DINOSA URS. 



465 



series of forms, from those which walked about on all fours to those which stood 

 erect, an instance of evoluti(5n paralleled in Mammalia. 



The first representatives to receive treatment will be those which had the proximal 

 tarsal bones separate from each other and movably articulated to the terminal faces of 

 the tibia and fibula. JIadrosaurus had the teeth in several rows, and so juxtaposed as 

 to give a pavement-like appearance to the armature of the jaw. The members of this 

 genus were of gigantic size, being twenty-eight feet in length, the thigh-bone alone 

 having been forty inclies long, though the humerus was only about one half this length. 

 The animals wandered through the old American forests and used their small fore 

 limbs to grasp the branches of trees and direct them to the mouth. In water as weU 

 as on land they were active. 



Closely allied to the previous reptiles, though having the teeth in a single row, was 

 the Iguanodon of the European Jurassic, an animal presenting many points of structure 

 in common with the iguana of to-day. Especially iguana-like were the peculiar teeth. 

 Though in the several museums of 

 Europe there are many fossil rep- 

 resentatives of this genus, the skel- 

 eton of /. bernissartensis, lately 

 found in Belgium, and now in the 

 possession of the Brussels museum, 

 is by far the most perfect, there 

 being but a few fragments missing. 

 The animal walked on its hind 

 limbs, as do the birds, and left in 

 the Wealden strata its three-toed 

 tracks. The fore limbs, as will be 

 seen from the figure, were extreme- 

 ly short, and, besides being used 

 in gathering food, were probably 

 organs of defence, the thumb be- 

 ing covered with a strong, conical spine, which could have pierced through the 

 body-walls of any animal which might unwittingly lead an attack. When stand- 

 ing up, as it did while feeding, the Iguanodon had a stature of fourteen feet, though 

 when stretched out in the water, its broad tail acting as a propeller, it probably was 

 twenty-eight feet in length. Scelidosaurus differed from the Iguanodon in having 

 four digits on its hind feet, though its teeth were in a single row. Specimens are 

 very uncommon. 



In 1878 what was then the largest known land animal was described by Professor 

 Cope as the Camarasaurus supremiis, a reptile having the fore and hind limbs well 

 developed, the femur alone being six feet in height, and the animal having a total 

 length — including the strong and elongated tail — of about eighty feet. One of the 

 dorsal vertebrae measured over three feet in width, and equalled in size those of the 

 right whale. Such a huge reptile wandei-ed about on the shores, or in the shallow 

 water, where it could easily reach to the tops of the larger shrubs, or, by resting on its 

 haunches, it might browse on the tops of trees. It held its own, as a fossil, without a 

 rival, for only a short time, for soon, from the same deposit, the early cretaceous of 

 Dakota, appeared the bones of an allied animal, but differing in having the vertebral 

 centra strongly biconcave, or amphicoelous, a peculiarity which gave origin to the 

 VOL. III. — 30 



Fig. 268. — Iguanodon bernissartensis^ as restored by DoUo. 



