Crocodilia

Crocodilians Fossil range: Cretaceous - Recent 84-0 Ma
Crocodilian fossil found in the Messel Pit fossil site.
Scientific classification
Class:	Reptilia
Subclass:	Diapsida
Infraclass:	Archosauromorpha
(Unranked) :	Crurotarsi
Superorder:	Crocodylomorpha
Order:	Crocodilia Owen, 1842
Families:	Gavialidae Alligatoridae Crocodylidae See below for prehistoric taxa

Crocodilia (or Crocodylia) is an order of large reptiles that appeared about 84 million years ago in the late Cretaceous Period (Campanian stage). They are the closest living relatives of birds, as the two groups are the only known survivors of the Archosauria. Members of the crocodilian stem group, the clade Crurotarsi, appeared about 220 million years ago in the Triassic Period and exhibited a wide diversity of forms during the Mesozoic Era.

Evolution and classification

Eusuchia, a modern clade which includes the crown group Crocodilia, first appeared in the Lower Cretaceous of Europe. Isisfordia duncani lived approximately 95 to 98 million years ago, during the Cenomanian epoch of the Upper Cretaceous. Isisfordia is the second oldest known eusuchian, and the earliest crocodylomorph yet found in Australia. Eusuchians underwent a mass radiation during the Late Cretaceous and the Paleogene, in which they evolved into numerous forms, such as semi-aquatic dinosaur-eating species (Deinosuchus); hooved, terrestrial carnivores (Pristichampsus), and 'hatchet'-shaped skulled forms (Baru).

Taxonomy

• Superorder Crocodylomorpha
  • Order Crocodilia
    • Superfamily Gavialoidea
      • Family Gavialidae: gharials & false gharials
    • Superfamily Alligatoroidea
      • Family Alligatoridae
        • Subfamily Diplocynodontinae (extinct)
        • Subfamily Alligatorinae: alligators
        • Subfamily Caimaninae: caimans
    • Superfamily Crocodyloidea
      • Family Crocodylidae
        • Subfamily Mekosuchinae (extinct)
        • Subfamily Crocodylinae: crocodiles

Phylogeny

Cladogram after Brochu (1997).

Eusuchia

  ├──Hylaeochampsa
  └──┬──Allodaposuchus
     └──Crocodilia
          ├──Gavialoidea
          │     ├──Eothoracosaurus
          │     └──┬──Thoracosaurus
          │        └──┬──Argochampsa
          │           ├──Eosuchus
          │           └──Gavialidae
          └──┬──Borealosuchus
             └──┬──Pristichampsus
                └──Brevirostres
                    ├──Alligatoroidea
                    │   ├──Leidyosuchus
                    │   ├─?Deinosuchus
                    │   └──Globidonta
                    │       ├──Stangerochampsa
                    │       ├──Brachychampsa
                    │       └──Alligatoridae
                    └──Crocodyloidea
                        ├──Prodiplocynodon
                        └──┬──Asiatosuchus
                           └──┬──Brachyuranochampsa
                              └──┬──Harpacochampsa
                                 └──Crocodylidae

External links

• Before Crocodiles, the Hairless Coyote
• International Crocodile Rescue
• Mikko's Phylogeny Archive Crocodyliformes