282 



SUBPHYLUM VERTEBRATA: 



and resemble adults; three species strictly aquatic 

 and limited to Atlantic Coastal Plain, southeastern 

 states, Mississippi drainage, and northeastern Mex- 

 ico (Figure 16.17). 



The sirens normally are included within the Order 

 Caudata. However, there is sufficient anatomical 

 and paleontological evidence to suggest their inde- 

 pendence from salamanders and perhaps to assume 

 they are more closely related to caecilians. 



Figure 16.17 S/ren, one of the fwo living genera of sirens (to about 3 

 feet long). 



ORDER CAUDATA (= URODELA) (Salamanders) 



Diagnosis: lizard-like, body with distinct head, 

 trunk, and tail, typically with four legs, (four in all 

 North American species) of equal size; skin smooth 

 and moist, without scales; fertilization external or 

 internal; eggs laid in water, on land, rarely retained; 

 larva resembles adult, often aquatic, many larvae 

 develop within eggs laid on land and a very few larva 

 are developed in the female (Figure 16.18). 



Salamanders have many other names regularly 

 applied to them. For example, certain aquatic forms 

 are called hellbenders, congo eels, or newts (or water- 



dogs). However, we shall use ''salamander" to apply 

 to all Caudata. 



The word "salamander" dates back to mythology, 

 referring to a mythical animal having the power to 

 endure fire without harm. These amphibians prob- 

 ably were associated with this myth because on occa- 

 sion they crawl out of logs placed into fires. In gen- 

 eral appearance, they resemble lizards; however, 

 salamanders have a smooth, moist skin rather than a 

 dry, scaly one. Most of these amphibians are retiring 

 in their habits in that they do not attempt to "fight 

 off" predators. Some rely upon poisonous skin secre- 

 tions to discourage predators. Another has poison 

 glands in its tail, and will swing its tail in the direc- 

 tion of disturbance. If strongly pressed, this animal 

 sheds its tail, a behavior similar to that of many 

 lizards. A few salamanders sometimes bite potential 

 predators and humans handling them, but the Pacific 

 giant salamander is the only formidable "fighter" in 

 North America. The latter species may also bite 

 humans and is known to have killed a garter snake. 



Salamanders are carnivorous throughout their life 

 history. The primitive pattern of life history involves 

 courtship and egg-laying in water, the hatching of 

 gilled larvae that are otherwise much like the adults, 

 and metamorphosis to the adult form. The adults 

 may be terrestrial, only coming back to ponds during 

 the spring breeding season, or may be gilled and 

 never leave the water. However, most salamanders 

 (mostly in one family that lacks both lungs and gills) 

 do not have an aquatic stage. These terrestrial lung- 

 less salamanders (lung function is taken over by the 

 mouth, throat, and parts of the skin) lay their eggs 

 in moist, usually hidden, spots on land. Their eggs 

 develop into a larval stage which transforms to the 

 adult before hatching. A very few land salamanders 

 bear their young alive, the mother giving nourishment 

 to the developing young. 



ORDER SAUENTIA (= ANURA) (Frogs and Toads) 



Diagnosis: head broadly joined to body, without 

 neck or tail; four legs, hind legs longer for leaping; 

 skin smooth to warty, moist, without scales; fertiliza- 

 tion usually external, eggs usually deposited in water 

 and hatch to a tadpole larva (polliwog), adults aquatic 

 or terrestrial; eggs may be carried by males in vari- 

 ously distributed brood pouches (Figure 16.19). 



The Anura or Salientia are called frogs or toads. 

 These common names have no meaning insofar as re- 



