Spiriferide brachiopods from the Famennian (Late Devonian) Hongguleleng Formation of western Junggar, Xinjiang, northwestern China

Junggar is one of the most important areas in the study of the Upper Devonian and Lower Carboniferous in the Junggar-Hinggan Stratigraphic Region. Nevertheless, abundant benthic fossils await modern taxonomic studies. In this paper, six genera and eight species of Famennian spiriferide brachiopods are described from the Duguer Member and its equivalents of the Hongguleleng Formation in western Junggar, adding new data to the Rugaltarostrum Subassemblage of the “Palaeospirifer”-Megalopterorhynchus Brachiopod Assemblage of this area. Five previously recognized species within this subassemblage are revised, including: Cyrtospirifer junggarensis F.M. Zhang [now Ulbospirifer? junggarensis (F.M. Zhang)]; Tenticospirifer tenticulum transversus F.M. Zhang [now Cyrtospirifer transversus (F.M. Zhang)]; Tenticospirifer koketekensis F.M. Zhang [now Cyrtospirifer koketekensis (F.M. Zhang)]; Mucrospirifer quadratus F.M. Zhang (now “Mucrospirifer” quadratus F.M. Zhang); and Mucrospirifer bouchadi (Muir-Wood) (now Tylothyris cf. novamexicana Stainbrook). Three additional species, Cyrtiorina houi n. sp., Goungjunspirifer sinicus F.M. Zhang, and Cyrtospirifer procumbens Simorin in Litvinovich et al., are described. Ulbospirifer? junggarensis and Goungjunspirifer sinicus are characterized by a prismatic layer. Cyrtiorina houi shows a moderately high and triangular ventral interarea, with delthyrium covered by pseudodeltidium with a rounded foramen. Cyrtospirifer procumbens can be distinguished from other species of this genus by its shallow, clearly limited sulcus with prominent primary plications, and high ventral interarea. Cyrtospirifer transversus has an alate to subpentagonal outline. Cyrtospirifer koketekensis has rounded and distinct flank plications. The ventral delthyrium of “Mucrospirifer” quadratus is covered by a pseudodeltidium. Tylothyris cf. novamexicana develops an angular sulcus in cross-section. Comparisons with the coeval brachiopod faunas from various regions indicate that, biogeographically, western Junggar has a close relationship with the Tarbagatai Mountain Range, northeastern Kazakhstan, central Kazakhstan, and Karaganda Basin, and a certain affinity with North America.