The evolution of the brain in Canidae (Mammalia: Carnivora)

Canid brain evolution followed three independent, yet convergent paths. Each of the three canid subfamilies (Hesperocyoninae, Borophaginae and Caninae) started with a simple brain, which gradually became more complicated as the cerebral cortex became larger and more fissured, the cerebellar hemispheres became larger and the vermis more twisted. The extent to which these evolutionary changes took place differs between the three canid subfamilies. Caninae, the living group, has the most advanced external brain anatomy. This is related to the general tendency of the carnivore brain to become more convoluted through geological time. A parallel development of similar sulcal patt erns took place in independent lineages within the Canidae. As a result, some sulci appeared independently several times during canid evolution. The cruciate sulcus appeared four times; the Sylvian, endolateral, ectolateral and ectosylvian sulci appeared three times. The skulls of species with short rostra have a more posteriorly placed posterior border of the palate than those of their close relatives with long rostra. This arrangement affects the position of the cribriform plate (posterior to which the olfactory bulbs are housed), which is also moved backwards and, as a result, the frontal lobes appear more massive. Some canid lineages evolved large size and certain craniodental characters (e.g., deep jaws and large canines), which allowed them to prey on large-bodied animals. In these cases a stasis is noted in brain evolution. This phenomenon might be related to energetic constraints.