EVOLUTIONARY AFFINITIES OF THE ORDER PERISSODACTYLA AND THE PHYLOGENETIC STATUS OF THE SUPERORDINAL TAXA UNGULATA AND ALTUNGULATA

Contrary to morphological claims, molecular data indicate that the ord er Perissodactyla (e.g., horses, rhinoceroses, and tapirs) is neither part of the superordinal taxon Paenungulata (Sirenia, Proboscidea, and Hyracoidea) nor an immediate outgroup of the paenungulates. Rather, P erissodactyla is closer to Carnivora and Cetartiodactyla (Cetacea + Ar tiodactyla) than it is to the paenungulates. Therefore, two morphologi cally defined superordinal taxa, Altungulata (Proboscidea, Sirenia, Hy racoidea, and Perissodactyla) and Ungulata (Altungulata and Cetartioda ctyla), are invalidated. Perissodactyla, Carnivora, and Cetartiodactyl a are shown to constitute a rather tight trichotomy. However, a molecu lar analysis of 36 protein sequences with a total concatenated length of 7885 aligned amino acids indicates that Perissodactyla is closer to Cetartiodactyla than either taxa is to Carnivora. The relationships a mong Paenungulata, Primates, and the clade consisting of Perissodactyl a, Carnivora, and Cetartiodactylaa could not be resolved on the basis of the available data. (C) 1997 Academic Press.