Mesozoic anurans from Liaoning Province, China, and phylogenetic relationships of archaeobatrachian anuran clades

ABSTRACT

Two Jurassic–Cretaceous anurans are described based on well-preserved specimens from the lower part of the Yixian Formation, western Liaoning Province, northeastern China. One specimen, from the Heitizigou site, documents a new genus and species, and the second, from the Sihetun site, is the holotype and only known specimen for the recently named Callobatrachus sanyanensis. Phylogenetic relationships of the major archaeobatrachian anuran clades are investigated with incorporation into the analysis of selected (well-established) early fossil taxa. The new taxon named and described in this paper is placed as the representative of a distinct archaic anuran clade, and Callobatrachus is considered to be an ingroup member of the Discoglossidae, constituting the earliest record of the family from Asia. The oldest known fossil anuran, Prosalirus from the Early Jurassic of Arizona, is grouped with Notobatrachus as sister taxa, and the two together form the most basal clade of Anura. Contradicting the widely accepted Leiopelmatidae–Discoglossidae sistergroup relationship, new evidence places the Leiopelmatidae as the most basal extant familial group and the sister group to other archaeobatrachian clades. The relationships and classification of the major archaic anuran clades are discussed, based on the phylogenetic results of this study.