Systematics and evolution
Main article: List of Testudines families
"Chelonia" (Testudines) from Ernst Haeckel's Kunstformen der Natur, 1904The first proto-turtles are believed to have existed in the early Triassic Period of the Mesozoic era, about 220 million years ago, and their shell, which has remained a remarkably stable body plan, is thought to have evolved from bony extensions of their backbones and broad ribs that expanded and grew together to form a complete shell that offered protection at every stage of its evolution, even when the bony component of the shell was not complete. This is supported by fossils of the freshwater Odontochelys semitestacea, the "half-shelled turtle with teeth", have been found near Guangling in south-west China, which displays a complete bony plastron and an incomplete carapace, similar to an early stage of turtle embryonic development.[6] Prior to this discovery, the earliest fossil turtles were terrestrial and had a complete shell, offering no clue to the evolution of this remarkable anatomical feature. By the late Jurassic, turtles had radiated widely, and their fossil history becomes easier to read.
Their exact ancestry is disputed. It was believed that they are the only surviving branch of the ancient clade Anapsida, which includes groups such as procolophonids, millerettids, protorothyrids, and pareiasaurs. All anapsid skulls lack a temporal opening, while all other extant amniotes have temporal openings (although in mammals the hole has become the zygomatic arch). The millerettids, protorothyrids, and pareiasaurs became extinct in the late Permian period, and the procolophonoids during the Triassic.[7]
However, it was recently suggested that the anapsid-like turtle skull may be due to reversion rather than to anapsid descent. More recent morphological phylogenetic studies with this in mind placed turtles firmly within diapsids, slightly closer to Squamata than to Archosauria.[8] All molecular studies have strongly upheld the placement of turtles within diapsids, though some place turtles closer to Archosauria than Squamata.[9] Reanalysis of prior phylogenies suggests that they classified turtles as anapsids both because they assumed this classification (most of them studying what sort of anapsid turtles are) and because they did not sample fossil and extant taxa broadly enough for constructing the cladogram. As of 2003, the consensus is that Testudines diverged from other diapsids between 200 and 279 million years ago.
The earliest known fully-shelled turtle is the late-Triassic Proganochelys, though this species already had many advanced turtle traits, and thus probably had many millions of years of preceding turtle evolution and species in its ancestry. It did lack the ability to pull its head into its shell (and it had a long neck), and had a long, spiked tail ending in a club, implying an ancestry occupying a similar niche to the ankylosaurs (though only through parallel evolution).
Turtles are divided into three suborders, one of which, the Paracryptodira, is extinct. The two extant suborders are the Cryptodira and the Pleurodira. The Cryptodira is the larger of the two groups and includes all the marine turtles, the terrestrial tortoises, and many of the freshwater turtles. The Pleurodira are sometimes known as the side-necked turtles, a reference to the way they withdraw their heads into their shells. This smaller group consists primarily of various freshwater turtles.
Basal and incertae sedis chelonians
Genus †Australochelys (Chelonia incertae sedis)
Genus †Murrhardtia (Chelonia incertae sedis)
Genus †Palaeochersis (Chelonia incertae sedis)
Genus †Chinlechelys (Proganochelydia or basal Testudines)
Genus †Chelycarapookus (Testudines incertae sedis)
Genus †Chitracephalus (Testudines incertae sedis)
Genus †Neusticemys (Testudines incertae sedis)
Genus †Scutemys (Testudines incertae sedis)
Suborder †Proganochelydia
Genus †Odontochelys (tentatively placed here)
Genus †Proganochelys
Fossil of Proganochelys quenstedti, one of the oldest true turtles presently known.
Unlike modern Testudines, Proganochelys was not able to hide its head under the shell.Suborder Cryptodira
Basal genera
Genus †Kayentachelys
Genus †Indochelys
Infraorder †Paracryptodira
Basal and incertae sedis
Family †Kallokibotiidae
Family †Mongolochelyidae
Family †Pleurosternidae
Family †Solemydidae
Superfamily †Baenoidea
Family †Baenidae
Family †Macrobaenidae
Family †Neurankylidae
Infraorder Eucryptodira
Basal and incertae sedis
†"Sinemys" wuerhoensis
Genus †Chubutemys (Meiolaniidae?)
Genus †Hangaiemys (Macrobaenidae?)
