2394 CROCODILES, DINOSAURS, AND FLYING DRAGONS 



OUTER AND LATERAL VIEWS OF A TOOTH 

 OF THE IGUANODON. 



characterized by the presence .of a separate chin bone (pd in the figure on p. 2359) 

 at the extremity of the lower jaw; by the absence of teeth from the front of both 

 jaws; by the teeth themselves approximating more or less closely to the type of the 



one here represented, and by being fre- 

 quently not implanted in distinct sockets; 

 and likewise by the vertebrae being com- 

 pletely solid throughout. The typical rep- 

 resentatives of this group are the well- 

 known iguanodons, originally described on 

 the evidence of teeth, from the Wealden 

 rocks of England, but now known by entire 

 skeletons from the corresponding deposits 

 of Belgium, which are exhibited in the 

 museum at Brussels. These reptiles, 

 which were represented by allied forms in 

 the United States, habitually walked on 

 their three-toed hind-limbs, the largest in- 

 dividuals attaining a length of some thirty- 

 three feet. They are characterized by the limb bones being hollow, by the length 

 of the metatarsal bones of the foot, by the first digit of the five-toed fore-limb 

 being converted into a large conical spine, and also by the teeth being of the type 

 of the one shown in the accompanying figure. Needless to say, animals with 

 such teeth must have been purely vegetable 

 feeders, as indeed were all the other members 

 of this group. The hind-feet terminated in 

 rather sharp claws, and there was no bony 

 armor on the body. The iguanodons probably 

 stalked about among the palm forests of the 

 Wealden period, on the leaves and fruit of 

 which they may be presumed to have in great 

 part subsisted. In these reptiles the large, 



flattened, and serrated teeth were arranged in each jaw in a single row, but in cer- 

 tain smaller forms known as trachodons which occur in the higher Cretaceous 

 rocks of both Europe and North America, there were several rows of teeth in 



use at the same time, the edges of these 

 teeth being so flattened and fitted to- 

 gether that a pavement-like structure 

 resulted. These trachodons were all 

 much inferior in size to the gigantic igu- 

 anodons. The American claosaur ( Clao- 

 saurus] , of which the skeleton is figured 

 on p. 2393, differs from the iguanodons 

 in having the fore-paw of normal structure. Nearly-allied to the iguanodons are 

 the remarkable armored and horned dinosaurs, which constitute a subgroup char- 

 acterized by their solid limb bones, the presence of some kind of bony armor, the 



PAVEMENT-LIKE TEETH OF THE 

 TRACHODON. After Marsh. 



TERMINAL TOE BONE OF AN ARMORED 

 DINOSAUR. After Marsh. 



