Crocodyliformes

Crocodyliformes Temporal range: Late Triassic–Recent, 225–0 Ma PreЄ Є O S D C P T J K Pg N
Protosuchus, an early crocodyliform
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Superorder:	Crocodylomorpha
Clade:	Crocodyliformes Hay, 1930
Clades
† Gobiosuchidae † Orthosuchus † Protosuchidae Mesoeucrocodylia

Crocodyliformes is a clade of crurotarsan archosaurs, the group often traditionally referred to as "crocodilians". They are the only members of Crocodylomorpha who survived beyond the Early Jurassic, while the crocodylomorphs were the only Pseudosuchia group who survived the Triassic–Jurassic extinction event.

In 1988, Michael J. Benton and James M. Clark argued that all traditional names for well-known groups of animals should be restricted to their crown clades, that is, used only for natural groups comprising all living members of any given lineage. This posed a problem for the crocodilians, because the name Crocodylia, while used in various ways by various scientists, had always included not only living crocodilians but many of their extinct ancestors known only from the fossil record.^[1]

Benton and Clark's solution to this issue was to restrict the name Crocodylia to the group containing modern alligators, crocodiles, and gharials, plus any extinct members of those specific families. The traditional group "Crocodylia" was replaced with the name Crocodyliformes, which included many of the extinct families that the new definition left out. Clark and Benton did not initially provide an exact definition for Crocodyliformes; but, in 2001, Paul Sereno and colleagues defined it as the clade including Protosuchus richardsoni and the Nile crocodile, plus all descendants of their common ancestor.^[2]

Chris Brochu agreed with the assessment that Crocodylia as a name has never had stable contents, and that a series of clades larger than the crown group Crocodylia (including Crocodyliformes and the slightly more inclusive clade Crocodylomorpha) was a good solution.^[3] However, in a 2008 paper, Jeremy Martin and Benton, the authors reversed the previous opinion (co-authored by Benton) that Crocodylia should be restricted to the crown group, suggesting that Crocodyliformes should be considered a synonym of a more inclusive Crocodylia, and thus replaced.^[4] Brochu and colleagues rejected this proposal, arguing that the crown definition of Crocodylia is the standard meaning both within and beyond the crocodyliform systematics community.^[5]

Phylogeny

Below is a simplified cladogram based on Fiorelli and Calvo (2007).^[6]

Crocodylomorpha	Terrestrisuchus  Dibothrosuchus  Crocodyliformes   Gobiosuchidae   Gobiosuchus  Zaraasuchus  Orthosuchus  Protosuchidae   Protosuchus  Hemiprotosuchus  "Kayenta Form"  Edentosuchus  Mesoeucrocodylia

In 2012, paleontologists Mario Bronzati, Felipe Chinaglia Montefeltro, and Max C. Langer conducted a broad phylogenetic analysis to produce supertrees of Crocodyliformes, including 184 species. The most parsimonious trees were highly resolved, meaning the phylogenetic relationships found in the analysis were highly likely. Below is a consensus tree from the study:^[7]

Kayentasuchus walkeri Crocodyliformes Protosuchia Orthosuchus stormbergi Protosuchus richardsoni Hemiprotosuchus leali Kayenta Form Edentosuchus tienshanensis Zaraasuchus shepardi Las Hoyas Croc Gobiosuchus kielanae Eopneumatosuchus colberti Zosuchus davidsoni Sichuanosuchus shuhanensis Sichuanosuchus huidongensis Shantungosuchus hangjinensis Shantungosuchus chuhsiensis Shantungosuchus brachycephalus Neuquensuchus universitas Shartegosuchus asperopalatum Fruita Form (Fruitachampsa callisoni) Hsisosuchus dashanpuensis Hsisosuchus chungkingensis Notosuchia Araripesuchus wegeneri Araripesuchus tsangatsangana Araripesuchus buitreraensis Araripesuchus patagonicus Araripesuchus gomesii Uruguaysuchus terrai Uruguaysuchus aznarezi Libycosuchus brevirostris Simosuchus clarki Malawisuchus mwakasyungutiensis Candidodon itapecuruense Notosuchus terrestris Comahuesuchus brachybuccalis Mariliasuchus amarali Yacarerani boliviensis Pakasuchus kapilimai Adamantinasuchus navae Stratiotosuchus maxhechti Pehuenchesuchus enderi Pabwehshi pakistanensis Iberosuchus macrodon Eremosuchus elkoholicus Doratodon Bergisuchus dietrichbergi Baurusuchus salgadoensis Baurusuchus pachechoi Chimaerasuchus paradoxus Sphagesaurus huenei Sphagesaurus montealtensis Sebecus huilensis Sebecus icaeorhinus Itaborai Croc Bretesuchus bonapartei Anatosuchus minor Barcinosuchus gradilis Itasuchus jesuinoi Miadanasuchus oblita Trematochampsa taqueti Caririsuchus camposi Kaprosuchus saharicus Mahajangasuchus insignis Peirosauridae Hamadasuchus rebouli Montealtosuchus arrudacamposi Uberabasuchus terrificus Peirosaurus torminni Lomasuchus palpebrosus Neosuchia

References

1. Benton, M.J. and Clark, J.M. (1988). "Archosaur phylogeny and the relationships of the Crocodylia." Pp. 295–338 in Benton, M.J. (ed.), The phylogeny and classification of the Tetrapods, volume 1. Oxford: Clarendon Press.
2. Sereno, P.C., Larson, H.C.E., Sidor, C.A. and Gado, B. (2001). "The giant crocodyliform Sarcosuchus from the Cretaceous of Africa." Science, 294: 1516–1519.
3. Brochu, C.A. (2003). "Phylogenetic approaches toward crocodylian history." Annu. Rev. Earth Planet. Sci., 31: 357–397.
4. Martin, J.E. and Benton, M.J. (2008). "Crown Clades in Vertebrate Nomenclature: Correcting the Definition of Crocodylia." Systematic Biology, 57: 1,173 — 181.
5. Brochu, A.C., Wagner, J.R., Jouve, S., Sumrall, C.D. and Densmore, L.D. (2009). "A correction corrected: consensus over the meaning of Crocodylia and why it matters" Systematic Biology, 58: 537-543.
6. Fiorelli LE, Calvo JO. 2007. The first "protosuchian" (Archosauria: Crocodyliformes) from the Cretaceous (Santonian) of Gondwana. Arquivos do Museu Nacional, Rio de Janeiro 65 (4): 417-459.
7. Bronzati, M.; Montefeltro, F. C.; Langer, M. C. (2012). "A species-level supertree of Crocodyliformes". Historical Biology: 1. doi:10.1080/08912963.2012.662680.