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Cryptodira – 11 families, 74 genera, over 200 species
Family[1]	Genera[2]
Carettochelyidae Boulenger, 1887 (1 genus)	Genus Carettochelys Ramsay , 1886 – one species Common name Scientific name IUCN Red List Status Range Picture Pig-nosed turtle C. insculpta Ramsay, 1886 VU IUCN Southern New Guinea and northern Northern Territory
Cheloniidae (sea turtles) Oppel, 1811 (5 genera)	Genus Caretta Rafinesque , 1814 – one species Common name Scientific name IUCN Red List Status Range Picture Loggerhead sea turtle C. caretta Linnaeus, 1758 VU IUCN Genus Lepidochelys (Ridley sea turtles) Fitzinger , 1843 – two species Common name Scientific name IUCN Red List Status Range Picture Kemp's ridley sea turtle L. kempii Garman, 1880 CR IUCN Olive ridley sea turtle L. olivacea von Eschscholtz, 1829 VU IUCN Genus Chelonia Brongniart , 1800 – one species Common name Scientific name IUCN Red List Status Range Picture Green sea turtle C. mydas Linnaeus, 1758 EN IUCN Genus Eretmochelys Fitzinger , 1843 – one species Common name Scientific name IUCN Red List Status Range Picture Hawksbill sea turtle E. imbricata Linnaeus, 1758 CR IUCN Genus Natator McCulloch , 1908 – one species Common name Scientific name IUCN Red List Status Range Picture Flatback sea turtle N. depressus Garman, 1880 DD IUCN
Chelydridae Gray, 1831(2 genera)	Genus Chelydra (snapping turtles) Schweigger, 1812 – three species Common name Scientific name IUCN Red List Status Range Picture Common snapping turtle C. serpentina Linnaeus, 1758 LC IUCN Central American snapping turtle C. rossignonii Bocourt, 1868 VU IUCN Southeastern Mexico, southern Belize, central Guatemala, and northwestern Honduras
Dermatemydidae Gray, 1870 (1 genus)	Genus Dermatemys Gray , 1847 – one species Common name Scientific name IUCN Red List Status Range Picture Central American river turtle D. mawii Gray, 1847 CR IUCN Eastern Mexico, Guatemala, Honduras, and Belize
Dermochelyidae Fitzinger, 1843 (1 genus)	Genus Dermochelys de Blainville , 1816 – one species Common name Scientific name IUCN Red List Status Range Picture Leatherback sea turtle D. coriacea Vandelli, 1761 VU IUCN
Rafinesque , 1815 (12 genera)	Genus Clemmys von Ritgen, 1828 – one species Common name Scientific name IUCN Red List Status Range Picture Spotted turtle C. guttata Schneider, 1792 EN IUCN Great Lakes region Genus Emys Duméril, 1805 – two species Common name Scientific name IUCN Red List Status Range Picture European pond turtle E. orbicularis Linnaeus, 1758 EN IUCN Sicilian pond turtle E. trinacris Fritz, Fattizzo, Guicking, Tripepi, Pennisi, Lenk, Joger and Wink, 2005 DD IUCN Genus Emydoidea Holbrook , 1838 – one species Common name Scientific name IUCN Red List Status Range Picture Blanding's turtle E. blandingii Holbrook, 1838 EN IUCN Genus Actinemys Baird and Girard, 1852 – one species Common name Scientific name IUCN Red List Status Range Picture Western pond turtle A. marmorata Baird and Girard, 1852 VU IUCN Genus Glyptemys Agassiz, 1857 – two species Common name Scientific name IUCN Red List Status Range Picture Bog turtle G. muhlenbergii Schoepff, 1801 CR IUCN Wood turtle G. insculpta Le Conte, 1830 EN IUCN Genus Terrapene (box turtles) Merrem , 1820 – four species Common name Scientific name IUCN Red List Status Range Picture Common box turtle T. carolina Linnaeus, 1758 VU IUCN Eastern coast of North America, and the Gulf of Mexico Eastern box turtle T. c. carolina Florida box turtle T. c. bauri Gulf Coast box turtle T. c. major Three-toed box turtle T. c. triunguis Mexican box turtle T. c. mexicana Yucatán box turtle T. c. yucatana Coahuilan box turtle T. coahuila Schmidt and Owens, 1944 EN IUCN Cuatro Ciénegas, Coahuila, Mexico Spotted box turtle T. nelsoni Stejneger, 1925 DD IUCN Sierra Madre Occidental, Mexico Terrapene ornata] Terrapene ornata Agassiz, 1857 NT IUCN Central United States, including the Mojave desert and the Midwest region Ornate box turtle left, Desert box turtle right Genus Chrysemys Gray, 1844 – one species Common name Scientific name IUCN Red List Status Range Picture Painted turtle C. picta Schneider, 1783 LC IUCN Eastern painted turtle C. p. picta Midland painted turtle C. p. marginata Southern painted turtle C. p. dorsalis Western painted turtle C. p. bellii
Geoemydidae Theobald, 1868	24
Kinosternidae Agassiz, 1857	4
Platysternidae Gray , 1869	1
Testudinidae Batsch , 1788	12
Trionychidae Fitzinger, 1826	14
Pleurodira – 3 families, 16 genera, over 60 species
Family	Genera
Chelidae Gray, 1831	15
Pelomedusidae Cope, 1868	2
Podocnemididae Gray, 1869	3

