Fusuline biostratigraphy and faunal composition of the upper part the Ichinotani Formation and lower part of the Mizuyagadani Formation in the Fukuji area, central Japan are reexamined and compared to those of previous works. The upper part of the Upper Member of the Ichinotani Formation is composed mainly of the upper Kasimovian and lower Gzhelian strata, and is characterized by the partial reappearance of Moscovian strata dominant in the lower part of the Upper Member, suggesting a more complicated geological structure of the formation than previously assumed. Fusulines apparently correlatable to the middle part of the Kasimovian have not been found in the Fukuji area. The species Carbonoschwagerina morikawai is restricted to the lower part of the Mizuyagadani Formation. Faunal composition and correlation of age-diagnostic fusuline species are reviewed paleobiogeographically between the Fukuji and other areas especially of the Akiyoshi Limestone. Described herein are two species of non-fusuline foraminifers and nine species of fusulines including Montiparus japonicus sp. nov.
Introduction
The Upper Paleozoic in the Hida Marginal Terrane has notable lithologic and paleobiogeographic features with a continental margin affinity, as revealed by those strata of the Carboniferous Ichinotani Formation (Igo, 1956, 1960, 1961) in the Fukuji area. Igo (1956, 1957) considered that the formation is a continuous succession from the upper Lower to Upper Carboniferous without any conspicuous stratigraphic breaks. He divided the Ichinotani Formation and the overlying Mizuyagadani Formation into six fusuline zones from lower to upper: Eostaffella, Profusulinella, Fusulinella, Fusulina, Triticites, and Pseudoschwagerina. The species Pseudoschwagerina morikawai Igo, 1957 had long been considered as an index species of the earliest Permian not only in the Fukuji area but also throughout Japan (e.g. Toriyama, 1967). Later, T. Ozawa and Kobayashi (1990), T. Ozawa et al. (1991), and Watanabe (1991) revealed that the C–P boundary in Japan should be drawn at the first appearance of Sphaeroschwagerina fusiformis (Krotow, 1888) in the Asselian Stage as well as in the stratotype sections of the Urals and Tethyan regions.
Previous workers (Igo, 1957; Niikawa, 1978; Igo et al., 1984) thought that the uppermost part of the Ichinotani Formation consists exclusively of the Upper Carboniferous (Kasimovian and Gzhelian), and is overlain by the Lower Permian (Asselian) Mizuyagadani Formation. Watanabe (1991) assigned the lower part of the Mizuyagadani Formation to the Gzhelian. The studied area along the middle reaches of the Ichinotani valley is occupied by the upper part of the Upper Member of the Ichinotani Formation mainly of late Kasimovian and early Gzhelian ages. This stratigraphic interval, however, is also characterized by the reappearance of Moscovian strata with Beedeina and Ozawainella dominant in the lower part of the Upper Member of the formation and by the absence of strata with reliable middle Kasimovian fusulines, suggesting a more complicated geologic structure in the uppermost part of the Ichinotani Formation than assumed previously. Furthermore, there are some biostratigraphic and taxonomic problems in the case of the comparison of previous works to my paleontologic data of the formation accumulated in the late 1970's, middle 2000's, and middle 2010's.
Figure 1.
Map showing the distribution of Kasimovian and Gzhelian fusuline localities (oval-shaped lines), and locations of Figure 2 and samples Fj-11 and Mz-1 in the Fukuji area. Those of the Mizuboradani valley and upper reaches of the Ichinotani valley are based on Niikawa (1978). Topographic map is from 1:50,000 maps “Kamikochi” published by the Geospatial Authority of Japan.
The main purpose of this paper is (1) to describe the fusuline biostratigraphy and faunal composition of the uppermost part of the Ichinotani Formation along the middle reaches of the Ichinotani valley, (2) to compare the faunal composition of age-diagnostic fusuline species between the Fukuji and other areas especially of the Akiyoshi Limestone, and (3) to describe two species of non-fusuline foraminifers and nine species of fusulines incuding Montiparus japonicus sp. nov. Limestone thin sections used in this paper are stored in the Museum of Nature and Human Activities, Hyogo (Fumio Kobayashi Collection, MNHAH), with prefix Ic, Fj, and Mi.
Samples and biostratigraphy
The Ichinotani Formation of about 350 m thick, and lithostratigraphically divided into three members (Adachi, 1985), is typically developed along the Ichinotani valley (Figure 1). It is overlain by the “Lower Permian” Mizuyagadani Formation (Kamei, 1952; Igo, 1956, 1957; Niikawa, 1978, 1980; Adachi, 1985). Strata exposed around the junction of upstream tributaries northward and westward in the middle reaches of the Ichinotani valley (Figures 1, 2) correspond to the upper part of the Upper Member of the Ichinotani Formation (Adachi, 1985). Biostratigraphically, they are equivalent to the Triticites Zone of Igo (1957) and Niikawa (1978), and Triticites exculptus–T. hidensis Zone of Igo et al. (1984). All of the Kasimovian fusulines illustrated in Watanabe (1991) from the formation originated from this area.
Figure 2.
Sample localities of the Ichinotani Formation around the junction of upstream tributaries northward and westward in the middle reaches of the Ichinotani valley.
The strata bounded by a fault or faults(?) in the studied section are provisionally divided into the Unit 1 to Unit 7 seemingly from lower to upper (Figures 2, 3) based on fusuline biostratigraphy.
