206 



REPTILIA. 



Mosasaiiroids were first placed among the Lacertilians by 

 Professor Owen, and the view entertained by this distin- 

 guished comparative anatomist of their real affinities is now 

 generally accepted. Professor Cope, however, considers these 

 Eeptiles to form — under the name of Pythonomorpha — a 

 group allied to the Ojjhidia. 



The body in the Mosasauroids is greatly elongated, the 

 vertebrae being procoelous, and sometimes provided with a 

 zygosphene and zygantrum. The teeth (fig. 556) are long, 

 pyramidal, and slightly curved ; but they are anchylosed to 

 the jaw, and are not sunk into distinct sockets, as in the 

 living Crocodiles. The condition of the integument is un- 

 known in many forms ; but Marsh has recently shown that 



osseous dermal scutes are present 

 in some forms (e.g., Holcodiis, Lcio- 

 don, and Edestosaurus), and we may 

 reasonably infer the presence of a 

 similar armature in other members 

 of the group. It is not known, 

 however, how much of the surface 

 was thus protected, though it would 

 appear that the head was certainly 

 not defended by scutes. From the 

 shortness of the humerus, and the 

 indications that the vertebral column 

 was unusually flexible, and that the 

 tail was laterally compressed, it was 

 early conjectured that the Mosa- 

 sauroids were marine and aquatic 

 in their habits. This conjecture 

 has been raised to the rank of a 

 certainty by the discovery that the 

 fore and hind limbs of the Mosa- 

 sauroids were in the form of fin-like 

 paddles (fig. 557), like those of the 

 Ichthyosaur and Plesiosaur, but having the digits distinct. 

 There can therefore be no doubt that Ifosasattrus — like the 

 living Amhli/rhynchns — was aquatic in its habits, and fre- 

 quented the sea-shore, coming, in fact, only occasionally to the 



Fig. o67. — Right anterior paddle 

 of Lcstosavnis siimis, one-twelfth of 

 the natural size. (After Marsh.) 

 a, Scapiila ; 6, Coraeoid ; c, Hu- 

 merus ; d, Radius ; e. Ulna. 



