Chelidae
Encyclopedia
The Chelidae are one of the three living families of the turtle
suborder Pleurodira
and are commonly called the Austro-South American Side Neck turtles. 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 going back to the Cretaceous. The family is entirely Gondwana
n in its origin with no members found outside of Gondwana, either in the present day or as a fossil.
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, several species have specialized to eating fruits.
The highly aquatic nature of the group is typified by the presence of Cloaca
l Breathing in some species of the genera Elseya
and Rheodytes
. However, species such as the Eastern Long-Neck Turtle (Chelodina longicollis) from Australia spend significant periods of time on land and is considered highly terrestrial
.
The smaller members of the family include the Macleay River Turtle (Emydura macquarii
) at around 16 cm, 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.
There have been a number of theories of the relationshps within the large Chelidae family. Using shared derived characters an early attempt in the 1970s used strict parsimony to determine that the 3 long-necked genera (Chelodina
, Chelus and Hydromedusa
) were each others closest relatives (Gaffney, 1977). This was accepted for sometime but brought into scrutiny by Pritchard (1984) who discussed the major differences between the 3 genera showing that 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 datasets were developed that used electrophoresis and nuclear and mtDNA analysis these all agreed on the independent evolution of the 3 long-necked clades (Georges et al. 1998, Seddon et al., 1997). This was culminated in a re-analysis of the morphological data which demonstrated the convergence of the 3 clades on a sweep of distinctive features needed for their piscivorous diet (Thomson, 2003, Thomson, 2000. The 3 sub-families within the 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 approximately 60 species within around 20 genera.
Following based on Georges et al. 1998.
Suborder Pleurodira
Turtle
Turtles are reptiles of the order Testudines , characterised by a special bony or cartilaginous shell developed from their ribs that acts as a shield...
suborder Pleurodira
Pleurodira
The Pleurodira are one of the two living suborders of turtles, the other being the Cryptodira. In many cases in the nomenclature of animals, ranks such as suborder are considered of little importance apart from nomenclatural or taxonomic reasons. However, this is not the case with the suborders of...
and are commonly called the Austro-South American Side Neck turtles. The Family is distributed in Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
, New Guinea
New Guinea
New Guinea is the world's second largest island, after Greenland, covering a land area of 786,000 km2. Located in the southwest Pacific Ocean, it lies geographically to the east of the Malay Archipelago, with which it is sometimes included as part of a greater Indo-Australian Archipelago...
, parts of Indonesia
Indonesia
Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...
and throughout most of South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
. It is a large family of turtles with a significant fossil history going back to the Cretaceous. The family is entirely Gondwana
Gondwana
In paleogeography, Gondwana , originally Gondwanaland, was the southernmost of two supercontinents that later became parts of the Pangaea supercontinent. It existed from approximately 510 to 180 million years ago . Gondwana is believed to have sutured between ca. 570 and 510 Mya,...
n in its origin with no members found outside of Gondwana, either in the present day or as a fossil.
Description
Like all Pleurodirous turtles the Chelid's withdraw their necks sideways into the shell, differing from Cryptodire's 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, ChelodinaChelodina
This large and diverse genus of long-necked Chelid turtles has had a complicated nomenclatural history. Although in the past the following have been considered separate genera and prior to that all the same, they are now considered sub-genera of the one genus....
and Hydromedusa
Hydromedusa
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 and the snake-necked turtles of the Australian-Melanesian region , but less closely to the side-necked...
) 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, several species have specialized to eating fruits.
The highly aquatic nature of the group is typified by the presence of Cloaca
Cloaca
In zoological anatomy, a cloaca is the posterior opening that serves as the only such opening for the intestinal, reproductive, and urinary tracts of certain animal species...
l Breathing in some species of the genera Elseya
Elseya
The Australian Snapping Turtles, Elseya Gray 1867, are a large genus of side-necked turtles in the family Chelidae found in river systems in northern and north eastern Australia and throughout the river systems of New Guinea...
and Rheodytes
Rheodytes
Rheodytes is a genus of turtle in the Chelidae family.It contains the following species:* Fitzroy River Turtle * Rheodytes devisi...
