2r(i A\NALS NEW YORK ACADEMY OF SCIENCES 



I take to be an indication that their quadrupedal gait is partly secondary 

 and that they are derivable from long-limbed, partly bipedal ancestry. 

 The shortening of the feet and pillar-like construction of the limbs is an 

 obvious parallelism with the specialization of these parts seen in all large 

 hind juamraals and is an adaptation to their great size. No near parallel 

 can he round to this group among living animals; the hippopotamus 

 affords some suggestions, but diverges widely in many respects.^^ 



I have already referred to the primary adaptation of ilic dinosaurs 

 as a dry-land adaptation of the Reptilia. To a limited extent, the mod- 

 ern lizards represent a corresponding adaptation but not carried so far 

 or occupying so important a place in the fauna. The lizards have to 

 compete with the large and varied dry-land fauna of mammals, and rela- 

 tively to these, they occupy but an unimportant niche in the terrestrial 

 life. They suggest, however, the sort of animal which in tlie absence 

 of a higher competing type evolved into the dinosaurs, and their more 

 specialized types (e. g., Chlainydosaurus) mimic them in proportions in 

 a most instructive manner. 



Dinosaurs are first recorded from the Triassic; those which we actually 

 know^® are of moderate to large size, slender and long limbed as com- 

 pared with other reptiles, not highly specialized in dentition, unarmored 

 and some but not all bipedal in gait. Indirect evidence in the multitudes 



»^ See W. D. Matthew : "The Pose of the Saiu-opodous Dinosaurs," Amer. Nat, vol. 



xliv, pp. 547-.'ifj0. 1010. 



88 The principal references on Triassic dinosaurs are the following: 



R. Broom : "On the South .\frican Dinosaur liortalotarsus," Trans. S. Afr. Phil. Soc, 



vol. xvi, pp. 201-204. 1006. 



E. FuAAs : "Die neuesten Dinosaurlerfunde in der schwabischen Trias," Die Natur- 

 wlssenschaften, Bd. I, Heft 4.5, pp. 1097-1100. 1913. 



F. VON HuEXE : "Die Dlnosaurier der europiiischen Triasformation." Geol. u. Pal. 

 Abh., Supplem. Bd. I. 1908. 



: "Kin prlmitiver Dinosaurier aus Elgin," Geol. u. Pal. Abh., Bd. xiv (N. S., 



Bd. X) Heft. I. 1910. 



■: "Beitriige zur Geschichte der .\rchosaurier," ibid., Bd. svii (N. S., Bd. xlll) 



Heft. I. 1014. 



: "Ueber die Zweistiimmigkcit der Dinosaurier," Neues Jahrb. Bell., Bd. xxxvll, 



s. 577-589. 1914. 



F. VON HuENE und R. S. Lull: "Neubeschreibung des Originals von XaiKisuiinis agilis 

 Marsh," Neues Jahrb., Bd. I, s. 134-144. 1908. 



-: "On the Triassic Reptile Hallopus victor Marsh," Amer. Jour. Scl., 



vol. XXV, pp. 113-118. 1908. 



O. Jaekel : "Ueber die Wirbethierfunde in der Oberen Trias von Halberstadt," Palse- 

 ont. Zeitsch., Bd. I, s. 155. 1913. 



R. S. Lni.L : "Fossil Footprints of the .Tura-Trlas of North America," Mem.. Boston 

 Soc. Nat. Hist, vol. v, pp. 461-557. 1904. 



— : "Dinosaurian Distribution," Am. .Tour. Scl., vol. xxix, pp. 1-39. 1910. 



: "The Life of the Connecticut Trias," ibid., vol. xxxlil, pp. 397-422. 1912. 



O. C. Marsh : "Notes on Triassic Dinosauria," ibid., vol. xllii, pp. 543-546. 1892. 



: "Restoration of Anchisaurus," ibid., vol. xlv, pp. 169-170. 1893. 



: "Dinosaurs of North America," U. S. Geol. Sur., 16th Annual Report pp. 143- 



244, pll. 1896. 



