地球科学 73 巻,139 ~ 148(2019 年) 139 Earth Science (Chikyu Kagaku) vol. 73, 139-148. 2019
Two additional araxoceratid ammonoids from the Wuchiapingian (upper Permian) of the South Kitakami Belt, Northeast Japan
EHIRO Masayuki*
Abstract Two Wuchiapingian (late Permian) ammonoids, Vedioceras sp. and Urartoceras sp., both belonging to the family Araxoceratidae, are described from the South Kitakami Belt, Northeast Japan. Araxoceratid ammonoids were widespread in the low-latitude regions of the Tethys, Tethys-Panthalassa border and eastern Panthalassa regions. The Wuchiapingian araxoceratid fauna of the South Kitakami Belt, including with the known araxoceratid ammonoids such as Araxoceras cf. rotoides, A. sp., Dzhulfoceras cf. furnishi, D. sp, Vescotoceras japonicum, V. sp. and Eusanyangites cf. bandoi, has a close similarity to that of the western Tethys Province in the generic composition.
Key Words : Ammonoid, Araxoceratidae, paleobiogeography, Permian, South Kitakami Belt, Wuchiapingian
Introduction 2001b). Recently, two additional araxoceratid specimens were collected The Ceratitida, which is the prevailing ammonoid order in the from the Motoyoshi and Utatsu areas. This paper describes these Triassic, appeared at the beginning of the Guadalupian (middle two ammonoids as Urartoceras sp. and Vedioceras sp., and Permian) and the species belonging to the family Araxoceratidae discusses their significance. had already flourished in the low-latitude regions during Wuchiapingian time (early Lopingian: late Permian). Therefore, Note on the fossil locality araxoceratid ammonoids are important from the viewpoints of late Permian stratigraphy and biogeography. They prospered in the The araxoceratid-bearing upper Permian strata are distributed in western Tethys Province (Azerbaijan, Armenia, and Julfa and the Motoyoshi and Utatsu areas of the South Kitakami Belt, Abadeh in Iran) (e.g. Ruzhencev 1959, 1962, 1963; Bando 1979; Northeast Japan. These two areas both occupy the eastern wing of Zakharov et al. 2010) and South China (e.g. Chao 1965; Zhao et al. a broad syncline whose axis trends NNE–SSW (Fig. 1). 1978; Liang 1983; Qin 1986; Yang and Xiong 1990). They are also known from the South Primorye region of Far East Russia Motoyoshi Area (Zakharov and Pavlov 1986a), South Kitakami Belt of Northeast At the Maehama coast in the Motoyoshi Area, the Lopingian Japan (Murata and Bando 1975; Ehiro and Bando 1985; Ehiro (upper Permian) Toyoma Formation and the Olenekian (upper part 2001b), Thailand? (Fujikawa and Ishibashi 1999) and Mexico of the Lower Triassic) Hiraiso Formation are exposed. Along the (Spinosa et al. 1975). northern coast of Maehama, the Toyoma Formation crops out more From the Wuchiapingian strata of the South Kitakami Belt, than 45 m in thickness, consisting mainly of massive or poorly seven species belonging to four genera of the family laminated black mudstones with a subordinate amounts of Araxoceratidae have hitherto been known: Eusanyangites cf. lenticular thin sandstones and calcareous, phosphatic nodules (Fig. bandoi Zakharov and Pavlov (originally described as Araxoceras 2). It is overlain unconformably by the basal conglomerate of the cf. kiangsiense Chao) from Motoyoshi Area (Murata and Bando Hiraiso Formation. Murata and Bando (1975) described an 1975), and Araxoceras cf. rotoides Ruzhencev, Araxoceras sp., ammonoid, Araxoceras cf. kiangsiense (Chao), from a horizon Dzhulfoceras cf. furnishi Ruzhencev, Dzhulfoceras sp., about 15 m below the boundary between the Toyoma and Hiraiso Vescotoceras japonicum (Bando and Ehiro) (originally described as formations, and correlated the ammonoid horizon (middle part of Prototoceras japonicum), Vescotoceras sp. (originally as the Toyoma Formation) with the Dzhulfian (equivalent of the Prototoceras sp.) from Utatsu Area (Ehiro and Bando 1985; Ehiro Wuchiapingian) of Iran. From an interval of 10 to 20 meters below
Received March 11, 2019. Accepted June 3, 2019. Editor NAKAI Hitoshi * Sendai Branch, the Tohoku University Museum, Aoba 6-3, Aramaki, Aoba-ku, Sendai City, Miyagi 980-8578, Japan (e-mail: [email protected])
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Fig. 1 Index map (A) and simplified geologic map of the southern part of the South Kitakami Belt in the Kitakami Massif, Northeast Japan, showing the fossil localities (B).
