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Modern sea turtles are not descended from more than one of the groups of sea-going turtles that have existed in the past they instead constitute a single radiation that became distinct from all other turtles at least 110 million years ago. Other pleurodires are also thought to have lived at sea, such as Araripemys and extinct pelomedusids. A lineage of unrelated marine testudines, the pleurodire (side-necked) bothremydids, also survived well into the Cenozoic. In Africa, the first marine turtle is Angolachelys, from the Turonian of Angola. The leatherback sea turtle is the only extant member of the family Dermochelyidae.įossil evidence of marine turtles goes back to the Late Jurassic (150 million years ago) with genera such as Plesiochelys, from Europe. The superfamily name Chelonioidea and family name Cheloniidae are based on the Ancient Greek word for tortoise: χελώνη ( khelone). All species except the leatherback sea turtle are in the family Cheloniidae. Sea turtles, along with other turtles and tortoises, are part of the order Testudines. Although this condition appears to resemble that found in the earliest known fossil reptiles (anapsids), it is possible it is a more recently evolved trait in sea turtles, placing them outside the anapsids. The skulls of sea turtles have cheek regions that are enclosed in bone. Other sea turtle species are smaller, ranging from as little as 60 cm (2 ft) long in the case of the Kemp's ridley, which is the smallest sea turtle species, to 120 cm (3.9 ft) long in the case of the green turtle, the second largest. The leatherback sea turtle is the largest sea turtle, reaching 1.4 to more than 1.8 m (4.6 to 5.9 ft) in length and weighing between 300 and 640 kg (661 to 1,411 lbs). However, the streamlined body plan reduces friction and drag in the water and allows sea turtles to swim more easily and swiftly. This tapering at both ends reduces volume and means that sea turtles cannot retract their head and limbs into their shells for protection, unlike many other turtles and tortoises. In general, sea turtles have a more fusiform body plan than their terrestrial or freshwater counterparts. Hatchling and sub-adult turtles do not exhibit sexual dimorphism it is not possible to determine their sex by looking at them. Adult female sea turtles have shorter tails, with a cloacal opening near the base. As adults, it is possible to tell male turtles from female turtles by their long tails with a cloacal opening near the tip. Descriptionįor each of the seven species of sea turtles, females and males are the same size. The only dermochelyid species of sea turtle is the leatherback. Sea turtles can be categorized as hard-shelled ( cheloniid) or leathery-shelled ( dermochelyid). The flatback turtle is found only in the waters of Australia, Papua New Guinea, and Indonesia. ![]() ![]() All but the flatback turtle are listed as threatened with extinction globally on the IUCN Red List of Threatened Species. ![]() waters, and are listed as endangered and/or threatened under the Endangered Species Act. Six of the seven sea turtle species, all but the flatback, are present in U.S. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerhead, Kemp's ridley, and olive ridley. Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. A green sea turtle, a species of the sea turtle superfamily
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