Editing Dinosaur (section)

===Feathers===
{{Main|Feathered dinosaurs}}
[[File:Feathered non-avian Maniraptora.jpg|thumb|Various feathered non-avian dinosaurs, including ''[[Archaeopteryx]]'', ''[[Anchiornis]]'', ''[[Microraptor]]'' and ''[[Zhenyuanlong]]'']]
Feathers are one of the most recognizable characteristics of modern birds, and a trait that was also shared by several non-avian dinosaurs. Based on the current distribution of fossil evidence, it appears that feathers were an ancestral dinosaurian trait, though one that may have been selectively lost in some species.<ref name=switeknature>{{cite journal |url=https://www.nature.com/articles/nature.2012.10933 |title=Rise of the fuzzy dinosaurs |last1=Switek |first1=Brian |date=July 2, 2012 |department=News |journal=Nature |publisher=Nature Research |location=London |doi=10.1038/nature.2012.10933 |s2cid=123219913 |issn=0028-0836 |access-date=January 1, 2019 |archive-date=April 13, 2020 |archive-url=https://web.archive.org/web/20200413155956/https://www.nature.com/articles/nature.2012.10933 |url-status=live }}</ref> Direct fossil evidence of feathers or feather-like structures has been discovered in a diverse array of species in many non-avian dinosaur groups,<ref name="NYT-20161208" /> both among saurischians and ornithischians. Simple, branched, feather-like structures are known from [[Heterodontosauridae|heterodontosaurids]], primitive [[neornithischia]]ns,<ref name="Godefroit2014">{{cite journal | last1 = Godefroit | first1 = P. | last2 = Sinitsa | first2 = S.M. | last3 = Dhouailly | first3 = D. | last4 = Bolotsky | first4 = Y.L. | last5 = Sizov | first5 = A.V. | last6 = McNamara | first6 = M.E. | last7 = Benton | first7 = M.J. | last8 = Spagna | first8 = P. | year = 2014 | title = A Jurassic ornithischian dinosaur from Siberia with both feathers and scales | url = http://palaeo.gly.bris.ac.uk/Benton/reprints/2014Kulinda.pdf | journal = Science | volume = 345 | issue = 6195 | pages = 451–455 | doi = 10.1126/science.1253351 | pmid = 25061209 | bibcode = 2014Sci...345..451G | hdl = 1983/a7ae6dfb-55bf-4ca4-bd8b-a5ea5f323103 | s2cid = 206556907 | access-date = July 27, 2016 | archive-url = https://web.archive.org/web/20190209232112/http://palaeo.gly.bris.ac.uk/Benton/reprints/2014Kulinda.pdf | archive-date = February 9, 2019 }}</ref> and theropods,<ref name=Xuetal2004/> and primitive ceratopsians. Evidence for true, vaned feathers similar to the flight feathers of modern birds has been found only in the theropod subgroup Maniraptora, which includes oviraptorosaurs, troodontids, dromaeosaurids, and birds.<ref name=KP04/><ref name=GC06/> Feather-like structures known as [[Pterosaur#Pycnofibers|pycnofibre]]s have also been found in pterosaurs.<ref name=kellneretal2009>{{cite journal |last1=Kellner |first1=Alexander W. A. |author1-link=Alexander Kellner |last2=Wang |first2=Xiaolin |last3=Tischlinger |first3=Helmut |last4=Campos |first4=Diogenes de Almeida |last5=Hone |first5=David W. E. |last6=Meng |first6=Xi |display-authors=3 |year=2010 |title=The soft tissue of ''Jeholopterus'' (Pterosauria, Anurognathidae, Batrachognathinae) and the structure of the pterosaur wing membrane |journal=Proceedings of the Royal Society B |location=London |publisher=Royal Society |volume=277 |issue=1679 |pages=321–329 |doi=10.1098/rspb.2009.0846 |issn=0962-8452 |pmc=2842671 |pmid=19656798}}</ref>

