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PALAEONTOLOGY, VOLUME 44
TABLE 1. Tarsometatarsal dimensions (mm) of Eremopezus and a selection of other birdsa. Species
Length
Eremopezus eocaenus DPC 20191 340 DPC 5555 ± Rea americana ÐÐ 335 ÐÐ 347 ÐÐ 319 Struthio camelus ÐÐ 439 ÐÐ 448 ÐÐ 441 Casuarius bennetti ÐÐ 259 ÐÐ 239 Casuarius sp. ÐÐ 256 Dinornis sp. ÐÐ 210 Sagittarius serpentarius ÐÐ 287 a
Proximal Width
Distal Width
Proximal Width/ Distal Width
56 ±
62 64
0´16 ±
43 45 40
39 39 41
0´13 0´13 0´13
71 70 71
59 54 56
0´16 0´16 0´16
38 37
45 44
0´15 0´15
41
41
0´16
92
118
0´44
24
21
0´08
Specimens housed in the University of California at Los Angeles (UCLA), Department of Biology.
Comparisons with extant neognathous birds. Eremopezus is not particulary close in morphology to any extant bird. Interesting comparisons can be made to the largest extant waterbirds and to large, terrestrial predators, even though these are still considerably smaller than Eremopezus and differ from it in many details. The shape of the distal tarsometatarsus is most closely approximated in the shoebilled stork (Balaeniceps rex, Balaenicipitidae) and in the secretarybird (Sagittarius serpentarius, Sagittariidae). Like Eremopezus, the shoebill has a markedly compressed distal end of the tarsometatarsal shaft, with splayed trochleae of about equal size and without much posterior de¯ection. The secretarybird also has notable splay, and is similar to Eremopezus in the shape and proportions of the trochleae. Both the secretarybird and the shoebill use their feet for active manipulation; the secretarybird captures snakes and other prey with its toes, while the shoebill grasps its way along tangled mats of ¯oating vegetation. Comparison with giant ground predators. The foot of the large North American genus, Diatryma, is very robustly built (Shufeldt 1915; Sinclair 1928). The shaft is relatively short and thick, and the central trochlea is relatively massive. The trochleae are splayed, but the medial and lateral ones are more reduced in size than those of Eremopezus, especially the medial one. The heads of the medial and lateral trochleae are nearly ¯at in Diatryma, rather than grooved, probably re¯ecting pro®cient rotation, abduction and adduction of the toes that originate on them. Both Diatryma and Gastornis have patent supratendinal bridges of the tibiotarsus. The tarsometatarsus of Gastornis is similar to that of Diatryma but the central trochlea is less enlarged; the medial and lateral trochleae are somewhat splayed and their heads are notably grooved (Martin 1992). In phorusrhacids the medial and lateral trochlea are reduced more than in the Fayum fossil (Matthew and Granger 1917). The tarsometatarsus of Eremopezus is not specialized for cursoriality to the extent seen in phorusrhacids. Comparison with ratites. Eremopezus is notable for the presence of a distal foramen and a possible scar for the hallux. Both of these features are unusual among extant ratites, but moas of the family Anomalopterygidae