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Brief Summary
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There are 23 living species of crocodilian. These include crocodiles, alligators, and caimans. This family’s closest living relatives are birds, not other reptiles. Crocodilians can walk on four legs or swim using their strong tails. They can also walk on their tails. The American crocodile can swim up to 20 miles per hour.
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Crocodylidae
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The crocodylian family Crocodylidae includes the true crocodiles, which are the members of the subfamily Crocodylinae, as well as the false gharial, the only extant member of the subfamily Tomistominae. The latter is a subject of controversy as to whether it is a crocodile or actually belongs in the family Gavialidae.[1] Further genetic analysis has to be done to come to a final conclusion.

Taxonomy

A total of three extant genera are placed in the family Crocodylidae, including a total of 15 species, including the desert crocodile, which is now accepted as a true species rather than a subspecies of the Nile crocodile. Recent studies suggest the dwarf crocodile, Osteolaemus tetraspis, is not a single, but two or even three species.[2] If so, the species count of extant crocodiles would be 16 or 17, putting the extant crocodylian species to a total of 26 instead of 24.

True crocodiles

The two extant genera of true crocodiles, Crocodylus and Osteolaemus, are in the subfamily Crocodylinae. Even according to traditional classification, the Tomistoma is not a true crocodile, though it is a member of the family Crocodylidae. Latest molecular evidence points to an even greater difference, creating the possibility that in fact Tomistoma is genetically closer to the gharial than true crocodiles. If proven, the species will be classified under the family Gavialidae.[1]

Their most obvious external differences from alligators are visible in the head. Crocodiles have narrower and longer heads, and more V-shaped than U-shaped snouts. The alligator's upper jaw is wider than its lower jaw, and the teeth in the lower jaw fit into small depressions in the upper jaw. The upper and lower jaws of the crocodiles are the same width, and teeth in the lower jaw fall along the edge or outside the upper jaw when the mouth is closed. When the crocodile's mouth is closed, the large fourth tooth in the lower jaw fits into a constriction in the upper jaw. For hard-to-distinguish specimens, the protruding tooth is the most reliable feature to define a species.

Crocodylidae

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A skull of the extinct Voay robustus

Most species are grouped into the genus Crocodylus. The other extant genus, Osteolaemus, is monotypic (as is Mecistops, if recognized).

Phylogeny

The cladogram below follows the topology from a 2012 analysis of morphological traits by Christopher A. Brochu and Glenn W. Storrs. Many extinct species of Crocodylus might represent different genera. C. suchus was not included because its morphological codings were identical to those of C. niloticus. However, the authors suggested that it could be explained by their specimen sampling, and considered the two species to be distinct.[4]

.mw-parser-output table.clade{border-spacing:0;margin:0;font-size:100%;line-height:100%;border-collapse:separate;width:auto}.mw-parser-output table.clade table.clade{width:100%}.mw-parser-output table.clade td{border:0;padding:0;vertical-align:middle;text-align:center}.mw-parser-output table.clade td.clade-label{width:0.8em;border:0;padding:0 0.2em;vertical-align:bottom;text-align:center}.mw-parser-output table.clade td.clade-slabel{border:0;padding:0 0.2em;vertical-align:top;text-align:center}.mw-parser-output table.clade td.clade-bar{vertical-align:middle;text-align:left;padding:0 0.5em}.mw-parser-output table.clade td.clade-leaf{border:0;padding:0;text-align:left;vertical-align:middle}.mw-parser-output table.clade td.clade-leafR{border:0;padding:0;text-align:right} Crocodyloidea

"Asiatosuchus" germanicus

   

Prodiplocynodon langi

     

Asiatosuchus grangeri

   

"Crocodylus" affinis

   

"Crocodylus" depressifrons

     

Brachyuranochampsa eversolei

   

"Crocodylus" acer

Crocodylidae    

Kentisuchus spenceri

     

Dollosuchoides densmorei

   

Megadontosuchus arduini

         

Gavialosuchus eggenburgensis

   

Toyotamaphimeia machikanensis

       

Tomistoma lusitanica

   

Tomistoma schlegelii

         

"Tomistoma" cairense

     