However, researchers do not agree regarding whether these structures share a common origin between lineages (i.e., they are [[homology (biology)|homologous]]),<ref name="mayr2016">{{cite journal |last1=Mayr |first1=G. |last2=Pittman |first2=M. |last3=Saitta |first3=E. |last4=Kaye |first4=T.G. |last5=Vinther |first5=J. |year=2016 |title=Structure and homology of ''Psittacosaurus'' tail bristles |journal=Palaeontology |volume=59 |issue=6 |pages=793–802 |doi=10.1111/pala.12257|bibcode=2016Palgy..59..793M |hdl=1983/029c668f-08b9-45f6-a0c5-30ce9256e593 |s2cid=89156313|url=https://research-information.bris.ac.uk/en/publications/029c668f-08b9-45f6-a0c5-30ce9256e593 |hdl-access=free }}</ref><ref name="benton2019"/> or if they were the result of widespread experimentation with skin coverings among ornithodirans.<ref name="barrett2015">{{cite journal |last1=Barrett |first1=P.M. |last2=Evans |first2=D.C. |last3=Campione |first3=N.E. |year=2015 |title=Evolution of dinosaur epidermal structures |journal=Biology Letters |volume=11 |issue=6 |page=20150229 |doi=10.1098/rsbl.2015.0229 |pmc=4528472 |pmid=26041865}}</ref> If the former is the case, filaments may have been common in the ornithodiran lineage and evolved before the appearance of dinosaurs themselves.<ref name=switeknature/> Research into the genetics of [[American alligator]]s has revealed that crocodylian [[scute]]s do possess feather-keratins during embryonic development, but these keratins are not expressed by the animals before hatching.<ref name=AlibL2006>{{cite journal |last1=Alibardi |first1=Lorenzo |last2=Knapp |first2=Loren W. |last3=Sawyer |first3=Roger H. |year=2006 |title=Beta-keratin localization in developing alligator scales and feathers in relation to the development and evolution of feathers |journal=Journal of Submicroscopic Cytology and Pathology |location=[[Siena]] |publisher=Nuova Immagine Editrice |volume=38 |issue=2–3 |pages=175–192 |issn=1122-9497 |pmid=17784647}}</ref> The description of feathered dinosaurs has not been without controversy in general; perhaps the most vocal critics have been Alan Feduccia and Theagarten Lingham-Soliar, who have proposed that some purported feather-like fossils are the result of the decomposition of collagenous fiber that underlaid the dinosaurs' skin,<ref name=TLS03/><ref name=FLH05/><ref name=LSFX07/> and that maniraptoran dinosaurs with vaned feathers were not actually dinosaurs, but convergent with dinosaurs.<ref name=AF02/><ref name=FLH05/> However, their views have for the most part not been accepted by other researchers, to the point that the scientific nature of Feduccia's proposals has been questioned.<ref name=Prum2003/>

''[[Archaeopteryx]]'' was the first fossil found that revealed a potential connection between dinosaurs and birds. It is considered a [[transitional fossil]], in that it displays features of both groups. Brought to light just two years after [[Charles Darwin]]'s seminal ''[[On the Origin of Species]]'' (1859), its discovery spurred the nascent debate between proponents of [[evolutionary biology]] and [[creationism]]. This early bird is so dinosaur-like that, without a clear impression of feathers in the surrounding rock, at least one specimen was mistaken for the small theropod ''[[Compsognathus]]''.<ref name=PW88/> Since the 1990s, a number of additional feathered dinosaurs have been found, providing even stronger evidence of the close relationship between dinosaurs and modern birds. Many of these specimens were unearthed in the [[lagerstätten]] of the Jehol Biota.<ref name="benton2019">{{cite journal |last1=Benton |first1=M.J. |last2=Dhouailly |first2=D. |last3=Jiang |first3=B. |last4=McNamara |first4=M. |year=2019 |title=The Early Origin of Feathers |journal=Trends in Ecology & Evolution |volume=34 |issue=9 |pages=856–869 |doi=10.1016/j.tree.2019.04.018|pmid=31164250 |bibcode=2019TEcoE..34..856B |hdl=10468/8068 |s2cid=174811556 |hdl-access=free }}</ref> If feather-like structures were indeed widely present among non-avian dinosaurs, the lack of abundant fossil evidence for them may be due to the fact that delicate features like skin and feathers are seldom preserved by fossilization and thus often absent from the fossil record.<ref name="Schweitzeretal1999">{{cite journal |last1=Schweitzer |first1=Mary H. |last2=Watt |first2=J.A. |last3=Avci |first3=R. |last4=Knapp |first4=L. |last5=Chiappe |first5=L. |last6=Norell |first6=M. |last7=Marshall |first7=M. |display-authors=3 |year=1999 |title=Beta-keratin specific immunological reactivity in feather-like structures of the Cretaceous Alvarezsaurid, ''Shuvuuia deserti'' |journal=[[Journal of Experimental Zoology|Journal of Experimental Zoology Part B]] |location=Hoboken, NJ |publisher=Wiley-Blackwell |volume=285 |issue=2 |pages=146–157 |pmid=10440726 |doi=10.1002/(SICI)1097-010X(19990815)285:2<146::AID-JEZ7>3.0.CO;2-A |bibcode=1999JEZ...285..146S |issn=1552-5007}}</ref>