Alligatoridae

{{Short description|Family of crocodilians including alligators and caimans}}

{{Automatic taxobox

| taxon = Alligatoridae

| fossil_range = {{fossilrange/linked|Campanian|Present}}

| image = Florida Alligator.jpg

| image_caption = American alligator (Alligator mississippiensis)

| authority = Gray, 1844

| subdivision_ranks = Subfamilies

| subdivision = * Alligatorinae

Caimaninae

}}

The family Alligatoridae of crocodylians includes alligators, caimans and their extinct relatives.

Phylogeny

File:Alligator olseni.jpg

File:Alligator prenasalis.JPG

The superfamily Alligatoroidea includes all crocodilians (fossil and extant) that are more closely related to the American alligator than to either the Nile crocodile or the gharial.{{cite journal |last=Brochu |first=Christopher A. |title=Phylogenetic approaches toward crocodylian history |journal=Annual Review of Earth and Planetary Sciences |volume=31 |year=2003 |pages=357–97 |doi=10.1146/annurev.earth.31.100901.141308 }} This is a stem-based definition for alligators, and is more inclusive than the crown group Alligatoridae.{{cite journal | author=Michael S. Y. Lee |author2=Adam M. Yates |date=27 June 2018 |title=Tip-dating and homoplasy: reconciling the shallow molecular divergences of modern gharials with their long fossil |journal=Proceedings of the Royal Society B: Biological Sciences |volume=285 |issue=1881 |pmid=30051855| doi=10.1098/rspb.2018.1071 |pmc=6030529 |doi-access=free}} As a crown group, Alligatoridae only includes the last common ancestor of all extant (living) alligators, caimans, and their descendants (living or extinct), whereas Alligatoroidea, as a stem-based group, also includes more basal extinct alligator ancestors that are more closely related to living alligators than to crocodiles or gavialids. When considering only living taxa (neontology), Alligatoroidea and Alligatoridae contain the same species.

The simplified cladogram below shows Alligatoridae's relationships to other extant (living) crocodilians.{{cite journal |last1=Rio |first1=Jonathan P. |last2=Mannion |first2=Philip D. |date=6 September 2021 |title=Phylogenetic analysis of a new morphological dataset elucidates the evolutionary history of Crocodylia and resolves the long-standing gharial problem |journal=PeerJ |volume=9 |page=e12094 |doi=10.7717/peerj.12094 |pmid=34567843 |pmc=8428266 |doi-access=free}}{{Cite journal |last1=Hekkala |first1=E. |last2=Gatesy |first2=J. |last3=Narechania |first3=A. |last4=Meredith |first4=R. |last5=Russello |first5=M. |last6=Aardema |first6=M. L. |last7=Jensen |first7=E. |last8=Montanari |first8=S. |last9=Brochu |first9=C. |last10=Norell |first10=M. |last11=Amato |first11=G. |date=2021-04-27 |title=Paleogenomics illuminates the evolutionary history of the extinct Holocene "horned" crocodile of Madagascar, Voay robustus |journal=Communications Biology |language=en |volume=4 |issue=1 |page=505 |doi=10.1038/s42003-021-02017-0 |pmid=33907305 |pmc=8079395 |issn=2399-3642 |doi-access=free}}

{{clade| style=font-size:85%;line-height:85%

|label1=Crocodylia

|sublabel1=(crown group)

|1={{clade

|label1=Alligatoroidea

|sublabel1=(stem-based group)

|1={{clade |state1=dashed

|1=Leidyosuchus{{extinct}}

|2={{clade

|label1=Diplocynodontinae{{extinct}}

|1=Diplocynodon{{extinct}}

|label2=Globidonta

|sublabel2=(stem-based group)

|2={{clade

|1=extinct basal Alligatoroid Globidontans{{extinct}}

|label2=Alligatoridae

|sublabel2=(crown group)

|2={{clade

|label1=Caimaninae

|sublabel1=(stem-based group)

