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Archosauriformes

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Archosauriforms
Temporal range:Latest Permian–Present,252–0Ma
Row 1 (basalarchosauriforms):Erythrosuchus africanus,Euparkeria capensis;

Row 2 (Pseudosuchia):Crocodylus mindorensis,Typothorax coccinarum;
Row 3 (Avemetatarsalia):Casuarius casuarius,Anhanguera piscator.

Scientific classificationEdit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauromorpha
Clade: Crocopoda
Clade: Archosauriformes
Gauthier,1986
Subgroups[2]

Archosauriformes(Greekfor 'ruling lizards', andLatinfor 'form') is acladeofdiapsidreptilesencompassingarchosaursand some of their close relatives. It was defined byJacques Gauthier(1994) as the clade stemming from thelast common ancestorofProterosuchidaeand Archosauria.[3]Phil Senter(2005) defined it as the most exclusive clade containingProterosuchusand Archosauria.[4]Gauthier as part of thePhylonyms(2020) defined the clade as the last common ancestor and all descendants ofGallus,Alligator,andProterosuchus.[5]Archosauriforms are a branch ofarchosauromorphswhich originated in theLate Permian(roughly 252million years ago) and persist to the present day as the two surviving archosaur groups:crocodiliansandbirds.

Archosauriforms present several traits historically ascribed to the group Archosauria. These include serrated teeth set in deep sockets, a more active metabolism, and anantorbital fenestra(a hole in the skull in front of the eyes). Reptiles with these traits have also been termed "thecodonts"in older methods of classification. Thecodontia is aparaphyleticgroup, and its usage as ataxonomiccategory has been rejected under moderncladisticsystems. The name Archosauriformes is intended as amonophyleticreplacement compatible with modern taxonomy.

Evolutionary history

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Early archosauriforms, informally termed "proterosuchians",were superficially crocodile-like animals with sprawling gaits, carnivorous habits, and long hooked snouts. Unlike the bulk of theirtherapsidcontemporaries, archosauriforms survived the catastrophicend-Permian mass extinction.The Late Permian proterosuchidArchosaurusis similar in appearance to itsEarly Triassicrelative,Proterosuchus.Within a few million years after the beginning of theTriassic,the archosauriformes had diversified past the "proterosuchian"grade.The next major archosauriform group wasErythrosuchidae,a family ofapex predatorswith massive heads, the largest carnivorous reptiles up to that time.

In 2016,Martin Ezcurraprovided the nameEucrocopodafor the clade including all archosauriforms morecrownward(closer to archosaurs) than erythrosuchids. He defined the clade all taxa more closely related toEuparkeria capensis,Proterochampa barrionuevoi,Doswellia kaltenbachi,Parasuchus hislopi,Passer domesticus(the house sparrow), orCrocodylus niloticus(the Nile crocodile) than toProterosuchus fergusiorErythrosuchus africanus.The name translates to "true crocodile feet", in reference to the possession of a crocodilian-stylecrurotarsal ankle.[2]Eucrocopodans include the familiesEuparkeriidae(small, agile reptiles),Proterochampsidae(narrow-snouted predators endemic toSouth America), andDoswelliidae(heavily armoredLaurasianreptiles similar to proterochampsids), as well as various other strange reptiles such asVancleaveaandAsperoris.

The most successful archosauriforms, and the only members to survive into theJurassic,were thearchosaurs.Archosauria includes crocodilians, birds, and all descendants of theircommon ancestor.Extinct archosaurs includeaetosaurs,rauisuchids(both members of the crocodilian branch),pterosaurs,and non-aviandinosaurs(both members of the avian branch).[6]

Metabolism

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Vascular density andosteocytedensity, shape and area have been used to estimate the bone growth rate of archosaurs, leading to the conclusion that this rate had a tendency to grow in ornithodirans and decrease in pseudosuchians.[7]The same method also supports the existence of high resting metabolical rates similar to those of living endotherms (mammals and birds) in theProlacerta-Archosauriformes clade that were retained by most subgroups, though decreased inProterosuchus,Phytosauriaand Crocodilia.[8]Erythrosuchids andEuparkeriaare basal archosauriforms showing signs of high growth rates and elevated metabolism, withErythrosuchuspossessing a rate similar of the fastest-growing dinosaurs. Sexual maturity in those Triassic taxa was probably reached quickly, providing advantage in a habitat with unpredictable variation from heavy rainfall to drought and high mortality.VancleaveaandEuparkeria,which show slower growth rates compared toErythrosuchus,lived after the climatic stabilization. Early crown archosaurs possessed increased growth rates, which were retained by ornithodirans.[9]Ornithosuchiansandpoposaursare stem-crocodilians that show high growth rates similar to those of basal archosauriforms.[10]