Two samples Ic-2A and Ic-3A were collected from the lowest limestone (Unit 1) exposed in the mapped area (Figures 2, 3). They are dark grey to black fusuline packstone with many late Kasimovian to early Gzhelian fusulines such as Carbonoschwagerina katoi (Niikawa, 1978), Rauserites exculptus (Igo, 1957), and Montiparus japonicus sp. nov. Four float limestone samples, Fj-7–10 were collected along the westward tributary where Ic-2A and Ic-3A were collected. Moscovian foraminifers occur in grey bioclastic packstone of Fj-8 (Figures 4.7–4.10). Carbonoschwagerina katoi, Rauserites exculptus, R. saurini (Igo, 1957), and others are contained in the dark grey to black limestone of Fj-9. Samples Fj-7 and Fj-10 consist of dark gray limestone with Rugosofusulina alpina (Schellwien, 1898), Quasifusulina longissima (von Möller, 1878), and Schubertella kingi Dunbar and Skinner, 1937 suggesting an early Gzhelian age. The sources of these four float samples, however, were not confirmed in the field. Additionally, Watanabe (1991) reported “Pseudoschwagerina” morikawai from his float limestone sample collected near the localities of these four float samples.
Because of no exposures, the stratigraphic relationship is uncertain between the limestone from which samples Ic-2A and Ic-3A were collected, and the underlying limestone beds cropping out 30 to 40 m SE of Ic-63 (Figure 2). The latter limestone beds consist of grey to dark grey, oolitic and sparitic limestone and contain late Moscovian (Myachkovian) fusulines (Figures 4.11–4.13, 4.15, 4.16, 4.18, 4.20–4.22) including Fusulinella rhomboidalis Niikawa, 1978 and Fusulinella soligalichi Dalmatskaya, 1961. Their stratigraphic interval is equivalent to the upper part of the Upper Zone of Fusulinella–Fusulina by Niikawa (1980), and to the middle part of the Fusulinella soligalichi Zone by Igo et al. (1984). Igo et al. (1984) divided Igo's (1957) Zone of Fusulina into the lower Beedeina ichinotaniensis Zone and the upper Fusulinella soligalichi Zone. The early Kasimovian Protriticites variabilis Bensh, 1972, was reported by Watanabe (1991) from the dark grey biosparitic limestone without illustrations. P. cf. variabilis (Figure 7.12) is present in a float limestone sample collected by the present author in late 1970's near the Watanabe's (1991) locality. According to Watanabe (1991, p. 23, 24), this early Kasimovian limestone lies about 10 m above the limestone with Fusulinella rhomboidalis.
The original stratigraphic order and thickness along the upstream tributary of the Ichinotani valley extending northward (Units 2 to 7, Figures 2, 3) are not determined exactly on account of bedded limestones dipping steeply to almost vertically and reversed in parts. The stratigraphic interval from the southernmost part of limestone from which sample Ic-63 was collected, to the top of the Ichinotani Formation is subdivided by Igo et al. (1984) and Adachi (1985) into the units 54 to 61 of the Upper Member of the formation. The interval from the sample locality Ic-63 to the level of red shale is named by Watanabe (1991, 2001) as the “Barren Zone” above the limestone with Protriticites variabilis of Watanabe (1991). Fusulines shown by Igo et al. (1984) from the unit 55 are inferred to be collected by them from the same unit exposed along the upstream tributary of the Ichinotani valley extending westward, not northward, under my assumption of their species composition.
Figure 3.
Stratigraphic columns of the Ichinotani Formation around the junction of upstream tributaries northward and westward in the middle reaches of the Ichinotani valley.
Foraminifers are rarely found in the dark grey to grey bedded limestones from which samples Ic-63–65 (oolitic limestone, Figures 4.1, 4.2) were collected. Among them, the occurrence of large-sized Fusiella comparable to F. hayashii Igo, 1957 is important, because the species is restricted to the Moscovian in the Ichinotani Formation. Fusulinella cf. asiatica Igo, 1957 (Figure 4.17), Fusulinella sp. (Figure 4.27), and others suggesting also a Moscovian age occur in sample Ic-66 (Figure 4.3). Poorly-oriented Protriticites sp. and Eostaffella sp. (Figure 4.23) probably assignable to early Kasimovian occur in sample Ic-67, a grey crinoidal grainstone. The conglomeratic limestone (sample Ic-68) (Figure 4.4) in the Unit 4 rarely contains fusulines that are questionably assigned to Protriticites. Foraminifers are also scarce in the bedded grey limesone of Unit 5. Schubertella? sp. and Endothyra? sp. are very rarely found in the grey limestone of sample Ic-69. Dark grey limestone (sample Ic-70) yields Triticites noinskyi plicatus Rozovskaya, 1950 (Figures 7.5, 7.6) suggesting an early Gzhelian age. This species also occurs in the Mizuyagadani valley (Figures 7.7, 7.8?) in association with Carbonoschwagerina morikawai (Figures 8.3, 8.6).
The sample Ic-71, a dark grey algal crinoidal wackestone, is assigned to the upper Moscovian based on the occurrence of a large-sized Ozawainella (Figure 4.31) that is probably referable to the species O. vozhgalica Safonova in Rauzer-Chernousova et al. (1951) characteristic and restricted to the Beedeina ichinotaniensis Zone of Igo et al. (1984). Noteworthy is the occurrence of the Podolskian Beedeina cf. lanceolata (Lee and Chen in Lee et al., 1930) (Figures 4.29, 4.30) from sample Ic-72 in association with O. cf. vozhgalica (Figures 4.14, 4.24–26) and others. In the stratigraphic interval from sample Ic-72 to the base of the Mizuyagadani Formation (Unit 7), Igo et al. (1984) showed the presence of Triticites sadai (nomen nudum), T. saurini, Pseudoschwagerina morikawai praemorikawai (nomen nudum), Rugosofusulina alpina, and others, all of which are hand-drawn specimens. The first and the third taxa were newly proposed by them without description. Based on these fusulines, Igo et al. (1984) assumed the uppermost part of the Ichinotani Formation along the Ichinotani valley as transitional strata between the Upper Carboniferous and the basal Permian. However, more evolved Carbonoschwagerina, “Pseudoschwagerina” minatoi Kanmera, 1958 than “P.” morikawai illustrated by Watanabe (1991) from the Mizuyagadani valley is not reported by Igo et al. (1984) from the Ichinotani valley. Three specimens named Schwagerina? satoi Y. Ozawa, 1925 were illustrated by Watanabe (1991, figs. 24.28–24.30) from the top of the Ichinotani Formation along the Ichinotani valley. These fusulines have more advanced test characters than Schwagerina? satoi that were illustrated from Watanabe's float limestone samples in his “Barren Zone”. Although these fusulines reported by Igo et al. (1984) and Watanabe (1991) from the top of the Ichinotani Formation (Unit 7) could not be found by the present author, they are thought to be an early Gzhelian age.
