaira Member are approximately consistent,
because the Kashiwadaira Memberconformablyoverlies theMotomura Member and the ages ofthese two members arethought to be about the same. The Kashiwadaira ammonoid fauna, however, includes Popanoceras, which was
known from pre‑Wordian strata previously,and is more likely
correlatable with the lowerpart ofthe Wordian. This somewhat contradictory age relationship between ammonoid‑
and fusulinoidean‑based strata remains a problem to beresolved.
Systematic Paleontology
Subclass Ammonoidea Agassiz,1847
Order Goniatitida Hyatt,1884
Suborder Goniatitina Hyatt,1884
Superfamily Marathonitoidea Ruzhentsev,1938
Family Marathonitidae Ruzhentsev,1938
Genus Jilingites Liang,1982
Type species : Jilingites bidentus Liang,1982
Jilingites? sp.
Figures 4.1,5.1
Material.⎜ IGPS coll.cat.no.109888
Remarks.⎜ A fragmental specimen, obliquely flattened
tectonically, is at hand. The conch has broadly roundedsides with a rounded venterand a smallorclosed umbilicus.
The suture partlypreserved has at least foursets ofroundedsaddles and bifid lobes. From these features,especiallyby
suture shape,this specimen probably belongs to the genus
Jilingites.
Occurrence and geological age.⎜ From the upper part of
the Kashiwadaira Member of the Takakurayama Formationin the G2 river(loc. T of Yanagisawa, 1967), Yaguki, Iwaki
City,Fukushima Prefecture.Middle Permian Wordian.
Superfamily Cycloloboidea von Zittel,1895
Family Cyclolobidae von Zittel,1895
Subfamily Cyclolobinae von Zittel,1895
Genus Waagenoceras Gemmellaro, 1887
Type species : Waagenoceras mojsisovicsi Gemmellaro,
1887
Waagenoceras sp.
Figures 4.2a‑c,5.2
Material.⎜ IGPS coll.cat.no.109889
Remarks.⎜ A ventrally flattened specimen is at hand.
The original shell form is estimated to be subglobularwith asmall umbilicus and rounded venter, although it suffered asevere tectonic deformation. The shell surface is smooth.
The suture is poorly preserved but typical for advanced
cyclolobids and has a wide ventral lobe divided by highdenticulate median saddle. High lateral saddles haveentirely rounded apices. Deep lateral lobes are strongly

Masayuki Ehiro

Figure 4. Ammonoid fossils from the Kesennuma and Yaguki areas.
1. Jilingites? sp.,IGPS coll.cat.no.109888,lateralview, ×1.5 ; 2a‑c. Waagenoceras sp.,IGPS coll.
cat. no.109889, ×1.0 ; 3. Popanoceras sp., IGPS coll. cat. no.108990, ×1.5 ; 4, 5. Tauroceras sp., 4.
IGPS coll.cat.no. 109891, ×1.5, 5.IGPS coll.cat.no.108992, ×1.0 ; 6‑8. Agathiceras sp., 6.IGPS coll.
cat. no.109893, ×1.5, 7. IGPS coll. cat. no. 109894, ×2.0, 8. IGPS coll. cat. no. 109895, ×2.0.

denticulate. At least five, probably six, lateral lobes arepresent. Based on these characteristics,the present specimen is considered to belong to the genus Waagenoceras.
Occurrence and geological age.⎜ From the upper part of
the Kashiwadaira Member of the Takakurayama Formationin the G2 river(loc. T of Yanagisawa, 1967), Yaguki, Iwaki
City,Fukushima Prefecture.Middle Permian Wordian.

