Running title: THE BRAIN ENDOCAST OF Riograndia riograndensis Academy Section: EARTH SCIENCES

Recently, the morphology and encephalization of the brain endocast of the Triassic non-mammaliaform probainognathian cynodont Riograndia guaibensis were studied. Here, we analyzed the brain endocast of an additional specimen of this species. The new endocast shows well-defi ned olfactory bulbs and a median sulcus dividing the hemispheres, traits that were not clearly observed in the fi rst studied specimen. Encephalization quotients were also calculated, revealing similar values to other nonmammaliaform cynodonts and lower than those of the fi rst analyzed specimen. The analyzed cranium is slightly larger than the fi rst studied one and may represent an advanced ontogenetic stage. Hence, these differences may be related to the intraspecifi c variation of this cynodont or alternatively, to the preservation of each specimen.