Chelidae

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Chelidae
Temporal range: Albian-Present
Chelus fimbriatus 2005.jpg
Chelus fimbriatus
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Testudines
Suborder: Pleurodira
Family: Chelidae
Gray, 1831 [1]
Genera

See text

Chelidae is one of three living families of the turtle suborder Pleurodira, and are commonly called 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 Gondwana, either in the present day or as a fossil. [3]

Contents

Description

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]

Chelids exhibit XX/XY genetic sex determination, in contrast to most other turtles, which have temperature-dependent sex determination. [7]

Shell morphology

Members of Chelidae have unique shell morphology. The carapace often has reduced surface exposure of neural bones, or even none at all. [8] This is due to less requirement for enlarged longissimus dorsi muscles in side-necked turtles. [9]

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) [9] 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.

Scute and skeletal elements of the chelid carapace Pu carapace.jpg
Scute and skeletal elements of the chelid carapace

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 twelve marginals (per side). Internally, the carapace is made of eight pleurals (per side), eleven 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. [8]

Scute and skeletal elements of the chelid plastron Pu plastron.jpg
Scute and skeletal elements of the chelid plastron

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 thirteen. 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 entoplastron, as well as paired epiplastra, entoplastra, hyoplastra, hypoplastra and xiphiplastra (Pritchard & Trebbau, 1984). [10]

Evolutionary history

The oldest records of Pan-Chelidae (the clade containing Chelidae and all other species more closely related to Chelidae than other pleurodires) first appear in the mid Cretaceous in South America and Australia, represented by Prochelidella cerrobarcinae from the Cerro Barcino Formation of Argentina, which dates from 118 to 110 million years ago, [11] [12] and indeterminate remains from the Griman Creek Formation, of New South Wales, Australia, dating to around 100 million years ago. [13] [14]

Classification

A mata mata, Chelus fimbriatus Chelus fimbriatus close.jpg
A mata mata, Chelus fimbriatus

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 the three long-necked genera ( Chelodina , Chelus , and Hydromedusa ) were each other's closest relatives. [15] This was accepted for some time, but brought into scrutiny, [16] 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 their structures 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. [17] [18] 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, [19] Thomson, 2000. [20] 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 twenty genera: [17]

Taxonomy after TTWG 2021 [21]

Phylogeny

Phrynops geoffroanus Phrynops geoffroanus BS 433.JPG
Phrynops geoffroanus

Relationships of the living forms based on Georges et al., 2014. [36] [ citation needed ]

    Chelidae    
                      Hydromedusinae          

   Hydromedusa

  Chelinae    

   Chelus

   Phrynops

   Rhinemys

   Mesoclemmys

   Platemys

   Acanthochelys

  Chelodininae    

   Chelodina

   Pseudemydura

   Elusor

   Rheodytes

   Flaviemys

   Elseya

   Emydura

   Myuchelys

The species in the Chelidae family are distributed across Australia, New Guinea, and South America. Over time they were required to disperse out of concerns of food shortage, habitat destruction, and weather disruptions. In all of these warmer climates, they can be found in turbid waters covered by muck and the root-mats of underwater vegetation. The waters that they are found in often lack large species of fish that would put them at risk of predation.

Related Research Articles

<span class="mw-page-title-main">Eastern long-necked turtle</span> Species of turtle

The eastern long-necked turtle is an east Australian species of snake-necked turtle that inhabits a wide variety of water bodies and is an opportunistic feeder. It is a side-necked turtle (Pleurodira), meaning that it bends its head sideways into its shell rather than pulling it directly back.

<i>Chelodina</i> Genus of turtles

Chelodina, collectively known as snake-necked turtles, is a large and diverse genus of long-necked chelid turtles with a complicated nomenclatural history. Although in the past, Macrochelodina and Macrodiremys have been considered separate genera and prior to that all the same, they are now considered subgenera of the Chelodina, further Macrochelodina and Macrodiremys are now known to apply to the same species, hence Chelydera is used for the northern snake-necked turtles.

