426 



THE GENERAL PRINCIPLES OF ZOOLOGY 



L% 



V- 



The Reptilia of the Mesozoic were for the most part very dif- 

 ferent from those living to-day, but some representatives of exist- 

 ing orders appeared then. The Chelonia and 

 Crocodilia date from the Triassic, the Lacertilia 

 from the Jurassic, and the Ophidia from the 

 Cretaceous ; but several orders arose and 

 became extinct in the Mesozoic era. The 

 Sauropterygia, to which we have already 

 referred as arising in the Permian, extended 

 through the Mesozoic. Some were relativelv 

 small, but others, like the Plesiosaurus ( Fig. 

 404), attained a length of twelve meters. 

 The bod\ r was lizard-like, with a small head, 

 long neck, two pairs of paddle-like appendages, 

 and a relatively short tail. Plesiosaurus was 

 marine, and lived probably in the shallower 

 waters near the shore. 



The Ichthyopterygia (Gr. t'x#w, fish, and 

 iTTepv^, fin) were reptiles which inhabited salt 

 water and in some cases attained a length of 

 from nine to twelve meters. The genus 

 Ichthyosaurus ( Fig. 405) is a typical represen- 

 tative. The head was large, and there was 

 no neck; there were two pairs of paddle-like 

 appendages and a long tail. From various 

 details of skeletal structure we know that 

 Ichthyosaurus went out for considerable dis- 

 tances in the open waters, but was able to 

 move about to some extent on the shore. It 

 was probably able to descend to considerable 

 depths and was a very carnivorous and vora- 

 cious animal, feeding on fish, especially ganoids, 

 which were abundant at that time. Remains 

 of the Ichthyopterygia have been found very 



He. 405. Ichlhyosau- j r j o 



ommunh. (After widely distributed geographically, in Europe, 



2SS n SSS3 Aflica " Asia< Australia > and North America, 

 in both Arctic and tropical regions, from the 



Triassic to the Cretaceous inclusive. 



A third group of Mesozoic reptiles, the Dinosauria (Gr. Setiw, 



£. 



