Editing Feather (section)

=== Functional considerations ===
The functional view on the evolution of feathers has traditionally focused on insulation, flight and display. Discoveries of non-flying Late Cretaceous feathered dinosaurs in China,<ref name="NYT-20161208">{{cite news |last=St. Fleur |first=Nicholas |title=That Thing With Feathers Trapped in Amber? It Was a Dinosaur Tail |url=https://www.nytimes.com/2016/12/08/science/dinosaur-feathers-amber.html |date=8 December 2016 |work=[[The New York Times]] |access-date=8 December 2016 |url-status=live |archive-url=https://web.archive.org/web/20161208224540/http://www.nytimes.com/2016/12/08/science/dinosaur-feathers-amber.html |archive-date=8 December 2016 }}</ref> however, suggest that flight could not have been the original primary function as the feathers simply would not have been capable of providing any form of lift.<ref name="sumida">{{Cite journal|author1=Sumida, SS|author2=CA Brochu|year=2000|title=Phylogenetic context for the origin of feathers|doi=10.1093/icb/40.4.486|journal=American Zoologist|volume=40|issue=4|pages=486–503|doi-access=free}}</ref><ref>{{Cite journal|author1=Dimond, C. C. |author2=R. J. Cabin |author3=J. S. Brooks |journal=BIOS|title=Feathers, Dinosaurs, and Behavioral Cues: Defining the Visual Display Hypothesis for the Adaptive Function of Feathers in Non-Avian Theropods | volume=82|year=2011|pages=58–63 | doi=10.1893/011.082.0302|issue=3|s2cid=98221211}}</ref> There have been suggestions that feathers may have had their original function in thermoregulation, waterproofing, or even as sinks for metabolic wastes such as sulphur.<ref>{{cite journal| title= Explanatory History of the Origin of Feathers|author=Bock, WJ|year=2000| journal= Am. Zool.|volume=40 |issue=4|pages=478–485 |doi=10.1093/icb/40.4.478|doi-access=free}}</ref> [[Yutyrannus|Recent discoveries]] are argued to support a thermoregulatory function, at least in smaller dinosaurs.<ref>{{Cite journal |date=4 April 2012 |author=Whitfield, John |title=Largest feathered dinosaur yet discovered in China |journal=Nature News Blog |url=http://blogs.nature.com/news/2012/04/largest-feathered-dinosaur-discovered-in-china.html |access-date=4 April 2012 |url-status=live |archive-url=https://web.archive.org/web/20120406145618/http://blogs.nature.com/news/2012/04/largest-feathered-dinosaur-discovered-in-china.html |archive-date=6 April 2012 }}</ref><ref name="yutyrannus">{{cite journal |author1=Xu X. |author2=Wang K. |author3=Zhang K. |author4=Ma Q. |author5=Xing L. |author6=Sullivan C. |author7=Hu D. |author8=Cheng S. |author9=Wang S. |year=2012 |title=A gigantic feathered dinosaur from the Lower Cretaceous of China |url=http://www.xinglida.net/pdf/Xu_et_al_2012_Yutyrannus.pdf |journal=Nature |volume=484 |issue=7392 |pages=92–95 |doi=10.1038/nature10906 |pmid=22481363 |bibcode=2012Natur.484...92X |s2cid=29689629 |display-authors=etal |archive-url=https://web.archive.org/web/20120417134949/http://www.xinglida.net/pdf/Xu_et_al_2012_Yutyrannus.pdf |archive-date=17 April 2012 }}</ref> Some researchers even argue that thermoregulation arose from bristles on the face that were used as tactile sensors.<ref>{{Cite journal|last1=Persons|first1=Walter S.|last2=Currie|first2=Philip J.|date=2015|title=Bristles before down: A new perspective on the functional origin of feathers|journal=Evolution|language=en|volume=69|issue=4|pages=857–862|doi=10.1111/evo.12634|issn=1558-5646|pmid=25756292|s2cid=24319963|doi-access=free}}</ref> While feathers have been suggested as having evolved from reptilian [[scale (zoology)|scales]], there are numerous objections to that idea, and more recent explanations have arisen from the paradigm of [[evolutionary developmental biology]].<ref name="Prum2003" /> Theories of the scale-based origins of feathers suggest that the planar scale structure was modified for development into feathers by splitting to form the webbing; however, that developmental process involves a tubular structure arising from a follicle and the tube splitting longitudinally to form the webbing.