n. plOrnithoscelida(Zoöl) A group of extinct Reptilia, intermediate in structure (especially with regard to the pelvis) between reptiles and birds.
Century Dictionary and Cyclopedia
ornithoscelidaA remarkable order of extinct reptiles presenting many characters intermediate between those of Reptilia and Aves, the ornithic modification being especially well marked in the pelvic arch and limb, whence the name. The ilium extends far in advance of the acetabulum, and is expansive, widely arching over the pelvic cavity, as in birds. The slender prolonged ischia, in some genera, are ornithic in character, and, in Hypsilophodon at least, unite in a median ventral symphysis. The pubes in some genera are as slender and elongated as in a typical bird. The tibia has a great cnemial crest and a ridge for the fibula, and its distal end is as in a bird, with a fossa to receive the ascending process of the astragalus. The distal end of the fibula is smaller than the proximal, though not so much reduced as in birds. The astragalus, similar to that of a bird, remained distinct in many genera; bnt in some, as Compsognathus, Ornithotarsus, and Euskelosaurus, it seems to have ankylosed with the tibia. The genera of Ornithoscelida are numerous, ranging throughout the Mesozoic period; the animals are mostly of large size, some of them, as the ignanodon, being among the largest terrestrial animals known. The order is divisible into two suborders, Dinosauria and Compsognatha.