Overview

Brief Summary

Austro-South American Side Necked Turtles

The Chelidae are one of three iving families of the Turtle (Testudines) suborder Pleurodira. There are some 60 odd species that are distributed in Australasia and South America. All members pull their heads back to the side as in other Pleurodiran Turtles. Well known members of this family include the Mata mata from South America and the Eastern Long-necked Turtle from Australia.

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage

Barcode of Life Data Systems (BOLD) Stats
                                        
Specimen Records:128Public Records:124
Specimens with Sequences:127Public Species:39
Specimens with Barcodes:120Public BINs:38
Species:40         
Species With Barcodes:37         
          
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Locations of barcode samples

Collection Sites: world map showing specimen collection locations for Chelidae

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Barcode data

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Wikipedia

Chelidae

The Chelidae are one of three living families of the turtle suborder Pleurodira and are commonly called the Austro-South American side-neck turtles.[2] The family is distributed in Australia, New Guinea, parts of Indonesia, and throughout most of South America. It is a large family of turtles with a significant fossil history dating back to the Cretaceous. The family is entirely Gondwanan in origin, with no members found outside of Gondwana, either in the present day or as a fossil.[3]

Description[edit]

Like all pleurodirous turtles, the chelids withdraw their necks sideways into their shells, differing from cryptodires that fold their necks in the vertical plane. They are all highly aquatic species with webbed feet and the capacity to stay submerged for long periods of time. The snake-necked species (genera Chelus, Chelodina, and Hydromedusa) are largely strike-and-gape hunters or foragers feeding on fish, invertebrates, and gastropods. The short-necked forms are largely herbivorous or molluscivorous, but are also opportunistic, with several species having specialized to eating fruits.

The highly aquatic nature of the group is typified by the presence of cloacal breathing in some species of the genera Elseya and Rheodytes.[4] However, some species, such as the eastern long-neck turtle (Chelodina longicollis) from Australia spend significant periods of time on land and are considered highly terrestrial.

The smaller members of the family include the Macleay river turtle (Emydura macquarii) at around 16 cm,[5] twist-necked turtle (Platemys platycephala) at 18 cm and the western swamp turtle (Pseudemydura umbrina) at 15 cm, whereas the larger species such as the mata mata (Chelus fimbriata) and the white-throated snapping turtle (Elseya albagula) both exceed 45 cm in shell length.[6]

Shell morphology[edit]

Members of Chelidae have unique shell morphology. The carapace often has reduced surface exposure of neural bones, or even none at all.[7] This is due to less requirement for enlarged longissimus dorsi muscles in side-necked turtles.[8]

The inside of the carapace is often heavily buttressed. This has sometimes been seen as a defense mechanism, that is it increases the strength of the shell against biting force, however Thomson (2003[8]) demonstrated it is linked to feeding methods and the prevention of internal torsion of the shell. Chelids also lack mesoplastra, which separates them from the Pelomedusidae.

The cervical scute is usually present, though it is absent in some species of Elseya and Myuchelys. Otherwise, the carapace has the usual complement of four costals, five vertebrals and 12 marginals (per side). Internally, the carapace is made of eight pleurals (per side), 11 peripherals (per side), a nuchal at the front and a suprapygal and pygal at the rear of the shell. As noted earlier, neurals, although always present, often exist as subsurface elements above the vertebral column.[7]

The plastron of chelids does not contain any hinges as can appear in some cryptodire turtles. The scute pattern is a unique feature of the Pleurodira and can be used to immediately identify a shell as belonging to this suborder. All cryptodires have 12 plastral scutes, whereas pleurodires have 13. The extra scute is called the intergular. The rest of the scutes and the skeletal structure beneath them are the same as all turtles: paired gulars, humerals, pectorals, abdominals, and anals. The skeletal elements consist of a single entoplaston, as well as paired epiplastra, entoplastra, hyoplastra, hypoplastra and xiphiplastra (Pritchard & Trebbau, 1984).[9]