Figure 4.
Limestone lithology and some Moscovian foraminifers. 1, Ooid grainstone D2-059530, Ic-63. 2, Bioclastic oolitic grainstone, D2-059537, Ic-64. 3, Oolitic crinoidal grainstone, D2-059557, Ic-66. 4, Protriticites?-bearing conglomeratic limestone, D2-059569, Ic-68. 5, algal crinoidal wackestone, D-059587, Ic-71. 6, Beedeina-bearing algal wackestone/packstone, D2-059608, Ic-72. 7, 16, Fusulinella spp.; 7, D2-035710, Fj-8; 16, D-059441, Ic-58 (about 34 m below Ic-63). 8, 9, Eoschubertella obscura (Lee and Chen in Lee et al., 1930), both D-035708, Fj-8. 10, Globivalvulina moderata Reitlinger, 1949, D-035708, Fj-8. 11, 19, Rectoendothyra sp.; 11, D2-059488, Ic-61(about 29 m below Ic-63); 19, D2-059528, Ic-63. 12, 18, Fusulinella rhomboidalis Niikawa; 12, D2-059440, Ic-58; 18, D2-059476, Ic-61. 13, Fusulinella soligalichi Dalmatskaya, D2-059477, Ic-61. 14, 24–26, Ozawainella cf. vozhgalica Safonova; 14, D2-059601; 24, D2-059643; 25, D2-059641; 26, D2-059630; all Ic-72. 15, 21, 22, Fusiella hayashii Igo; 15, D2-059514; 21, D2-059499; 22, D2-059515; all Ic-62. 17, Fusulinella cf. asiatica Igo, D2-059554, Ic-66. 20, Eoschubertella sp., D2-059520, Ic-62 (about 30 m below Ic-63). 23, Eostaffella sp., D-059565, Ic-67. 27, Fusulinella sp., D2-059556, Ic-66. 28, Bradyina regularis Lin, 1978; D-059500, Ic-62. 29, 30, Beedeina cf. lanceolata (Lee and Chen); 29, D2-059629; 30, D2-059602; both Ic-72. 31, Ozawainella vozhgalica Safonova, D2-059592, Ic-71. Scale bar is 1 mm; bar A for 1–6; bar B for 12, 13, 16–18, 27–30; bar C for 15, 21, 22; bar D for 7, 14, 24–26, 31; bar E for 8–11, 19, 20, 23.
Figure 5.
Fusuline zonation and biostratigraphic distribution of some Kasimovian and Gzhelian fusulines in the Wakatakeyama area of the Akiyoshi Limestone (Kobayashi, 2017), and ranges of some coeval fusuline species in the Fukuji area. Q. longissima = Quasifusulina longissima; Protrit. = Protriticites; Mont. = Montiparus; Schw. = Schwagerina; Carb. = Carbonoschwagerina; Raus. = Rauserites; Darvasos. = Darvasoschwagerina.
Summarizing the above discussion, the upper part of the Upper Member of the Ichinotani Formation along the middle reaches of the Ichinotani valley is not composed throughout of only the upper Kasimovian and lower Gzhelian, but also includes the Moscovian strata of several meters thick in at least two horizons. More Moscovian beds are presumable in the mapped area from the presence of float samples containing Moscovian fusulines. The Moscovian beds in the northern part of the mapped area (Units 2 and 6) are inferred to be fault-bounded with the underlying and overlying strata having Gzhelian or Kasimovian fusulines. These points of biostratigraphic information suggest more complicated geological structure of the formation than previously assumed.
Limestone assigned to the “Pseudoschwagerina” Zone along the Ichinotani valley is confined to the float sample of Watababe (1991) as mentioned above. Triticites elongatus Niikawa, 1978 proposed newly from the lenticular limestone of this zone and occurring along the upper reaches of the valley (Niikawa, 1978, loc. 46) should be reassigned to an elongate form of Jigulites that is common in the middle to upper Gzhelian of the Tethyan regions. In addition to the species “Pseudoschwagerina” morikawai and “P.” minatoi, a transitional form from “P.” morikawai to “P.” minatoi was illustrated by Watanabe (1991) from strata along the Mizuyagadani valley. Carbonoschwagerina minatoi is the index species of the uppermost Gzhelian of Japan (T. Ozawa et al., 1992; Kobayashi, 2017). Carbonoschwagerina described herein from the lower reaches of the Takadani valley (Figure 1) belongs to a primitive form of C. morikawai. Many individuals of non-fusuline foraminifers such as Climacammina, Tetrataxis, Bradyina, and Pseudojanischewskina also occur in the Takadani valley. Further biostratigraphic studies should be done around the Mizuyagadani valley, where Niikawa (1978, 1980) showed fault-bounded relations between the Zone of Triticites and the Zone of Pseudoschwagerina, and the Upper and Lower Zones of Fusulinella–Fusulina.
Biostratigraphic correlation and faunal implications
As noted above, the fusuline biostratigraphy of the Kasimovian and Gzhelian is described based on my data mainly along the middle reaches of Ichinotani valley in comparison to previous works in the Fukuji area. Although the biostratigraphic ranges of fusulines are not exactly determined independently in the Fukuji area, they are roughly estimated based on age-diagnostic species common between the Fukuji area and other areas especially of the Akiyoshi Limestone (Kobayashi, 2017). Approximate ranges of some of them in the former are shown on the basis of the biostratigraphic correlation between the former and the latter (Figure 5).
