turtle stone: see concretion.

turtle, a reptile of the order Chelonia, with strong, beaked, toothless jaws and, usually, an armorlike shell. The shell normally consists of bony plates overlaid with horny shields. The upper portion, or carapace, covers the turtle's back and sides, and the lower portion, or plastron, covers the belly; the two parts are joined at the sides. Exceptions are the rare plateless turtles of New Guinea and the marine leatherback turtle, which is encased in a thick, ossified skin resembling a carapace. When startled, most turtles withdraw their heads straight back into their shells, the neck folding into an S-shaped curve. However, in the side-necked turtles of the Southern Hemisphere, the head moves sideways and tucks next to the shoulder.

Turtles are found throughout most of the temperate and tropical world and in the open ocean; of the 270 known species, 42% are rare or threatened with extinction. Many turtles and their eggs are valued as food. Edible species include several marine turtles, the green turtle (traditional ingredient of turtle soup), the diamondback terrapin, and the soft-shelled turtles. Catching females when they lay eggs on land has contributed to a serious decline in many species, since it can take 10 to 30 years for some turtles to reach sexual maturity.

Different types of turtle are variously adapted to living on land, in freshwater, or in the ocean, but all turtles breathe by means of lungs, and all lay eggs on land. The land-living species, especially those of the family Testudinidae, are commonly called tortoises. The name terrapin is generally applied to large freshwater or brackish water species, especially those used for food. Turtle species are either herbivorous or carnivorous but rarely both. They range in length from a few inches to over 6 ft (2 m), most being between 5 in. and 15 in. (13-38 cm) long. Many specimens have survived more than 50 years in captivity, and one giant tortoise is known to have lived 152 years.

Turtles existed 200 million years ago, at the time of the earliest dinosaurs; these early land-dwelling turtles could not retract their necks. By 120 million years ago some turtles had adapted to an aquatic life. Many of the living families of turtles existed in the Cretaceous period and have undergone very little change since then. On the basis of morphological (body structure) evidence, turtles were thought to be the oldest surviving group of reptiles. However, molecular studies comparing genes in different reptile groups indicate that turtles, along with crocodiles, are the most modern of reptiles.

Types of Turtles

Turtles are classified in 12 families. The Northern Hemisphere's largest family is that of common freshwater turtles (Emydidae), which includes about a third of all turtle species and is abundant in S and E Asia, E North America, and Central America. Members of this group have webbed feet; many spend most of the time in freshwater ponds or marshes; some live in brackish estuaries. They include such well-known North American turtles as the pond turtles (including the spotted, wood, and Muhlenberg's turtles), the painted turtle, the sliders, the diamondback terrapin, and the Blanding's turtle. The box turtle, which is primarily terrestrial, belongs to this family. Land tortoises (Testudinidae) form the second largest family. Tortoises have high-domed shells, move on club-shaped feet, are vegetarian, and live in warm regions throughout the world. The musk turtles and mud turtles (family Kinosternidae) are common small turtles of the E United States, and are found only in the Americas. The soft-shelled turtles (family Trionychidae) are flat-bodied, carnivorous freshwater turtles of the Northern Hemisphere, with a leathery covering instead of horny shields on their shells. The snapping turtle family (Chelydridae) is a North American group that includes the common snapper and the alligator snapper.

Marine turtles are classified in two families. The family Chelonidae includes five sea turtle species of tropical and subtropical distribution: the green turtle, the loggerhead, the hawksbill (or tortoiseshell turtle), the Kemp's ridley, and the olive ridley. The family Dermochelidae includes only one species, the leatherback, or leatherneck, largest and heaviest of all turtles, weighing as much as 1100 lbs (500 kg). Marine turtles lack toes, and their legs are oarlike, allowing speeds of nearly 20 mph (32 kph) in the water. With the exception of the loggerhead, all are endangered, either by pollution with plastic debris, which some turtles eat by mistake, or by commercial fishing, especially shrimp trawling. Commercial trade in all endangered sea turtles is banned; however, many wild turtles are skinned for leather and tortoiseshell ornaments, or taken for food.

Classification

Turtles are classified in the phylum Chordata, subphylum Vertebrata, class Reptilia, order Chelonia.

snapping turtle, large, aggressive New World freshwater turtle. The two snapping turtle species are the sole members of the family Chelydridae. Snapping turtles prefer quiet, muddy water. They spend most of their time submerged, surfacing periodically to breathe. They feed on fish and other aquatic animals as well as on vegetation and decaying matter; they are valuable scavengers. They have long necks, powerful jaws, and fierce dispositions, lunging at aggressors and biting them. The common snapping turtle, or snapper (Chelydra serpentina), is found from SE and S central Canada to NE South America. The adult is often over 18 in. (45 cm) long and weighs over 30 lb (14 kg); some specimens weigh twice as much. The alligator snapper (Macrochelys temmincki) is found in the SE United States and the Mississippi valley. One of the world's largest turtles, it may reach a length of 30 in. (75 cm) and weigh 200 lb (90 kg). It has a muscular, wormlike projection on the tongue, which it uses as a fishing lure as it lies concealed in the mud of a river bottom. Snapping turtles lay their eggs in the ground in early summer, often at some distance from water. The eggs, about 20 in a clutch, hatch after a 10-week incubation, and the young find their way to water. Snapping turtles are classified in the phylum Chordata, subphylum Vertebrata, class Reptilia, order Chelonia, family Chelydridae.

