| Cryptodira | |
|---|---|
 | |
| Physical description | |
| Binomial name | Chelonia mydas |
| Lifespan | Unknown |
| Conservational Status | |
| IUCN status | IUCN 3.1 |
| Scientific classification | |
| Kingdom | Animalia |
| Phylum | Chordata |
| Class | Reptilia |
| Order | Testudines |
| Suborder | Cryptodira |
| Distribution | |
| Distribution of species | Worldwide |
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.
Systematics and evolution[]
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 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.
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.
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 follows:
SUBORDER CRYPTODIRA
- Basal genera
- Genus †Kayentachelys (sometimes monotypic family Kayentachelyidae)
- Genus †Indochelys (sometimes monotypic family Indochelyidae)
paracryptodire.
- †Infraorder Paracryptodira
- Basal and incertae sedis
- Family Kallokibotiidae
- Family Mongolochelyidae
- Family Pleurosternidae
- Family Solemydidae
- Superfamily Baenoidea
- Family Baenidae
- Family Macrobaenidae
- Family Neurankylidae
- Basal and incertae sedis
Meiolania platyceps was a primitive Eucryptodira.
Kinixys belliana from the Testudinidae
The Indian Flap-shelled Turtle (Lissemys punctata) from the Trionychidae is a highly advanced eucryptodire
- Infraorder Eucryptodira
- Basal and incertae sedis
- Family †Eurysternidae
- Family †Plesiochelyidae
- Family †Xinjiangchelyidae
- Clade Centrocryptodira
- †"Sinemys" wuerhoensis
- Genus †Chubutemys (Meiolaniidae?)
- Family †Meiolaniidae
- Genus †Osteopygis
- Family †Macrobaenidae (paraphyletic? May belong in Paracryptodira)
- Family †Sinemydidae (paraphyletic?)
- Genus †Judithemys
- Genus Hangaiemys ("Macrobaenidae"?)
- Clade Polycryptodira
- Family Chelydridae (snapping turtles)
- Superfamily Chelonioidea (sea turtles)
- Family †Protostegidae
- Family †Thalassemyidae
- Family †Toxochelyidae
- Family Cheloniidae (green sea turtles and relatives)
- Family Dermochelyidae (leatherback turtles)
- Genus †Planetochelys
- 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)
- Superfamily Trionychoidea
- Family †Adocidae
- Family Carettochelyidae (pignose turtles)
- Family Dermatemydidae (river turtles)
- Family Kinosternidae (mud turtles)
- Family Trionychidae (softshell turtles)
- Basal and incertae sedis