The eutherian stapedial artery: character analysis and implications for superordinal relationships

Evidence from outgroups, ontogeny, neontology, and fossils is used to distinguish primitive and derived character states for the major components of the eutherian stapedial artery in 17 modern orders. Derived states support the following higher-level phylogenetic hypotheses: (1) Microchiroptera and Megachiroptera are monophyletic+ADs- and (2) within Ungulata, Tubulidentata is the outgroup to the remaining modern orders, followed in succession by Artiodactyla and then Cetacea. Three branches of the stapedial artery, the a. diploetica magna, ramus temporalis, and ramus posterior, all but neglected in previous syntheses, are shown to be primitive for Eutheria and Amniota.