<span class="mw-page-title-main">Pleurodira</span> Order of turtles

The Pleurodira are one of the two living suborders of turtles, the other being the Cryptodira. The division between these two suborders represents a very deep evolutionary divide between two very different types of turtles. The physical differences between them, although anatomical and largely internal, are nonetheless significant, and the zoogeographic implications of them are substantial. The Pleurodira are known more commonly as the side-necked turtles and the name Pleurodira quite literally translates to side neck, whereas the Cryptodira are known as hidden-necked turtles. The Pleurodira turtles are currently restricted to freshwater habitats in the Southern Hemisphere, largely to Australia, South America, and Africa. Within the Pleurodira, three living families are represented: Chelidae, also known as the Austro-South American side-necked turtles, the Pelomedusidae, also known as the African mud terrapins, and the Podocnemididae, also known as the American side-neck river turtles. However, they were cosmopolitan clade during the Cretaceous and most of the Cenozoic, and even occurred in marine environments around the world.

<span class="mw-page-title-main">Argentine snake-necked turtle</span> Species of turtle

The Argentine snake-necked turtle, also known commonly as the South American snake-necked turtle is a species of turtle in the family Chelidae. The species is known for the long neck to which its common names refer. Despite appearances, the Argentine snake-necked turtle is probably more closely related to the mata mata than to the Australian snake-necked turtles in the genus Chelodina. H. tectifera is found in northern Argentina, Uruguay, Paraguay, and southern Brazil. Not much is known about it, as it has not been extensively researched. It is a popular pet in the exotic pet trade.

The Namoi River snapping turtle, also commonly known as Bell's turtle, the Namoi River elseya, or Bell's saw-shelled turtle, is a species of turtle in the family Chelidae. The species is endemic to New South Wales, Australia.

<i>Elseya</i> Genus of turtles

Elseya is a genus of large side-necked turtles, commonly known as Australian snapping turtles, in the family Chelidae. Species in the genus Elseya are found in river systems in northern and northeastern Australia and throughout the river systems of New Guinea. They are identified by the presence of alveolar ridges on the triturating surfaces of the mouth and the presence of a complex bridge strut.

<i>Emydura</i> Genus of turtles

Emydura, the Australian short-necked turtles, are a genus of turtles in the family Chelidae. It was paraphyletic with Elseya. Consequently, it was split into two genera Myuchelys and Elseya by Thomson & Georges, 2009. They can grow quite large, 30 cm or more is not unusual and have a life span of around 20–30 years. They generally do not hibernate as their warmer climate lets them remain active all year round; they also spend more time in the water than other varieties. They are considered omnivore but rely on a constant supply of meat to remain healthy, feeding on basically anything that will fit into their mouth.

<i>Hydromedusa</i> Genus of turtles

Hydromedusa is a turtle genus in the family Chelidae, commonly known as the South American snake-necked turtles. They are quite closely related to the South American side-necked swamp turtles (Acanthochelys) and the snake-necked turtles of the Australian-Melanesian region (Chelodina), but less closely to the spine-necked river turtles of South America (Podocnemididae) which belong to a more modern lineage of Pleurodira.

<span class="mw-page-title-main">Fitzroy River turtle</span> Species of turtle

The Fitzroy River turtle is a species of freshwater turtle in the family Chelidae. It is the only surviving member of the genus Rheodytes, the other member being the extinct form Rheodytes devisi. The species is endemic to south eastern Queensland, Australia and only found in tributaries of the Fitzroy River.

<i>Elseya uberrima</i> Extinct species of turtle

Elseya uberrima is a Pliocene species of extinct Australian snapping turtle.

<i>Myuchelys</i> Genus of turtles

The Myuchelys is a genus of turtles, the Australian saw-shelled turtles, in the family Chelidae and subfamily Chelodininae. They inhabit the headwaters and tributaries of rivers within their range and this led to the name Myuchelys, which is formed from the Aboriginal word myuna meaning clear water and the Greek chelys meaning turtle. They have a short neck and the intergular scute completely separates the gular scutes. They have no alveolar ridge separating them from the snapping turtles of the genus Elseya.

