Cryptodira

Carapace of Pleurosternon bullocki, from Milner (2004).

Belongs within: Testudinata.
Contains: Centrocryptodira.

The Cryptodira are the larger of the two major clades of living testudinates. Living cryptodires are characterised by the ability to draw the head directly backwards within the shell, but this feature is not yet present in stem members of the clade. Kayentachelys aprix is one such stem cryptodire, known from the Early Jurassic of Arizona.

Synapomorphies (from Gaffney & Meylan 1988): Main adductor tendon with cartilaginous nodule articulating on trochlear surface; processus pterygoideus externus with flat vertical plane oriented at right angles to plane of pterygoid; ventral process of prefrontal contacting vomer.

<==Cryptodira
    |--Kayentachelys [Kayentachelydia, Kayentachelyidae] GM88
    |    `--K. aprix GM88
    `--Selmacryptodira [Baenoidea] GM88
         |--Pleurosternidae GM88
         |    |--Glyptops [Glyptopsidae] GM88
         |    `--Pleurosternon [incl. Mesochelys] GM88
         |         `--P. bullocki N85
         `--Daiocryptodira GM88
              |--Eucryptodira GM88
              |    |--Centrocryptodira GM88
              |    `--Plesiochelyidae GM88
              |         |  i. s.: Parachelys GM88
              |         |         Eurysternum GM88
              |         |--Portlandemys GM88
              |         `--+--Plesiochelys GM88
              |            `--Thalassemys [Thalassemydidae] GM88
              |                 `--T. moseri GM88
              `--Baenidae GM88
                   |--Trinitichelys GM88
                   `--Baeninae GM88
                        |  i. s.: Neurankylus GM88
                        |--Hayemys GM88
                        `--Baenodd GM88
                             |--Plesiobaena GM88
                             `--Baenini GM88
                                  |--Baenina GM88
                                  |    |--Chisternon GM88
                                  |    `--Baena arenosa GM88, C77
                                  `--Eubaenina GM88
                                       |--Eubaena cephalica GM88
                                       `--+--Palatobaena GM88
                                          `--Stygiochelys Gaffney & Hiatt 1971 GM88, D07
                                               `--S. estesi D07

*Type species of generic name indicated

REFERENCES

[C77] Cope, E. D. 1877. Report upon the extinct Vertebrata obtained in New Mexico by parties of the expedition of 1874. Geographical Surveys West of the One Hundredth Meridian 4 (2): i–iv, 1–370.

[D07] Dixon, D. 2007. The Complete Illustrated Encyclopedia of Dinosaurs & Prehistoric Creatures. Hermes House: London.

[GM88] Gaffney, E. S., & P. A. Meylan. 1988. A phylogeny of turtles. In: Benton, M. J. (ed.) The Phylogeny and Classification of the Tetrapods vol. 1. Amphibians, Reptiles, Birds pp. 157–219. Clarendon Press: Oxford.

[N85] Norman, D. 1985 (reprinted 2000). The Illustrated Encyclopedia of Dinosaurs. Salamander Books: London.

Last updated: 11 August 2017.