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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
A beakless turtle with a snout shaped like that of a pigs
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
World's oceans excluding the polar regions
A white turtle with a beak, black eye-spots, and a dark-brown carapace
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
The Gulf of Mexico and the eastern coast of the United States
A green turtle with a white underside and beak
Olive ridley sea turtle L. olivacea
von Eschscholtz, 1829
VU IUCN
Coasts of Oceania, South China Sea, Sea of Japan, the Indian Ocean, Africa (excluding the Mediterranean), and the Americas (excluding the eastern coast of North America and southern South America)
alt=A green turtle with a white underside and beak
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
Tropical and temperate oceans of the world
A dark brown turtle with a beak, a green carapace, and a white underside
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
Tropical and subtropical oceans of the world
A turtle with a beak, a black head, flippers, and carapace, a white neck and underside, and serrated scutes on the carapace
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
Around the coast of Australia, stretching to New Guinea and Java, excluding the southern coast
A grey turtle with a white beak
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
United States east of the Rocky Mountains
An orange-brown tortoise with a grey carapace
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
A green turtle with webbed feet
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
Oceans of the world
A large black turtle without a bony shell
Emydidae
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
A black tortoise with yellow speckles across the body and carapace
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
Mediterranean Europe, and around the Caspian Sea
A black tortoise with yellow speckles across the body and carapace
Sicilian pond turtle E. trinacris
Fritz, Fattizzo, Guicking, Tripepi, Pennisi, Lenk, Joger and Wink, 2005
DD IUCN
Sicily, an island off the coast of Italy
A grey tortoise
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
Great Lakes region in the United States
A black tortoise with yellow spots covering the body
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
Western coast of the contiguous United States
A dark brown turtle with webbed feet, and a yellow-speckled head and neck
Genus Glyptemys Agassiz, 1857 – two species
Common name Scientific name IUCN Red List Status Range Picture
Bog turtle G. muhlenbergii
Schoepff, 1801
CR IUCN
One population in New England and another population in Virginia, United States
A black turtle with an orange patch on its neck
Wood turtle G. insculpta
Le Conte, 1830
EN IUCN
New England, Newfoundland, and the Greats Lakes
A black tortoise with a yellow plastron and spots on the head and neck
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 A dark grey tortoise
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 Brown tortoises
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
United States spilling over into Canada excluding the Mojave desert
Eastern painted turtle
C. p. picta
Midland painted turtle
C. p. marginata
Southern painted turtle
C. p. dorsalis
Western painted turtle
C. p. bellii
A grey tortoise with square patterns on the carapace A brown tortoise A grey tortoise with a single thin, orange line running down the carapace from head to tail and white marks on the head and neck A grey tortoise with yellow stripes running down the neck from the head
Underside view, showing a tan plastron Underside view, showing a tan plastron Underside view, showing a tan plastron and webbed feet Underside view, the plastron is bright red with black and white Rorshach-like patterns
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

  1. ^ John B. Iverson; A. Jon Kimerling; A. Ross Kiester. "List of All Families". Terra Cognita Laboratory, Geosciences Department of Oregon State University. Retrieved 26 June 2010.
  2. ^ John B. Iverson; A. Jon Kimerling; A. Ross Kiester. "List of Genera". Terra Cognita Laboratory, Geosciences Department of Oregon State University. Retrieved 26 June 2010.

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.

External links

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

Cetacean anatomy is the study of the form or morphology of cetaceans (whales, dolphins and porpoises). It can be contrasted with cetacean physiology, which is the study of how the component parts of cetaceans function together in these living marine mammals.[1] In practice, cetacean anatomy and cetacean physiology complement each other, the former dealing with the structure of a cetacean, its organs or component parts and how they are put together, such as might be observed on the dissecting table or under the microscope, and the latter dealing with how those components function together in the living marine mammal.

The anatomy of cetaceans have common characteristics with other terrestrial mammals, and, in addition, is often shaped by the physical characteristics of aquatic living, the medium in which these mammals live. Water is much denser than air, holds a relatively small amount of dissolved oxygen, and absorbs more light than air does.

