翼龍目：修订间差异

翼龍類的生理結構，因為飛行演化的需求，而與牠們祖先的生理結構有大幅差異。翼龍類的骨頭中空，內有空氣，類似現代[[鳥類]]的骨頭。牠們擁有隆脊狀[[胸骨]]，可讓飛行相關肌肉附著在上，還有加大的腦部，顯示出與飛行有關的特化特徵<ref name="Witmer_et_al_2003">{{en}}{{citeCite journal |authorlast=Witmer LM,|first=Lawrence M. |last2=Chatterjee S,|first2=Sankar |last3=Franzosa J,|first3=Jonathan |last4=Rowe T|first4=Timothy |date=2003-10 |title=Neuroanatomy of flying reptiles and implications for flight, posture and behaviour |url=http://www.nature.com/articles/nature02048 |journal=Nature |language=en |volume=425 |issue=6961 |pages=950–3 |pmid=14586467 |doi=10.1038/nature02048 |dateissn=October 20030028-0836}}</ref>。在某些較晚的翼龍類裡，肩膀部位的脊椎癒合成一節[[聯合背椎]]（Notarium，一種在鳥類與某些翼龍類肩膀出現的複合脊骨），可在飛行時使身體堅挺，並提供[[肩胛骨]]穩定的支撐。

翼龍類的翼膜由皮膚與其他軟組織構成，由不同形式的緊密纖維補強<ref name ="Bennett2000">{{en}}{{citeCite journal |authorlast=Bennett SC|first=S. Christopher |date=2000-01 |title=Pterosaur flight: theThe role of actinofibrils in wing function |url=http://www.tandfonline.com/doi/abs/10.1080/10292380009380572 |journal=Historical Biology |language=en |volume=14 |issue=4 |pages=255–284 |year=2000 |doi=10.1080/10292380009380572 |urlissn=http://www.informaworld.com/smpp/content~content=a907600799~db=all |access0891-date=2012-05-05 |archive-date=2020-04-06 |archive-url=https://web.archive.org/web/20200406123116/https://taylorandfrancis.com/ |dead-url=no 2963}}</ref>。翼膜連接至極長的第四手指與身體側面（或是後肢）之間。

過去的觀點認為，翼龍類的翼膜構造簡單，僅由皮膚構成。但現在的觀點認為，翼龍類的翼膜構造相當複雜，具有高度氣動性，適合主動飛行。翼膜是由一種排列緊密的強韌纖維所構成，名為「Actinofibrils」<ref name =Bennett2000/>。這種翼龍類專有的獨特纖維，以十字方式互相交錯、重疊。目前無法得知這種獨特纖維是由角質、肌肉、或者是具彈性物質所構成，因此也無法得知其實際功能。研究人員推測，這種纖維可能有使翼膜堅韌、或補強的作用<ref name="kellneretal2009">{{en}}Cite journal |last=Kellner, A.|first=Alexander W. A., |last2=Wang, X.,|first2=Xiaolin |last3=Tischlinger, H.,|first3=Helmut |last4=de Almeida Campos, D.,|first4=Diogenes |last5=Hone, D.|first5=David W. E. and |last6=Meng, X.|first6=Xi (2009).|date=2010-01-22 "|title=The soft tissue of ''Jeholopterus'' (Pterosauria, Anurognathidae, Batrachognathinae) and the structure of the pterosaur wing membrane |url=https://royalsocietypublishing."org/doi/10.1098/rspb.2009.0846 ''|journal=Proceedings of the Royal Society B'',: publishedBiological onlineSciences before|volume=277 print August 5, 2009,|issue=1679 |doi:=10.1098/rspb.2009.0846 |pmc=PMC2842671 |pmid=19656798}}</ref>。翼膜由皮膚、極薄的肌肉構成，由不同形式的緊密纖維補強，並具有複雜的[[血管]]系統<ref name="naish&martill2003">{{en}}{{cite journal |author=Naish D, Martill DM |year=2003 |title=Pterosaurs&nbsp; — a successful invasion of prehistoric skies |journal=Biologist |volume=50 |issue=5 |pages=213–6 |year=2003}}</ref>。

