

0. C. Marsh — Footprints of Jurassic Dinosaurs. 231 



The interpretation of the various footprints here shown is 

 fortunately a much less difficult matter than that of the huge 

 tridactyle tracks from the Triassic, as in the latter case there 

 was little except conjecture to assist in the investigation. In 

 the present instance, however, it is known that abundant osse- 

 ous remains of large Dinosaurs are imbedded in deposits of 

 the same age, and in the same general vicinity. Some of 

 these reptiles are known to have been bipedal, and quite large 

 enough to make the footprints now discovered. Moreover, 

 the structure of the feet of some of these animals is sufficiently 

 well known to demonstrate clearly that in walking they must 

 have made footsteps similar to, if not identical with, the fossil 

 specimens here recorded. 



l. 



Figure 1. — Outlines of Jurassic footprints found with those shown on Plate V- 

 a, footprint of large herbivorous reptile ; 5, footprint of large carnivorous 

 reptile ; c, footprint of smaller carnivorous reptile. 



All the figures are one-tenth natural size. 



As to the particular reptiles that made the present foot- 

 prints, we have a hint in the impressions themselves. Some 

 of these show marks of short and wide toes, suggesting that 

 they were made by the robust feet of herbivorous Dinosaurs. 

 The other footprints show impressions of longer and more 

 slender toes, such as are known in the carnivorous Dinosaurs, 

 which lived at the same time and in the same region as the 

 herbivorous forms, and, indeed, preyed upon them. In Plate V, 

 the large figure on the left evidently represents the foot- 

 print of a herbivorous Dinosaur, while the small one on the 

 right, with slender toes, was probably made by a carnivorous 

 form. Of the outline figures above, the one with the thick 

 digital imprints (a) was doubtless made by a herbivorous rep- 

 tile, while the other two (b and c) appear carnivorous in type. 



In selecting from this horizon the known. Dinosaurs that 

 might have made the present footprints, it would be safe to 

 say that the genus Camptosaurus, especially some of its larger 

 species, may be held responsible for the herbivorous footsteps, 

 while its carnivorous enemy, Allosaurus, had representatives 

 to which the more slender impressions may naturally be due. 



