Redescription and phylogenetic reassessment of the enigmatic anuran Eorubeta nevadensis (Amphibia) based on new specimens from ?latest Cretaceous–Paleocene beds of the Sheep Pass Formation, Nevada

Abstract

ABSTRACTEorubeta nevadensis was originally based on a poorly preserved specimen from a well core in Member B of the Late Cretaceous–Eocene Sheep Pass Formation, White Pine County, Nevada. Originally thought to be a member of Leptodactylidae, E. nevadensis was later determined to have uncertain affinities with other anurans. Additional specimens of E. nevadensis recently collected from the outcrop from Members B and C of the Sheep Pass Formation in the Sheep Pass Canyon area, White Pine County, fill many gaps in knowledge about this poorly understood anuran. The new information allows for the first time a phylogenetic analysis of Eorubeta using parsimony. This analysis places E. nevadensis as the sister taxon of Acosmanura. Eorubeta nevadensis was originally reported as early Eocene but is now considered to be ?latest Cretaceous–Paleocene, based on invertebrates and pollen. Thus, although it is uncertain if E. nevadensis spans the Cretaceous–Paleogene boundary, it was at least part of the recovery fauna. The anuran fossil record from this time interval in North America is based on very fragmentary material of mostly uncertain relationships, making E. nevadensis the only nearly complete, well-preserved anuran fossil known. Eorubeta nevadensis, one of the larger fossil anurans recorded, is remarkable for being the only fossil anuran documented from a high-elevation environment, which has been compared to the modern Puna-Altiplano or the Tibetan Plateau.