Article: The cranial anatomy of the captorhinid reptile Labidosaurikos meachami from the Lower Permian of Oklahoma
Study of Labidosaurikos meachami, from the Lower Permian Hennessey Formation (Sumner Group) of north-central Oklahoma, reveals the presence of over thirty new cranial characters not present in single-tooth-rowed captorhinids and Captorhinus aguti. However, it is uncertain if these new characters represent autapomorphies of L. meachami because the skulls of all other large, multiple-rowed captorhinids are poorly known; many of these characters may instead diagnose subclades of multiple-tooth-rowed taxa within Captorhinidae. A suite of skeletal features, including the presence of tooth plates, prominent tooth wear, and the morphology of the skull roof, suggests strongly that L. meachami was herbivorous. Propaliny was probably a significant component of the feeding mechanism.Phylogenetic analysis of the interrelationships of the well known North American captorhinids indicates that Labidosaurikos meachami is more closely related to the large, single-rowed Labidosaurus hamatus than it is to Captorhinus aguti. The sister-group relationship between Labidosaurikos meachami and Labidosaurus hamatus is supported by fifteen synapomorphies, and is the most robust clade within Captorhinidae. This relationship supports the hypothesis that multiple rows of teeth evolved independently at least twice among captorhinids. Eocaptorhinus laticeps, recently assigned to the genus Captorhinus as ' Captorhinus sp.', is formally recognized as Captorhinus laticeps (new combination). The phylogenetic analysis indicates that C. laticeps and C. aguti form a clade, identified here as Captorhinus, that is the sister group of the L. meachami-L. hamatus clade.