|1={{clade

|1=Caiman 90 px

|2=Melanosuchus 120 px }}

|2=Paleosuchus 90 px }}

|label2=Alligatorinae

|sublabel2=(stem-based group)

|2=Alligator 100 px }} }} }} }}

|2={{clade

|1=extinct basal Crocodilians{{extinct}} (possibly including Mekosuchinae{{extinct}})

|label2=Longirostres

|sublabel2=(crown group)

|2={{clade

|label1=Crocodyloidea

|sublabel1=(stem-based group)

|1={{clade

|1=extinct basal crocodiles{{extinct}}

|2=Crocodylidae (crown group) 90 px }}

|label2=Gavialoidea

|sublabel2=(stem-based group)

|2={{clade

|1=extinct basal Gavialoids{{extinct}}

|label2=Gavialidae

|sublabel2=(crown group)

|2={{clade

|1=Gavialis 110 px

|2=Tomistoma 90 px }} }} }} }} }} }}

Alligatoridae contains eight living species: two alligators within Alligatorinae, and the six caimans of Caimaninae. Phylogenetic studies using molecular DNA consistently resolve their relationships as follows:{{Cite journal |last1=Bittencourt |first1=Pedro Senna |last2=Campos |first2=Zilca |last3=Muniz |first3=Fabio de Lima |last4=Marioni |first4=Boris |last5=Souza |first5=Bruno Campos |last6=Da Silveira |first6=Ronis |last7=de Thoisy |first7=Benoit |last8=Hrbek |first8=Tomas |last9=Farias |first9=Izeni Pires |date=22 March 2019 |title=Evidence of cryptic lineages within a small South American crocodilian: the Schneider’s dwarf caiman Paleosuchus trigonatus (Alligatoridae: Caimaninae) |journal=PeerJ |volume=7 |page=e6580 |doi=10.7717/peerj.6580 |pmid=30931177 |pmc=6433001 |doi-access=free }}

{{clade

|label1=Alligatoridae

|1={{clade

|label1=Caimaninae

|1={{clade

|1=Paleosuchus palpebrosus Cuvier's dwarf caiman

|2=Paleosuchus trigonatus Schneider's dwarf caiman }}

|label2=Jacarea

|2={{clade

|1={{clade

|1=Caiman crocodilus Spectacled caiman

|2=Caiman yacare Yacare caiman }}

|2=Caiman latirostris Broad-snouted caiman }}

|2=Melanosuchus niger Black caiman }} }}

|label2=Alligatorinae

|2={{clade

|1=Alligator sinensis Chinese alligator

|2=Alligator mississippiensis American alligator }} }} }}

The below detailed cladogram shows one proposal for the internal relationships within Alligatoridae including fossil species, based on morphological analysis{{Cite journal|author1=Paula Bona |author2=Martín D. Ezcurra |author3=Francisco Barrios |author4=María V. Fernandez Blanco |year=2018 |title=A new Palaeocene crocodylian from southern Argentina sheds light on the early history of caimanines |journal=Proceedings of the Royal Society B: Biological Sciences |volume=285 |issue=1885 |page=20180843 |doi=10.1098/rspb.2018.0843 |pmid=30135152 |pmc=6125902 }} (although the exact alligatoroid phylogeny is still disputed).

{{clade| style=font-size:85%;line-height:85%

|label1=Alligatoroidea

|sublabel1=(stem-based group)

|1={{clade

|1=Leidyosuchus{{extinct}}

|2={{clade

|1=Diplocynodon{{extinct}}

|label2=Alligatoridae

|sublabel2=(crown group)

|2={{clade

|label1=Alligatorinae

|sublabel1=(stem-based group)

