New evidence for an old acquaintance: Neoprocoela edentata from the Oligocene of central Patagonia is the oldest species of Nannophryne (Anura: Bufonidae)

Abstract

Neoprocoela edentata is a fossil anuran collected in Scarritt Pocket, Patagonia, Argentina. This locality provided the first described pre-Neogene batrachofauna of South America, which is also one of the few known to include representatives of extant taxa. Neoprocoela edentata shows an unusual combination of characters, and it has alternatively been related to Bufonidae or to a polyphyletic assemblage including Calyptocephalellidae and Telmatobiidae. In this paper, we redescribe the single specimen of N. edentata, complementing the examination with micro-CT scan reconstructions, and expanding its original description. This results in a combination of character states unique for Bufonidae, allowing us to confidently assign N. edentata to this family. Then, we performed a total evidence phylogenetic analysis, including molecular and osteological data, to evaluate the phylogenetic relationships of N. edentata within Bufonidae. This species was recovered in a strongly supported clade with the extant genus Nannophryne; thus, Neoprocoela is consider a junior synonym of this genus, retaining edentata as a valid species. Finally, considering the geographic and stratigraphic provenance of the fossil remains, we discuss its value as evidence of the early evolution of South American toads and as an absolute-age calibration point, something relatively unusual for neobatrachian fossil species of that age.