Article: Hindlimb of a giant terrestrial bird from the upper Eocene, Fayum, Egypt

Eremopezus eocaenus Andrews, 1904 is a giant groundbird from upper Eocene deposits of the Fayum, Egypt, which has hitherto been known from non-diagnostic fragmentary material. New fossils collected from quarry L-41 of the Jebel Qatrani Formation include two well-preserved distal tarsometatarsi and an associated whole tarsometatarsus and distal tibiotarsus that allow a more precise evaluation of the phylogenetic position and tarsal function of Eremopezus. Unlike most ratites, the distal tarsometatarsus has a patent distal foramen and a slight hallucal digit. The trochlea for digits II and IV are only slightly reduced in size, are splayed to the right, and the heads lack deep grooving. These features resemble the condition seen in BalaenicepsSagittarius, suggesting active use of the toes in grasping or manipulation, rather than the condition in graviports and cursors, which have reduced medial and lateral trochleae often with distinct grooving of the heads. The limb is relatively long and gracile, another difference from graviports. There is no compelling evidence to link Eremopezus to any known ratite lineage, to the Phorusrhacoidea, or to the extinct predatory birds of the Eocene (e.g. Diatryma, Gastornis). We suggest that Eremopezus represents an endemic African group that independently attained large size and flightlessness.