the boundary between the Toyoma and Hiraiso formations, including the ammonoid horizon, Murata and Bando (1975) reported the occurrences of some bivalves and gastropods, such as Palaeoneilo ogachiensis Hayasaka, Phestia kon'noi Murata and Kitakamispira hanzawai Murata. These molluscs belong to the Palaeoneilo ogachiensis-Phestia kon'noi Zone (Murata 1969) of the middle part of the Toyoma Formation, and therefore, Murata and Bando (1975) considered that the upper part of the Toyoma Formation is missing in this area. This ammonoid, A. cf. kiangsiense of Murata and Bando (1975), was subsequently Fig. 2 Columnar section of the Toyoma Formation and the basal part of the Hiraiso Formation in the Motoyoshi Area at Maehama coast, compared with Eusanyangites bandoi Zakharov and Pavlov Motoyoshi-cho, Kesennuma City, Miyagi Prefecture, showing the horizon described from the South Primorye (Zakharov 1986). Zakharov of the present and known ammonoids. (1986) correlated the E. bandoi beds of Primorye with the Sanyangites Zone (Zhao et al. 1978) of South China, which Utatsu Area occupies the upper part of the Wuchiapingian Stage. Ehiro (2001b) In the Utatsu Area, the late Capitanian to Wuchiapingian reported an occurrence of Stacheoceras? sp. from the same locality, Suenosaki Formation (more than 800 m in thickness) and but slightly lower horizon (Fig. 2). overlaying Changhsingian (late Lopingian) Tanoura Formation One of the present ammonoid specimens, described as (more than 700 m) are widely distributed (Ehiro and Bando 1985) Urartoceras sp., was collected from the mudstone about 30 m (Fig. 3). The latter is in fault contact with or unconformably below the top of the Toyoma Formation distributed on the northern overlain by the Triassic Hiraiso Formation. The lowermost part of coast of Maehama (38°47′59″N, 141°32′50″E). Bivalves P. the Suenosaki Formation yields Capitanian fusulinids, such as ogachiensis and P. kon'noi also occur in and around this ammonoid Lepidolina kumaensis Kanmera and L. multiseptata (Deprat) horizon. This horizon (Maehama Horizon) is slightly (about 15 m?) (Murata and Shimoyama 1979). There are two pebbly mudstone lower than that of E. cf. bandoi (Fig. 2), but their precise beds in the lower part of the formation. The lower pebbly mudstone stratigraphic relationship is unknown, because Murata and Bando (Ishihama-1 Horizon: locality 3 of Ehiro and Bando 1985, figs. 3 (1975) did not show the precise information of their fossil locality. and 4) yields some ammonoids from the calcareous, phosphatic
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above the lower pebbly bed. Some bivalves and gastropods, such as Euphemitopsis kitakamiensis Murata and Astartella toyomensis Nakazawa and Newell, index fossils of the Euphemitopsis kitakamiensis-Astartella toyomensis Zone (Murata 1969) and characteristic in the lower part of the Toyoma Formation, were reported from both the lower and upper pebbly mudstone beds (Murata and Shimoyama 1979). Based on the ammonoids, above ammonoid-bearing horizon is correlated with the Dzhulfian (Wuchiapingian) (Ehiro and Bando 1985). The lower part of the Tanoura Formation yields Changhsingian smaller foraminifer Colaniella aff. inflata (Wang) and fusulinid Palaeofusulina sp. (Murata and Shimoyama 1979). Present ammonoid specimen, Vedioceras sp., was collected from the basal part of the upper pebbly mudstone (Fig. 3, Ishihama-2 Horizon) distributed along the northern coast of Ishihama (locality 8 of Ehiro and Bando 1985, figs. 3 and 4; 38°43′56″N, 141°33′46″E).
