Paleoneurology in Proterotheriidae Litopterns: a Case of Neuromorphological Convergence between Extinct South American and North American Ungulates

DOZO, MARÍA TERESA

Jena

Congreso; 6th International Congress of Vertebrate Morphology; 2001

Institute of Systematic Zoology and Evolutionary Biology. Friedrich-Schiller-Universitat

Paleoneurology of mammals can supply novel information on particular evolutionary processes such the cases of homoplasy. The Proterotheriidae, characteristic of the South American Tertiary, have been considered convergent with the Equiidae, for the reduction of the fingers but in dental and tarsal traits, they look like Cervidae and Camelidae. The objectives of this study are to infer the brain of these litopterns and to compare them with the brains of Perissodactyla and Artiodactyla of the Northern Hemisphere that may correspond to their ecological equivalent. The endocasts of Proterotheriidae show good representation of the telencephalic hemispheres, of rectangular contour with a well developed isocortex and a complex sulcal pattern. The longitudinal neocortical sulci are homologated to the ectosylvian, suprasylvian, ectolateral, lateral and entolateral sulci. The analysis of endocasts of extinct ungulates of the Northern Hemisphere, suggests that, during the Oligocene and Miocene, perissodactyls Equiidae and Hyracodontidae and artiodactyls Oreodontidae, Camelidae, Boviidae, Suidae and Palaeomerycidae developed  brains with similar external morphologies to those of the Proterotheriidae. It stands out the presence of several longitudinal neocortical sulci and the expanded front region, without development of the Sylvian region. Given that these similarities are observed among divergent groups, they are interpreted as adaptive responses to similar selective pressures. Thus, it may be expected that similar adaptive types develop brains with similar morphological patterns.