. However, species such as the Eastern Long-Neck Turtle (Chelodina longicollis) from Australia spend significant periods of time on land and is considered highly terrestrial
Terrestrial animal
Terrestrial animals are animals that live predominantly or entirely on land , as compared with aquatic animals, which live predominantly or entirely in the water , or amphibians, which rely on a combination of aquatic and terrestrial habitats...
.
The smaller members of the family include the Macleay River Turtle (Emydura macquarii
Emydura macquarii
The Murray River Turtle is a wide ranging species that occurs throughout many of the rivers of the eastern half of Australia. It is found primarily in the Murray River Basin and all its major tributaries, along with a number of coastal rivers up the New South Wales Coast...
) at around 16 cm, 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
Elseya albagula
The White Throated Snapping Turtle is one of the largest species of Chelid Turtles in the world growing to approximately 45 cm carapace length. The species is endemic to south-eastern Queensland, Australia found in the Burnett, Mary and Fitzroy River Drainages...
) both exceed 45 cm in shell length.
Shell morphology
| Members of the Chelidae have unique shell morphology. The carapace Carapace A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the... often has reduced surface exposure of neural bones, or even none at all (Thomson & Georges, 1996). This is due to less requirement for enlarged longissimus dorsi muscles in side necked turtles (Thomson, 2003). 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) demonstrated it is linked to feeding methods and the prevention of internal torsion of the shell. Chelid's also lack Mesoplastra which separates them from the Pelomedusidae Pelomedusidae Pelomedusidae is a family of freshwater turtles, native to eastern and southern Africa. They range in size from to in shell length, and are generally roundish in shape... . The cervical scute is usually present though it is absent in some species of Elseya Elseya The Australian Snapping Turtles, Elseya Gray 1867, are a large genus of side-necked turtles in the family Chelidae found in river systems in northern and north eastern Australia and throughout the river systems of New Guinea... and Myuchelys Myuchelys The Australian Saw Shelled Turtles, Myuchelys, are a genus of turtles in the family Chelidae. They inhabit the headwaters and tributaries of rivers within their range and this led to the name Myuchelys, which is formed from the Aboriginal words Myuna meaning high water and chelys meaning turtle... . Otherwise the carapace has the usual complement of 4 costals, 5 vertebrals and 12 marginals (per side). Internally the carapace is made of 8 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. 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 Pleurodira The Pleurodira are one of the two living suborders of turtles, the other being the Cryptodira. In many cases in the nomenclature of animals, ranks such as suborder are considered of little importance apart from nomenclatural or taxonomic reasons. However, this is not the case with the suborders of... and can be used to immediately identify a shell as belonging to this suborder. All Cryptodire's 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). |
Classification
Chelodina
This large and diverse genus of long-necked Chelid turtles has had a complicated nomenclatural history. Although in the past the following have been considered separate genera and prior to that all the same, they are now considered sub-genera of the one genus....
, Chelus and Hydromedusa
Hydromedusa
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 and the snake-necked turtles of the Australian-Melanesian region , but less closely to the side-necked...
) were each others closest relatives (Gaffney, 1977). This was accepted for sometime but brought into scrutiny by Pritchard (1984) who discussed the major differences between the 3 genera showing that 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 datasets were developed that used electrophoresis and nuclear and mtDNA analysis these all agreed on the independent evolution of the 3 long-necked clades (Georges et al. 1998, Seddon et al., 1997). This was culminated in a re-analysis of the morphological data which demonstrated the convergence of the 3 clades on a sweep of distinctive features needed for their piscivorous diet (Thomson, 2003, Thomson, 2000. The 3 sub-families within the 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 approximately 60 species within around 20 genera.
