A NEW PROCOLOPHONID FROM THE UPPER TRIASSIC OF TEXAS, WITH A DESCRIPTION OF TOOTH REPLACEMENT AND IMPLANTATION

A new procolophonid, Libognathus sheddi, gen. et sp. nov. is reported from thr Cooper Canyon Formation (Dockum Group; Upper Triassic: lower Norian) near Post, Texas. This is the first published description of a n unequivocal procolophonid from the Upper Triassic of the southwester n United States. Some of the distinctive characters of Libognathus are the deep dentary, large anteriorly directed foramen on the lateral de ntary surface, and the forward projecting coronoid. Libognathus provid es a good example of tooth replacement and implantation, which are poo rly known in procolophonids. The implantation is protothecodont, with the teeth set in sockets and firmly anchored by spongy hone of attachm ent. The stages of replacement are of the typical reptilian pattern. L ibognathus is closely related to Hypsognathus from the Passaic Formati on (Norian) of New jersey, and correlative strata in Connecticut and N ova Scotia.