Cryptodira

Cryptodira Temporal range: Early Jurassic—Present, 190–0 Ma PreЄ Є O S D C P T J K Pg N
File:Tortoise.aldabra.750pix.jpg
Aldabra giant tortoise (Aldabrachelys gigantea)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Testudines
Suborder:	Cryptodira Cope, 1868
Subgroups
Eucryptodira †Paracryptodira
Synonyms
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.

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:

File:Manchuroche.JPG

Manchurochelys liaoxiensis was a paracryptodire.

Meiolania platyceps was a primitive eucryptodire.

File:Kinixys belliana nogueyi 1 by diotime.jpg

Kinixys belliana from the Testudinidae

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

• †Dracochelys
• †Emarginachelys
• †Hangaiemys
• †Judithemys
• †Mongolemys
• †Sinemys
• †Ordosemys
• †Paracryptodira
  • †Dorsetochelys
  • Family Baenidae
  • Family Pleurosternidae
• Family †"Plesiochelyidae"
• Family †Xinjiangchelyidae
• Clade Panchelonioidea
  • Superfamily Chelonioidea (sea turtles)
    • Family †Protostegidae
    • Family †Thalassemydidae
    • Family †Toxochelyidae
    • 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 Panchelydridae
  • Family Chelydridae (snapping turtles)
• Superfamily Kinosternoidea
  • Family Dermatemydidae (river turtles)
  • Family Kinosternidae (mud turtles)
• Clade Pantrionychia
  • Genus †Adocus
  • Superfamily Trionychia
    • Family Carettochelyidae (pignose turtles)
    • Family Trionychidae (softshell turtles)

Further reading

• 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.