This study describes a brachiopod fauna, consisting of 22 species in 19 genera, from the Upper Permian (Lopingian) Mizukoshi Formation in the Mizukoshi area of central Kyushu, southwest Japan. The fauna includes three new species: Anidanthus mizukoshiensis, Terrakea yanagidai and Rhynchopora matsumotoi. The Mizukoshi fauna is a Boreal-Tethyan mixed fauna allied with the Middle Permian brachiopod faunas of central Japan (Hida Gaien Belt), northeast Japan (South Kitakami Belt) and eastern Russia (South Primorye). Palaeobiogeographical data on the Mizukoshi fauna suggest that during the Middle-Late Permian the Mizukoshi area was located between the Hida Gaien region to the north and the South Kitakami region to the south, bordering the eastern margin of North China (Sino-Korea). This conclusion supports a strikeslip model that describes largescale sinistral strikeslip movement along the Tanakura Tectonic Line (TTL)-Median Tectonic Line (MTL) from the Early Cretaceous to Palaeogene.
Introduction
The Mizukoshi area, located approximately 20 km SE of Kumamoto, central Kyushu, southwest Japan (Figure 1), is one of the most famous Permian brachiopod fossil localities in Japan. Yanagida (1963) described the following three brachiopod species from the upper part of the Mizukoshi Formation in this area: Linoproductus cf. lineatus (Waagen), Neospirifer fasciger Keyserling and Spiriferella keilhavii (von Buch). Yanagida noted that the Mizukoshi fauna is comparable in specific composition to the Middle and Upper Permian brachiopod faunas of the lower Kanokura Formation in the South Kitakami Belt, northeast Japan; the Maizuru Group in the Maizuru Belt, southwest Japan; the Chandalaz Formation in South Primorye, Far East Russia; and the upper Toman Formation (= Kaishantun Formation) in eastern Jilin Province, Northeast China. On the basis of this work, Nakamura and Tazawa (1990) treated the Mizukoshi fauna as a Boreal-Tethyan mixed fauna, as with the Middle Permian brachiopod faunas of the South Kitakami, Hida Gaien, South Primorye and Jilin regions.
Figure 1.
Index map showing the study area and the fossil localities MZ-S1 and MZ-S2 (using the topographical map of “Mifune” scale 1:25,000 published by the Geographical Survey Institute of Japan).
Tazawa (1993) proposed a tectonic model of Japan, the strike-slip model, which involved large-scale sinistral strike-slip movement from the Early Cretaceous to Palaeogene. According to Tazawa (2001a, 2004), the sinistral strike-slip movement generated 1,500–2,000 km of displacement along the Tanakura Tectonic Line (TTL)-Median Tectonic Line (MTL) and a marked rearrangement of the pre-Cretaceous terranes of Japan. Given the specifics of this hypothesis, it was expected that the Mizukoshi Formation, with its Boreal-Tethyan mixed brachiopod fauna, would provide important evidence for the strike-slip model as the link between the Permian rocks of the Hida Gaien Belt and the South Kitakami Belt; however, investigation by Yanagida (1963) and Tazawa and Hasegawa (2007) revealed only three species within the Mizukoshi fauna, making it too poor to provide meaningful evidence relevant to the strike-slip model.
With the help of a student (S. Hasegawa), I collected a number of brachiopod specimens from the upper part of the Mizukoshi Formation over the period from 2001 to 2005. The purpose of the present study is to describe all of the available brachiopod material of the Mizukoshi fauna and thereby discuss the age and palaeobiogeography of this fauna and its bearing on the pre-Neogene tectonics of Japan. All of the specimens described in this paper are housed in the following institutions, as indicated by the prefixes assigned to the registered specimen numbers: GK-D, Kyushu University Museum in Fukuoka; NU-B, Department of Geology, Faculty of Science, Niigata University in Niigata.
Stratigraphy
Matsumoto and Huzimoto (1939) were the first to recognize fusulinoidean-bearing Permian rocks in the Mizukoshi area, naming the shale-dominated Permian sequence the Mizukoshi Formation. Subsequently, Yanagida (1958) compiled a geological map of this area, and assigned a late Middle Permian age for the Mizukoshi Formation based on some fusulinoideans, Lepidolina cf. gubleri (Kanmera), Lepidolina cf. toriyamai Kanmera and Pseudodoliolina cf. pseudolepida (Deprat), etc., recovered from limestone blocks enclosed in the shales within the upper part of the formation.
More recently, Tazawa and Hasegawa (2007) clarified the stratigraphy of the Mizukoshi Formation. The Mizukoshi Formation is distributed throughout the Mizukoshi area, with a general ENE-WSW trend and dip toward the NNW. The formation is approximately 1,690 m in total thickness and is composed chiefly of black shale with intercalated sandstone and conglomerate, and limestone blocks (Figure 2). The black shale is lithologically similar to shales of the Upper Permian Toyoma Formation (Onuki, 1969) in the South Kitakami Belt, northeast Japan, and the upper part of the Moribu Formation (Tazawa, 2001b) in the Hida Gaien Belt, central Japan. The conglomerate in the upper part of the formation is correlated with the Usuginu-type conglomerate of the South Kitakami Belt on the basis of lithology (Kano, 1967) and the K-Ar hornblende ages (260 ± 13 Ma) of granitic clasts (Tobe et al., 2000). Brachiopods occur as reworked fossils from thin beds of sandy shale and calcareous sandstone within thick shales in the upper part of this formation. The lithology and topographic and stratigraphic details of the fossil localities MZ-S1 and MZ-S2 are as follows (see also Figures 1, 2).
Figure 2.
Generalized columnar section of the Mizukoshi Formation, showing the fossil horizons MZ-S1 and MZ-S2 (adapted from Tazawa and Hasegawa, 2007).
MZ-S1: Grey to light-brown sandy shale, 250 m above the thick sandstone of the upper part of the Mizukoshi Formation, exposed at a road-cutting along Root 219 (Yokono-Yabe Line) between Kanmegi and Mizukoshi and approximately 500 m SW of Tsuzumugi (Lat. 32°41′47″N, Long. 130°51′30″E). All of the brachiopod specimens described by Yanagida (1963) and Tazawa and Hasegawa (2007) were collected from this locality.
MZ-S2: rey sandy shale and dark-grey calcareous fine-grained sandstone, 80 m above the thick sandstone of the upper part of the Mizukoshi Formation, exposed within the western slope of a small tributary located approximately 500 m S of Tsuzumugi and 270 m SE of MZ-S1 (Lat. 32°41′41″N, Long. 130°51′39″E).
The Mizukoshi fauna
The brachiopod fauna described herein includes the following 22 species in 19 genera: Neochonetes (Zhongyingia) zhongyingensis Liao, Kitakamichonetes multicapillatus Afanasjeva and Tazawa, Capillomesolobus sp., Transennatia gratiosa (Waagen), Waagenoconcha krystofovichi (Fredericks), Waagenoconcha permocarbonica Ustritsky, Anidanthus ussuricus (Fredericks), Anidanthus mizukoshiensis sp. nov., Terrakea yanagidai sp. nov., Yakovlevia kaluzinensis Fredericks, Urushtenoidea crenulata (Ting), Permianella typica He and Zhu, Derbyia nipponica Nakamura, Acosarina cf. circular Xu, Orthotichia sp., Hustedia ratburiensis Waterhouse and Piyasin, Rhynchopora matsumotoi sp. nov., Rhynchopora sp., Gypospirifer volatilis Duan and Li, Alispiriferella lita (Fredericks), Elivina sp. and Dielasma sp. (Figure 3).
Figure 3.
Brachiopod species of the Mizukoshi fauna and their occurrences in South Kitakami (Setamai, Kamiyasse-Imo and Takakurayama), Hida Gaien (Moribu and Oguradani), South Primorye (Vladivostok and Nakhodka), Northeast China (Jilin and Heilongjiang) and Inner Mongolia (Zhesi and Xiujimqinqi). Open circle is the Boreal (bipolar) species, and solid circle is the Tethyan species.
Age and correlation
Brachiopods of the Mizukoshi fauna consist mostly of Middle Permian elements, although with some Late Permian genera and species. Neochonetes (Zhongyingia) zhongyingensis is known from the Upper Permian (Wuchiapingian) of Hunan, South China, and the Upper Permian (Lopingian) of Guizhou, South China. Acosarina cf. circular resembles A. circular, which occurs in the Upper Permian (Wuchiapingian) of Hunan, South China. It is noteworthy that all of the brachiopod fossils were reworked, probably by turbidity currents, in the Late Permian, as originally suggested by Yanagida (1958).
The following fusulinoideans and smaller foraminifers are found within limestone cobbles of the conglomerate in the upper part of the Mizukoshi Formation: Rauserella sp., Codonofusiella sp., Danbarula cascadensis (Thompson, Wheeler and Danner), Lantschichites cuniculata (Kanmera), Nankinella sp. Chusenella choshiensis Chisaka, Metadoliolina gravitesta (Kanmera), Lepidolina multiseptata (Deprat), Lepidolina shiraiwensis (Ozawa), Lepidolina kumaensis Kanmera and Colaniella sp. It is remarkable that most of the fusulinoideans are late Middle Permian (Capitanian) elements, and that the smaller foraminifer Colaniella mostly indicates a Wuchiapingian age, although it occurs also from Guadalupian beds. On the basis of these foraminifers, the age of the Mizukoshi Formation is considered to be Late Permian (Lopingian), probably Wuchiapingian, because all the foraminifers occur as reworked fossils from limestone clasts of conglomerate.
Furthermore, the K-Ar hornblende ages (260 ±13 Ma) of granitic clasts within the conglomerate in the Mizukoshi Formation indicates that the age of the conglomerate is younger than the late Middle Permian. The evidence provided by the age of the granitic clasts supports the above conclusion that a Late Permian (Lopingian), probably Wuchiapingian age can be attributed to the Mizukoshi Formation.
