Fourteen species of early Permian (Artinskian and Kungurian) fusulines are described from the upper part of the Nakadaira Formation in the Kamiyasse area, South Kitakami, Japan, correlatable to the upper part of the Sakamotozawa Formation in the type area. Among them, Praeparafusulina pseudojaponica, Juresanella juresanensis, and Juresanella uralensis diagnostic in the Nakadaira Formation are uncommon or absent in seamount-originated limestones of the Permian and Jurassic terranes of Japan, and important paleobiogeographically. Darvasella kitakamiensis sp. nov. is distinguished from the known species of the genus by its more regularly folded septa and the presence of axial fillings. Based on these fusulines, the uppermost part of the Nakadaira Formation is correlated to the Artinskian/Kungurian of Cisuralian, suggesting that the carbonate facies having early and most middle Guadalupian fusulines is not developed in the Kamiyasse area, as well as probably throughout the southern Kitakami.
Introduction
The standard succession of the Permian System of the South Kitakami Terrane (Belt) is divided into the Sakamotozawa, Kanokura, and Toyoma formations, corresponding to the Cisuralian, Guadalupian, and Lopingian. The comprehensive chronostratigraphic divisions of the Permian South Kitakami are the result of the areal lithostratigraphic subdivision and correlation, and cross-referencing by index fossils of foraminifers mostly of fusulines, ammonoids, corals, and brachiopods (Minato et al., 1954; Kanmera and Mikami, 1965b; Onuki, 1969; Tazawa, 1976; Kawamura et al., 1990; Kobayashi, 2002; Shiino et al., 2011).
Among the three, the Sakamotozawa Formation is designated as the stratotype of the lower Permian of Japan based on prolific occurrences of fusulines in the Sakamotozawa–Nagaiwa (Hikoroichi) area (Kanmera and Mikami, 1965b). The formation unconformably overlying the upper Carboniferous (Bashkirian to lower Moscovian) Nagaiwa Formation is divided into the lower subformation and upper subformation. Biostratigraphically, the former is subdivided into the lower Zellia nunosei Zone and the upper Monodiexodina langsonensis-Nipponitella explicata Zone, and the latter, from lower to upper, into the Pseudofusulina vulgaris, P. fusiformis, and P. ambigua zones. The upper subformation is conformably overlain by siliciclastic rocks possibly referable to the lower part of the Kanokura Formation (Kanmera and Mikami, 1965a, b). The upper boundary of the Sakamotozawa Formation is biostratigraphically correlated approximately to the upper Kungurian (top of the Cisuralian) based on the occurrence of Misellina species from the uppermost part of the formation in the Hikoroichi area (Ueno et al., 2009) and from the Setamai-Yahagi area (Murata, 1971; Choi, 1972, 1973). On the other hand, fusuline biostratigraphic subdivision and correlation of the Kanokura and its corresponding formations such as the Kamiyasse Formation are disputable in relation to the stratigraphic level (levels) of remarkable sandstone containing Parafusulina matsubaishi Fujimoto, 1956 (= Monodiexodina sutchanica Dutkevich in Likharev, 1939) variably settled by authors (e.g. Morikawa, 1960; Choi, 1973; Misaki and Ehiro, 2004; Kobayashi et al., 2009; Shiino et al., 2011).
This paper shows the absence of the carbonate facies having early and most middle Guadalupian fusulines in the Kamiyasse area based on the examination of fusuline faunas of the upper part of the Nakadaira Formation corresponding to that of the Sakamotozawa Formation in the type area. Fourteen species including Darvasella kitakamiensis sp. nov. are described systematically. Some of these species are age-diagnostic and important paleobiogeographically. They are uncommon or absent in sea-mount-originated limestones in the Permian and Jurassic terranes of Japan. All the thin sections studied herein are stored in the collection are the Museum of Nature and Human Activities, Hyogo, Japan (Fumio Kobayashi Collection, MNHAH).
Figure 1.
Chronostratigraphic subdivision and fusuline zonation of the Cisuralian and Guadalupian in the Tethyan Realm, and stratigraphy of Permian formations of the South Kitakami.
The Cisuralian/Guadalupian boundary, correlation of three stages of the International (Artinskian, Kungurian, and Roadian) vs. Tethyan (Yakhtashian, Bolorian, and Kubergandian) are somewhat different among Leven (2009), Henderson et al. (2012), Davydov et al. (2013) and Kobayashi (2019), as well as the subdivision and correlation of the Guadalupian. In this paper, they follow those of Leven (2009) with slight modifications (Figure 1) and are almost the same as those of Kobayashi (2019) based on the fusuline biostratigraphy of the Akiyoshi Limestone. In this paper, the Bolorian/Kubergandian boundary is drawn at the base of the Misellina ovalis Zone, and the Cisuralian/Guadalupian boundary is fixed between the M. ovalis and Cancellina cutalensis zones as in Leven (2009). The base of the Midian is settled at the level lower than that of the Capitanian in this paper, unlike Kobayashi (2019).
Stratigraphy and samples
Lithostratigraphic subdivision and nomenclature, thickness, and correlation of the Permian are more or less different in the Kamiyasse area among authors due to remarkable lateral changes of lithologic features (Kambe and Shimazu, 1961; Tazawa, 1973; Misaki and Ehiro, 2004; Shiino et al., 2008, 2011). According to Misaki and Ehiro (2004) and Shiino et al. (2011), the Permian strata of the area are divided into Nakadaira, Hoso-o, Kamiyasse, and Kurosawa formations in ascending order (Figure 1). General lithology and thickness of these four formations are lenticular limestone intercalated in sandstone 300 m thick, mudstone 100 to 400 m thick, alternating fossiliferous limestone and sandstone 150 to 250 m thick, and massive black mudstone over 1,000 m thick, respectively, according to Misaki and Ehiro (2004).