Superfamily Popanoceratoidea Hyatt,1900
Family Popanoceratidae Hyatt,1900
Genus Popanoceras Hyatt,1884
Type species : Goniatites sobolewskyanus de Verneuil in
Murchison et al.,1845
Popanoceras sp.
Figures 4.3,5.3
Material.⎜ IGPS coll.cat.no.109890
Description.⎜ The shell is thinly discoidal with flat sides
and acutelyrounded? venter. It is small,having a maximum
diameter of about 26 mm and a corresponding umbilicalPopanoceratidae from South Kitakami
examined. The shell shape of the small specimen (IGPS
coll. cat. no. 109891) is discoidal, involute, with a smallumbilicus. The maximum diameteris estimated to be about
38 mm, and the corresponding height, width, and umbilical
diameter are about 18, 2.5 and 6.5 mm, respectively. The
flanks and venter are flattened with abruptly roundedventrolateral shoulders. Sinuous, fine and dense ribs areprominent on the flat flanks, forming a deep ventral sinus.
About 40 ribs occur per one‑fourth of a volution. Radiallyelongated pits are also noteworthy at the midpoint of thelateralside ofthe innermould. The suture is not preserved.
The large specimen (IGPS coll. cat. no. 109892)is fragmental, only the outer flank is preserved. It exceeds adiameter of 100 mm. The broad flanks and narrow venter,
about 9 mm wide, are nearly flat to broadly rounded withrounded ventrolateralshoulders. Manyfine prominent sinuous ribs are on the flanks. The suture is not preserved.
From these characters these specimens are undoubtedly
Tauroceras,but are difficult to identify at the specific level.
Occurrence and geological age.⎜ IGPS coll. cat. no.
109891 from the upper part of the Kashiwadaira Member of
the Takakurayama Formation in the G2 river (loc. T of
Yanagisawa, 1967), Yaguki, Iwaki City, Fukushima Prefecture.⎜ IGPS coll.cat.no.109892 from the uppermost part of
the Hosoo Formation at a road‑cut along a forest road (loc.
H‑5 of Ehiro and Misaki,2005)in the southern basin of the
Shigejizawa River,Kesennuma City,Miyagi Prefecture.
Figure 5. Suture lines of Jilingites?,
Waagenoceras, Popanoceras and Agathiceras.
1. Jilingites? sp., IGPS coll. cat. no. 109888 ; 2.
Waagenoceras sp., IGPS coll. cat. no.109889 ; 3.
Popanoceras sp., IGPS coll. cat. no. 108990 ; 4.
Agathiceras sp., IGPS coll. cat. no.108993

diameter ofabout 6 mm. Transverse,slightlyprojected fineribs,each tracing a rounded ventral sinus,are on the lateralsides. Thirteen or 14 ribs are present per one‑fourth of a
volution. The suture is partly poorly preserved. The wide
ventral lobe is divided bya median saddle into two strongly
tridenticulated? branches. The median saddle is about half
the height ofthe ventral lobe. The first laterallobe is trifid?
having nearly the same width as the prongs of the ventral
lobe. Second lateral lobe is also trifid. All saddles arerounded.
Occurrence and geological age.⎜ From the upper part of
the Kashiwadaira Member of the Takakurayama Formationin the G2 river(loc. T of Yanagisawa, 1967), Yaguki, Iwaki
City,Fukushima Prefecture.Middle Permian Wordian.
Genus Tauroceras Toumanskaya,1938
Type species : Popanoceras scrobiculatum Gemmellaro,1887
Tauroceras sp.
Figures 4.4‑5
Material.⎜ Two specimens, IGPS coll. cat. nos. 109891
and 109892
Description.⎜ Small and rather large specimens are

Superfamily Agathiceratoidea Arthaber,1911
Family Agathiceratidae Arthaber,1911
Genus Agathiceras Gemmellaro,1887
Type species : Agathiceras suessi Gemmellaro,1887
Agathiceras sp.
Figures 4.6‑8,5.4
Material⎜ IGPS coll.cat.nos.109893,109894,and 109895
Description.⎜ Specimens smallto moderate size; diameter 23‑30 mm. Conch is involute and due to tectonic
deformation, thinly discoidal to spherical in outline, with analmost closed umbilicus. The sides of the shell are flat orslightlyconvex and umbilicalshoulders are rounded. Venteris convex with rounded ventrolateral shoulders. Shell surface is ornamented bymanyfine spiral lirae. The suture ispoorly preserved in one specimen (no. 109893), and four
rounded saddles and three almost rounded lobes are present
on the lateral side.
Occurrence and geological age.⎜ From the lower part of
the Kashiwadaira Member of the Takakurayama Formationin the G2 river(loc. T of Yanagisawa, 1967), Yaguki, Iwaki
City,Fukushima Prefecture.Middle Permian Wordian.
Acknowledgments
I thank to Professor Emeritus Kei Mori of the Tohoku
Universityforhis kind review ofthe manuscript,the board ofeducation,IwakiCityforallowing me to conduct a geologicalsurveyin the Yakuki area,Mr.Chisato Suzuki forhis help in
the field,and Mr.Yuta Shiino forproviding a specimen. This

Masayuki Ehiro
study was financially supported by the Saito Gratitude
Foundation (2000),Sendai,Japan.
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