Palaeobiogeography and tectonic implication
Among the brachiopods listed above, Kitakamichonetes, Waagenoconcha, Anidanthus, Terrakea, Yakovlevia, Rhynchopora, Gypospirifer, Alispiriferella and Elivina are Boreal (including bipolar)-type genera, whereas Neochonetes (Zongyingia), Transennatia, Urushtenoidea, Permianella and Acosarina are Tethyan-type genera (see Figure 3); consequently, the Mizukoshi fauna is a typical Boreal-Tethyan mixed fauna, although the Boreal types are predominant. In terms of generic and specific composition, the Mizukoshi fauna has a close affinity with the Permian brachiopod faunas of northeast Japan (Setamai, Kamiyasse-Imo and Takakurayama in the South Kitakami Belt), central Japan (Moribu and Oguradani in the Hida Gaien Belt), eastern Russia (South Primorye), Northeast China (Jilin and Heilongjiang) and North China (Inner Mongolia), particularly those of the South Kitakami, Hida Gaien and South Primorye regions. All of these regions are included within the Southern Subzone of the Inner Mongolia-Japan Transitional Zone of Tazawa (1991). This subzone was probably a continental shelf bordering the northern and eastern margins of North China (Sino-Korea), located in the northern mid-latitudes during the Middle to Late Permian (Figure 4).
Figure 4.
Middle-Late Permian reconstruction map of the world (adapted from Ziegler et al., 1997). Black areas are continental shelf or continental slope. AF: Africa, AN: Antarctica, AR: Arabia, AU: Australia, E: Eurasia, G: Greenland, IC: Indochina, IN: India, L: Lhasa, M: Mongolia, NA: North America, NC: North China, Q: Qiangtang, SA: South America, SC: South China, SI: Sibumasu, T: Tarim.
The above data strongly suggest that the Mizukoshi Formation is the SW extension of the Permian rocks of the Hida Gaien Belt, thereby belonging to the South Kitakami Terrane which is characterised by Permian continental-shelf sediments with Boreal-Tethyan mixed faunas. The dominant Boreal-type assemblage in the Mizukoshi fauna indicates that during the Middle-Late Permian the Mizukoshi area was probably located between the Hida Gaien Belt to the north and the South Kitakami Belt to the south. A reconstruction of Middle-Late Permian Japan shows clearly that large-scale sinistral strike-slip faulting occurred subsequent to the Permian. This finding is in agreement with the strike-slip model proposed by Tazawa (1993, 2004), which describes large-scale (approximately 1,500–2,000 km of displacement) sinistral strike-slip faulting along the TTL-MTL during the Early Cretaceous to Palaeogene (Figure 5). The Mizukoshi fauna provides compelling evidence of large-scale sinistral strike-slip movement in Japan.
Figure 5.
Tectonic map of Japan in the present and the Early Cretaceous, showing the distribution of the Permian brachiopod faunas in the South Kitakami Terrane. Solid black arrow shows the direction of strike-slip motion. MTL: Median Tectonic Line, TTL: Tanakura Tectonic Line, 1: South Kitakami Terrane, 2: Akiyoshi Terrane, 3: Mino Terrane, 4: Shimanto Terrane, 5: Hida Nappe (made from Tazawa, 2007).
Systematic descriptions
Order Productida Sarytcheva and Sokolskaya, 1959
Suborder Chonetidina Muir-Wood, 1955
Superfamily Chonetoidea Bronn, 1862
Family Rugosochonetidae Muir-Wood, 1962
Subfamily Rugosochonetinae Muir-Wood, 1962
Genus Neochonetes Muir-Wood, 1962
Subgenus Neochonetes (Zhongyingia) Shen and Archbold, 2002
Type species.—Neochonetes zhongyingensis Liao, 1980.
Neochonetes (Zhongyingia) zhongyingensis Liao, 1980 Figures 6.1a–6.2b
Figure 6.
1a–2b. Neochonetes (Zhongyingia) zhongyingensis Liao, 1a, 1b, 1c: external mould and latex cast of a ventral valve, NU-B1007, (1b, 1c ×2), 2a, 2b: internal mould of a dorsal valve, NU-B1021, (2b ×2), 3a–4b. Kitakamichonetes multicapillatus Afanasjeva and Tazawa, 3a, 3b, 3c, 3d: external mould, external latex cast, internal mould and internal latex cast of a ventral valve, NU-B1031, 4a, 4b: external mould and latex cast of a ventral valve, NU-B1033, 5a, 5b. Capillomesolobus sp., internal mould of a ventral valve, NU-B1030, (5b ×2), 6a–7b. Transennatia gratiosa (Waagen), 6a, 6b, 6c, 6d, 6e: ventral, posterior, anterior and lateral views of internal mould of a ventral valve, NU-B767, (6a–6e ×2), 7a, 7b: internal mould of a ventral valve, NU-B769, (7b ×2), 8a–12b. Waagenoconcha permocarbonica Ustritsky, 8a, 8b, 8c: ventral external latex cast, ventral internal mould and dorsal internal mould of a composite valve, NU-B866, 9: internal latex cast of a dorsal valve, NU-B869, 10a, 10b: ventral and dorsal views of internal mould of a composite valve, NU-B870, 11: external mould of a dorsal valve, NU-B880, 12a, 12b: internal mould and latex cast of a dorsal valve, NU-B892. (Natural size unless otherwise indicated).
Neochonetes zhongyingensis Liao, 1980, p. 257, pl. 5, figs. 10–13.
Neochonetes (Zhongyingia) zhongyingensis Liao. Shen and Archbold, 2002, p. 333, figs. 4A–4Q.
Material.—Twenty-five specimens from locality MZ-S2: (1) external moulds of five ventral valves, NU-B1005–1009; (2) internal moulds of nine ventral valves, NU-B1010–1018; (3) external and internal moulds of two dorsal valves, NU-B1019, 1020; (4) internal moulds of nine dorsal valves, NU-B1021–1029.
Description.—Shell medium size for genus, transversely trapezoidal in outline; widest at hinge; cardinal extremities extended; length 11 mm, width 17 mm in the largest specimen (NU-B1007). Ventral valve moderately convex in lateral profile; umbo small; ears large, acute; sulcus broad and shallow, beginning from anterior to umbo, rapidly widening anteriorly. Dorsal valve gently concave in lateral profile; ears large, flat; fold low and broad. External surface of both valves ornamented by numerous weak capillae and irregular growth lines; 4–5 capillae in 1 mm at anterior margin of ventral valve. Internal structures are obscure.
Remarks.—These specimens are referred to Neochonetes (Zhongyingia) zhongyingensis Liao, 1980, originally described from the Longtan and Changhsingian beds of Guizhou, South China, on account of size, shape and external ornament of both valves, although the Mizukoshi specimens have weaker capillae than the Chinese material (see Shen and Archbold, 2002, figs. 4D, 4E, 4K, 4L. 4O).
Neochonetes (Zhongyingia) linshuiensis Campi and Shi (2005, p. 282, figs. 4B–4F, 4H, 4P–4R), from the Changhsingian of Sichuan, South China, differs from N. (Z.) zhongyingensis in its smaller size and in having coarser capillae on the ventral valve.
Distribution.—Upper Permian (Wuchiapingian) of South China (Hunan); Upper Permian (Lopingian) of South China (Guizhou) and southwest Japan (Mizukoshi).
Subfamily Chalimochonetinae Afanasjeva, 1988
Genus Kitakamichonetes Afanasjeva and Tazawa, 2007
Type species.—Kitakamichonetes multicapillatus Afanasjeva and Tazawa, 2007.
Kitakamichonetes multicapillatus Afanasjeva and Tazawa, 2007 Figures 6.3a–6.4b
Kitakamichonetes multicapillatus Afanasjeva and Tazawa, 2007, p. 73, pl. 11, figs. 1–12.
Material.—Six specimens from locality MZ-S2: (1) external and internal moulds of a ventral valve, NU-B1031; (2) external moulds of three ventral valves, NU-B1032–1034; (3) external moulds of two dorsal valves, NU-B1035, 1036.
Description.—Shell medium size for genus, transversely trapezoidal to semicircular in outline; cardinal extremities acute; widest at hinge; length 18 mm, width 41 mm in the best preserved specimen (NU-B1031). Ventral valve gently convex in lateral profile; umbo small; ears large, triangular in shape and pointed; sulcus wide and shallow, arising at umbo and fairly broad near front margin. Dorsal valve slightly concave in lateral profile; fold wide and low, very weakly developed. External surface of both valves ornamented with numerous capillae and very weak, irregular concentric rugae; capillae numbering 4–5 in 1 mm near anterior margin of ventral valve. Ventral interior with long median septum, a pair of teeth and large muscle field. Other internal structures are obscure.
Remarks.—The Mizukoshi specimens are referred to Kitakamichonetes multicapillatus Afanasjeva and Tazawa, 2007, described from the Middle Permian Kanokura Formation of the South Kitakami Belt, northeast Japan in size, shape and surface ornamentation of the shells, especially in their enormously large size.
Comparison with other chonetid species has been fully discussed by Afanasjeva and Tazawa (2007, p. 73).
Distribution.—Middle Permian (Wordian-Capitanian) of northeast Japan (South Kitakami Belt); Upper Permian (Lopingian) of southwest Japan (Mizukoshi).
Subfamily Capillomesolobinae Pečar, 1986
Genus Capillomesolobus Pečar, 1986
Type species.—Capillomesolobus karavankensis Pečar, 1986.
Capillomesolobus sp. Figures 6.5a, 6.5b
Material.—One specimen from locality MZ-S2, external and internal moulds of a ventral valve, NU-B1030.
