There are fourteen extant families of the

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...

Testudines, an order of

reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates ( lizards and snakes) and rhynchocephalia ...

. The testudines are some of the most ancient reptiles alive, with only the

tuatara Tuatara (''Sphenodon punctatus'') are reptiles endemic to New Zealand. Despite their close resemblance to lizards, they are part of a distinct lineage, the order Rhynchocephalia. The name ''tuatara'' is derived from the Māori language and m ...

s considered more primitive. There are approximately 300

extant species Neontology is a part of biology that, in contrast to paleontology, deals with living (or, more generally, ''recent'') organisms. It is the study of extant taxa (singular: extant taxon): taxa (such as species, genera and families) with members sti ...

and 97

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

of testudines, split into two suborders: the

Cryptodira The Cryptodira ('' el, hidden neck'') are a suborder of Testudines that includes most living tortoises and turtles. Cryptodira differ from Pleurodira (side-necked turtles) in that they lower their necks and pull the heads straight back into the ...

ns and the

Pleurodira The Pleurodira are one of the two living suborders of turtles, 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 differen ...

ns. The distinction between these two suborders is based on the mode in which they cover their head and neck. The Pleurodirans, also called the side-necked turtles, have long necks, and fold them sideways to align them with the shell. The

Pelomedusidae :''Alternatively, "Pelomedusidae" may refer to the Pelomedusoidea. See below for details.'' Pelomedusidae is a family of freshwater turtles endemic to sub-Saharan Africa, including Madagascar, São Tomé, and the Seychelles(Although this pop. ma ...

and

Chelidae Chelidae 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 Ame ...

are the only extant families of pleurodires. The Cryptodirans pull their neck straight back to conceal their head within the shell. The

Carettochelyidae Carettochelyidae is a family of cryptodiran turtles belonging to the Trionychia. It contains only a single living species, the pig-nosed turtle (''Carettochelys insculpta'') native to New Guinea and Northern Australia. Stem-group carettochelyid ...

Cheloniidae 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. They are the only sea turtles t ...

Chelydridae The Chelydridae is a family of turtles that has seven extinct and two extant genera. The extant genera are the snapping turtles, ''Chelydra'' and ''Macrochelys''. Both are endemic to the Western Hemisphere. The extinct genera are ''Acherontemys' ...

Dermatemydidae The Dermatemydidae are a family of turtle Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side ne ...

Dermochelyidae Dermochelyidae is a family of turtles which has seven extinct genera and one extant genus, including the largest living sea turtles. Classification of known genera The following list of dermochelyid species was published by Hirayama and Tong i ...

Emydidae Emydidae (Latin ''emys'' (freshwater tortoise) + Ancient Greek εἶδος (''eîdos'', “appearance, resemblance”)) is a family of testudines (turtles) that includes close to 50 species in 10 genera. Members of this family are commonly calle ...

Kinosternidae The Kinosternidae are a family of mostly small turtles that includes the mud turtles and musk turtles. The family contains 25 species within four genera, but taxonomic reclassification is an ongoing process, so many sources vary on the exact num ...

, Testudinidae and

Trionychidae The Trionychidae are a taxonomic family of a number of turtle genera, commonly known as softshell turtles. The family was erected by Leopold Fitzinger in 1826. Softshells include some of the world's largest freshwater turtles, though many can a ...

are all cryptodires, although the ability to retract the head has been lost in the sea turtles (Cheloniidae and Dermochelyidae). A third order, the

Paracryptodira __NOTOC__ Paracryptodira is an extinct group of reptiles in the clade Testudinata (which contains modern turtles and their extinct relatives), known from the Jurassic to Paleogene of North America and Europe. Initially treated as a suborder sist ...

ns, are extinct. Reptiles are classified according to the pattern of fenestration in the temporal region of the

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, th ...

. Testudines are placed in the subclass

Anapsida An anapsid is an amniote whose skull lacks one or more skull openings (fenestra, or fossae) near the temples. Traditionally, the Anapsida are the most primitive subclass of amniotes, the ancestral stock from which Synapsida and Diapsida evolved ...

because they lack fenestration. There are suggestions that this lack of fenestration is a secondary characteristic and that turtles belong in

Diapsida Diapsids ("two arches") are a clade of sauropsids, distinguished from more primitive eureptiles by the presence of two holes, known as temporal fenestrae, in each side of their skulls. The group first appeared about three hundred million years ag ...