Systematic description
The specimens described here are kept in the Tohoku University Museum (Institution abbreviation: IGPS = Institute of Geology and Paleontology, Tohoku University, Sendai).
Order Ceratitida Hyatt 1884 Superfamily Otoceratoidea Hyatt 1900 Family Araxoceratidae Ruzhencev 1959 Subfamily Araxoceratinae Ruzhencev 1959
Discussion.—Leonova (2002) lumped many genera in the subfamily Araxoceratinae together. For example, she considered the genera Rotaraxoceras, Vedioceras, Kiangsiceras, Konglingites and Sanyangites are synonymous with the genus Araxoceras, and the genera Discotoceras, Urartoceras, Vescotoceras and Jinjiangoceras with the genus Prototoceras. This proposal is, however, not supported by any discussion. I think each genus above has its own distinctive characteristics, and, for the time being, treat them as distinct genera. Fig. 3 Columnar section of the Permian strata in the Utatsu Area along the northern coast of Utatsu, Minamisanriku Town, Miyagi Prefecture, showing the horizons of the present and known ammonoids and Genus Vedioceras Ruzhencev 1962 foraminifers. Cp.: Capitanian. Type species.—Vedioceras ventroplanum Ruzhencev 1962 nodules: they comprise the araxoceratids, Araxoceras cf. rotoides, Araxoceras sp., Vescotoceras japonicum, Vescotoceras sp., Vedioceras sp. Dzhulfoceras cf. furnishi and Dzhulfoceras sp., in association with Figures 4.1a–1d some goniatitids, such as Pseudogastrioceras sp., Stacheoceras giganteum Ehiro, S. iwaizakiense Mabuti and Timorites sp. nov. Material.—A deformed specimen, IGPS coll. cat. no. 112267, (Ehiro and Bando 1985; Ehiro et al. 1986; Ehiro 2001b, 2006). The collected by Masaki Takahashi. upper pebbly bed (Ishihama-2 Horizon) is located about 80 meters Description.—Flattened and elliptically deformed, parts of inner
( 29 ) 142 E a ayuki and outer molds are present. The conch attains a diameter (D) of conch attains a diameter of about 113 mm along the longest axis of about 57 mm along the longest axis of the elliptically deformed the elliptically deformed specimen, and the corresponding height specimen, and the corresponding height (H) and umbilical diameter and the umbilical diameter are ca. 58 and ca. 20 mm, respectively. (UD) are ca. 22 and 14 mm, respectively. The H/D is 0.39 and UD/ The UD/D is 0.18. Although the exact shell width is not known due D is 0.25. Although the original conch form is unclear due to the to the tectonic flattening, the shell cross section, in the deformed flattening of the specimen, it displays nearly flat sides, the outer state, is discoidal (Fig. 4.2c). The flared umbilical rim occupies the half of which is slightly concave. The ventral shoulder of the inner umbilical one-fourth to one-third of the lateral sides with mold is acutely rounded, but that of the outer mold is edged. The decreasing its height to the venter, and therefore, the maximum venter is slightly convex to nearly flat. The umbilical margin has a shell width is near the umbilical edge. The remaining lateral sides narrow and low, but distinct rim (Fig. 4.1c), and the maximum are slightly concave to flat, but this concave structure is considered shell width is at the umbilical shoulder. The shell surface appears to be caused by the lateral flattening. The venter is roof-shaped to be smooth, but, on the outer mold, some indistinct structures are with angular ventral shoulders and a low median ridge (Fig. 4.2d). observed. On the lateral side, there are widely spaced (3 folds per Faint, prorsiradiate, concave ribs are observed on the shell surface quarter of a volution), low, radial folds (Fig. 4.1c), which run from (Fig. 4.2b). They are wide with narrow