Turtle

[13] During development, the ribs grow sideways into a carapacial ridge, unique to turtles, entering the dermis (inner skin) of the back to support the carapace.

[23] The turtle's skull is unique among living amniotes (which includes reptiles, birds and mammals); it is solid and rigid with no openings for muscle attachment (temporal fenestrae).

The cone cells contain oil droplets placed to shift perception toward the red part of the spectrum, improving color discrimination.

[43] Experiments on green sea turtles showed they could learn to respond to a selection of different odorant chemicals such as triethylamine and cinnamaldehyde, which were detected by olfaction in the nose.

[44] The rigid shell of turtles is not capable of expanding and making room for the lungs, as in other amniotes, so they have had to evolve special adaptations for respiration.

They can moderate the increase in acidity during anaerobic (non-oxygen-based) respiration by chemical buffering and they can lie dormant for months, in aestivation or brumation.

Large species, both terrestrial and marine, have sufficient mass to give them substantial thermal inertia, meaning that they heat up or cool down over many hours.

The Aldabra giant tortoise weighs up to some 60 kilograms (130 lb) and is able to allow its temperature to rise to some 33 °C (91 °F) on a hot day, and to fall naturally to around 29 °C (84 °F) by night.

[26] Generally lacking speed and agility, most turtles feed either on plant material or on animals with limited movements like mollusks, worms, and insect larvae.

[67] Some species have developed specialized diets such as the hawksbill, which eats sponges, the leatherback, which feeds on jellyfish, and the Mekong snail-eating turtle.

[70] The oblong turtle has a particularly large vocal range; producing sounds described as clacks, clicks, squawks, hoots, various kinds of chirps, wails, hooos, grunts, growls, blow bursts, howls, and drum rolls.

[75] Studies have shown that turtles can navigate the environment using landmarks and a map-like system resulting in accurate direct routes towards a goal.

Some non-marine turtles, such as the species of Geochelone (terrestrial), Chelydra (freshwater), and Malaclemys (estuarine), migrate seasonally over much shorter distances, up to around 27 km (17 mi), to lay eggs.

One possibility is imprinting as in salmon, where the young learn the chemical signature, effectively the scent, of their home waters before leaving, and remember that when the time comes for them to return as adults.

Proof that homing occurs is derived from genetic analysis of populations of loggerheads, hawksbills, leatherbacks, and olive ridleys by nesting place.

[13] There is experimental evidence that the embryos of Mauremys reevesii can move around inside their eggs to select the best temperature for development, thus influencing their sexual destiny.

[19][104] The theory accounted for the evolution of fossil pareiasaurs from Bradysaurus to Anthodon, but not for how the ribs could have become attached to the bony dermal plates.

[108] During the Late Cretaceous and Cenozoic, members of the pleurodire families Bothremydidae and Podocnemididae became widely distributed in the Northern Hemisphere due to their coastal habits.

[105] Some early morphological phylogenetic studies have placed turtles closer to Lepidosauria (tuataras, lizards, and snakes) than to Archosauria (crocodilians and birds).

[121] Ylenia Chiari and colleagues (2012) analyzed 248 nuclear genes from 16 vertebrates and suggested that turtles share a more recent common ancestor with birds and crocodilians.

[123] Squamata (lizards, snakes) Testudines Crocodilia (crocodiles, alligators) Aves (birds) Modern turtles and their extinct relatives with a complete shell are classified within the clade Testudinata.

Diversity has been stable, according to their analysis, except for a single rapid increase around the Eocene-Oligocene boundary some 30 million years ago, and a large regional extinction at roughly the same time.

In Pleurodira, the pelvis is sutured, joined with bony connections, to the carapace and to the plastron, creating a pair of large columns of bone at the back end of the turtle, linking the two parts of the shell.

[136] The world regions richest in non-marine turtle species are the Amazon basin, the Gulf of Mexico drainages of the United States, and parts of South and Southeast Asia.

[159][160] The Florida Fish and Wildlife Conservation Commission estimated in 2008 that around 3,000 pounds of softshell turtles were exported weekly via Tampa International Airport.

[162][163] Two tortoises were on the Soviet Union's September 1968 Zond 5 circumlunar flight, making them the first earthly living things to travel to the vicinity of the Moon.

[173] An ancient Greek origin myth told that only the tortoise refused the invitation of the gods Zeus and Hera to their wedding, as it preferred to stay at home.

[179][180][181] In 1896, the French playwright Léon Gandillot wrote a comedy in three acts named La Tortue that was "a Parisian sensation"[182] in its run in France, and came to the Manhattan Theatre, Broadway, New York, in 1898 as The Turtle.

[184] A giant fire-breathing turtle called Gamera is the star of a series of Japanese monster movies in the kaiju genre and has had twelve films from 1965 to 2006.

[190] Poor husbandry of tortoises can cause chronic rhinitis (nasal swelling), overgrown beaks, hyperparathyroidism (which softens their skeleton), constipation, various reproductive problems, and injuries from dogs.

Photograph of one half of a tortoise skeleton, cut in half vertically showing the vertebrae following curving along the carapace
Sagittal section of a tortoise skeleton
Drawing of a section through a turtle embryo showing formation of the shell, with the ribs growing sideways
Development of the shell. The ribs are growing sideways into the carapacial ridge, seen here as a bud, to support the carapace. [ 17 ]
Closeup of the head and neck of turtle
Head and neck of a European pond turtle
Marine turtle swimming
Sea turtles have streamlined shells and limbs adapted for fast and efficient swimming. [ 35 ]
head of a red-eared slider turtle
The red-eared slider has an exceptional seven types of color-detecting cells in its eyes. [ 38 ]
photo of a river turtle with only its nose above water
A submerged Indian softshell turtle nose-breathing at river surface
photo of a turtle climbing out of mud
Snapping turtle emerging from period of brumation , in which it buried itself in mud. Turtles have multiple circulatory and physiological adaptations to enable them to go long periods without breathing. [ 53 ]
cooter turtles basking in sunshine near their pond
Smaller pond turtles, like these northern red-bellied cooters , regulate their temperature by basking in the sun.
Photograph of a green sea turtle on the seabed, feeding
A green sea turtle grazing on seagrass
Photograph of an oblong turtle
The oblong turtle has a sizable vocal repertoire. [ 68 ]
Photo of a large bird eating a turtle
Crested caracara eating a turtle
An olive ridley sea turtle nesting on Escobilla Beach, Oaxaca , Mexico . Female sea turtles migrate long distances to nest on favored beaches.
Frames from a film showing one desert tortoise biting the other desert tortoise
Desert tortoises fighting
Photograph of a male turtle mounting a female
Mounting behavior in the three-toed box turtle
Land turtle laying an egg in a hole
A female common snapping turtle depositing her eggs in a hole she dug
Tortoise hatching from egg
Marginated tortoise emerges from its egg
Diagram of evolution of turtle shells showing four fossil species
Diagram of the origins of the turtle body plan through the Triassic : isolated bony plates evolved to form a complete shell , in a sequence involving Pappochelys , Eorhynchochelys , Odontochelys , and Proganochelys . [ 19 ]
Photograph of a marine turtle escaping from a specially-designed fishing net
Many turtles have been killed accidentally in fishing nets. [ 143 ] Some trawlers now use nets fitted with turtle excluders . [ 144 ] Seen here, a loggerhead escapes a net so fitted.