Remarks.—The single specimen from Mizukoshi is safely assigned to the genus Capillomesolobus by its small, wider subrectangular ventral valve (length 8 mm, width 9 mm), ornamented by numerous capillae (4–5 per 1 mm at the anterior margin of the valve), and by having a sulcus with a median lobe. This specimen most resembles Mesolobus sp. Tazawa (1979, p. 25, pl. 4, figs. 2a, 2b) from the Kanokura Formation of Matsukawa in the Kesennuma area, South Kitakami Belt and Capillomesolobus sp. Tazawa (2001b, p. 289, figs. 6.8a–6.10) from the Moribu Formation of the Moribu area, Hida Gaien Belt, in size, outline and external ornament of the ventral valve.
The shells described or figured from the Lower and Middle Permian of the South Kitakami Belt, northeast Japan as Chonetes sinuosa Schellwien, 1892 by Hayasaka (1925, p. 93, pl. 5, figs. 5, 6), Mesolobus mesolobus (Norwood and Pratten, 1855) by Nakamura (1959, p. 205, pl. 2, figs. 2, 3) and Mesolobus sinuosa (Schellwien, 1892) by Tazawa (1976, pl. 2, fig. 12) are clearly distinguished from the Mizukoshi species in their much larger dimensions.
Suborder Productidina Waagen, 1883
Superfamily Productoidea Gray, 1840
Family Productellidae Schuchert, 1929
Subfamily Marginiferinae Stehli, 1954
Tribe Paucispiniferini Muir-Wood and Cooper, 1960
Genus Transennatia Waterhouse, 1975
Type species.—Productus gratiosus Waagen, 1884.
Transennatia gratiosa (Waagen, 1884) Figures 6.6a–6.7b
Productus gratiosus Waagen, 1884, p. 691, pl. 72, figs. 3–7; Diener, 1897, p. 23, pl. 3, figs. 3–7; Mansuy, 1913, p. 115, pl. 13, figs. 1a, 1b; Colani, 1919, p. 10, pl. 1, figs. 2a–2c; Chao, 1927, p. 44, pl. 4, figs. 6–10; Chi-Thuan, 1962, p. 491, pl. 2, figs. 5–7.
Productus (Dictyoclostus) gratiosus Waagen. Huang, 1933, p. 88, pl. 11, figs. 14a, 14b; Hayasaka, 1960, p. 49, pl. 1, fig. 8.
Marginifera gratiosa (Waagen). Reed, 1944, p. 98, pl. 19, figs. 6–7.
Dictyoclostus gratiosus (Waagen). Zhang and Ching (Jin), 1961, p. 411, pl. 4, figs. 12–18; Wang et al., 1964, p. 291, pl. 45, figs. 14–19; Leman, 1994, pl. 1, figs. 11–13.
Gratiosina gratiosa (Waagen). Grant, 1976, pl. 33, figs. 19–26; Licharew and Kotlyar, 1978, pl. 12, figs. 5, 6; pl. 20, fig. 1.
Asioproductus gratiosus (Waagen). Yang et al., 1977, p. 350, pl. 140, figs. 5a–5c; Feng and Jiang, 1978, p. 254, pl. 90, figs. 1, 2; Tong, 1978, p. 228, pl. 80, figs. 7a, 7b; Lee et al., 1980, p. 373, pl. 164, figs. 14a–14c; pl. 166, figs. 5–6.
Asioproductus bellus Chan (Zhan), 1979, p. 85, pl. 6, figs. 7–13; pl. 9, figs. 8–10; text-fig. 18.
Transennatia gratiosus (Waagen). Wang et al., 1982, p. 214, pl. 92, figs. 6–8; pl. 102, figs. 4–9; Liu et al., 1982, p. 185, pl. 132, figs. 9a–9d; Ding and Qi, 1983, p. 280, pl. 95, figs. 14a, 14b.
Transennatia gratiosa (Waagen). Yang, 1984, p. 219, pl. 33, figs. 7a–7c; Jin, 1985, pl. 4, figs. 33, 34, 45, 46; Tazawa and Matsumoto, 1998, p. 6, pl. 1, figs. 4–8; Tazawa et al., 2000, p. 7, pl. 1, figs. 3–5; Tazawa and Ibaraki, 2001, p. 7, pl. 1, figs. 1–3; Tazawa, 2001b, p. 289, figs. 6.1–6.7; Shen et al., 2002, p. 676, figs 4.27–4.31.
Material.—Five specimens from locality MZ-S2: (1) external and internal moulds of a ventral valve, NU-B767; (2) internal moulds of two ventral valves, NU-B768, 769; (3) external moulds of two dorsal valves, NU-B770, 771.
Description.—Shell small for genus, transversely subquadrate in outline, widest at hinge; length 13 mm, width 20 mm in the largest specimen (NU-B768). Ventral valve strongly and unevenly convex in lateral profile, most convex at umbonal region, strongly geniculated at anterior margin of visceral disc, with long trail; umbo small, slightly incurved; ears small, pointed; sulcus narrow and low; lateral slopes steep. Dorsal valve almost flat on visceral disc, geniculated at anterior margin of visceral disc, followed by short trail; fold narrow and low. External surface of ventral valve reticulate on visceral disc and costate on trail; costae converging into sulcus anteriorly, having a density of 7–8 per 5 mm at midvalve; spines or spine bases not observed. External ornament of dorsal valve similar to that of the opposite valve. Interior of both valves not well preserved and obscure.
Remarks.—These specimens are referred to Transennatia gratiosa (Waagen, 1884), on the basis of their small size, strongly convex ventral valve and reticulate ornament on the disks of both valves. The Mizukoshi specimens are smaller than the Salt Range specimens, and most resemble the smaller shells of T. gratiosa from the Middle Permian (Wordian) of the Ise and Moribu areas, Hida Gaien Belt, central Japan (Tazawa and Matsumoto, 1998; Tazawa, 2001b) and the Kesennuma and Setamai areas, South Kitakami Belt, northeast Japan (Hayasaka, 1960; Tazawa and Ibaraki, 2001).
Transennatia insculpta (Grant, 1976, p. 135, pl. 32, figs. 1–37; pl. 33, figs. 1–16) from the Rat Buri Limestone of Ko Muk, southern Thailand is close to T. gratiosa in general appearance, but it has a wider shell and more prominent ears.
Distribution.—Middle Permian (Wordian-Capitanian) of Nepal (Kumaon Himalayas), Cambodia (Sisophon), Vietnam (Quang Tri), South China (Guangxi, Hubei and Shaanxi), Northeast China (Jilin and Heilongjiang), eastern Russia (South Primorye) and Japan (Hida Gaien and South Kitakami Belts); Middle Permian (Wordian) to Upper Permian (Wuchiapingian) of Pakistan (Salt Range); Upper Permian (Wuchiapingian) of South China (Yunnan, Sichuan, Guizhou, Guangdong, Hunan, Hubei, Jiangxi, Zhejiang and Anhui); Upper Permian (Lopingian) of southwest Japan (Mizukoshi).
Superfamily Echinoconchoidea Stehli, 1954
Family Echinoconchidae Stehli, 1954
Subfamily Juresaniinae Muir-Wood and Cooper, 1960
Tribe Waagenoconchini Muir-Wood and Cooper, 1960
Genus Waagenoconcha Chao, 1927
Type species.—Productus humboldti d’Orbigny, 1842.
Waagenoconcha krystofovichi (Fredericks, 1925) Figures 7.17a–7.18c
Figure 7.
1a–5. Anidanthus ussuricus (Fredericks), 1a, 1b: ventral and dorsal views of internal mould of a conjoined valve, NU-B732, 2a, 2b, 2c: posterior, anterior and lateral views of internal mould of a conjoined valve, NU-B735, 3: internal mould of a dorsal valve, NU-B738, 4: external mould of a dorsal valve, NU-B737, 5: external mould of a dorsal valve, NU-B736, 6a–8e. Anidanthus mizukoshiensis sp. nov., 6a, 6b: external mould of a dorsal valve, NU-B776, (6b ×2), 7a, 7b: external mould of a dorsal valve, NU-B777, (7b ×2), 8a, 8b, 8c, 8d, 8e: ventral and dorsal views of internal mould of a conjoined valve and external mould of a dorsal valve, NU-B775 (holotype), (8b, 8c, 8e ×2), 9a–13. Terrakea yanagidai sp. nov., 9a, 9b, 9c, 9d: ventral, posterior, anterior and lateral views of internal mould of a ventral valve, NU-B778 (holotype), 10a, 10b, 10c, 10d: ventral, posterior, anterior and lateral views of internal mould of a ventral valve, NU-B787, 11: external latex cast of a ventral valve, NU-B781, 12: external latex cast of a ventral valve, NU-B779, 13: external mould of a dorsal valve, NU-B852, 14. Yakovlevia kaluzinensis Fredericks, internal mould of a ventral valve, NU-B774, 15a–16. Urushtenoidea crenulata (Ting), 15a, 15b: external cast of a ventral valve, NU-B773, (15b ×2), 16: internal mould of a ventral valve, NU-B772, 17a–18c. Waagenoconcha krystofovichi (Fredericks), 17a, 17b: internal mould and external latex cast of a ventral valve, NU-B896, 18a, 18b, 18c: ventral, anterior and lateral views of internal mould of a ventral valve, NU-B898. (Natural size unless otherwise indicated).
Productus krystofovichi Fredericks, 1925, p. 20, pl. 2, figs. 71–75.
Productus humboldti mut. purdoni Davidson. Fredericks, 1925 p. 19, pl. 2, figs. 76–78.
Waagenoconcha krystofovichi (Fredericks). Licharew and Kotlyar, 1978, pl. 17, figs. 5, 6.
Material.—Seven specimens from locality MZ-S2: (1) external and internal moulds of two ventral valves, NU-B896, 897; (2) internal moulds of five ventral valves, NU-B898–902.