interspaces. near the umbilical margin to two-thirds of the lateral side. On the The septa are largely destroyed and only an umbilical one-thirds venter of the outer mold, about a half of which is preserved, some of the external suture is preserved: a part of probable second lateral longitudinal lirae are visible. They are very fine and faint, and lobe and strongly crenulated umbilical series (Fig. 4.2e). The number more than five, including that located on the ventral second lateral lobe is strongly denticulate. The second incision of shoulder (Fig. 4.1d). The suture is not preserved. the umbilical series is very deep and its ventral side is serrated. Discussion.—Although the suture is not known, the present Discussion.—Based on the general conch form, having a specimen can be assigned with confidence to Vedioceras discoidal shell with a flared umbilical rim and a carinated venter, Ruzhencev 1962, based on the shell form, having nearly parallel the present specimen is considered to belong to the genus sides, flat venter with edged ventral shoulders and rather wide Urartoceras Ruzhencev, 1959. Genus Prototoceras Spath 1930 umbilicus with low rim. The present species somewhat similar to also has a flared umbilical rim and a carinated venter, but the Vedioceras nakamurai Bando (Bando 1979, p. 117, text-figure 3C– umbilical series of the external suture of the genus is only weakly D, pl. 4, figs. 3–4) from Abadeh, central Iran by having rather crenulated and differ clearly from that of the present specimen. The compressed shell with nearly parallel sides. But, the present present species is distinguished from Urartoceras abichianum specimen has a smaller umbilicus (UD/D = 0.25) than V. Ruzhencev (Ruzhencev 1959, p. 64, fig. 1g, 2g; 1962, p. 94, fig. 5; nakamurai (UD/D = 0.32–0.35). In addition, the present specimen Ruzhencev and Sarycheva 1965, pl. 18.5) from Azerbaijan, which is unique in having radial folds on the sides and in having fine lirae is a type species of the genus, in having a low median ridge of the on the venter. Thus the present species is thought to be a new venter, in having ribs on the lateral sides and in having serrated species, but I refrain from identifying it at the specific level, second incision of the umbilical series of the external suture. The because the specimen is poorly preserved. present species also differ from Urartoceras sp. (Teichert et al. Occurrence.—Lower part of the Suenosaki Formation exposed 1973, p. 410, text-fig. 11K, pl. 3, figs. 7-8) from Kuh-E-Ali Bashi, at Ishihama coast, Utatsu, Minamisanriku Town, Miyagi Prefecture. northwest Iran, which has a low median ridge of the venter similar Middle Wuchiapingian. to the present species, in having ribs on the lateral sides and in having serrated second incision of the umbilical series. The present Genus Urartoceras Ruzhencev 1959 species may be a new species, but further identification will require additional well-preserved material. Type species.—Urartoceras abichianum Ruzhencev 1959 Occurrence.—From the middle part of the Toyoma Formation exposed at Maehama coast, Motoyoshi-cho, Kesennuma City, Urartoceras sp. Miyagi Prefecture. Late Wuchiapingian. Figures 4.2a–2e Discussion Material.—A deformed specimen, IGPS coll. cat. no. 112268. Description.—Flattened and obliquely deformed specimen is Stratigraphic and geographic distribution of the examined. It is large and consists of phragmocone and body araxoceratid ammonoids outside Japan chamber, the latter of which occupies about a half volution. The The Wuchiapingian strata of the South Kitakami Belt yield six
