HIGHER CHORDATES 



285 



performed during the year are reproduction, feeding, 

 obtaining moisture, basking, and escaping harm. 

 Spring is the peak of activity and is the breeding 

 season in most species. This spring peak is gradually 

 reduced to the minimal activity of summer. In the 

 summer the reptiles may go into a coma-like aestiva- 

 tion or become crepuscular or nocturnal rather than 

 diurnal. Activity then rises in the fall and once again 

 is reduced in the winter. In the latter period some 

 reptiles go into a coma-like hibernation. These activi- 

 ties are generally associated with temperature and 

 moisture rather than light. 



Reptiles are more independent of their environ- 

 ment than are amphibians. Although reptiles depend 

 upon the environment as a heat source, they are more 

 independent of this heat. For example, in the same 

 habitat and at the same time different species may 

 maintain different normal activity temperature 

 ranges. Reptiles show much greater tolerance to low 

 humidity and saline waters. Some reptiles actually 

 live in the ocean. Notable are the poisonous sea 

 snake and certain turtles which are almost completely 

 marine, but some lizards and crocodilians are often 

 found in marine shore waters. 



Reptiles also show greater diversity in protective 

 methods against their enemies. Most reptiles can 

 leave an area of danger faster than amphibians can; 

 some reptiles have protective armor (turtles), head 

 spines (horned lizards), shed their tail (lizards), have 

 offensive weapons (especially venomous snakes), or 

 are protectively colored to blend into their back- 

 ground (many species). Amphibians tend to have 

 these protective devices to a lesser degree. 



ORDER TESTUDINATA(= CHELONIA) (Turiles) 



Diagnosis: body oval, generally within a bony 

 shell; shell of rounded dorsal carapace and flat ven- 

 tral plastron; jaws with horny sheaths, without teeth; 

 anus a longitudinal slit; sexes separate, eggs buried 

 byfemale; terrestrial, fresh-water, and marine (Figure 

 16.20). 



All Testudinata may be called turtles; however, 

 the name "tortoise" is sometimes reserved for land 

 species and "terrapin" for certain edible fresh-water 

 species. 



Turtles have been turtles since the Triassic, about 

 200 million years ago. There are now about three 

 hundred species widely distributed over the warmer 

 parts of the earth. Although there are fresh-water 



Figure 16.20 C/emmys, a fresh-water turtle. (After Van Denburgh.) 



and marine species, all turtles lay their eggs on land 

 in an underground cavity that is excavated by the 

 female's hind legs. Turtles usually have external 

 sexual differences, the male usually having a longer 

 tail and the anal (actually cloacal) opening farther 

 out on the tail. Males also tend to have the underpart 

 of their shells concave. 



Turtles tend to be unspecialized in food habits, 

 eating either plant or animal food. In general, they 

 obtain their animal prey either by waiting for it to 

 come along, or by stalking it and lunging at it. Al- 

 though turtles lack teeth, they have rather sharp, 

 horny jaws that cut cleanly like scissors. Small food 

 items may be engulfed whole but usually are grabbed 

 by the jaws and cut and torn while being held by the 

 turtle's front feet. Large prey must be eaten piece- 

 meal. 



Aquatic species usually pull their prey underwater 

 before eating it. One aquatic species has remarkable 

 feeding specialization. The alligator snapping turtle 

 of the lower Mississippi Valley and Gulf Coast has 

 a worm-like tongue. This turtle opens its mouth 

 while underwater and wiggles its tongue. The tongue 

 lures fish, and when a fish comes the turtle snaps its 

 mouth closed. 



ORDER RHYNCHOCEPHAUA (Tuafara) 



Diagnosis: one living species, lizard-like; jaws with 

 teeth; anus a transverse slit; unique skeletal char- 

 acteristics; sexes separate, female lays eggs; alternate 

 habitats (see Figure 16.21). 



The only living species is the lizard-like tuatara of 

 New Zealand. It alternates its activities among land, 