Description.—Shell small for genus, elongate subrectangular in outline, with greatest width slightly anterior to midvalve; length about 43 mm, width 33 mm in the largest specimen (NU-B898). Ventral valve strongly convex in lateral profile; umbo large, incurved; hinge nearly straight, slightly shorter than greatest width of valve; ears small, triangular; sulcus narrow and deep; lateral slopes steep. External surface of ventral valve ornamented with numerous, elongate, quincuncially arranged spine bases on venter, and smaller, rounded spine bases on umbonal slopes; several faint radial folds on lateral slopes. Ventral interior with small, elongate, faintly dendritic adductor scars and large, striated diductor scars on posterior one third of valve.
Remarks.—These specimens are referred to Waagenoconcha krystofovichi (Fredericks, 1925) from the Chandalaz Formation of Cape Kalouzin in the Vladivostok area, South Primorye, eastern Russia, on account of size, shape and external ornament of the ventral valve, especially in having radial folds on ventral lateral slopes.
Waagenoconcha purdoni (Davidson, 1862) from the Chhidru Formation of the Salt Range is similar in general shape and external ornament of the ventral valve, but it has a much larger and less convex ventral valve (see Waagen, 1884, pl. 73, figs. 1–3).
Distribution.—Middle Permian (Capitanian) of South Primorye, eastern Russia; Upper Permian (Lopingian) of Mizukoshi, southwest Japan.
Waagenoconcha permocarbonica Ustritsky in Ustritsky and Tschernjak, 1963 Figures 6.8a–6.12b
Waagenoconcha permocarbonica Ustritsky in Ustritsky and Tschernjak, 1963, p. 79, pl. 7, fig. 6; pl. 8, figs. 1–3; Lee et al., 1980, p. 364, pl. 168, figs. 1, 6; pl. 169, figs. 3, 4; Duan and Li, 1985, p. 107, pl. 37, figs. 3–5; Shi and Waterhouse, 1996, p. 77, pl. 9, figs. 4–15; pl. 10, figs. 1–4; Tazawa, 2001b, p. 292, figs. 7.20–7.23.
Material.—Thirty specimens from locality MZ-S2: (1) external mould of a conjoined valve, NU-B865; (2) external moulds of two ventral valves and associated internal mould of the conjoined valve, NU-B866, 867; (3) internal moulds of three conjoined valves, NU-B868-870; (4) external mouds of two ventral valves, NU-B871, 872; (5) internal moulds of four ventral valves, NU-B873-876; (6) external and internal moulds of two dorsal valves, NU-B877, 878; (7) external moulds of twelve dorsal valves, NU-B879-890; (8) internal moulds of four dorsal valves, NU-B891-894.
Description.—Shell large for genus, transversely subrectangular in outline, with greatest width slightly anterior to midvalve; length 33 mm, width about 54 mm in the largest specimen (NU-B874). Ventral valve strongly convex in both lateral and anterior profiles; umbo small, incurved; hinge slightly shorter than widest part at about midvalve; ears inconspicuous; cardinal extremities rounded; lateral slopes steep; sulcus moderately developed, commencing at about 10 mm from umbo, deepest at midvalve, and becoming shallower and wider toward anterior margin. Dorsal valve with flattened to slightly inflated and rounded visceral disc, strongly geniculated at anterolateral margins, and followed by short trail. External surface of ventral valve ornamented by irregular concentric rugae and numerous, quincuncially arranged spine bases; spine bases becoming fine at anterolateral parts; numbering 6–7 in 5 mm at midvalve, 14–16 in 5 mm near anterior margin. External ornament of dorsal valve similar to that of opposite valve. Ventral interior with small, elongate, posteriorly smooth and anteriorly dendritic adductor scars and large, flabellate, striated diductor scars. Dorsal interior with trilobed cardinal process followed by thick, long median septum, extending to about midvalve; adductor scars elongate oval in shape and dendritic.
Remarks.—These specimens are referred to Waagenoconcha permocarbonica Ustritsky, 1963, originally described by Ustritsky (in Ustritsky and Tschernjak, 1963) from the Bashkirian to the Sakmarian of Taimyr, on account of size, shape and external ornament of both valves.
Waagenoconcha waageni (Rothpletz, 1892) from the Middle Permian of Timor is close in general outline, but it has more numerous and stronger concentric rugae and coarser spine bases on the ventral valve (see Archbold and Bird, 1989, figs. 3C, 3D).
Waagenoconcha imperfecta Prendergast (1935, p. 15, pl. 4, figs. 1–3), from the Upper Permian (Wuchiapingian) of the Canning Basin, western Australia, differs from the present species in having very fine and closely arranged spine bases on both valves.
Waagenoconcha abichi (Waagen, 1884, p. 697, pl. 74, figs. 1–7) from the Middle Permian (Capitanian) Wargal Formation and the Upper Permian (Wuchiapingian-Changhsingian) Chhidru Formation of the Salt Range, is clearly distinguished from the present species by its smaller size and much coarser spine bases on the ventral valve.
Distribution.—Middle Carboniferous (Bashkirian) to Lower Permian (Sakmarian) of northern Russia (Taimyr); Lower Permian (Sakmarian) of western Canada (Yukon Territory); Middle Permian (Roadian to Wordian) of North China (Inner Mongolia) and central Japan (Hida Gaien Belt); Upper Permian (Lopingian) of southwest Japan (Mizukoshi).
Superfamily Linoproductoidea Stehli, 1954
Family Linoproductidae Stehli, 1954
Subfamily Anidanthinae Waterhouse, 1968b
Genus Anidanthus Hill, 1950
Type species.—Linoproductus springsurensis Booker, 1932.
Anidanthus ussuricus (Fredericks, 1924) Figures 7.1a–7.5
Productus ussuricus Fredericks, 1924, p. 8, pl. 1, figs. 1–5; Fredericks, 1925, p. 18.
Linoproductus cf. lineatus (Waagen): Yanagida, 1963, p. 74, pl. 10, figs. 8–14.
Anidanthus abukumaensis Yanagisawa, 1967, p. 89, pl. 2, fig. 16.
Anidanthus ussuricus (Fredericks): Nakamura, 1972b, p. 434, pl. 1, figs. 1a–1c; Grigorjeva and Kotlyar, 1977, p. 56, pl. 5, figs. 1–3; text-fig. 34; Licharew and Kotlyar, 1978, pl. 13, figs. 5a–5g; Lee et al., 1980, p. 379, pl. 170, figs. 5, 9; Duan and Li, 1985, p. 113, pl. 38, figs. 6–9; Gu, 1992, p. 236, pl. 69, figs. 18, 25; pl. 74, figs. 7, 8; pl. 78, figs. 11, 12; Tazawa and Hasegawa, 2007, p. 6, figs. 4.1–4.7.
Pseudomarginifera ussuricus (Fredericks): Wang and Zhang, 2003, p. 106, pl. 17, figs. 16–27.
Material.—Seven specimens from locality MZ-S1: (1) internal moulds of two conjoined valves, NU-B732, 733; (2) internal mould of two ventral valves, NU-B734, 735; (3) external moulds of three dorsal valves, NU-B736–738.
Description.—Shell large for genus, transversely subquadrate in outline; hinge straight, equal to greatest width; length 9 mm, width about 34 mm in the largest ventral valve specimen (NU-B733); length 18 mm, width about 35 mm in the largest dorsal valve specimen (NU-B736). Ventral valve highly convex in both lateral and anterior profiles, with long trail; umbo tapering, pointed and strongly incurved beyond hinge; ears small; sulcus broad and shallow; flanks steep. Dorsal valve slightly concave on venter, strongly geniculated and followed by long trail; ears large, prominent and almost flattened; fold broad and low. External ornament of ventral valve obscure, but numerous capillae faintly observed. Dorsal valve ornamented by strong concentric lamellae and numerous capillae over visceral disc; lamellae only on ears; numbering 4 lamellae in 5 mm, and 7–8 capillae in 5 mm at about midvalve.
Remarks.—These specimens are poorly preserved and severely deformed but can be safely referred to Anidanthus ussuricus (Fredericks, 1924), originally described from the Chandalaz Formation of the Vladivostok area, South Primorye, Far East Russia by their large size and extremely developed long trail on both valves. The linoproductid shells, described and figured by Yanagida (1963, p. 74, pl. 10, figs. 8–14) as Linoproductus cf. lineatus (Waagen, 1884) from the same locality MZ-S1 of Mizukoshi, are probably conspecific with the present species by their strongly convex ventral valves with long trails. Stepanov (1935, p. 56) established the genus Pseudomarginifera with the present species, Productus ussuricus Fredericks, 1924, as type species. However, I tentatively treat Pseudomarginifera as a junior synonym of Anidanthus, owing to the poor state of preservation of both Frederick’s and the Mizukoshi specimens.
The type species, Anidanthus springsurensis (Booker, 1932) from the Cattle Creek Formation of Queensland, eastern Australia, differs from A. ussuricus in its much smaller size.
Distribution.—Middle Permian (Wordian-Capitanian) of North China (Zhesi and Xiujimqinqi, Inner Mongolia), Northeast China (Jilin) and eastern Russia (Vladivostok and Nakhodka, South Primorye); Upper Permian (Lopingian) of northeast Japan (Takakurayama in the Abukuma Mountains) and southwest Japan (Mizukoshi).
Anidanthus mizukoshiensis sp. nov. Figures 7.6a–7.8e
Etymology.—Named after the fossil locality, Mizukoshi.
Material.—Three specimens from locality MZ-S2: (1) external mould of a dorsal valve and associated internal mould of conjoined valve, NU-B775 (holotype); (2) external and internal moulds of a dorsal valve, NU-B776; (3) external mould of a dorsal valve, NU-B777.
Diagnosis.—Small, transverse Anidanthus, with fine, numerous costellae on dorsal valve, numbering 11–12 in 5 mm at about midvalve.
