Crocodyloidea

The Crocodyloidea superfamily of crocodilians evolved in the Late Cretaceous period. Cladistically, it is defined as Crocodylus niloticus (the Nile crocodile) and all crocodylians more closely related to C. niloticus than to either Alligator mississippiensis (the American alligator) or Gavialis gangeticus (the gharial).[1]

Crocodyloidea
Temporal range: Late Cretaceous - Recent, 83.5–0 Ma
Nilecroc100
Crocodylus niloticus (Nile crocodile)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Crocodilia
Clade: Brevirostres
Superfamily: Crocodyloidea
Fitzinger, 1826
Subgroups

Phylogeny

Cladogram after Brochu C. A., Njau J., Blumenschine R. J., Densmore L. D. (2010).[2]

Borealosuchus

Pristichampsus

 Brevirostres 

Leidyosuchus canadensis

 Crocodyloidea 

Prodiplocynodon langi

Asiatosuchus grangeri

"Crocodylus" affinis

"Crocodylus" depressifrons

Brachyuranochampsa

"Crocodylus" acer

 Crocodylidae 
 Tomistominae 

Dollosuchoides

Gavialosuchus

Kentisuchus

Tomistoma

 Crocodylinae 

"Crocodylus" megarhinus

 Mekosuchinae 

Kambara

Australosuchus

Trilophosuchus

 Osteolaeminae 

Rimasuchus

"Crocodylus" pigotti

Euthecodon

Voay

Osteolaemus osborni

O. tetraspis

Mecistops

Crocodylus anthropophagus

C. palaeindicus

C. palustris

C. siamensis

C. porosus

C. johnsoni

C. novaeguineae

C. mindorensis

C. niloticus

C. acutus

C. intermedius

C. rhombifer

C. moreletii

Rhamphosuchus

References

  1. ^ Brochu, Christopher A. (May 2003). "Phylogenetic approaches toward crocodylian history". Annual Review of Earth and Planetary Sciences. 31: 360. doi:10.1146/annurev.earth.31.100901.141308.
  2. ^ Brochu, C. A.; Njau, J.; Blumenschine, R. J.; Densmore, L. D. (2010). "A New Horned Crocodile from the Plio-Pleistocene Hominid Sites at Olduvai Gorge, Tanzania". PLoS ONE. 5 (2): e9333. doi:10.1371/journal.pone.0009333. PMC 2827537. PMID 20195356.
Aegyptosuchidae

Aegyptosuchidae is an extinct family of eusuchian crocodyliforms from the Cretaceous period of Africa. They are characterized by their large size and flat heads. The family includes two genera, Aegyptosuchus and Aegisuchus.

Albertosuchus

Albertosuchus is an extinct genus of crocodyloid crocodylian from the Late Cretaceous of Canada. The type species Albertosuchus knudsenii was named in 2015 from the Scollard Formation in Alberta. Albertosuchus is the northernmost-known Late Cretaceous crocodylian in North America. Albertosuchus lacks the notch in the upper jaw between the maxilla and premaxilla bones that is characteristic of most crocodyloids, and it also has a very short mandibular symphysis (the connection between the two halves of the lower jaw). Phylogenetic analysis indicates that it is one of the most basal members of Crocodyloidea and a close relative of Arenysuchus from the Late Cretaceous of Spain, although the incomplete nature of known material makes these findings uncertain.

Allodaposuchus

Allodaposuchus is an extinct genus of crocodyliforms that includes four species that lived in what is now southern Europe during the Campanian and Maastrichtian stages of the Late Cretaceous. Although generally classified as a non-crocodylian crocodylomorph, it is sometimes placed as one of the earliest true crocodylians. Allodaposuchus is one of the most common Late Cretaceous crocodylomorphs from Europe, with fossils known from Spain, Romania, and France.

Arenysuchus

Arenysuchus (meaning "Arén crocodile") is an extinct genus of crocodyloid from Late Cretaceous (late Maastrichtian stage) deposits of north Spain. It is known from the holotype MPZ ELI-1, a partial skull from Elías site, and from the referred material MPZ2010/948, MPZ2010/949, MPZ2010/950 and MPZ2010/951, four teeth from Blasi 2 site. It was found by the researchers José Manuel Gasca and Ainara Badiola from the Tremp Formation, in Arén of Huesca, Spain. It was first named by Eduardo Puértolas, José I. Canudo and Penélope Cruzado-Caballero in 2011 and the type species is Arenysuchus gascabadiolorum. The generic name refers to the finding site, and "suchus", from Greek meaning crocodile. The specific name honours the researchers who discovered the holotype.

