The endocranial cast of the advanced mammal-like reptile Therioherpeton cargnini (Therapsida-Cynodontia) from the Middle Triassic of Brazil.

The prominent characteristics of the endocranial cast of Therioherpeton cargnini are: brain-like appearance, well developed olfactory bulbs, observable cerebral hemispheres with diverging caudal poles and tapering ones, interhemispheric furrow, midbrain exposure with probable intercollicular boundary, absence of pineal representation, cerebellar region contacting with the lateral part of the caudal cerebral poles, high range of encephalization quotients, which are nearly below the known mammalian range. The significance of the caudal divergence of the hemispheres and the exposed midbrain is discussed. The morphology of the endocast and relative brain size of Therioherpeton cargnini are in general agreement with other features of the species that locates it as one of the more advanced cynodont toward mammalian patterns, and this may imply that the brain does not evolved more conservatively than other characters at the reptile-mammal transition.