27-765: Platychelyidae is an extinct family of pan- pleurodiran turtles, known from the Late Jurassic and Early Cretaceous of Europe, South America, North America, and the Caribbean. It represents the oldest known clade of stem-pleurodires. All known members have been found in marine or coastal deposits. Despite this, their limb morphology suggests that they were not adapted for open marine conditions, but were likely inhabitants of shallow water environments, including brackish and saline waters, and they likely never inhabited environments more marine than lagoons . Their tolerance for saline environments likely aided their dispersal during
54-458: 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 –Alveolar ridge absent; cervical scute absent in Australian species (except as
81-753: 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 Relationships of the living forms based on Georges et al., 2014. Hydromedusa Chelus Phrynops Rhinemys Mesoclemmys Platemys Acanthochelys Chelodina Pseudemydura Elusor Rheodytes Flaviemys Elseya Emydura Myuchelys The species in
108-515: 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). 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
135-451: Is due to less requirement for enlarged longissimus dorsi muscles in side-necked turtles. 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. Chelids also lack mesoplastra, which separates them from
162-560: Is one of three living families of the turtle suborder Pleurodira , and are commonly called 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 dating back to the Cretaceous. The family is entirely Gondwanan in origin, with no members found outside Gondwana, either in
189-761: 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. The Pleurodira are identified by the method with which they withdraw their heads into their shells. In these turtles,
216-403: 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 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
243-462: The cervical vertebrae . All extant turtles studied so far have eight vertebrae in the neck. In the Pleurodira, these vertebrae are narrow in cross-section and spool-shaped with biconvex centra on one or more of the cervicals. These centra act as a double joint, allowing a large degree of sideways movement and providing a means of folding the neck onto itself in the lateral plane. Conversely, in
270-581: The 1970s used strict parsimony to determine the three long-necked genera ( Chelodina , Chelus , and Hydromedusa ) were each other's closest relatives. This was accepted for some time, but brought into scrutiny, 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
297-464: The Cryptodira, the neck bones are wide and flat. The biconvex centra in some of the cryptodiran cervicals allow the neck to fold onto itself in the vertical plane. Pleurodirans also differ from cryptodirans in the emarginations of their skulls. Skull emargination provides room and anchorage for the jaw muscles. The connection points and the position of the emarginations relate to different bones of
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#1732772127795324-435: The breakup of Pangea. Unlike modern pleurodires, which retract their necks to the sides, Platychelys retracted its neck inwards, similar to modern cryptodire turtles. Platychelys is strongly morphologically similar to mata mata and snapping turtles , suggesting that it had a similar ecology as a ram or suction feeder. After Pleurodira The Pleurodira are one of the two living suborders of turtles ,
351-552: The group is typified by the presence of cloacal breathing in some species of the genera Elseya and Rheodytes . 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, twist-necked turtle ( Platemys platycephala ) at 18 cm and
378-676: 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 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
405-764: The independent evolution of the three long-necked clades. 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, Thomson, 2000. 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: Taxonomy after TTWG 2021 1 Forelimbs each with five claws; gular scutes separated by
432-443: 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 2 Intergular scute not in contact with the pectoral scutes 3 – Intergular scute contacts and partly separates the pectoral scutes Pseudemydura 3 Suture between
459-688: 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, and indeterminate remains from the Griman Creek Formation , of New South Wales, Australia, dating to around 100 million years ago. A number of theories of the relationships within the large chelid family have been posited. Using shared derived characters, an early attempt in
486-547: 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,
513-431: The neck is bent in the horizontal plane, drawing the head into a space in front of one of the front legs. A larger overhang of the carapace helps to protect the neck, which remains partially exposed after retraction. This differs from the method employed by a cryptodiran , which tucks its head and neck between its forelegs, within the shell. The different methods of bending the neck require completely different anatomies of
540-462: 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
567-674: The present day or as a fossil. 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
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#1732772127795594-482: The pterygoid. One of the three extant families in this suborder is the family Chelidae , which have a specially adapted strategy for catching prey. While the majority of the family Chelidae are omnivores, 17 species are carnivorous: Chelus fimbriatus and species of the Chelodina genus. This special strategy is referred to as a gape-suck mechanism. The turtle first opens its mouth little by little. Then, when
621-474: 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 4 Surface of the temporal region covered with distinct regular scales or low tubercles; dorsal surface of
648-449: 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 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
675-477: The skull. Another difference is in the arrangement of the bones of the shell and the scutes overlaying them. Pleurodiran turtles have 13 scutes on the plastron of the shell, whereas cryptodiran turtles have only 12. The extra scute is called the intergular and is at the front of the plastron between the gular scutes . Pelomedusid turtles also possess mesoplastra , further differentiating this group. The jaw closure mechanism has articulation on trochlear surfaces of
702-516: The turtle is within striking range of the prey, it will open its mouth completely, sucking in water at such a rate that the current into its mouth is too strong for prey to escape and it engulfs the prey within 0.004 seconds. This strategy also circumvents issues to quick capture of underwater prey, such as resistance to rapid movement in water, pressure waves due to a rapid strike, and rapid water intake when feeding. After Ferreria, et al. 2018. Chelidae Around 20., see text Chelidae
729-526: 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. Chelids exhibit XX/XY genetic sex determination , in contrast to most other turtles, which have temperature-dependent sex determination . Chelid turtles have unique shell morphology. The carapace often has reduced surface exposure of neural bones, or even none at all. This
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