Enigmatic new ungulates from the Early Middle Eocene of central Anatolia, Turkey

ABSTRACT

Four new ungulate species described here from the early middle Eocene Uzunçarsidere Formation, near Ankara, Turkey present a phylogenetic and biogeographic puzzle. The four species, known from jaws, teeth, and skull and postcranial fragments, share a suite of diagnostic dental features (selenolophodont molars, all lower molars lacking hypoconulids, premolars with metacones small or absent, and narrow, short premolar talonids) and are included in a single new genus, Hilalia. Hilalia saribeya, H. selanneae, H. sezerorum, and H. robusta are distinguished from each other by size and details of premolar morphology. Cladistic analysis indicates that although Hilalia shares a common ancestor with perissodactyls, hyracoids and some “condylarths” to the exclusion of artiodactyls, its position relative to those taxa is unresolved—the calcaneum lacks derived features of artiodactyl, perissodactyl or hyracoid calcanea, some features of Hilalia's molar morphology are convergent with features in some hyracoids, perissodactyls, and selenolophodont “condylarths”, and Hilalia has more primitive premolars than most members of those groups. The affinities of some other members of the Uzunçarsidere mammal fauna, including an embrithopod, marsupials, and a possible proboscidean, have suggested that central Anatolia may have served as a biogeographic crossroads for mammalian dispersal among Asia, Africa, and Europe during the early Paleogene. However, the absence of convincing links between Hilalia and any of the increasingly well-known Paleogene ungulates of Asia, Indo-Pakistan, and Africa, or those of Europe and North America suggests that our understanding of early Paleogene ungulate evolution and biogeography is far from complete.