A cladistic analysis among Trilophodont gomphotheres (Mammalia, Proboscidea) with special attention to the South American genera

Abstract

The trilophodont gomphothere group is a monophyletic group of genera separated from other proboscideans by one synapomorphy, the presence of trefoil-shaped wear patterns on the occlusal surfaces of their teeth. These wear patterns vary from being just a single trefoil, through double trefoils, to more complex combinations of trefoils. They are present in all of the genera studied here. Our cladistic analysis makes use of 12 genera as terminal taxa. It was performed using 43 cranial, dental and postcranial morphological characters. The polarity of characters was based on outgroup criteria using the genus Phiomia as the outgroup. All characters are considered to be unordered (34 are binary and nine are multistate). The present analysis leads us to reject the hypothesis that considered Rhynchotherium as a direct ancestor of South American gomphotheres and supports the hypothesis that Sinomastodon is the sister group of Cuvieronius and Stegomastodon. High congruence between the stratigraphical record and the phylogenetic hypothesis is observed.