The phylogeny of the order Carnivora based on cerebral structure

Abstract

The cerebral structure of thirty-nine species of the order Carnivora is examined on a comparative basis. Descriptions and illustrations of four basic views (lateral, dorsal, medial, ventral) of each species are provided. It is proposed that the cerebrum of the family Canidae represents the ancestral form. From that point, the phylogenetic development of each major cerebral trait is traced individually. Among the most important sequences of changes is that shown by the Sylvian gyrus. This becomes infolded into the Sylvian cleft and successively reduced until lost at several levels along one branch, whereas along another it becomes strongly reduced while remaining superficial. Changes in the ectosylvian gyrus accompanying those of the Sylvian include its becoming infolded and reduced on the first line mentioned above. Other cerebral traits that were of outstanding value are the cruciate sulcus, ursine lozenge, pyriform lobe, and ectolateral and lingual gyri. Among the conclusions reached is one concerning the Pinnipedia. Because of the close similarity of the cerebrum to that of the bears, it appears unjustified to accord it ordinal or even subordinal rank. Nor does the two superfamilies currently recognized receive support. It is further concluded that the Viverridae lacks homogeneity and that the Lutrinae deserve consideration as a separate family.