Editing Pterosaur (section)

===Origins===
[[File:Scleromochlus restoration.jpg|left|thumb|Life restoration of ''[[Scleromochlus]],'' an [[archosauromorph]] theorized to be related to pterosaurs.]]
Because pterosaur [[anatomy]] has been so heavily modified for flight, and immediate [[transitional fossil]] predecessors have not so far been described, the ancestry of pterosaurs is not fully understood.{{sfn|Witton|2013|p=13}} The oldest known pterosaurs were already fully adapted to a flying lifestyle. Since Seeley, it was recognised that pterosaurs were likely to have had their origin in the "archosaurs", what today would be called the [[Archosauromorpha]]. In the 1980s, early cladistic analyses found that they were [[Avemetatarsalia]]ns (archosaurs closer to [[dinosaur]]s than to [[crocodilia]]ns). As this would make them also rather close relatives of the dinosaurs, these results were seen by Kevin Padian as confirming his interpretation of pterosaurs as bipedal warm-blooded animals. Because these early analyses were based on a limited number of taxa and characters, their results were inherently uncertain.{{sfn|Witton|2013|pp=14, 17}}

Several influential researchers who rejected Padian's conclusions offered alternative hypotheses. [[David Unwin]] proposed an ancestry among the basal Archosauromorpha, specifically long-necked forms ("[[Protorosauria|protorosaurs]]") such as [[tanystropheid]]s. A placement among [[archosauriformes|basal archosauriforms]] like ''[[Euparkeria]]'' was also suggested.<ref name=DU06b/> Basal archosauromorps such as these seemed to be good candidates for close pterosaur relatives due to their long-limbed anatomy; especially notable is ''[[Sharovipteryx]]'', which possessed skin membranes on its hindlimbs likely used for gliding.{{sfn|Witton|2013|pp=14, 17}} A 1999 study by [[Michael Benton]] reinforced that pterosaurs were avemetatarsalians closely related to ''[[Scleromochlus]],'' and named the group Ornithodira to encompass pterosaurs and dinosaurs''.<ref name="Benton, 1999">{{cite journal|last1=Benton|first1=M.J.|year=1999|title=''Scleromochlus taylori'' and the origin of dinosaurs and pterosaurs|journal=Philosophical Transactions of the Royal Society B: Biological Sciences|volume=354|issue=1388|pages=1423–46|doi=10.1098/rstb.1999.0489|pmc=1692658}}</ref>'' In 1996, research S. Christopher Bennett published an analysis finding pterosaurs to be protorosaurs or closely related to them after removing characteristics of the hindlimb from his analysis, to test the possibility of locomotion-based [[convergent evolution]] between pterosaurs and [[dinosaur]]s.<ref>{{cite journal | last1 = Bennett | first1 = S. Christopher | year = 1996 | title = The phylogenetic position of the Pterosauria within the Archosauromorpha | journal = Zoological Journal of the Linnean Society | volume = 118 | issue = 3| pages = 261–308 | doi = 10.1111/j.1096-3642.1996.tb01267.x | doi-access = free }}</ref> A 2007 reply by Dave Hone and Michael Benton could not reproduce this result, finding pterosaurs to be closely related to dinosaurs even without hindlimb characters. They concluded that, although more basal pterosauromorphs are needed to clarify their relationships, current evidence indicates that pterosaurs are avemetatarsalians, as either the sister group of ''Scleromochlus'' or a branch between the latter and ''[[Lagosuchus]]''.<ref name="hone&benton2007">{{cite journal |author1=Hone D.W.E. |author2=Benton M.J. | year = 2007 | title = An evaluation of the phylogenetic relationships of the pterosaurs to the archosauromorph reptiles | journal = Journal of Systematic Palaeontology | volume = 5 | issue = 4| pages = 465–69 | doi = 10.1017/S1477201907002064|s2cid=86145645 }}</ref> 
[[File:Lagerpeton NT small.jpg|thumb|Life restoration of ''[[Lagerpeton]]''. [[Lagerpetidae|Lagerpetid]]s share many [[anatomical]] and [[Neuroanatomy|neuroanatomical]] similarities with pterosaurs and may be close relatives]]
A 2011 archosaur-focused phylogenetic analysis by [[Sterling Nesbitt]] benefited from far more data and found strong support for pterosaurs being avemetatarsalians, though ''Scleromochlus'' was not included due to its poor preservation.<ref name="NSJ11">{{cite journal|last=Nesbitt|first=S.J.|year=2011|title=The early evolution of archosaurs: relationships and the origin of major clades|journal=Bulletin of the American Museum of Natural History|volume=352|pages=1–292|doi=10.1206/352.1|hdl=2246/6112|s2cid=83493714|doi-access=free}}</ref> A 2016 archosauromorph-focused study by [[Martin Ezcurra]] included various proposed pterosaur relatives, yet also found pterosaurs to be closer to dinosaurs and unrelated to more basal taxa.<ref>{{cite journal |last1=Ezcurra |first1=Martín D. |title=The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms |journal=PeerJ |date=28 April 2016 |volume=4 |pages=e1778 |doi=10.7717/peerj.1778 |pmid=27162705 |pmc=4860341 |doi-access=free }}</ref> Working from his 1996 analysis, Bennett published a 2020 study on ''[[Scleromochlus]]'' which argued that both ''Scleromochlus'' and pterosaurs were non-archosaur archosauromorphs, albeit not particularly closely related to each other.<ref>{{cite journal | last1 = Bennett | first1 = S.C. | year = 2020 | title = Reassessment of the Triassic archosauriform ''Scleromochlus taylori'': neither runner nor biped, but hopper | journal = PeerJ | volume = 8 | page = e8418 | doi = 10.7717/peerj.8418 | pmid = 32117608 | pmc = 7035874 | doi-access = free }}</ref> By contrast, a later 2020 study proposed that [[lagerpetid]] [[archosaur]]s were the sister clade to pterosauria.<ref name="Ezcurra Nesbitt Bronzati 2020">{{cite journal |last1=Ezcurra |first1=Martín D. |last2=Nesbitt |first2=Sterling J. |last3=Bronzati |first3=Mario |last4=Dalla Vecchia |first4=Fabio Marco |last5=Agnolin |first5=Federico L. |last6=Benson |first6=Roger B. J. |last7=Brissón Egli |first7=Federico |last8=Cabreira |first8=Sergio F. |last9=Evers |first9=Serjoscha W. |last10=Gentil |first10=Adriel R. |last11=Irmis |first11=Randall B. |last12=Martinelli |first12=Agustín G. |last13=Novas |first13=Fernando E. |last14=Roberto da Silva |first14=Lúcio |last15=Smith |first15=Nathan D. |last16=Stocker |first16=Michelle R. |last17=Turner |first17=Alan H. |last18=Langer |first18=Max C. |title=Enigmatic dinosaur precursors bridge the gap to the origin of Pterosauria |journal=Nature |date=17 December 2020 |volume=588 |issue=7838 |pages=445–449 |doi=10.1038/s41586-020-3011-4 |pmid=33299179 |bibcode=2020Natur.588..445E |s2cid=228077525 |url=http://doc.rero.ch/record/329918/files/ser_edp.pdf }}</ref> This was based on newly described fossil [[skull]]s and [[forelimb]]s showing various [[anatomical]] similarities with pterosaurs and reconstructions of lagerpetid [[brain]]s and [[sensory system]]s based on [[CT scan]]s also showing [[Neuroanatomy|neuroanatomical]] similarities with pterosaurs.<ref>{{Cite web|title=Paleontologists find pterosaur precursors that fill a gap in early evolutionary history|url=https://phys.org/news/2020-12-paleontologists-pterosaur-precursors-gap-early.html|access-date=2020-12-14|website=phys.org|language=en}}</ref><ref>{{Cite web|last=Black|first=Riley|title=Pterosaur Origins Flap into Focus|url=https://www.scientificamerican.com/article/pterosaur-origins-flap-into-focus/|access-date=2020-12-14|website=Scientific American|language=en}}</ref> The results of the latter study were subsequently supported by an independent analysis of early pterosauromorph interrelationships.<ref>{{cite journal |last1=Baron |first1=Matthew G. |title=The origin of Pterosaurs |journal=Earth-Science Reviews |date=October 2021 |volume=221 |pages=103777 |doi=10.1016/j.earscirev.2021.103777 |bibcode=2021ESRv..22103777B }}</ref>