|1={{clade

|1=Ceratosuchus{{extinct}}

|2=Allognathosuchus{{extinct}}

|3=Navajosuchus{{extinct}}

|4=Arambourgia{{extinct}}

|5=Procaimanoidea{{extinct}}

|6={{clade

|1=Wannaganosuchus{{extinct}}

|2={{clade

|1=Alligator prenasalis{{extinct}}

|2={{clade

|1=Alligator mcgrewi{{extinct}}

|2={{clade

|1=Alligator olseni{{extinct}}

|2={{clade

|1=Alligator sinensis Chinese alligator

|2={{clade

|1=Culebrasuchus{{extinct}}

|2={{clade

|1=Alligator mississippiensis American alligator

|2=Alligator mefferdi{{extinct}}

|3=Alligator thomsoni{{extinct}} }} }} }} }} }} }} }} }}

|label2=Caimaninae

|sublabel2=(stem-based group)

|2={{clade

|1={{clade

|1=Stangerochampsa{{extinct}}

|2=Albertochampsa{{extinct}}

|3=Brachychampsa{{extinct}} }}

|2={{clade

|1=Protocaiman{{extinct}}

|2={{clade

|1=Gnatusuchus{{extinct}}

|2={{clade

|1=Globidentosuchus{{extinct}}

|2={{clade

|1={{clade

|1=Eocaiman{{extinct}}

|2=Notocaiman{{extinct}} }}

|2={{clade

|1=Kuttanacaiman{{extinct}}

|2={{clade

|1={{clade

|1=Purussaurus{{extinct}}

|2=Mourasuchus{{extinct}} }}

|2={{clade

|1={{clade

|1=Necrosuchus{{extinct}}

|2=Tsoabichi{{extinct}}

|3={{clade

|1=Paleosuchus trigonatus Smooth-fronted caiman

|2=Paleosuchus palpebrosus Cuvier's dwarf caiman }} }}

|2={{clade

|1=Centenariosuchus{{extinct}}

|2={{clade

|1={{clade

|1=Caiman latirostris Broad-snouted caiman

|2=Melanosuchus niger Black caiman }}

|2={{clade

|1={{clade

|1=Caiman yacare Yacare caiman

|2=Caiman crocodilus Spectacled caiman }}

|2={{clade

|1=Caiman brevirostris{{extinct}}

|2={{clade

|1=La Venta Caiman{{extinct}}

|2=Caiman wannlangstoni{{extinct}}

}} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }}

Evolution

The superfamily Alligatoroidea is thought to have split from the crocodile-gharial lineage in the late Cretaceous, about 87 million years ago. Leidyosuchus of Alberta is among the earliest known genera. Fossil alligatoroids have been found throughout Eurasia as land bridges across both the North Atlantic and the Bering Strait have connected North America to Eurasia during the Cretaceous, Paleogene, and Neogene periods. Alligators and caimans split in North America during the early Tertiary or late Cretaceous (about 53 million{{cite journal|last10= Wu|first10=X.-B.|last9= Zhang|first9=B.-W.|last8= Deng|first8=Y.-P.|last7= Ouyang|first7=J.-H.|last6= Jiang|first6=X.-Y.|last5= Lee|first5=P.-S.|last4= Yan|first4=P.|last3= Zhang|first3=H.-B.|last2= Miao|first2=J.-S.|last1= Pan|first1=T.|title= Near-complete phylogeny of extant Crocodylia (Reptilia) using mitogenome-based data|journal= Zoological Journal of the Linnean Society |year= 2020|volume=191|issue=4|pages=1075–1089|doi= 10.1093/zoolinnean/zlaa074}} to about 65 million years ago{{cite journal|last1= Oaks|first1= J.R.|title=A time-calibrated species tree of Crocodylia reveals a recent radiation of the true crocodiles |journal= Evolution |volume= 65|issue= 11|year= 2011|pages= 3285–3297|doi= 10.1111/j.1558-5646.2011.01373.x|pmid= 22023592|s2cid= 7254442|doi-access= free}}) and the latter reached South America by the Paleogene, before the closure of the Isthmus of Panama during the Neogene period. The Chinese alligator split from the American alligator about 33 million years ago 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.{{cite journal|doi= 10.2307/3889340|title= Phylogenetics, Taxonomy, and Historical Biogeography of Alligatoroidea|last=Brochu|first=Christopher A.|journal=Society of Vertebrate Paleontology Memoir|volume=6|year=1999|pages=9–100|jstor=3889340}} The alligator's full mitochondrial genome was sequenced in the 1990s.