Thecachampsa antiqua

   

Thecachampsa americana

   

Thecachampsa carolinense

       

Penghusuchus pani

     

Paratomistoma courti

   

Maomingosuchus petrolicus

                 

"Crocodylus" megarhinus

     

Kambara implexidens

   

Australosuchus clarkae

     

Trilophosuchus rackhami

   

Quinkana

           

Brochuchus pigotti

   

"Crocodylus" gariepensis

     

Euthecodon arambourgii

   

Euthecodon brumpti

         

Rimasuchus lloydi

     

Voay robustus

     

Osteolaemus osborni

   

Osteolaemus tetraspis

           

Mecistops cataphractus

Crocodylus

C. checchiai

   

C. palaeindicus

     

C. anthropophagus

   

C. thorbjarnarsoni

     

C. niloticus

     

C. siamensis

     

C. palustris

     

C. porosus

   

C. johnsoni

   

C. mindorensis

     

C. novaeguineae

   

C. raninus

             

C. acutus

   

C. intermedius

   

C. rhombifer

   

C. moreletii

                   

References

  1. ^ a b Gatesy, Jorge; Amato, G.; Norell, M.; DeSalle, R.; Hayashi, C. (2003). "Combined support for wholesale taxic atavism in gavialine crocodylians" (PDF). Systematic Biology. 52 (3): 403–422. doi:10.1080/1063515035019703..mw-parser-output cite.citation{font-style:inherit}.mw-parser-output q{quotes:"""""'"'"}.mw-parser-output code.cs1-code{color:inherit;background:inherit;border:inherit;padding:inherit}.mw-parser-output .cs1-lock-free a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/6/65/Lock-green.svg/9px-Lock-green.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-limited a,.mw-parser-output .cs1-lock-registration a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Lock-gray-alt-2.svg/9px-Lock-gray-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-lock-subscription a{background:url("//upload.wikimedia.org/wikipedia/commons/thumb/a/aa/Lock-red-alt-2.svg/9px-Lock-red-alt-2.svg.png")no-repeat;background-position:right .1em center}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration{color:#555}.mw-parser-output .cs1-subscription span,.mw-parser-output .cs1-registration span{border-bottom:1px dotted;cursor:help}.mw-parser-output .cs1-hidden-error{display:none;font-size:100%}.mw-parser-output .cs1-visible-error{font-size:100%}.mw-parser-output .cs1-subscription,.mw-parser-output .cs1-registration,.mw-parser-output .cs1-format{font-size:95%}.mw-parser-output .cs1-kern-left,.mw-parser-output .cs1-kern-wl-left{padding-left:0.2em}.mw-parser-output .cs1-kern-right,.mw-parser-output .cs1-kern-wl-right{padding-right:0.2em}
  2. ^ Eaton, Mitchell J.; Andrew Martin; John Thorbjarnarson; George Amato (March 2009). "Species-level diversification of African dwarf crocodiles (Genus Osteolaemus): A geographic and phylogenetic perspective". Molecular Phylogenetics and Evolution. 50 (3): 496–506. doi:10.1016/j.ympev.2008.11.009. PMID 19056500.
  3. ^ McAliley, Willis, Ray, White, Brochu & Densmore (2006). Are crocodiles really monophyletic?—Evidence for subdivisions from sequence and morphological data. Molecular Phylogenetics and Evolution 39:16–32.
  4. ^ Brochu, C. A.; Storrs, G. W. (2012). "A giant crocodile from the Plio-Pleistocene of Kenya, the phylogenetic relationships of Neogene African crocodylines, and the antiquity of Crocodylus in Africa". Journal of Vertebrate Paleontology. 32 (3): 587. doi:10.1080/02724634.2012.652324.
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Crocodylidae: Brief Summary
provided by wikipedia EN

The crocodylian family Crocodylidae includes the true crocodiles, which are the members of the subfamily Crocodylinae, as well as the false gharial, the only extant member of the subfamily Tomistominae. The latter is a subject of controversy as to whether it is a crocodile or actually belongs in the family Gavialidae. Further genetic analysis has to be done to come to a final conclusion.

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