Editing Bipedalism (section)

===Archosaurs (includes crocodilians and dinosaurs)===

====Birds====
All [[birds]] are bipeds, as is the case for all [[theropod]] [[dinosaurs]]. However, [[hoatzin]] chicks have claws on their wings which they use for climbing.

====Other archosaurs====
Bipedalism evolved more than once in [[archosaurs]], the group that includes both dinosaurs and [[crocodilia]]ns.<ref>{{Cite journal |title=The evolution of locomotion in archosaurs |last=Hutchinson |first=J. R.| journal=Comptes Rendus Palevol |volume=5 |issue=3–4 |year=2006 |pages=519–530 |doi=10.1016/j.crpv.2005.09.002 |bibcode=2006CRPal...5..519H |url=http://doc.rero.ch/record/15518/files/PAL_E2922.pdf}}</ref> All dinosaurs are thought to be descended from a fully bipedal ancestor, perhaps similar to ''[[Eoraptor]]''.

Dinosaurs diverged from their [[archosaur]] ancestors approximately 230 million years ago during the Middle to Late [[Triassic]] period, roughly 20 million years after the [[Permian-Triassic extinction event]] wiped out an estimated 95 percent of all life on Earth.<ref>{{cite web |author=Penn State |title=Global Warming Led To Atmospheric Hydrogen Sulfide And Permian Extinction |website=ScienceDaily |date=1 March 2005 |url=https://www.sciencedaily.com/releases/2005/02/050223130549.htm |url-status=live |archive-url=https://web.archive.org/web/20110605025707/http://www.sciencedaily.com/releases/2005/02/050223130549.htm|archive-date=2011-06-05}}</ref><ref>{{cite web |title=The Day The Earth Nearly Died – programme summary |website=Science & Nature > TV & Radio Follow-up |publisher=BBC |url=http://www.bbc.co.uk/science/horizon/2002/dayearthdied.shtml |url-status=live |archive-url=https://web.archive.org/web/20120901070225/http://www.bbc.co.uk/science/horizon/2002/dayearthdied.shtml|archive-date=2012-09-01}}</ref> [[Radiometric dating]] of fossils from the early dinosaur [[genus]] ''[[Eoraptor]]'' establishes its presence in the fossil record at this time. Paleontologists suspect ''Eoraptor'' resembles the [[Common descent|common ancestor]] of all dinosaurs;<ref>Hayward, T. (1997). The First Dinosaurs. ''Dinosaur Cards''. Orbis Publishing Ltd. D36040612.</ref> if this is true, its traits suggest that the first dinosaurs were small, bipedal predators.<ref>{{Cite journal |last=Sereno |first=Paul C. |author2=Catherine A. Forster |author3=Raymond R. Rogers |author4=Alfredo M. Monetta |date=January 1993 |title=Primitive dinosaur skeleton from Argentina and the early evolution of Dinosauria |journal=Nature |volume=361 |issue=6407 |pages=64–66 |bibcode=1993Natur.361...64S |doi=10.1038/361064a0 |s2cid=4270484}}</ref> The discovery of primitive, dinosaur-like ornithodirans such as ''[[Marasuchus]]'' and ''[[Lagerpeton]]'' in [[Argentina|Argentinian]] [[Middle Triassic]] strata supports this view; analysis of recovered fossils suggests that these animals were indeed small, bipedal predators.

Bipedal movement also re-evolved in a number of other [[dinosaur]] lineages such as the [[Iguanodontia|iguanodonts]]. Some extinct members of [[Pseudosuchia]], a sister group to the avemetatarsalians (the group including dinosaurs and relatives), also evolved bipedal forms – a poposauroid from the [[Triassic]], ''[[Effigia okeeffeae]]'', is thought to have been bipedal.<ref>{{Cite magazine |last=Handwerk| first=Brian |title=Dino-Era Fossil Reveals Two-Footed Croc Relative |magazine=[[National Geographic Magazine|National Geographic]] |url=http://news.nationalgeographic.com/news/2006/01/0125_060125_crocodile.html |date=2006-01-26 |access-date=2007-10-29 |url-status=dead |archive-date=2007-10-31 |archive-url=https://web.archive.org/web/20071031013504/http://news.nationalgeographic.com/news/2006/01/0125_060125_crocodile.html}}</ref> [[Pterosaur]]s were previously thought to have been bipedal, but recent trackways have all shown quadrupedal locomotion.