The postcranial skeleton of the Permian microsaur Pantylus

Abstract

The description of the postcranial skeleton of Pantylus is based on four specimens from the Putnam Formation, Wichita Group, and material from the Clyde Formation, Clear Fork Group, Lower Permian of Texas. The presence of haemal arches, only 24 presacral vertebrae, and an astragalus and calcaneum are reptilian features, but the anatomy of the cervical vertebrae, the absence of trunk intercentra, and the nature of the scales as well as the anatomy of the skull indicate that this genus is a microsaur. The carpals, described for the first time in any microsaur, resemble those of rhachitomous amphibians in having a large proximal centrale. There are four manus digits and five in the pes. Pantylus was apparently a fully terrestrial form, with stout although short limbs. The presence of heavy ventral armor suggests that it dragged itself along the ground, or was a burrowing form. The extensive wear shown by the massive tooth plates indicates a diet of hard-shelled invertebrates or plant food. Pantylus is most clearly related to the Early Pennsylvanian microsaur Trachystegos. Although both genera may be related to the gymnarthrids Cardiocephalus and Euryodus, they are sufficiently distinct to be placed in a separate family.