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Turtles Fossil range: 210–0 Ma PreЄ Є O S D C P T J K Pg N Late Triassic - Recent
"Chelonia" from Ernst Haeckel's Kunstformen der Natur, 1904
Scientific classification
Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Superclass: Tetrapoda Class: Reptilia Subclass: Anapsida Superorder: Chelonia Macartney, 1802 Order: Testudines Linnaeus, 1758
Diversity
14 extant families with ca. 300 species
blue: sea turtles, black: land turtles
Suborders
Cryptodira Pleurodira See text for families.

Turtles, Tortoises, and Terrapins are ectothermic reptiles, most of whose body is shielded by a special bony or cartilagenous shell developed from their ribs. They belong to an anapsid lineage, as can be seen from their solid skullcap. About 300 species are alive today; some are highly endangered.

The order to which the turtles belong is usually called Testudines. Sometimes Chelonia is given as a junior synonym, but this is strictly speaking incorrect. For most purposes, the differences are minor however: The Chelonia are simply the Testudines plus the "proto-turtle" Australochelys africanus, a turtlelike anapsid from the Jurassic which lacked some of the Testudines' apomorphies. The oldest fossils of the Testudines actually predate Australochelys. They are the basal turtle genus Proganochelys^[1] which lived in Late Triassic Eurasia about 210 million years ago, making turtles one of the oldest reptile groups, and a much more ancient group than lizards and snakes.

Contents 1 Characteristics 2 Systematics 2.1 Basal chelonians 2.2 Suborder Cryptodira 2.3 Suborder Pleurodira 3 Footnotes 4 References

Characteristics

The defining feature of the testudines is the presence of a bony shell comprising an upper carapace and a lower plastron, both composed of solid bony plates. In most families, this bony shell is further covered by a layer of thick horny scales, which form the visible part of the shell, but some have a softer, leathery, covering^[2].

Living testudines lack teeth, having a horny beak, which is sharpened or serrated to cut flesh or plant matter. Testudines also have strong limbs to lift their heavy bodies. The shape of the limb is variable, however, with land dwelling species typically fusing the toes into a solid clump, freshwater species having distinct, but webbed, toes, and marine species having powerful flippers^[2].

Testudines lay eggs in a nest chamber, but no species displays parental care. Instead, the young are left to fend for themselves from the moment they hatch. Incubation time varies greatly between species, but two to three months is typical^[2].

Systematics

Main article: List of Testudines families

There are about 300 living species of testudine, grouped into two suborders and fourteen families^[3].

Basal chelonians

• Genus Australochelys (basal Chelonia)
• Genus Proganochelys (basal Testudines)

Suborder Cryptodira

Basal genera

• Genus Kayentachelys
• Genus Indochelys

Infraorder †Paracryptodira

• Basal and incertae sedis
  • Family †Kallokibotiidae
  • Family †Mongolochelyidae
  • Family †Pleurosternidae
  • Family †Solemydidae
• Superfamily †Baenoidea
  • Family †Baenidae
  • Family †Macrobaenidae
  • Family †Neurankylidae

Infraorder Eucryptodira

• †"Sinemys" wuerhoensis
• Genus †Chubutemys (Meiolaniidae?)
• Genus †Hangaiemys (Macrobaenidae?)
• Genus †Judithemys
• Genus †Osteopygis
• Genus †Planetochelys
• Family Chelydridae (snapping turtles)
• Family †Eurysternidae
• Family †Macrobaenidae
• Family †Meiolaniidae (horned turtles)
• Family †Plesiochelyidae
• Family †Sinemydidae
• Family †Xinjiangchelyidae
• Superfamily Chelonioidea (sea turtles)
  • Family †Protostegidae
  • Family †Thalassemyidae
  • 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)
• Superfamily Trionychoidea
  • Family †Adocidae
  • Family Carettochelyidae (pignose turtles)
  • Family Dermatemydidae (river turtles)
  • Family Kinosternidae (mud turtles)
  • Family Trionychidae (softshell turtles)

Suborder Pleurodira

Basal and incertae sedis

• Family †Araripemydidae
• Family †Proterochersidae
• Family Chelidae (Austro-American sideneck turtles)

Superfamily Pelomedusoidea

• Family †Bothremydidae
• Family Pelomedusidae (African sideneck turtles)
• Family Podocnemididae (Madagascan big-headed and American sideneck river turtles)

Footnotes

References

• Haaramo, Mikko (2008): Mikko's Phylogeny Archive - Hallucicrania. Version of 2008-MAR-11. Retrieved 2008-MAY-07.

v • d • e Extant sauropsida orders by subclass Kingdom: Animalia · Phylum: Chordata · Subphylum: Vertebrata Anapsida Chelonia Testudines Diapsida Lepidosauromorpha Sphenodontia · Squamata Archosauromorpha Crocodilia

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• This page was last modified on 8 October 2008, at 15:53.

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