Difference between revisions of "Alligatoridae" - New World Encyclopedia

From New World Encyclopedia
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{{Mergefrom|Alligatorinae|date=December 2008}}
 
 
{{Taxobox
 
{{Taxobox
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| name = Alligators and Caimans
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| name = Alligators and caimans
 
| fossil_range = [[Cretaceous]] - Recent
 
| fossil_range = [[Cretaceous]] - Recent
 
| image = Florida Alligator.jpg
 
| image = Florida Alligator.jpg
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| image_caption = [[American Alligator]]
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| image_caption = [[American alligator]]
 
| regnum = [[Animal]]ia
 
| regnum = [[Animal]]ia
 
| phylum = [[Chordate|Chordata]]
 
| phylum = [[Chordate|Chordata]]
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''[[Paleosuchus]]''
 
''[[Paleosuchus]]''
 
}}
 
}}
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[[Alligatoridae]] is a family of
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:in having wider and shorter heads, with more obtuse snouts; in having the fourth, enlarged tooth of the under jaw received, not into an external notch, but into a pit formed for it within the upper one; in lacking a jagged fringe which appears on the hind legs and feet of the crocodile; in having the toes of the hind feet webbed not more than half way to the tips; and an intolerance to salinity
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:common name for any species belonging to the reptile family Crocodylidae (order Crocodilia).
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'''Alligators''' and '''caimans''' are [[archosaur]]s, [[species]] of [[crocodilia]]ns and form the [[family (biology)|family]] '''Alligatoridae''' (sometimes regarded instead as the [[subfamily]] '''Alligatorinae''').
 
'''Alligators''' and '''caimans''' are [[archosaur]]s, [[species]] of [[crocodilia]]ns and form the [[family (biology)|family]] '''Alligatoridae''' (sometimes regarded instead as the [[subfamily]] '''Alligatorinae''').
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: flexible semi-erect (semi-sprawled) posture. They can walk in low, sprawled "belly walk," or hold their legs more directly underneath them to perform the "high walk" (Britton 2001). Most other reptiles can only walk in a sprawled position, and chameleons are the only modern reptiles with a more erect posture than crocodilians. The semi-erect posture makes it possible for some species to gallop on land if necessary (Britton 2001). An Australian species can reach a speed of over 16 km/h while galloping on an irregular forest floor. Their ankle bones, or tarsi are highly modified. Modern crocodilian locomotion is not a primitive trait, but a specialization for their semi-aquatic lifestyle.
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All crocodilians have, like Homo sapiens (humans), thecodont dentition (teeth set in bony sockets), but unlike mammals, they replace their teeth throughout life (though not in “extreme” old age).
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:'''Alligator''' is the common name for large, primarily aquatic [[reptile]]s that belong to the [[genus]] ''Alligator'' of the family [[Alligatoridae]] and order [[crocodile#Order Crocodilia|Crocodilia]]. The family Alligatoridae also includes the caimans, and the order Crocodilia also includes the true crocodiles (family Crocodylidae).
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:[[Alligator]]s (family Alligatoridae, genus ''Alligator'') differ from [[crocodile]]s (family Crocodylidae) principally in having wider and shorter heads, with more obtuse snouts; and in having the fourth, enlarged tooth of the under jaw received, not into an external notch, but into a pit formed for it within the upper one. While in alligators only the upper teeth can be seen with the jaws closed, in true crocodiles the upper and lower teeth can be seen—though many individuals bear jaw deformities, which complicate this means of identification. In addition, alligators lack a jagged fringe, which appears on the hind legs and feet of the crocodile; the toes of the hind feet are webbed not more than half way to the tips; and alligators have a lower tolerance to [[salinity]], strongly preferring fresh water, while crocodiles can tolerate salt water due to specialized [[gland]]s for filtering out [[salt]].
  
