Alligatorinae Possible | |
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Clade: | Archosauromorpha |
Clade: | Archosauriformes |
Order: | Crocodilia |
Family: | Alligatoridae |
Subfamily: | Alligatorinae Gray, 1844 |
Genera | |
Alligatorinae is a subfamily within the family Alligatoridae that contains the alligators and their closest extinct relatives, and is the sister taxon to Caimaninae (the caimans). Many genera in Alligatorinae are described, but only the genus Alligator is still living, with the remaining genera extinct.
Alligators and caimans split in North America during the early Tertiary or late Cretaceous (about 53 million to about 65 million years ago). [3] [4] The Chinese alligator split from the American alligator about 33 million years ago [3] and likely descended from a lineage that crossed the Bering land bridge during the Neogene. The modern American alligator is well represented in the fossil record of the Pleistocene. [5] The alligator's full mitochondrial genome was sequenced in the 1990s. [6] The full genome, published in 2014, suggests that the alligator evolved much more slowly than mammals and birds. [7]
Alligatorinae is cladistically defined as Alligator mississippiensis (the American alligator) and all species closer to it than to Caiman crocodylus (the spectacled caiman). [8] [9] This is a stem-based definition for Alligatorinae, and means that it includes more basal extinct alligator ancestors that are more closely related to living alligators than to caimans.
The below cladogram shows the phylogeny of Alligatorinae. [10] [9]
Alligatoridae |
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The family Alligatoridae of crocodylians includes alligators, caimans and their extinct relatives.
Boverisuchus is an extinct genus of planocraniid crocodyliforms known from the middle Eocene of Germany and western North America. It was a relatively small crocodyliform with an estimated total length of approximately 2.2–3.6 metres (7.2–11.8 ft).
Procaimanoidea is an extinct genus of alligatorid from the Eocene of North America. It was named posthumously in 1946 by Charles W. Gilmore; the type species is P. utahensis, from the Uintan of Utah. It is based on USNM 15996, a nearly complete skull and partial left hind leg. A second species, P. kayi, was named in 1941 by C.C. Mook as a species of Hassiacosuchus, for remains from the Bridgerian of Wyoming. It was reassigned to Procaimanoidea in 1967 by Wassersug and Hecht.
A caiman is an alligatorid belonging to the subfamily Caimaninae, one of two primary lineages within the Alligatoridae family, the other being alligators. Caimans are native to Central and South America and inhabit marshes, swamps, lakes, and mangrove rivers. They have scaly skin and live a fairly nocturnal existence. They are relatively small-sized crocodilians with an average maximum weight of 6 to 40 kg depending on species, with the exception of the black caiman, which can grow more than 4 m (13 ft) in length and weigh in excess of 450 kg. The black caiman is the largest caiman species in the world and is found in the slow-moving rivers and lakes that surround the Amazon basin. The smallest species is the Cuvier's dwarf caiman, which grows to 1.2 to 1.5 m long. There are six different species of caiman found throughout the watery jungle habitats of Central and Southern America. The average length for most of the other caiman species is about 2 to 2.5 m long.
Alligatoroidea is one of three superfamilies of crocodylians, the other two being Crocodyloidea and Gavialoidea. Alligatoroidea evolved in the Late Cretaceous period, and consists of the alligators and caimans, as well as extinct members more closely related to the alligators than the two other groups.
Arambourgia is an extinct monotypic genus of alligatorine crocodylian from Europe. It was named in 1905 as Allognathosuchus gaudryi. It was made a separate genus Arambourgia in 1940. This was synonymized with Allognathosuchus haupti in 1990, but later reassigned as its own genus once again in 2004. Arambourgia was likely to have been part of an early dispersal event of alligatorines from North America to Europe during the Eocene epoch. Arambourgia had non-serrated teeth and a deep orienirostral snout, unlike the flatter snouts of most other alligatorids.
Brachychampsa is an extinct genus of alligatorid, possibly a basal caiman. Specimens have been reported from New Mexico, Colorado, Wyoming, Montana, North and South Dakota, New Jersey, and Saskatchewan, though only those from Montana, Utah, and New Mexico are based on material sufficient to justify the referral. Some specimens have been reported from the Campanian-aged deposits of Central Asia, although the species status is indeterminate for these fossils. The genus first appeared during the late Campanian stage of the Late Cretaceous and became extinct during the late Maastrichtian stage of the Cretaceous. Brachychampsa is distinguished by an enlarged fifth maxillary tooth in the upper jaw.
