New albanerpetontid amphibians from the albian to Coniacian of Utah, Usa—Bridging the gap

ABSTRACT

Newly discovered fossils described herein from Utah, USA, help fill a sizeable gap in the Cretaceous record of the Albanerpetontidae and provide information on the evolution of the family during the latest Early–middle Late Cretaceous. The geologically oldest record of sympatry among albanerpetontids is in the Mussentuchit Member (latest Albian–earliest Cenomanian in age), Cedar Mountain Formation, where two indeterminate species are recognized based on jaws. The first species primitively resembles geologically older albanerpetontids in the structure of the premaxilla and documents the last appearance of this more primitive premaxillary pattern. The second species closely resembles the North American Campanian–Maastrichtian species Albanerpeton nexuosus in derived premaxillary features, and is the earliest record both of a subgeneric clade that includes all congeners, except A. arthridion, and of a less inclusive clade of Euramerican Upper Cretaceous–Miocene species having premaxillary synapomorphies that reinforced the snout. Albanerpeton cifellii, sp. nov. is named on a premaxilla having an inferred unique pattern of contact with the nasal. This new species is known only from the Smoky Hollow Member (late Turonian in age), Straight Cliffs Formation, and is the oldest member of a subgeneric clade of North American Upper Cretaceous species having a triangular or slit-shaped suprapalatal pit in the premaxilla. Indeterminate albanerpetontid bones are also reported from the above two units and the basal (early or middle Coniacian in age) John Henry Member, Straight Cliffs Formation.