Anatomical Plasticity in the Snout of Lystrosaurus

Abstract

The skull of Lystrosaurus, characterized by an elongated snout and a scarf premaxilla-nasal suture, differs from the generalized Permian dicynodont form. The sutural relationships of the bones of the Lystrosaurus snout are further investigated here using several anatomical lines of evidence: gross osteology, histological and serial sections, and micro-computed tomography scans. Novel evidence was found for supernumerary bone(s) in the dorsal region of the snout in a few specimens of Lystrosaurus. The developmental and functional implications of this anatomical plasticity are discussed. It is hypothesized that the supernumerary bones may have formed from separate ossification centers of the frontal bone.