Genus †Judithemys
Genus †Osteopygis
Genus †Planetochelys
Family Chelydridae (snapping turtles)
Family †Eurysternidae
Family †Macrobaenidae
Family †Meiolaniidae (horned turtles)
Family †Plesiochelyidae
Family †Sinemydidae
Family †Xinjiangchelyidae
Superfamily Chelonioidea (sea turtles)
Family †Protostegidae
Family †Thalassemyidae
Family †Toxochelyidae
The Western Hermann's Tortoise (Testudo hermanni hermanni) is a cryptodire.
Cryptodires hide their head inwards.Family Cheloniidae (green sea turtles and relatives)
Family Dermochelyidae (leatherback turtles)
Superfamily Testudinoidea
Family †Haichemydidae
Family †Lindholmemydidae
Family †Sinochelyidae
Family Platysternidae (big-headed turtle)
Family Emydidae (pond, box and water turtles)
Family Geoemydidae (Asian river turtles, Asian leaf turtles, Asian box turtles and roofed turtles)
Family Testudinidae (tortoises)
Superfamily Trionychoidea
Family †Adocidae
Family Carettochelyidae (pignose turtles)
Family Dermatemydidae (river turtles)
Family Kinosternidae (mud turtles)
The African Helmeted Turtle (Pelomedusa subrufa) is a pleurodire.
Pleurodires hide their head sideways.
Family Trionychidae (softshell turtles)
Suborder Pleurodira
Basal and incertae sedis
Family †Araripemydidae
Family †Proterochersidae
Family Chelidae (Austro-American sideneck turtles)
Superfamily Pelomedusoidea
Family †Bothremydidae
Family Pelomedusidae (African sideneck turtles)
Family Podocnemididae (Madagascan big-headed and American sideneck river turtles)
Turtle, tortoise, or terrapin?
Different animals are called turtles, tortoises, or terrapins in different varieties of EnglishAlthough the word turtle is widely used to describe all members of the order Testudines, it is also common to see certain members described as terrapins, tortoises or sea turtles as well. Precisely how these alternative names are used, if at all, depends on the type of English being used.
British English normally describes these reptiles as turtles if they live in the sea; terrapins if they live in fresh or brackish water; or tortoises if they live on land. However, there are exceptions to this where American or Australian common names are in wide use, as with the Fly River turtle.
American English tends to use the word turtle for all freshwater species, as well as for certain land-dwelling species (e.g. box turtles). Oceanic species are usually referred to as sea turtles, and tortoise is restricted to members of the true tortoise family, Testudinidae. The name terrapin is typically reserved only for the brackish water diamondback terrapin, Malaclemys terrapin; the word terrapin being derived from the Algonquian word for this animal.[10]
Australian English uses turtle for both the marine and freshwater species but tortoise for the terrestrial species.
To avoid confusion, the word chelonian is popular among veterinarians, scientists, and conservationists working with these animals as a catch-all name for any member of the superorder Chelonia which includes all turtles, tortoises and terrapins living and extinct, as well as their immediate ancestors. It is based on the Ancient Greek word χελώνη, chelōnē; Modern Greek χελώνα, chelōna; meaning turtle/tortoise.
As pets
Wikibooks has a book on the topic of
Keeping Pet Turtles
Turtles, particularly small terrestrial and freshwater turtles, are commonly kept as pets. Among the most popular are Russian Tortoises, Spur-thighed Tortoises, and Red-eared sliders (or Red-eared terrapin).[11]
In the United States, due to the ease of contracting salmonella through casual contact with turtles, the U.S. Food and Drug Administration (FDA) established a regulation in 1975 to discontinue the sale of turtles under 4 inches. It is illegal in every state in the U.S. for anyone to sell any turtles under 4 inches long. Many stores and flea markets still sell small turtles due to a loophole in the FDA regulation which allows turtles under 4 inches to be sold for educational purposes.[12][13]
Some states have other laws and regulations regarding possession of Red-eared Sliders (abbreviated as RES) as pets because they are looked upon as invasive species or pests where they are not native but have been introduced through the pet trade. As of July 1, 2007 it is illegal in Florida to sell any wild type RES. Unusual color varieties such as albino and pastel RES, which are derived from captive breeding, are still allowed for sale.[14]
As food
The window of a restaurant serving guilinggao, decorated with a 龜 ('turtle') characterThe flesh of turtles was, and still is, considered a delicacy in a number of cultures. Turtle soup has been a prized dish in Anglo-American cuisine, and still remains so in some parts of the Far East.
