Cranial anatomy of Desmatosuchus haplocerus (Reptilia: Archosauria: Stagonolepididae)

Abstract

New skull material of the Triassic aetosaur Desmatosuchus haplocerus (Archosauria: Stagonolepididae) from the Cooper Canyon Formation (Late Triassic: early Norian) of Texas is described. This is the most complete description of the skull of Desmatosuchus to date, shedding light on the edentulous premaxilla, laterally exposed splenial on the mandible, reduced external mandibular fenestra, dentition (small denticles and wear facets), and variability of the hemispherical fontanelle. The quadratojugal/postorbital contact, a synapomorphy supposedly shared by the Stagonolepididae and Rauisuchia (sensu Parrish), is absent in Desmatosuchus. The interesting convergence in cranial and postcranial morphology of aetosaurs and certain living edentates (armadillos) suggests the possibility of insectivory or omnivory, instead of herbivory as a feeding strategy. This new description is intended to provide detailed information for future studies on the interrelationships of the Stagonolepididae (which are plagued by incomplete material), and their phylogenetic position among the archosaurs.