Turtles are reptiles of the order Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira and Cryptodira, which differ in the way the head retracts. There are 360 living and recently extinct species of turtles, including land-dwelling tortoises and freshwater terrapins. They are found on most continents, some islands and, in the case of sea turtles, much of the ocean. Like other amniotes they breathe air and do not lay eggs underwater, although many species live in or around water.
Sea turtles, sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerhead, Kemp's ridley, and olive ridley. Six of the seven sea turtle species, all but the flatback, are present in U.S. waters, and are listed as endangered and/or threatened under the Endangered Species Act. All but the flatback turtle are listed as threatened with extinction globally on the IUCN Red List of Threatened Species. The flatback turtle is found only in the waters of Australia, Papua New Guinea, and Indonesia.
The Trionychidae are a taxonomic family of a number of turtle genera, commonly known as softshell turtles. The family was erected by Leopold Fitzinger in 1826. Softshells include some of the world's largest freshwater turtles, though many can adapt to living in highly brackish areas. Members of this family occur in Africa, Asia, and North America, with extinct species known from Australia. Most species have traditionally been included in the genus Trionyx, but the vast majority have since been moved to other genera. Among these are the North American Apalone softshells that were placed in Trionyx until 1987.
The leatherback sea turtle, sometimes called the lute turtle, leathery turtle or simply the luth, is the largest of all living turtles and the heaviest non-crocodilian reptile, reaching lengths of up to 2.7 metres and weights of 500 kilograms (1,100 lb). It is the only living species in the genus Dermochelys and family Dermochelyidae. It can easily be differentiated from other modern sea turtles by its lack of a bony shell; instead, its carapace is covered by oily flesh and flexible, leather-like skin, for which it is named. Leatherback turtles have a global range, although there are multiple distinct subpopulations. The species as a whole is considered vulnerable, and some of its subpopulations are critically endangered.
The Blanding's turtle is a semi-aquatic turtle of the family Emydidae. This species is native to central and eastern parts of Canada and the United States. It is considered to be an endangered species throughout much of its range. The Blanding's turtle is of interest in longevity research, as it shows few or no common signs of aging and is physically active and capable of reproduction into eight or nine decades of life.
The alligator snapping turtle is a large species of turtle in the family Chelydridae. The species is endemic to freshwater habitats in the United States. M. temminckii is one of the heaviest living freshwater turtles in the world. It is the largest freshwater species of turtle in North America. It is often associated with, but not closely related to, the common snapping turtle, which is in the genus Chelydra. The specific epithet temminckii is in honor of Dutch zoologist Coenraad Jacob Temminck.
The painted turtle is the most widespread native turtle of North America. It lives in relatively slow-moving fresh waters, from southern Canada to northern Mexico, and from the Atlantic to the Pacific. They have been shown to prefer large wetlands with long periods of inundation and emergent vegetation. This species is one of the few that is specially adapted to tolerate freezing temperatures for extended periods of time due to an antifreeze-like substance in their blood that keeps their cells from freezing. This turtle is a member of the genus Chrysemys, which is part of the pond turtle family Emydidae. Fossils show that the painted turtle existed 15 million years ago. Three regionally based subspecies evolved during the last ice age. The southern painted turtle (C. dorsalis) is alternately considered the only other species in Chrysemys, or another subspecies of C. picta.
Turtle soup, also known as terrapin soup, is a soup or stew made from the meat of turtles. Several versions of the soup exist in different cultures, and it is often viewed as a delicacy.
The golden coin turtle, also known commonly as the Chinese three-banded box turtle and the Chinese three-striped box turtle, is a species of turtle in the family Geoemydidae. The species is native to southern China. There are two recognized subspecies.
The Japanese pond turtle, also called commonly the Japanese pond terrapin and the Japanese pond tortoise, is a species of turtle in the family Geoemydidae endemic to Japan. Its Japanese name is nihon ishigame, Japanese stone turtle. Its population has decreased somewhat due to habitat loss, but it is not yet considered a threatened species.
Toxochelys is an extinct genus of marine turtle from the Late Cretaceous period. It is the most commonly found fossilized turtle species in the Smoky Hill Chalk, in western Kansas.
Desmatochelys is an extinct genus of sea turtles belonging to the family Protostegidae. This genus contains two known species, D. lowii and D. padillai. D. lowii was first discovered in 1895, followed by D. padillai in 2015. Having been estimated at over 120 million years old, D. padillai is currently the oldest known species of sea turtle.
Dorsetochelys is an extinct genus of turtle from the Early Cretaceous of southern England and northwestern Germany.
Pleurosternon is an extinct genus of freshwater pleurosternid turtle from the latest Jurassic to earliest Cretaceous of Europe. Its type species, P. bullockii was described by the paleontologist Richard Owen in 1853. Since then, and throughout the late 19th century, many fossil turtles were incorrectly assigned to this genus, though only two are currently considered valid.
Plesiochelys is a genus of late Jurassic European and Asian turtle. The type species is Plesiochelys etalloni.
Neurankylus is an extinct genus of turtles in the family Baenidae that lived between 112 and 61 million years ago in Canada and the United States. It was originally placed within the monotypic family Neurankylidae, but it has since been placed in the Neurankylinae, alongside Trinitichelys. The type species, Neurankylus eximius, was described by Lawrence Lambe in 1902. The species N. lithographicus was discovered in the Milk River Formation (Canada), alongside the holotype of the pachycephalosaurid dinosaur Acrotholus audeti.
The Helochelydridae are an extinct family of stem-turtles known from fossils found in North America and Europe spanning the Early to Late Cretaceous.
Rhinochelys is an extinct genus of sea turtles belonging to the family Protostegidae.
Hylaeochelys is an extinct genus of plesiochelyid turtle that lived during the Late Jurassic-Early Cretaceous in Portugal, Spain, France, and southern England. The type species was originally named by Richard Owen as Pleurosternon latiscutatum in 1853, before being moved to the new genus Hylaeochelys by Richard Lydekker in 1889. Other species included in the genus are H. belli, H. kappa and H. lata, originally named under different genera by Gideon Mantell and Owen, respectively. All species are represented by carapaces, primarily from the Lulworth Formation of the Purbeck Limestone Group that was deposited during the Berriasian.
Compsemydidae is an extinct family of turtles, likely belonging to the clade Paracryptodira. The earliest undisputed member is Tongemys from the Berriasian age of the Early Cretaceous; two Late Jurassic genera have also sometimes been included in the group, but may alternatively be members of the family Pleurosternidae. The genus Compsemys survived the Cretaceous–Paleogene extinction event and lasted until the Thanetian age of the Paleocene.
