Xianyuechelys yingliangi: a new nanhsiungchelyid turtle from the Late Cretaceous of Ganzhou Basin, China

Nanhsiungchelyidae is a group of large Pan-Trionychia that lived in North America and Asia during the Cretaceous. Despite a long research history, their taxonomy and internal nodes are still controversial. Here, we erect a new taxon, Xianyuechelys yingliangi gen. et sp. nov., from the Upper Cretaceous Lianhe Formation of Ganzhou Basin, China. Xianyuechelys yingliangi is attributed to Nanhsiungchelyidae based on its carapace being covered by a sculpturing of large pits. However, the new species also possesses an unique combination of characteristics among nanhsiungchelyids such as a wide, crescentic nuchal, absence of a pair of anterolateral processes, and the fourth and fifth vertebral scutes that contact at a point. The holotype is a juvenile or sub-adult based on the incomplete ossification of carapace, but its morphological characteristics can mostly be regarded as taxonomically informative rather than ontogenetic in origin. Phylogenetic analysis suggests Xianyuechelys yingliangi forms a monophyletic group with Nanhsiungchelys spp. and Anomalochelys angulata, supported by two unambiguous synapomorphies: wide vertebral scutes and wide neurals. The phylogenetic analysis also suggests Basilemys, Jiangxichelys and 'Zangerlia' form a monophyletic group. Our new finding increases the known diversity of nanhsiungchelyids in southern China.