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Fig. 4 Ammonoid fossils from the Wuchiapingian of the South Kitakami Belt at Maehama, Motoyoshi-cho, Kesennuma City and at Ishihama, Utatsu, Minamisanriku Town, Miyagi Prefecture. 1, Vedioceras sp., IGPS coll. cat. no. 112267; 1a, lateral view of the inner mold; 1b, ventral view of the inner mold; 1c, rubber cast of the outer mold (arrows indicate radial folds); 1d, ventral view of the rubber cast of outer mold (arrows indicate longitudinal striae; vs: ventral shoulder); 2, Urartoceras sp., IGPS coll. cat. no. 112268; 2a and 2b, lateral views (ls: last septum); 2c, cross section of the shell; 2d, ventral view showing the median ridge (mr); 2e, suture line. Scale bars are 1 cm, unless otherwise stated. araxoceratid genera, inclusive of the present species: Araxoceras, Eusanyangites, are known from the western Tethys Province Dzhulfoceras, Urartoceras, Vedioceras, Vescotoceras and (Azerbaijan, Armenia, and Julfa and Abadeh in Iran), whereas only Eusanyangites. Among these, five genera, except for Araxoceras has also been reported from South China. Zakharov
( 31 ) 144 E a ayuki and Oleinikov (1994) reported an occurrence of a new species of in Julfa. These three zones are also roughly correlatable, Dzhulfoceras, D. orientale Zakharov, from the upper Dorashamian respectively, with the“ Araxilevis Beds”, Araxoceras tectum and strata of South Primorye. But there still remains doubt about the Vedioceras nakamurai zones in Abadeh, central Iran (Iranian- generic assignment of this species. Because, the external lateral Japanese Research Group 1981). In this paper, stratigraphic suture line of the genus Dzhulfoceras has two large saddles and horizons of these three fossil zones in the Dzhulfian are, herein lobes with a rather long umbilical series. The last occupies about after, referred to the lower, middle and upper Dzhulfian, umbilical one-thirds of the lateral sides, and consists 4-5 pairs of respectively. In these areas, ammonoids are known from the middle small rounded saddles and pointed lobes. The Primorye species, and upper Dzhulfian (Fig. 5). however, has a very short umbilical series consisting of only one In South China, the Wuchiapingian Stage is subdivided into the pair. Outside Japan, Eusanyangites is only known from South Laibinian and Laoshanian substages, in ascending order (Jin et al. Primorye. 1998; Jin and Shang 2000). Seven conodont zones based on the The stratigraphic distributions of these araxoceratid genera Clarkina species are established in the Wuchiapingian: the C. outside Japan are as follows: postbitteri postbitteri, C. dukouensis and C. asymmetrica zones, in In the Transcaucasia (Azerbaijan, Armenia and Julfa), the ascending order, in the Laibinian, and the C. leveni, C. Dzhulfian (Wuchiapingian) are divided into three zones: the guangyuanensis, C. transcaucasica and C. orientalis zones in the Pseudodunbarula arpaensis-Araxilevis intermedius, Araxoceras Laoshanian (Shen et al. 2010, 2019; Yuan et al. 2017). Based on latissimum and Vedioceras ventrosulcatum zones, in ascending the conodont stratigraphy of Shen and Mei (2010) in Iran, the order (Zakharov et al. 2010). They correspond, respectively, to the lower, middle and upper Dzhulfian are correspond to the C. Araxilevis-Orthotetina, Pseudogastrioceras-Permophricodothyris dukouensis to the C. leveni (Laibinian to the lowermost and Haydenelia-Pseudowellerella zones of Stepanov et al. (1969) Laoshanian), the C. guangyuanensis to the lower part of the C.
Fig. 5 Ammonoid occurrences in the Dzhulfian (Wuchiapingian) of Armenia, Azerbaijan, Julfa and Abadeh, and its correlation with conodont zones in Abadeh. The Clarkina postbitteri postbitteri Zone has not been confirmed in Abadeh.