Limestones of the Nakadaira Formation consist of fossiliferous grainstone, packstone, grainstone/packstone, and are more or less deformed and recrystallized. They contain various kinds of fossils such as fusulines, crinoids, algae, corals, bryozoans, sponges, brachiopods, and gastropods. Tazawa (1973, 1976) reported more than ten species of fusulines such as Robustoschwagerina schellwieni (Hanzawa, 1939), Chalaroschwagerina vulgaris (Schellwien and Dyhrenfurth, 1909), Pseudofusulina fusiformis (Schellwien and Dyhrenfurth, 1909), and Acervoschwagerina sp. Most of them are common in those described by Kanmera and Mikami (1965b) from the upper subformation of the Sakamotozawa Formations in the type area.
Parafusulina motoyoshiensis (Morikawa, 1960) by Misaki and Ehiro (2004) from the upper part of the Nakadaira Formation is doubtful in their identification. It is the zonal species of the lower part of the Midian Kamiyasse Formation (Kobayashi et al., 2009). Likewise, their identification with Pseudofusulina kraffti (Schellwien and Dyhrenfurth, 1909) and Pseudofusulina fusiformis from the Kamiyasse Formation is highly problematic, since these two species are confined to the upper part of the Yakhtashian in Japan and Tethyan regions.
The occurrence of “limestone” in the Hoso-o Formation is restricted to thin lenticular beds of “limestone”, a few of which occur Pseudofusulina? sp. and Pseudodoliolina sp. according to Misaki and Ehiro (2004). On the other hand, limestone pebbles and cobbles within calcareous conglomerate that corresponds to the “limestone” by Misaki and Ehiro (see Shiino et al., 2008, p. 201, line 13–16 in the right column), contain many fusulines such as Sumatrina cf. annae Volz, 1904, Pseudodoliolina pseudolepida (Deprat, 1912), and Chusenella sinensis Sheng, 1963, suggesting early Midian in age (Shiino et al., 2008). Limestone sensu stricto is almost absent in the Hoso-o Formation according to the Shiino's fieldwork done in the 2000s (see Kobayashi et al., 2009, figs. 2, 3; Shiino et al., 2011, fig. 4). Based on eight species of ammonoids from black mudstone, in addition to Pseudofusulina? sp. and Pseudodoliolina sp. from “arenaceous limestone” and “conglomeratic limestone”, Misaki and Ehiro (2004) assigned the Hoso-o Formation to late Cisuralian to early Guadalupian.
For the purpose of ascertaining of the age of the upper part of the Nakadaira Formation, 14 limestone samples were collected near Hoso-o (Figure 2). Among them, seven samples (H-1, 2A, 2B, 3–6) were from three limestone beds along the ridge north of Ishi-sawa. These beds are less than 10 m thick and intercalated in siliciclastic rocks (Figure 3). They are referred to the upper to uppermost limestones of the formation, so far as exposed along the ridge north of lower stream of Ishi-sawa.
Seven limestone float samples (H-7, 8A, 8B, 9–12) were also collected along the riverside slope south of localities of seven samples along the ridge, because two float limestones containing large schwagerinids (Darvasella kitakamiensis sp. nov. and Schwagerinidae gen. et sp. indet.), not recognized along the ridge, were discovered. These limestone float samples are assumed to be derived from limestones stratigraphically equivalent to the seven of those collected along the ridge. A possible derivation of these float samples from the overlying formations should be excluded, since (1) the limestone sensu stricto is not discovered from the Hoso-o Formation, (2) limestone float rapidly disappears in the upper streamside entering into the distribution area of the Hoso-o Formation, and (3) fusulines all contained in these float samples are coeval with those of the upper part of the Sakamotozawa Formation in the type area.
Lithologies of these 14 samples are H-1: crinoidal fusuline packstone, H-2A: crinoidal bioclastic grainstone, H-2B: bioclastic grainstone/packstone, H-3: crinoidal algal packstone/grainstone, H-4: crinoidal algal packstone, H-5: bioclastic packstone/wackestone, H-6: algal crinoidal fusuline grainstone, H-7: bioclastic packstone, H-8A: fusuline bioclastic grainstone, H-8B: bioclastic grainstone, H-9: algal packstone, H-10: fusuline bioclastic grainstone, H-11: crinoidal bioclastic grainstone, and H-12: bioclastic packstone. Foraminifers contained in 12 samples are shown in Figure 4.
Faunal analysis and correlation
Many age-diagnostic species are newly recognized from the upper part of the Nakadaira Formation. They are Pamirina darvasica Leven, 1970; Cuniculinella globosaeformis (Leven, 1967); Praeparafusulina pseudojaponica (Dutkevich in Likharev, 1939; Juresanella juresanensis (Rauzer-Chernousova, 1940); J. uralensis (Rauzer-Cherousova, 1949b); Concavutella vissarionovae (Rauzer-Cherousova, 1949b); Pseudofusulina solida (Schellwien, 1908); and Darvasella kitakamiensis sp. nov. (Figure 4). As described in the next section, the named species among them were previously established on the basis of the materials from the South Urals (fourth to seventh species), Darvas (P. darvasica), southeast Pamir (C. globosaeformis), and North China (P. pseudojaponica). Ages of these fusulines are confined to Artinskian and Kungurian, corresponding to Yakhtashian, Bolorian, and early Kubergandian in the Tethyan standard sequence (Figure 1). Darvasella vulgariformis (Kalmykova, 1960), allied to D. kitakamiensis, is known from the Artinskian of Darvas (Kalmykova, 1960, 1967) and southeast Pamir (Leven, 1967).
Figure 2.
Geological map of the Kamiyasse area modified from Kobayashi et al. (2009) and limestone sample localities (H-1 to 12) of the Nakadaira Formation near Hoso-o. Fossil locality of the Hoso-o Formation by Shiino et al. (2008) is shown by a star.
