Nothorthis Ulrich and Cooper, 1938

Zhan, Renbin & Jin, Jisuo, 2005, Brachiopods from the Middle Ordovician Shihtzupu Formation of Yunnan Province, China, Acta Palaeontologica Polonica 50 (2), pp. 365-393 : 374

Genus Nothorthis Ulrich and Cooper, 1938 Nothorthis perplexa Xu and Liu, 1984

Fig. 8L, O; Table 4.

Nothorthis? perplexa sp. nov.; Xu and Liu 1984: 171, pl. 11: 22–25. Nothorthis perplexa Xu and Liu, 1984 ; Zhan and Jin in press.

Material.—Two dorsal internal moulds.

Discussion.—The minute, slightly transverse shells of Nothorthis perplexa are rare but well preserved together with the large shells of Martellia and Leptellina . The brachiophores are rod−like with widely divergent brachiophore bases ( Fig. 8L 1 , L 2 ). The cardinal process is small, ridge− or knob−like. The multicostellae are somewhat less numerous than in other species of Nothorthis . These characters are essentially identical to those of the same species from the Dashaba Formation (see Zhan and Jin in press).

Figures

Fig. 1. Location map of the study area. A. Map of China, with the South China palaeoplate outlined by thick line; inset box enlarged as B. B. The border region between Yunnan, Guizhou and Sichuan provinces; inset enlarged as C. C. Detailed map of the Shizigou Valley section near the Weixin County town, with the fossil locality marked by solid triangle.

Fig. 2. Middle Ordovician sedimentary facies on the Yangtze Platform, South China palaeoplate (modified from Zhang et al. 2002), with three fossil localities discussed in the text: 1, Shihtzupu Formation at Shizigou Valley near the Weixin County town, Yunnan Province; 2, Type area of Shihtzupu Formation at Donggongsi, Zunyi, Guizhou Province; 3, Dashaba Formation at Shuanghe, Changning, Sichuan Province.