The hopping dead: Late cretaceous frogs from the middle – late campanian (judithian) of western North America

Abstract

The Mesozoic record for anurans (i.e., crown-clade frogs) in North America extends from the Early Jurassic to terminal Cretaceous. Here we review the record for middle – late Campanian (= Judithian North American Land Mammal Age and ca. 79–73 million years ago) anurans from the North American Western Interior. Judithian anuran fossils (mostly isolated bones) are known from dozens of localities in ten formations, distributed from southern Alberta and Saskatchewan, Canada, southwards into southern Texas, USA. Based largely on distinctive cranial bones, we recognize six or, perhaps, seven species: three named species (Scotiophryne pustulosa, Hensonbatrachus kermiti, and Tyrrellbatrachus brinkmani); three potentially diagnosable species (Theatonius n. sp. and two unnamed new genera and species); and one Scotiophryne-like species (cf. Scotiophryne sp.). On the basis of distinctive maxillae, we also recognize three broad groups of morphs, each of which likely contains multiple, as yet unrecognizable taxa. The familial affinities of those taxa and morphs are uncertain, due to the fragmentary nature of the available specimens. We provisionally recognize two geographic assemblages of Judithian anurans: a northern one encompassing Alberta, Canada and Montana, USA and a southern one encompassing Wyoming, Utah, and New Mexico, USA. The Judithian anuran record contains some species restricted to that interval and other taxa having longer temporal ranges and it documents the first appearances of edentulous anurans (T. brinkmani and Theatonius n. sp.) in the Northern Hemisphere.