Accordingly, age of the uppermost part of the Nakadaira Formation is estimated as old as early Kubergandian, and is coeval with the uppermost part of the Sakamotozawa Formation in the type area. However, species of Misellina, reported from the type area (Ueno et al., 2009) and the Setamai-Yahagi area (Murata, 1971; Choi, 1973), were not detected in the present material. The occurrence of Darvasella, Juresanella, and Concavutella indigenous to the South Kitakami Terrane, is rare or absent in coeval limestones in the Permian and Jurassic accretionary terranes of Japan. These schwagerinids are important paleobiogeographically and paleoenvironmentally along with Nipponitella and highly slender fusulines [e.g. “Monodiexodina (Ferganites) langsonensis” (Saurin, 1950) and “Rugosofusullina alpina” (Schellwien, 1898)] from the lower part of the Sakamotozawa Formation (Kanmera and Mikami, 1965b), and Monodiexodina sutchanica from the Kamiyasse Formation (Kobayashi et al., 2009). M. sutchanica has special paleobiogeographic and paleoecological implications on account of its antitropical distribution and its strong facies dependence (Ueno, 2006). This species is densely concentrated as lag deposits showing hummocky cross stratification with a few pebbles on the swaley erosive surfaces in the basal part of the Kamiyasse Formation (Shiino et al., 2011). Both Nipponitella and Monodiexodina have not been reported from seamount-originated limestones in Japan.
Figure 3.
Columnar section of the upper part of the Nakadaira Formation near Hoso-o, showing the stratigraphic levels of seven samples.
Shiino et al. (2008) showed the probable absence of early and most middle Guadalupian fusulines in the Kamiyasse area based on two reasons. One was the lithostratigraphy and occurrence of late Guadalupian fusulines (Sumatrina cf. annae and Pseudodoliolina pseudolepida, in association with Chusenella sinensis) from the upper part of the Hoso-o Formation correlatable to the middle to upper part of the Kanokura Formation in the Setamai-Yahagi area (Figure 1). The other was little biostratigraphic significance of Monodiexodina sutchanica due to the strong facies dependence. Moreover, Kobayashi et al. (2009) supposed that the occurrences of early Guadalupian neoschwagerinids that had been reported from the South Kitakami by previous workers without description and illustrations are doubtful, as exemplified by Wutuella sp. This unnamed species from the Kamiyasse Formation (Kobayashi et al., 2009) is conspecific with a small specimen that was misidentified by Choi (1970) as “Cancellina” sp. from the lower part of the Kamiyasse Formation in the Imo-sawa area neighboring the Kamiyasse. The occurrence of Cancellina is restricted to the lower Guadalupian throughout the world. In contrast to – better wording?? the dominant to common occurrence of limestone in the Nakadaira (Sakamotozawa) and Kamiyasse (upper part of the Kanokura) formations, the limestone having early and most of middle Guadalupian fusulines is absent in the Hoso-o Formation by comprehensively considering the lithologic and fusuline biostratigraphic elements shown in Misaki and Ehiro (2004), Shiino et al. (2008), and Kobayashi et al. (2009).
The carbonate facies having early and middle Guadalupian fusulines is considered to be not developed not only in the Kamiyasse area but also throughout South Kitakami, where almost continuous deposition of siliciclastic rocks from the upper Cisuralian to middle Guadalupian has been confirmed. The presence or absence of limestone might be related to the tectonic setting of the ancient South Kitakami and/or global historical changes of sea-level fluctuations during the Permian.
Nine taxa of non-fusuline foramainifers were recognized in 11 samples (Figure 4). They are less diversified than those of the Asselian and of Wordian to Changhsingian. Climacammina valvulinoides Lange, 1925 is not age-diagnostic because of common occurrence from the Moscovian to Guadalupian. Others are unnamed due to insufficient number and few well-oriented specimens. Among the nine taxa, two genera, Pachyphloia and Agathammina are confined to the middle Cisuralian to Lopingian.
Description of species
Superfamily Fusulinoidea von Möller, 1878
Family Ozawinellidae Thompson and Foster, 1937
Genus Pamirina Leven, 1970 emend. Kobayashi, 1977
Type species.—Pamirina darvasica Leven, 1970.
Pamirina darvasica Leven, 1970
Figure 5.1
Pamirina darvasica Leven, 1970, p. 23, 24, pl. 1, figs.1–9, 23, 24; Kobayashi, 1977, p. 14, 15, pl. 2, figs. 1–3; Igo et al., 1993, p. 20, 23, 24, figs. 3.1–3.9, 4.1–4.33.
Remarks.—Broad morphological variations of this species were shown by Igo et al. (1993) in which the genus and this species were reviewed and discussed. The Kamiyasse specimens, though well-oriented specimens are few, are certainly identified with Pamirna darvasica.
Family Schubertellidae Skinner, 1931b
Subfamily Boultoniinae Skinner and Wilde, 1954
Genus Minojapanella Fujimoto and Kanuma, 1953
Type species.—Minojapanella elongata Fujimoto and Kanuma, 1953.
Figure 5.
Fusulines from the Nakadaira Formation (1). 1, Pamirina darvasica Leven, D2-038826, H-10; 2, Minojapanella elongata Fujimoto and Kanuma, D2-038741, H-3; 3–6, Darvasites minatoi (Kanmera and Mikami), 3, D2-038782, H-6; 4, D2-038768, H-4; 5, D2-038725, H-1; 6, D2-038767, H-4; 7–9, Praeskinnerella sp., H-10; 7, D2-038813; 8, D2-038831; 9, D2-038838; 10, 17, Darvasella kitakamiensis sp. nov., H-10, Paratypes; 10, D2-038819; 17, D2-038826; 11–14, Juresanella juresanensis (Rauzer-Chernousova), 11, D2-038739, H-2B; 12, D-038726, H-1; 13, D2-038757, H-3; 14, D2-038735, H-2B; 15, 16?, 18–20, Juresanella uralensis (Rauzer-Chernousova), 15, D2-038750, H-3; 16, D2-038725, H-1; 18, D2-038857, H-12; 19, D2-038759, H-3; 20, D2-038755, H-3; 21, Pseudofusulina solida (Schellwien), D2-038771, H-4. Scale bar A of 0.5 mm is for 1, 2; B of 2 mm for 3–21.
