Turtle

For other uses, see Turtle (disambiguation).
Families
Testudines, Chelonia

Turtles are reptiles of the order Testudines (all living turtles belong to the crown group Chelonia), most of whose body is shielded by a special bony or cartilagenous shell developed from their ribs. The term turtle is usually used for the aquatic species, though aquatic fresh water turtles are also called terrapins. The term is sometimes used (esp. in North America) to refer to all members of the order, including tortoises, which are predominantly land-based. The order of Testudines includes both extant (living) and extinct species. About 300 species are alive today. Some species of turtles are highly endangered.

Description

All turtles have a protective shell around their bodies. The top part of the shell is called the carapace, the bottom is called the plastron, and the two are connected by a bridge. Some are known to be able to breathe through their rectums as well. Reference the Rheodytes leukops species.

Sea turtles grow to large sizes and live in the oceans in the temperate and tropical regions of Earth. Pond turtles (terrapins) are usually much smaller, while some land terrapins (tortoises) are as large as sea turtles. The sizes of turtles vary from a few centimetres (forest and jungle species) to two metres (the leatherback turtle and the Galapagos tortoise).

Turtles generally live a long time; some individuals are known to have lived longer than 150 years. The oldest tortoise on record is Tui Malila, known to have lived at least 188 years.

Sea turtles lay their eggs on dry sandy beaches. The eggs of the largest species are spherical, while the eggs of the rest are elongated. Their albumen is white and will not coagulate when cooked because of the protein it contains which is different to that of bird eggs. Turtle eggs prepared to eat consist mainly of yolk. In some species, temperature of the egg during development determines whether an egg develops into a male or a female: a higher temperature causes a female, a lower temperature causes a male.

Although they spend large proportions of their lives underwater, turtles are air-breathing reptiles, and must surface at regular intervals to refill their lungs with fresh air. However, aquatic respiration in Australian freshwater turtles is currently being studied. Some species have large cloacal cavities lined with many finger-like projections. These projections, called "papillae", have a rich blood supply, and increase the surface area of the cloaca. The turtles can take up dissolved oxygen from the water through these papillae, in much the same way that fish use gills.

Turtles have a gelatinous substance in their upper and lower shell, called calipash and calipee respectively, the calipash being of a dull greenish and the calipee of a light yellow color.

Evolution

The first turtles are believed to have existed in the era of the dinosaurs, 200 million years ago. Their exact ancestry is disputed. It was believed that they are the only surviving branch of the ancient clade Anapsida, which includes groups such as procolophonoids, millerettids, protorothyrids and pareiasaurs. All Anapsid skulls lack a temporal opening, while all other extant amniotes have temporal openings (although in mammals the hole has become the zygoid arch). Most anapsids became extinct in the late Permian period, except procolophonoids and possibly the precursors of the testudines (turtles).

However, it was recently suggested that the Anapsid-like turtle skull may be due to convergent evolution rather than to anapsid descent. More recent phylogenetic studies with this in mind placed turtles firmly within diapsids, slightly closer to Squamata than to Archosauria. All molecular studies have strongly upheld this new phylogeny, though some place turtles closer to Archosauria. Re-analysis of prior phylogenies suggests that they classified turtles as anapsids both because they assumed this classification (most of them studying what sort of anapsid turtles are) and because they did not sample fossil and extant taxa were broadly enough for constructing the cladogram. While the issue is far from resolved, most scientists now lean towards a Diapsid origin for turtles.

Order Testudines - Turtles

Gulf Coast Box Turtle, Terrapene carolina major (Emydidae) A slider of genus Trachemys A Leatherback Sea Turtle. Photo credit: NOAA

Suborder Paracryptodira (extinct)

Suborder Cryptodira

Suborder Pleurodira


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Suborder Pleurodira.
. Suborder Cryptodira.
. Suborder Paracryptodira (extinct)
.
. While the issue is far from resolved, most scientists now lean towards a Diapsid origin for turtles.
.

Re-analysis of prior phylogenies suggests that they classified turtles as anapsids both because they assumed this classification (most of them studying what sort of anapsid turtles are) and because they did not sample fossil and extant taxa were broadly enough for constructing the cladogram.
. All molecular studies have strongly upheld this new phylogeny, though some place turtles closer to Archosauria. Volkswagen Bus may be a reference to:. More recent phylogenetic studies with this in mind placed turtles firmly within diapsids, slightly closer to Squamata than to Archosauria. Volkswagen Eurovan, generation T5. However, it was recently suggested that the Anapsid-like turtle skull may be due to convergent evolution rather than to anapsid descent. Volkswagen Eurovan, generation T4.

Most anapsids became extinct in the late Permian period, except procolophonoids and possibly the precursors of the testudines (turtles). Volkswagen Type 2, generation T3/Vanagon/T25. All Anapsid skulls lack a temporal opening, while all other extant amniotes have temporal openings (although in mammals the hole has become the zygoid arch). Volkswagen Type 2, generation T2. It was believed that they are the only surviving branch of the ancient clade Anapsida, which includes groups such as procolophonoids, millerettids, protorothyrids and pareiasaurs. Volkswagen Type 2, generation T1. Their exact ancestry is disputed.

The first turtles are believed to have existed in the era of the dinosaurs, 200 million years ago. Turtles have a gelatinous substance in their upper and lower shell, called calipash and calipee respectively, the calipash being of a dull greenish and the calipee of a light yellow color. The turtles can take up dissolved oxygen from the water through these papillae, in much the same way that fish use gills. These projections, called "papillae", have a rich blood supply, and increase the surface area of the cloaca.

Some species have large cloacal cavities lined with many finger-like projections. However, aquatic respiration in Australian freshwater turtles is currently being studied. Although they spend large proportions of their lives underwater, turtles are air-breathing reptiles, and must surface at regular intervals to refill their lungs with fresh air. In some species, temperature of the egg during development determines whether an egg develops into a male or a female: a higher temperature causes a female, a lower temperature causes a male.

Turtle eggs prepared to eat consist mainly of yolk. Their albumen is white and will not coagulate when cooked because of the protein it contains which is different to that of bird eggs. The eggs of the largest species are spherical, while the eggs of the rest are elongated. Sea turtles lay their eggs on dry sandy beaches.

The oldest tortoise on record is Tui Malila, known to have lived at least 188 years. Turtles generally live a long time; some individuals are known to have lived longer than 150 years. The sizes of turtles vary from a few centimetres (forest and jungle species) to two metres (the leatherback turtle and the Galapagos tortoise). Pond turtles (terrapins) are usually much smaller, while some land terrapins (tortoises) are as large as sea turtles.

Sea turtles grow to large sizes and live in the oceans in the temperate and tropical regions of Earth. Reference the Rheodytes leukops species. Some are known to be able to breathe through their rectums as well. The top part of the shell is called the carapace, the bottom is called the plastron, and the two are connected by a bridge.

All turtles have a protective shell around their bodies. . Some species of turtles are highly endangered. About 300 species are alive today.

The order of Testudines includes both extant (living) and extinct species. in North America) to refer to all members of the order, including tortoises, which are predominantly land-based. The term is sometimes used (esp. The term turtle is usually used for the aquatic species, though aquatic fresh water turtles are also called terrapins.

Turtles are reptiles of the order Testudines (all living turtles belong to the crown group Chelonia), most of whose body is shielded by a special bony or cartilagenous shell developed from their ribs. Superfamily Pelomedusoidea. Superfamily Chelonioidea. Superfamily Kinosternoidea.

Superfamily Trionychoidea. Superfamily Testudinoidea.

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