{{cite journal|author1=Janke, A. |author2=Arnason, U. |year=1997|title=The complete mitochondrial genome of Alligator mississippiensis and the separation between recent archosauria (birds and crocodiles)|journal=Molecular Biology and Evolution|volume= 14|issue= 12|pages= 1266–72|pmid= 9402737|doi= 10.1093/oxfordjournals.molbev.a025736|doi-access= free}} The full genome, published in 2014, suggests that the alligator evolved much more slowly than mammals and birds.{{cite journal |vauthors=Green RE, Braun EL, Armstrong J, Earl D, Nguyen N, Hickey G, Vandewege MW, St John JA, Capella-Gutiérrez S, Castoe TA, Kern C, Fujita MK, Opazo JC, Jurka J, Kojima KK, Caballero J, Hubley RM, Smit AF, Platt RN, Lavoie CA, Ramakodi MP, Finger JW, Suh A, Isberg SR, Miles L, Chong AY, Jaratlerdsiri W, Gongora J, Moran C, Iriarte A, McCormack J, Burgess SC, Edwards SV, Lyons E, Williams C, Breen M, Howard JT, Gresham CR, Peterson DG, Schmitz J, Pollock DD, Haussler D, Triplett EW, Zhang G, Irie N, Jarvis ED, Brochu CA, Schmidt CJ, McCarthy FM, Faircloth BC, Hoffmann FG, Glenn TC, Gabaldón T, Paten B, Ray DA |title=Three crocodilian genomes reveal ancestral patterns of evolution among archosaurs |journal=Science |volume=346 |issue=6215 |page=1254449 |year=2014 |pmid=25504731 |pmc=4386873 |doi=10.1126/science.1254449 }}

True alligators

The lineage including alligators proper (Alligatorinae) occurs in the fluvial deposits of the age of the Upper Chalk in Europe, where they died out in the Pliocene age. The true alligators are today represented by two species, A. mississippiensis in the southeastern United States which can grow to {{convert|15.6|ft|m}} and weigh {{convert|1000|lb|kg}},[https://web.archive.org/web/20110521070055/http://animals.nationalgeographic.com/animals/reptiles/american-alligator/?source=A-to-Z "American alligator"]. animals.nationalgeographic.com. National Geographic Society. with unverified sizes of up to {{convert|19.2|ft|m}}, and the small A. sinensis in the Yangtze River, China, which grows to an average of {{convert|5|ft|m}}. Their name derives from the Spanish el lagarto, which means "the lizard".

Caimans

File:Caiman crocodilus Tropicario 2.JPG at the Helsinki Tropicario Zoo aquarium in Helsinki, Finland in 2010]]

In Central and South America, the alligator family is represented by six species of the subfamily Caimaninae, which differ from the alligator by the absence of a bony septum between the nostrils, and having ventral armour composed of overlapping bony scutes, each of which is formed of two parts united by a suture. Besides the three species in Caiman, the smooth-fronted caimans in genus Paleosuchus and the black caiman in Melanosuchus are described. Caimans tend to be more agile and crocodile-like in their movements, and have longer, sharper teeth than alligators.{{cite book | author = Guggisberg, C.A.W. | title = Crocodiles: Their Natural History, Folklore, and Conservation| year = 1972 | page = 195 | publisher = David & Charles| isbn = 978-0-7153-5272-4}}

C. crocodilus, the spectacled caiman, has the widest distribution, from southern Mexico to the northern half of Argentina, and grows to a modest size of about {{convert|2.2|m|ft|abbr=on}}. The largest is the near-threatened Melanosuchus niger, the jacaré-açu or large or black caiman of the Amazon River basin. Black caimans grow to {{convert|14.5|ft|abbr=on|order=flip}}, with the unverified size of up to {{convert|5.7|m|abbr=on}}. The black caiman and American alligator are the only members of the alligator family that pose the same danger to humans as the larger species of the crocodile family.

