454 MESOZOIC ERA— AGE OF REPTILES. 



a, b, c. There has been found, also, the whole form of one insect appar- 

 ently the larva of an Ephemera (Fig. 716). It is quite probable that 

 many of the tracks were formed by similar larves inhabiting the water. 



Reptilian Tracks. — By far the larger number of tracks are those of 

 Reptiles. More than fifty species have been described by Hitchcock.* 

 These vary extremely, both in size and in character. In size, they vary 

 from the track of a living Triton, a half-inch long, to that of the Oto- 

 zoum (Fig. 717), twenty inches long, and with a stride of three feet. 

 Some had five toes, some four, and some only three functional toes on 

 the hind-feet. Again, some had hind and fore feet of nearly equal size, 

 and evidently walked or crawled in true quadrupedal style. Others had 

 hind-feet much larger than fore-feet, and were essentially bipedal in 

 locomotion, only putting down their small fore-feet occasionally ; but 

 walking bird-like, not hopping kangaroo-like, on their hind-legs. In 

 connection with the bipedal tracks there have been found what seemed 

 to be the impression of a dragging tail (Fig. 718) ; but these are so 

 rare and doubtful that it is generally believed the animals were mostly 

 long-legged and short-tailed. 



The general conclusion from an attentive study of these tracks, in 

 connection with the findings elsewhere of bones and teeth, is that they 

 are the tracks partly of Amphibians of the order of Labyrintliodonts, 

 but mostly of Dinosaurs. The hugest among them, the Otozoum Moodii 

 (Fig. 717), was probably a long-legged biped amphibian, which stood 

 twelve feet high. The Anom^ms (Fig. 719), a common form, was 

 probably a Dinosaur, which walked often on two legs only, and in so 

 doing brought the whole tarsus and heel on the ground, in the manner 

 of a kangaroo when resting. 



Supposed Bird-Tracks.— Those which have been referred to birds 

 are : 1. Wholly bipedal, i. e., there is no evidence of fore-feet at all. 2. 

 They are tridactyl. 3. They have a regular progression in the number 

 of joints in the tracks, the inner toe having two, the middle toe three, 

 and the outer toe four joints. Now, in birds, the inner toe has three, 

 the middle toe four, and the outer toe five joints, but the last two joints 

 in each case make but one division of the track, so that the track is ex- 

 actly what is given above. The discovery, however, that Dinosaurs 

 have but three functional toes on the hind-foot, and that they also have 

 the same number of joints as birds, has greatly shaken confidence in the 

 ornithic character of these tracks. Only the absence of fore-feet tracks, 

 therefore, remains. But as many of these early reptiles walked occa- 

 sionally on two legs, it is not impossible that some of them always 

 walked thus. It is quite possible or even probable, therefore, that all 

 these tracks are those of Reptiles. Assuming them to be those of 



* About seventy species are now known (E. H. Hitchcock). 