Description.—Shell small size for genus, transversely subrectangular in outline, with greatest width along hinge; length about 15 mm, width about 22 mm in the holotype (NU-B775). Ventral valve strongly and unevenly convex in lateral profile, most convex at umbonal region, slightly convex at venter, geniculated near anterior margin of visceral disc, and followed by short trail; umbo small, strongly incurved; sulcus broad and shallow, originating near umbo and extending to anterior margin. Dorsal valve slightly concave, without fold; ears large, prominent and flattened. External surface of dorsal valve ornamented by strong concentric rugae and numerous, fine costellae on visceral disc, rugae only on ears; numbering 6–7 rugae on visceral disc; costellae with a density of 11–12 per 5 mm at about midvalve. Internal structures not clearly observed in the present material.
Remarks.—Anidanthus mizukoshiensis n. sp. is distinguished from the type species Anidanthus springsurensis (Booker, 1932) by its smaller and more transverse shell, and having much finer costellae on the dorsal valve.
Anidanthus aagardi (Toula, 1875, p. 235, pl. 7, figs. 2a–2c) from the Middle to Upper Permian (?) of Spitsbergen differs from A. mizukoshiensis in having a less transverse shell.
The preceding described species, Anidanthus ussuricus (Fredericks, 1924), differs from the present species in its much larger size and extremely long trail.
Subfamily Grandaurispininae Lazarev, 1986
Genus Terrakea Booker, 1930
Type species.—Productus brachythaerus Morris, 1845.
Terrakea yanagidai sp. nov. Figures 7.9a–7.13
Terrakea sp. B Tazawa, 2008a, p. 63, figs. 3A–3P.
Etymology.—Named for Prof. Juichi Yanagida.
Material.—Eighty-one specimens from locality MZ-S2: (1) external and internal moulds of a ventral valve, NU-B778 (holotype); (2) external moulds of three ventral valves, NU-B779-781; (3) internal mould of a ventral valve with external mould of the opposite dorsal valve, NU-B782; (4) internal moulds of sixty-seven ventral valves, NU-B783-849; (5) external and internal moulds of a dorsal valve, NU-B850; (6) external moulds of eight dorsal valves, NU-B851-858.
Diagnosis.—Small, transverse Terrakea, having highly arched ventral valve with long trail and flattened dorsal valve, strongly geniculated and followed by short trail.
Description.—Shell small for genus, transversely subrectangular in outline, with greatest width at hinge; length 12 mm, width 28 mm in the holotype (NU-B778); length 15 mm, width about 31 mm in the largest specimen (NU-B784). Ventral valve strongly convex, geniculated and followed by long trail; umbo large, tapering and incurved; venter slightly convex with shallow sulcus; flanks steep; ears small, triangular and clearly demarcated from visceral portion. Dorsal valve flat on visceral disc, strongly and sharply geniculated and followed by short trail. External surface of ventral valve ornamented by costellae and spine bases; costellae fine, numerous, numbering 11–12 in 5 mm at about midvalve; spine bases elongate, quincuncially arranged on venter and trail; erect spines numerous over ears. External surface of dorsal valve ornamented by numerous fine costellae, regular, rather weak rugae, and numerous quincuncially arranged spines. Internally, ventral valve with finely dendritic adductor scars and longitudinally striated diductor scars. Other internal structures are obscure.
Remarks.—The Mizukoshi specimens were first described by Tazawa (2008a) as Terrakea sp. B. This species is distinguished from the type species, T. brachythaera (Morris, 1845) by its much smaller size and fine costellae on the ventral valve.
Terrakea japonica Tazawa (2008b, figs. 3A–3L), from the lower Kanokura Formation (Wordian) of Imo, South Kitakami Belt, northeast Japan, is similar to T. yanagidai, but it differs from the latter in its larger size and stronger costellae on both valves.
Terrakea pollex Hill (1950, p. 20, pl. 9, figs. 6–12) from the Fairyland Member of the Buffel Formation in Cracow Homestead, Queensland, eastern Australia, differs from T. yanagidai in having a shell with a shorter hinge and a rounded oval-shaped dorsal valve with a long trail.
Terrakea borealis Ganelin (in Sarytcheva, 1977, p. 142, pl. 21, figs. 4–8; text-fig. 81) from the Omolonsky Horizon of the Kolyma-Omolon region, northeastern Russia, differs from the present new species in having ears with fewer spines.
Family Yakovleviidae Waterhouse, 1975
Genus Yakovlevia Fredericks, 1925
Type species.—Chonetes (Yakovlevia) kaluzinensis Fredericks, 1925.
Yakovlevia kaluzinensis Fredericks, 1925 Figure 7.14
Chonetes (Yakovlevia) kaluzinensis Fredericks, 1925, p. 7, pl. 2, figs. 64–66.
Yakovlevia kaluzinensis Fredericks. Kotlyar, 1961, text-figs. 1–3; Licharew and Kotlyar, 1978, pl. 14, figs. 1, 2; Manankov, 1998, pl. 8, figs. 18, 19; Tazawa, 1999, p. 90, figs. 3.7–3.15; Tazawa, 2001b, p. 291, figs. 6.20–6.25.
Yakovlevia sp. Horikoshi et al., 1987, figs. 3A, 3B.
Material.—One specimen from locality MZ-S2, internal mould of a ventral valve, NU-B774.
Remarks.—The Mizukoshi specimen is large in size (length about 43 mm, width about 46 mm), transversely subquadrate in outline, and having a pair of small, elongate subtrigonal adductor scars and two large diductor scars which are striated anteriorly and demarcated by a strong ridge posterolaterally. This specimen is referred to Yakovlevia kaluzinensis Fredericks, 1925, originally described by Fredericks (1925) from the Chandalaz Formation of the Vladivostok area, South Primorye in size, shape and internal structure of the ventral valve. It most resembles the specimens of Y. kaluzinensis, described by Tazawa (2001b, p. 291, figs. 6.20–6.25) from the Moribu Formation of Moribu, Hida Gaien Belt, central Japan.
Distribution.—Middle Permian (Kungurian-Capitanian) of southeastern Mongolia (near Mt. Dzhirem-Ula), eastern Russia (South Primorye) and central Japan (Hida Gaien Belt); Upper Permian (Lopingian) of Mizukoshi, southwest Japan.
Suborder Strophalosiidina Schuchert, 1913
Superfamily Aulostegoidea Muir-Wood and Cooper, 1960
Family Aulostegidae Muir-Wood and Cooper, 1960
Subfamily Chonosteginae Muir-Wood and Cooper, 1960
Genus Urushtenoidea Jin and Hu, 1978
Type species.—Urushtenia chaoi Jin, 1963.
Urushtenoidea crenulata (Ting in Yang et al., 1962) Figures 7.15a–7.16
Eomarginifera crenulata Ting in Yang et al., 1962, p. 85, pl. 37, figs. 6 right–8.
Urushtenia costata Ting in Yang et al., 1962, p. 87, pl. 25, figs. 5–7; pl. 37, figs. 6 left.
Urushtenia chenanensis Chan in Chan (Zhan) and Lee, 1962, p. 478, 488, pl. 3, figs. 4–6.
Urushtenia crenulata (Ting). Ching (Jin), 1963, p. 20, pl. 1, figs. 17–24; pl. 2, figs. 9, 10, 18–20; text-fig. 5; Yang et al., 1977, p. 335, pl. 136, figs. 11a–11c; Feng and Jiang, 1978, p. 246, pl. 89, figs. 11a, 11b; Tong, 1978, p. 218, pl. 78, figs. 17a–17c; Yang and Gao, 1996, pl. 34, figs. 7, 8.
Urushutenia chenanensis Chan. Tong, 1978, p. 218, pl. 78, figs. 16a–16c.
Urushtenoidea chenanensis (Chan). Jin and Hu, 1978, p. 117, pl. 2, fig. 9; Hu, 1983, pl. 3, figs. 4, 5.
Urushtenoidea crenulata (Ting). Nakamura, 1979, p. 228, pl. 1, figs. 5–9; pl. 3, figs. 1, 2; Yang, 1984, p. 213, pl. 31, figs. 19a–19c; Tazawa, 2001b, p. 296, figs. 7.1–7.9.
Urushtenoidea maceus (Ching). Nakamura, 1979, p. 227, pl. 1, figs. 1–4; pl. 2, figs. 1–3.
Uncisteges crenulata (Ting). Liu et al., 1982, p. 178, pl. 129, figs. 1a–1d; Jin, 1985, pl. 6, fig. 41; Zhu, 1990, p. 74, pl. 14, figs. 4–14; pl. 17, figs. 12, 12a.
Material.—Two specimens from locality MZ-S2: (1) external and internal moulds of a ventral valve, NU-B772; (2) external cast of a ventral valve, NU-B773.
Description.—Shell medium size for genus, transversely subquadrate in outline; length about 15 mm, width about 18 mm in the larger specimen (NU-B773). Ventral valve slightly convex in venter, strongly geniculated at right angle, and followed by long trail. External ornament of ventral valve consisting of few weak concentric rugae and costae on visceral disc, numerous strong costae on trail, numbering 6 in 5 mm at middle of trail. Internal structure of ventral valve obscure in the present specimen.
Remarks.—The single ventral valve specimen from Mizukoshi can be referred to Urushtenoidea crenulata (Ting in Yang et al., 1962) in size, shape and external ornament of the ventral valve. This specimen most resembles the ventral valve specimen (NU-B409; Tazawa, 2001b, fig. 7.2) of U. crenulata, described from the lower Moribu Formation of Moribu, Hida Gaien Belt, central Japan.
Distribution.—Middle Permian (Kungurian-Capitanian) of Cambodia (Sisophon), South China (Guizhou, Sichuan, Hunan, Guangdong, Jiangxi, Fujian, Jiangsu, Hubei and Shaanxi), Northwest China (Qinghai and Gansu), and Japan (South Kitakami and Hida Gaien Belts); Upper Permian (Lopingian) of Mizukoshi, southwest Japan.
