Morphometric Variation in the Red-Cheeked Mud Turtle (Kinosternon cruentatum) and its Taxonomic Implications

Abstract. The Scorpion Mud Turtle (Kinosternon scorpioides) has been recognized by most recent authors to be a single species (3 subspecies) ranging from Tamaulipas, Mexico, to northern Argentina. However, recent molecular analyses have demonstrated that it is not monophyletic, but rather paraphyletic relative to other Neotropical Kinosternon. Based on extensive genetic sampling across the range of this species, a recent paper elevated the 3 subspecies (albogulare, cruentatum, and scorpioides) to species status, confirmed the divergence of Pacific and Atlantic versant populations of K. cruentatum, and recommended that both be given species status. However, the type locality of K. cruentatum is imprecise, making the allocation of the name problematic. Our study sought to determine the provenance of the type using morphometric analysis of specimens from across the range. That analysis demonstrates unequivocally that the type of K. cruentatum was collected on the Atlantic versant, likely from an eastern population. Furthermore, the analysis also revealed that the type of K. mexicanum, previously synonymized with K. cruentatum, was collected from along the Pacific versant. Hence, the name K. cruentatum should be restricted to populations in Atlantic drainages, and the name K. mexicanum should be restricted to Pacific drainages. Our analysis also indicated divergence among the 3 allopatric Atlantic versant populations, but future genetic work will be needed to determine whether they merit taxonomic recognition.