Body

Skeleton Skull

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 maxilla. The braincase is concentrated through the nasal passage to the front and is correspondingly higher, with individual cranial bones that overlap. The bony otic capsule, the petrosal, is only cartilaginous when connected to the skull, so that it can swing independently.[2][3]

Vertebrae

The number of vertebrae that make up the spine varies between species, anywhere between 40 and 93 individual vertebrae. The cervical spine, found in all mammals, consists of seven vertebrae which, however, are greatly reduced or fused together. This gives stability during swimming at the expense of mobility. The fins are carried by the thoracic vertebrae, ranging from 9 to 17 individual vertebrae. The sternum is only cartilaginous, but nonetheless strong. The last two to three pairs of ribs are not connected at all and hang freely in the body wall. Behind it is the stable lumbar and tail part of the spine which includes all other vertebrae. Below the caudal vertebrae is the chevron bone; the vortex developed provides additional attachment points for the tail musculature.[2][3]

Limbs

The front limbs are paddle-shaped with shortened arms and elongated finger bones, to support the movement. They are united by cartilage. It also leads to a proliferation of the finger members, a so-called hyperphalangy, on the second and third fingers. The only functional joint is the shoulder joint in all cetaceans except for the Amazon river dolphin. The collarbone is completely absent. The movement of cetaceans on land is no longer necessary nor possible, due to the great body weight and the atrophied hindlimbs. In fact the rear limbs have become a rudimentary internal appendage without connections to the spine.[2][3]

External organs Jaw

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 oral cavity inflates to expand the mouth. The inflation of the oral cavity causes the cavum ventrale, the folds (throat pleats) on the throat stretching to the naval, to expand, increasing the amount of water that the mouth can store.[7] The mandible is connected to the skull by dense fibers and cartilage, allowing the jaw to swing open at almost a 90° angle. The mandibular symphysis is also fibrocartilaginous, allowing the jaw to bend which lets in more water.[8] To prevent stretching the mouth too far, rorquals have a sensory organ located in the middle of the jaw to regulate these functions.[9] Gulp-feeders, like right whales, on the other hand swim with an open mouth, filling it with water and prey. This makes their head, which can make up a third of their body weight, huge in order to feed effectively. Not able to expand their mouth like rorquals, right whales must have a head that is large enough to take in enough water and food to feed effectively, carrying their bulk all the time.[10]

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 water vapor condenses. This spray, known as the blow, is often visible from far away as a white splash, which can also be caused by water resting on top of the blowhole. Baleen whales have two blowholes, causing a V-shaped blow, while toothed whales have only one blowhole. The trachea only connects to the blowhole and there is no connection to the esophagus as with humans and most other mammals. Because of this, there is no risk of food accidentally ending up in the animal's lungs, and likewise the animal cannot breathe through its mouth. Consequently, whales have no pharyngeal reflex.[15]

Skin

Fins

Internal organs

Intestines The small intestines is divided into three sections: the duodenum, the jejunum, and the ileum. The mesentery is thin in baleen whales. The caecum is present in all whales with the exception of the Amazon river dolphins and the right whales, however it is relatively short in baleen whales. The appendix is absent in all cetaceans.

Stomach In most whales, food is swallowed and travels down through the esophagus where it meets a three-chambered-stomach. The first compartment is known as the fore-stomach; this is where food gets ground up into an acidic liquid, which is then squirted into the main stomach. Like in humans, the food is mixed with hydrochloric acid and protein-digesting enzymes. Then, the partly digested food is moved into the third stomach, in which fat-digesting enzymes, and then mixed with an alkaline liquid to neutralize the acid from the first stomach to prevent damage to the intestinal tract. Once the solution is safe, it is moved into the intestinal tract.

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 gall bladder. Toothed whales have one bile duct and baleen whales have two. Like other mammals, the liver is located in the right side of the body, just below the diaphragm.