 
== True alligators ==
 
== True alligators ==

Revision as of 19:28, 10 January 2009

Alligators and caimans
Fossil range: Cretaceous - Recent
American alligator
American alligator
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Sauropsida
Order: Crocodilia
Family: Alligatoridae
Gray, 1844
Extant genera

Alligator
Caiman
Melanosuchus
Paleosuchus

Alligatoridae is a family of


in having wider and shorter heads, with more obtuse snouts; in having the fourth, enlarged tooth of the under jaw received, not into an external notch, but into a pit formed for it within the upper one; in lacking a jagged fringe which appears on the hind legs and feet of the crocodile; in having the toes of the hind feet webbed not more than half way to the tips; and an intolerance to salinity
common name for any species belonging to the reptile family Crocodylidae (order Crocodilia).

Alligators and caimans are archosaurs, species of crocodilians and form the family Alligatoridae (sometimes regarded instead as the subfamily Alligatorinae).

flexible semi-erect (semi-sprawled) posture. They can walk in low, sprawled "belly walk," or hold their legs more directly underneath them to perform the "high walk" (Britton 2001). Most other reptiles can only walk in a sprawled position, and chameleons are the only modern reptiles with a more erect posture than crocodilians. The semi-erect posture makes it possible for some species to gallop on land if necessary (Britton 2001). An Australian species can reach a speed of over 16 km/h while galloping on an irregular forest floor. Their ankle bones, or tarsi are highly modified. Modern crocodilian locomotion is not a primitive trait, but a specialization for their semi-aquatic lifestyle.

All crocodilians have, like Homo sapiens (humans), thecodont dentition (teeth set in bony sockets), but unlike mammals, they replace their teeth throughout life (though not in “extreme” old age).

Alligator is the common name for large, primarily aquatic reptiles that belong to the genus Alligator of the family Alligatoridae and order Crocodilia. The family Alligatoridae also includes the caimans, and the order Crocodilia also includes the true crocodiles (family Crocodylidae).
Alligators (family Alligatoridae, genus Alligator) differ from crocodiles (family Crocodylidae) principally in having wider and shorter heads, with more obtuse snouts; and in having the fourth, enlarged tooth of the under jaw received, not into an external notch, but into a pit formed for it within the upper one. While in alligators only the upper teeth can be seen with the jaws closed, in true crocodiles the upper and lower teeth can be seen—though many individuals bear jaw deformities, which complicate this means of identification. In addition, alligators lack a jagged fringe, which appears on the hind legs and feet of the crocodile; the toes of the hind feet are webbed not more than half way to the tips; and alligators have a lower tolerance to salinity, strongly preferring fresh water, while crocodiles can tolerate salt water due to specialized glands for filtering out salt.

True alligators

Alligators proper occur in the fluvial deposits of the age of the Upper Chalk in Europe, where they did not die out until the Pliocene age. The true alligators are now restricted to two species, A. mississippiensis in the southeastern United States, which can grow to 4.24 m (14 ft) and weigh 1000 lbs (454.5 kg)[1], with the record length of 5.81 m (19 ft 2 in), and the small A. sinensis in the Yangtze River, People's Republic of China, which grows to an average of 1.5 m (5 ft). Their name derives from the Spanish el lagarto, which means "the lizard".

Alligator prenasalis fossil

Caimans

In Central and South America, the alligator family is represented by five species of the genus Caiman, which differs from the alligator by the absence of a bony septum between the nostrils, and the ventral armour is composed of overlapping bony scutes, each of which is formed of two parts united by a suture. Some authorities further divide this genus into three, splitting off the smooth-fronted caimans into a genus Paleosuchus and the Black Caiman into Melanosuchus. Caimans tend to be more agile and crocodile-like in their movements, and have longer, sharper teeth than alligators.[2]

C. crocodilus, the Spectacled Caiman, has the widest distribution, from southern Mexico to the northern half of Argentina, and grows to a modest size of about 2.2 meters. The largest is the near-threatened Melanosuchus niger, the Jacare-assu, Large, or Black Caiman of the Amazon. Black Caimans grow to 16.5 feet (5 meters) [3], with the largest recorded size 5.79 m (19 ft). The Black Caiman and American Alligator are the only members of the alligator family posing the same danger to humans as the larger species of the crocodile family.

