Cheloniidae

In contrast to their earth-bound relatives, tortoises, sea turtles 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.{{Cite web |title=Information About Sea Turtles: Leatherback Sea Turtle – Sea Turtle Conservancy |url=https://conserveturtles.org/information-about-sea-turtles-leatherback-sea-turtle/ |access-date=2024-02-01 |language=en-US}}

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."Sea Turtle Species" World Wildlife https://www.worldwildlife.org/species/sea-turtle

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.{{Cite web |title=Seaturtles (Cheloniidae) {{!}} Encyclopedia.com |url=https://www.encyclopedia.com/environment/encyclopedias-almanacs-transcripts-and-maps/seaturtles-cheloniidae |access-date=2024-02-01 |website=www.encyclopedia.com}} 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.{{cite web | url=http://eol.org/pages/8123/overview | title=Sea turtles - Encyclopedia of Life }} Travelling throughout the oceans has been reported in olive ridley 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 herbivorous 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.{{cite web | url=http://animals.nationalgeographic.com/animals/reptiles/green-turtle | archive-url=https://web.archive.org/web/20100123163239/http://animals.nationalgeographic.com/animals/reptiles/green-turtle | archive-date=23 January 2010 | title=Green Turtles, Green Turtle Pictures, Green Turtle Facts - National Geographic }}

Sea turtles are ectotherms, meaning their life history traits, behaviors, and physiology are impacted by environmental temperature, which determines sea turtle sex-ratio and hatching success.{{cite journal |last1=Fuentes |first1=M.M.P.B. |last2=Limpus |first2=C.J. |last3=Hamann |first3=M. |title=Vulnerability of sea turtle nesting grounds to climate change |journal=Global Change Biology |date=January 2011 |volume=17 |issue=1 |pages=140–153 |doi=10.1111/j.1365-2486.2010.02192.x |bibcode=2011GCBio..17..140F }} This sensitivity makes them highly vulnerable to increasing temperatures and events related to climate change. Temperature increases also drive processes like sea-level rise and cyclonic activity, both of which can alter nesting environments and increase the risk of embryo mortality.{{cite journal |last1=Gammon |first1=Malindi |last2=Whiting |first2=Scott |last3=Fossette |first3=Sabrina |title=Vulnerability of sea turtle nesting sites to erosion and inundation: A decision support framework to maximize conservation |journal=Ecosphere |date=June 2023 |volume=14 |issue=6 |doi=10.1002/ecs2.4529 |bibcode=2023Ecosp..14E4529G |doi-access=free }}

A study predicted that by 2070, nesting grounds of Chelonia mydas in the Northern Great Barrier Reef would be most vulnerable to higher temperatures, with temperature posing a greater threat than sea-level rise and cyclonic activity. Mitigating temperature-related threats will have the greatest impact on reducing nesting site vulnerability. Climate risks will vary geographically and across species as different species of sea turtles will adapt their nesting behavior and ecology in response to ongoing climate change.{{cite journal |last1=Stokes |first1=Holly J. |last2=Esteban |first2=Nicole |last3=Hays |first3=Graeme C. |title=Nest site selection in sea turtles shows consistencies across the globe in the face of climate change |journal=Animal Behaviour |date=February 2024 |volume=208 |pages=59–68 |doi=10.1016/j.anbehav.2023.12.001 |bibcode=2024AnBeh.208...59S |doi-access=free }}

Despite rising temperatures, sea turtles have shown resilience to climate changes in the past that have allowed them to persist for millions of years.{{cite journal |last1=Santidrián Tomillo |first1=Pilar |last2=Spotila |first2=James R. |title=Temperature-Dependent Sex Determination in Sea Turtles in the Context of Climate Change: Uncovering the Adaptive Significance |journal=BioEssays |date=November 2020 |volume=42 |issue=11 |pages=e2000146 |doi=10.1002/bies.202000146 |pmid=32896903 }} Cheloniidae and Dermochelyidae (sister group) are the only sea turtle families that have survived extreme periods of climatic fluctuation, thus they may adapt to future climate conditions.

