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There are 14 extant [[family (biology)|families]] of the [[order (biology)|order]] [[Testudines]], an order of [[reptile]] commonly known as turtles, [[tortoise]]s and [[terrapin]]s. The testudines are some of the most ancient reptiles alive, with only the [[tuatara]]s considered more primitive. There are approximately 300 [[extant species]] and 97 [[genera]] of testudines, split into two [[suborders]]: the [[Cryptodira]]ns and the [[Pleurodira]]ns. The distinction between these two suborders is based on the mode in which they cover their head and neck. The Pleurodirans, also called the side-necked turtles, have long necks, and fold them sideways to align them with the shell. The [[Pelomedusidae]] and [[Chelidae]] are the only extant families of pleurodires. The Cryptodirans pull their neck straight back to conceal their head within the shell. The [[Carettochelyidae]], [[Cheloniidae]], [[Chelydridae]], [[Dermatemydidae]], [[Dermochelyidae]], [[Emydidae]], [[Kinosternidae]], [[Testudinidae]] and [[Trionychidae]] are all cryptodires, although the ability to retract the head has been lost in the sea turtles (Cheloniidae and Dermochelyidae). A third order, the [[Paracryptodira]]ns, are extinct.<ref name=eol>{{cite web |url=http://www.eol.org/pages/8120 |title=Testudines |last=Pecor |first=Keith |date=2 March 2010 |accessdate=26 June 2010 |publisher=[[Encyclopedia of Life]]}}</ref>
There are 14 extant [[family (biology)|families]] of the [[order (biology)|order]] [[Testudines]], an order of [[reptile]] commonly known as turtles, [[tortoise]]s and [[terrapin]]s. The testudines are some of the most ancient reptiles alive, with only the [[tuatara]]s considered more primitive. There are approximately 300 [[extant species]] and 97 [[genera]] of testudines, split into two [[suborders]]: the [[Cryptodira]]ns and the [[Pleurodira]]ns. The distinction between these two suborders is based on the mode in which they cover their head and neck. The Pleurodirans, also called the side-necked turtles, have long necks, and fold them sideways to align them with the shell. The [[Pelomedusidae]] and [[Chelidae]] are the only extant families of pleurodires. The Cryptodirans pull their neck straight back to conceal their head within the shell. The [[Carettochelyidae]], [[Cheloniidae]], [[Chelydridae]], [[Dermatemydidae]], [[Dermochelyidae]], [[Emydidae]], [[Kinosternidae]], [[Testudinidae]] and [[Trionychidae]] are all cryptodires, although the ability to retract the head has been lost in the sea turtles (Cheloniidae and Dermochelyidae). A third order, the [[Paracryptodira]]ns, are extinct.<ref name=eol>{{cite web |url=http://www.eol.org/pages/8120 |title=Testudines |last=Pecor |first=Keith |date=2 March 2010 |accessdate=26 June 2010 |publisher=[[Encyclopedia of Life]]}}</ref>


Reptiles are classified according to the pattern of [[wikt:fenestration|fenestration]] in the temporal region of the [[skull]]. Testudines are placed in the subclass [[Anapsida]] because they lack fenestration.<ref>[[Alfred Romer|Romer, A.S.]] (1933). ''Vertebrate Paleontology''. University of Chicago Press. , 3rd ed., 1966.</ref> There are suggestions that this lack of fenestration is a secondary characteristic and that turtles belong in [[Diapsida]]. The shell of testudines distinguishes them from other vertebrates. The shell is not an [[exoskeleton]], but a modified [[ribcage]] and part of the [[vertebral column]]. Because of the shell, the pectoral and pelvic girdles are located within the ribcage. The limb bones are also modified to accommodate to the shell.<ref name=eol />
Reptiles are classified according to the pattern of [[wikt:fenestration|fenestration]] in the temporal region of the [[skull]]. Testudines are placed in the subclass [[Anapsida]] because they lack fenestration.<ref>[[Alfred Romer|Romer, A.S.]] (1933). ''Vertebrate Paleontology''. University of Chicago Press. , 3rd ed., 1966.</ref> There are suggestions that this lack of fenestration is a secondary characteristic and that turtles belong in [[Diapsida]].<ref name="Laurin 1995 165–223"/>
Both sides cite strong evidence, and the conflict has yet to be resolved.<ref>{{cite book|last=Benton|first=M. J.|coauthors=|authorlink=|title=[[Vertebrate Paleontology (Benton)|Vertebrate Paleontology]]|edition=2nd|publisher=Blackwell Science Ltd|location=London|year=2000|isbn=0632056142|series=}}, 3rd ed. 2004 ISBN 0-632-05637-1</ref><ref>{{cite journal|last=Zardoya|first=R.|coauthors=Meyer, A.|year=1998|title=Complete mitochondrial genome suggests diapsid affinities of turtles|url=http://www.pubmedcentral.gov/articlerender.fcgi?artid=24355|journal=[[Proceedings of the National Academy of Sciences|Proc Natl Acad Sci U S A]]|issn=0027-8424|volume=95|issue=24|pages=14226–14231|doi=10.1073/pnas.95.24.14226|pmid=9826682|pmc=24355}}</ref><ref>{{cite journal|last=Rieppel|first=O.|coauthors=deBraga, M.|year=1996|title=Turtles as diapsid reptiles|url=|journal=[[Nature (journal)|Nature]]|issn=|volume=384|issue=|pages=453–455|doi=10.1038/384453a0}}</ref> The shell of testudines distinguishes them from other vertebrates. The shell is not an [[exoskeleton]], but a modified [[ribcage]] and part of the [[vertebral column]]. Because of the shell, the pectoral and pelvic girdles are located within the ribcage. The limb bones are also modified to accommodate to the shell.<ref name=eol />


