Cryptodira

Cryptodira Temporal range: Early Jurassic—Present, 190–0 Ma PreЄ Є O S D C P T J K Pg N
Aldabra giant tortoise (Aldabrachelys gigantea)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Testudines
Suborder:	Cryptodira Cope, 1868[1]
Subgroups
Eucryptodira †Paracryptodira
Synonyms[1][2]
Cryptoderes Duméril and Bibron, 1834 Cryptodera Lichtenstein, 1856 Cryptodira Cope, 1868 Cryptodiramorpha Lee, 1995 Pancryptodira Joyce, Parham, and Gauthier, 2004

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,^[3] 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.

As per the system used here, the Cryptodira can be classified as:^[4]

Manchurochelys liaoxiensis was a member of Sinemydidae.

Kinixys belliana from the Testudinidae

The Indian flapshell turtle (Lissemys punctata) from the Trionychidae is a highly advanced eucryptodire.

• †Hangaiemys
• †Paracryptodira
  • Family †Baenidae
  • Family †Pleurosternidae
• Eucryptodira
  • †Owadowia
  • Family †Plesiochelyidae
  • Clade Americhelydia
    • †Emarginachelys
    • Family Chelydridae (snapping turtles)
    • Superfamily Kinosternoidea
      • Family Dermatemydidae (river turtles)
      • Family Kinosternidae (mud turtles)
    • Clade Panchelonioidea
      • Family †Sandownidae
      • Family †Xinjiangchelyidae
      • Family †Sinemydidae
      • Family †Toxochelyidae
      • †Ctenochelys
      • Superfamily Chelonioidea (sea turtles)
        • Family †Protostegidae
        • Family †Thalassemydidae
        • Family Cheloniidae (green sea turtles and relatives)
        • Family Dermochelyidae (leatherback turtles)
  • Superfamily Testudinoidea
    • Family †Haichemydidae
    • Family †Lindholmemydidae
    • Family †Sinochelyidae
    • Family Platysternidae (big-headed turtle)
    • Family Emydidae (pond, box and water turtles)
    • Family Geoemydidae (Asian river turtles, Asian leaf turtles, Asian box turtles and roofed turtles)
    • Family Testudinidae (tortoises)
  • Clade Pantrionychia
    • Clade †Adocusia
      • Family †Adocidae
      • Family †Nanhsiungchelyidae
    • Superfamily Trionychia
      • Family Carettochelyidae (pignose turtles)
      • Family Trionychidae (softshell turtles)

References

Further reading

• Baur, George (1890): On the Classification of the Testudinata. Am. Nat. 24(282): 530-536. doi:10.1086/275138 First page image
• 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" (PDF). 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" (PDF). Chelonian Research Monographs. 5. Archived (PDF) from the original on 2012-04-23. 

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