452 Comparative Morphology of Chordates 



Order Urodela (Caudata) 



"Tailed Amphibians." Body elongated. Adult retains larval tail. 

 Fore- and hindlegs of nearly equal size. Larval gills and gill-clefts 

 may or may not be retained by adult. Living mainly in the northern 

 hemisphere; most abundant in the more temperate parts of it. 



The following two divisions, based on gill-structures, are con- 

 venient, but probably have little phylogenetic significance. 



Perennibranchiata: Three pairs of external gills in adult. Wholly 

 aquatic. 



Necturus: Two pairs of gill-clefts in adult. Length, 12 to 15 inches. 

 Common "mud puppy" of eastern United States and Canada (Fig. 

 349C). 



Proteus: Two pairs of gill-clefts in adult. Three digits on foreleg, 

 two on hindleg. Skin almost devoid of pigment. The blind cave-dwelling 

 "'olm" of southern Europe. 



Siren (lacertina) : Three pairs of gill-clefts in adult. Eel-like in 

 form (Fig. 349D). Length, 2 feet or more. Forelegs weakly developed; 

 no hindlegs. "Mud eel" of southeastern United States. 



Caductbranchiata : Adult without gills. 



Cryptobranchus (alleganiensis, the only species) : Adult has 

 only one pair of gill-clefts. Wholly aquatic. The "hell-bender" of 

 eastern United States (Fig. 349E). Length, 18 inches or more. Con- 

 spicuous fold or "frill" of skin extending lengthwise of the body on 

 each side, probably serving to increase respiratory surface. 



Megalobatrachus (japonicus, the only species): Very similar to 

 Cryptobranchus; wholly aquatic, but with no gill-clefts in adult and 

 very much larger. Length, up to 5 feet or more. "Giant salamander" 

 of China and Japan; the largest living amphibian. 



Amphiuma: One pair of gill-clefts in adult. Wholly aquatic. Eel- 

 like in form; length, up to 3 feet. Both pairs of legs much reduced. 

 "Congo eel" of southeastern United States (Fig. 349B). 



In all caducibranchs except Cryptobranchus and Amphiuma, the 

 larval gill-clefts are entirely closed in the adult. The following genera 

 include some of the better-known salamanders and newts (Fig. 350). 



Ambystoma, common North American salamander; Salaman- 

 dra, European salamanders, mostly terrestrial; Triturus, common 

 American newt; Plethodon, Desmognathus, and other genera of the 

 Family Plethodontidae include the majority of American urodeles — 

 some brook-dwellers, some terrestrial, all lungless; Hynobius, Asiatic 

 land salamander; Ranodon, Asiatic brook-dweller with reduced lungs; 

 Onychodactylus, Asiatic genus including two lungless species. 