( 32 ) ra ocerati a onoi ro Kitaka i 145 transcaucasica (lower to middle Laoshanian) and the upper part of Ghaderi et al. 2014). Based on the correlation of Shen and Mei the C. transcaucasica to the C. orientalis zones (middle to upper (2010), the horizon of Urartoceras sp. of Teichert et al. (1973) is Laoshanian), respectively (Fig. 5). In Abadeh, the lower most part equivalent with the upper part of the Araxilevis bed (the Clarkina of the Unit 7 (upper Hambast Formation), which overlies the leveni Zone; the lower Dzhulfian). As pointed out by Ghaderi et al. Dzhulfian beds (Unit 6: lower Hambast Formation) and once (2014), however, this Urartoceras specimen was collected from a included in the Dorashamian (Changhsingian), yields float and not in situ (Teichert et al. 1973), and thus, the precise Wuchiapingian conodont C. orientalis (Shen and Mei 2010). stratigraphic position in the Dzhulfian is unknown. Therefore, the lowermost part of the“ Dorashamian” in Abadeh is The occurrence of the genus Vedioceras is restricted from the correlated with the upper Laoshanian. upper Dzhulfian in Armenia, Azerbaijan (Ruzhencev 1962, 1963; In Azerbaijan, the species of the genus Araxoceras are described Ruzhencev and Sarycheva 1965) and Julfa (Stepanov et al. 1969). only from the middle Dzhulfian (Ruzhencev 1959, 1962; In Abadeh, however, they are reported from both the middle and Ruzhencev and Sarycheva 1965), but, in contrast, they are known upper Dzhulfian (Bando 1979; Iranian-Japanese Research Group only from the upper Dzhulfian in Julfa (Stepanov et al. 1969) and 1981) and from the basal part of the Unit 7 of the Hambast from both the middle and upper Dzhulfian in Abadeh (Bando 1979; Formation (Zakharov et al. 2010) (Fig. 5). The last specimen Iranian-Japanese Research Group 1981; Zakharov et al. 2010) (Fig. probably belongs to the C. orientalis Zone. 5). A. rotoides, to which the Kitakami species was compared, also The range of the genus Vescotoceras, in Azerbaijan and Julfa, is ranges from the middle to upper Dzhulfian. In South China, limited in the middle Dzhulfian (Ruzhencev 1959, 1962; Araxoceras are known from the middle Wuchiapingian Ruzhencev and Sarycheva 1965; Stepanov et al. 1969), but it Araxoceras-Konglingites Zone (Zhao et al. 1978). However, the ranges up to the upper Dzhulfian in Abadeh (Bando 1979) (Fig. 5). precise stratigraphic position of this zone is not clear. Because, in Outside Japan, the genus Eusanyangites is only known from the South China, Araxoceras species have only been known from the Eusanyangites bandoi beds of the South Primorye (Zakharov and Jiangxi Province: from the middle to upper part of the Laoshan Pavlov 1986a, 1986b). Zakharov and Pavlov (1986b) correlated the Member (middle Wuchiapingian) in Fengchen (Zhao et al. 1978; E. bandoi beds with the upper Wuchiapingian, and Zakharov (1986) Qin 1986) and from the lower-middle part of the Wuchiapingian in considered that the beds correspond with the Sanyangites Zone Shanggao (Qin 1986; Wang et al. 1997), and the generic (upper Wuchiapingian) of South China and the Vedioceras assignment of the latter is somewhat questionable. In addition, the ventrosulcatum Zone (upper Dzhulfian) of Azerbaijan. conodont data concerning these ammonoid zones are also limited. Only Wang et al. (1997) reported an occurrence of C. leveni from Correlation of the araxoceratids-bearing beds of the South the bed just below the Araxoceras?