The conservation status of each of the seven turtle species are either endangered, threatened or data deficient (Flatback). The green and loggerhead sea turtles are categorized as endangered, olive ridley are classified as vulnerable, Kemp's ridley, and hawksbill sea turtles are critically endangered and the flatback sea turtle does not have enough data to draw an accurate conclusion on conservation status.{{Cite web |title=Sea Turtle Threats |url=https://www.seeturtles.org/sea-turtles-threats/ |access-date=2024-11-22 |website=SEE Turtles |language=en-US}}

Most do not reach sexual maturity before becoming prey to other organisms, or being caught by humans either intentionally or as bycatch by commercial fishing operations. 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.{{fact|date=May 2025}}

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.{{cite web |url=https://myfwc.com/research/wildlife/sea-turtles/threats/fibropapillomatosis/ |title=Fibropapillomatosis and Its Effect on Green Turtles |work=Florida Fish and Wildlife Conservation Commission }}

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.{{cite web | url=https://www.worldwildlife.org/species/sea-turtle | title=Sea Turtle | Species | WWF }}

• Subfamily Carettinae
• Genus Caretta
• Loggerhead sea turtle (Caretta caretta){{sfn|Rhodin|Iverson|Bour|Fritz|2021|p={{pn|date=May 2025}}}}
• Genus Lepidochelys
• Kemp's ridley sea turtle (Lepidochelys kempii){{sfn|Rhodin|Iverson|Bour|Fritz|2021|p={{pn|date=May 2025}}}}
• Olive ridley sea turtle (Lepidochelys olivacea){{sfn|Rhodin|Iverson|Bour|Fritz|2021|p={{pn|date=May 2025}}}}
• Subfamily Cheloniinae
• Genus Chelonia
• Green sea turtle (Chelonia mydas){{sfn|Rhodin|Iverson|Bour|Fritz|2021|p={{pn|date=May 2025}}}}
• Genus Eretmochelys
• Hawksbill sea turtle (Eretmochelys imbricata){{sfn|Rhodin|Iverson|Bour|Fritz|2021|p={{pn|date=May 2025}}}}
• Genus Natator
• Flatback sea turtle (Natator depressus){{sfn|Rhodin|Iverson|Bour|Fritz|2021|p={{pn|date=May 2025}}}} (previously in Chelonia)

Below is a cladogram showing the phylogenetic relationships of living and extinct sea turtles in the family Cheloniidae based on Lynch and Parham (2003){{cite journal |last=Lynch |first=S.C. |author2=Parham, J.F. |year=2003 |title=The first report of hard-shelled sea turtles (Cheloniidae sensu lato) from the Miocene of California, including a new species (Euclastes hutchisoni) with unusually plesiomorphic characters |journal=PaleoBios |volume=23 |issue=3 |pages=21–35 }} and Parham and Pyenson (2010).{{cite journal |last1=Parham |first1=James F. |last2=Pyenson |first2=Nicholas D. |title=New sea turtle from the Miocene of Peru and the iterative evolution of feeding ecomorphologies since the Cretaceous |journal=Journal of Paleontology |date=March 2010 |volume=84 |issue=2 |pages=231–247 |doi=10.1666/09-077R.1 |bibcode=2010JPal...84..231P }}