Suborder Lyttoniidina Williams, Harper and Grant, 2000
Superfamily Permianelloidea He and Zhu, 1979
Family Permianellidae He and Zhu, 1979
Genus Permianella He and Zhu, 1979
Type species.—Permianella typica He and Zhu, 1979.
Permianella typica He and Zhu, 1979 Figure 8.1
Figure 8.
1. Permianella typica He and Zhu, internal mould of a dorsal valve, NU-B895, 2a–6b. Hustedia ratburiensis Waterhouse and Piyasin, 2a, 2b, 2c: ventral and dorsal views of internal mould of a conjoined valve, NU-B1037, (2b, 2c ×2), 3: internal mould of a ventral valve, NU-B1045 (×2), 4: internal mould of a ventral valve, NU-B1046 (×2), 5: external latex cast of a dorsal valve, NU-B1047 (×2), 6a, 6b: external latex cast and external mould of a ventral valve, NU-B1040 (×2), 7a–8b. Acosarina cf. circular Xu, 7a, 7b: internal mould of a ventral valve, NU-B861, (7b ×2), 8a, 8b: internal mould of a ventral valve, NU-B863, (8b ×2), 9a, 9b. Orthotichia sp., internal mould of a ventral valve, NU-B864, (9b ×2), 10a–10c. Rhynchopora matsumotoi sp. nov., 10a, 10b, 10c: ventral view of internal mould of a conjoined valve and external latex cast of a dorsal valve, NU-B1052 (holotype), (10b, 10c ×2), 11a, 11b. Rhynchopora sp., internal mould of a ventral valve, NU-B1053, (11b ×2), 12–16c. Derbyia nipponica Nakamura, 12: internal mould of a ventral valve, NU-B905, 13a, 13b, 13c: external mould, external latex cast and internal mould of a ventral valve, NU-B906, 14a, 14b, 14c: external mould, external latex cast and internal mould of a dorsal valve, NU-B911, 15: internal mould of a dorsal valve, NU-B912, 16a, 16b, 16c: external mould, external latex cast and internal mould of a ventral valve, NU-B904. (Natural size unless otherwise indicated).
Permianella typica He and Zhu, 1979, p. 132, 137, pl. 1, figs. 1a, b; pl. 2, figs. 1–3; pl. 3, figs. 1–3; Wang and Jin, 1991, p. 496, pl. 2, figs. 1–3; Shen and Tazawa, 1997, p. 288, figs. 2–4, 5.1–5.14; Campi et al., 2000, p. 41, figs. 4A, 4C; 5A, 5B.
Material.—One specimen from locality MZ-S2, internal mould of a dorsal valve, NU-B895.
Remarks.—The material available is lacking the posterior half of the dorsal valve, but it resembles well the specimens of Permianella typica He and Zhu, 1979, described by Shen and Tazawa (1997, p. 288, figs. 2–5), from the lower Kanokura Formation of the southern Kitakami Mountains (South Kitakami Belt), northeast Japan. It is characterized by its large size (length over 25 mm, width 17 mm) and by having a deep anterior incision.
Distribution.—Middle Permian (Wordian-Capitanian) of northeast Japan (South Kitakami Belt) and Malaysia (Pahang); Upper Permian (Wuchiapingian) of South China (Zhejiang, Jiangxi and Sichuan); Upper Permian (Lopingian) of southwest Japan (Mizukoshi).
Order Orthotetida Waagen, 1884
Suborder Orthotetidina Waagen, 1884
Superfamily Orthotetoidea Waagen, 1884
Family Derbyiidae Stehli, 1954
Genus Derbyia Waagen, 1884
Type species.—Derbyia regularis Waagen, 1884.
Derbyia nipponica Nakamura, 1972a Figures 8.12–8.16c
Derbyia magnifica Licharew, 1932. Hayasaka and Minato, 1956, p. 141, pl. 23, figs. 1a–1c; Hayasaka, 1960, p. 45, pl. 2, figs. 5, 6.
Derbyia nipponica Nakamura, 1972a, p. 399, pl. 7, figs. 1, 4–9; Tazawa and Ibaraki, 2001, p. 14, pl. 3, figs. 1, 2, 4.
Derbyia cf. buchi (d’Orbigny, 1842). Tazawa and Matsumoto, 1998, p. 5, pl. 1, figs. 1–2.
Material.—Twelve specimens from locality MZ-S2: (1) internal mould of a conjoined valve, NU-B903; (2) external and internal moulds of four ventral valves, NU-B904-907; (3) internal moulds of three ventral valves, NU-B908-910; (4) external and internal moulds of a dorsal valve, NU-B911; (5) internal moulds of three dorsal valves, NU-B912-914.
Description.—Shell medium to large for genus, transversely subelliptical in outline; hinge much shorter than greatest width at about midvalve; length 48 mm, width 54 mm in the largest specimen (NU-B904). Ventral valve slightly convex to nearly flat, ornament consisting of numerous fine costellae and 5–8 irregular strong rugae; costellae with narrow interspaces, increasing by intercalation, numbering 9–11 in 5 mm at midvalve. Dorsal valve gently but more strongly convex than ventral valve, ornament same as opposite valve. Internally, ventral valve having thin, long median septum, extending to near midvalve; dorsal valve with divergent, strong crural plates.
Remarks.—These specimens can be referred to Derbyia nipponica Nakamura, 1972a, from the lower Kanokura Formation of the South Kitakami Belt, northeast Japan, on account of their medium to large, transverse shells with short hinge and regular, fine costellae on both valves.
Derbyia schellwieni Frech (1911, p. 125, pl. 18, figs. 3a–3d), from the Upper Permian (Lopingian) of Jiangxi, East China, is similar in size and outline, but the Chinese species is clearly distinguished from D. nipponica by its distinct parvicostellate ornament with strong first-order costellae.
Derbyia buchi (d’Orbigny, 1842), as illustrated in Kozlowski (1914, pl. 8, figs. 1–6), is similar in size, transverse outline, and slightly convex ventral valve, but differs in having fewer and stronger costellae on both valves.
The type species, Derbyia regularis Waagen (1884, p. 594, pl. 53, figs. 1, 2, 4), from the Amb and Wargal Formations of the Salt Range, differs from D. nipponica in having a wider hinge and much stronger and more regular costellae on both valves.
Distribution.—Middle Permian (Wordian-Capitanian) of central and northeast Japan (Hida Gaien and South Kitakami Belts); Upper Permian (Lopingian) of southwest Japan (Mizukoshi).
Order Orthida Schuchert and Cooper, 1932
Suborder Dalmanellidina Moore, 1952
Superfamily Enteletoidea Waagen, 1884
Family Schizophoriidae Schuchert and LeVene, 1929
Genus Acosarina Cooper and Grant, 1969
Type species.—Acosarina dorsisulcata Cooper and Grant, 1969.
Acosarina cf. circular Xu, 1987 Figures 8.7a–8.8b
Cf. Acosarina circular Xu, 1987, p. 216, 318, pl. 13, figs. 12, 13, 17.
Material.—Five specimens from locality MZ-S2: (1) external moulds of two ventral valves, NU-B859, 860; (2) internal moulds of three ventral valves, NU-B861–863.
Description.—Shell small for genus, subcircular or slightly wider than long, with greatest width at midvalve; length 10 mm, width 11 mm in the largest specimen (NU-B861). Hinge short, about half of width; anterior margin rounded, rectimarginate. Ventral valve slightly convex, no fold. External surface multicostellate, 4–5 costellae in 1 mm near anterior margin. Internally, ventral valve with short dental plates and low but long median septum, extending over two-thirds of length.
Remarks.—These specimens are safely assigned to the genus Acosarina by their small, subcircular, rectimarginate and multicostellate shell. In size, shape and internal structure of the ventral valve, especially its having a long median septum, the Mizukoshi specimens most resemble Acosarina circular Xu, 1987, originally described from the Wuchiapingian of Hunan, South China. Accurate comparison is, however, difficult due to the lack of examples of the dorsal valve.
The type species, Acosarina dorsisulcata Cooper and Grant (1969, p. 2, pl. 5, figs. 19–23; 1976, p. 2621, pl. 667, figs. 1–26; pl. 673, figs. 1–6) is also small in size, but the Texan species differs from the present species in having a relatively shorter ventral median septum.
Genus Orthotichia Hall and Clarke, 1892
Type species.—Orthis? morganiana Derby, 1874.
Orthotichia sp. Figures 8.9a, 8.9b
Material.—One specimen from locality MZ-S2, internal mould of a ventral valve, NU-B864.
Remarks.—The single ventral valve specimen from Mizukoshi is small in size (length 10 mm, width about 11 mm), subcircular in outline, and it has a pair of strong dental plates and a long median septum, extending slightly anterior to the ends of the dental plates. The surface ornament of the ventral valve is faintly imprinted, being multicostellate. This specimen is safely assigned to the genus Orthotichia on the basis of its small, subcircular ventral valve, with strong dental plates and long median septum. In Orthotichia the median septum is much shorter than that of Acosarina. The Mizukoshi specimen well resembles Orthotichia sp. Huang (1933, p. 6, pl. 1, figs. 6a–6d) from the Changhsingian of Guizhou, South China in size and outline of the ventral valve, but the poor preservation of the present material makes accurate comparison difficult.
Order Athyridida Boucot, Johnson and Staton, 1964
Suborder Retziidina Boucot, Johnson and Staton, 1964
Superfamily Retzioidea Waagen, 1883
Family Neoretziidae Dagys, 1972
Subfamily Hustediinae Grunt, 1986
Genus Hustedia Hall and Clarke, 1893
Type species.—Terebratula mormoni Marcou, 1858.
