A new hupehsuchian (Reptilia: Ichthyosauromorpha) with widely spaced autopodium from the marine Lower Triassic of South China

Hupehsuchia is a group of marine reptiles from the uppermost Lower Triassic of South China, known for their segmented neural spines covered by dermal ossicles and polydactyl forelimbs. Although five genera and species are currently known for this group, our understanding of their true diversity is limited. In this study, we report a new hupehsuchian, Lentamanusuchus hubeiensis gen. et sp. nov., based on the combination of unique characters in the trunk region and forelimb. These include widely spaced autopodial elements, an extra distal carpal and metacarpal, and a two-layered dermal armour. Phylogenetic analysis recovered the new species as a sister taxon to Parahupehsuchinae within Hupehsuchidae, supporting the gradual addition of extra carpal and digital elements in hupehsuchians. The widely spaced autopodia of Lentamanusuchus hubeiensis represent previously unknown morphologies in hupehsuchians. The wide spacing of the proximal autopodia, along with hyperphalangy, may help smooth the paddle surface to reduce vortices during wrist and proximal digit flexion and extension while swimming. Alternatively, it could result from reduced ossification of manual elements due to diminished muscular control in the manus. https://zoobank.org/urn:lsid:zoobank.org:pub:32503E51-083A-482D-AEFF-4015621A6870