Alligatorinae Explained

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.

Evolution

Alligators and caimans split in North America during the early Tertiary or late Cretaceous (about 53 million to about 65 million years ago).^{[1] [2]} The Chinese alligator split from the American alligator about 33 million years ago^[1] 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.^[3] The alligator's full mitochondrial genome was sequenced in the 1990s.^[4] The full genome, published in 2014, suggests that the alligator evolved much more slowly than mammals and birds.^[5]

Phylogeny

Alligatorinae is cladistically defined as Alligator mississippiensis (the American alligator) and all species closer to it than to Caiman crocodylus (the spectacled caiman).^{[6] [7]} 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.^{[8] [7]}

Taxonomy

• 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

Notes and References

1. Wu. X.-B.. Zhang. B.-W.. Deng. Y.-P.. Ouyang. J.-H.. Jiang. X.-Y.. Lee. P.-S.. Yan. P.. Zhang. H.-B.. Miao. J.-S.. Pan. T.. Near-complete phylogeny of extant Crocodylia (Reptilia) using mitogenome-based data. Zoological Journal of the Linnean Society . 2020. 191. 4. 1075–1089. 10.1093/zoolinnean/zlaa074.
2. Oaks. J.R.. A time-calibrated species tree of Crocodylia reveals a recent radiation of the true crocodiles . Evolution . 65. 11. 2011. 3285–3297. 10.1111/j.1558-5646.2011.01373.x. 22023592. 7254442. free.
3. 10.2307/3889340. Phylogenetics, Taxonomy, and Historical Biogeography of Alligatoroidea. Brochu. Christopher A.. Society of Vertebrate Paleontology Memoir. 6. 1999. 9–100. 3889340.
4. Janke, A. . Arnason, U. . 1997. The complete mitochondrial genome of Alligator mississippiensis and the separation between recent archosauria (birds and crocodiles). Molecular Biology and Evolution. 14. 12. 1266–72. 9402737. 10.1093/oxfordjournals.molbev.a025736. free.
5. 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 . Three crocodilian genomes reveal ancestral patterns of evolution among archosaurs . Science . 346 . 6215 . 1254449 . 2014 . 25504731 . 4386873 . 10.1126/science.1254449 .
6. Brochu . C. A. . 2003 . Phylogenetic approaches toward crocodylian history . Annual Review of Earth and Planetary Sciences . 31 . 31 . 357–97 . 10.1146/annurev.earth.31.100901.141308 . 2003AREPS..31..357B . 2021-07-26 . 2015-04-02 . https://web.archive.org/web/20150402192747/http://www.naherpetology.org/pdf_files/970.pdf . dead .
7. Brochu . C. A. . 10.1111/j.1096-3642.2011.00716.x . Phylogenetic relationships of Necrosuchus ionensis Simpson, 1937 and the early history of caimanines . Zoological Journal of the Linnean Society . 163 . S228–S256 . 2011 . free .
8. Hastings . A. K. . Bloch . J. I. . Jaramillo . C. A. . Rincon . A. F. . MacFadden . B. J. . Systematics and biogeography of crocodylians from the Miocene of Panama . 10.1080/02724634.2012.713814 . Journal of Vertebrate Paleontology . 33 . 2 . 239 . 2013 . 2013JVPal..33..239H . 83972694 . free .