某些大型標本的翼部骨頭內有中空空間，證實某些翼龍類具有類似[[鳥類]]的[[呼吸系統]]。此外，根據至少一個標本的軟組織，顯示其呼吸系統延伸到翼膜內部<ref name="claessensetal2009">{{en}}{{citeCite journal |authorlast=Claessens LP, O'Connor PM, Unwin DM |titlefirst=RespiratoryLeon evolutionP. facilitatedA. the origin of pterosaur flight and aerial gigantismM. |journallast2=PLoS ONEO'Connor |volumefirst2=4Patrick M. |issuelast3=2Unwin |pagesfirst3=e4497David M. |yeardate=2009-02-18 |pmideditor-last=19223979Sereno |pmceditor-first=2637988Paul |doititle=10.1371/journal.pone.0004497Respiratory Evolution Facilitated the Origin of Pterosaur Flight and Aerial Gigantism |url=httphttps://wwwdx.plosoneplos.org/article/info%3Adoi%2F1010.1371%2Fjournal/journal.pone.0004497 |editor1-lastjournal=SerenoPLoS ONE |editor1-firstlanguage=Paulen |access-datevolume=2009-03-204 |archive-dateissue=2014-07-202 |archive-urldoi=https://web10.archive.org1371/web/20140720074511/http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournaljournal.pone.0004497 |deadissn=1932-url6203 |pmc=noPMC2637988 |pmid=19223979}}</ref>。

從手腕延伸出的[[翅骨]]（Pteroid），是一種翼龍類專有的骨頭，協助支撐手腕部到肩膀的前膜。化石證據顯示，前三根手指之間可能也連接者翼膜。因此，前膜的面積可能更大<ref name="naish&martill2003"/>。古生物學界對翅骨角度、位置的看法相當不同。[[大衛·安文]]等人認為，翅骨的角度往前，擴大前膜的面積<ref name="Wilkinson MT, Unwin DM, Ellington CP 2006 119–26">{{en}}{{citeCite journal |authorlast=Wilkinson MT,|first=Matthew T |last2=Unwin DM,|first2=David M |last3=Ellington CP|first3=Charles P |date=2006-01-07 |title=High lift function of the pteroid bone and forewing of pterosaurs |journalurl=Prochttps://royalsocietypublishing. Biolorg/doi/10. Sci1098/rspb.2005.3278 |volumejournal=273Proceedings |issue=1582of the Royal Society B: Biological Sciences |pageslanguage=119–26en |pmidvolume=16519243273 |pmcissue=15600001582 |doi=10.1098/rspb.2005.3278 |dateissn=January0962-8452 2006|pmc=PMC1560000 |pmid=16519243}}</ref>。但論點這是非常有爭議的。在2007年，[[克里斯·班尼特]]認為翅骨的角度朝向身體，而非朝前，如同傳統的看法<ref>{{en}}{{citeCite journal |authorlast=Bennett SC|first=S. Christopher |date=2007-12-12 |title=Articulation and Functionfunction of the Pteroidpteroid Bonebone of Pterosaurspterosaurs |url=http://www.tandfonline.com/doi/abs/10.1671/0272-4634%282007%2927%5B881%3AAAFOTP%5D2.0.CO%3B2 |journal=Journal of Vertebrate Paleontology |language=en |volume=27 |issue=4 |pages=881–91 |year=2007 |doi=10.1671/0272-4634(2007)27[881:AAFOTP]2.0.CO;2 |url=http://www.bioone.org/perlserv/?request=get-abstract&doi=10.1671%2F0272-4634(2007)27%5B881%3AAAFOTP%5D2.0.CO%3B2 |issn=0272-4634}}</ref>。根據組織學、個體生長學、形態學等層面的證據，皆顯示翅骨本身是個骨頭，而非骨化的軟骨。古生物學界對於翅骨的起源還沒有定論，目前有：從[[腕骨]]延伸出、第一[[掌骨]]延伸而出、或是新演化的骨頭…等說法<ref name="Unwinetal1996">{{en}}{{citeCite journal |doi=10.1098/rspb.1996.0008 |last=Unwin |first=D. M. |coauthors=Frey, E., Martill, D. M., Clarke, J. B., and Riess, J. |yeardate=1996-01-22 |title=On the nature of the pteroid in pterosaurs |url=https://royalsocietypublishing.org/doi/10.1098/rspb.1996.0008 |journal=Proceedings of the Royal Society of London. Series B: Biological Sciences |language=en |volume=263 |issue=1366 |pagesdoi=45–5210.1098/rspb.1996.0008 |issn=0962-8452}}</ref>。