Minojapanella elongata Fujimoto and Kanuma, 1953
Figure 5.2
Minojapanella elongata Fujimoto and Kanuma, 1953, p. 152, pl. 19, figs. 1–11; Kanmera and Mikami, 1965b, p. 280, 281, pl. 45, fig. 10, pl. 48, fig. 16; Choi, 1973, p. 14, 15, pl. 1, figs. 8–11; Tazawa, 1976, pl. 1, figs. 1, 2; Ueno et al., 2009, p. 41, figs. 6.6, 6.7.
Remarks.—Minojapanella elongata was established from the Mino Terrane, central Japan. The specimens referable to this species are also described and illustrated by many workers from the Southern Kitakami Terrane. As well as them, the illustrated and some other specimens are identified with this species. They are not assignable to Wutuella but to Minojapanellla due to their smaller test with fewer whorls, and more weakly folded septa.
Family Schwagerinidae Dunbar and Henbest, 1930
In this family, diagnostic characters of some genera and their differences from those of similar genus (genera), and stratigraphic distribution of them on occasions are briefly summarized, since some genera are assigned to pseudofusulinids and their allies that have been proposed recently, are uncommon and/or have not been reported from Japan.
Genus Concavutella Bensh, 1987
Type species.—Pseudofusulina? concavutus Vissarionova, 1937.
Remarks.—The genus is distinguished from Pseudofusulina by its concave periphery and protruding poles of inner and middle whorls of the test, smaller proloculus, and more regularly folded septa.
Concavutella vissarionovae (Rauzer-Chernousova, 1949b)
Figures 8.14–8.18
Pseudofusulina? vissarionovae Rauzer-Chernousova, 1949b, p. 155, 156, pl. 10, figs. 3, 4; Grozdilova and Lebedeva, 1961, p. 242, 243, pl. 19, fig. 5, pl. 20, fig. 1.
Remarks.—This species questionably assigned to Pseudofusulina was originally described by Rauzer-Chernousova (1949b) from the Irgina Horizon (Irginian substage) of the middle Artinskian in the Preurals (Rauzer-Chernousova, 1949a, b). It is characterized by a large, elongate fusiform test with more or less concave periphery in outer few whorls, regularly arranged septal loops, some of which are in contact with the roof of chamber, and distinct axial fillings. Two specimens identified with this species by Grozdilova and Lebedeva (1961) from the lower Artinskian of Timan have a more concave periphery than the types. Although test size is obscure due to abrasion of outer test, the illustrated five specimens herein are included in this species by their common characters such as size of proloculus, tightly coiled initial whorl(s) with thin wall, and the mode of septal folding to that of the types. However the degree of concavity of the periphery of the test is not prominent as in the Russian specimens.
Genus Cuniculinella Skinner and Wilde, 1965
Type species.—Cuniculinella tumida Skinner and Wilde, 1965.
Junior synonym.—Chalaroschwagerina (Cuniculina) Leven in Leven and Mohaddam, 2004 (type, Parafusulina? vulgarisiformis Morikawa, 1952).
Remarks.—Leven in Leven and Mohaddam (2004) proposed a new subgenus Cuniculina for forms attributed to the genus Chalaroschwagerina from the Tethyan regions and distinguished them from Chalaroschwagerina (Chalaroschwagerina) by the presence of cuniculi. Cuniculina might be better considered as congeneric with Cuniculinella rather than with an independent subgenus of Chalaroschwagerina established by Skinner and Wilde (1965).
Cuniculinella globosaeformis (Leven, 1967)
Figures 7.9, 7.10
Parafusulina globosaeformis Leven, 1967, p. 176, 177, pl. 27, figs. 2, 3, 5.
Chalaroschwagerina (Cuniculina) globosaeformis (Leven). Leven in Leven and Mohaddam, 2004, p. 452, pl. 2, fig. 7.
Remarks.—Morphologic features of the test are similar to both Cuniculinella globosaeformis and Cuniculinella vulgarisiformis. By having more irregularly folded septa, the former might be distinguished from the latter. The present specimens are identified with the former originally described by Leven (1967) from the Yakhtashian of southeast Pamir, and the subsequent ones from the Bolorian of eastern Iran by Leven in Leven and Mohaddam (2004).
Genus Darvasella Leven, 1992
Type species.—Rugosofusulina vulgariformis Kalmykova, 1960.
Remarks.—The genus is clearly distinguished from Eoparafusulina by its larger test with larger proloculus, thicker and more or less undulated wall, and not so regularly folded septa.
Figure 6.
Fusulines from the Nakadaira Formation (2). 1–11, Darvasella kitakamiensis sp. nov., 1, H-8A; 2–11, H-10; 4, Holotype; 1–3, 5–11, Paratypes; 1, D2-038800; 2, D2-038812; 3, D2-038815; 4, D2-038825; 5, D2-038823; 6, D2-038828; 7, D2-038816; 8, D2-038817; 9, D2-038834; 10, D2-038827; 11, D2-038821. Scale bar of 2 mm for all.
Figure 7.
Fusulines from the Nakadaira Formation (3). 1, 2, 8, “Leeina” kraffti (Schellwien and Dyhrenfurth), 1, D2-038744, H-3; 2, D2-038844, H-11; 8, D2-038727, H-1; 3–7, Darvasella kitakamiensis sp. nov., H-10, Paratypes; 3, D2-038835; 4, D2-038836; 5, D2-038829; 6, D2-038832; 7, D2-038837; 9, 10, Cuniculinella globosaeformis (Leven), H-12; 9, D2-038847; 10, D2-038852; 11, Schwagerinidae gen. et sp. indet., D2-038833, H-10. Scale bar of 4 mm for all.
