page_title: Eremopezus
section_title: Feet
hierarchical_section_title: Eremopezus / Description / Feet
context_page_description: Eremopezus is a prehistoric bird genus, possibly a palaeognath. It is known only from the fossil remains of a single species, the huge and presumably flightless Eremopezus eocaenus. This was found in Upper Eocene Jebel Qatrani Formation deposits around the Qasr el Sagha escarpment, north of the Birket Qarun lake near Faiyum in Egypt. The rocks its fossils occur in were deposited in the Priabonian, with the oldest dating back to about 36 million years ago and the youngest not less than about 33 Ma.
  It is not precisely known from which strata the first few remains of this bird were collected. They were formerly considered of Early Oligocene age—some 33-30 Ma—but this is now assumed incorrect, as only the upper and not the entire Jebel Qatrani Formation is of Oligocene age. It is also possible that they are from the slightly older Qasr el Sagha Formation, but as both this and the Oligocene parts of the Jebel Qatrani Formation were laid down in an ecosystem markedly different from that of the Eocene Jebel Qatrani Formation, it is now assumed that all material of E. eocaenus is from the lowest rocks of the Jebel Qatrani Formation.
context_section_description: Its tibiotarsus length is not precisely known; if it had the proportions found in elephant birds and moa, it would have been 80–90 cm long. But there is no real reason to assume that Eremopezus, living in wetlands rich in predators, was similar to these bulky lumbering insular ratites. The tibiotarsus of DPC 20919 preserves most of the bone and is as long as the complete tarsometatarsus already (34 cm); an overall tibiotarsus length of c. 40–50 cm, as found in the small slow-moving elephant bird Mullerornis agilis and the nimble emu, is a reasonable estimate.
  The tarsometatarsus had a small hypotarsus with a single simple crest and devoid of foramina for tendons. The ankle joint consists of a sizable midward and an even larger outward groove. The conspicuous ridge on the backside of the tarsometatarsus is formed by the third toe's midfoot bones, which are set to the plantar side in respect to their neighbors, with which they are fused. This is particularly noticeable in the lower part of the bone, where a corresponding groove is present on the dorsal side. This smooths out proximad, with the proximal half of the bone—which is not known from an unflattened specimen to date—probably oval or triangular (with the point backwards) in cross section.
  As regards the length and stoutness of the lower leg and the foot, E. eocaenus would probably have been similar to a good-sized American rhea (Rhea americana) in measurements. Its toes, however, differed vastly in shape and posture from those of this ratite (and most other birds). Above the tibiotarsal trochleae of the African bird, the bone was considerably wider than the ankle, among ratites being matched by some moa and the dwarf cassowary (Casuarius bennetti). Thus, towards its toes the midfoot bone must have flared outwards, resulting in an overall wide-footed appearance. It is notable that while elephant birds have toes that are only a little more flaring than those of rheas, those of fast-running long-legged birds (ratites and others, like seriemas and some Charadriiformes) generally tend to bunch together in a narrower angle, with the most extreme situation found in the ostrich. This suggests that wherever Eremopezus did walk, it indeed walked or trotted and ran only in dire need—if it could run quickly at all, which is by no means certain.
  It is also notable that the attachment point of the tibiotarsal trochleae was flattened in Eremopezus, leaving little room for a bulky pad where the toes joined. In cursorial birds, this area is typically wide, to provide space for a large cushioning pad where the toes join, which improves balance during walking or running. The structure in E. eocaenus, by contrast, must have allowed a much better toe-flexing ability. The shallow grooves on the trochleae allowed for considerable sideways mobility of the toes; if the single phalanx bone known is assigned correctly to this species (it is the best match in size by far), it is very wide at the proximal end and tapers noticeably distad. The third (middle) toe was the most robust and largest. The inner toe was about as large as the outer one, and attached noticeably more proximal on the tibiotarsus. There is a single foramen on the dorsal side of the tarsometatarsus, with a plantar exit hole between the third and fourth metacarpal's distal ends (presumably for the outer toe's adductor tendon) and another (presumably for nerves and blood vessels) on the plantar surface of the tarsometatarsus. The outer sides of the outer trochleae have a hook at their backward end, which together with deep pits for ligaments nearby must have served to hold strong tendons. Its hallux was vestigial, as is typical for birds that move about on foot a lot; it even cannot be ruled out that the hallux was entirely missing (as in ratites).
caption: The dwarf cassowary (Casuarius bennetti) is one of the few ratites with toes as splayed  as (but still less mobile than) E. eocaenus
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