484 O. C. Marsh—On Dinosaurian Reptiles. 
AFFINITIES OF DINOSAURS. 
The extinct reptiles known as Dinosaurs were for a long 
time regarded as a peculiar order, having, indeed, certain rela- 
tions to Birds, but without being closely allied to any of the 
other groups of known Reptiles. J/egalosaurus and Jguano- 
don, the first Dinosaurian genera described, were justly con- 
sidered as representing two distinct families, one including the 
carnivores, and the other the herbivorous forms. 
With the discovery and investigation of Cetcosaurus 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 J/egalo- 
saurus, or I[guanodon, but constituted a well-marked group 
by themselves. It was this new order, the Sawropoda, as I 
have called them, that first showed definite characters allying 
them with other known groups of Reptiles. In 1878, I 
pointed out that the Sawropoda were the least specialized of 
the Dinosaurs, and I gave a list of characters in which they 
showed such an approach to the Mesozoic Crocodiles as to sug- 
gest a common ancestry at no very remote period.” 
FIGURE 1.—Restoration of A2étosaurus ferratus, Fraas; with dermal armor of 
the limbs removed. One-eighth natural size. 
Again in 1884, I called attention to the same point, and also to 
the relationship of Dinosaurs with the Aétosauria, as I had 
- named them, a group of small reptiles from the Triassic of Ger- 
many, showing strong affinities with Crocodilians.t A restora- 
tion of one of these small animals is shown in the diagram before 
you (figure 1). In the same communication I compared with 
Dinosaurs another allied group, the Hallopoda, which I had 
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 another diagram (figures 4-5), I 
have placed before you restorations of the fore and hind limbs 
of the type species (//allopus victor). 
* This Journal, vol. xvi, p. 412, November, 1878. 
+ Report British Association, Montreal Meeting, 1884, p. 765. 
