Pseudospiriferina pinguis Yang and Xu, 1966

Sun, Zuoyu, Hao, Weicheng, Sun, Yuanlin & Jiang, Dayong, 2009, Silicified Anisian (Middle Triassic) spiriferinid brachiopods from Guizhou, South China, Acta Palaeontologica Polonica 54 (1), pp. 61-68 : 65

Pseudospiriferina pinguis Yang and Xu, 1966

Fig. 4 .

1966 Pseudospiriferina pinguis sp. nov.; Yang and Xu 1966: 45, pl. 5: 5; pl. 6: 1.

1974 Pseudospiriferina cf. pinguis Yang and Xu, 1966 ; Liao and Sun 1974: 352, pl. 184: 11–14.

1978 Pseudospiriferina pinguis Yang and Xu, 1966 ; Feng and Jiang 1978: 292, pl. 104: 5.

Material.—7 articulated shells and 4 dorsal valves.

Dimensions.—L = 15.5 mm; W = 19.0 mm; H = 12.0 mm (GMPKU−P−6168, Fig. 4A–D ).

Description.—Shell medium−sized, strongly ventribiconvex, with subcircular outline and rounded cardinal extremities. Greatest width attained near midlength. Anterior commissure uniplicate. Ventral interarea moderately high, apsacline. Beak relatively stout, slightly incurved. Delthyrium open, its width attaining about one−third of the hinge line. Ventral sulcus, gently developed, only slightly wider than interspaces between costae, occasionally with weak median costa. Dorsal fold low, slightly higher than costae on flanks. Shell ornamented on flanks with strong costae, rounded in cross

16

14

) 12

mm

(

Length 10 8

6

10 15 20 Width (mm)

section. Concentric lamellae crowded near the anterior margin, commonly about four lamellae per 1 mm.

Remarks.— Pseudospiriferina pinguis Yang and Xu, 1966 is characterized by subcircular shell outline, strongly biconvex shell with crowded concentric lamellae near its anterior margin. Our material generally agrees with these features as observed on the holotype by Yang and Xu (1966). However, some specimens of the studied collection display variation especially in the relatively transverse outline and larger size. Stratigraphic and geographic distribution.—Guanling Formation, Anisian, Machangping, Fuquan, central Guizhou, and Xinmin, Panxian, western Guizhou, China.

Figures

Fig. 4. Spiriferinid brachiopod Pseudospiriferina pinguis Yang and Xu, 1966 from the bed Cy 3 of the Yangjuan−Chupiwa section, near Chupiwa village, Xinmin District, Panxian County, Guizhou, China. Complete shell GMPKU−P−6168, in ventral (A), dorsal (B), posterior (C), and lateral oblique (D) views. Scale bars 2 mm.