| Cryptodira Temporal range: Jurassic - recent |
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|---|---|
| Aldabra giant tortoise (Aldabrachelys gigantea) | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | Testudines |
| Suborder: | Cryptodira |
| Infraorders | |
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Paracryptodira |
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| Synonyms | |
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Cryptodiramorpha Lee, 1995 |
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Cryptodira is the taxonomic suborder of Testudines that includes most living tortoises and turtles. Cryptodira differ from Pleurodira (side-neck turtles) in that they lower their necks and pull the heads straight back into the shells; instead of folding their necks sideways along the body under the shells' margins. They include among their species freshwater turtles, snapping turtles, tortoises, soft shell turtles, and sea turtles.
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Cryptodires evolved primarily through the Jurassic period, and by the end of the Jurassic had almost completely replaced Pleurodires in the lakes and rivers, while beginning to develop land-based species.
Cryptodira has three living superfamilies, the Chelonioidea (sea turtles), Testudinoidea (tortoises and pond turtles) and Trionychoidea (softshell turtles and relatives). The Kinosternoidea are now recognized as a paraphyletic assemblage of mostly primitive Trionychoidea; they do not form a natural group.[1]
There are two commonly-found circumscriptions of the Cryptodira. One is used here; it includes a number of primitive extinct lineages known only from fossils, as well as the Eucryptodira. These are, in turn, made up from some very basal groups, and the Centrocryptodira contains the prehistoric relatives of the living cryptodires, as well as the latter, which are collectively called Polycryptodira.[1]
The alternate concept restricts the use of the term "Cryptodira" to the crown clade (i.e. Polycryptodira). The Cryptodira as understood here are called Cryptodiramorpha in this view. Under this approach, the pleurodires and cryptodires are not sister taxa.[1]
As per the system used here, the Cryptodira can be classified as follows:[1]
SUBORDER CRYPTODIRA
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