snake-necked turtle: see side-necked turtle.

side-necked turtle, name for the long-necked turtle of the families Chelidae and Pelomedusidae, found only in the Southern Hemisphere. The neck in these two families is of a different structure from that of other turtles and is folded sideways under the shell for concealment instead of being pulled straight back. Members of the family Chelidae, sometimes called snake-necked turtles, are river turtles of South America and the Australia-New Guinea region. Several species have slender, elongated snouts. Among these is the matamata (Chelys fimbriata) of Brazil and N South America. The matamata is a weak-jawed turtle that lies in wait for its prey, chiefly fish, and sucks it up with the snout. Its shell has high bumps and is covered with moss and water plants, so that when motionless the turtle looks like a rock. The family Pelomedusidae includes two African genera, Pelomedusa and Pelusios. Members of the latter genus resemble the North American box turtles, with a hinged shell. A third genus, Podocnemis, is found in rivers of South America and Madagascar. Side-necked turtles are classified in the phylum Chordata, subphylum Vertebrata, class Reptilia, order Chelonia.

sea turtle, name for several species of large marine turtles found in tropical and subtropical oceans. These turtles are modified for life in the ocean by having flipperlike forelimbs without toes and lightweight shells. Their heads are too large to be withdrawn into the shell. They spend most of their lives in the water, but come ashore to lay their eggs. All sea turtle species are declining in numbers, owing in large part to the destruction of the eggs, which are widely used as food in tropical regions. Sea turtle meat is also eaten, and there is a market for turtle oil, hide, and shell. In a few places, such as Sarawak, harvesting of eggs is regulated by law to insure propagation of the species. The size of sea turtles has also decreased, owing to the hunting of large specimens. Nearly all species have a circumglobal distribution although there are differences between the Atlantic and the Pacific populations. Most sea turtles are found in North American waters as far N as the U.S. S Atlantic coast and Baja California. All but one species belong to the family Chelonidae. The green turtle, Chelonia mydas, with greenish to brownish skin and shell, formerly reached weights of 1,000 lb (450 kg); the largest now found are about 4 ft (120 cm) long and weigh about 500 lbs (225 kg). The green turtle feeds chiefly on marine vegetation and is most abundant in shallow water. The loggerhead, Caretta caretta, is a large-headed brown to reddish turtle. Chiefly carnivorous, it ranges from open oceans to coastal salt marshes and stream mouths. Like the green turtle it sometimes comes ashore to bask in uninhabited places. The hawksbill, or tortoiseshell turtle, Eretmochelys imbricata, may reach 30 in. (75 cm) in length and weigh 100 lbs (45 kg). The horny plates of its shell are translucent and have a variegated color pattern, chiefly brown and yellow. These plates have long been valued for the making of ornamental objects. Although tortoise-shell has to a large extent been replaced in many applications by plastic, a renewed demand for the genuine material poses a serious threat to the hawksbill. The ridleys, the smallest sea turtles, inhabit shallow offshore waters. The 2-ft (60-cm) long, gray Atlantic ridley, Lepidochelys kempii, breeds only in the Gulf of Mexico, although the young are often carried by the Gulf Stream to the Carribean Sea and Europe. The slightly larger, greenish Pacific ridley, or oliveback (L. olivacea), is found in the Indian and Pacific oceans. The leatherback is the largest of all turtles and, although a marine turtle, belongs to a separate family. All sea turtles other than the leatherback are classified in the phylum Chordata, subphylum Vertebrata, class Reptilia, order Chelonia, family Chelonidae.

green turtle: see sea turtle.

box turtle, hard-shelled land turtle of the genus Terrapene, native to North America. Its lower shell, or plastron, has a hinge dividing it into front and rear sections; the animal can raise these sections to meet the upper shell, or carapace, forming a secure box around its body. It is primarily a vegetarian, although it also eats insects, earthworms, and slugs. The box turtle hibernates during cold winters and mates in the spring. In summer the female buries from two to seven eggs, which hatch out in the early fall. The young often remain in the nest until the following spring. The Eastern box turtle, Terrapene carolina, is a woodland species found in the eastern and central United States. The Western species, T. ornata, is found in the grasslands of the central United States and northern Mexico. There are also several rare Mexican species. Box turtles are classified in the phylum Chordata, subphylum Vertebrata, class Reptilia, order Chelonia, family Emydidae.

