A neotenic salamander, Jeholotriton paradoxus, from the Daohugou Beds in Inner Mongolia

Over the past 10 years, there has been a wealth of discoveries of fossil salamanders from the Jehol Biota in northern China. These specimens have revealed many new species in addition to establishing probable divergence times and relationships among modern salamander families. Among these are numerous specimens of a neotenic species Jeholotriton paradoxus. In this study, we focused on this particular salamander species because its classification still remains enigmatic. The aim of this research was to determine the relationship of Jeholotriton with respect to other Jehol salamanders as well as modern salamander families. Although Jeholotriton has been described in previous studies, the discovery of new specimens and increasing knowledge of other Mesozoic salamanders has allowed for a more through description of the genus. Jeholotriton is known only from the Daohugou locality in Ningchen, south-eastern Inner Mongolia. It may be close to the base of the modern Urodele radiation, and might provide evidence of their transition from putative ancestors in the Permo-Triassic. We discovered that the fossil Kokartus (family Karauridae) and the living hynobiids (the most primitive group of modern salamanders) Ranodon sibiricus and Hynobius maculosus, as well as Dicamptodontidae tenebrosus all share some similarities with Jeholotriton. However, conclusive relationships could not be confidently established because of the unique combination of mature and larval characteristics in Jeholotriton.