Covert biases, circularity, and apomorphies: A critical look at the North American Quaternary Herpetofaunal Stability Hypothesis

The North American Pleistocene Herpetofaunal Stability Hypothesis was established in the 1980s based on summary reviews of primary descriptive paleoherpetological literature. The hypothesis posits that North American herpetofaunas essentially were taxonomically and geographically stable throughout the Quaternary. Modern biogeographic distribution of species served as an important criterion for primary identification of the majority of fossil herpetofaunal specimens, rendering the Herpetofaunal Stability Hypothesis circular. Apomorphy-based identifications are an important and well-established alternative to the traditional approach, but are used only rarely within the Quaternary paleontology community. Preliminary applications of the apomorphy-based approach reveal that species-level resolution often is not possible for herpetofaunal remains. Lack of species-level resolution may be a consequence of poor documentation of evolutionary morphology for most herpetofaunal species lineages. Development of adequate skeletal collections and the search for apomorphies in the anatomical systems typically preserved in Quaternary deposits will yield meaningful insights into evolutionary morphology, an enhanced appreciation of Quaternary faunal dynamics, and a greater concordance with modern neontological approaches. Maintenance of traditional methods of identification will yield a false perception of clarity, erroneous interpretations of Quaternary faunal dynamics, and may perpetuate misleading data in Quaternary paleontology as well as other fields that rely on those data.