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Cheloniidae is a family of typically large marine turtles that are characterised by their common traits such as, having a flat streamlined wide and rounded shell and almost paddle-like flippers for their forelimbs. The six species that make up this family are: the
green sea turtle The green sea turtle (''Chelonia mydas''), also known as the green turtle, black (sea) turtle or Pacific green turtle, is a species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank ...

green sea turtle
,
loggerhead sea turtle The loggerhead sea turtle (''Caretta caretta''), is a species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often d ...

loggerhead sea turtle
,
olive ridley sea turtle The olive ridley sea turtle (''Lepidochelys olivacea''), also known commonly as the Pacific ridley sea turtle, is a species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an or ...

olive ridley sea turtle
,
hawksbill sea turtle The hawksbill sea turtle (''Eretmochelys imbricata'') is a critically endangered sea turtle Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines Turtles are reptile Reptiles ...

hawksbill sea turtle
,
flatback sea turtle The Australian flatback sea turtle (''Natator depressus'') is a species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species ...
and the
Kemp's ridley sea turtle Kemp's ridley sea turtle (''Lepidochelys kempii''), also called the Atlantic ridley sea turtle, is the rarest species of sea turtle and is the world's most endangered species, endangered species of sea turtle. It is one of two living species in ...
.


Morphology

In contrast to their earth-bound relatives,
tortoise Tortoises () are reptiles Reptiles, as most commonly defined, are the animals in the class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a ...

tortoise
s,
sea turtle Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines Turtles are reptile Reptiles are tetrapod Tetrapods (; from Greek 'four' and 'foot') are four-limbed animals constitut ...

sea turtle
s do not have the ability to retract their heads into their shells. Their plastron, which is the bony plate making up the underside of a turtle or tortoise's shell, is comparably more reduced from other turtle species and is connected to the top part of the shell by ligaments without a hinge separating the pectoral and abdominal plates of the plastron. Sizes among the seven species of sea turtles range from 71 to 213 cm; for example, the smallest turtle species in the family Cheloniidae, the Kemp's Ridley, only has a shell size of about 75 cm and a weight of 50 kg. All species have a distinct hardened shell.


Reproduction and life cycle

Reproductive behaviors among the different species of sea turtles are similar, with slight differences in each of the species. The females come to shore and bury their clutch of eggs on beaches or sandy environments typically at night and well away from the high tide line of the shore. Most females nest only once every three to four years and most species have two to four egg laying time periods per nesting season, which is from spring to late fall. A common number of eggs laid in a nest is often about 100 eggs per clutch. The incubation period of some turtles can range anywhere from 50 to 60 days. The development of the eggs is dependent on the temperature of the environment that they were buried in, with warmer climates bringing about an earlier emergence by the hatchlings. The timing of sea turtle hatching tends to be almost synchronous among the whole clutch of eggs, with just about all the eggs in the nest hatching within the same time. This is thought to aid the process of the hatchlings unburying themselves from the sand and most often occurs at night time. Temperature has also been linked to the likeliness of hatching's sex, warmer temperature more likely to produce females and colder temperatures more commonly producing males.


Habitat and ecology

The habitat range of sea turtles, in general, is known to be far reaching into warmer temperatures and the tropical and subtropical areas of the Pacific and Atlantic Oceans and is even also found in warmer seas such as the Mediterranean Sea. Within these temperamental biomes, sea turtles frequent near by the coastlines when nesting, and spend most of their lives swimming out in waters over the continental shelf when feeding. Travelling throughout the oceans has been reported in Olive Ridleys Sea Turtles but more often than not, they tend to frequent bays and estuaries. The diets of all the sea turtle species, except for the Green Sea Turtle, which is only carnivorous from hatchling to juvenile, are mostly carnivorous, with some herbivorous tendencies. Sea turtles feed mainly on sea sponges, jellyfish, mollusks and barnacles, sea urchins, and even fish. The green sea turtle, on the other hand, feeds primarily on many different types of sea grasses.


