Jeholotriton paradoxus (Amphibia: Caudata) from the Lower Cretaceous of southeastern Inner Mongolia, China

Abstract

Listen

Translate article

ABSTRACT A fossil salamander is described based on specimens from a Lower Cretaceous deposit near Ningcheng, Inner Mongolia, China. Recently reported as Jeholotriton paradoxus, this form represents a neotenic salamander as indicated by larval features such as external gills, tooth-bearing coronoids, pterygoids with anteromedially oriented anterior processes, and underdeveloped maxillae, in combination with adult features such as extensive medial contact of the nasals and posteriorly directed tooth rows in the palate. This taxon is distinguished from other Mesozoic salamanders by having 15–16 presacrals, proximally expanded unicapitate ribs, vomers with large tooth patches anteriorly and longitudinal dentigerous bars posteriorly, large nasals with no anterior notch, frontals with no anterolateral extension, premaxillae with distinct alary processes, short transverse processes on the vertebrae, and phalangeal formulae of 2-2-3-2 for the manus and 2-2-3-3-2 for the pes. Including Laccotriton, Liaoxitriton, Sinerpeton and Chunerpeton, five taxa of Mesozoic salamander have now been found in China. Jeholotriton has especially well-preserved impressions of articulated skeletons, a type of preservation that is uncommon in Mesozoic strata throughout the world and provides important anatomical details of this early salamander. The great diversity of fossil salamanders from the late Mesozoic of northeastern China implies that East Asia was an important center for the early evolution of urodeles.