Figure 8.
Fusulines from the Nakadaira Formation (4). 1–7, Praeparafusulina pseudojaponica (Dutkevich), 1, D2-038789, H-6; 2, D2-038740, H-3; 3, D2-038788, H-6; 4, D2-038792, H-6; 5, D2-038752, H-3; 6, D2-038745, H-3; 7, D2-038742, H-3; 8, 9, Leeina? sp., 8, D2-038846, H-12; 9, D2-038776, H-6; 10–13, Sakmarella sp., 10, D2-038785, H-6; 11, D2-038762, H-4; 12, D2-038749, H-3; 13, D2-038754, H-3; 14–18, Concavutella vissarionovae (Rauzer-Chernousova), 14, D2-038747, H-3; 15, D2-038855, H-12; 16, D2-038780, H-6; 17, D2-038854, H-12; 18, D2-038743, H-3. Scale bar of 2 mm for all.
Darvasella kitakamiensis sp. nov.
Figures 5.10, 5.17, 6.1–6.11, 7.3–7.7
Pseudofusulina fusiformis (Schellwien and Dyhrenfurth, 1909). Kanmera and Mikami, 1965b, p. 301, 302, pl. 52, figs. 1–6; par Choi, 1973, p. 46, 47, pl. 9, figs. 1, 2, non pl. 9, fig. 3 and pl. 11, fig. 4 (other species of the genus).
Chusenella sp. Ueno et al., 2009, p. 43, fig. 9.4.
Pseudofusulina dzamantalensis (Leven, 1967). par Ueno et al., 2009, p. 50, 51, fig. 9.5, figs. 8.1–8.4 (questionable).
Darvasella sp. Ueno et al., 2009, p. 54, 56, figs. 7.9, 7.10.
Etymology.—From the southern part of Kitakami Mountains.
Type specimens.—Holotype D2-038825 (axial section, Figure 6.4). Paratypes: ten axial, four sagittal, and three tangential sections. Their register numbers are shown in the explanation of Figures 5–7.
Type locality.—Northern riverside slope 310 m east of the entrance of Ishi-sawa flowing into the Yasse River, near Hoso-o, Kamiyasse area, northern part of Kesennuma City, Miyagi Prefecture.
Diagnosis.—Elongate fusiform to subcylindrical test with gently undulated wall thinner in inner and thicker in outer whorls. Septa rather regularly and intensely folded in polar regions and weakly in the median part of the test. Tunnel path irregular and axial fillings developed moderately to intensely.
Description.—Test elongate fusiform to subcylindrical in shape with straight to irregularly undulated periphery, and rounded poles. Axis of coiling almost straight to slightly curved. Mature test consists of six to seven whorls, about 9.8 to 13.5 mm in length, about 3.4 to 4.4? mm in width, and about 2.7? to 3.7 in form ratio.
Proloculus spherical to subspherical, and 0.39 to 0.56 mm in longer diameter. The first whorl is subspherical to inflated fusiform and is succeeded by outer whorls increasing their form ratio. Degree of the test expansion is variable among specimens. It is more or less variable depending on the orientation of axial section. From the first to the seventh whorls of the holotype, approximate length is 0.81, 2.15, 3.53, 5.30, 7.64, 9.93, and 11.8? mm, and width is 0.56, 0.86, 1.24, 1.90, 2.68, 3.55, and 4.4? mm.
Wall gently undulated and the degree of undulation is variable among specimens. It is thin and consists of a tectum and thin translucent layer in the first whorl, gradually thickened and of a tectum and alveolar keriotheca in the succeeding one to two whorls. In further outer few whorls, wall attains to 0.1 to 0.2 mm in the thickest part and accompanies thin, discontinuous layer comparable to lower tectorium in some specimens.
Septa rather regularly and intensely folded in polar regions and weakly in the median part of the test. Septal counts from the first to the sixth whorls 8 to 10, 13 to 17, 18 to 22, 22 to 24, 23 to 26, and 25 to 30. Phrenotheca distinct in some specimens. Tunnel one half as high as chambers in outer whorls. Its path irregular and not straight. Rudimentary chomata present on proloculus and in inner few whorls. Axial fillings developed moderately to intensely.
Remarks.—This new species differs from the type species of the genus, Darvasella vulgariformis originally attributed to Rugosofusulina and described by Kalmykova (1960, 1967) from the Yakhtashian of Darvas and subsequently by Leven (1967) from the Artinskian of southeast Pamir in its more regularly folded septa and the presence of axial fillings. It is distinguished from Darvasella cucumeriformis proposed by Leven (1997) from the Yakhtashian of northern Afghanistan in its less concave periphery of the test, more regularly folded septa, and the presence of axial fillings. Pseudofusulina dzamantalensis originally assigned to Parafusulina and described by Leven (1967) from the Kubergandian of southeast Pamir has a thinner and not so clearly undulated wall as this new species.
Among the described species from the Sakamotozawa Formation, those identified with Pseudofusulina fusiformis by Kanmera and Mikami (1965b) and a part with those by Choi (1973), as listed above, are assumed to be reassigned to Darvasella kitakamiensis. Likewise, Darvasella sp., Chusenella sp., and one among five identified with Pseudofusulina dzamantalensis, all described by Ueno et al. (2009), might be also reassigned to the present new species based on their undulated thick wall and other test characters. Remaining four among five by Ueno et al. (2009) are different from the types of Leven (1967) in their corrugated wall and not so regularly folded septa. Though their wall is thinner, they are possibly reassigned to this new species because of similarities of the size and shape of the test and proloculus, mode of septal folding, and development of axial fillings.
Occurrence.—Abundant in the fusuline bioclastic grainstone (H-8A, H-10) of the upper part of the Nakadaira Formation in the Kamiyasse area, and probably common in the upper part of the Sakamotozawa Formation in the Hikoroichi and Setamai-Yahagi areas.