. Both sides cite strong evidence, and the conflict has yet to be resolved. The shell of testudines distinguishes them from other vertebrates. The shell is not an

exoskeleton An exoskeleton (from Greek ''éxō'' "outer" and ''skeletós'' "skeleton") is an external skeleton that supports and protects an animal's body, in contrast to an internal skeleton ( endoskeleton) in for example, a human. In usage, some of the ...

, but a modified

ribcage The rib cage, as an enclosure that comprises the ribs, vertebral column and sternum in the thorax of most vertebrates, protects vital organs such as the heart, lungs and great vessels. The sternum, together known as the thoracic cage, is a sem ...

and part of the

vertebral column The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord (a flexible rod of uniform composition) found in all chordate ...

. Because of the shell, the pectoral and pelvic girdles are located within the ribcage. The limb bones are also modified to accommodate to the shell. The earliest known turtles are from fossils in the

Upper Triassic The Late Triassic is the third and final epoch of the Triassic Period in the geologic time scale, spanning the time between Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch and followed by the Early Jurassic Epoch. ...

. These fossils are nearly indistinguishable from modern turtles anatomically. In these early fossils (mostly of the genus Proganochelys), the teeth have already been lost, and a

keratin Keratin () is one of a family of structural fibrous proteins also known as ''scleroproteins''. Alpha-keratin (α-keratin) is a type of keratin found in vertebrates. It is the key structural material making up Scale (anatomy), scales, hair, Nail ...

beak is suggested by the

mandible In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

s. Important differences between Proganochelys and modern turtles are the presence of the palatal teeth (lost in modern species), the inability to retract the head within the shell, and the lack of a trochlear pulley in the jaw closing anatomy.

Families

The following lists the family—the Latin name of the family, date in which the species was formally described and classified, and the binomial authority on the species; the number of genera belonging to the family; the name or names commonly used; an example species and an example image. , - ,

Rafinesque Constantine Samuel Rafinesque-Schmaltz (; October 22, 1783September 18, 1840) was a French 19th-century polymath born near Constantinople in the Ottoman Empire and self-educated in France. He traveled as a young man in the United States, ultimat ...

, 1815, , 12, , Pond turtles, terrapins, and sliders, ,

Red-eared slider The red-eared slider or red-eared terrapin (''Trachemys scripta elegans'') is a subspecies of the pond slider (''Trachemys scripta''), a semiaquatic turtle belonging to the family Emydidae. It is the most popular pet turtle in the United States, ...

(''Trachemys scripta elegans''), , Tortoise1 cepolina

, - ,

Geoemydidae The Geoemydidae (formerly known as Bataguridae) are one of the largest and most diverse families in the order Testudines (turtles), with about 70 species. The family includes the Eurasian pond and river turtles and Neotropical wood turtles. Mem ...

Theobald Theobald is a Germanic dithematic name, composed from the elements '' theod-'' "people" and ''bald'' "bold". The name arrived in England with the Normans. The name occurs in many spelling variations, including Theudebald, Diepold, Theobalt, Tyb ...

, 1868, , 24, , Asian leaf turtles, roofed turtles, and Asian box turtles, ,

Amboina box turtle The Amboina box turtle or Southeast Asian box turtle (''Cuora amboinensis'') is a species of Asian box turtle. It is found in the Nicobar Islands, eastern India (Assam), Bangladesh, Myanmar, Thailand, Cambodia, Laos, central and southern Vietn ...

(''Cuora amboinensis''), , Cuora amboinensis kamaroma j

, - ,

Agassiz Jean Louis Rodolphe Agassiz ( ; ) FRS (For) FRSE (May 28, 1807 – December 14, 1873) was a Swiss-born American biologist and geologist who is recognized as a scholar of Earth's natural history. Spending his early life in Switzerland, he rec ...

