New Morphological Evidence for the Phylogeny of Artiodactyla, Cetacea, and Mesonychidae

Abstract
Parsimony-based analyses of a data set including 68 taxa coded for 186 morphological characters corroborate monophyly of Artiodactyla (even-toed ungulates), Suiformes (hippos, pigs, peccaries), Neoselenodontia (camels, deer, cows), and Acreodi (whales, dolphins, porpoises, mesonychids). Additional findings include a sister-group relationship between Cainotheriidae and Cameloidea (Camelidae + Oromerycidae), Elomeryx as the sister group to all other suiform artiodactyls, Protoceratidae as the basal branch of Neoselenodontia, and paraphyly of Mesonychidae. The molecule-based groups Whippomorpha (whales, dolphins, hippos), Cetruminantia (whales, deer, cows), and Artiofabula (whales, cows, pigs) are contradicted by these data and occur together in trees that are at least 25 steps longer than the most parsimonious ones. In terms of tree length, the molecule-based topology is contradicted by morphological data with and without extinct taxa, and unlike previous, morphology-based analyses, the exclusion of Cetacea from the clade of living artiodactyls is not dependent on the inclusion of extinct taxa. Artiodactyla is diagnosed in all most parsimonious trees by several characters, including a short mastoid process of the petrosal, absence of an alisphenoid canal, and presence of an entocingulum on P4. Some previously suggested artiodactyl synapomorphies, such as an enlarged facial exposure of the lacrimal and absence of contact between the frontal and alisphenoid, are shown to be synapomorphies of more exclusive clades within Artiodactyla.