Savage, Jay M. Department of Biology, University of Miami, Coral Gables, Florida.
Gaffney, Eugene S. Department of Vertebrate Paleontology, American Museum of Natural History, New York, New York.
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An order of the class Reptilia, including the turtles, terrapins, and tortoises; also termed Testudines. The order Chelonia (often referred to as Testudines) comprises one of the oldest groups of reptiles on Earth. Members of the Chelonia (chelonians) first appeared in the Triassic Period, being among the commonest fossils from that time. Extant chelonians [including such popular species as box turtles (Fig. 1) and the painted turtle (Fig. 2)] are most frequently found in freshwater streams, lakes, and ponds or in marshy areas. However, a number of strictly terrestrial species are known (Fig. 3), and several species are marine (Fig. 4). Turtles occur on all the major continents and continental islands in tropic and temperate regions. The marine forms are basically tropic in distribution, but some individuals stray into temperate waters. In some classification schemes, Chelonia has been assigned the status of a superorder, containing extant members of turtles, extinct forms, and all related ancestors. Under these circumstances, the term Testudines (alternatively, Chelonii or Testudinata) denotes the order of living and extinct turtles. See also: Fossil; Reptilia; Triassic; Zoogeography
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