Temporal range: Early Jurassic—Present, 190–0 Ma 
|Aldabra giant tortoise (Aldabrachelys gigantea)|
|Order:||Testudines salchi turtles|
Cryptoderes Duméril and Bibron, 1834
Cryptodira is a 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.
Systematics and evolution
Cryptodires evolved during 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. Meanwhile, pleurodires became the dominant freshwater testudines in the Cretaceous to Eocene of Europe, and produced a family of marine species, the Bothremydidae.
The Cryptodira suborder has three living superfamilies, the Chelonioidea (sea turtles), Testudinoidea (tortoises and pond turtles), and Trionychoidea (soft-shell turtles and relatives). The families within the Kinosternoidea are now recognized as a paraphyletic assemblage of mostly primitive Trionychoidea; they do not form a natural group.
Two circumscriptions of the Cryptodira are commonly found. 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 contain the prehistoric relatives of the living cryptodires, as well as the latter, which are collectively called Polycryptodira.
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.
As per the system used here, the Cryptodira can be classified as:
- Family †"Plesiochelyidae"
- Family †Xinjiangchelyidae
- Clade Panchelonioidea
- Superfamily Testudinoidea
- Clade Panchelydridae
- Family Chelydridae (snapping turtles)
- Superfamily Kinosternoidea
- Clade Pantrionychia
- Rhodin 2011, p. 000.171
- Rhodin 2008, p. 000.3
- Adán Pérez-García, A new turtle confirms the presence of Bothremydidae (Pleurodira) in the Cenozoic of Europe and expands the biostratigraphic range of Foxemydina, The Science of Nature August 2016, 103:50 First online: 04 June 2016
- See references in Haaramo (2008)
- Anquetin, J. R. M. (2012). "Reassessment of the phylogenetic interrelationships of basal turtles (Testudinata)". Journal of Systematic Palaeontology. 10: 3. doi:10.1080/14772019.2011.558928.
- Baur, George (1890): On the Classification of the Testudinata. Am. Nat. 24(282): 530-536. doi:10.1086/275138 First page image
- Haaramo, Mikko (2008): Mikko's Phylogeny Archive – Cryptodira. Version of 2008-MAR-11. Retrieved 2008-MAY-07.
- Rhodin, Anders G.J.; van Dijk, Peter Paul; Inverson, John B.; Shaffer, H. Bradley; Roger, Bour (2011-12-31). "Turtles of the world, 2011 update: Annotated checklist of taxonomy, synonymy, distribution and conservation status". Chelonian Research Monographs. 5. Archived from the original (PDF) on 2012-01-22.
- Rhodin, Anders G.J.; van Dijk, Peter Paul; Parham, James F. (2008-12-08). "Turtles of the world, 2008 checklist". Chelonian Research Monographs. 5. Archived from the original (PDF) on 2011-09-05.
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