<i>Chelodina canni</i> Species of turtle

Chelodina canni, also known commonly as Cann's snake-necked turtle, is a species of turtle in the family Chelidae. The species is endemic to Australia, where it is found in the northern and northeastern parts of the continent. It has a narrow zone of hybridization with its related species the eastern snake-necked turtle, C. longicollis. For many years C. canni was assumed to be the same species as C. novaeguineae from New Guinea. However, in 2002 it was shown that these two species differ both morphologically and genetically, and therefore C. canni was separated and described as a unique species.

<span class="mw-page-title-main">Gulf snapping turtle</span> Species of turtle

The Gulf snapping turtle or Lavaracks' turtle is a large species of freshwater turtle in the sidenecked family Chelidae. The species is endemic to northern Australia in northwest Queensland and northeast Northern Territory. The species, similar to other members of the Australian snapping turtles in genus Elseya, only comes ashore to lay eggs and bask. The Gulf snapping turtle is a herbivore and primarily consumes Pandanus and figs.

<i>Chelodina burrungandjii</i> Species of turtle

Chelodina (Chelydera) burrungandjii, the sandstone snake-necked turtle or Arnhem Land long-necked turtle, is a medium-sized turtle reaching carapace lengths of 316 mm. The species is found in the sandstone plateaus and escarpments and the plunge pools of Arnhem Land of the Northern Territory. The species had been long recognised as valid. However, it had been difficult to research due to the remoteness of its habitat. Efforts to breed this species in captivity had been largely unsuccessful, until National Aquarium Herpetologist Matthew Benedict lead a successful breeding project in 2021. The species occurs in proximity to Chelodina rugosa, to which it is closely related. For the most part the two species are parapatric in distribution. However, they do come together in limited locations such as plunge pools at the base of the escarpments. In these areas there is hybridization between the species.

Prochelidella is an extinct genus of Early to Late Cretaceous chelid turtles from the Bajo Barreal, Candeleros, Cerro Barcino and Portezuelo Formations of the Cañadón Asfalto, Golfo San Jorge and Neuquén Basins in Patagonia, Argentina. It includes the following species:

<i>Chelodina alanrixi</i> Species of turtle

Chelodina alanrixi is a species of snake-necked fossil turtle which was described in 2001 using material gathered in Redbank Plains, Queensland, Australia. It is a member of the Chelidae Pleurodira. The fossil has been dated to the Eocene Epoch.

Yaminuechelys is an extinct genus of chelid turtle from Argentina and the Dorotea Formation of Chile. The genus first appeared during the Late Cretaceous and became extinct during the Late Paleocene.

Lomalatachelys neuquina is an extinct genus and species of chelid turtle from Argentina. The specimen was found in the Loma de La Lata zone approximately 75 km from Neuquen City in north west Patagonia, Argentina.

<i>Elseya rhodini</i> Species of New Guinea turtle

Elseya rhodini, the southern New Guinea stream turtle, is a recently described aquatic species of chelid turtle found south of the central ranges of New Guinea. It inhabits small streams that flow into the major river drainage's south of the ranges.

<span class="mw-page-title-main">Scott A. Thomson</span> Australian herpetologist

Scott A. Thomson is an Australian herpetologist, paleontologist, and taxonomist, specialising in turtles of the family Chelidae.

