Abstract

Cambaytheres (Cambaytherium, Nakusia, and Kalitherium) are recently discovered early Eocene placental mammals from the Indo-Pakistan region. They have been assigned to Perissodactyla (the clade including horses, tapirs, and rhinos, a member of superorder Laurasiatheria) or Anthracobunidae, an obscure family that has been variously considered artiodactyls or perissodactyls, but most recently placed at the base of the Proboscidea or of Tethytheria (Proboscidea + Sirenia, superorder Afrotheria). Based on new dentitions, skulls, and postcranial elements, we demonstrate that cambaytheres occupy a pivotal position as the sister taxon of Perissodactyla, thereby providing insight on the phylogenetic and biogeographic origin of Perissodactyla. The presence of the sister group of perissodactyls in western India near or prior to the time of collision suggests that Perissodactyla may have originated on the Indian Plate during its final drift toward Asia.