Evolution of Gyrification in Carnivores

Abstract

The order Carnivora is a large and highly diverse mammalian group with a long and well-documented evolutionary history. Nevertheless, our knowledge on the degree of cortical folding (or degree of gyrification) is limited to just a few species. Here we investigate the degree of cortical folding in 64 contemporary and 37 fossil carnivore species. We do so by measuring the length of gyri impressions on endocranial casts. We use this approach because we have found that there is a very good correlation between the degree of cortical folding and the relative length of the gyri that are exposed on the outer surface of the hemispheres. Our results indicate that aquatic and semiaquatic carnivores have higher degrees of cortical folding than terrestrial carnivores. The degree of cortical folding varies among modern families, with viverrids having the lowest values. Furthermore, the scaling of cortical folding with brain size follows different patterns across specific carnivore families. Forty million years ago, the first carnivores had a relatively small cortex and limited cortical folding. Both the size of the cortex and the degree of cortical folding increased independently in each family during evolution.

Brain of the African wild dog. I. Anatomy, architecture, and volumetrics

“…To date few descriptions of the anatomy of the brains of wild canids are available (limited to endocast morphology, e.g., Radinsky, 1969Radinsky, , 1973Lyras & Van der Geer, 2003;Lyras, Giannakopoulou, Kouvari, & Papadopoulos, 2016), which is in direct contrast to many comprehensive studies of the brain of the domestic dog (e.g., Beitz & Fletcher, 1993;Fox, 1971;Palazzi, 2011;Singer, 1962). Here we have provided a comprehensive description of the brain of the African wild dog, which, due to its specialized social behavioral repertoire (Creel & Creel, 1995;Gusset et al, 2006;Robbins & McCreery, 2000;Skinner & Chimimba, 2005;Thomas et al, 2006;van den Berghe et al, 2012;Walker et al, 2017) and phylogenetic position within the canids (Bardeleben et al, 2005;Lindblad-Toh et al, 2005), is of interest in understanding the derived and shared neural features of the various members of the canid lineage, including the domestic dog.…”

The Brain Anatomy of the Brown Bear (Carnivora, Ursus arctos L., 1758) Compared to That of Other Carnivorans: A Cross-Sectional Study Using MRI

“…However, it is less convoluted than in Pinnipedia: Zalophus californianus (Montie et al, 2009), northern fur seal ( Callorhinus ursinus ) and Steller sea lion ( Eumetopias jubatus ) (based on specimens available in CMBC). Gyrification studies showed the polar bear ( Ursus maritimus ) having a considerably more convoluted brain surface than other sampled Carnivora species, surpassed only by two Pinnipedia species (Lyras et al, 2016).…”

The neurocranium of Ekweeconfractus amorui gen. et sp. nov. (Hyaenodonta, Mammalia) and the evolution of the brain in some hyaenodontan carnivores

“…(Frey et al, 2011;Grohé et al, 2012;Mahboubi et al, 2014). A study by Lyras et al (2016) suggested that aquatic and semi-aquatic carnivorans as a rule have more gyrencephalic brains than terrestrial ones, but this is not the case with A. macrognathus. The homology between the functional regions of the cortex in hyaenodonts and carnivorans is currently not sufficiently established to speculate about more specific sensory adaptations such as those seen in the otter (Radinsky, 1968).…”