HIGHER CHORDATES 



289 



ever, the crocodile still attains a fair size in the West 

 Indies, Columbia, and Central America. 



Crocodilians generally lay their eggs in piles of 

 gathered vegetation. The decaying of the plants is 

 believed to produce sufficient heat to "incubate" the 



eggs. 



These animals are alert predators that tend to stalk 

 their prey. Food is quickly seized by the peg-like 

 teeth. Small prey is crushed and swallowed; larger 

 prey often is drowned and torn by the spinning of 

 crocodilians, and then is gulped down in sizeable 

 chunks. Such predaceous capabilities are a danger to 

 man. Some crocodilians use their tails to fell large 

 prey (this has happened to man) and knock the prey 

 into its jaws. 



The crocodilians date back to the Triassic Age, 225 

 million years age, and are closely related to dino- 

 saurs. The word "dinosaur" is applied to some of the 

 orders of the Subclass Archosauria, or "ruling rep- 

 tiles," and the Order Crocodilia is part of that sub- 

 class of the Class Reptilia. 



CLASS AVES (Birds) 



Diagnosis: skin not moist and glandular (except 

 on the tail, which has an oil or preening gland), dry, 

 with both scales and feathers; four limbs, front pair 



modified as wings that usually enable flight, hind- 

 limbs variously modified for support or swimming; 

 mouth modified as a beak; paired nostrils lead to 

 mouth; respiration by lungs; body temperature in- 

 ternally regulated; sexes separate, eggs laid typically 

 in some sort of constructed nest, no larval stage; 

 terrestrial, marine, and fresh-water. 



Subclass ARCHAEORNITHES (Lizard Birds) 



Diagnosis: includes Archaeopteryx, the Jurassic 

 toothed bird that clearly shows the reptilian ancestry 

 of birds. 



Subclass NEORNITHES (True Birds) 



Diagnosis: includes all modern birds and some 

 extinct, tooth-bearing forms; modern birds divided 

 into two taxa; walking or flightless birds include 

 ostriches, cassowarys, emus, elephant birds (extinct 

 for several centuries), moas (extinct for several cen- 

 turies), kiwis, rheas and tinamous (flying forms); 

 most walking birds are African, South American, or 

 Australian; remaining birds constitute modern birds 

 (Figure 16.24). 



Enumeration of the many living orders and any 

 other identification of birds is beyond the scope of 



PENGUIN 



APTERYX 



figure 16.24 Some variation extremes of the birds, including Apteryx, a kiwi. {From Malcolm 

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



