tur·tle / ˈtərtl/ • n. 1. a slow-moving reptile (family Testudinidae) of warm climates, enclosed in a scaly or leathery domed shell into which it can retract its head and thick legs. 2. (also sea turtle) a large marine reptile (families Cheloniidae and Dermochelyidae) with a bony or leathery shell and flippers, coming ashore annually on sandy beaches to lay eggs. ∎  the flesh of a sea turtle, esp. the green turtle, used chiefly for soup. 3. a freshwater reptile (Emydidae and other families) related to the turtles, typically having a flattened shell. Called terrapin in South Africa and India and tortoise in Australia. ∎  any reptile of this order, including the terrapins and tortoises. 4. Comput. a directional cursor in a computer graphics system that can be instructed to move around a screen.5. short for turtleneck.PHRASES: turn turtle (chiefly of a boat) capsize.

Turtle

There are about 260 species of turtles, tortoises, and terrapins. They range in size from the leatherback, a marine species reaching an upper shell length of about 190 centimeters (6.2 feet) and a weight of over 900 kilograms (1,984 pounds), to small freshwater species that average around 10 centimeters (3.9 inches) in length and weigh less than 100 grams (a few ounces). Turtles are no longer classified as reptiles but are considered a distinct and unique evolutionary lineage of terrestrial vertebrates, the class Chelonia. Possession of an upper (carapace) and lower (plastron) shell in combination with a skull that lacks temporal ("the temple") openings behind the eye socket sets turtles distinctly apart from amphibians, reptiles, tuataras, crocodilians, and birds. Over their 210-million-year history since the late Triassic, turtles have remained conservative in retaining a shell, their distinctive skeletal feature, but at the same time demonstrating an amazing diversity during their evolution, from sleek, flexible water-loving softshell turtles to high-domed, land-dwelling galapagos tortoises.

All turtles are egg-layers; females dig nests in which to lay their eggs but like amphibians provide no maternal care after hatching (as in crocodilians and birds). Some turtles, such as softshells, snapping turtles, and diamondback terrapins, have commercial value and have been regularly consumed as food by people. Turtles are popular in the pet trade, and many species have been adversely impacted by overcollecting. In addition, the natural habitats of turtles are disappearing at an alarming rate, due to human overpopulation worldwide.

see also Amphibian; Crocodilians; Extinction; Reptile

Joseph T. Collins

Bibliography

Halliday, Tim R., and Kraig Adler. The Encyclopedia of Reptiles and Amphibians. New York: Facts on File, 1986.

Pough, F. Harvey, et al. Herpetology. Upper Saddle River, NJ: Prentice Hall, 1998.

turtle2 the name turtle is an alteration (originally by English sailors) of tortoise. The flesh of various species of the turtle is used as food, and it was traditionally regarded as a feature of civic banquets; in the late 19th century the term turtledom was coined for aldermen as consumers of turtle-dinners.

In Terry Pratchett's Discworld series, the world is said to be supported by four elephants carried on the back of a giant turtle; the idea of the universe supported on a turtle's back is derived from Hindu mythology.
turn turtle chiefly (of a boat) turn upside down. From turtle-hunters' flipping over turtles on to their backs to render them helpless. Used figuratively from the early 19th century for turning upside down something held to resemble a turtle in shape.

turtle Reptile found on land or in marine and fresh waters. Turtles have the most ancient lineage of all reptiles, preceding even the dinosaurs. They have a bony, horn-covered, boxlike shell (carapace) that encloses shoulder and hip girdles and all internal organs. All lay eggs on land. Terrestrial turtles are usually called tortoises, and some edible species found in brackish waters are called terrapins. Marine turtles have smaller, lighter shells. Length: 10cm–2m (4in–7ft). Order Chelonia.

turtle Marine reptile; the main species for food is the green turtle, Chelonia mydas, so called because of the greenish tinge of its fat. It is farmed to a small extent, but mainly caught in the wild. See also calipash; mock turtle.