232 VERTEBRATE ZOOLOGY 



THE FOUR ORDERS OF LIVING REPTILES 



The order Prosauria is represented to-day by one genus, Sphen- 

 odon, placed in the family Rhynchocephalia. The order Chelonia is 

 represented by two sub-orders and several large families. The order 

 Crocodilia is to-day a minor order, represented by only a few species 

 of large reptiles. The order Sauria contains a large proportion of liv- 

 ing reptiles, since to it belong the lizards and the snakes. 



ORDER PROSAURIA (RHYNCHOCEPHALIA) 



The only representative of this order now living is Sphenodon (Hair 

 teria) pundatum (Fig 132, A), the "tuatara" of the Maories of New 

 Zealand. Gadow refers to this species as "the last living witness of 

 by-gone ages, this primitive, ahnost ideally generalized type of rep- 

 tile, this ' living fossil.' " This ahnost reverential attitude toward the 

 antiquity of this reptile has, however, broken down through the dis- 

 covery that Paleohatteria, the extinct type which was supposed to 

 hnk Sphenodon with the remote past, is really more nearly an an- 

 cestral Hzard than an ancestral Sphenodon; a fact that led such an 

 authority as Williston to assert that some of our modern lizards are 

 more primitive than is Sphenodon. 



The tuatara is decidedly primitive in some features. There is no 

 penis; the centra of the vertebrae are amphiccelous; the first three 

 basiventralia are quite large; and the skeletal structure of both limbs 

 and girdles is primitive. The skull (Fig. 132, B, C, D) is an ahnost 

 ideally generalized reptilian skull and well repays study. 



Sphenodon is facing extinction at the present time. Already it has 

 disappeared from the mainland and is confined to a few small islands 

 off the coast of New Zealand. For years it has been assiduously 

 hunted by the Maories who consider its flesh an unusual delicacy. 

 Unless protected it will soon go the way of its extinct ancestors and 

 will be represented only by a few specimens in our museums. 



The tuatara is nocturnal in habits, living in burrows during the day. 

 It shares its capacious burrow with various kinds of petrels, with 

 which it lives on apparently amicable terms. It will not tolerate any 

 other species of guest, not even other individuals of the same species, 

 and viciously attacks any invader no matter how formidable. Its 

 lizard-like aspect is only skin deep; for it requires only a very casual 