Obsoletes obsoletus (Schellwien, 1908) reported by Niikawa (1978) is more related to O. grosdilovae (Miklukho-Maklay, 1949) described from the lower Kasimovian of the southern Fergana by Bensh (1972). An occurrence of the species supports the presence of the lower Kasimovian in the Fukuji area along with Protriticites cf. variabilis, and is not in conflict with that of Fusulinella rhomboidalis and F. soligalichi from the lowerlying Moscovian beds. F. rhomboidalis is confined to the Myachkovian in the Akiyoshi Limestone, and F. soligalichi was originally described from the upper Podolskian and the lower Myachkovian along the Volga of the Russian Platform (Dalmatskaya, 1961).
Fusulines apparently correlatable to the middle Kasimovian are not found in the Fukuji area. Dark grey to black limestone beds containing Carbonoschwagerina katoi, Rauserites exculptus, and others are assigned to the upper Kasimovian to lower Gzhelian based on the biostratigraphic range of R. exculptus in the Akiyoshi Limestone. Although the faunal composition somewhat resembles that from the late Kasimovian to early Gzhelian, Rugosofusulina alpina and Triticites noinskyi plicatus characteristic in the Fukuji area are unknown from Akiyoshi. On the contrary, middle Gzhelian Jigulites horridus (Kanmera, 1958) and late Gzhelian J. titanicus Kobayashi, 2017 are more dominant than coeval Carbonoschwagerina morikawai and C. minatoi, respectively, in the Akiyoshi Limestone, and are completely absent in the Fukuji area, along with Darvasoschwagerina shimodakensis (Kanmera, 1958) and Pseudofusulina kumasoana Kanmera, 1958 also characteristic in the middle and upper Gzhelian of the Akiyoshi Limestone.
More conspicuous faunal dissimilarities at the generic level are recognized in the Moscovian between the Fukuji and Akiyoshi areas. Neostaffella and Hidaella are absent in coeval strata throughout Japan except for the Ichinotani Formation. Early Moscovian Akiyoshiella, late Moscovian Kanmeraia, and middle Kasimovian Quasifusulinoides characteristic to the Akiyoshi Terrane are absent in the Fukuji area. Carbonoschwagerina morikawai and C. minatoi are common throughout the Gzhelian of Japan. Kasimovian to Gzhelian inflated schwagerinids exemplified by Carbonoschwagerina and Tumefactus have particular implications to late Carboniferous paleobiogeography and faunal provincialism. Tumefactus, proposed by Leven and Davydov (2001) as a subgenus of the genus Schwageriniformis and distributed in the western Paleo-Tethys, is a counterpart of Carbonoschwagerina and is related morphologically, but unrelated phylogenetically (Kobayashi, 2017).
Faunal similarities and dissimilarities summarized above should also be affected strongly by paleoenviro-mental controls typified by the exclusive occurrence of reddish shale and sharpstone conglomerate in the Ichinotani Formation throughout Japan (Igo, 1960, 1961). They are also attributed to the origin of the Japanese terranes, the continental margin of ancient North China in the Hida Marginal Terrane versus the Panthalassan sea-mounts accreted to ancient South China in the Akiyoshi Terrane, and are important for the tectonic evolution and amalgamation of East Asia from the Late Paleozoic to the Middle Mesozoic.
Description of species
Genus Bradyina von Möller, 1878
Type species.—Bradyina nautiliformis von Möller, 1878.
Bradyina nautiliformis von Möller, 1878
Figure 9.29, 9.30, 9.34–9.36, 9.39
Bradyina nautiliformis von Möller, 1878, p. 83, pl. 3, fig. 4a–d; pl. 10, fig. 3a, b; Lee and Chen in Lee et al., 1930, p. 104, pl. 5, figs. 5–9; Rauzer-Chernousova et al., 1940, p. 47, pl. 8, figs. 1–3; pl. 9, figs. 1–3; Putrya, 1956, p. 371, pl. 1, figs. 9–11; Lin, 1978, p. 36, pl. 7, fig. 16; Igo and Adachi, 1981, p. 110, pl. 6, fig. 15 (= Adachi, 1985, p. 115, 116, pl. 18, fig. 1); Kobayashi, 2019, p. 6, 7, 9, figs. 5.1–5.14; Kobayashi and Vachard, 2019, p. 367, 369, pl. 1, figs. 62, 63; pl. 3, figs. 1–6, 30.
Remarks.—Size and shape of the test, degree of depth of umbilicus, thickness of wall, and perforation of pseudo-keriotheca are considerably variable from specimen to specimen in the present material. They are supposed to represent the intraspecific variations of Bradyina nautiliformis, as suggested by Kobayashi (2019). This species is distinguished from Bradyinelloides pseudonautiliformis (Reitlinger, 1950) illustrated herein in Figure 9.31–9.33 by its thinner and not so coarsely alveolar thick wall.
Genus Pseudojanischewskina Mamet and Pinard, 1990
Type species.—Pseudojanischewskina multicribrata Mamet and Pinard, 1990.
Pseudojanischewskina sp. A
Figure 9.27, 9.28
Remarks.—This unnamed species is assigned to Pseudojanischewskina based on its thinner wall consisting of a tectum and much more finely porous layer. Remnants of septa and lamellae are sporadically present in association with the main septa that gently curved outward. These characters are also recognized in Pseudojanischewskina sp. B (Figure 9.25, 9.26), but the test of P. sp. A is almost spherical. P. sp. A and P. sp. B differ from the known species of the genus by their smaller test and fewer number of whorls in mature stage.
Figure 6.