References

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  2. ↑ Obst, Fritz Jurgen (1998). Cogger, H. G.; Zweifel, R. G. (eds.). 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. & Lee, M. (eds.) Evolution and Zoogeography of Australasian Vertebrates. Sydney: Australia.
  4. ↑ Gordos, M. A.; Franklin, C. E. & Limpus, C. J. (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.
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  6. ↑ Thomson, S.; Georges, A. & Limpus, C. (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. ↑ Badenhorst, Daleen; Stanyon, Roscoe; Engstrom, Tag; Valenzuela, Nicole (2013-03-20). "A ZZ/ZW microchromosome system in the spiny softshell turtle, Apalone spinifera, reveals an intriguing sex chromosome conservation in Trionychidae". Chromosome Research. 21 (2): 137–147. doi:10.1007/s10577-013-9343-2. ISSN   0967-3849. PMID   23512312. S2CID   14434440.
  8. 1 2 Thomson, S. & Georges, A. (1996). "Neural bones in chelid turtles". Chelonian Conservation and Biology 2: 82-86.
  9. 1 2 Thomson S. (2003). "Long necks, flat heads and the evolution of piscivory". World Chelonian Trust.
  10. ↑ Pritchard, Peter C. H. & Trebbau, Pedro (1984). The Turtles of Venezuela . Society for the Studies of Amphibians and Reptiles: 403 pp.
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  12. ↑ Krause, J. Marcelo; Ramezani, Jahandar; Umazano, Aldo M.; Pol, Diego; Carballido, José L.; Sterli, Juliana; Puerta, Pablo; Cúneo, N. Rubén; Bellosi, Eduardo S. (April 2020). "High-resolution chronostratigraphy of the Cerro Barcino Formation (Patagonia): Paleobiologic implications for the mid-cretaceous dinosaur-rich fauna of South America". Gondwana Research. 80: 33–49. Bibcode:2020GondR..80...33K. doi:10.1016/j.gr.2019.10.005. S2CID   210265289.
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  14. ↑ Bell, Phil R.; Fanti, Federico; Hart, Lachlan J.; Milan, Luke A.; Craven, Stephen J.; Brougham, Thomas; Smith, Elizabeth (January 2019). "Revised geology, age, and vertebrate diversity of the dinosaur-bearing Griman Creek Formation (Cenomanian), Lightning Ridge, New South Wales, Australia". Palaeogeography, Palaeoclimatology, Palaeoecology. 514: 655–671. Bibcode:2019PPP...514..655B. doi:10.1016/j.palaeo.2018.11.020. hdl: 11585/651841 . S2CID   134264936.
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  17. 1 2 Georges, A.; Birrell, J.; Saint, K. M.; McCord, W. & Donnellan, S. C. (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.
  18. ↑ Seddon, J.; Georges, A.; Baverstock, P. & 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.
  19. ↑ Thomson S. (2003). "Long necks, flat heads and the evolution of piscivory". World Chelonian Trust
  20. ↑ 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.
  21. ↑ Rhodin, Anders G.J.; Iverson, John B.; Bour, Roger; Fritz, Uwe; Georges Arthur; Shaffer, H. Bradley; van Dijk, Peter Paul (2021-12-01). "Turtles of the World: Annotated Checklist and Atlas of Taxonomy, Synonymy, Distribution, and Conservation Status (9th Ed.)" (PDF). Chelonian Research Monographs. 8: 1–472. doi:10.3854/crm.8.checklist.atlas.v9.2021. ISBN   9780991036837. S2CID   244279960.
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  28. ↑ 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.
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  34. ↑ Zhang, X.; Unmack, P. J.; Kuchling, G.; Wang, Y. & Georges, A. (October 2017). "Resolution of the enigmatic phylogenetic relationship of the critically endangered Western Swamp Tortoise Pseudemydura umbrina (Pleurodira: Chelidae) using a complete mitochondrial genome". Molecular Phylogenetics and Evolution. 115: 58-61.
  35. ↑ Seibenrock, F. (1901). "Beschreibung einer neuen schildkrotengattung aus der familie Chelydidae aus Australien: Pseudemydura". Anzeiger der Akademie der Wissenschaften in Wien. 38: 248-251.
  36. ↑ Georges, Arthur; Zhang, Xiuwen; Unmack, Peter; Reid, Brenden N.; Le, Minh; McCord, William P. (2014). "Contemporary genetic structure of an endemic freshwater turtle reflects Miocene orogenesis of New Guinea". Biological Journal of the Linnean Society. 111 (1): 192–208. doi: 10.1111/bij.12176 . ISSN   0024-4066. S2CID   4950570.
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