Developmental, physiological, anatomical and palaeontological lines of evidence indicate that crocodilians evolved from endothermic ancestors. Living crocodilians are ambush predators adapted to a semi-aquatic lifestyle that benefits from ectothermy due to the lower oxygen intake that allows longer diving time. The mixing of oxygenated and deoxygenated blood in their circulatory system is apparently an innovation that benefits ectothermic life. Earlier archosaurs likely lacked those adaptations and instead had completely separated blood as birds and mammals do.[11][12]A similar process occurred in phytosaurs, which were also semi-aquatic.[13]

The similarities betweenpterosaur,ornithischianandcoelurosaurianintegument suggest a common origin ofthermal insulation(feathers) in ornithodirans at least 250 million years ago.[14][15]Erythrosuchids living in high latitudes might have benefited from some sort of insulation.[13]IfLongisquamawas an archosauromorph, it could be associated with the origin of feathers.[16][13]

Relationships

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Below is a cladogram from Nesbitt (2011):[17]

Archosauriformes

*Note:Phytosaurs were previously placed within Pseudosuchia, or crocodile-line archosaurs.

Below is a cladogram from Senguptaet al.(2017),[18]based on an updated version of Ezcurra (2016)[2]that reexamined all historical members of the "Proterosuchia" (apolyphyletichistorical group includingproterosuchidsanderythrosuchids). The placement of fragmentary taxa that had to be removed to increase tree resolution are indicated by dashed lines (in the most derived position that they can be confidently assigned to). Taxa that arenomina dubiaare indicated by the note "dubium". Bold terminal taxa are collapsed.[2]

Crocopoda

Sources

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  • Gauthier, J. A.(1986)."Saurischian monophyly and the origin of birds".In Padian, K. (ed.).The Origin of Birds and the Evolution of Flight.Memoirs of the California Academy of Sciences. Vol. 8.California Academy of Sciences.pp. 1–55.ISBN978-0-940228-14-6.
  • Gauthier, J. A.;Kluge, A. G.; Rowe, T. (June 1988)."Amniote phylogeny and the importance of fossils"(PDF).Cladistics.4(2).John Wiley & Sons:105–209.doi:10.1111/j.1096-0031.1988.tb00514.x.hdl:2027.42/73857.PMID34949076.S2CID83502693.