1–6, 11, 12, Carbonoschwagerina katoi (Niikawa, 1978); 1, D2-004042; 2, 3, D2-004041; 4, D2-035728; 5, D2-004043; 6, D2-004045; 11, D2-004038; 12, D2-004046; 4, Fj-9, others Ic-2A; 7–10, 13, 14, Rauserites exculptus (Igo, 1957); 7, D2-035728; 8, D2-035733; 9, D2-035722; 10, D2-035715; 13, D2-004040; 14, D2-035717; 13, Ic-2A, others Fj-9; 15–21, 24, Rauserites saurini (Igo, 1957); 15, D2-035731; 16, D2-035730; 17, D2-035716; 18, D2-035725; 19, D2-035734; 20, D2-035724; 21, D2-035732; 24, D2-035719; all Fj-9; 22, 25, 29–34, Montiparus japonicus sp. nov.; 22, D2-004062; 25, D2-004037; 29, D-004036; 30, D2-004039; 31, D2-004064; 32, D2-004065; 33, D2-004063; 34, D2-004061; 25, 29, 30, Ic-2A; others Ic-3A; 34: holotype, others: paratypes; 23, 26–28, Schubertella kingi Dunbar and Skinner, 1937; 23, 27, D2-035697; 26, D2-035753; 28, D2-035695; 26, Fj-10; others Fj-7. Scale bar is 1 mm; bar A for 7–22, 24, 25, 29–44; bar B for 1–6; bar C for 23, 26–28.
Figure 7.
1–4, Lasiodiscus? sp.; 1, D2-035752; 2, D2-035739; 3, D2-035766; 4, D2-035743; all Fj-10; 5–7, 8?, Triticites noinskyi plicatus Rozovskaya, 1950; 5, D2-059581, Ic-70; 6, D2-059582, Ic-70; 7, D2-059665, Mz-1; 8, D2-059656, Mz-1; 9–11, Quasifusulina longissima (von Möller, 1878); 9, D2-035704; 10, D2-035759; 11: D2-035746; 9, Fj-7; others Fj-10; 12, Protriticites cf. variabilis Bensh, 1972, D2-004136, Ic-9A; 13–28, Rugosofusulina alpina (Schellwien, 1898); 13, D2-035765; 14, D2-35695; 15, D2-035696; 16, D2-035758; 17, D2-035755; 18, D2-035743; 19, D2-025740; 20, D2-035701; 21, D2-035766; 22, D2-035753; 23, D2-035699; 24, D2-035751; 25, D2-035745; 26, D2-035702; 27, D2-035700; 28, D2-035760; 14, 15, 20, 23, 26, 27, Fj-7; others Fj-10. Scale bar is 1 mm; bar A for 1–4, bar B for 12, bar C for 5–11, 13–28.
Figure 8.
1–23, Carbonoschwagerina morikawai (Igo, 1957); 1, D2-035839; 2, D2-035784; 3, D2-059653; 4, D2-035829; 5, D2-035767; 6, D2-059662; 7, D2-035832; 8, D2-035820; 9, D2-035794; 10, D2-035792; 11, D2-035783; 12, D2-035781; 13, D2-0358338; 14, D2-035789; 15, D2-035788; 16, D2-035782; 17, D2-035805; 18, D2-035828; 19, D2-035779; 20, D2-035801; 21, D2-035787; 22, D2-035803; 23, D2-035776; 3, 6, Mz-1; others Fj-11. Scale bar of 2 mm for all.
Figure 9.
1–6, Carbonoschwagerina morikawai (Igo, 1957); 1, D2-035836; 2, D2-035809; 3, D2-035799; 4, D2-035806; 5, D2-035786; 6, D2-035777; all Fj-11; 7, Endothyra? sp. A, D2-035811, Fj-11; 8, Endothyra? sp. B, D2-035835, Fj-11; 9–12, Tetrataxis sp.; 9, D2-035806; 10, 12, D2-035843; 11, D2-035798; all Fj-11; 13, Deckerella sp., D2-035777, Fj-11; 14–17, Climacammina cf. procera Reitlinger, 1950; 14, D2-035842; 15, D2-035768; 16, D2-035838; 17, D2-035811; all Fj-11; 18, Climacammina sp., D2-035838, Fj-11; 19, 20, Schubertella cf. mjachkoensis Rauzer-Chernousova in Rauzer-Chernousova et al., 1951; 19, D2-035839; 20, D2-035803; both Fj-11; 21, 22, Bradyina minima Reitlinger, 1950; 21, D2-59578, Ic-70; 22, D2-035803, Fj-11; 23, Pseudobradyina? sp., D2-035826, Fj-11; 24, Reitlingerina sp., D2-035800, Fj-11; 25, 26, Pseudojanischewskina sp. B; 25, D2-035841, Fj-11; 26, D2-035702, Fj-7; 27, 28, Pseudojanischewskina sp. A; 27, D2-035827; 28, D2-035829; both Fj-11; 29, 30, 34–36, 39, Bradyina nautiliformis von Möller, 1878; 29, D2-035780; 30, D2-035802; 34, D2-035786; 35, D2-059580; 36, D2-035772; 39, D2-035825; 35, Ic-70; others Fj-11; 31–33, Bradyinelloides pseudonautiliformis (Reitlinger, 1950); 31, D2-035793, Fj-11; 32, D2-035743, Fj-10; 33, D2-035781, Fj-11; 37, 38, Bradyina papilionacea Lin, 1978; 37, D2-035767, Fj-11; 38, D2-35700, Fj-7. Scale bar is 1 mm; bar A for 1–6; bar B for 15, 18, 29, 30, 34–36, 38, 39; bar C for 17, 31–33, 37; bar D for 9–14, 16, 21, 22, 24; bar E for 19, 20, 25–28; bar F for 7, 8, 23.
Table 1.
Measurements of Rugosofusulina alpina (Schellwien, 1898).
Genus Quasifusulina Chen, 1934
Type species.—Fusulina longissima von Möller, 1878.
Quasifusulina longissima (von Möller, 1878)
Figure 7.9–7.11
Fusulina longissima von Möller, 1878, p. 59–61, pl. 1, fig. 4; pl. 2, fig. 1a–c; pl. 7, fig. 1a–c.
