Palæos:		Unit 200: Anapsida
The Vertebrates		500: Cryptodira

Anapsida: Cryptodira

REPTILOMORPHA
|--SYNAPSIDA
`--+--EUREPTILIA 
   |   
   Anapsida
   |--Bolosauridae 
   `--Procolophonia
      |--Procolophonoidea 
      `--+--Hallucicrania 
         |  |--Lanthanosuchidae 
         |  `--Pareiasauria 
         `--Testudines
            |--Pleurodira
            `--Cryptodira
               |--Kayentachelys 
               `--Selmacryptodira
                  |--Meiolania  
                  `--Polycryptodira

1. Cryptodira
2. Kayentachelys X
3. Meiolania X 
4. Polycryptodira
5. Selmacryptodira

Descriptions

Cryptodira: snapping turtles, soft-shells, tortoises & sea turtles. 

Range: from the Early Jurassic

Phylogeny: Testudines:: Pleurodira + *: Kayentachelys + Selmacryptodira. 

Characters: Head (refer to BIODIDAC): pentagonal in dorsal view, with 2 large temporal emarginations dorsally; parietal covers the crown of the skull, which is markedly domed and tapers to a thin ridge between emarginations; this post parietal process overlies a long post supraoccipital process; occipital condyle below, and overhung by, supraoccipital process; ventrally, the skull has 2 large openings roughly below the emarginations, with a strong pterygoid bar passing between them; post margin of skull formed dorsally by squamosal + opisthotic & ventrally by quadrate + basisphenoid; small medial frontals ant to parietals; broad postorbitals form sides; prefrontal at apex pf rostrum; prefrontal and vomer in contact; (refer to BIODIDAC) upper jaw formed by maxilla w. small premaxilla at tip, both covered in life with keratinous beak; jugal and quadratojugal line up posterior to maxilla; $ jaw adductor tendon passes over process of otic capsule formed by prootic and quadrate; adductor may pass over parietal as well in some species.; $ vertical flange on external process of pterygoid; lower jaw (see BIODIDAC) formed largely by dentary and surangular; dentary has splenial and (post to splenial) a coronoid; retracted neck bent vertically; neck bend by way of specialized condyles – details vary among species. & may have evolved independently; no J forms have ability to retract neck; 2 relatively distinct sacral vertebrae; pelvic girdle sutured (not fused) to both plastron and carapace (see BIODIDAC and shellgirdle). Dominant crown group except in Aus; only Recent turtles in Northern hemisphere. 

Image: Geochelone carbonaria from Merkblätter.  

Links: Turtle, Tuatara, Crocodile Checklist--3; Halsbergers (Cryptodira); \Snapping Turtle Page\ - information and photo gallery page; WIEM: Zólwie skrytoszyjne (Polish); Higher Relationships of Testudines; Mongoleus; Order Testudines (Czech & English); Higher Reptile Taxa; Testudines; Cryptodira; Basal Cryptodira (Mikko's phylogeny); CRYPTODIRA (very nice summary of paleodiversity); APUS.RU | Подотряд Скрытошейные ·черепахи - Cryptodira; Halsbergerschildkröten (Cryptodira)- Kriechtiere (a remarkable set of links); Phylogeny of Turtles/Dr. E. S. Gaffney; tierdach.de- Halsberger-Schildkröten (German: possibly Best on the Web); Dr. Robert Wochesländer (abstracts); home2; Ocean Ambassadors -- Turtle Biology (sea turtles, natural history); Testudines Turtle Skull Reproductions; Jomonjin_KameDataBase.  ATW030531. 

Kayentachelys: Early Jurassic of North America. 

Phylogeny: Cryptodira: Selmacryptodira + *.  

Links: Kayentachelys.

Selmacryptodira: 

Range: from the Late Jurassic. 

Phylogeny: Cryptodira: Kayentachelys + *: Meiolania + Polycryptodira

Characters: $ posteromedial process of pterygoid preventing ventral exposure of prootic & forming floor of middle ear; loss of palatal teeth (independently of pleurodires).

Links: Testudines; Higher Relationships of Testudines.  ATW030512. 

Meiolania:  huge, "horned" turtles.

Range: Eocene to Pleistocene of Australia & South America.

Phylogeny: Selmacryptodira: Polycryptodira + *. 

Characters: "horned" head; tail spiked, with club.

Links: Meiolaniidae; Meiolania; PANGEA; qui (French); Fassaden (German).

References: Shaffer et al. (1997). 020214.

Note: The Pleistocene fossils from Lord Howe Island, Australia are particularly well-known.

Polycryptodira: at the moment, this is simply a placeholder for all living cryptodires, which is how the clade is defined.

checked ATW030512