Taxonomy of ?Gyposaurus? sinensis Young, 1941 from the early Jurassic Lufeng Formation of Yunnan Province, southwestern China

WANG, YA-MING; YOU, HAI-LU; ALEJANDRO OTERO; WANG, TAO

Calgary

Congreso; 77° Annual Meeting of the Society of Vertebrate Paleontology; 2017

Society of Vertebrate Paleontology

Basal sauropodomorphs represent the first radiation of herbivorous dinosaurs, which were diversified across all continents from the Late Triassic to Early Jurassic. The Lower Jurassic Lufeng Formation in Lufeng Basin of Yunnan Province, southwestern China has yielded numerous dinosaurs, most of which have been referred to basal sauropodomorphs, including Lufengosaurus huenei Young 1941, Gyposaurus sinensis Young 1941, Lufengosaurus magnus Young 1942, Yunnanosaurus huangi Young 1942, Yunnanosaurus robustus Young 1951, Jingshanosaurus xinwaensis Zhang and Yang 1994, Chuxiongosaurus lufengensis Lü et al 2010 and Xingxiulong chengi Wang et al. 2017. However, the taxonomic status of some of them has been debated ever since, including ?Gyposaurus? sinensis, the most debated Lufeng basal sauropodomorph taxon. Here we redescribe the holotype specimens of ?Gyposaurus? sinensis (IVPP V26, V27) and demonstrate that the material can be referred to a juvenile Lufengosaurus huenei. Both the unfused dorsal vertebrae and the bone histology of the fibula suggest that ?Gyposaurus? sinensis was a young juvenile. In addition, the morphology of the holotype specimens of ?Gyposaurus? sinensis strongly resembles that of Lufengosaurus huenei: they share coarsely serrated teeth, a slender scapula with a symmetrical distal end that lacks a posteroventral process, a humerus with a convex proximal end and a sinuous proximolateral margin of deltopectoral crest, and similar proportions of humeral /femoral length as well as tibial/femoral length. Preliminary phylogenetic analysis, in which ?Gyposaurus? sinensis and Lufengosaurus huenei were included as separate terminal units, recovered ?Gyposaurus? sinensis as part of a polytomy with Lufengosaurus huenei,Glacialisaurus, and Coloradisaurus, indicating a close relationship between these taxa. Therefore, we consider ?Gyposaurus? sinensis is a junior synonym of Lufengosaurus huenei. However, the status of the referred material of ?Gyposaurus? sinensis (such as IVPP V43, V45 and V95) still needs further investigation.