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Journal of Paleontology 91(1):12–24
Holotype.—The specimen (No. 8165) from the Maokou Formation, Liangshan area of Shaan’xi, China (Sheng, 1956, pl. 8, fig. 6).
Occurrence.—This species is widely distributed in the Guada- lupian Maokou Formation in North and South China, and in the Lhasa Block (Fan et al., 2013).
Description.—Test small, fusiform with bluntly rounded poles. Spirotheca composed of the tectum and coarsely alveolar keriotheca. Adult tests commonly have 5–6.5 whorls, with 4.0–5.4mm in length and 1.7–2.3mm in width, giving axial ratio 2.3–2.7. Septa are fluted strongly and irregularly. Septal folds are nearly as high as half of the chamber’s height. Proloculus is moderate in size, around 0.2mm in outside diameter. Axial fillings present.
Family Staffellidae Miklukho-Maklay, 1949 Subfamily Staffellinae Miklukho-Maklay, 1949 Genus Nankinella Lee, 1934
Type species.—Staffella discoides Lee, 1931 from the upper Chihsia Limestone of Nanjing in Jiangsu province, China, assigned as the genotype of Nankinella by Lee (1934).
Nankinella mingshanensis Sheng and Rui, 1984 Figure 3.5, 3.6, 3.11
1984 Nankinella mingshanensis Sheng and Rui, p. 34, pl. 1, figs. 24–26.
Holotype.—The specimen (no. 82384) from the Palaeofusulina sinensis zone, Leping village of Jiangxi, China (Sheng and Rui, 1984, pl. 1, fig. 25).
Occurrence.—This species was first discovered in the upper Permian strata in Jiangxi (Sheng and Rui, 1984) and later discovered in the Maokou Formation in Guizhou (Zhang et al., 1988) and Yunnan (Zhou, 1998).
Description.—Test median, subrhomboidal with narrowly pointed periphery, slightly convex lateral sides, and closed umbilici. Adult tests commonly develop 6–8 whorls, with length in the range of 1.2–1.7mm, width 1.9–2.9mm, giving axial ratio around 0.6. Spirotheca with three layers, tectum as well as outer and inner tectorium. Septa straight. Proloculi are quite small, less than 0.1mm in diameter, therefore difficult to recognize and measure in most thin sections.
Nankinella orientalis Miklukho-Maklay, 1954 Figure 3.1–3.4, 3.10
1954 Nankinella orientalis Miklukho-Maklay, p. 70, pl. 11, figs. 1–4.
1963 Nankinella orientalis; p. 31, pl. 2, figs. 8–10.
Holotype.—The specimen (no. 226-4-45) from a pebble of foraminiferal limestone from Lower Triassic conglomerates in Epchika area, northern Caucasus (Miklukho-Maklay, 1954).
Occurrence.—This species is commonly distributed in the Changhsingian of North and South China, and has been reported from the Guadalupian strata in Azerbaijan associated with Chusenella and Verbeekina (Ruzhentsev and Sarycheva, 1965).
Description.—Test median, subrhomboidal with rounded periphery, slightly convex lateral sides, and closed umbilici. Test of inner whorls with narrowly pointed periphery. Adult tests commonly develop 6–9 whorls, with 1.5–1.9mm in length and 2.0–2.5mm in width, giving axial ratio around 0.7. Spirotheca with three layers, tectum as well as outer and inner tectorium. Septa straight. Proloculi are less than 0.1mm in diameter.
Nankinella sp. Figure 3.7–3.9
Description.—Test median, elliptical with rounded periphery, slightly convex lateral sides and closed umbilici. Tests of the inner whorls are subrhomboidal with narrowly pointed periph- ery. Adult tests develop 6–7.5 whorls, with length of 1.3– 1.4mm, width of 1.5–1.9mm, giving axial ratio around 0.7. Spirotheca are composed of tectum, upper and lower tectorium. Septa straight. Proloculi are less than 0.1mm in diameter.
Remarks.—The present species is similar to N. orientalis except for the much smaller size and the elliptical shape of the adult tests.
Results
The Xishancun fauna from the northern Tengchong Block is composed of Chusenella riagouensis Chen, 1985,
C.cf. minuta Skinner, Nankinella cf. mingshanensis Sheng and Rui, N. orientalis Miklukho-Maclay, 1954, and Nankinella sp. (Fig. 3). Among them, Chusenella riagouensis is the dominant species. Until now it was only found in the Xainza area of Tibet (Zhang et al., 1985). It is distinct fromother Chusenella species in its small size. This species occurs in the Zhaopu (Zhuobu) Formation of the Xainza area and indicates an age of Roadian to Capitanian. Nankinella mingshanensis Sheng was first found in the upper Permian in Jiangxi (Sheng and Rui, 1984) and later discovered in the Guadalupian Maokou Formation in Guizhou and Yunnan of South China (Zhang et al., 1988; Zhou, 1998). Nankinella orien- talis is widely distributed in the Changhsingian strata of North and South China (Geobiodiversity Database, Fan et al., 2013) and ranges down to the Guadalupian strata in Azerbaijan (Ruzhentsev and Sarycheva, 1965). These data suggest an age of Roadian– Capitanian for the Chusenella-Nankinella fauna. The Shuangheyan fauna from the southern Tengchong Block
consists of four species: Chusenella mingguangensis Shietal., 2008, Schwagerina chihsiaensis (Lee, 1931), Schwagerina pseu- docompacta Sheng, 1956, and Staffella sp. (Fig. 4). Chusenella mingguangensis is the dominant element here, and is also prolific in the previously reported Wordian–Capitanian Caiyuanzi fauna (Shi et al., 2008). This species is rather unique for its small size and intensely coiled inner whorls. So far it has only been discovered in the Tengchong Block. Schwagerina chihsiaensis was first discovered in the Kungurian Chihsia limestone in South China
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