Shen Shuzhong (沈树忠)

Paleobiogeographical extinction patterns of Permian brachiopods in the Asian-western Pacific region

Abstract Spatial and temporal variations in biological diversity are critical in understanding the role of biogeographical regulation (if any) on mass extinctions. An analysis based on a latest database of the stratigraphic ranges of 89 Permian brachiopod families, 422 genera, and 2059 species within the Boreal, Paleoequatorial, and Gondwanan Realms in the Asian–western Pacific region suggests two discrete mass extinctions, each possibly with different causes. Using species/family rarefaction analysis, we constructed diversity curves for late Artinskian–Kungurian, Roadian–Wordian, Capitanian, and Wuchiapingian intervals for filtering out uneven sampling intensities. The end-Changhsingian (latest Permian) extinction eliminated 87–90% of genera and 94–96% of species of Brachiopoda. The timing of the end-Changhsingian extinction of brachiopods in the carbonate settings of South China and southern Tibet indicates that brachiopods suffered a rapid extinction within a short interval just below the Permian/Triassic boundary. In comparison, the end-Guadalupian/late Guadalupian extinction is less profound and varies temporally in different realms. Brachiopods in the western Pacific sector of the Boreal Realm nearly disappeared by the end-Guadalupian but experienced a relatively long-term press extinction spanning the entire Guadalupian in the Gondwanan Realm. The end-Guadalupian brachiopod diversity fall is not well reflected at the timescale used here in the Paleoequatorial Realm because the life-depleted early Wuchiapingian was overlapped by a rapid radiation phase in the late Wuchiapingian. The Guadalupian fall appears to be related to the dramatic reduction of habitat area for the brachiopods, which itself is associated with the withdrawal of seawater from continental Pangea and the closure of the Sino-Mongolian seaway by the end-Guadalupian.

Late Permian (Lopingian) Gastropods from the Qubuerga Formation at the Qubu Section in the Mt. Everest (Qomolangma) Region, Southern Tibet (Xizang), China

Late Permian gastropod fauna in the Mt. Everest (Qomolangma) region, southern Tibet (Xizang), China is poorly known. This paper describes a small gastropod fauna collected by one of the authors (SSZ) from the upper part of the Qubuerga Formation at the Qubu section. The section is located at about 30 km north of Mt. Everest (Fig. 1). Although a limited number of specimens is available, the fauna is more diverse than all previously reported gastropod faunas (e.g., Yu, 1975) from southern Tibet. Description of the gastropod fauna in the Mt. Everest region adds significant data for understanding the distribution of gastropods during the Late Permian and the paleobiogeographic relationship between the Himalayan and Tethyan regions.  Figure 1 —Map showing the location of gastropods described in this paper (after Shen et al. 2003a) The Permian strata at the Qubu section have been discussed in detail by Shen et al. (2003a). The Qubuerga Formation yielding the gastropod fauna described herein is composed of siltstone interbedded with shale and bioclastic limestone with a thickness of 255.7 m. This formation is divided into two members. The lower member is dominated by bioclastic limestone and siltstone containing abundant brachiopods and bryozoans. The upper member is composed of black shale and micaceous siltstone. Atomodesma -dominated bivalves and gastropods are abundant in the upper part of the lower member and the upper member (Fig. 2).  Figure 2 —Distribution of gastropod species and associated bivalves and brachiopods at the Qubu section (stratigraphic column and brachiopod assemblages after Shen et al., 2003a) A total of eight species in six genera and an indeterminate genus and species of Neritopsidae are recognized. The identified species are Stachella micra Yu, 1975, Bellerophon sp. cf. B. affinis Waagen, 1880, Retispira sp., Euphemites sp. 1, E …