page_title: Pteranodon
section_title: Crest function
hierarchical_section_title: Pteranodon / Paleobiology / Crest function
caption_attribution_description: Photos of Pteranodon longiceps specimens YPM 2594 and 2493 from Eaton (1910). Image and text has been reflipped, as description on website states the images were flipped.
context_page_description: Pteranodon is a genus of pterosaur that included some of the largest known flying reptiles, with wingspans over 7 meters. They lived during the late Cretaceous geological period of North America in present-day Kansas, Alabama, Nebraska, Wyoming, and South Dakota. More fossil specimens of Pteranodon have been found than any other pterosaur, with about 1,200 specimens known to science, many of them well preserved with nearly complete skulls and articulated skeletons. It was an important part of the animal community in the Western Interior Seaway.
  Pteranodon was a pterosaur, meaning that it is not a dinosaur. By definition, all dinosaurs belong to one of the two groups within Dinosauria, i.e. Saurischia or Ornithischia. As such, this excludes pterosaurs. Nonetheless, Pteranodon is frequently featured in dinosaur media and are strongly associated with dinosaurs by the general public. While not dinosaurs, pterosaurs such as Pteranodon form a clade closely related to dinosaurs as both fall within the clade Avemetatarsalia.
context_section_description: 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. Therefore, display was probably the main function of the crest, and any other functions were secondary.
  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. Bennett (1992) agreed with Eaton's own assessment that the crest was too large and variable to have been a muscle attachment site. 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. 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.
  In 1943, Dominik von Kripp suggested that the crest may have served as a rudder, an idea embraced by several later researchers. 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. 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. Additionally, the rudder and air brake hypotheses do not explain why such large variation exists in crest size even among adults.
  Alexander Kellner suggested that the large crests of the 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.
  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.
caption: Putative male Pteranodon longiceps specimens YPM 2594 and 2493
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