286 



SUBPHYLUM VERTEBRATA: 



tympanic membrane 



IGUANA 



SPHENODON 



Figure 16.21 A lizard. Iguana, and the tuatara, Sphenodon. 

 Morphology, Reinhold Publishing Corp., New York, 1962.) 



{From Malcolm Jollie, Chordate 



burrows, and water where it feeds upon fishes, in- 

 sects, and worms. Ahhough the tuatara lays eggs Hke 

 other reptiles, the eggs take a long time (about thir- 

 teen months) to hatch. The tuatara is called a "living 

 fossil" because the only other known members of the 

 order are fossils from Permian to Eocene, about 250 

 to 40 million years ago. 



ORDER SQUAMATA (Lizards and Snakes) 



Diagnosis: skin of horny scales or plates, outer 

 layer periodically shed; jaws with teeth; anus a trans- 

 verse slit; sexes separate, both suborders lay eggs or 

 female retains them; terrestrial, fresh-water, or ma- 

 rine. 



Although the combination of lizards and snakes 

 into a single order might be surprising, it is standard 

 practice because none of the so-called differences be- 

 tween lizards and snakes are completely reliable. 

 There are many snake-like lizards and some snakes 

 that bear vestiges of legs. Also, there are some Squa- 

 mata families that cannot be assigned definitely either 

 to the snakes or to the lizards. 



Suborder SAURIA (= LACERTIUA) (Lizards) 



Diagnosis: body usually slender and four-legged; 

 point of lower jar bone usually fused; eyelids usually 



present; tongue usually unforked; North American 

 species either with four legs or with movable eyelids 

 (Figure 16.21). 



Most of the lizards of North America lay eggs, but 

 in some the eggs are retained within the female's body 

 and the young born alive. Bearing of live young is 

 characteristic of some alligator, scaly, horned, and 

 night lizards, as well as the California legless lizard. 



Lizards capture their prey with the teeth or flick 

 it into the mouth with the tongue. They rarely 

 swallow the food whole; they crush small prey and 

 shake or tear large prey before swallowing. Some 

 lizards are very adept at "lapping up" insects. 



The only poisonous lizards are the beaded lizards, 

 the Gila monster and the Mexican beaded lizard. 

 Venom is produced by a lower jaw gland and secreted 

 at the base of several lower jaw teeth between the 

 teeth and lips. The teeth are a crude venom-injecting 

 apparatus, but they can inflict serious and sometimes 

 fatal bites to man. The venom-producing structure is 

 thought to be a carryover from an ancestral structure, 

 because the teeth of poisonous lizards are entirely 

 adequate for most defensive purposes and for eating. 

 The poisonous lizards feed upon bird eggs and fledg- 

 lings, nestling mammals, and other small lizards. 



The only beaded lizard found in the United States, 

 the Gila monster, ranges from northern Mexico 

 across Arizona, and barely enters Nevada, Utah, and 



