The skeleton of a baurioid therocephalian therapsid from the Lower Triassic ( Lystrosaurus Zone) of South Africa

On the basis of a single, virtually complete specimen of a baurioid (“scaloposaur”) therocephalian, the first full reconstruction of a member of this group is given. It shows that these therapsids were very mammal-like in their proportions, with relatively long limbs, attenuated lumbar ribs, and a highly reduced tail. The specimen is referred to Regisauridae, indet. The degree of differentiation of the axial skeleton is similar to that found in cynodont therapsids, although the head was probably capable of less dorso-ventral movement at the occipito-atlas joint, and there is evidence for a greater degree of lateral undulation of the trunk in the lumbar region. The shoulder girdle was probably highly mobile. The structure of the pelvis and hindlimb supports the hypothesis that the primitive therapsid hindlimb could operate in either a sprawling mode, or in a more advanced, parasagittal mode facultatively. The lack of periosteal bone over the ends of the centra and other bones, and the open nature of the sutures between the centra and neural arches, and between the centra and the lumbar and sacral ribs, support the view that ‘scaloposaurs’ such as this were immature specimens.