The Origin of the Lungless Salamanders (Amphibia: Plethodontidae)

Abstract

It has been generally accepted that lunglessness in plethodontid salamanders results from a selection for increased ballast in aquatic, Late Cretaceous ancestors that inhabited fast-moving, cool Appalachian mountain brooks. However, late Mesozoic mountain-stream environments consistent with that scenario were probably absent from the region: geological evidence indicates that late Mesozoic Appalachia was a chronically warm, low-elevation, non-montane region with little relief and topography. An alternative hypothesis for the origin of plethodontid salamanders is considered. We suggest that proto-plethodontids may have been only semi-aquatic or terrestrial. Supporting evidence includes a plethodontid-like reliance on cutaneous respiration in certain extant ambystomatid salamanders.