Taxonomic revision of the Triassic brachiopod genus Angustothyris and its phylogenetic implications

Abstract Angustothyrididae Dagys, 1972 is a key group of terebratulide brachiopods, because it exhibits characteristics bridging the two major suborders, Terebratulidina and Terebratellidina, and could represent an evolutionary link between them. However, the taxonomy of its type genus, Angustothyris Dagys, 1972, has remained poorly understood. Our restudy of specimens from the Middle Triassic of Hungary and southwestern China, including material from the type localities, reveals that the specimens previously assigned to Angustothyris actually represent multiple genera. This indicates that the diversity of this group has been underestimated, leading us to establish Balatonithyris new genus, Qianothyris new genus, and Angustothyris aszofoensis new species. The long teloform loop in Qianothyris n. gen. fills a morphological gap between short-looped terebratulidines and long-looped terebratellidines, supporting a Late Permian–Triassic origin of the terebratellidines from the Angustothyrididae. The morphological evidence, however, conflicts with molecular data that suggest an earlier divergence between the two suborders. This contradiction implies that either the Angustothyrididae is not the direct ancestor of terebratellidines, or that the terebratellidines are a polyphyletic group with multiple evolutionary origins. UUID: http://zoobank.org/b19352c0-8352-4bba-a0b1-a95963f3da38