Asiatosuchus

Asiatosuchus is an extinct genus of crocodyloid crocodilians that lived in Eurasia during the Paleogene. Many Paleogene crocodilians from Europe and Asia have been attributed to Asiatosuchus since the genus was named in 1940. These species have a generalized crocodilian morphology typified by flat, triangular skulls. The feature that traditionally united these species under the genus Asiatosuchus is a broad connection or symphysis between the two halves of the lower jaw. Recent studies of the evolutionary relationships of early crocodilians along with closer examinations of the morphology of fossil specimens suggest that only the first named species of Asiatosuchus, A. grangeri from the Eocene of Mongolia, belongs in the genus. Most species are now regarded as nomina dubia or "dubious names", meaning that their type specimens lack the unique anatomical features necessary to justify their classification as distinct species. Other species such as "A." germanicus and "A." depressifrons are still considered valid species, but they do not form an evolutionary grouping with A. grangeri that would warrant them being placed together in the genus Asiatosuchus.

Brachyuranochampsa

Brachyuranochampsa is an extinct genus of crocodyloid crocodilians.

The only robust occurrence of Brachyuranochampsa is B. eversolei from the middle Eocene of Wyoming. Another species, B. zangerli from the lower Bridger Formation at Grizzly Buttes, has been synonymized with another primitive crocodyloid, "Crocodylus" affinis, also known from the Bridger Formation

Crocodylidae

The crocodylian family Crocodylidae includes the true crocodiles, which are the members of the subfamily Crocodylinae, as well as potentially 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.

Crocodylus acer

"Crocodylus" acer is an extinct species of crocodyloid from the Eocene of Utah. A single well preserved skull was described by paleontologist Edward Drinker Cope in 1882 and remains the only known fossil of the species. It was found from the Wasatchian-age Green River Formation. "C." acer had a long, narrow snout and a low, flattened skull.Some postcranial bones have been attributed to "C." acer but they have more recently been suggested to belong to the related species "C." affinis. Although they were first placed in the genus Crocodylus, "C." acer and "C." affinis are not crocodiles. Recent studies place them as early members of Crocodyloidea, only distantly related to Crocodylus. Although it represents a distinct genus, a generic name has not yet been proposed for "C." acer.

Crocodylus affinis

"Crocodylus" affinis is an extinct species of crocodyloid from the Eocene of Wyoming. Fossils were first described from the Bridger Formation by American paleontologist Othniel Charles Marsh in 1871. Marsh described the species, along with every other species of crocodyloid in the Bridger Formation, under the genus Crocodylus. Recent phylogenetic studies of crocodyloids show that "C." affinis is not a species of Crocodylus, but a genus has not yet been erected to include the species. Other Bridger species such as Crocodylus clavis and Brachyuranochampsa zangerli have been synonymized with "C." affinis.

Eusuchia

The Eusuchia ("true crocodiles") are a clade of crocodylomorphs that first appears in the Early Cretaceous with Hylaeochampsa. Along with Dyrosauridae and Sebecosuchia, they were the only crocodyliformes who survived the K-T extinction. Since the other two clades died out 35 and 11 million years ago, all living crocodilian species are eusuchians, as are many extinct forms.

Gavialoidea

Gavialoidea is one of three superfamilies of crocodylians, the other two being Alligatoroidea and Crocodyloidea. Although many extinct species are known, only the gharial Gavialis gangeticus and the false gharial Tomistoma schlegelii are alive today.

Globidonta

Globidonta is a clade of alligatoroids that includes alligators, caimans, and closely related extinct forms. It is defined as a stem-based clade including Alligator mississippiensis (the American Alligator) and all forms more closely related to it than to Diplocynodon. The group's fossil range extends back into the Late Cretaceous with early alligatoroids such as Albertochampsa and Brachychampsa. Extinct globidontans were particularly common in North America and Eurasia, and their modern range also includes South America. The oldest known globidontan is Acynodon from France, which is also the most basal.Basal globidontans are characterized by their blunt snouts and bulbous teeth. Modern globidontans have flattened snouts and more conical teeth, and are seen as more generalized than earlier globidontans. Generalized forms are usually expected to be ancestral to more specialized forms rather than descendants of them, so it is unusual for basal members of the group to appear specialized. This seems to conflict with the "Law of the Unspecialized" first proposed by Edward Drinker Cope in 1894. Under the Law of the Unspecialized, morphological change is always directed toward specialization, and specialized forms can never become "unspecialized" again. This pattern of change, while not seen in globidontans, can be observed in basal members of Alligatoroidea and Crocodyloidea.