The earliest known turtles are from fossils in the [[Upper Triassic]]. These fossils are nearly indistinguishable from modern turtles anatomically. In these early fossils (mostly of the genus [[Proganochelys]]), the teeth have already been lost, and a [[keratin]] beak is suggested by the [[mandibles]]. Important differences between Proganochelys and modern turtles are the presence of the palatal teeth (lost in modern species), the inability to retract the head within the shell, and the lack of a trochlear pulley in the jaw closing anatomy.<ref name=eol />
The earliest known turtles are from fossils in the [[Upper Triassic]]. These fossils are nearly indistinguishable from modern turtles anatomically. In these early fossils (mostly of the genus [[Proganochelys]]), the teeth have already been lost, and a [[keratin]] beak is suggested by the [[mandibles]]. Important differences between Proganochelys and modern turtles are the presence of the palatal teeth (lost in modern species), the inability to retract the head within the shell, and the lack of a trochlear pulley in the jaw closing anatomy.<ref name=eol />

Revision as of 17:13, 24 August 2010

Turtles
Temporal range: Triassic–Recent
Scientific classification
Kingdom:
Phylum:
Class:
Order:
Linnaeus, 1758

There are 14 extant families of the order Testudines, an order of reptile commonly known as turtles, tortoises and terrapins. The testudines are some of the most ancient reptiles alive, with only the tuataras considered more primitive. There are approximately 300 extant species and 97 genera of testudines, split into two suborders: the Cryptodirans and the Pleurodirans. The distinction between these two suborders is based on the mode in which they cover their head and neck. The Pleurodirans, also called the side-necked turtles, have long necks, and fold them sideways to align them with the shell. The Pelomedusidae and Chelidae are the only extant families of pleurodires. The Cryptodirans pull their neck straight back to conceal their head within the shell. The Carettochelyidae, Cheloniidae, Chelydridae, Dermatemydidae, Dermochelyidae, Emydidae, Kinosternidae, Testudinidae and Trionychidae are all cryptodires, although the ability to retract the head has been lost in the sea turtles (Cheloniidae and Dermochelyidae). A third order, the Paracryptodirans, are extinct.[1]

Reptiles are classified according to the pattern of fenestration in the temporal region of the skull. Testudines are placed in the subclass Anapsida because they lack fenestration.[2] There are suggestions that this lack of fenestration is a secondary characteristic and that turtles belong in Diapsida.[3] Both sides cite strong evidence, and the conflict has yet to be resolved.[4][5][6] The shell of testudines distinguishes them from other vertebrates. The shell is not an exoskeleton, but a modified ribcage and part of the vertebral column. Because of the shell, the pectoral and pelvic girdles are located within the ribcage. The limb bones are also modified to accommodate to the shell.[1]

The earliest known turtles are from fossils in the Upper Triassic. These fossils are nearly indistinguishable from modern turtles anatomically. In these early fossils (mostly of the genus Proganochelys), the teeth have already been lost, and a keratin beak is suggested by the mandibles. Important differences between Proganochelys and modern turtles are the presence of the palatal teeth (lost in modern species), the inability to retract the head within the shell, and the lack of a trochlear pulley in the jaw closing anatomy.[1]

Families

The following lists the family—the Latin name of the family, date in which the species was formally described and classified, and the binomial authority on the species; the number of genera belonging to the family; the name or names commonly used; an example species and an example image.