Although the Caiman has not been studied in-depth, it has been discovered that their mating cycles (previously thought to be spontaneous or year-round) are linked to the rainfall cycles and the river levels in order to increase their offspring's chances of survival.

Differences from crocodiles

See also: Crocodilia#Differences between alligators and crocodiles

Alligators differ from crocodiles principally in having wider and shorter heads, with more obtuse snouts; in having the fourth, enlarged tooth of the under jaw received, not into an external notch, but into a pit formed for it within the upper one; in lacking a jagged fringe which appears on the hind legs and feet of the crocodile; in having the toes of the hind feet webbed not more than half way to the tips; and an intolerance to salinity, alligators strongly preferring fresh water, while crocodiles can tolerate salt water due to specialized glands for filtering out salt. In general, crocodiles tend to be more dangerous to humans than alligators.

Taxonomy

An alligator nest at Everglades National Park, Florida, United States.
  • ORDER Crocodilia
    • Family Alligatoridae
      • Genus Leidyosuchus (extinct)
      • Genus Deinosuchus (extinct)
      • Subfamily Alligatorinae
        • Genus Albertochampsa (extinct)
        • Genus Chrysochampsa (extinct)
        • Genus Hassiacosuchus (extinct)
        • Genus Navahosuchus (extinct)
        • Genus Ceratosuchus (extinct)
        • Genus Allognathosuchus (extinct)
        • Genus Hispanochampsa (extinct)
        • Genus Arambourgia (extinct)
        • Genus Procaimanoidea (extinct)
        • Genus Wannaganosuchus (extinct)
        • Genus Alligator
          • Alligator prenasalis (extinct)
          • Alligator mcgrewi (extinct)
          • Alligator olseni (extinct)
          • Chinese Alligator, Alligator sinensis
          • Alligator mefferdi (extinct)
          • American Alligator, Alligator mississippiensis
      • Subfamily Caimaninae
        • Genus Necrosuchus (extinct)
        • Genus Eocaiman (extinct)
        • Genus Paleosuchus
          • Cuvier's Dwarf Caiman, Paleosuchus palpebrosus
          • Smooth-fronted Caiman, Paleosuchus trigonatus
        • Genus Purussaurus (extinct)
        • Genus Mourasuchus (extinct)
        • Genus Orthogenysuchus (extinct)
        • Genus Caiman
          • Yacare Caiman, Caiman yacare
          • Spectacled Caiman, Caiman crocodilus
            • Rio Apaporis Caiman, C. c. apaporiensis
            • Brown Caiman, C. c. fuscus
          • Caiman lutescans (extinct)
          • Caiman sorontans[citation needed] (extinct) - Not reported in the literature, probably a 'nomen nudum'
          • Broad-snouted Caiman, Caiman latirostris
        • Genus Melanosuchus
          • Melanosuchus fisheri (extinct)
          • Black Caiman, Melanosuchus niger

References
ISBN links support NWE through referral fees

  1. ↑ <http://www.eparks.org/marine_and_coastal/marine_wildlife/alligator.asp>
  2. ↑ Guggisberg, C.A.W. (1972). Crocodiles: Their Natural History, Folklore, and Conservation. ISBN 0715352725. 
  3. ↑ <http://www.flmnh.ufl.edu/cnhc/cbd-faq-q2.htm>

External links

Template:Wikispecies-inline Template:Commonscat-inline

Related articles on alligators, caimans, crocodiles and gharials
Topics
Alligator–Crocodile differentation · Crocodile exoskeleton · Crocodillin · Foramen of Panizza · Gastralium · List of crurotarsans · Madras Crocodile Bank Trust · The Croc Festival
Human
interaction
U.S. Alligator fatalities · Crocodile attacks · Crocodile tears · Famous crocodiles and alligators · Sewer alligator

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