2o6 WATER REPTILES OF THE PAST AND PRESENT 



smaller than those of the gavials even. The resemblance of the 

 living teleosaurs to the modem gavials must have been very 

 great, although the heavier bony armor indicates a less exclusively 

 aquatic life. They probably Hved more in the shallow waters of 

 the seas near the shores. 



Near the close of the Jurassic appeared for the first time, so 

 far as we now know, broad-headed mesosuchian crocodiles, forms 

 having less numerous and stronger teeth, and resembling closely 

 modern alligators. It has been believed that these broad-headed 

 kinds were of later origin than the more slender-nosed teleosaurs, 

 but a moment's consideration will make it evident how improbable 

 such an evolution must be. The crocodiles must have descended 

 from strictly terrestrial reptiles, and no terrestrial reptiles have 

 a slender nose. That they should have acquired a slender face in 

 adaptation to water habits and then returned to the more primitive 

 land type with a broad face and less strictly aquatic habits is con- 

 trary to all our experience in paleontology. From this it is alto- 

 gether probable that broad-faced crocodiles of later times must 

 have been the descendants of broad-faced kinds that were in exist- 

 ence during all the Jurassic times, but of which we as yet have no 

 knowledge. These broad-faced Jurassic crocodiles were, for the 

 most part, small creatures, much smaller than the teleosaurs even, 

 and smaller than any species of crocodiles now living. Their 

 remains are known only from fresh-water or shore deposits, and are, 

 for the most part, associated with those of land and fresh-water 

 animals. About the time of their first known appearance in geo- 

 logical history, the small mammals and birds had also become more 

 or less abundant, and it was suggested by Owen that these land 

 animals had sometjiing to do with the development of the ancient 

 amphibious crocodiles. Perhaps this was the case with respect to 

 their greater abundance and development, and with certain pecu- 

 liarities of their structure, but that the gavial-like teleosaurs should 

 have come back to the land and reverted to a more primitive form 

 seems quite improbable. 



During Cretaceous times, especially in America, numerous forms 

 of these old mesosuchian crocodiles were doubtless in existence, both 

 slender-nosed and broad-nosed, and some of them must have been 



