472 RICPIARD SWANN LULL ON 



The fifth stage is that of Ornithomimus, a Cretaceous carnivorous dinosaur, in which 

 both lateral digits are obsolete, and with the loss of metatarsal I, metatarsal IV becomes 

 the widest at the proximal end. Ornithomimus seems to be an aberrant form and 

 strongly suggests the footprint genus Grallator. Most Cretaceous dinosaurs have reached 

 this stage of absolute structural tridactylism. 



Digit V is thus the first to suffer reduction being functional in no known dinosaur. 

 Digit I follows, but more slowly, especially in the carnivorous Theropoda where its use as 

 a prehensile claw caused it to be retained longer than in the herbivorous Orthopoda. An 

 interesting compensation is also shown between the widening of the proximal end of 

 metatarsal 11 as metatarsal V is reduced and in the same manner the widenino- of meta- 

 tarsal IV follows the loss of that of the hallux, thus maintaining the width of the ankle 

 joint. Otozoum represents a pro-Anchisaurus stage in its plantigrade foot and well 

 developed, non-rotated hallux. It is more generahzed than the foot of any known 

 dinosaur. 



Evidences as to gait, speed, and habits. — {a) Non-saltatorial. The gait of the vari- 

 ous creatures which left their impressions on the sandstone is in most instances a true 

 walk or run, generally bipedal, sometimes quadrupedal, and but rarely does one find 

 evidence of a sprawling crawl, such as most modern reptiles exhibit. There is no evi- 

 dence whatever among the footprints of a leaping dinosaur, that is, one in which both feet 

 leave the ground at the same moment. Fidicopus lyelJianus, in a fine specimen, no. ^ 

 of the Hitchcock ichnological museum, at Amherst (E. Hitchcock, '65, pi. 19), seems to 

 have tried to stop so suddenly as to slide for a considerable distance before overcoming its 

 momentum and this is the nearest approach to evidence in favor of a saltatorial form. 



The Anomoepodoid foi-ms, which include Fulicopus with their elongated metatarsi, 

 have a limb whose structure approaches a saltatorial type as much as that of any other 

 dinosaur, with the possible exception of Hallopus a lower Jurassic form, (Marsh, '96, p. 

 153), and the evidence leads one to doubt whether any dinosaurs were truly leapino- in 

 gait. Hitchcock ('58, p. 57) in speaking of Fidicopus lyeUlanus {Anomoepus major) 

 says : " On one specimen in the cabinet we find the impression [of the ischial callosity, 

 vide infral repeated at the distance of ten inches, as if the animal moved by leaps." 

 This serial repetition of the impression may have been made hy the animal resting at 

 each step while feeding as the footprints give no evidence of jumping nor is it hkely that 

 an animal would take successive leaps of ten inches whe)i its normal stride was two and 

 a half feet ! 



(6) Semiaquatic habits. The existence of semiaquatic forms seems to be proven by 

 the presence of a web to the foot in several instances, the most notable being Otozoum 

 moodii in which the membrane, if such it were, extended for some distance beyond the 