Hustedia ratburiensis Waterhouse and Piyasin, 1970 Figures 8.2a–8.6b
Hustedia ratburiensis Waterhouse and Piyasin, 1970, p. 138, pl. 23, figs. 15–30; Grant, 1976, p. 241, pl. 66, figs. 1–69; pl. 67, figs. 51–58; Archbold, 1999, figs. 5E–5H; Yanagida and Nakornsri, 1999, p. 118, pl. 32, figs. 11–16; Tazawa, 2001b, p. 299, figs. 8.6a–8.6c.
Hustedia thailandica Waterhouse and Piyasin, 1970, text-figs. 12, 13.
Hustedia nakornsrii Yanagida, 1970, p. 79, pl. 14, figs. 9a–9d.
Material.—Fifteen specimens from locality MZ-S2: (1) internal mould of a conjoined valve, NU-B1037; (2) external moulds of four ventral valves, NU-B1038–1041; (3) internal moulds of five ventral valves, NU-B1042–1046; (4) external mould of a dorsal valve, NU-B1047; (5) internal moulds of four dorsal valves, NU-B1048–1051.
Description.—Shell medium size for genus, suboval in outline, with greatest width slightly anterior to midvalve; length 9 mm, width 7 mm in the largest ventral valve specimen (NU-B1038); length 6 mm, width 7 mm in the best preserved dorsal valve specimen (NU-B1047). Ventral valve moderately convex in lateral profile, most convex at umbonal region, without sulcus. External surface of ventral valve ornamented by simple, broad and rounded costae; 2 close-set costae medianly and 4 pairs of costae laterally. Dorsal valve slightly transverse, moderately but more weakly convex than the opposite valve, without fold. Surface ornament same as ventral one, consisting of a median costa and 4 pairs of lateral costae. Internal structures are not well preserved in the present specimens.
Remarks.—The Mizukoshi specimens can be referred to Hustedia ratburiensis Waterhouse and Piyasin, 1970 by their size, outline and external ornament. This species was described and compared in detail by Waterhouse and Piyasin (1970) and Grant (1976).
Hustedia indica (Waagen, 1883, p. 493, pl. 35, figs. 1, 2) from the Wargal Formation of the Salt Range differs from H. ratburiensis in its more elongate shell with broader plicae.
The type species, Hustedia grandicosta (Davidson, 1862, p. 28, pl. 1, fig. 5; Waagen, 1883, p. 491, pl. 34, figs. 6–12) from the Productus Limestone of the Salt Range differs from the present species in having more numerous, finer costae on both the ventral and dorsal valves.
Distribution.—Lower Permian (Kungurian) to Upper Permian (Wuchiapingian) of Thailand (Khao Phrik, Khao Nong Ta On and Khao Hin King); Middle Permian (Wordian) to Upper Permian (Lopingian) of Japan (Moribu and Mizukoshi).
Order Rhynchonellida Kuhn, 1949
Superfamily Rhynchoporacea Muir-Wood, 1955
Family Rhynchoporidae Muir-Wood, 1955
Genus Rhynchopora King, 1865
Type species.—Terebratula geinitziana de Verneuil, 1845.
Rhynchopora matsumotoi sp. nov. Figures 8.10a–8.10c
Etymology.—Named for Prof. Tatsuro Matsumoto.
Material.—One specimen from locality MZ-S2, external mould of a dorsal valve and associated internal mould of the conjoined valve, NU-B1052 (holotype).
Diagnosis.—Small, transverse Rhynchopora, with 5 costae in ventral sulcus and 6 costae on dorsal fold.
Description.—Shell small for genus, transversely pentagonal in outline, with greatest width slightly anterior to midvalve; length about 10 mm, width 12 mm in the holotype specimen (NU-B1052). Ventral valve gently convex in lateral profile; sulcus wide and shallow. Dorsal valve gently convex, with a broad and low fold. External surface of both valves ornamented by simple numerous costae; 5 in ventral sulcus, 5–6 on each flank of ventral valve; 6 on dorsal fold, 4–5 on each flank of dorsal valve. Internal structures of both valves are obscure.
Remarks.—Rhynchopora matsumotoi n. sp. most resembles Rhynchopora tschernyschae Koczyrkevicz (1979, p. 47, pl. 11, figs. 1–4) from the Barabashevka Formation of South Primorye, Far East Russia in size and shape of the shell, but it differs from the Russian species in having more numerous costae on the ventral sulcus and dorsal fold.
Rhynchopora scorsa Reed (1944, p. 129, pl. 21, figs. 5–8) from the Wargal Formation of the Salt Range, Pakistan differs from the Mizukoshi species in its larger and less transverse shell.
Rhynchopora sp. Figures 8.11a, 8.11b
Material.—One specimen from locality MZ-S2, internal mould of a ventral valve, NU-B1053.
Remarks.—This specimen is safely assigned to the genus Rhynchopora by its small size (length 10 mm, width 11 mm), pentagonal outline, fine simple costae and broad and shallow ventral sulcus with 3 rounded costae in the bottom. The Mizukoshi specimen well resembles shells described as Rhynchopora tschernyshae Koczyrkevicz, 1979 from the upper Oyakejima Formation of the Ogatsu area, South Kitakami Belt, northeast Japan (Tazawa et al., 2000, p. 10, pl. 1, figs. 6a–6d), and Rhynchopora sp. from the lower Moribu Formation of the Moribu area, Hida Gaien Belt, central Japan (Shi and Tazawa, 2001, p. 756, figs. 2.2a, 2.2b; Tazawa, 2001b, p. 299, figs. 8.5a–8.5c) in size, shape and surface ornament of the ventral valve. But accurate comparison is difficult for the poorly preserved specimen.
Order Spiriferida Waagen, 1883
Suborder Spiriferidina Waagen, 1883
Superfamily Spiriferoidea King, 1846
Family Trigonotretidae Schuchert, 1893
Subfamily Neospiriferinae Waterhouse, 1968a
Genus Gypospirifer Cooper and Grant, 1976
Type species.—Gypospirifer nelsoni Cooper and Grant, 1976, p. 2214, pl. 591, figs. 6–9.
Gypospirifer volatilis Duan and Li, 1985 Figures 9.3–9.7
Figure 9.
1a–2b. Elivina sp., 1a, 1b: internal mould of a ventral valve, NU-B915, (1b ×2), 2a, 2b: internal mould of a dorsal valve, NU-B919, (2b ×2), 3–7. Gypospirifer volatilis Duan and Li, 3: internal mould of a ventral valve, NU-B726, 4: external latex cast of a ventral valve, GK-D31003, 5: external latex cast of a dorsal valve, GK-D31005, 6: external latex cast of a ventral valve, NU-B723, 7: internal latex cast of a ventral valve, NU-B724, 8a–14. Alispiriferella lita (Fredericks), 8a, 8b: external mould and external latex cast of a ventral valve, NU-B934, 9: external latex cast of a ventral valve, NU-B936, 10: external latex cast of a ventral valve, GK-D31017, 11: internal mould of a ventral valve, NU-B714, 12a, 12b: internal mould and internal latex cast of a ventral valve, NU-B950, 13a, 13b, 13c: external latex cast of a ventral valve and ventral and dorsal views of internal mould of a conjoined valve, NU-B924, 14: external latex cast of a ventral valve, NU-B935, 15a–18c. Dielasma sp., 15a, 15b: ventral and dorsal views of internal mould of a conjoined valve, NU-B1054, 16a, 16b, 16c: ventral, dorsal and lateral views of internal mould of a conjoined valve, NU-B1055, 17: internal mould of a ventral valve, NU-B1060, 18a, 18b, 18c: ventral, dorsal and lateral views of internal mould of a conjoined valve, NU-B1057. (Natural size unless otherwise indicated).
Spirifer cf. moosakhailensis Davidson: Noda, 1956, p. 17, pl. 4, figs. 9, 10.
Neospirifer fasciger (Keyserling): Yanagida, 1963, p. 71, pl. 8, figs. 1–7; pl. 9, figs. 1–3.
Neospirifer cf. fasciger (Keyserling): Yanagisawa, 1967, p. 90, pl. 2, fig. 18.
Neospirifer moosakhailensis (Davidson): Lee and Gu, 1976, p. 286, pl. 175, figs. 1–3 only.
Gypospirifer volatilis Duan and Li, 1985, p. 127, 207, pl. 48, figs. 1–2; pl. 49, figs. 1–2; Tazawa, 2001b, p. 302, figs. 8.23–8.26; Tazawa and Hasegawa, 2007, p. 7, figs. 4.8–4.12, 5.1, 5.2.
Gypospirifer sp. Tazawa, 2000, figs. 3.12, 3.13.
Neospirifer volatilis (Duan and Li): Wang and Zhang, 2003, p. 146, pl. 38, figs. 1–8.
Material.—Sixteen specimens from locality MZ-S1: (1) external moulds of two conjoined valves, GK-D31003, 31008; (2) external moulds of a ventral valve, NU-B723; (3) internal moulds of ten ventral valves, GK-D31001, 31002, NU-B724–731; (4) external moulds of three dorsal valves, GK-D31004, 31005, 31009.
Description.—Shell medium to large for genus, transversely semielliptical in outline with greatest width at hinge, and slightly alate; length about 50 mm, width more than 70 mm in the largest specimen (NU-B726); length about 38 mm, width about 60 mm in the best preserved specimen (GK-D31005). Ventral valve gently convex in lateral and anterior profiles, most convex at umbonal region; umbo slightly extended and strongly incurved; interarea moderately high, broad and gently concave; sulcus deep, narrow, and rapidly widening anteriorly, with U-shaped bottom. External surface of ventral valve ornamented by numerous costae and very fine growth lines; costae subridged, added by bifurcation, and weakly fasciculated, numbering 10–12 in 10 mm at about midvalve. Dorsal valve gently convex in both profiles, having a high and narrow fold. External ornament of dorsal valve similar to that of opposite valve. Ventral valve interior with a pair of thick, short dental plates and a deeply impressed muscle field.
