MESOZOIC ERA: THE AGE OE REPTILES 



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able that some of the land reptiles should have changed their habits, 

 when it is remembered that in the shallow waters bordering the land 

 there was an abundant supply of fish for food, and also that there was 

 probably some overcrowding on the land which would force the 

 weaker species to take the food that was not to the liking of their 

 stronger neighbors. 



Ichthyosaurus (Greek, ichthus, fish, and saurus, reptile). — The 

 most conspicuous features of reptiles of this order (Fig. 514) are the 



Fig. 514. — Ichthyosaurus, showing both the skeleton and the "shadow" made 

 by the carbon of the fleshy parts of the body. (Courtesy, American Museum of 

 Natural History.) 



heavy body, with its pointed head and numerous teeth, and the 

 powerful tail, with its vertical fin, adapted for rapid propulsion. 

 Some individuals grew to be 40 feet long, although the usual size 

 was very much less. The jaws of some individuals were five feet 

 long and were furnished with 200 conical teeth. The eyes were 

 large, not only in proportion to the size of the skull, but in the 

 largest species actually attained in some perhaps the size of the 

 human skull, and were provided with a ring of radiating, bony 

 plates (sclerotic plates), like those of the early amphibians, which 

 were apparently for the purpose of focusing the eye, as well as for 

 protection. 



The limbs consisted of paddles, made up of three or more rows of 

 polygonal bones, the whole being covered with a leathery membrane. 

 The skin was smooth and without scales. The vertebrae were bicon- 

 cave, as in fishes. That Ichthyosaurus was carnivorous is shown by 