A related problem is the origin of pterosaur flight.{{sfn|Witton|2013|p=18}} Like with birds, hypotheses can be ordered into two main varieties: "ground up" or "tree down". Climbing a tree would cause height and gravity to provide both the energy and a strong [[selection pressure]] for incipient flight.{{clarify|date=July 2021}} [[Rupert Wild]] in 1983 proposed a hypothetical "propterosaurus": a lizard-like arboreal animal developing a membrane between its limbs, first to safely parachute and then, gradually elongating the fourth finger, to glide.<ref>Rupert Wild, 1983, "Über die Ursprung der Flugsaurier", ''Weltenberger Akademie, Erwin Rutte-Festschrift'', pp. 231–38</ref> However, subsequent cladistic results did not fit this model well. Neither protorosaurs nor ornithodirans are biologically equivalent to lizards. Furthermore, the transition between gliding and flapping flight is not well-understood. More recent studies on basal pterosaur hindlimb morphology seem to vindicate a connection to ''Scleromochlus''. Like this archosaur, basal pterosaur lineages have plantigrade hindlimbs that show adaptations for saltation.<ref name="ReferenceA" />

At least one study found that the early Triassic [[ichnofossil]] ''[[Prorotodactylus]]'' is anatomically similar to that of early pterosaurs.<ref name="Ezcurra Nesbitt Bronzati 2020"/>