colspan="5" align="center" Template:Bgcolor-blue|Cryptodira – 11 families, 74 genera, over 200 species
Family[7] Genera[8] Common name(s) Example species Example image
Carettochelyidae
Boulenger, 1887
1 Pig-nosed Turtle Pig-nosed Turtle (Carettochelys insculpta)
Cheloniidae
Oppel, 1811
5 Sea turtles Green Sea Turtle (Chelonia mydas)
Chelydridae
Gray, 1831
2 Snapping turtles Alligator Snapping Turtle (Macrochelys temminckii)
Dermatemydidae
Gray, 1870
1 Mesoamerican River Turtle Mesoamerican River Turtle (Dermatemys mawii)
Dermochelyidae
Fitzinger, 1843
1 Leatherback Sea Turtle Leatherback Sea Turtle (Dermochelys coriacea)
Emydidae
Rafinesque, 1815
12 Box or water turtles Red-eared Slider (Trachemys scripta elegans)
Geoemydidae
Theobald, 1868
24 Asian river, leaf, roofed or Asian box turtles Malayan Box Turtle (Cuora amboinensis) Cuora amboinensis kamaroma j.jpg
Kinosternidae
Agassiz, 1857
4 Mud or musk turtles Common Musk Turtle (Sternotherus odoratus)
Platysternidae
Gray, 1869
1 Big-headed Turtle Big-headed Turtle (Platysternon megacephalum)
Testudinidae
Batsch, 1788
12 Tortoises Aldabra Giant Tortoise (Geochelone gigantea)
Trionychidae
Fitzinger, 1826
14 Softshell turtles Spiny Softshell Turtle (Apalone spinifera)
colspan="5" align="center" Template:Bgcolor-blue|Pleurodira – 3 families, 16 genera, over 60 species
Family Genera Common names Example species Example photo
Chelidae
Gray, 1831
15 Austro-American sideneck turtles Common Snakeneck Turtle (Chelodina longicollis)
Pelomedusidae
Cope, 1868
2 Afro-American sideneck turtles African Helmeted Turtle (Pelomedusa subrufa)
Podocnemididae
Gray, 1869
3 Madagascan Big-headed, Big-headed Amazon River Turtle and South American sideneck river turtles Madagascan Big-headed Turtle (Erymnochelys madagascariensis)


References

  1. ^ a b c Pecor, Keith (2 March 2010). "Testudines". Encyclopedia of Life. Retrieved 26 June 2010.
  2. ^ Romer, A.S. (1933). Vertebrate Paleontology. University of Chicago Press. , 3rd ed., 1966.
  3. ^ Cite error: The named reference Laurin 1995 165–223 was invoked but never defined (see the help page).
  4. ^ Benton, M. J. (2000). Vertebrate Paleontology (2nd ed.). London: Blackwell Science Ltd. ISBN 0632056142. {{cite book}}: Cite has empty unknown parameter: |coauthors= (help), 3rd ed. 2004 ISBN 0-632-05637-1
  5. ^ Zardoya, R. (1998). "Complete mitochondrial genome suggests diapsid affinities of turtles". Proc Natl Acad Sci U S A. 95 (24): 14226–14231. doi:10.1073/pnas.95.24.14226. ISSN 0027-8424. PMC 24355. PMID 9826682. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  6. ^ Rieppel, O. (1996). "Turtles as diapsid reptiles". Nature. 384: 453–455. doi:10.1038/384453a0. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  7. ^ John B. Iverson, A. Jon Kimerling, A. Ross Kiester. "List of All Families". Terra Cognita Laboratory, Geosciences Department of Oregon State University. Retrieved 26 June 2010.{{cite web}}: CS1 maint: multiple names: authors list (link)
  8. ^ John B. Iverson, A. Jon Kimerling, A. Ross Kiester. "List of Genera". Terra Cognita Laboratory, Geosciences Department of Oregon State University. Retrieved 26 June 2010.{{cite web}}: CS1 maint: multiple names: authors list (link)

Further reading

  • David T. Kirkpatrick (November/December 1995). "Platysternon megacephalum". Reptile & Amphibian Magazine. pp. 40–47. Retrieved 26 June 2010. {{cite web}}: Check date values in: |date= (help)
  • Cogger, H.G. (2004). Encyclopedia of Reptiles & Amphibians Second Edition. Fog City Press. ISBN 1-877019-69-0. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  • John B. Iverson, A. Jon Kimerling, A. Ross Kiester. "EMYSystems". Terra Cognita Laboratory, Geosciences Department of Oregon State University. Retrieved 26 June 2010.{{cite web}}: CS1 maint: multiple names: authors list (link)