Reassessment of ‘Gyposaurus’ sinensis Young, 1941 (Dinosauria: Sauropodomorpha) from the Early Jurassic Lufeng Basin, Yunnan Province, China

Abstract

The Early Jurassic Lufeng Formation of Yunnan Province, southwestern China, has yielded a rich assemblage of early-branching sauropodomorphs. The syntype series of ‘Gyposaurus’ sinensis Young, 1941, represented by two skeletons from the Shawan Member of this formation, was the second-earliest named taxon after Lufengosaurus huenei Young, 1941. However, its taxonomic status has been debated ever since, owing to the invalidity of the genus ‘Gyposaurus’. Here, we provide a detailed redescription of the remaining syntype specimens of ‘Gyposaurus’ sinensis, including V26 and V27, which comprise almost complete postcranial skeletons. Both the unfused vertebrae and the osteohistology of the syntype specimens suggest that they are immature individuals. The morphology of the skeletons, especially that of the scapula, humerus, ilium, and femur of ‘Gyposaurus’ sinensis, is more similar to that of Lufengosaurus huenei than to that of other non-sauropodan sauropodomorphs. A phylogenetic analysis, in which ‘Gyposaurus’ sinensis and Lufengosaurus huenei were included as separate terminal taxa, recovered ‘Gyposaurus’ sinensis as part of a polytomy with Lufengosaurus huenei and Glacialisaurus, also indicating a close relationship between these taxa. Therefore, we suggest that ‘Gyposaurus’ sinensis is probably referable to a junior synonym of Lufengosaurus huenei.