Scute and Skeletal elements of the Chelid Carapace
Scute and Skeletal elements of the Chelid Carapace
Scute and Skeletal elements of the Chelid Plastron
Scute and Skeletal elements of the Chelid Plastron

Classification[edit]

A number of theories of the relationships within the large chelid family have been posited. Using shared derived characters, an early attempt in the 1970s used strict parsimony to determine that the three long-necked genera (Chelodina, Chelus and Hydromedusa) were each other's closest relatives.[10] This was accepted for some time, but brought into scrutiny,[11] because the major differences between the genera showed they all appeared to have evolved independently of each other, hinging on the fact that although they had long necks, how they used them and the structural differences were different.

A number of additional data sets were developed that used electrophoresis and nuclear and mtDNA analysis; these all agreed on the independent evolution of the three long-necked clades.[12][13] This was culminated in a reanalysis of the morphological data which demonstrated the convergence of the clades on a sweep of distinctive features needed for their piscivorous diets,[14] Thomson, 2000.[15] The subfamilies within Chelidae show the monophyly of the majority of the South American species and all the Australian species, with the far more ancient Hydromedusa as sister taxon to both these other groups.

The family Chelidae contains about 60 species within around 20 genera:[12]

Suborder Pleurodira

Phylogeny[edit]

Relationships of the living forms based on Georges et al., 2014.[29]

    Chelidae    
                      Hydromedusinae          

  Hydromedusa



  Chelinae    

  Chelus




  Phrynops





  Rhinemys



  Mesoclemmys





  Platemys



  Acanthochelys






  Chelodininae    

  Chelodina




  Pseudemydura





  Elusor



  Rheodytes





  Flaviemys




  Elseya




  Emydura



  Myuchelys










References[edit]