Planocrania is an extinct genus of eusuchian crocodyliforms from what is now China. Two species are currently known to belong to the genus.
Stangerochampsa is an extinct genus of alligatorid, possibly an alligatorine or a stem-caiman, from the Late Cretaceous of Alberta. It is based on RTMP.86.61.1, a skull, partial lower jaws, and partial postcranial skeleton discovered in the late Campanian–early Maastrichtian-age Horseshoe Canyon Formation. Stangerochampsa was described in 1996 by Wu and colleagues. The type species is S. mccabei. The generic name honors the Stanger family, the owners of the ranch where the specimen was found, and the species name honors James Ross McCabe, who discovered, collected, and prepared it. Stangerochampsa is described as "small to medium–sized"; the type skull is 20.0 centimetres (7.9 in) long from the tip of the snout to the occipital condyle, and is 13.0 centimetres (5.1 in) wide at its greatest, while the thigh bone is 14.2 centimetres (5.6 in) long. It had heterodont dentition, with large crushing teeth at the rear of the jaws.
Tsoabichi is an extinct genus of caimanine crocodylian. Fossils are known from the Green River Formation in Wyoming, and date back to the Ypresian stage of the Eocene. The genus was named and described in 2010 by paleontologist Christopher A. Brochu, with the type species being Tsoabichi greenriverensis. According to the current understanding of caiman evolutionary relationships, Tsoabichi is a basal member of Caimaninae and may have evolved after caimans dispersed into North America from northern and central South America, their main center of diversity in the Cenozoic.
Alligator prenasalis is an extinct species of alligator from the Late Eocene period. It is well known, with many fossils having been collected from the Chadron and Brule Formations in South Dakota. The species was first named in 1904, but was originally classified as a crocodile in the genus Crocodilus. It was reassigned to the genus Alligator in 1918 on the basis of more complete material. It is the earliest known member of the genus Alligator.
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 and all forms more closely related to it than to Diplocynodon. The group's fossil range extends back into the Campanian stage of 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.
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, with Hanyusuchus having become extinct in the last few centuries.
Brevirostres is a paraphyletic group of crocodilians that included alligatoroids and crocodyloids. Brevirostres are crocodilians with small snouts, and are distinguished from the long-snouted gharials. It is defined phylogenetically as the last common ancestor of Alligator mississippiensis and Crocodylus niloticus and all of its descendants. This classification was based on morphological studies primarily focused on analyzing skeletal traits of living and extinct fossil species, and placed the gharials outside the group due to their unique skull structure, and can be shown in the simplified cladogram below:
Culebrasuchus is an extinct, monotypic genus of caiman alligatorid known from the Early to Middle Miocene (Hemingfordian) of the Panama Canal Zone of Panama. It contains a single species, Culebrasuchus mesoamericanus.
Planocraniidae is an extinct family of eusuchian crocodyliforms known from the Paleogene of Asia, Europe and North America. The family was coined by Li in 1976, and contains three genera, Boverisuchus, Duerosuchus and Planocrania. Planocraniids were highly specialized crocodyliforms that were adapted to living on land. They had extensive body armor, long legs, and blunt claws resembling hooves, and are sometimes informally called "hoofed crocodiles".
Alligator olseni is an extinct species of alligator. They lived in the Early Miocene period, around 20.4–15.97 million years ago and possibly earlier. Their range was principally in what is now known as Florida, United States, and possibly extending into southeastern Texas. It is a small alligator with an estimated body length of 2.6 metres (8.5 ft).
Alligator mcgrewi is an extinct species of alligator described by K.P. Schmidt in 1941. They lived in the Early Miocene period, and their range was principally in what is now Nebraska, United States. It is a small alligator with an estimated body length of 1.6 metres (5.2 ft).
Alligator thomsoni is an extinct species of alligator that existed during the Early Miocene period. Their range was principally in what is now known as Nebraska, United States.
Alligator mefferdi is an extinct species of alligator described by Charles Craig Mook. They lived in the Miocene period, and their range was principally in what is now Nebraska, United States. The type specimen was discovered in the Ash Hollow Formation at Ash Hollow State Historical Park.