Quasifusulina longissima (von Möller). Chen, 1934, p. 92, 93, pl. 5, figs. 6–9; Igo, 1957, p. 224, 225, pl. 8, figs. 13–18; pl. 11, figs. 12, 13; Niikawa, 1978, p. 561, 562, pl. 11, figs. 5, 7, 9, 10, 12; Watanabe, 1991, fig. 31.6–31.11; Watanabe, 1997, p. 101–106, pl. 11, figs. 1–16; Kobayashi, 2017, p. 43, pl. 11, figs. 25–36.
Remarks.—Specimens assigned to this species in the Fukuji area are described from the Triticites Zone and Pseudoschwagerina Zone by Igo (1957) and Niikawa (1978), and illustrated from the “Pseudoschwagerina” minatoi Zone by Watanabe (1991). Quasifusulina is not found in sample Fj-11 with Carbonoschwagerina morikawai. The illustrated specimens herein were obtained from float samples Fj-7 and Fj-10 in association with Rugosofusulina alpina. The largest specimen in sample Fj-10 is more than 9.5 mm in length. Longer diameter of proloculus in sample Fj-7 and Fj-10 ranges from 0.25 to 0.48 mm. The present specimens are closely similar to those described by authors. Watanabe (1997, p. 106) transferred Niikawa's (1978) longissima specimens and Igo's (1957) one specimen to Q. longissimi ultima Kanmera, 1958 based on a larger proloculus.
Genus Rugosofusulina Rauzer-Chernousova, 1937
Type species.—Fusulina prisca Ehrenberg, 1842.
Rugosofusulina alpina (Schellwien, 1898)
Figure 7.13–7.28
Fusulina alpina var. communius Schellwien, 1898, p. 245–247, pl. 17, figs. 5–7.
Schellwienia alpina (Schellwien). Lee, 1927, p. 94–96, pl. 15, figs. 1–11.
Rugosofusulina alpina (Schellwien). Rauzer-Chernousova, 1937, pl. 2, fig. 7; Igo, 1957, p. 239–242, pl. 14, figs. 11–15; pl. 15, figs. 1, 2; Shcherbovich, 1969, p. 26, 27, pl. 7, figs. 4–6.
Measurements.—Shown in Table 1.
Description.—Test elongate fusiform with broadly arched periphery, straight to slightly convex lateral sides, and rounded poles. Periphery and lateral sides of the test more or less undulated. Test consists of four to five whorls, 5.21 to 7.75 mm in length and 2.19 to 2.95 mm in width, giving a form ratio 2.3? to 3.19. Proloculus is spherical to subspherial and its longer diameter 0.28 to 0.53 mm. Length, width, and form ratio of whorls gradually increase outwards. Wall, smooth to slightly undulate in inner whorls, becomes thicker and distinctly undulate in most of middle and outer whorls, and consists of a tectum and alveolar keriotheca. Thickness of the wall is 0.08 to 0.15 mm in the thickest middle and outer whorls.
Septa closely spaced throughout whorls, irregularly and intensely folded in polar regions, and planar to weakly folded in tunnel regions. Septal counts from the first to fifth whorls 8 to 11, 21 to 25, 24 to 28, 27 to 29, and more than 13 in the illustrated five sections, respectively. Septal sutures distinct in general in outer whorls. Tunnel low and narrow in inner whorls, gradually higher outwards. Its path becomes irregular and wider in outer whorls. Chomata absent except on poloculus and inner few whorls.
Remarks.—Sixteen specimens illustrated herein are closely similar to those identified by Igo (1957) with this species in many respects. This species was originally divided into three varieties, Fusulina alpina var. anti-qua, F. alpina var. fragilis, and F. alpina var. communius by Schellwien (1898). Among the three, the Fukuji specimens are closely similar to F. alpina var. communius, though having a more undulated wall and larger proloculus. Lee (1927) noted the difficulty of the taxonomic separation of the varieties. Rauzer-Chernousova (1937) considered the independency of Fusulina alpina var. communius from two other varieties and reassigned alpina to Rugosofusulina. Size and shape of the test and proloculus, degree of undulation and thickness of the wall are more or less variable in the Fukuji material. These differences gradually changing from specimen to specimen are due to the intraspecific variations of this species. This species is similar to Rugosofusulina prisca ovoidea Bensh, 1972 proposed from the Kasimovian of the southern Fergana (Bensh, 1972), but has a larger proloculus and thicker wall.
Genus Carbonoschwagerina T. Ozawa, Watanabe, and Kobayashi, 1992
Type species.—Pseudoschwagerina morikawai Igo, 1957.
Remarks.—See Kobayashi (2017, p. 102, 104).
Carbonoschwagerina katoi (Niikawa, 1978)
Figure 6.1–6.6, 6.11, 6.12
Triticites katoi Niikawa, 1978, p. 565, 566, pl. 14, figs. 1, 2.
Triticites ichinotaniensis Niikawa, 1978, p. 566, 567, pl. 13, figs. 8, 9.
Triticites paramontiparus Niikawa, 1978, p. 564, pl. 13, figs. 1, 2.
Schwagerina? satoi Y. Ozawa, 1925. Watanabe, 1991 (pars), fig. 24.19–24.27. (non 24.28–24.30)
Remarks.—Niikawa (1978) proposed three new species of Triticites listed above from the same sample. They are safely reassigned to Carbonoschwagerina. Relative to other species of the genus, they are characterized by a smaller test, larger proloculus, and thicker wall throughout growth. These three new species are not easily differentiated from each other based on more or less differences in size of the test and proloculus, degree of inflation of the test, and thickness of the wall, as done by Niikawa (1978). Watanabe (1991, p. 26) suggested that they are conspecific. Likewise, Kobayashi (2017) recognized close similarities among Triticites katoi, T. ichinotaniensis, and Carbonoschwagerina nipponica Kobayashi, 2017. C. nipponica was distinguished from the first and second species by having larger test and thinner wall (Kobayashi, 2017). Triticites paramontiparus is also treated as synonymous with T. katoi, since slight morphological differences among T. katoi, T. ichinotaniensis, and T. paramontiparus are presumed to be intraspecific variations of T. katoi.