翼龍類的手腕有兩塊近側[[腕骨]]、四塊末側腕骨（不計算翅骨的狀況），顯示牠們的手腕經過明顯特化過程。在成年個體標本，這兩塊近側腕骨癒合成一塊，而其中三塊末側腕骨癒合成一塊。唯一未癒合的腕骨位於手腕中間，位於末側腕骨、翅骨之間，連接至末側腕骨的垂直突出面，另一側則是以凹處連接翅骨<ref name="wilkinsonetal2006">{{en}}{{citeCite journal |last=Wilkinson author |first=Matthew Wilkinson M.T., |last2=Unwin D.|first2=David M., |last3=Ellington C.P. |first3=Charles yearP |date= 2006-01-07 | title = High lift function of the pteroid bone and forewing of pterosaurs | url =https://royalsocietypublishing.org/doi/10.1098/rspb.2005.3278 | journal = Proceedings of the Royal Society B: Biological Sciences |language=en |volume = 273 | issue = 1582| pages = 119–126 | doi = 10.1098/rspb.2005.3278 | pmidissn=165192430962-8452 | pmc=PMC1560000 |pmid= 156000016519243}}</ref>。

古生物學家們對於臂膜是否也連接到後肢，連接至後肢的哪個部位，目前還沒有定論。[[喙嘴翼龍類]]的[[索德斯龍]]<ref name="Unwin_Bakhurina_1994">{{en}}{{citeCite journal |authorlast=Unwin DM,|first=David M. |last2=Bakhurina NN|first2=Natasha N. |date=1994-09 |title=''Sordes pilosus'' and the nature of the pterosaur flight apparatus |url=http://www.nature.com/articles/371062a0 |journal=Nature |language=en |volume=371 |issue= 6492|pages=62–4 |year=1994 |doi=10.1038/371062a0 |issn=0028-0836}}</ref>、[[蛙嘴龍科]]的[[熱河翼龍]]<ref>{{en}}{{citeCite journal |authorlast=Wang X,|first=Xiaolin Zhou Z, Zhang F, Xu X|date=2002 |title=A nearly completely articulated rhamphorhynchoid pterosaur with exceptionally well-preserved wing membranes and "?hairs"? from Inner Mongolia, northeast China |url=http://www.scichina.com/ky/0203/ky0226.stm |journal=Chinese Science Bulletin |language=en |volume=47 |pageissue=3 |year=2002 |issn=1001-6538 |doi=10.1360/02tb9054 |issueissn=31001-6538}}</ref>、還有[[桑塔納岩層]]發現的某種翼手龍類化石，證實至少某些物種的翼膜有連接至後肢<ref>{{en}}Cite journal |last=Frey et|first=Eberhard |last2=Tischlinger |first2=Helmut |last3=Buchy |first3=Marie-Céline |last4=Martill |first4=David alM., (|date=2003)-01 |title=New specimens of Pterosauria (Reptilia) with soft parts with implications for pterosaurian anatomy and locomotion ''|url=https://www.lyellcollection.org/doi/10.1144/GSL.SP.2003.217.01.14 |journal=Geological Society, London, Special Publications'' |language=en |volume=217 |issue=1 |doi=10.1144/GSL.SP.2003.217.01.14 |issn=0305-8719}}</ref>。然而，現代[[蝙蝠]]與[[飛鼠]]翼膜的連接方式上有相當大的不同，而不同種類的翼龍類可能也有不同的翼膜連接方式。研究顯示翼龍類的四肢比例有相當大的不同，可能反映了不同的翼展方式<ref>{{en}}{{citeCite journal |authorlast=Dyke GJ,|first=G. J. |last2=Nudds RL,|first2=R. L. |last3=Rayner JM|first3=J. M. V. |date=2006-07 |title=Limb disparity and wing shape in pterosaurs |journalurl=Jhttps://onlinelibrary. Evolwiley. Biolcom/doi/10.1111/j.1420-9101.2006.01096.x |volumejournal=19Journal of Evolutionary Biology |issuelanguage=4en |pagesvolume=1339–4219 |pmidissue=167805344 |doi=10.1111/j.1420-9101.2006.01096.x |dateissn=July 20061010-061X}}</ref>。