  1. ^ a b Gray, J. E. 1831. Synopsis Reptilium or short descriptions of the species of reptiles. Part 1. Cataphracta, tortoises, crocodiles, and enaliosaurians. London. 85 pp.
  2. ^ Obst, Fritz Jurgen (1998). Cogger, H.G. & Zweifel, R.G., ed. Encyclopedia of Reptiles and Amphibians. San Diego: Academic Press. pp. 111–112. ISBN 0-12-178560-2. 
  3. ^ Georges, A., & Thomson, S. 2006. Evolution and Zoogeography of Australian freshwater turtles. In: Merrick, J.R., Archer, M., Hickey, G., and Lee, M. (eds.), Evolution and Zoogeography of Australasian Vertebrates. Sydney: Australia.
  4. ^ Gordos, M.A., C.E. Franklin & C.J. Limpus (2004). Effect of water depth and water velocity upon the surfacing frequency of the bimodally respiring freshwater turtle, Rheodytes leukops. The Journal of Experimental Biology. 207:3099-3107.
  5. ^ Cann, J. (2008) Freshwater Turtles: A Wild Australia Guide, Qld, Australia: Steve Parish Publishing, p. 46.
  6. ^ Thomson, S., Georges, A. and C. Limpus, (2006). A New Species of Freshwater Turtle in the Genus Elseya (Testudines: Chelidae) from Central Coastal Queensland, Australia. Chelonian Conservation and Biology. 5(1):74-86.
  7. ^ a b Thomson, S. and Georges, A. 1996. Neural bones in chelid turtles. Chelonian Conservation and Biology 2:82-86.
  8. ^ a b Thomson S. 2003. Long necks, flat heads and the evolution of piscivory. World Chelonian Trust
  9. ^ Peter C. H. Pritchard and Pedro Trebbau 1984. Turtles of Venezuela. Society for the Studies of Amphibians and Reptiles: 403 pp.
  10. ^ Gaffney, E.S. 1977. The side-necked turtle family Chelidae: a theory of relationships using shared derived characters. American Museum Novitates 2620:1-28.
  11. ^ Pritchard, P.C.H. 1984. Piscivory in turtles, and evolution of the long-necked Chelidae. in Ferguson, M.W. (ed) The structure, development and evolution of reptiles. Zoological Society of London, Symposium. 52:87-110.
  12. ^ a b Georges, A.; J. Birrell, K. M. Saint, W. McCord und S. C. Donnellan (1998) A phylogeny for side-necked turtles (Chelonia: Pleurodira) based on mitochondrial and nuclear gene sequence variation Biological Journal of the Linnean Society 67: 213-246
  13. ^ Seddon, J., Georges, A., Baverstock, P. and McCord, W. 1997. Phylogenetic relationships of chelid turtles (Pleurodira: Chelidae) based on mitochondrial 12S rRNA gene sequence variation. Molecular Phylogenetics and Evolution. 7:55-61.
  14. ^ Thomson S. (2003). Long necks, flat heads and the evolution of piscivory. World Chelonian Trust
  15. ^ Thomson S.A. (2000). On the identification of the holotype of Chelodina oblonga (Testudinata: Chelidae) with a discussion of the taxonomic implications. Chelonian Conservation and Biology 3:745-749.
  16. ^ Baur, Georg. 1893. Notes on the classification of the Cryptodira. American Naturalist 27:672–674.
  17. ^ Megirian, D. and Murray, P. 1999. Chelid turtles (Pleurodira, Chelidae) from the Miocene Camfield Beds, Northern Territory of Australia, with a description of a new genus and species. The Beagle (Records of the Museums and Art Galleries of the Northern Territory) 15:75–130.
  18. ^ Gray, J.E. (1867) Description of a new Australian tortoise (Elseya latisternum). Ann. Mag. Nat. Hist. (3) 20: 43-45.
  19. ^ Cann, J. and Legler, J.M. (1994). The Mary River Tortoise: a new genus and species of short-necked chelid from Queensland, Australia (Testudines; Pleurodira). Chelonian Conservation and Biology 1(2):81-96.
  20. ^ Le, M., Reid, B., N., McCord, W., P., Naro-Maciel, E., Raxworthy, C., J., Amato, G., Georges A., 2013. Resolving the phylogenetic history of the short-necked turtles, genera Elseya and Myuchelys (Testudines: Chelidae) from Australia and New Guinea. Molecular Phylogenetics and Evolution. 68 (2013) 251–258.
  21. ^ Thomson, S. & Georges, A. (2009) Myuchelys gen. nov. — a new genus for Elseya latisternum and related forms of Australian freshwater turtle (Testudines: Pleurodira: Chelidae) Zootaxa 2053: 32–42.
  22. ^ Seibenrock, F. 1901. Beschreibung einer neuen schildkrotengattung aus der familie Chelydidae aus Australien: Pseudemydura. Anz. Akad. Wiss. Wien 38:248-251.
  23. ^ Legler, J.M. & Cann, J. 1980. A new species of chelid turtle from Queensland, Australia. Contributions to Science (Natural History Museum of Los Angeles County) 324:1-18.
  24. ^ Gray, John Edward. 1825. A synopsis of the genera of reptiles and amphibia, with a description of some new species. Annals of Philosophy (2)10:193–217.
  25. ^ Gray, J.E. 1873. Observations on chelonians, with descriptions of new genera and species. Annals and Magazine of Natural History (4)11:289-308.
  26. ^ a b c d Broin, F. de. and de la Fuente, M.S. 2001. Oldest world Chelidae (Chelonii, Pleurodira), from the Cretaceous Patagonia, Argentina. Palaeontology 333:463-470.
  27. ^ Wieland, G. R. 1923. A new Parana Pleurodiran. American Journal of Science. 5(25):1-15.
  28. ^ Baur, Georg. 1893. Notes on the classification and taxonomy of the Testudinata. Proceedings of the American Philosophical Society 31:210–225.
  29. ^ Georges, A., Zhang, X., Unmack, P., Reid, B., Le, M., and McCord, W. 2014. Contemporary genetic structure of an endemic freshwater turtle reflects Miocene orogenesis of New Guinea. Biological Journal of the Linnean Society, 2014, 111, 192–208.

External links and further reading[edit]

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