Conservation status and significance to humans

The conservation status of each of the seven turtle species are mostly all endangered or threatened. The green and loggerhead sea turtles are categorized as endangered, Olive Ridleys are classified as vulnerable, Kemp's Ridleys, and Hawksbills sea turtles are critically endangered and the Flat Back sea turtle does not have enough data to draw an accurate conclusion on conservation status. Many do not ever make it to full adulthood because of being caught, either intentionally or by accident by big fisheries and fishermen. Their slow maturity rate, which most of the time means about 10 or 15 years, does not allow the turtles which have been caught to have fully reproductively matured and to have produced hatchlings of their own. International legislation has been put into place to attempt to reduce the number of sea turtle deaths but this does not deter the demand for the consumption of turtle eggs around the world, and some are hunted for their shells. In addition to this, turtles face another threat which has been theorized as being linked to human pollution. A growing number of turtles have been found with fibropapillomatosis, fibrous tumor growths on their skin, mouths, and even internal organs. In some areas the number of infected turtles is over 70%. It is unknown what the effects of the growths will have in the long term for sea turtle populations. Sea turtles play a very important part in marine ecosystems. They maintain the balance of health of sea grasses and reefs, which in turn benefit the likes of shrimp, lobsters, and tunas. They are also the last living members of the seafaring category of marine reptiles that have been in existence on Earth for at least the past 100 million years. They are also highly significant to multiple cultures and are also popular animals in tourism, which gives a higher importance to their conservation.


Classification


Extant genera

*Subfamily Carettinae **Genus ''
Caretta The loggerhead sea turtle (''Caretta caretta''), is a species of sea turtle, oceanic turtle distributed throughout the world. It is a marine reptile, belonging to the Family (biology), family Cheloniidae. The average loggerhead measures around ...
'' ***Loggerhead sea turtle (''Caretta caretta'') **Genus ''Lepidochelys'' ***
Kemp's ridley sea turtle Kemp's ridley sea turtle (''Lepidochelys kempii''), also called the Atlantic ridley sea turtle, is the rarest species of sea turtle and is the world's most endangered species, endangered species of sea turtle. It is one of two living species in ...
(''Lepidochelys kempii'') ***Olive ridley sea turtle (''Lepidochelys olivacea'') *Subfamily Cheloniinae **Genus ''Chelonia (genus), Chelonia'' ***Green sea turtle (''Chelonia mydas'') **Genus ''Eretmochelys'' ***Hawksbill sea turtle (''Eretmochelys imbricata'') **Genus ''Natator'' ***Flatback sea turtle (''Natator depressus'') (previously in ''Chelonia'')


Cladogram

Below is a cladogram showing the phylogenetic relationships of living and extinct sea turtles in the family Cheloniidae based on Lynch and Parham (2003) and Parham and Pyenson (2010).


Extinct genera

*Genus †''Allopleuron'' *Genus †''Argillochelys'' *Genus †''Cabindachelys''Myers, T.S., Polcyn M.J., Mateus O., Vineyard D.P., Gonçalves A.O., & Jacobs L.L. (2017). "A new durophagous stem cheloniid turtle from the lower Paleocene of Cabinda, Angola." ''Papers in Palaeontology'' 1-16. *Genus †''Carolinochelys *Genus †''Catapleura'' *Genus †''Erquelinnesia'' *Genus †''Gigantatypus'' *Genus †''Glyptochelone'' *Genus †''Itilochelys *Genus †''Lytoloma'' *Genus †''Osteopygis'' *Genus †''Pampaemys'' *Genus †''Peritresius'' *Genus †''Porthochelys'' *Genus †''Prionochelys'' *Genus †''Procolpochelys'' *Genus †''Retechelys'' *Genus †''Syllomus'' *Genus †''Tasbacka'' *Genus †''Thinochelys'' *Genus †''Miocaretta''


References


External links

* Skaphandrus.co
Cheloniidae


Bibliography

* {{Authority control Cheloniidae, Taxa named by Nicolaus Michael Oppel Turtle families Extant Paleocene first appearances Thanetian taxonomic families Ypresian taxonomic families Lutetian taxonomic families Bartonian taxonomic families Priabonian taxonomic families Rupelian taxonomic families Chattian taxonomic families Aquitanian taxonomic families Burdigalian taxonomic families Langhian taxonomic families Serravallian taxonomic families Tortonian taxonomic families Messinian taxonomic families Zanclean taxonomic families Piacenzian taxonomic families Gelasian taxonomic families Calabrian taxonomic families Ionian taxonomic families Tarantian taxonomic families Holocene taxonomic families