<ref name="Prum2002" /><ref name="Prum2003" /> The number of feathers per unit area of skin is higher in smaller birds than in larger birds, and this trend points to their important role in thermal insulation, since smaller birds lose more heat due to the relatively larger surface area in proportion to their body weight.<ref name="pettingill" /> The miniaturization of birds also played a role in the evolution of powered flight.<ref>{{Cite journal|author1=De Ricqles |author2=A. J. |author3=K. Padian |author4=J. R. Horner |author5=E. T. Lamm |author6=N. Myhrvold |year=2003|title=Osteohistology of confuciusornis sanctus (theropoda: Aves)|journal=Journal of Vertebrate Paleontology|volume=23|issue=2 |pages=373–386|doi=10.1671/0272-4634(2003)023[0373:oocsta]2.0.co;2 |s2cid=84936431 }}</ref> The coloration of feathers is believed to have evolved primarily in response to [[sexual selection]]. In fossil specimens of the [[Paraves|paravian]] ''[[Anchiornis huxleyi]]'' and the [[pterosaur]] ''[[Tupandactylus imperator]]'', the features are so well preserved that the [[melanosome]] (pigment cells) structure can be observed. By comparing the shape of the fossil melanosomes to melanosomes from extant birds, the color and pattern of the feathers on ''Anchiornis'' and ''Tupandactylus'' could be determined.<ref>{{cite journal|last1=Li|first1=Quanguo|last2=Gao|first2=Ke-Qin|last3=Vinther|first3=Jakob|last4=Shawkey|first4=Matthew|last5=Clarke|first5=Julia|last6=D'Alba|first6=Liliana|last7=Meng|first7=Qingjin|last8=Briggs|first8=Derek|last9=Prum|first9=Richard|title=Plumage Color Patterns of an Extinct Dinosaur|journal=Science|date=12 March 2010|volume=327|issue=5971|pages=1369–1372|doi=10.1126/science.1186290|pmid=20133521|bibcode = 2010Sci...327.1369L |s2cid=206525132|url=http://doc.rero.ch/record/210394/files/PAL_E4402.pdf}}</ref><ref>Cincotta, A., Nicolaï, M., Campos, H.B.N. et al. Pterosaur melanosomes support signalling functions for early feathers. Nature 604, 684–688 (2022). {{doi|10.1038/s41586-022-04622-3}}.</ref> ''Anchiornis'' was found to have black-and-white-patterned feathers on the forelimbs and hindlimbs, with a reddish-brown crest. This pattern is similar to the coloration of many extant bird species, which use plumage coloration for display and communication, including sexual selection and camouflage. It is likely that non-avian dinosaur species utilized plumage patterns for similar functions as modern birds before the origin of flight. In many cases, the physiological condition of the birds (especially males) is indicated by the quality of their feathers, and this is used (by the females) in [[mate choice]].<ref>{{Cite journal|author1=Saino, Nicola |author2=Riccardo Stradi|s2cid=4400888|year=1999|title=Carotenoid Plasma Concentration, Immune Profile, and Plumage Ornamentation of Male Barn Swallows|journal=American Naturalist|volume=154|issue=4|pages=441–448|doi=10.1086/303246|pmid=10523490}}</ref><ref>{{Cite journal|author1=Endler, John A. |author2=David A. Westcott |author3= Joah R. Madden |author4=Tim Robson |author5= Patrick Phillips  |name-list-style=amp |year=2005|title=Animal visual systems and the evolution of color patterns: Sensory processing illumiates signal evolution|journal=Evolution|volume=59|issue=8|pages=1795–1818|pmid=16329248|doi=10.1111/j.0014-3820.2005.tb01827.x|s2cid=25683790 |doi-access=free}}</ref> Additionally, when comparing different ''[[Ornithomimus|Ornithomimus edmontonicus]]'' specimens, older individuals were found to have a pennibrachium (a wing-like structure consisting of elongate feathers), while younger ones did not. This suggests that the pennibrachium was a secondary sex characteristic and likely had a sexual function.<ref>{{Cite journal|last1=Zelenitsky|first1=D. K.|last2=Therrien|first2=F.|last3=Erickson|first3=G. M.|last4=DeBuhr|first4=C. L.|last5=Kobayashi|first5=Y.|last6=Eberth|first6=D. A.|last7=Hadfield|first7=F.|date=2012-10-26|title=Feathered Non-Avian Dinosaurs from North America Provide Insight into Wing Origins|journal=Science|language=en|volume=338|issue=6106|pages=510–514|doi=10.1126/science.1225376|pmid=23112330|issn=0036-8075|bibcode=2012Sci...338..510Z|s2cid=2057698}}</ref>