The Anisian (Middle Triassic) brachiopods from the southern Qilian Mountains, north‐western China

Abstract

The Anisian (Middle Triassic) witnessed the diversification of brachiopods after the Permian–Triassic extinction. The Anisian brachiopod fauna from the southern Qilian Mountains in north‐western China has the highest taxonomic diversity at species level among coeval faunas worldwide. Nevertheless, many taxa from this remote region remain poorly defined, and therefore require emendation. Here we describe 23 species (including two uncertain species) in 15 brachiopod genera based on well‐preserved carbonate and silicified specimens collected from the Anisian Dajialian and Qieermagou formations in Tianjun, southern Qilian Mountains. Two new genera (Crenulatomargus, Tianjunospina) and six new species (Costirhynchopsis xui, Crenulatomargus terebratuliformis, Schwagerispira elegans, Lepismatina? inusitata, Tianjunospina junheensis, Qilianoconcha circularis) are erected. The diagnoses of Triasorhynchia, Yangkongia, Sinucostella, Aequspiriferina, Qilianoconcha and Parantiptychia are emended. Also, the genus Eoantiptychia and the family Triasorhynchiidae are regarded as junior synonyms of Qilianoconcha and Tetrarhynchiidae, respectively. After systematic description and taxonomic emendation, 56 species (including seven uncertain species) in 26 genera are confirmed in the southern Qilian brachiopod fauna. Network analysis of 14 brachiopod faunas worldwide shows that six groups were detected during the Anisian (Qingyan, southern Qilian – western Qinling, Himalaya – northern Siberia, central Qinghai, New Zealand, and Europe/western Tethys). Compared with those from the western Tethys, the eastern Tethyan faunas are less allied to each other. Except for the assemblage from the adjacent western Qinling area, other coeval faunas have much lower affinities with the Qilian fauna.