Genus Darvasites Miklukho-Maklay, 1959
Type species.—Triticites ordinatus var. daroni Miklukho-Maklay, 1949.
Remarks.—Distribution of the genus Nagatoella is almost confined to the Akiyoshi Terrane in Japan. Schwagerinids assigned to Nagatoella and described from the Jurassic and South Kitakami terranes are reassigned to Darvasites by their smaller test with fewer whorls. In my opinion, Darvasites (Alpites) Davydov in Davydov et al., 2013 is a junior synonym of Darvasites even at the sub-generic level.
Darvasites minatoi (Kanmera and Mikami, 1965b)
Figures 5.3–5.6
Nagatoella minatoi Kanmera and Mikami, 1965b, p. 307, 308, pl. 50, figs. 9–11, pl. 53, figs. 7–9; Choi, 1973, p. 29, pl. 7, fig. 6, pl. 12, figs. 1–8.
Darvasites minatoi (Kanmera and Mikami). Ueno et al., 2009, p. 45, 46, figs. 6.12, 6.13.
Remarks.—This species is characterized by ellipsoidal test with broadly rounded poles, tightly coiled inner whorls, regularly folded septa, straight tunnel bordered by distinct chomata. Based on these morphologic features, Kanmera and Mikami (1965b) assigned this species to Nagatoella. However, the test is smaller, the number of whorls is fewer than those of Nagatoella, and axial fillings are less developed to almost absent in this species. These morphologic features suggest that this species should be reassigned to Darvasites very characteristic of the Sakmarian, Yakhtashian, and Bolorian in the Tethyan regions.
The Kamiyasse specimens have smaller test, thinner wall, and weaker chomata than the types. However, they are identical with Darvasites minatoi, as these slight differences are supposed to be ascribed to morphologic variations of this species. This species is easily distinguished from Darvasites ikenoensis (Morikawa and Isomi, 1961) described by Kobayashi in Kobayashi and Furutani (2009) from the western part of Mt. Ryozen in the Mino Terrane by its larger test, and more intensely and more regularly folded septa.
Genus Juresanella Bensh, 1987
Type species.—Pseudofusulina juresanensis Rauzer-Chernousova, 1940.
Remarks.—The genus is distinguished from Pseudofusulina by its more slender test having tightly coiled inner whorls with thin wall and from Monodiexodina by its not so regularly folded septa with higher septal loops.
Juresanella juresanensis Rauzer-Chernousova, 1940
Figures 5.11–5.14
Pseudofusulina juresanensis Rauzer-Chernousova, 1940, p. 91, 96, pl. 6, figs. 3–7.
Remarks.—More elongate and slender specimens than other pseudofusulinids, though exact test size is uncertain due to abrasion of outer whorl(s), were recognized in Sample H-1, H-2B, and H-3. Based on their morphologic similarities, they are identified with Juresanella juresanensis that was assigned to Pseudofusulina and described from the Artinskian Burtsev and Irgina horizons of the Ufa Plateau by Rauzer-Chernousova (1940). The Kamiyasse specimens are more than 8.5 mm in length and about 2 mm in width, consisting of 6 to 6.5 whorls slowly expanding outward, pointed to sharply pointed poles except for broadly rounded pole in the final whorl. Wall is very thin, and structureless or with indistinct alveolar keriotheca in inner whorls. Moreover, they are characterized by thin septa moderately folded and weak to supplementary axial fillings in inner whorls, and indistinct chamata. Considerable variations are recognized in the illustrated four specimens of the Russian types as well as in the Kamiyasse specimens. Axial fillings are better developed generally in the present ones.
This species closely resembles Juresanella lutugini (Schellwien, 1908) and Juresanella forakerensis (Skinner, 1931a) in many respects. However, it is distinguished from the former, originally assigned to Fusulina by Schellwien (1908), by smaller test and more irregular and weaker septal folding. The latter was described as “Fusulina” forakerensis from the upper Pennsylvanian Foraker limestone of northern Oklahoma (Skinner, 1931a). In addition to a larger test, J. forakerensis is distinguished from this species by its straight and wider tunnel, and distinct and massive chomata that are obscure in the latter.
Juresanella uralensis Rauzer-Chernousova, 1949b
Figures 5.15, 5.16?, 5.18–5.20
Pseudofusulina forakerensis var. uralensis Rauzer-Chernousova, 1949b, p. 143, pl. 7, figs. 4, 5.
Remarks.—The present material is characterized by its elongate fusiform test consisting of tightly coiled inner whorls with acutely pointed poles and thinner wall, rather regularly expanding outer whorls with thicker wall and bluntly pointed poles in outer whorls, and regularly folded septa throughout the test. These features are closely similar to those of Juresanella uralensis proposed by Rauzer-Chernousova (1949b) from the upper Artinskian (Burtsev to Sargin horizons) of the Cisurals (Rauzer-Chernousova, 1949a). Those are also commonly found in Juresanella forakerensis (Skinner, 1931a). However, the tunnel is much wider and chomata in inner whorls are more massive in the Oklahoma species.
This species is different from Pseudofusulin solida, described below, by its smaller proloculus and tightly coiled inner whorls. It is distinguished from elongate forms of “Pseudofusulina” blochini proposed by Korzhenevski (1940) based on the Sakmarian core samples of the Ishimbayevo oil field in the South Urals by its more elongate test with more acutely pointed poles in inner whorls and more intensely folded septa.
Genus Leeina Galloway, 1933
Type species.—Fusulina vulgaris var. fusiformis Schellwien and Dyhrenfurth, 1909.
