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| Turtle Temporal range: Triassic - Recent | |
|---|---|
| |
| "Chelonia" from Ernst Haeckel's Kunstformen der Natur, 1904 | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Sauropsida |
| Order: | Testudines Linnaeus, 1758 See text for families. |
Turtles are reptilians of the Order Testudines (all living turtles belong to the crown group Chelonia), most of whose body is shielded by a special bony or cartilaginous shell developed from their ribs. The Order Testudines includes both extant (living) and extinct species. The earliest known turtles date from 215 million years ago, making turtles one of the oldest reptile groups and a more ancient group than lizards and snakes. About 300 species are alive today, and some are highly endangered.
Turtles cannot breathe in water however the hold their breath for various periods of time.
Like other reptiles, turtles are poikilothermic (or "of varying temperature"). Like other amniotes (reptiles, dinosaurs, birds, and mammals), they breathe air and don't lay eggs underwater, although many species live in or around water. The largest turtles are aquatic.
(670 lb).
The largest ever chelonian was Archelon ischyros, a Late Cretaceous sea turtle known to have been up to 4.6 m (15 ft) long.
The smallest turtle is the speckled padloper tortoise of South Africa. It measures no more than 8 cm (3 in) in length and weighs about 140 g (5 oz). Two other species of small turtles are the American mud turtles and musk turtles that live in an area that ranges from Canada to South America. The shell length of many species in this group is less than 13 cm (5 in) in length.
Evolutionary history
The first turtles are believed to have existed in the early Triassic Period of the Mesozoic era, about 200 million years ago. 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 procolophonoids, 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.
However, it was recently suggested that the anapsid-like turtle skull may be due to reversion rather than to anapsid descent. More recent phylogenetic studies with this in mind placed turtles firmly within diapsids, slightly closer to Squamata than to Archosauria. All molecular studies have strongly upheld this new phylogeny, though some place turtles closer to Archosauria. Re-analysis 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 turtle is 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, presumably, only parallel evolution).
Turtle, tortoise or terrapin?
Differences between turtles, tortoises and terrapins
Turtles as pets
Main article: Pet turtlesTurtles, particularly small terrestrial and freshwater turtles, are commonly kept as pets. Among the most popular are Russian Tortoises, Greek spur-thighed tortoises and red-ear sliders (or terrapin).
See also
- Addyaita: a giant turtle of Aldabra. It was reportedly 250-years old when it died at Kolkata Zoo on March 24, 2005.
- Araripemys arturi
- List of Testudines families
- Pet turtles
- Red-eared slider: most common pet turtle
- Sea Turtles
- Turtle racing
- Turtles and tortoises in popular culture
Further reading
- Iskandar, DT (2000). Turtles and Crocodiles of Insular Southeast Asia and New Guinea. ITB, Bandung.
- Pritchard, Pether C H (1979). Encyclopedia of Turtles. T.F.H. Publications.
References
- http://www.enchantedlearning.com/subjects/dinosaurs/dinos/Archelon.shtml
- Reptile blood isn't necessarily cold, as reptiles sun themselves and take other measures to stay warm.
- http://www.tortoise.org/general/wildfaqs.html#largest
- http://www.oceansofkansas.com/Turtles.html
- http://www.ucmp.berkeley.edu/anapsids/procolophonoidea.html
- Rieppel, O., and DeBraga, M. (1996). "Turtles as diapsid reptiles." Nature, 384: 453-455.
- Zardoya, R., and Meyer, A. (1998). "Complete mitochondrial genome suggests diapsid affinities of turtles." Proceedings of the National Academy of Sciences of the United States of America, 95(24): 14226-14231.
- http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=538573
- David Alderton (1986). An Interpret Guide to Reptiles & Amphibians, Salamander Books Ltd., London & New York.