jiaksh.] AFFINITIES OF DINOSAURS. 'J 31 



the accompanying plate, based mainly upon a study of the original 

 specimens. 



Besides the four genera here represented, no other European dinosaurs 

 at present known are sufficiently well preserved to admit of accurate 

 restorations of the skeleton. This is true, moreover, of the dinosaurian 

 remains from other parts of the world outside of Xorth America. 



AFFINITIES OF DINOSAURS. 



The extinct reptiles known as dinosaurs were for a long time 

 regarded as a peculiar order, having, indeed, certain relations to 

 birds, but without being closely allied to any of the groups of known 

 reptiles. Megalosaurus and Iguauodon, the first dinosaurian genera 

 described, were justly considered as representing two distinct families, 

 one including the carnivores, and the other the herbivorous forms. 



With the discovery and investigation of Cardiodon (Cetiosaurus) and 

 its allies in Europe, and especially of the gigantic forms with similar 

 characters in America, it became evident that these reptiles could not 

 be placed in the same families with Megalosaurus or Iguanodon, but 

 constituted a well-marked group by themselves. It was this new order, 

 the Sauropoda, as the writer has named them, that first showed definite 



Fig. 06. — Restoration of Aetosaurus ferralus Fraas ; with dermal armor of the limbs removed. One- 

 eighth natural size. 



characters allying them with other known groups of reptiles. In 1878 

 he pointed out that the Sauropoda were the least specialized of the 

 dinosaurs, and gave a list of characters m which they showed such an 

 approach to the Mesozoic crocodiles as to suggest a common ancestry 

 at no very remote period. 1 



AFFINITIES WITH AETOSAURIA. 



Again, in 1884, the writer called attention to the same point, and 

 also to the relationship of dinosaurs with the Aetosauria, as he has 

 named them, a group of small reptiles from the Triassic of Germany 

 showing strong affinities with crocodilians. 2 A restoration of one of 

 these small animals is shown in fig. 56. In the same communication 

 he compared with dinosaurs another allied group, the Hallopoda, which 

 he described from the lower Jurassic of America, but had not then fully 

 investigated. Subsequent researches proved the latter group to be of 

 the first importance in estimating the affinities of dinosaurs, and in 

 figs. 59 and 60 are restorations of the fore and hind limbs of the type 

 species (Hallopus victor). 



1 American Journal of Science. Vol. XVI, p. 412, November, 1878. 



2 Report .British Association, Montreal Meeting, 1884, p. 765. 