Heart

Swim bladder Weberian apparatus

Reproductive organs Testes Ovaries

Nervous system Central nervous system Cerebellum Identified neurons Immune system

See also

References

  1. ^ Prosser, C. Ladd (1991). Comparative Animal Physiology, Environmental and Metabolic Animal Physiology (4th ed.). Hoboken, NJ: Wiley-Liss. pp. 1–12. ISBN 0-471-85767-X.
  2. ^ a b c Bruno Cozzi; Sandro Mazzariol; Michela Podestà; Alessandro Zott (2009). "Diving Adaptations of the Cetacean Skeleton" (PDF). The Open Zoology Journal. 2: 24–32. doi:10.2174/1874336600902010024. Retrieved 5 September 2015.
  3. ^ a b c A. Thomas, J. (1916). Outlines of Zoology (5 ed.). pp. 766–771.
  4. ^ The Institute for Marine Mammal Studies. "Frequently asked questions". IMMS. Retrieved 17 February 2016.
  5. ^ Webster, D.; Fay, R.; Popper, A. (1992). "The Marine Mammal Ear: Specializations for aquatic audition and echolocation". In Ketten, D.R. (ed.). The Evolutionary Biology of Hearing. Springer-Verlag. pp. 717–750. ISBN 978-1-4612-7668-5.
  6. ^ Au, W.; Fay, R.; Popper, A. (2000). "Cetacean Ears". Hearing by Whales and Dolphins. Springer-Verlag. pp. 43–108. doi:10.1007/978-1-4612-1150-1. ISBN 978-0-387-94906-2. {{cite book}}: |journal= ignored (help)
  7. ^ W. Vogle, A.; A. Lillie, Margo; A. Piscitelli, Marina; A. Goldbogen, Jeremy; D. Pyenson, Nicholas; E. Shadwick, Robert (2015). "Stretchy nerves are an essential component of the extreme feeding mechanism of rorqual whales". Current Biology. 25 (9): 360–361. doi:10.1016/j.cub.2015.03.007.
  8. ^ A. Goldbogen, Jeremy (2010). "The Ultimate Mouthful: Lunge Feeding in Rorqual Whales". American Scientist. 98 (2): 124. doi:10.1511/2010.83.124.
  9. ^ Welsh, Jennifer (2012). "Whale's Big Gulp Aided by Newfound Organ". Retrieved 23 January 2016.
  10. ^ Kenney, Robert D. (2002). "North Atlantic, North Pacific and Southern Right Whales". In William F. Perrin, Bernd Wursig and J. G. M. Thewissen (ed.). The Encyclopedia of Marine Mammals. Academic Press. pp. 806–813. ISBN 0-12-551340-2.
  11. ^ Rommel, S. A.; Costidis, A. M.; Fernandez, A.; Jepson, P. D.; Pabst, D. A.; McLellan, W. A.; Houser, D. S.; Cranford, T. W.; van Helden, A. L.; Allen, D. M.; Barros, N. B. (2006). "Elements of beaked whale anatomy and diving physiology and some hypothetical causes of sonar-related stranding". Journal of Cetacean Research and Management. 7 (3): 189–209.
  12. ^ Mass et al. 2007, pp. 701–715.
  13. ^ Reidenberg, Joy S. (2007). "Anatomical adaptations of aquatic mammals". The Anatomical Record. 290 (6): 507–513. doi:10.1002/ar.20541.
  14. ^ Bjerager, P.; Heegaard, S.; Tougaar, J. (2003). "Anatomy of the eye of the sperm whale (Physeter macrocephalus L.)". Aquatic Mammals. 29 (1): 31–36. doi:10.1578/016754203101024059.
  15. ^ Tinker 1988, The Respiratory System, pp.65–68.
  16. ^ Cavendish, Marshall (2010). "Gray whale". Mammal Anatomy: An Illustrated Guide. ISBN 978-0-7614-7882-9.

Further reading