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Alligatoridae; Temporal range: Cretaceous - Holocene,83–0 Ma PreꞒ Ꞓ O S D C P T J K Pg N
	American alligator (Alligator mississippiensis)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Crocodilia
Clade:	Globidonta
Family:	Alligatoridae; Gray, 1844
Subfamilies
	Alligatorinae; Caimaninae; Incertae sedis †Orientalosuchus; ;

Alligators and Caimans make up the second largest family of the crocodilians, Alligatoridae. There are 4 genera and about 7 known species of Alligatorids. Alligatorids range in size depending on species. The Chinese alligator (Aligator sinensis) is usually about 1.5 metres (4.9 ft) while the American Alligator (A. mississippiensis) is usually 4 m (13 ft). The largest American alligator was 5.79 m (19.0 ft) long. The Black Caiman of the Amazon can reach as much as 6 m (20 ft).

Alligatorids live in the southern United States, Central America, northern South America and near the Yangzee river in China.

Alligators vs crocodiles

There are several differences between alligators and crocodiles. Alligators have shorter and wider snouts. They prefer fresh water to saltwater. Crocodiles have a gland that removes much of the salt. Alligators do not have this gland. In alligators, the fourth tooth of their lower jaw fits into a pit in the upper jaw. In crocodilians this tooth fits into a groove on the outside of the jaw. Alligators are also less aggressive than crocodilids. Usually only the largest of the species are a threat to humans.

Species

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 (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

↑ Family Alligatoridae (Alligators and Caiman) Archived 2016-03-04 at the Wayback Machine University of Bristol. Quote:"The Alligatoridae appears in the Upper Cretaceous while the genus Alligator first occurs in the Oligocene."