Editing Quetzalcoatlus (section)

===Skull===
[[Image:Quetzskullswittonnaish2008.png|thumb|Skull reconstruction of ''Q. lawsoni'']]Complete skulls are not known from either ''Quetzalcoatlus'' species. Reconstructions of its skull anatomy must therefore draw from eight separate ''Q. lawsoni'' specimens which preserve skull elements. Based on the length of the mandible (lower jaw), the skull of ''Q. lawsoni'' likely measured about {{Convert|94–96|cm|in|abbr=on}} in length.<ref name="andres2021" /><ref name="kellner&langston1996" /> The distance between the [[Condyloid process|condyloid]] (articular) processes of the mandible is around {{Convert|13|cm|in|abbr=on}}.<ref name="padian2021" /> The ratio between the length of the skull and the length of the average dorsal (back) vertebra is very high in ''Q. lawsoni'', and is surpassed only by ''Pteranodon'' and ''[[Tupuxuara]]''.<ref name="andres2021" /> The nasoantorbital [[fenestra]], a massive opening found in many pterosaurs which combined the [[nasal cavity]] (which housed the external nostril) and [[antorbital fenestra]], was very large in ''Q. lawsoni'', occupying about a third of the total length of the skull.<ref name="andres2021" /><ref name="kellner&langston1996" /> In the largest specimen, TMM 41961-1.1, it measured {{Convert|34.7|cm|in|abbr=on}} in length and {{Convert|10.45|cm|in|abbr=on}} in height. ''Q. lawsoni''<nowiki/>'s [[choana]]e (internal nostrils) were [[wikt:confluent|confluent]] and anteriorly expanded, meaning that they were essentially fused and expanded towards the front. The orbit was small and [[wikt:obovate|obovate]], resembling an inverted egg in shape.<ref name="andres2021" /> It was fairly low on the skull, similar to other azhdarchoids, like [[Tapejaridae|tapejarids]].<ref name="kellner&langston1996" /> Like in other pterosaurs, the orbit was positioned in a way that would have allowed ''Quetzalcoatlus'' to see both forwards and directly to the sides, giving it a degree of [[Stereopsis|stereoscopic vision]].<ref name="padian2021" />

Like other azhdarchids, ''Quetzalcoatlus'' had a long, slender, toothless beak,<ref name="andres2021" /><ref name="kellner&langston1996" /> with a gape of around 52 degrees.<ref name="kellner&langston1996" /> It was constructed from the premaxilla and [[maxilla]] on the upper jaw,<ref name="andres2021" /> and the [[Mandible|dentary]] on the lower jaw.<ref name="kellner&langston1996" /> Beak tips are not preserved in any specimen, so it is not clear whether its tip was sharp or had some other morphology, such as a keel. The dentary had a slight [[wikt:sinusoidal|sinusoidal]] curve, which is also observed in ''[[Hatzegopteryx]]''.<ref name="andres2021" /> The [[mandibular symphysis|mandibular symphyses]] would have widened slightly as the jaw opened, slightly separating the mandibles, which has led to suggestions that some sort of [[Gular skin|gular pouch]] was present.<ref name="andres2021" /><ref name="kellner&langston1996" /> At the base of the beak, formed from the [[premaxilla]], was a crest, referred to by some authors as a [[sagittal crest]].<ref name="andres2021" /><ref name="kellner&langston1996" /> A premaxillary crest is also observed in ''Wellnhopterus'', though is smaller and more anterior. The exact form of the crest in ''Q. lawsoni'' has yet to be determined, due to the poor preservation of the rear half of ''Q. lawsoni''{{'}}s skull. From what is known, two distinct [[Polymorphism (biology)|morphotypes]] have been suggested: one with a square sagittal crest and a tall nasoantorbital [[fenestra]], and one with a more semicircular sagittal crest and a shorter nasoantorbital fenestra. Additionally, one morphotype is larger than the other, and has a proportionally shorter beak. Despite their differences, both share the diagnostic traits of ''Q. lawsoni'', and are considered the same species. The reason for there being two morphotypes is unclear, though it may correlate to individual variation, [[ontogeny]], or [[sexual dimorphism]].<ref name="andres2021" />