Editing Pteranodon (section)

===Crest function===
''Pteranodon'' was notable for its skull crest, though the function of this crest has been a subject of debate. Most explanations have focused on the blade-like, backward pointed crest of male ''P. longiceps'', however, and ignored the wide range of variation across age and sex. The fact that the crests vary so much rules out most practical functions other than for use in mating displays.<ref>{{Cite journal | last1 = Tomkins | first1 = J. L. | last2 = Lebas | first2 = N. R. | last3 = Witton | first3 = M. P. | last4 = Martill | first4 = D. M. | last5 = Humphries | first5 = S. | title = Positive Allometry and the Prehistory of Sexual Selection | journal = The American Naturalist | volume = 176 | issue = 2 | pages = 141–148 | year = 2010 | pmid = 20565262 | doi = 10.1086/653001 | bibcode = 2010ANat..176..141T | s2cid = 36207 | url = http://eprints.lincoln.ac.uk/15259/1/__ddat02_staffhome_jpartridge_653001.pdf | access-date = 2018-08-06 | archive-date = 2017-08-09 | archive-url = https://web.archive.org/web/20170809073819/http://eprints.lincoln.ac.uk/15259/1/__ddat02_staffhome_jpartridge_653001.pdf | url-status = dead }}</ref> Therefore, display was probably the main function of the crest, and any other functions were secondary.<ref name=bennett1992/>

Scientific interpretations of the crest's function began in 1910, when George Francis Eaton proposed two possibilities: an aerodynamic counterbalance and a muscle attachment point. He suggested that the crest might have anchored large, long jaw muscles, but admitted that this function alone could not explain the large size of some crests.<ref name=eaton1910>Eaton, G.F. (1910). "Osteology of ''Pteranodon''." ''Memoirs of the Connecticut Academy of Arts and Sciences'', '''2''':1–38, pls. i–xxxi.</ref> Bennett (1992) agreed with Eaton's own assessment that the crest was too large and variable to have been a muscle attachment site.<ref name=bennett1992/> Eaton had suggested that a secondary function of the crest might have been as a counterbalance against the long beak, reducing the need for heavy neck muscles to control the orientation of the head.<ref name=eaton1910/> Wind tunnel tests showed that the crest did function as an effective counterbalance to a degree, but Bennett noted that, again, the hypothesis focuses only on the long crests of male ''P. longiceps'', not on the larger crests of ''P. sternbergi'' and very small crests that existed among the females. Bennett found that the crests of females had no counterbalancing effect, and that the crests of male ''P. sternbergi'' would, by themselves, have a negative effect on the balance of the head. In fact, side to side movement of the crests would have required more, not less, neck musculature to control balance.<ref name=bennett1992/>[[File:Pteranodon longiceps skulls.jpg|thumb|Putative male ''Pteranodon longiceps'' specimens YPM 2594 and 2493]]

In 1943, Dominik von Kripp suggested that the crest may have served as a [[rudder]], an idea embraced by several later researchers.<ref name=bennett1992/><ref name=kripp1943>von Kripp, D. (1943). "Ein Lebensbild von ''Pteranodon ingens'' auf flugtechnischer Grundlage." ''Nova Acta Leopoldina, N.F.'', '''12'''(83): 16–32 [in German].</ref> One researcher, Ross S. Stein, even suggested that the crest may have supported a membrane of skin connecting the backward-pointing crest to the neck and back, increasing its surface area and effectiveness as a rudder.<ref name=stein1975>{{Cite journal | author = Stein, R.S. | year = 1975 | title = Dynamic analysis of ''Pteranodon ingens'': a reptilian adaptation to flight | journal = Journal of Paleontology | volume = 49 | pages = 534–548}}</ref> The rudder hypothesis, again, does not take into account females nor ''P. sternbergi'', which had an upward-pointing, not backward-pointing crest. Bennett also found that, even in its capacity as a rudder, the crest would not provide nearly so much directional force as simply maneuvering the wings. The suggestion that the crest was an air brake, and that the animals would turn their heads to the side in order to slow down, suffers from a similar problem.<ref name=bramwell>Bramwell, C.D. and Whitfield, G.R. (1974). "Biomechanics of Pteranodon." ''Philosophical Transactions Royal Society B'', '''267'''.</ref> Additionally, the rudder and air brake hypotheses do not explain why such large variation exists in crest size even among adults.<ref name=bennett1992/>

[[Alexander Kellner]] suggested that the large crests of the pterosaur ''[[Tapejara (pterosaur)|Tapejara]]'', as well as other species, might be used for heat exchange, allowing these pterosaurs to absorb or shed heat and regulate body temperature, which also would account for the correlation between crest size and body size. There is no evidence of extra blood vessels in the crest for this purpose, however, and the large, membranous wings filled with blood vessels would have served that purpose much more effectively.<ref name=bennett1992/>

With these hypotheses ruled out, the best-supported hypothesis for crest function seems to be as a sexual display. This is consistent with the size variation seen in fossil specimens, where females and juveniles have small crests and males large, elaborate, variable crests.<ref name=bennett1992/>