Flat-snouted globidontans occurred two times in the evolution of the clade: once in caimans and once in alligators. Alligator sinensis, the Chinese Alligator, has a snout that is somewhat blunt and could be considered specialized. However, its snout is not nearly as blunt as those of more basal globidontans such as Albertachampsa.If the last common ancestor of Diplocynodon and globidontans was more like Diplocynodon, it would have had a generalized snout shape. It is also possible that the generalized form of Diplocynodon may also have arisen from a specialized blunt-snouted ancestor. Baryphracta, a diplocynodontine closely related to Diplocynondon, has a blunt snout and may have been similar in appearance to such an ancestor.

Kambara

Kambara is an extinct genus of mekosuchine crocodylian that lived during the Eocene and Oligocene epochs in Australia.

Kentisuchus

Kentisuchus is an extinct genus of tomistomine crocodylian. It is considered one of the most basal members of the subfamily. Fossils have been found from England and France that date back to the early Eocene. The genus has also been recorded from Ukraine, but it unclear whether specimens from Ukraine are referable to Kentisuchus.

Mekosuchinae

Mekosuchinae is an extinct subfamily of crocodiles from Australia and the South Pacific. They first appear in the fossil record in the Eocene in Australia, and survived until the arrival of humans: in the Pleistocene in Australia and within the Holocene in the Pacific islands of Fiji, New Caledonia and Vanuatu. There is however disagreement on whether or not Mekosuchinae is a subfamily within Crocodylidae, or a distinct family in its own right, Mekosuchidae, within the superfamily Crocodyloidea.

Mekosuchine crocodiles were a diverse group. One of the last species, Mekosuchus inexpectatus from Holocene New Caledonia, may have been arboreal. The early Miocene species, Harpacochampsa camfieldensis, may have resembled a false gharial. Another mekosuchine fossil, currently undescribed, has been found in Miocene deposits from New Zealand. One genus, Mekosuchus, managed to spread to the islands of the Pacific; it is believed to have island-hopped across the Coral Sea, moving first to a now submerged island known as Greater Chesterfield Island, then New Caledonia and onwards.

In the Pleistocene, Quinkana was one of the top terrestrial predators of the Australian continent.

Mekosuchines underwent a drastic decline in post-Miocene Australia, with all genera, except for Quinkana and Pallimnarchus (both perishing during the Quaternary extinction event) becoming expirated or extinct in Australia by the end of the Pliocene. After the demise of Quinkana and Pallimnarchus, the group survived on Vanuatu and New Caledonia until the arrival of humans, who are presumed to have driven them to extinction.

Neosuchia

Neosuchia is a clade within Mesoeucrocodylia that includes all modern extant crocodilians and their closest fossil relatives. It is defined as the most inclusive clade containing all crocodylomorphs more closely related to Crocodylus niloticus (the Nile Crocodile) than to Notosuchus terrestris. Neosuchia is very diverse and may be polyphyletic, as the clade has undergone many revisions since it was first named in 1988. Neosuchians first appear in the Early Jurassic with the earliest known goniopholid Calsoyasuchus, which lived during the Sinemurian and Pliensbachian stages.

Prodiplocynodon

Prodiplocynodon is an extinct genus of basal crocodyloid crocodylian. It is the only crocodyloid known from the Cretaceous and existed during the Maastrichtian stage. The only species of Prodiplocynodon is the type species P. langi from the Lance Formation of Wyoming, known only from a single holotype skull lacking the lower jaw.The skull was collected by the American Museum Expedition of 1892 from exposures near the Cheyenne River in Niobrara County. It was described by Charles C. Mook of the American Museum of Natural History in 1941. The generic name means "before Diplocynodon" because Mook saw close similarities between the holotype skull and that of the alligatoroid Diplocynodon from the Eocene of Europe.

Tomistominae

Tomistominae is a subfamily of crocodylians that includes one living species, the false gharial. Many more extinct species are known, extending the range of the subfamily back to the Eocene epoch. In contrast to the false gharial, which is a freshwater species that lives only in southeast Asia, extinct tomistomines had a global distribution and lived in estuaries and along coastlines.

The classification of tomistomines among Crocodylia has been in flux; while traditionally thought to be within Crocodyloidea, molecular evidence indicates that they are more closely related to true gharials as members of Gavialoidea.

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