Revision of the early cretaceous Cordicephalus from Israel and an assessment of its relationships among Pipoid frogs

Abstract

Because many fossil pipoid anurans have been described during the past 35 years from Cretaceous deposits in South America and Africa, it is appropriate to revisit some of the earlier ones to have been discovered, viz., Cordicephalus gracilis, C. longicostatus, and Thoraciliacus rostriceps from Israel. Careful examination of Cordicephalus, based on study of previously, as well as newly, prepared specimens, reveals the existence of only one species. Cordicephalus gracilis is redescribed and compared with Thoraciliacus, and the phylogenetic relationships of these genera to other living and fossil pipoid frogs are investigated in a parsimony analysis. Thoraciliacus is basal to a clade containing Cordicephalus, Palaeobatrachus, and all other living and fossil pipids; however, the placement of Cordicephalus with respect to Palaeobatrachus and Pipidae is unresolved. Both Thoraciliacus and Cordicephalus retain the primitive state for several pipid synapomorphies involving the condition of the vomers, parasphenoid, and presence of a tympanosquamosal bone. In contrast to Thoraciliacus, however, Cordicephalus is characterized by several derived characters including possession of an otic capsule modified to accommodate a Eustachian tube and depressed, fully ossified opisthocoelous vertebrae. Despite their lack of many pipid specializations, both Thoraciliaus and Cordicephalus seem to possess many morphological features that typically are associated with aquatic habits. Among these are possession of a flat skull with a short rostrum, short axial column, and relatively long metapodials.