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292. Smaller and more slender theropods. Vertebrae amphicoelous. Teeth compressed, more or less recurved. Astragalus without ascending process.

Upper Triassic. Anchisaurus Marsh, Megadactylus Hitchcock, Ammosaurus Marsh, Connecticut Valley. Thecodontosaurus Riley and Stutchbury, England, Africa, Australia. Massospondylus Owen, South Africa. Zanclodon Plieninger, Sellosaurus Huene, Europe.



[No MS. was found for (1) the Coelurosauria, containing several families and numerous genera of light-limbed saurischian dinosaurs, including the Ornithomimidae, (2) the Megalosauria group of the Jurassic, and (3) the Deinodont group of the Cretaceous. For group 1 see papers by Osborn 1917 (Bulletin, Amer. Mus. Nat. Hist., vol. XLIII), von Huene 1921 (Acta Zoölogica, Bd. II); for groups 2 and 3 see Matthew and Brown, 1922 (Bulletin, Amer. Mus. Nat. Hist., vol. XLVI).—.]

Quadrupedal, semiplantigrade, herbivorous dinosaurs, with long neck and tail and small skull. Postfrontal sometimes present. Teeth subcylindrical, with a thickened, spoon-shaped crown, in a single row, and more or less restricted to anterior part of jaws, the premaxillae with teeth; no predentary. No coronoid process to mandible. The anterior, sometimes all, presacral vertebrae opisthocoelous, with a more or less developed hyposphene-hypantrum articulation, and with hollow, lateral cavities in centra. Four or five sacrals, twenty-six or