Remarks.—The Mizukoshi specimens are not so well preserved but they can be identified with Gypospirifer volatilis Duan and Li, 1985, originally described from the Middle Permian Zhesi (Jisu) Formation of the Zhesi area, Inner Mongolia, by their size, outline, and surface ornamentation, especially the deep ventral sulcus and high dorsal fold. Tazawa (2001b, p. 302) has discussed this species and its comparison with related forms.
A single ventral specimen, described and figured by Yanagisawa (1967, p. 90, pl. 2, fig. 18) as Neospirifer cf. fasciger (Keyserling) from the Kashiwadaira Formation (= upper Takakurayama Formation) of the Takakurayama area, Abukuma Mountains, northeast Japan, is referred to Gypospirifer volatilis in its large size and having a fold rapidly widening anteriorly.
Distribution.—Middle Permian (Wordian-Capitanian) of North China (Zhesi and Xiujimqinqi, Inner Mongolia) and central Japan (Moribu in the Hida Gaien Belt); Upper Permian (Lopingian) of Northeast China (Jilin), northeast Japan (Takakurayama) and southwest Japan (Mizukoshi).
Family Spiriferellidae Waterhouse, 1968a
Genus Alispiriferella Waterhouse and Waddington, 1982
Type species.—Spirifer (Spiriferella) keilhavii (von Buch) var. ordinaria Einor in Licharew and Einor, 1939.
Alispiriferella lita (Fredericks, 1924) Figures 9.8a–9.14
Spiriferella saranae mut. lita Fredericks, 1924, p. 36, pl. 1, figs. 16–27; text-figs. 2a, 2b.
Spirifer cf. saranae mut. lita Fredericks. Hayasaka, 1925, p. 98, pl. 5, fig. 14.
Spiriferella cf. saranae mut. lita Fredericks. Nonaka, 1944, p. 86, pl. 7, figs. 12–14.
Spiriferella keilhavii (von Buch). Yanagida, 1963, p. 72, pl. 9, figs. 4–9; pl. 10, figs. 1–7.
Timaniella harkeri Waterhouse. Licharew and Kotlyar, 1978, pl. 18, figs. 2, 3.
Spiriferella grandis Kotlyar in Licharew and Kotlyar, 1978, p. 73, pl. 18, figs. 7, 8.
Spiriferella lita (Fredericks). Tazawa, 1979, p. 28, pl. 4, figs. 12–13; pl. 5, figs. 1–4, 6; Tazawa, 2001b, p. 302, figs. 8.19–8.22; Tazawa and Chen, 2006, p. 336, fig. 6.4; Tazawa and Hasegawa, 2007, p. 9, figs. 5.3–5.11.
Spiriferella cf. lita (Fredericks). Tazawa et al., 2000, p. 12, pl. 1, figs. 16, 17.
Alispiriferlla ordinaria (Einor in Licharew and Einor). Tazawa, 2001b, p. 302, figs. 8.14a–8.14c.
Alispiriferella japonica Tazawa, 2001b, p. 303, figs. 8.15–8.18.
Alispiriferella neimongolensis Wang and Zhang, 2003, p. 154, pl. 46, figs. 9–18; pl. 50, figs. 5, 9.
Material.—Seventy specimens from localities MZ-S1 and MZ-S2: (1) external and internal moulds of a conjoined valve (from MZ-S1), NU-B711; (2) external mould of a conjoined valve (from MZ-S2), NU-B923; (3) external mould of a ventral valve with internal mould of a conjoined valve (from MZ-S2), NU-B924; (4) internal moulds of nine conjoined valves (from MZ-S2), NU-B925–933; (5) external and internal moulds of a ventral valve (from MZ-S1), NU-B712; (6) external moulds of nine ventral valves (five specimens from MZ-S1), GK-D31013, 31014, 31017, 31022, 31023, (four specimens from MZ-S2), NU-B934–937; (7) internal moulds of forty-five ventral valves (eleven specimens from MZ-S1), NU-B713–721, GK-D31011, 31021, (thirty-four specimens from MZ-S2), NU-B938–971; (8) external and internal moulds of three dorsal valves (from MZ-S2), NU-B972–974; (9) external moulds of five dorsal valves (from MZ-S2), NU-B975–979; (10) internal moulds of twenty-six dorsal valves (one specimen from MZ-S1), NU-B722, (twenty-five specimens from MZ-S2), NU-B980–1004.
Description.—Shell large for genus, transversely trapezoidal in outline; hinge straight, equal to widest part; length about 27 mm, width about 70 mm in the largest specimen (NU-B713); length about 34 mm, width about 58 mm in another large specimen (NU-B934). Ventral valve moderately convex in lateral profile, with maximum convexity at umbonal slope; interarea moderately high, broad and gently concave, with large delthyrium; sulcus deep, wide and having smooth V-shaped bottom; 5 pairs of strong, simple, broad and rounded costae on each side of sulcus. Dorsal valve moderately convex in both lateral and anterior profiles; fold high, wide and having a median groove; 4–5 pairs of simple or bifurcated costae on each side of fold.
Ventral interior with a pair of high dental plates and a deeply impressed heart-shaped muscle field. Dorsal interior with small, laminated cardinal process and subhorizontal socket plates. Other internal structures are obscure.
Remarks.—These specimens are referred to Alispiriferella lita (Fredericks, 1924), originally described from the Middle Permian of the Vladivostok area, South Primorye, by their large, transverse shells, ventral sulcus with smooth V-shaped bottom and strong, simple and rounded costae on the ventral valves.
The type species, Alispiriferella ordinaria (Einor in Licharew and Einor, 1939) from the Lower Permian of Novaya Zemlya is clearly distinguished from A. lita by its smaller and less transverse shell with ventral sulcus bearing two prominent sulcal costae and more often fasciculate costae on both ventral and dorsal valves.
The smaller specimens, described by Tazawa (2001b) as A. ordinaria and Alispiriferella japonica Tazawa, 2001b from the Middle Permian of Moribu, central Japan seem to be young shells of A. lita, in that they have a smooth-bottomed ventral sulcus.
Distribution.—Middle Permian (Wordian-Capitanian) of North China (Zhesi and Xiujimqinqi, Inner Mongolia), Northeast China (Heilongjiang), eastern Russia (South Primorye), northeast Japan (Kesennuma in the South Kitakami Belt), central Japan (Moribu in the Hida Gaien Belt); Upper Permian (Lopingian) of northeast Japan (Ogatsu in the southern Kitakami Mountains) and southwest Japan (Mizukoshi).
Genus Elivina Fredericks, 1924
Type species.—Spirifer tibetana Diener, 1897.
Elivina sp. Figures 9.1a–9.2b
Material.—Eight specimens from locality MZ-S2: (1) internal mould of a ventral valve, NU-B915; (2) external and internal moulds of a dorsal valve, NU-B916; (3) external moulds of two dorsal valves, NU-B917, 918; (4) internal moulds of a dorsal valve with posterior fragment of the ventral valve, NU-B919; (5) internal moulds of three dorsal valves, NU-B920-922.
Remarks.—These specimens are safely assigned to the genus Elivina by their small, elongate oval shell (length about 18 mm, width about 16 mm in the single ventral valve specimen, NU-B922) with short hinge and 3 or 4 simple coarse costae on each side of both the ventral and dorsal valves. The Mizukoshi species resembles Elivina bishaini Archbold and Barkham (1989, p. 132, figs. 6A–6Z, 6AA–6LL) from the Maubisse Formation of Bisnain, West Timor in size and outline of the shell, but it differs from the Timor species in having coarse simple costae on both valves.
The type species, Elivina tibetana (Diener, 1897, p.45, pl. 6, figs. 1–7) from the Chitichun Limestone is also elongate oval in outline, but it is much larger in size.
Order Terebratulida Waagen, 1883
Suborder Terebratulidina Waagen, 1883
Superfamily Dielasmatoidea Schuchert, 1913
Family Dielasmatidae Schuchert, 1913
Subfamily Dielasmatinae Schuchert, 1913
Genus Dielasma King, 1859
Type species.—Terebratulites elongatus Schlotheim, 1816.
Dielasma sp. Figures 9.15a–9.18c
Material.—Nine specimens from locality MZ-S2: (1) internal moulds of five conjoined valves, NU-B1054–1058; (2) internal moulds of four ventral valves, NU-B1059–1062.
Description.—Shell medium size for genus, elongate subpentagonal in outline, with greatest width slightly anterior to midvalve; length 31 mm, width about 20 mm in the largest specimen (NU-B1062). Ventral valve gently and unevenly convex in lateral profile, rather strongly convex in umbonal region but flattened on venter; sulcus broad and shallow on anterior one-third of the valve. Dorsal valve less convex; fold absent. Surface ornament not well preserved in the present specimens. Ventral interior with a pair of strong, subparallel dental plates. Internal structures of dorsal valve obscure.
Remarks.—These specimens are safely assigned to the genus Dielasma by their size and shape of the shell and in having strong dental plates in the ventral valve. The Mizukoshi species superficially resembles Dielasma timanica Tschernyschew (1902, p. 38, 459, pl. 1, fig. 2; pl. 2, fig. 9) from the Lower Permian of Timan and the Urals, although it is smaller in size than the Russian species.
Dielasma sp. (Tazawa, 2001b, p. 303, figs. 8.27, 8.28) from the lower Moribu Formation of Moribu, Hida Gaien Belt, central Japan is clearly distinguished from the present species in having a narrow but distinct median fold on the ventral valve.
Acknowledgments
Sincere thanks are due to S. Hasegawa, Yachiyo Engineering Co., Ltd., Fukuoka, for his help in the field; T. Kurihara, Department of Geology, Niigata University for his help drawing figures; and G. R. Shi, Deakin University, Melbourne and S. Z. Shen, Nanjing Institute of Geology and Palaeontology, Academia Sinica for their critical review of the manuscript by which this paper is greatly improved.
