Hypsodonty and body size in Typotheria-Hegetotheria notoungulates.

M. REGUERO Y A. CANDELA.

Puerto Madryn

Jornada; Reunión Anual de Comunicaciones Científicas y Simposio del 50º Aniversario de la Asociación Paleontológica Argentina; 2005

The Eocene/Oligocene array of Typotheria and Hegetotheria notoungulates in Patagonia is believed to represent independent radiations of endemic hypsodont clades presumably derived from different ancestry. Four families of these clades: Archaeohyracidae and Interatheriidae (protohypsodonts) and Hegetotheriidae and Mesotheriidae (euhypsodonts) were analyzed. The protohypsodonty in these groups first appear at 32.7 and 36.0 Ma in the Barrancan Age. Overall they exhibit a tendency to increase the crown height (hypsodonty) and the body size through their evolutionary history. The hypsodonty has been considered as an adaptation for grazing (abrasive diet). Body size has been identified as an important variable that characterizes differences between ungulate species with different dietary habits. In the case of these South American ungulates, the relation between both variables has not been studied taking into account the phylogenetic relationships between the species. In this contribution we test the existence of phylogenetic correlation in the hypsodonty and body size in these notoungulates and found that it is significant for both traits. We also explore the relationship between hypsodonty and body size removing the phylogenetic effect using the independent constrasts method. Preliminar results indicate that in South American ungulates the hypsodonty are not significantly associated with the body size after controlling for phylogeny. Among the ungulates examined the increasing of hypsodonty would not follow the gradually increasing of size. However, the correlated evolution of these variables is identified at less inclusive clades of Typotheria and Hegethoteria. Different hypsodonty-body size patterns found in these clades may be influenced by the different complexity of occlusal designs.