Turtles remain a part of the traditional diet on the island of Grand Cayman, so much so that when wild stocks became depleted, a turtle farm was established specifically to raise sea turtles for their meat. The farm also releases specimens to the wild as part of an effort to repopulate the Carribbean sea.[1]
Guilinggao jelly was a Chinese medicine preparation containing powdered shell of a certain turtle species; these days, though, it is typically made with only herbal ingredients.
Harvesting wild turtles is legal in Florida, and a single seafood company in Fort Lauderdale was reported (200 cool as buying about 5,000 pounds of softshell turtles a week. The harvesters (hunters) are paid about $2 a pound; some manage to catch as many as 30-40 turtles (500 pounds) on a good day. Some of the catch gets to the local restaurants, while most of it is exported to the Far East; Florida Fish and Wildlife Conservation Commission estimates (200 cool that around 3,000 pounds of softshell turtles are exported each week via Tampa International Airport.[15]
Gallery
Closeup head-on view of a common snapping turtle (Chelydra serpentina), taken near the St. Lawrence River in northern New York State
Turtle in the backyard of a Florida Resident.
In culture
Main article: Cultural depictions of turtles and tortoises
See also
Adwaita: a giant turtle that was reportedly 250 years old when it died in 2006
Araripemys arturi
Little Turtle - chief of the Miami Tribe
Turtle racing
Further reading
Iskandar, DT (2000). Turtles and Crocodiles of Insular Southeast Asia and New Guinea. Bandung: Palmedia – ITB.
Pritchard, Peter Charles Howard (1979). Encyclopedia of turtles. Neptune, NJ: T.F.H. Publications. ISBN 0-87666-918-6.
References
^ "Archelon-Enchanted Learning Software". Enchantedlearning.com. http://www.enchantedlearning.com/subjects/dinosaurs/dinos/Archelon.shtml. Retrieved 2009-03-14.
^ Michael J. Connor. "CTTC's Turtle Trivia". Tortoise.org. http://www.tortoise.org/general/wildfaqs.html#largest. Retrieved 2009-03-14.
^ "Marine Turtles". Oceansofkansas.com. http://www.oceansofkansas.com/Turtles.html. Retrieved 2009-03-14.
^ "Anatomy and Diseases of the Shells of Turtles and Tortoises". Peteducation.com. http://www.peteducation.com/article.cfm?articleid=2700. Retrieved 2009-03-14.
^ All but Ageless, Turtles Face Their Biggest Threat: Humans
^ Li C, Wu XC, Rieppel O, Wang LT, Zhao LJ (November 200 cool . "An ancestral turtle from the Late Triassic of southwestern China". Nature 456 (7221): 497–501. doi:10.1038/nature07533. PMID 19037315.
^ "Introduction to Procolophonoidea". Ucmp.berkeley.edu. http://www.ucmp.berkeley.edu/anapsids/procolophonoidea.html. Retrieved 2009-03-14.
^ Rieppel O, DeBraga M (1996). "Turtles as diapsid reptiles". Nature 384: 453–5. doi:10.1038/384453a0.
^ Zardoya R, Meyer A (November 199 cool . "Complete mitochondrial genome suggests diapsid affinities of turtles". Proc. Natl. Acad. Sci. U.S.A. 95 (24): 14226–31. doi:10.1073/pnas.95.24.14226. PMID 9826682. PMC: 24355. http://www.pnas.org/cgi/pmidlookup?view=long&pmid=9826682.
^ http://www.bartleby.com/61/1/T0120100.html
^ David Alderton (1986). An Interpret Guide to Reptiles & Amphibians, Salamander Books Ltd., London & New York.
^ GCTTS FAQ: "4 Inch Law", actually an FDA regulation
^ Turtles intrastate and interstate requirements; FDA Regulation, Sec. 1240.62, page 678 part d1.
^ Turtle ban begins today; New state law, newszap.com, 2007-07-01. Retrieved 2007-07-06.
^ "China Gobbling Up Florida Turtles", By Craig Pittman, St. Petersburg Times. Published: Thursday, October 9, 2008
External links
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Testudines
UC Berkeley Museum of Paleontology
Chelonian studbook Collection and display of the weights/sizes of captive turtles
Biogeography and Phylogeny of the Chelonia (taxonomy, maps)
The word 'turtle' in different languages
New Scientist article (including video) on how the turtle evolved its shell
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