Following based on Georges et al. 1998.
Suborder Pleurodira
- Family PelomedusidaePelomedusidaePelomedusidae is a family of freshwater turtles, native to eastern and southern Africa. They range in size from to in shell length, and are generally roundish in shape...
- Family PodocnemididaePodocnemididaePodocnemididae is a family of turtles native to Madagascar and northern South America. They are side-necked turtles , which means they do not retract their heads backwards, but hide it sideways....
- Family CHELIDAE Gray, 1831
- Subfamily Chelodininae
- Genus ChelodinaChelodinaThis large and diverse genus of long-necked Chelid turtles has had a complicated nomenclatural history. Although in the past the following have been considered separate genera and prior to that all the same, they are now considered sub-genera of the one genus....
Fitzinger 1826 – Australian Snake-necked Turtles - Genus ElseyaElseyaThe Australian Snapping Turtles, Elseya Gray 1867, are a large genus of side-necked turtles in the family Chelidae found in river systems in northern and north eastern Australia and throughout the river systems of New Guinea...
Gray 1867 – Australian Snapping Turtles - Genus EmyduraEmyduraThe Australian short-necked turtles, Emydura, 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....
Bonaparte 1836 – Australian Short-necked Turtles - Genus ElusorMary River TurtleThe Mary River turtle, Elusor macrurus, is an endangered short-necked turtle that inhabits the Mary River in South-East Queensland, Australia. In the 1960s and 1970s, they were popular as pets in Australia, with about 15,000 sent to shops every year during a ten-year period. They were originally...
, Cann & Legler, 1994 – Mary River Turtle - Genus MyuchelysMyuchelysThe Australian Saw Shelled Turtles, Myuchelys, are a genus of turtles in the family Chelidae. They inhabit the headwaters and tributaries of rivers within their range and this led to the name Myuchelys, which is formed from the Aboriginal words Myuna meaning high water and chelys meaning turtle...
Thomson & Georges 2009 – Australian Saw Shelled Turtles - Genus Pseudemydura Siebenrock 1901 – Western Swamp TortoiseWestern Swamp TortoiseThe western swamp tortoise , also known as the western swamp turtle, is a short-necked freshwater tortoise that monotypically represents the sub-family Pseudemydurinae.-Description:...
- Genus RheodytesRheodytesRheodytes is a genus of turtle in the Chelidae family.It contains the following species:* Fitzroy River Turtle * Rheodytes devisi...
Legler and Cann 1980, – Fitzroy River Turtles
- Genus Chelodina
- Subfamily Chelidinae
- Genus Chelus Duméril 1806 – Matamata Turtles
- Genus AcanthochelysAcanthochelysAcanthochelys is a genus of turtle in the Chelidae family.It contains the following species:* Big-headed pantanal swamp turtle * Chaco side-necked turtle...
Gray, 1873 – South American Side-necked Swamp Turtles - Genus MesoclemmysMesoclemmysMesoclemmys is a genus of turtle in the Chelidae family.Species include:* Mesoclemmys dahli - Dahl's toad-headed turtle* Mesoclemmys gibba - Gibba turtle* Mesoclemmys heliostemma* Mesoclemmys hogei - Hoge's side-necked turtle...
– Gibba Turtle - Genus PhrynopsPhrynopsSometimes called the bearded toadheads but better known by their scientific name of Phrynops this genus of turtles has often been a bit of a dumping ground for the short-necked South American turtles of the family Chelidae....
– Toad-headed Turtles - Genus PlatemysTwist-necked turtleThe Twist-necked turtle, Platemys platycephala, also known as the flat-headed turtle is distributed widely across northern South America. Twist-necked turtles have extremely flat shells that help them hide from predators under rocks and debris. When threatened, this turtle withdraws by twisting its...
