Brevirostres

Brevirostres Temporal range: Late Cretaceous - Recent, 83.5–0 Ma PreЄ Є O S D C P T J K Pg N
American alligator (Alligator mississippiensis)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Superorder:	Crocodylomorpha
Order:	Crocodilia
Clade:	Brevirostres von Zittel, 1890

Brevirostres is a clade of crocodylians that includes alligatoroids and crocodyloids. Brevirostres are crocodylians with short snouts, and are distinguished from the long, slender-snouted gharials. It is defined phylogenetically as the last common ancestor of Alligator mississippiensis (the American alligator) and Crocodylus niloticus (the Nile crocodile) and all of its descendants.^[1] Below is a cladogram showing the phylogenetic relations of Brevirostres from Brochu (1997):^[2]

Crocodylia	Gavialoidea †Borealosuchus †Pristichampsus  Brevirostres  Alligatoroidea Crocodyloidea

Brevirostres was first named by Karl Alfred von Zittel in 1890. Von Zittel considered Gavialis, the gharial, to be closely related to Tomistoma, the false gharial, and excluded them from the group. Tomistoma, as its name implies, is traditionally not considered closely related to Gavialis, but instead classified as a crocodylid. Under this classification, all members of Brevirostres are brevirostrine, or short-snouted. Recent molecular analyses support von Zittel's classification in placing Tomistoma as a close relative of Gavialis. If this classification is accepted, Brevirostres can be considered a junior synonym of Crocodylia. If Brevirostres is defined as the last common ancestor of all brevirostrines -including Tomistoma- and all of its descendants, the common ancestor's descendants would include Gharial, and thus all crocodylians.^[3]

References

1. Brochu, C. A. (2003). "Phylogenetic approaches toward crocodylian history" (PDF). Annual Review of Earth and Planetary Sciences. 31: 357–97. doi:10.1146/annurev.earth.31.100901.141308.
2. Brochu, C.A. (1997). "A review of "Leidyosuchus" (Crocodyliformes, Eusuchia) from the Cretaceous through Eocene of North America". Journal of Vertebrate Paleontology. 17 (4): 679–697. doi:10.1080/02724634.1997.10011017. JSTOR 4523857.
3. Brochu, C.A. (1999). "Phylogenetics, taxonomy, and historical biogeography of Alligatoroidea". Memoir (Society of Vertebrate Paleontology). 6: 9–100. doi:10.2307/3889340.