大部分翼龍類具有修長的口鼻部。許多翼龍類的嘴部佈滿針狀牙齒；而某些衍化物種則沒有牙齒，具有類似現代[[鳥類]]的狹長喙狀嘴，例如[[無齒翼龍科]]、[[神龍翼龍科]]<ref name="DU06b">{{cite book |last=Unwin |first=David M. |title=The Pterosaurs: From Deep Time |url=https://archive.org/details/pterosaursfromde00unwi |year=2006 |publisher=Pi Press |location=New York |isbn=978-0-13-146308-0 |page=[https://archive.org/details/pterosaursfromde00unwi/page/246 246]}}</ref>。某些標本的喙狀嘴則保存了[[角質]]組織<ref name="frey&martill1998">{{en}}{{citeCite journal |authorlast=Frey E,|first=Eberhard |last2=Martill DM|first2=David M. |date=1998-12-22 |title=Soft tissue preservation in a specimen of ''Pterodactylus kochi'' (Wagner) from the Upper Jurassic of Germany |url=http://www.schweizerbart.de/papers/njgpa/detail/210/88437/Soft_tissue_preservation_in_a_specimen_of_Pterodac?af=crossref |journal=Neues Jahrbuch fu ̈rfür Geologie und PalaPaläontologie ̈ontologie,- Abhandlungen |language=en |volume=210 |issue=3 |pagesdoi=421–4110.1127/njgpa/210/1998/421 |yearissn=19980077-7749}}</ref>。

自從1990年代以來的新發現化石與詳細研究，發現翼龍類普遍具有頭冠，這與過去的觀點不同。翼龍類的頭冠主要由角質組織構成，甚至是全部，因此很少在[[化石]]化過程中保存下來<ref name="naish&martill2003"/>。科學家藉由[[紫外線]]攝像技術，檢驗出[[翼手喙龍]]與[[翼手龍屬]]的化石也具有頭冠，而過去沒有被發現<ref name="frey&martill1998"/><ref name="CJ02">{{en}}Czerkas, S.A., and Ji, Q. (2002). A new rhamphorhynchoid with a headcrest and complex integumentary structures. In: Czerkas, S.J. (Ed.). ''Feathered Dinosaurs and the Origin of Flight''. The Dinosaur Museum:Blanding, Utah, 15-41. ISBN 978-1-932075-01-4.</ref>。根據過去的理論，只有衍化的[[翼手龍類]]具有頭冠；而近年發現的翼手喙龍、[[奧地利翼龍]]也具有頭冠，證實部分[[喙嘴翼龍類]]也具有頭冠<ref name="naish&martill2003"/>。

翼龍類並沒有發現羽毛證據，但至少部份翼龍類覆蓋者類似毛的絲狀結構，類似[[哺乳动物|哺乳類]]的毛髮，但非[[同源演化]]的結果。翼龍類的毛不同於哺乳類的毛髮，而是獨特的結構，兩者為[[趨同演化]]的後果。雖然在有些研究裡，翼膜上的纖維被誤認為毛，而有些化石的頭部與身體上的確有絲狀結構物痕跡，例如[[索德斯龍]]、[[熱河翼龍]]<ref name="Unwin_Bakhurina_1994" />。翼龍類的毛不類似現今[[蝙蝠]]的毛髮，這是另一個趨同演化的例子。翼龍類演化出毛，是基於飛行的需求，也顯示翼龍類是[[恒温动物|溫血動物]]。

大部分的脊椎動物是[[趾行動物]]，行走時以腳趾接觸地面，腳踝不接觸地面；從足跡化石顯示，翼龍類行走時以腳掌接觸地面，類似[[人類]]與[[熊]]，都屬於[[蹠行動物]]。[[神龍翼龍科]]的足跡化石顯示，至少有部分翼龍類行走時採取後肢直立步態，而非往後肢兩側延展的步態<ref name="witton&naish2008">{{en}}{{citeCite journal |authorlast=Witton MP, Naish D |titlefirst=AMark reappraisal of azhdarchid pterosaur functional morphology and paleoecologyP. |journallast2=PLoS ONENaish |volumefirst2=3Darren |issuedate=52008-05-28 |pageseditor-last=e2271McClain |yeareditor-first=2008Craig |pmc=2386974R. |doititle=10.1371/journal.pone.0002271A Reappraisal of Azhdarchid Pterosaur Functional Morphology and Paleoecology |url=httphttps://wwwdx.plosoneplos.org/article/info%3Adoi%2F1010.1371%2Fjournal/journal.pone.0002271 |pmidjournal=18509539PLoS |editor1-last=McClainONE |editor1-firstlanguage=Craig R.en |access-datevolume=2008-10-213 |archive-dateissue=2014-12-175 |archive-urldoi=https://web.archive.org/web/20141217215315/http://www.plosone.org/article/info:doi/10.1371/journal.pone.0002271 |deadissn=1932-url6203 |pmc=noPMC2386974 |pmid=18509539}}</ref>。