References

Further reading

• David T. Kirkpatrick (November–December 1995). "Platysternon megacephalum". Reptile & Amphibian Magazine. pp. 40–47. Retrieved 26 June 2010.
• Cogger, H.G.; R.G. Zweifel; D. Kirschner (2004). Encyclopedia of Reptiles & Amphibians Second Edition. Fog City Press.
  ISBN 1-877019-69-0
  .

• John B. Iverson; A. Jon Kimerling; A. Ross Kiester. "EMYSystems". Terra Cognita Laboratory, Geosciences Department of Oregon State University. Retrieved 26 June 2010.

Cetacean anatomy is the study of the form or

Unlike toothed whales (left), baleen whales (right) do not have a melon

The skull of all cetaceans is extended, which can be clearly seen in baleen whales. The nostrils are located on top of the head above the eyes. The back of the skull is significantly shortened and deformed. By shifting the nostrils to the top of the head, the nasal passages extend perpendicularly through the skull. The teeth or baleen in the upper jaw sit exclusively on the

The jaws of toothed whales are designed for catching swift prey. Porpoises have spade-shaped teeth, but dolphins have conical teeth. Cetaceans are monophydonts, meaning they have one set of teeth their entire life.^[4] Toothed whales use their jaw to recieve pulses for echolocation. Echoes are received using complex fatty structures around the lower jaw as the primary reception path, from where they are transmitted to the middle ear via a continuous fat body.^[5] Lateral sound may be received though fatty lobes surrounding the ears with a similar density to water. Some researchers believe that when they approach the object of interest, they protect themselves against the louder echo by quieting the emitted sound. This is known to happen in bats, but here the hearing sensitivity is also reduced close to a target.^[6]

As opposed to toothed whales, baleen whales have different jaw designs depending on their feeding behaviour. Lunge-feeders, like rorquals, have to expand their jaw to a volume that can be bigger than the whale itself; to do this, the

Beaked whales have a somewhat similar jaw anatomy as rorquals. The throats of beaked whales have a bilaterally paired set of grooves that are associated with their unique feeding mechanism, suction feeding. Instead of capturing prey with their teeth, beaked whales suck it into their oral cavity. Suction is aided by the throat grooves, which stretch and expand to accommodate food. Their tongue can move very freely. By suddenly retracting the tongue and distending the gular (throat) floor, pressure immediately drops within the mouth sucking the prey in with the water.^[11]

Eyes The whale eye is relatively small for its size, yet they do retain a good degree of eyesight. As well as this, the eyes of a whale are placed on the sides of its head, so their vision consists of two fields, rather than a binocular view like humans have. When belugas surface, their lens and cornea correct the nearsightedness that results from the refraction of light; they contain both rod and cone cells, meaning they can see in both dim and bright light, but they have far more rod cells than they do cone cells. Whales do, however, lack short wavelength sensitive visual pigments in their cone cells indicating a more limited capacity for colour vision than most mammals.^[12] Most whales have slightly flattened eyeballs, enlarged pupils (which shrink as they surface to prevent damage), slightly flattened corneas and a tapetum lucidum; these adaptations allow for large amounts of light to pass through the eye and, therefore, a very clear image of the surrounding area. In water, a whale can see around 10.7 metres (35 ft) ahead of itself, but, of course, they have a smaller range above water. They also have glands on the eyelids and outer corneal layer that act as protection for the cornea.^[13] Toothed whales can retract and protrude its eyes thanks to a 2-cm-thick retractor muscle attached around the eye at the equator.^[14]

Blowhole

The blowhole is the hole at the top of a whale's head through which the animal breathes air. When a whale reaches the water surface to breathe, they will forcefully expel air through the blowhole. Mucus and carbon dioxide from the animal's metabolism, which have been stored in the whale while diving, are also expelled. The exhalation is released into the comparably lower-pressure and colder atmosphere, so any

Kidneys Whale kidneys are specially designed for excreting excess salt content. Water is typically gained by the food they eat, however, the invertebrates they consume have the same salt content as seawater. As in other vertebrates, whale salt levels are three times less than that of seawater. However, the kidneys are inefficient at retaining water, and expel much of it while excreting salt.[16]

Spleen Liver The liver in whales is bilobed, as opposed to the five-lobed liver in humans, and they lack a

• La peinture de l'Embryon d'un Marsouins (Painting of the embryo of a Porpoise) - from The natural history of marine fish to strange with real peincture & description Daulphin, and several others of his species observed by Pierre Belon du Mans.

Nervous system Central nervous system Cerebellum Identified neurons Immune system

See also

References