Among 12 specimens identified as Schwagerina? satoi by Watanabe (1991) from the Ichinotani Formation, nine are associated with Rauserites exculptus and R. hidensis (Igo, 1957), and came from float samples. They have a smaller test, and smaller length and width in corresponding whorls than other three specimens named also as Schwagerina? satoi by Watanabe (1991) from the top of the formation that are thought to be a more evolved form of Carbonoschwagerina than C. katoi. Specimens questionably assigned to Schwagerina by Watanabe (1991) including S.? satoi from the Akiyoshi Terrane and the Ichinotani Formation are transferred from Schwagerina? to Carbonoschwagerina. The septa are folded throughout the test in the topotypes of Schwagerina satoi from the upper Kasimovian and lower Gzhelian of the Akiyoshi Limestone (Kobayashi, 2017, p. 90, 92, pl. 23, figs. 6–31).
Carbonoschwagerina morikawai (Igo, 1957)
Figures 8.1–8.23, 9.1–9.6
Pseudoschwagerina morikawai Igo, 1957, p. 238, 239, pl. 15, figs. 11–17; Kanmera, 1958, p. 177–179, pl. 27, figs. 1–11; Niikawa, 1978, p. 568, pl. 14, figs. 5–8.
“Pseudoschwagerina” morikawai Igo. T. Ozawa and Kobayashi, 1990, pl. 4, figs. 19, 20; Watanabe, 1991, figs. 26.1–26.14; figs. 27.1–27.11; figs. 28.3–28.5.
Carbonoschwagerina morikawai (Igo). T. Ozawa, Watanabe, and Kobayashi, 1992, p. 396, 397, figs. 10.8–10.12; Kobayashi, 2017, p. 106, 108, pl. 14, figs. 5–16; pl. 15, figs. 1–13.
Remarks.—Type specimens of Carbonoschwagerina morikawai from the Mizuyagadani valley (Igo, 1957) and the present ones from the Takadani valley have a smaller test and larger proloculus than those from the Yayamadake Limestone (Kanmera, 1958) and the Akiyoshi Limestone (Watanabe, 1991; Kobayashi, 2017). C. morikawai of the Fukuji area, however, cannot be separated from that of the Yayamadake and Akiyoshi limestones on the species level by slight differences of other test characters such as the number of juvenile whorls and degree of expansion of the test, along with thickness of the wall, mode of septal folding, development of chomata, and their ontogenetic changes.
The described species is distinguished from C. minatoi (Kanmera, 1958) as mentioned in Kanmera (1958), Watanabe (1991), and Kobayashi (2017). Watanabe (1991) recognized a transitional form from morikawai to minatoi and showed the one-way trend of evolution from C. morikawai to C. minatoi. Comparison of these two species between Japanese and foreign materials were discussed by Watanabe (1991) and Kobayashi (2017). Moreover, Kobayashi (2017) pointed out Carbonoschwagerina nakazawai (Nogami, 1961) is an ancestral form of C. morikawai. In addition to two specimens from the Mizuyagadani valley, many specimens from the Takadani valley are illustrated herein to compare to those referable to the genus reported in and outside Japan.
Table 2.
Measurements of Montiparus japonicus sp. nov.
Genus Montiparus Rozovskaya, 1948
Type species.—Fusulina montipara von Möller, 1878.
Montiparus japonicus sp. nov.
Figures 6.22, 6.25, 6.29–6.34
ZooBank lsid: urn:lsid:zoobank.org:act:0D26D019-19C8-4975B9DB-1EB62B186D01
Etymology.—From Japan.
Type specimens.—Holotype, MNHAH D2-004061, axial section from Ic-3A (Figure 6.34). Paratypes: six axial sections from Ic-2A and Ic-3A (Figures 6.25, 6.29–6.33), and one sagittal section from Ic-2A (Figure 6.22). Register numbers of seven paratypes are shown in the explanation of Figure 6.
Type locality.—Middle reaches of Ichinotani valley, Fukuji area, Takayama City, Gifu Prefecture.
Diagnosis.—Inflated fusiform Montiparus consisting of relatively tightly coiled inner whorls followed by gradually expanding outer whorls with an arched periphery and rounded to bluntly pointed poles. Septa closely spaced, intensely folded in the polar regions resulting many irregularly-shaped and irregularly-sized loops, and almost planar to very weakly folded in the median part of the test. Chomata are massive and well-developed.
Measurements.—Shown in Table 2.
Description.—Test inflated fusiform with an arched periphery, straight to slightly concave lateral sides, and rounded to bluntly pointed poles. Mature test has six to seven whorls, 4.96 to 5.8? mm in axial length and 1.95 to 2.63 mm in median width, giving a form ratio of 2.06 to 2.8?.
Proloculus is spherical, 0.07 to 0.19 mm in diameter. The first to the second whorls subspherical to inflated fusiform and succeeded by outer whorls gradually increasing their length and width. Poles of middle and outer whorls are rounded to more or less pointed.
Wall is thin and not differentiated in inner one or two whorls, and gradually thickened outward and consists of a tectum and finely alveolar keriotheca. Thickness of the wall is 0.015 to 0.028 mm in inner one or two whorls and 0.051 to 0.097 mm in outer two whorls. Septa are closely spaced throughout the test, strongly folded in the polar regions of middle and outer whorls resulting many irregularly-shaped and irregularly-sized loops, and almost planar to very weakly folded in the median part of the test. Septal counts from the first to seventh whorl 9, 16, 19, 23, 26, 27, and more than 25 in the paratype.
Tunnel is less than half as high as chambers in inner two whorls, and becomes somewhat higher in outer whorls. Its path is narrow and almost straight to irregularly zigzag. Chomata are massive, well-developed, and about a third as high as chambers in most specimens. They appear in contact with the roof of chambers is due to secondary deposits in specimens. Axial fillings are not present.