{{clade| style=font-size:85%;line-height:95%; width:800px;

|label1=Pancheloniidae (=Cheloniidae sensu lato)

|1={{clade

|1=†Toxochelys

|2={{clade

|1=†Mexichelys

|2={{clade

|1=†Lophochleyinae

|2={{clade

|1=†Euclastes

|2={{clade

|1=†Argillochelys

|2=†Eochelone

|3={{clade

|1={{clade

|1=†Erquelinnesia

|2=†Pacifichelys}}

|2={{clade

|1=†Puppigerus

|label2=Cheloniidae(sensu stricto)

|2={{clade

|1=†Syllomus

|2={{clade

|1=†Procolpochelys

|2={{clade

|1=Chelonia mydas 70 px

|2=Natator depressus}}

|3={{clade

|1=Eretmochelys imbricata 70 px

|label2=Carettini

|2={{clade

|label1=Lepidochelys

|1={{clade

|1=Lepidochelys kempii

|2=Lepidochelys olivacea}}

|2=Caretta caretta

}} }} }} }} }} }} }} }} }} }} }} }}

• Genus †Allopleuron
• Genus †Argillochelys{{citation needed|date=May 2012}}
• Genus †Cabindachelys{{cite journal |last1=Myers |first1=Timothy S. |last2=Polcyn |first2=Michael J. |last3=Mateus |first3=Octávio |last4=Vineyard |first4=Diana P. |last5=Gonçalves |first5=António Olímpio |last6=Jacobs |first6=Louis L. |title=A new durophagous stem cheloniid turtle from the lower Paleocene of Cabinda, Angola |journal=Papers in Palaeontology |date=May 2018 |volume=4 |issue=2 |pages=161–176 |doi=10.1002/spp2.1100 |bibcode=2018PPal....4..161M }}
• Genus †Carolinochelys{{citation needed|date=May 2012}}
• Genus †Catapleura
• Genus †Erquelinnesia
• Genus †Gigantatypus{{cite journal |last1=Kaddumi |first1=H. F. |title=A new genus and species of gigantic marine turtles (chelonioidea: cheloniidae) from the Maastrichtian of the Harrana Fauna–Jordan |journal=PalArch's Journal of Vertebrate Palaeontology |date=2006 |volume=3 |issue=1 |url=https://doc.rero.ch/record/16350 }}
• Genus †Glyptochelone
• Genus †Itilochelys{{Cite journal|last1=Danilov |first1=I.G. |last2=Averianov |first2=A.O |last3=Yarkov |first3=A.A. |year=2010|title=Itilochelys rasstrigin gen. et sp. nov., a new hard-shelled sea turtle (Cheloniidae sensu lato) from the Lower Palaeocene of Volgograd Province, Russia |journal=Proceedings of the Zoological Institute RAS| volume=314 |issue=1 |pages=24–41 |doi=10.31610/trudyzin/2010.314.1.24 }}
• Genus †Lytoloma
• Genus †Osteopygis
• Genus †Pampaemys
• Genus †Peritresius
• Genus †Porthochelys
• Genus †Prionochelys
• Genus †Procolpochelys{{citation needed|date=May 2012}}
• Genus †Retechelys
• Genus †Syllomus
• Genus †Tasbacka
• Genus †Thinochelys
• Genus †Miocaretta

{{update|section|date=October 2019}}

{{Reflist}}

• {{cite book |doi=10.3854/crm.8.checklist.atlas.v9.2021 |title=Turtles of the World: Annotated Checklist and Atlas of Taxonomy, Synonymy, Distribution, and Conservation Status |edition=9th |series=Chelonian Research Monographs |date=2021 |volume=8 |isbn=978-0-9910368-3-7 |first1=Anders G.J. |last1=Rhodin |first2=John B. |last2=Iverson |first3=Roger |last3=Bour |first4=Uwe |last4=Fritz |first5=Arthur |last5=Georges |first6=H. Bradley |last6=Shaffer |first7=Peter Paul |last7=van Dijk |doi-access=free }}

• Skaphandrus.com [https://archive.today/20130216201139/http://skaphandrus.com/en/marine_species/family/Cheloniidae Cheloniidae]

{{Cheloniidae}}

{{Taxonbar|from=Q30143}}

{{Authority control}}

Category:Taxa named by Nicolaus Michael Oppel

Category:Turtle families

Category:Extant Paleocene first appearances