Although caimans have not been studied in depth, scientists have learned their mating cycles (previously thought to be spontaneous or year-round) are linked to the rainfall cycles and the river levels, which increases chances of survival for their offspring.

Taxonomy

{{See also|List of crocodilians}}† = extinctFile:Crocnest.JPG, Florida, United States]]

File:Spectacled caiman by Keven Law.jpg head]]

File:Wikipedia-7744.jpg, Jauaperi River, Amazonia]]

File:Caïman de Schneider (Paleosuchus trigonatus).jpg]]

Family Alligatoridae
Subfamily Alligatorinae
Genus Alligator
† Alligator hailensis
† Alligator mcgrewi
† Alligator mefferdi
Alligator mississippiensis, American alligator
† Alligator olseni
† Alligator prenasalis
Alligator sinensis, Chinese alligator
† Alligator thomsoni
Genus † Allognathosuchus
Genus † Arambourgia
Genus † Ceratosuchus
Genus † Chrysochampsa
Genus † Eoalligator
Genus † Hassiacosuchus
Genus † Krabisuchus
Genus † Navajosuchus?
Genus † Procaimanoidea
Genus † Wannaganosuchus
Subfamily Caimaninae
Genus † Acresuchus
Genus † Bottosaurus{{cite journal |author=Adam P. Cossette |year=2020 |title=A new species of Bottosaurus (Alligatoroidea: Caimaninae) from the Black Peaks Formation (Palaeocene) of Texas indicates an early radiation of North American caimanines |journal=Zoological Journal of the Linnean Society |volume=191 |pages=276–301 |doi=10.1093/zoolinnean/zlz178 }}
Genus Caiman
† Caiman brevirostris
Caiman crocodilus, Spectacled caiman
Caiman latirostris, Broad-snouted caiman
† Caiman lutescans
† Caiman venezuelensis
† Caiman wannlangstoni
Caiman yacare, Yacare caiman
Genus † Centenariosuchus
Genus † Chinatichampsus
Genus † Culebrasuchus
Genus † Eocaiman
Genus † Globidentosuchus
Genus † Gnatusuchus
Genus † Kuttanacaiman
Genus Melanosuchus
† Melanosuchus fisheri
Melanosuchus niger, Black caiman
Genus † Mourasuchus
Genus † Necrosuchus
Genus † Orthogenysuchus
Genus Paleosuchus
Paleosuchus palpebrosus, Cuvier's dwarf caiman
Paleosuchus trigonatus, Smooth-fronted caiman
Genus † Protocaiman
Genus † Purussaurus
Genus † Tsoabichi

References

External links

[http://www.crocodilian.com "Crocodilians: Natural History & Conservation"] {{Webarchive|url=https://web.archive.org/web/20110708204615/http://www.crocodilian.com/ |date=2011-07-08 }} crocodilian.com
[http://www.fossilworks.org/cgi-bin/bridge.pl?taxon_no=38421&is_real_user=1&action=taxonInfo# "Family Alligatoridae Gray 1844 (alligator)"] {{Webarchive|url=https://web.archive.org/web/20220605165516/http://www.fossilworks.org/cgi-bin/bridge.pl?taxon_no=38421&is_real_user=1&action=taxonInfo |date=2022-06-05 }}, fossilworks.org.
{{Commons category-inline}}
{{Wikispecies-inline}}

Category:Taxa named by John Edward Gray

Category:Crocodilian families

Category:Extant Campanian first appearances