Little Turtle, c.1752-1812, chief of the Miami, born in a Miami village near present-day Fort Wayne, Ind. He was noted for his oratorical powers, military skill, and intelligence. He was a principal commander of the Native Americans in the defeat of Gen. Josiah Harmar on the Miami River in 1790 and of Gen. Arthur St. Clair on the Wabash River in 1791. After several attacks on the forces of Gen. Anthony Wayne, he counseled peace but was overruled. Consequently he was not in command at Fallen Timbers. He reluctantly signed the Treaty of Greenville (Ohio) in 1795, ceding a great part of Ohio to the whites, and he also signed several subsequent treaties. Later he refused to join Tecumseh's confederacy against the whites. He persuaded many of the Miami to turn to agriculture and appealed to the government to halt the liquor trade among his people.

Species (Streptopelia turtur, family Columbidae) of migratory European pigeon that winters in northern Africa. It is about 11 in. (28 cm) long and has a reddish brown body, blue-gray head, and white-tipped tail. A ground feeder, it eats prodigious amounts of small seeds. The name is applied to other temperate and tropical Old World Streptopelia species of slim, fast-flying game birds. The ringed turtledove, or ringdove, has feral populations in California and Florida, U.S.; the laughing and spotted doves have also been introduced outside their native habitats.

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Any of approximately 300 species (order Testudines) of reptiles that have a bony shell overlaid with horny shields and are found in most parts of the world. Turtles have existed for 200 million years, making them the oldest of all surviving reptiles. Most species are aquatic or semiaquatic; some are terrestrial. Turtles eat plants, animals, or both. They are toothless, have a horny beak, and range from less than 4 in. (10 cm) to more than 5 ft (1.5 m) long. They have sturdy, sprawling limbs with short feet or paddlelike flippers (marine turtles). Some species bend the neck sideways, but most pull the head and neck backward into the shell. Almost half of the known turtle species are rare, threatened, or endangered. Seealso box turtle; painted turtle; snapping turtle; softshell turtle; terrapin; tortoise.

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Any of more than 30 species (family Trionychidae) of swift-moving carnivorous turtles found in North America, Africa, and Asia. Thriving in fresh waters that have soft sandy or muddy bottoms, they often lie buried in mud or sand and occasionally emerge to bask in the sun. They have a pancakelike leathery shell, webbed feet, a long neck, and an elongated snout. Aggressive when captured, they can deliver rapid, vicious bites. North American species have a grayish or brown shell, 14–18 in. (35–45 cm) long. Two Old World species grow to 24 in. (60 cm) or more.

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Either of two species (family Chelydridae) of edible, omnivorous, freshwater turtles found in North and Central America. They are tan to black and have a rough upper shell, a small cross-shaped lower shell, a long tail, and a large head with hooked jaws. Known for their fierceness, they lunge at aggressors and prey and bite them with their powerful jaws. The common snapping turtle (Chelydra serpentina) has a shell 8–12 in. (20–30 cm) long and weighs 10–35 lbs (4.5–16 kg). The alligator snapping turtle (Macroclemys temmincki), the largest freshwater turtle in the U.S., has a shell 16–28 in. (40–70 cm) long and weighs 40–155 lbs (18–70 kg). It lies quietly on the bottom of slow moving bodies of water, luring fishes by means of a wormlike appendage on the floor of its open mouth.

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Species (Chrysemys picta, family Emydidae) of brightly marked North American turtle found from southern Canada to northern Mexico. It has a smooth shell, 4–7 in. (10–18 cm) long, with red and yellow markings on its relatively flat, black or greenish brown upper shell. It usually lives in quiet, shallow bodies of fresh water, especially those with thickly planted mud bottoms, feeding on plants, small animals, and some carrion. It often basks in large groups on logs and other objects. In many areas it hibernates.

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Any of several species of terrestrial turtles found in the U.S. and Mexico (genus Terrapene) or the subtropical and tropical regions of Asia (genus Cuora). Box turtles have a high, rounded upper shell (carapace) that grows to a maximum length of about 7 in. (18 cm). The lower shell (plastron) is hinged across the centre and can be drawn very tightly against the carapace to form a protective “box” that completely encloses the turtle's soft parts. Box turtles feed on earthworms, insects, mushrooms, and berries and are often kept as pets.

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(born circa 1752, near Fort Wayne, Ind.—died July 14, 1812, Fort Wayne, Ind., U.S.) American Indian leader. Chief of the Miami tribe, he led raids on settlements in the Northwest Territory in the early 1790s. Defeated by Gen. Anthony Wayne at the Battle of Fallen Timbers (1794), he was obliged to sign the Treaty of Greenville (1795), which ceded to the U.S. much of Ohio and parts of Illinois, Indiana, and Michigan. He then advocated peace and prevented the Miami from joining the Shawnee confederacy of Tecumseh.

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