A fossil mud turtle (Testudines, Kinosternidae) from the early middle Miocene (early Barstovian) of New Mexico

ABSTRACT

The nearly complete skeleton of a mud turtle, Kinosternon skullridgescens, n. sp., is described from Santa Fe County, New Mexico. The specimen was collected from the early middle Miocene, early Barstovian, Skull Ridge Member of the Tesuque Formation (16.0–14.9 Ma) and is one of the oldest and most complete fossil representatives of the genus Kinosternon. Phylogenetically, the new taxon is placed on the stem of the flavescens group in conjunction with the extinct Kinosternon pojoaque from the late Barstovian of New Mexico. In addition to the flavescens group, K. skullridgescens shares morphological similarities with members of the subrubrum group (of North America), as well as with Kinosternon herrerai (from gulf drainages of eastern Mexico). Close proximity of the fossils K. skullridgescens and K. pojoaque to Mexico suggests that a small-plastroned ancestor of the extant taxa K. herrerai, Kinosternon angustipons (from lower Central America), and Kinosternon dunni (from northwestern South America) could have dispersed from North America into Central America by the middle Miocene (Barstovian). Phylogenetic results based on morphology suggest that the taxon Kinosternon steindachneri (formerly Kinosternon subrubrum steindachneri) be reinstated at the species level.

ACKNOWLEDGMENTS

Many thanks to G. S. Morgan (NMMNHS) for helpful discussions and e-mail correspondences on the stratigraphy of New Mexico fossil localities and loan of NMMNH 63853; C. Mehling and E. S. Gaffney (AMNH) for loans and allowing me to prepare and study FAM fossils discussed here; R. Hulbert and J. Bloch (FLMNH) for discussions and loan assistance; C. Manz and A. Rincon (FLMNH) for discussions; S. Lad for discussions and assistance; A. Hastings, R. Hulbert, and E. Woodruff (FLMNH) for discussions and assistance with bootstrap analysis; J. Iverson (Earlham College) for e-mail correspondences; J. O’Sullivan (University of Tampa) for assistance in X-ray imaging of FAM 9090; K. Krysko and M. Nickerson (FLMNH) for loans of modern turtle specimens; E. Simons, C. May, and B. Morris for donations of modern specimens; J. Waldrop for donations of fossil specimens; S. Chester (YPM) for travel and lodging assistance; D. Brinkman, T. Lyson, and S. Modesto for comments that improved the manuscript. This is University of Florida Contribution to Paleobiology no. 644.

Handling editor: Sean Modesto