, 1857, , 4, , Mud and musk turtles, ,

Common musk turtle ''Sternotherus odoratus'' is a species of small turtle in the family Kinosternidae. The species is native to southeastern Canada and much of the Eastern United States. It is also known commonly as the common musk turtle, eastern musk turtle, o ...

(''Sternotherus odoratus''), ,

, - , Platysternidae

Gray Grey (more common in British English) or gray (more common in American English) is an intermediate color between black and white. It is a neutral or achromatic color, meaning literally that it is "without color", because it can be compose ...

, 1869 , , 1, , Big-headed turtle, ,

Big-headed turtle The big-headed turtle (''Platysternon megacephalum'') is a species of turtle in the family Platysternidae from Southeast Asia and southern China. Background Previously considered a distinct family placed on occasion in " Kinosternoidea", i ...

(''Platysternon megacephalum''), , Zolw wielkoglowy

, - , Testudinidae

Batsch August Johann Georg Karl Batsch (28 October 1761 – 29 September 1802) was a German naturalist. He was a recognised authority on mushrooms, and also described new species of ferns, bryophytes, and seed plants. Life and career Batsch was born ...

, 1788, , 12, ,

Tortoises Tortoises () are reptiles of the family Testudinidae of the order Testudines (Latin: ''tortoise''). Like other turtles, tortoises have a turtle shell, shell to protect from predation and other threats. The shell in tortoises is generally hard, ...

, ,

Aldabra giant tortoise The Aldabra giant tortoise (''Aldabrachelys gigantea'') is a species of tortoise in the family Testudinidae. The species is endemic to the islands of the Aldabra Atoll in the Seychelles. It is one of the largest tortoises in the world.Pritch ...

(''Geochelone gigantea''), , Tortoise

, - ,

Fitzinger, 1826, , 14, , Softshell turtles, ,

Spiny softshell turtle The spiny softshell turtle (''Apalone spinifera'') is a species of softshell turtle, one of the largest freshwater turtle species in North America. Both the common name, spiny softshell, and the specific name, ''spinifera'' (spine-bearing), ref ...

(''Apalone spinifera''), ,

, - , colspan="5" align="center" bgcolor="#BBBBFF",

– 3 families, 16 genera, over 60 species , - !Family!!Genera!!Common names!!Example species!!Example image , - ,

, 1831 , , 15, , Austro-American sideneck turtles, ,

Common snakeneck turtle The eastern long-necked turtle (''Chelodina longicollis'')Kennett, R., Roe, J., Hodges, K., and Georges, A. 2009. ''Chelodina longicollis'' (Shaw 1784) – eastern long-necked turtle, common long-necked turtle, common snake-necked turtle. ''In'': ...

(''Chelodina longicollis''), , Eastern long neck tortoise - chelodina longicollis

, - ,

Cope The cope (known in Latin as ''pluviale'' 'rain coat' or ''cappa'' 'cape') is a liturgical vestment, more precisely a long mantle or cloak, open in front and fastened at the breast with a band or clasp. It may be of any liturgical colour. A c ...

, 1868 , , 2, , Afro-American sideneck turtles, ,

African helmeted turtle The African helmeted turtle (''Pelomedusa subrufa''), also known commonly as the marsh terrapin, the crocodile turtle, or in the pet trade as the African side-necked turtle, is a species of omnivorous side-necked terrapin in the family Pelomedus ...

(''Pelomedusa subrufa''), ,

, - ,

Podocnemididae Podocnemididae is a family of pleurodire (side-necked) turtles, once widely distributed. Most of its 20 genera and 30 species are now extinct. Seven of its eight surviving species are native to South America: the genus '' Peltocephalus'', with o ...

, 1869 , , 3, , Madagascar big-headed, big-headed Amazon River turtle and South American sideneck river turtles, , Madagascar big-headed turtle (''Erymnochelys madagascariensis''), ,

References

External links

* {{Featured list *

Testudines Turtles are an order of reptiles known as Testudines, characterized by a special shell developed mainly from their ribs. Modern turtles are divided into two major groups, the Pleurodira (side necked turtles) and Cryptodira (hidden necked t ...

Testudines families

Families

References

Further reading

External links