-bearing bed in Shanggao. Kitakami Belt When these occurrences of C. leveni and Araxoceras? are The araxoceratid-bearing beds in the South Kitakami Belt are emphasized, the age of the genus Araxoceras in Jiangxi is early (to known from three localities (horizons): 1) The lower pebbly middle?) Laoshanian. mudstone bed (Ishihama-1 Horizon) and 2) the upper pebbly The species of the genus Dzhulfoceras, including D. furnishi, are mudstone bed (Ishihama-2 Horizon) of the lower part of the known from the upper Dzhulfian of Azerbaijan (Ruzhencev 1962, Suenosaki Formation at Ishihama, Utatsu Area, and 3) the middle 1963; Ruzhencev and Sarycheva 1965) and the“ Dorashamian” part of the Toyoma Formation at Maehama, Motoyoshi Area (Shevyrevites bed) of Abadeh (Bando 1979). The latter horizon is (Maehama Horizon). The Ishihama-1 Horizon yields araxoceratid probably in the C. orientalis Zone and corresponds to the upper ammonoids such as Araxoceras cf. rotoides, A. sp., Dzhulfoceras Laoshanian (Fig. 5). cf. furnishi, D. sp., Vescotoceras japonicum and V. sp., associated Urartoceras species have hitherto been only reported from the with some goniatitids (Pseudogastrioceras, Stacheoceras and middle-upper Dzhulfian of Azerbaijan (Ruzhencev 1959; Timorites). These three araxoceratid genera range from lower to Ruzhencev and Sarycheva 1965: type species U. abichianum upper Laoshanian (middle to upper Wuchiapingian), upper Ruzhencev) and from the basal part of the“ Ali Bashi Formation” Laoshanian and lower to upper Laoshanian, respectively. Although at Julfa (Teichert et al. 1973: Urartoceras sp.) (Fig. 5). The latter the range of the genus Dzhulfoceras is limited to the upper species was corrected from bed 3 of locality 4 at the Kuh-e-Ali Laoshanian in the western Tethys Province, it is highly probable Bashi Section. Teichert et al. (1973) correlated the beds 1-7 of that the Ishihama-1 Horizon is correlated with the lower locality 4 with the Ali Bashi Formation of Dorashamian age. This Laoshanian, rather than the upper Laoshanian. Because, 1) this sequence (beds 1-7), however, yields typical Wuchiapingian horizon is in the Euphemitopsis kitakamiensis-Astartella (Dzhulfian) conodonts (Sweet and Mei 1999; Shen and Mei 2010; toyomensis Zone of the lower part of the Toyoma Formation, and 2)
( 33 ) 146 E a ayuki the lowermost part of the Suenosaki Formation, about 90 meters reconstruction of the South Kitakami might also be applicable to below the Ishihama-1 Horizon, yields Capitanian fusulinid late Permian time. Lepidolina and, on the other hand, there is an interval of 700 to 800 meters from this horizon to the Changhsingian fossil-bearing Acknowledgments horizon of the Tanoura Formation. The Ishihama-2 Horizon yields only one ammonoid specimen belongs to the genus Vedioceras, The author thanks Dr. Masaki Takahashi (Nat. Inst. Adv. Ind. which ranges from the lower to the upper Laoshanian in the Sci. Tech. Japan) for providing his specimen and Dr. Noritoshi western Tethys Province. This horizon may also be correlated with Suzuki (Tohoku Univ.) for his help with the literature. The the lower Laoshanian on the same ground as the Ishihama-1 manuscript was greatly improved by the constructive reviews of Horizon. Urartoceras and Eusanyangites are known from the Dr. Masayuki Fujikawa, Mr. Hitoshi Nakai (editor) and an Maehama Horizon. The former genus ranges from the lower to anonymous reviewer. upper Laoshanian, but the latter is known only from the upper Laoshanian. While taking into account that this horizon belongs to References the Palaeoneilo ogachiensis-Phestia kon'noi Zone of the middle part of the Toyoma Formation (Murata and Bando 1975), it is Bando Y (1979) Upper Permian and Lower Triassic ammonoids from highly probable that the Maehama Horizon is late Laoshanian in Abadeh, central Iran. Mem Fac Educ, Kagawa Univ, Ser II, 29: 103- 138. age. Chao K (1965) The Permian ammonoid-bearing formations of South China. Scientia Sinica, 14: 1813-1825. Paleobiogeographic significance of the Araxoceratid fauna Ehiro M (2001a) Origins and drift histories of some microcontinents The distribution areas of the araxoceratid genera known from the distributed in the eastern margin of Asian Continent. Earth Sci (Chikyu Kagaku), 55: 71-81. South Kitakami Belt are rather limited, except for the genus Ehiro M (2001b) Some additional Wuchiapingian (Late