Remarks.—Many taxonomic problems of Schwagerinidae had long been left uncertain as exemplified by Pseudofusulina and its similar Leena, both of which were considered synonymous with Schwagerina by Dunbar and Skinner in 1937 who established the genus Pseudofusulina in 1931. Generic definition and classification of fusiform schwagerinids are varied among authors even after Bensh (1987) who advocated her original ideas for the taxonomic revision of pseudofusulinids. Although Pseudofusulina and Leeina might be congeneric, Leeina is treated as an independent genus herein because of considerable morphologic differences of the type species. That is, septal folding is weaker in the type species of Leeina than in that of Pseudofusulina, P. huecoensis Dunbar and Skinner, 1931, and prenotheca is not recognized in the former.
“Leeina” kraffti (Schellwien and Dyhrenfurth, 1909)
Figures 7.1, 7.2, 7.8
Fusulina kraffti Schellwien and Dyhrenfurth, 1909, p. 169, pl. 13, figs. 1–6, pl. 16, figs. 1–9.
Pseudofusulina kraffti kraffti (Schellwien and Dyhrenfurth). Kanmera and Mikami, 1965b, p. 300, 301, pl. 44, fig. 7.
Pseudofusulina kraffti (Schellwien and Dyhrenfurth). Tazawa, 1976, pl. 1, fig. 7.
Leeina kraffti (Schellwien and Dyhrenfurth). Leven, 2009, p. 138, pl. 22, fig. 3.
Remarks.—Short subcylindrical test with straight to concave periphery and broadly rounded poles, and dense axial fillings are characteristic of the present specimens. From these characters, illustrated specimens are identified with Fusulina kraffti from Darvas (Schellwien and Dyhrenfurth, 1909). Specimens referable to the types have been reassigned to Pseudofusulina by many workers from Japan and elsewhere (e.g. Leven, 1967, 1997) including those of Kanmera and Mikami (1965b) and Tazawa (1976) from the South Kitakami. In this paper, however, this species is tentatively reassigned to Leeina as proposed by Leven (2009).
Genus Praeparafusulina Tumanskaya, 1962
Type species.—Parafusulina pseudojaponica Dutkevich in Likharev, 1939.
Remarks.—The genus is assumed to be proposed mainly on the basis of its lower stratigraphic occurrence and smaller size of the type species than those of Parafusulina japonica (Gümbel, 1874). It is adopted herein as a genus characterized by having a more inflated fusiform test than other parafusulinids.
Praeparafusulina pseudojaponica (Dutkevich in Likharev, 1939)
Figures 8.1–8.7
Schellwienia japonica (Gümbel, 1874). Lee, 1927, p. 82, pl. 13, figs. 1–3.
Parafusulina pseudojaponica Dutkevich in Likharev, 1939, p. 43, pl. 5, figs. 4–6 (= Schellwienia japonica pl. 13, figs. 1–3 by Lee, 1927); Kalmykova, 1967, p. 206, pl. 24, figs. 1–5.
Parafusulina japonica (Gümbel). Kalmykova, 1967, p. 206, 208, pl. 25, figs. 1–4.
Remarks.—Dutkevich in Likharev (1939) gave a new species name, pseudojaponica for three specimens among eight described by Lee (1927) as Schellwienia japonica from the Fuching Limestone, south Chihli, North China. These three specimens are considerably different from the topotypes of Parafusulina japonica from the Akasaka Limestone (Kobayashi, 2011). Parafusulina pseudojaponica was designated as the type species of Praeparafusulina later proposed by Tumanskaya (1962). This species is distinguished from Parafusulina japonica by its shorter fusiform test, smaller length and width in corresponding whorls, and more regularly folded septa, even considering broad morphologic variations of the topotypes of P. japonica. Kalmykova (1967) recognized the development of cuniculi in “Parafusulina” pseudojaponica from the Sakmarian of Darvas, which is supposed to be conspecific with Parafusulina japonica described by Kalmykova (1967) from the lower part of the Darvasian (probably Yakhtashian) of Darvas.
The Kamiyasse specimens closely resemble those from North China and Darvas in many respects, and are surely identified with them. The presence of cuniculi was also ascertained in the present specimens. They are named as Praeparafusulina pseudojaponica and apparently distinguished from Parafusulina japonica by their smaller test and proloculus, and smaller length and width of the corresponding whorls.
Pseudofusulina aff. japonica described from the upper subformation of the Sakamotozawa Formation (Kanmera and Mikami, 1965b) somewhat resembles the topotypes from the Akasaka Limestone, but has a much thicker wall in the corresponding whorls, especially in the inner whorls, as suggested by Kanmera and Mikami (1965b). Parafusulina japonica is also distinguished from Praeparafusulina pseudojaponica by its larger test, larger proloculus, and thicker wall. Although detailed comparison is not possible, the single illustrated specimen that was realized to be related to “Pseudofusulina” japonica by Ueno et al. (2009) from the Sakamotozawa Formation might be conspecific with Praeparafusulina pseudojaponica.
Genus Praeskinnerella Bensh, 1991
Praeskinnerella—a new name for the genus Guembelites Bensh, 1987)
Type species.—Schwagerina guembeli Dunbar and Skinner, 1937.
Remarks.—This genus is distinguished from Schwagerina by its fusiform test tapering toward poles with more or less concave lateral slopes. It is thought to be distinct at the generic level in spite of many similarities of other test characters between the two genera.
Praeskinnerella sp.
Figures 5.7–5.9
Remarks.—Schwagerinids in association with Darvasella kitakamiensis are characteristic in the hexagonal-like, elongate fusiform test with straight to slightly concave periphery, concave lateral slopes gently tapering toward poles, and narrowly rounded poles. Inner whorls are tightly coiled against the gradually expanding outer whorls. Septa are intensely and rather regularly folded. Axial fillings are well developed both sides of irregular and not straight tunnel with variable angles, showing x-letter shape in axial and tangential sections.
