Ecomorphological diversity among Paleogene hyracoids (Mammalia): A new cursorial browser from the Fayum, Egypt

A new genus and species (Antilohyrax pectidens) of gazelle-sized hyracoid f rom the late Eocene, Jebel Qatrani Formation, Fayum Province, Egypt, exhibi ts dental, cranial and postcranial specializations unique among hyracoids. The lower incisors are broad, hyper-pectinate teeth similar to those of the extant dermopteran genus Cynocephalus. Upper incisors are apparently absen t, and the shape of the premaxilla suggests that the lower incisors occlude d against an upper fibrous pad, as in Cynocephalus and ruminants. The cheek teeth are dominated by sharp-edged, crescentic shearing blades, suggesting a folivorous diet. The articulation between the astragalus and navicular i s furrowed and condylar in shape, allowing notable midtarsal flexion and ex tension but limited lateral movement. The tibia and fibula are fused togeth er throughout most of their length. In size and proportions, limb elements resemble those of the extant springbok (Antidorcas marsupialis, Bovidae). F unctional inferences derived from these features suggest a cursorial browse r, a Paleogene analog to the bovids that do not appear in Africa until the Miocene. The new genus and species adds another adaptive dimension to what was already an extremely diverse record of Tertiary hyracoids, and further underscores that hyracoids were the dominant terrestrial ungulates of the A frican Paleogene.