Vertebrate paleontology of the Cloverly Formation (Lower Cretaceous), III: a new species of Albanerpeton, with biogeographic and paleoecological implications

Abstract

ABSTRACT We describe a new species of the albanerpetontid amphibian Albanerpeton from three localities in the Lower Cretaceous Cloverly Formation of Wyoming, U.S.A. Radiometric dates between ∼111–112 Ma indicate it is slightly younger than A. arthridion from the Antlers Formation. The new species is diagnosed on a pair of fused frontals that possess a unique combination of characters, mixing plesiomorphic features of the internasal process with a more derived overall shape and proportions. Referred material includes premaxillae, maxillae, dentaries, atlantes, ‘axes,’ trunk vertebrae, humeri, and an ilium. Phylogenetic analyses place the new species near the base of Albanerpeton sensu lato but without fully resolving its position. The inclusion of Shirerpeton and Wesserpeton within this clade opens up the possibility that these genera might be incorporated into Albanerpeton, or that a number of species formerly assigned to Albanerpeton might receive new generic assignments. By including several informal species in our analysis, it becomes clear that character distributions are more homoplastic and that past genus typologies are probably less secure. We assign the new species to Albanerpeton conservatively, pending further phylogenetic study. The Cloverly Albanerpeton is found in unambiguously aquatic deposits, suggesting that the animal lived near these settings for at least part of its life. This is a common habitat for Mesozoic albanerpetontids, unlike the karst-dominated, often drier, deposits in which Cenozoic species are typically found. Despite the recent discovery of a probable arboreal species, it is likely that albanerpetontids inhabited a range of habitats throughout their evolutionary history.