Fossil frogs from the early Campanian of West Texas, USA, with comments on Late Cretaceous anuran diversity in southern Laramidia

Abstract

A rare early Campanian (Aquilan) assemblage consisting of disarticulated anuran bones is described from the Aguja Formation of West Texas, USA. Many specimens within the assemblage pertain to taxonomically informative elements (maxillae, urostyles, and ilia). Morphological variety among specimens pertaining to each suggests high local species richness comparable with that seen elsewhere among frogs from similarly well-sampled localities of the Late Cretaceous Western Interior. Comparison between environmentally and temporally analogous microvertebrate assemblages in southern Utah, USA, reveals that anurans in both areas exhibit morphological similarities consistent with regionally allied ‘southern’ faunas. Among their differences, one character (dorsal protuberance of the ilium) consistently exhibited among some ilial morphotypes from Utah is conspicuously absent among those of West Texas. Two ostensibly exclusive ilial morphs in West Texas add additional support to the presence of taxonomically segregated, sub-regional populations of anurans in southern Laramidia during early to middle Campanian time.