Permian) Araxoceras. Outside Japan, the genera Dzhulfoceras, Urartoceras, ammonoids from the Southern Kitakami Massif, Northeast Japan. Vedioceras, and Vescotoceras are only known from the western Paleont Res, 5: 111-114. Tethys Province (Armenia, Azerbaijan, Julfa and Abadeh), and Ehiro M (2006) A new species of Stacheoceras (Permian ammonoid) from the Upper Permian in the South Kitakami Belt, Northeast Japan. have not been reported from South China, South Primorye, Paleont Res, 10: 261-264. Thailand and Mexico. Araxoceras species are also known from Ehiro M and Bando Y (1985) Late Permian ammonoids from the South China in addition to the western Tethys, but, Araxoceras Southern Kitakami Massif, Northeast Japan. Trans Proc Palaeont Soc 137 25 49 rotoides, to which the Kitakami species was compared, is known Japan, NS, : - . Ehiro M, Sasaki O and Kano H (2016a) Ammonoid fauna of the late only from the western Tethys. On the other hand, the genus Olenekian Osawa Formation in the Utatsu area, South Kitakami Belt, Eusanyangites is only known from South Primorye. Northeast Japan. Paleont Res, 20: 90-104. It is considered that the South Kitakami Belt had located in the Ehiro M, Shimoyama S and Murata M (1986) Some Permian Cyclolobaceae from the Southern Kitakami Massif, Northeast Japan. low-latitude region near South China during the middle to late Trans Proc Palaeont Soc Japan, NS, 142: 400-408. Paleozoic based on the Silurian-Carboniferous coral fauna, and Ehiro M, Tsujimori T, Tsukada K and Manchuk N (2016b) Chapter Permian coral, bivalve and ammonoid faunas (e.g. Ehiro 2001a; 2a. Palaeozoic basement and associated cover. In: Moreno T, Wallis Ehiro et al. 2016b). The araxoceratid fauna of the South Kitakami, S, Kojima T and Gibbons W (eds), The Geology of Japan, 25-60, Geological Society, London. however, most resembles with those of the western Tethys Province Fujikawa M and Ishibashi T (1999) Carboniferous and Permian in the generic composition, and not with that of South China. The ammonoids from northern Thailand (Paleontological study of Paleozoic close faunal relationship with the western Tethys, as well as the Cephalopoda in Southeast Asia-1). Mem Fac Sci, Kyushu Univ, Ser D, eastern Panthalassa, was also argued by Ehiro et al. (2016a) based Earth and Planet Sci, 30: 91-110, pls. 2-3. Ghaderi A, Leda L, Schobben M, Korn D and Ashouri AR (2014) on the Early Triassic Olenekian ammonoid fauna. Ehiro et al. High-resolution stratigraphy of the Changhsingian (Late Permian) (2016a) considered that this faunal similarity between the South successions of NW Iran and the Transcaucasus based on lithological Kitakami and the western Tethys is resulted from the location of features, conodonts and ammonoids. Fossil Record, 17: 41-57. the South Kitakami during the Early Triassic, which might be Hyatt A (1884) Genera of fossil cephalopods. Proc Boston Soc Natur Hist, 22: 253-338. situated in the low-latitude region of the Tethys-Panthalassa border Hyatt A (1900) Cephalopoda. In: Zittel KA von (ed), Textbook of being influenced by the potential current from the western Tethys, Paleontology (translated and edited by C. R. Eastman), 1, 502-604, as well as that from the eastern Panthalassa. When the faunal Macmillan, London. relationship of the araxoceratid fauna between the South Kitakami Iranian-Japanese Research Group (1981) The Permian and the Lower Triassic Systems in Abadeh Region, Central Iran. 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要 旨
南部北上帯産のウーチャーピンジアン期(後期ペルム紀)のアラクソセラス科のアンモノイド 2 種,Vedioceras sp. および Urartoceras sp., を記載した.アラクソセラス科のアンモノイドはテチス地域,テチス-パンサラッ サ境界地帯およびパンサラッサ東部域などの低緯度地帯に広く分布した熱帯性アンモノイドである.既知の Araxoceras cf. rotoides, A. sp., Dzhulfoceras cf. furnishi, D. sp, Vescotoceras japonicum, V. sp. および Eusanyangites cf. bandoi を含めて,南部北上帯のウーチャーピンジアン期アラクソセラス科アンモノイドフォーナは,その属構成 において,テチス西部域のフォーナと強い類似性をもつ.
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