FIRST RECORD OF THE FAMILY RHINOPHRYNIDAE FROM THE OLIGOCENE OF EASTERN NORTH AMERICA

The anuran family Rhinophrynidae is today represented by a single species of fossorial frog restricted to southernmost Texas and Central America. While three extinct genera are known from the Jurassic (Rhadinosteus) and Eocene (Chelomophrynus, Eorhinophrynus), the extant genus Rhinophrynus is known from only two sites: the latest Eocene (Chadronian) of Saskatchewan and the Pleistocene of Mexico. Here, we provide the first record for the Rhinophrynidae for both the Oligocene and from eastern North America. We have so far identified humeri, vertebrae, and ilia that are referable to Rhinophrynus from one of the earliest terrestrial vertebrate sites in Florida (Brooksville Quarry 1A; late Oligocene). In addition to Rhinophrynus, we have found anuran fossils referable to the families Hylidae, Eleutherodactylidae, Bufonidae, and Ranidae. Finding Rhinophrynus in the late Oligocene of Florida fits with previous findings from the herpetological diversity (Anguidae, Helodermatidae, Xantusiidae) that suggest an affinity with western North America and drier conditions than found today. The Rhinophrynus recovered from the Brooksville Quarry 1A exhibits many similarities to the extinct R. canadensis from the Eocene, including that both are smaller than the extant R. dorsalis. In addition, their ilia have a less gracile dorsal prominence than found in R. dorsalis. The size and shape of the vertebrae vary between R. dorsalis, R. canadensis, and the Brooksville material. The neural arches of R. dorsalis flare laterally at their connection to the centrum, whereas this is absent in the Brooksville specimens. In addition, the Brooksville specimens have a tear-drop shaped neural canal whereas that of R. dorsalis is more rectangular. A Rhinophrynus humerus from Brooksville has been distinguished from R. dorsalis by having a crest extending from the ulnar epicondyle that runs parallel to the long axis (rather than curving posteriorly) and a more robust and relatively longer paraventral crest. The late Oligocene herpetological community at Brooksville is concordant with previous suggestion of large-scale reorganization of the North American herpetofauna in the early Oligocene. However, this diversity in northern Florida appears to have shifted in the early Miocene as Rhinophrynus does not occur at nearby Thomas Farm site.