172 



WATER REPTILES OF THE PAST AND PRESENT 



the Rhynchocephalia (p. 176) of which the SpJienodon, or tua- 

 tera, of New Zealand is the only living representative, but whose 

 direct genealogical history- runs back nearly or quite to the time 

 in which the thalattosaurs lived. On the other hand, there are so 

 many resemblances to the mosasaurs shown in the remains that 

 have been discovered, that it is possible the thalattosaurs were only 

 a short-lived branch of the primitive lizards, which we also know 

 were in existence at the time when the thalattosaurs lived. How- 

 ever, even though they resembled the mosasaurs, there could have 

 been no direct genealogical relationships between them, for it is 

 quite certain that the thalattosaurs very soon went out of exist- 

 ence, leaving no descendants. But it matters Little which were 

 the land forbears of the thalattosaurs; they present such distinct 

 adaptations to water life — characters all their own — that their 



Fig. 82. — Skull of ThalaUosaiirus. (After Merriam) 



ancestral kinship may well be left to the future researches of the 

 curious paleontologist. For the present, at least, they may well 

 be placed in an order of reptiles all their own, as Professor Merriam 

 has proposed — the Thalattosauria. 



No thalattosaurs were large animals. If they had the same 

 proportions between the lengths of head, body, and tail as the 

 mosasaurs, none exceeded seven feet in length, and they may have 

 been even shorter, though probably not much. The figure of the 

 skull, as restored by Professor Merriam, shows many striking 

 aquatic adaptations, in the elongated, pointed muzzle, in the large 

 external nostrils, situated far back toward the eyes, and in the well- 

 ossified ring of bones surrounding the eyeball. There is a parietal 

 opening in the roof of the skull, as in the modern hzards and 

 tuatera; but it is not known for certainty whether there were two 