Remarks.—This new species resembles Montiparus subcrassulus proposed by Rozovskaya (1950) from the middle Kasimovian of the Moscow Basin in size and shape of the test. The former is distinguished from the latter by having more strongly folded septa in the polar regions and more massive chomata in the inner and middle whorls. It is also similar to Montiparus umbonoplicatus (Rauzer-Chernousova and Belyaev in Rauzer-Chernousova and Fursenko, 1937) originally described from Samara Bend, Russia, later from the Donetz Basin (Putrya, 1940) and the Moscow Basin (Rozovskaya, 1950), and recently from the Akiyoshi Limestone (Kobayashi, 2017). However, M. japonicus has a more inflated fusiform test and more strongly folded septa in the polar regions. It is distinguished from M. montiparus, type species of the genus, by its larger test, and more intensely and more irregularly folded septa. M. japonicus is similar to some specimens of the Montiparus matsumotoi inflatus Watanabe (nomen nudum) illustrated from the middle Kasimovian of the Omi Limestone without description (Watanabe, 1991, figs. 18.1–18.6). However, the former has a larger test, not so tightly coiled inner whorls, and more strongly folded septa than the latter.
The new species differs from Protriticites globulus Putrya, 1948, designated as the type species of the genus (Putrya, 1948) by its mode of septal folding: very weakly folded in the median part of the test and more intensely folded in polar regions. Likewise, it is not assigned to Rauserites because of its almost planar to very weakly folded septa in the median part of the test and more developed chomata.
Genus Protriticites Putrya, 1948
Type species.—Protriticites globulus Putrya, 1948.
Protriticites cf. variabilis Bensh, 1972
Figure 7.12
Cf.
Protriticites variabilis Bensh, 1972, p. 22, 23, pl. 1, figs. 1–4; Kobayashi, 2017, p. 46, 47, pl. 9, figs. 18–33.
Remarks.—The illustrated specimen is compared to P. variabilis originally described from the lower Kasimovian (Protriticites pseudomontiparus-Obsoletes obsoletus Zone) of the southern Fergana by Bensh (1972) and recently from the lower Kasimovian of the Akiyoshi Limestone by Kobayashi (2017). They somewhat resemble each other in their well developed chomata, weakly folded septa in the polar regions, and finely perforate layer between the tectum and lower tectorium in outer whorls. More well-oriented specimens are needed for further comparison.
Genus Rauserites Rozovskaya, 1950
Type species.—Triticites stuckenbergi Rauzer-Chernousova, 1938.
Rauserites exculptus (Igo, 1957)
Figure 6.7–6.10, 6.13, 6.14
Triticites exculptus Igo, 1957, p. 225, 226, pl. 12, figs. 1–17.
Triticites exculptus var. naviformis Igo, 1957, p. 228–230, pl. 12, figs. 18–24.
Rauserites exculptus (Igo). Kobayashi, 2017, p. 52, 54, pl. 18, figs. 20–49.
Remarks.—This species was distinguished from Triticites exculptus var. naviformis in its smaller test and less complicated septal folding by Igo (1957). However, both taxa are not easily separated each other based on slight differences of size and shape of the test, and mode of septal folding. T. exculptus is reassigned to Rauserites based on its mode and strength of septal folding. Rauserites hidensis (Igo, 1957) might be distinguished from R. exculptus by its larger test, larger proloculus, and more strongly foled septa, though its strict distinction from R. exculptus is not easy.
Some morphological resemblances between Triticites exculptus and T. matsumotoi Kanmera, 1955 were indicated by Igo (1957). However, the latter is distinguishable from the former by more developed chomata, more finely alveolar keriotheca even in outer whorls of the test, and weakly folded septa in the polar regions. Based on the mode and strength of septal folding, T. matsumotoi is reassigned to Montiparus.
Rauserites saurini (Igo, 1957)
Figure 6.15–6.21, 6.24
Triticites saurini Igo, 1957, p. 230–232, pl. 14, figs. 1–9; Niikawa, 1978 (?), p. 564, 565, pl. 13, figs. 4–7.
Remarks.—Specimens with a larger and more elongate test, and greater length and width in corresponding whorls than Rauserites exculptus are identical with Triticites saurini also reassignable to Rauserites. The mode of septal folding and development of chomata are similar between these two species. In spite of the similar mode of septal folding, species identification with Triticites saurini by Niikawa (1978) is questionable because of highly variable length and width of corresponding whorls and somewhat corrugated wall in his illustrated specimens that are associated with Carbonoschwagerina morikawai. Kobayashi (2017) assumed that R. saurini might be conspecific with R. hidensis. However, many mature specimens, some of which are illustrated herein, suggest the taxonomic separation of R. saurini from R. hidensis based on larger and more elongate test in R. saurini.
Genus Triticites Girty, 1904
Type species.—Miliolites secalicus Say in James, 1823.
Triticites noinskyi plicatus Rozovskaya, 1950
Figure 7.5–7.7, 7.8?
Triticites noinskyi plicatus Rozovskaya, 1950, p. 26, pl. 5, figs. 13–16.
Remarks.—Rozovskaya (1950) proposed Triticites noinskyi plicatus from the upper Kasimovian and lower Gzhelian of the Russian Platform by its more intensely folded septa than of Triticites noinskyi Rauzer-Chernousova, 1938. Though well-oriented specimens are few in sample Ic-70 and sample Mz-1, they are identified with T. noinskyi plicatus by their similarities of the mode of septal folding, length and width of the test, size of proloculus, and thickness of the wall to those of the original Russian ones.
Acknowledgements
The author is grateful to Yasuhiro Ota and Merlynd Nestell for their constructive comments and helpful review of this paper, and to Hiroshi Furutani for his invaluable information on the geology of the Fukuji area and his help in the field. Financial support for the field and laboratory work from Grant-in Aid for Scientific Research (C) of Japan Society for promotion of Science in 2013–2015 is gratefully acknowledged.
