Taxonomic status of the Early Permian Helodectes paridens Cope (Diadectidae) with discussion of occlusion of diadectid marginal dentitions

Helodectes paridens Cope ( It was based on a poorly preserved jaw and adjoining elements of the left side of a small skull that was believed to possess a double row of marginal teeth. Thorough preparation of the holotype reveals that one row represents a normal complement of rooted premaxillary and maxillary teeth and the other a row of crowns derived from the opposing teeth of the absent dentary. There are no detectable differences from the commonly encountered Diadectes of the same age, and Helodectes should be regarded as a junior synonym of that genus. As the holotype of H. paridens exhibits no features on which to base specific identity, it is referred to as Diadectes sp. The same interpretation undoubtedly applies to the double row of premaxillary-maxillary marginal teeth in the lost and only known specimen of the equally small holotype of H. isaaci Cope (1880) from the same locality as H. paridens. A second example of Helodectes-Wks, dental preservation is described in the opposing upper and lower jaw elements in a very small Diadectes specimen from the Early Permian of Texas.