Among the known genera, these schwagerinids are probably attributed to Praeskinnerella, and among the known species they are more or less similar to Praeskinnerella cushmani (Chen, 1934) originally assigned to Pseudofusulina. However, the present unnamed species is easily distinguished from P. cushmani from South China in its larger test with concave, hexagonal-like middle and outer whorls, and distinct axial fillings. One specimen identified as Praeskinnerella fragilis Leven, 1992 by Ueno et al. (2009) from the Sakamotozawa Formation might be an incomplete specimen referable to this unnamed species, though more comparison cannot be done because of its abrasion of outer whorls. Schwagerina sp. described by Kanmera and Mikami (1965b, p. 306, 307, pl. 52, fig. 7) also from the same formation should be reassigned to Praeskinnerella. It is similar to the present unnamed species, but the latter has more elongate test with much more depressed lateral slopes. The present specimens of Praeskinnerella might be an independent species of the genus. However, this possibility is deferred until more sufficient specimens are accumulated.
Genus Pseudofusulina Dunbar and Skinner, 1931
Type species.—Pseudofusulina huecoensis Dunbar and Skinner, 1931.
Remarks.—As mentioned above, Leeina is treated as independent from Pseudofusulina. On the other hand, Tastubella Bensh and Kireeva in Bensh, 1987, and Kutkanella Bensh, 1987 might be junior synonyms of Pseudofusulina. Because, both “Pseudofusulina” jaroslavkensis Vissarionova, 1937 (designated as the type species of the former) and “Fusulina” verneuili var. solida Schellwien, 1908 (done as that of the latter) are not easily distinguishable from species of Pseudofusulina at the generic level.
An independency of Nonpseudofusulina proposed by Leven (2008) is considered problematic taxonomically and phylogeneticallybecause the Yakhtashian species reassigned to Nonpseudofusulina (Leven, 2008, 2009) such as “Pseudofusulina” immensa Leven, 1997 and “Parafusulina?” dutkevitchi Leven, 1967, as well as the Bolorian species of “Pseudofusulina?” jukunda Leven, 1992, are presumed to be largely different from the type species of Nonpseudofusulina, “Pseudofusulina” blochini Korzhenevski, 1940 of the Sakmarian.
Pseudofusulina solida (Schellwien, 1908)
Figure 5.21
Fusulina verneuili var. solida Schellwien, 1908, p. 177, pl. 20, figs. 11–14.
Pseudofusulina solida (Schellwien). Rauzer-Chernousova, 1949b, p.144, pl. 7, fig. 6; Grozdilova and Lebedeva, 1961, p. 244, pl. 20, fig. 4.
Nonpseudofusulina verneuili solida (Schellwien). Leven, 2009, p. 134, pl. 19, fig. 3.
Remarks.—One axial section illustrated might be identical with the taxon proposed from arctic Russia by Schellwien (1908) as a variety of Fusulina verneuli Möller, 1878 and later treated as an independent species of Pseudofusulina by Rauzer-Chernousova (1949b) and Grozdilova and Lebedeva (1961). It is distinguished from Pseudofusulina paraconcessa Rauzer-Chernousova, 1949b from the Artinskian Irgina Horizon of Cisurals, by its less elongate test. According to Rauzer-Chernousova (1949a, b), this species ranges from the Burtsev Horizon to the Sargina Horizon of the Artinskian of southern Urals. On the other hand, Leven (2009) illustrated the specimen referable to this species from the Sakmarian of Carnic Alps, and reassigned it to the genus Nonpseudofusulina.
Genus Sakmarella Bensh and Kireeva in Bensh, 1987
Type species.—Fusulina mölleri Schellwien, 1908.
Remarks.—Sakmarella is different from Pseudofusulina in its more regularly folded septa with lower septal loops, and generally in thinner wall and absence of or poorly developed axial fillings.
Sakmarella sp.
Figures 8.10–8.13
Remarks.—Among the illustrated pseudofusulinids of the Nakadaira Formation, those of four are different from inflated forms of Concavutella vissarionovae in their thinner septa with lower septal loops, besides not concave to straight but broadly arched periphery. They are somewhat similar to Sakmarella mölleri described by Rauzer-Chernousova (1965) from the lower Sakmarian of southern Urals, but have a more inflated test with more intensely folded septa. Whether Sakmarella extends up to the upper Cisuralian or not is uncertain, large inflated forms of pseudofusulines seem to be inferior in number toward late Cisuralian in the stratotype regions of Urals.
Schwagerinidae gen. et sp. indet.
Figure 7.11
Remarks.—The illustrated parallel section of a large schwagerinid and a few other sections far apart from the center were obtained in sample H-10 in association with Darvasella kitakamiensis, Praeskinnerella sp., and others. They are distinct compared to diagonal sections of Zellia nunosei Hanzawa, 1939 described by Kanmera and Mikami (1965b) from the Sakamotozawa Formation in their larger test with more number of whorls and many more septa. Moreover, they are not attributed to other inflated schwagerinids such as Paraschwagerina in their chamber height not rapidly increasing in outer whorls. Though apart from the center, they are dissimilar to the one specimen questionably assigned to Kubergandella by Ueno et al. (2009) in their larger test and more whorls. The specimen of Ueno et al. (2009) is quite different from the two known species reassigned to Kubergandella by Leven (1992, 2009) in having a much thicker wall of corresponding whorls. In my opinion, it might be better reassigned to Chalaroschwagerina because of its similarity to “Pseudofusulina” vulgaris globosa (Schellwien and Dyhrenfurth, 1909) illustrated by Kanmera and Mikami (1965b) from the Sakamotozawa Formation.
Acknowledgements
I am grateful to Katsumi Ueno (Fukuoka University) and Hiroshi Furutani (Museum of Nature and Human Activities, Hyogo) who read the early version of the manuscript and gave me helpful comments and suggestions. The final version was improved by constructive review of Katsumi Ueno. Yuta Shiino (Niigata University) provided valuable information on the field geology, and Permian stratigraphy and sedimentary facies analysis of the Kamiyasse area, and read the newer version of the manuscript.
