Was Kungurian Permian captorhinid Eureptile Captorhinikos valensis a Herbivore?

The captorhinid reptile Captorhinikos valensis from the lower Permian Vale Formation of Texas, and the evolution of herbivory in eureptiles

Authors:

Modesto et al

Abstract:

Captorhinikos valensis is a poorly known, multiple-tooth-rowed captorhinid reptile from the Lower Permian Vale Formation of Texas. Our reappraisal of C. valensis reveals it to be a small moradisaurine, exhibiting a maximum of five rows of bullet-shaped teeth in the multiple-rowed region of both the maxilla and the dentary. The slightly radiating organization of the tooth rows distinguishes C. valensis from the parallel arrangement of the tooth rows exhibited by all other moradisaurines. Captorhinikos valensis is also distinguishable from the coeval moradisaurine Labidosaurikos meachami by a more conspicuously denticulated, broader, ‘U’-shaped transverse flange of the pterygoid, a plesiomorphic morphology shared with the large, single-rowed captorhinid Labidosaurus hamatus. Postcranial information is limited to two short series of presacral vertebrae not associated with the cranial materials; open neurocentral sutures are present in one specimen, indicating immaturity at death. We investigated the relationships of C. valensis to other captorhinids by adding it to the data matrix of a previously published analysis that included several moradisaurine captorhinids. A branch-and-bound PAUP analysis discovered a single optimal tree. Whereas a previous analysis of captorhinid interrelationships found the (undifferentiated) genus Captorhinikos to fall outside of a clade composed of L. hamatus and the large moradisaurines, our analysis recovered C. valensis in a clade with the genera Labidosaurikos, Gansurhinus, Moradisaurus, and Rothianiscus (i.e., Moradisaurinae sensu stricto), and Captorhinikos chozaensis as the sister species of a clade that includes L. hamatus and Moradisaurinae s.s.; Captorhinikos chozaensis is no longer classifiable as a moradisaurine (according to our phylogenetic definition for the group), and should be assigned to a new genus. Stratigraphic calibration of our captorhinid phylogeny indicates that moradisaurines evolved by the middle Kungurian (middle Leonardian).