Wagner 1830 – Twisted-necked Turtles - Genus RhinemysRhinemysRhinemys is a genus of turtle in the Chelidae family.Species include:* Rhinemys rufipes – Red side-necked turtle...
– Red-headed Sideneck Turtle - Genus †Bonapartemys Lapparent de Broin and de la Fuente 2001
- Genus †Lomalatachelys Lapparent de Broin and de la Fuente 2001
- Genus †Prochelidella Lapparent de Broin and de la Fuente 2001
- Genus †Palaeophrynops Lapparent de Broin and de la Fuente 2001
- Genus †ParahydraspisParahydraspisParahydraspis is an extinct genus of turtle.-Sources:* The Osteology of the Reptiles by Alfred Sherwood Romer...
Wieland 1923 - Genus †Linderochelys de la Fuente et al. 2007
- Subfamily Hydromedusinae
- Genus HydromedusaHydromedusaHydromedusa 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 and the snake-necked turtles of the Australian-Melanesian region , but less closely to the side-necked...
Wagler 1830 – South American Snake-necked Turtles - Genus †Yaminuechelys de la Fuente et al. 2001
- Genus Hydromedusa
- Subfamily Chelodininae
| Key to Australasian Chelidae |
|---|
1 Forelimbs each with five claws; gular scutes separated by the intergular; intergular scute in broad contact with the anterior margin of the plastron 2 – Forelimbs each with four claws; gular scutes in contact; intergular scute not in broad contact with the anterior margin of the plastron Chelodina Chelodina This large and diverse genus of long-necked Chelid turtles has had a complicated nomenclatural history. Although in the past the following have been considered separate genera and prior to that all the same, they are now considered sub-genera of the one genus.... 2 Intergular scute not in contact with the pectoral scutes 3 – Intergular scute contacts and partly separates the pectoral scutes Pseudemydura 3 Suture between the second and third costal scutes contacting the seventh marginal scute; suture between the third and fourth costal scutes contacting the ninth marginal scute 4 – Suture between the second and third costal scutes contacting the sixth marginal scute; suture between the third and fourth costal scutes contacting the eighth marginal scute Rheodytes Rheodytes Rheodytes is a genus of turtle in the Chelidae family.It contains the following species:* Fitzroy River Turtle * Rheodytes devisi... 4 Surface of the temporal region covered with distinct regular scales or low tubercles; dorsal surface of the head with a prominent head shield which may be entire or fragmented; cervical scute present or absent 5 – Skin of the temporal region smooth, sometimes broken into regular scales of low relief; dorsal surface of head without a prominent head shield; cervical scute present (except as a rare variant) Emydura Emydura The Australian short-necked turtles, Emydura, 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.... 5 Precloacal tail length greater than postcloacal length only in adult males; tail round in cross section; cloacal orifice round; tail always shorter than half of carapace length 6 – Tail distinctive and large; precloacal length greater than postcloacal length at all ages in both sexes; tail laterally compressed; cloacal orifice a longitudinal slit; tail up to 53% of carapace length in adult males Elusor 6 Prominent alveolar ridge on the triturating surfaces of the mouth; cervical scute absent (except as a rare variant); no prominent process of the head shield extending down the parietal ridge toward the tympanum Elseya Elseya The Australian Snapping Turtles, Elseya Gray 1867, are a large genus of side-necked turtles in the family Chelidae found in river systems in northern and north eastern Australia and throughout the river systems of New Guinea... –Alveolar ridge absent; cervical scute absent in Australian species (except as a rare variant), present in New Guinea species (except as a rare variant); posterior process of the head shield extends laterally down the parietal ridge toward the tympanum Myuchelys Myuchelys The Australian Saw Shelled Turtles, Myuchelys, are a genus of turtles in the family Chelidae. They inhabit the headwaters and tributaries of rivers within their range and this led to the name Myuchelys, which is formed from the Aboriginal words Myuna meaning high water and chelys meaning turtle... |