Pleistocene anurans from Cathedral Cave, Nevada: Implications of morphological variation for the identification of isolated and underutilized skeletal elements

Anuran remains from the Room 2 excavation at Cathedral Cave, Nevada, USA, provide insight into the Pleistocene history of anurans in the Great Basin of the western United States. We identified recovered specimens as Pipanura, Neobatrachia, Bufonidae, Ranidae, Scaphiopodidae, and Spea. Identified elements included maxillae, an atlas, presacral vertebrae, sacral vertebrae, urostyles, sacrourostyles, and a tibiofibula. Taxonomic identifications were based on detailed morphological evaluations that considered a broad comparative pool of skeletal elements from North American frog populations. That approach minimized the use of geography as an unstated criterion for specimen identification and resulted in identifications above the species level, reflecting the considerable, overlapping variation that we documented in portions of the skeletal system of North American anurans. Although such observations are not novel for all skeletal elements that we evaluated, the variation that we describe in detail across all evaluated elements is indicative of broader challenges in species- and generic-level identification of anuran remains from Quaternary deposits. Nevertheless, ilia referred to Bufonidae were represented by two distinct morphotypes, suggesting the possibility of multiple species of that taxon in the fossil assemblage and in contrast to the lack of bufonids around the cave today. Regardless of the overall taxonomic resolution in our study, the assemblage indicates some level of regional, taxonomic stability over roughly 150,000 years. More importantly, our study reinforces the idea that higher taxonomic level identifications based on morphology and incorporating intra- and interspecific variation (while minimizing geographic inference) can inform our understanding of biogeographic patterns.