References

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  1. ^Sookias, R. B.; Sullivan, C.; Liu, J.; Butler, R. J. (2014)."Systematics of putative euparkeriids (Diapsida: Archosauriformes) from the Triassic of China".PeerJ.2:e658.doi:10.7717/peerj.658.PMC4250070.PMID25469319.
  2. ^abcdEzcurra, Martín D. (2016-04-28)."The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms".PeerJ.4:e1778.doi:10.7717/peerj.1778.ISSN2167-8359.PMC4860341.PMID27162705.
  3. ^Gauthier J. A. (1994):The diversification of the amniotes.In: D. R. Prothero and R. M. Schoch (ed.) Major Features of Vertebrate Evolution: 129-159. Knoxville, Tennessee: The Paleontological Society.
  4. ^Phil Senter (2005). "Phylogenetic taxonomy and the names of the major archosaurian (Reptilia) clades".PaleoBios.25(2): 1–7.
  5. ^Gauthier, Jacques A. (2020). "Archosauriformes J. Gauthier 1986 [J. A. Gauthier], converted clade name". In De Queiroz, Kevin; Cantino, Philip; Gauthier, Jacques (eds.).Phylonyms: A Companion to the PhyloCode(1st ed.). Boca Raton: CRC Press.doi:10.1201/9780429446276.ISBN9780429446276.S2CID242704712.
  6. ^Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and Their Kin
  7. ^Cubo, Jorge; Roy, Nathalie Le; Martinez-Maza, Cayetana; Montes, Laetitia (2012)."Paleohistological estimation of bone growth rate in extinct archosaurs".Paleobiology.38(2): 335–349.Bibcode:2012Pbio...38..335C.doi:10.1666/08093.1.ISSN0094-8373.S2CID84303773.
  8. ^Legendre, Lucas J.; Guénard, Guillaume; Botha-Brink, Jennifer; Cubo, Jorge (2016-11-01)."Palaeohistological evidence for ancestral high metabolic rate in archosaurs".Systematic Biology.65(6): 989–996.doi:10.1093/sysbio/syw033.ISSN1063-5157.PMID27073251.
  9. ^Botha-Brink, Jennifer; Smith, Roger M. H. (2011-11-01). "Osteohistology of the Triassic archosauromorphs Prolacerta, Proterosuchus, Euparkeria, and Erythrosuchus from the Karoo Basin of South Africa".Journal of Vertebrate Paleontology.31(6): 1238–1254.Bibcode:2011JVPal..31.1238B.doi:10.1080/02724634.2011.621797.ISSN0272-4634.S2CID130744235.
  10. ^de Ricqlès, Armand; Padian, Kevin; Knoll, Fabien; Horner, John R. (2008-04-01)."On the origin of high growth rates in archosaurs and their ancient relatives: Complementary histological studies on Triassic archosauriforms and the problem of a" phylogenetic signal "in bone histology".Annales de Paléontologie.94(2): 57–76.Bibcode:2008AnPal..94...57D.doi:10.1016/j.annpal.2008.03.002.ISSN0753-3969.
  11. ^Seymour, Roger S.; Bennett-Stamper, Christina L.; Johnston, Sonya D.; Carrier, David R.; Grigg, Gordon C. (2004-11-01)."Evidence for endothermic ancestors of crocodiles at the stem of archosaur evolution"(PDF).Physiological and Biochemical Zoology.77(6): 1051–1067.doi:10.1086/422766.hdl:2440/1933.ISSN1522-2152.PMID15674775.S2CID10111065.
  12. ^Summers, Adam P. (April 2005)."Warm-hearted crocs".Nature.434(7035): 833–834.Bibcode:2005Natur.434..833S.doi:10.1038/434833a.ISSN1476-4687.PMID15829945.S2CID4399224.
  13. ^abc"Dinosaur Renaissance".Scientific American.April 1975.Retrieved2020-05-03.
  14. ^Yang, Zixiao; Jiang, Baoyu; McNamara, Maria E.; Kearns, Stuart L.; Pittman, Michael; Kaye, Thomas G.; Orr, Patrick J.; Xu, Xing; Benton, Michael J. (January 2019)."Pterosaur integumentary structures with complex feather-like branching".Nature Ecology & Evolution.3(1): 24–30.doi:10.1038/s41559-018-0728-7.hdl:1983/1f7893a1-924d-4cb3-a4bf-c4b1592356e9.ISSN2397-334X.PMID30568282.S2CID56480710.
  15. ^Benton, Michael J.; Dhouailly, Danielle; Jiang, Baoyu; McNamara, Maria (2019-09-01)."The early origin of feathers".Trends in Ecology & Evolution.34(9): 856–869.doi:10.1016/j.tree.2019.04.018.hdl:10468/8068.ISSN0169-5347.PMID31164250.S2CID174811556.
  16. ^Buchwitz, Michael; Voigt, Sebastian (2012-09-01). "The dorsal appendages of the Triassic reptile Longisquama insignis: reconsideration of a controversial integument type".Paläontologische Zeitschrift.86(3): 313–331.Bibcode:2012PalZ...86..313B.doi:10.1007/s12542-012-0135-3.ISSN1867-6812.S2CID84633512.
  17. ^Nesbitt, S.J. (2011)."The early evolution of archosaurs: relationships and the origin of major clades".Bulletin of the American Museum of Natural History.352:1–292.doi:10.1206/352.1.hdl:2246/6112.S2CID83493714.
  18. ^Sengupta, S.; Ezcurra, M.D.; Bandyopadhyay, S. (2017)."A new horned and long-necked herbivorous stem-archosaur from the Middle Triassic of India".Scientific Reports.7(1): 8366.Bibcode:2017NatSR...7.8366S.doi:10.1038/s41598-017-08658-8.PMC5567049.PMID28827583.
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