Editing Quetzalcoatlus (section)

=== Skeleton ===
[[File:Azhdarchid pterosaur neck lengths.png|left|thumb|300x300px|Neck lengths of various azhdarchids. ''Q. sp.'' is now ''Q. lawsoni''.]]
Like other pterosaurs, ''Quetzalcoatlus'' had light, hollow bones, supported internally by struts called [[trabecula]]e. The neck of ''Q. lawsoni'', measured from the third [[Cervical vertebrae|cervical]] (neck) [[vertebra]] to the seventh, has been estimated at {{Convert|149.5|cm|in|abbr=on}}.<ref name=":0" /> It consisted of nine elongated vertebrae, which were [[wikt:procoelous|procoelous]], meaning that they were concave at the front.<ref name="andres2021" /> All of them were compressed [[Anatomical terms of location|dorsoventrally]] (top to bottom), and were better suited for dorsoventral motion than [[Anatomical terms of location|lateral]] (side-to-side) motion. However, the lateral range of motion was still extensive, and the neck and head could swing left and right in an arc of about 180 degrees.<ref name="padian2021" /><ref name="padian1983">{{Cite journal|author=Padian, K.|year=1983|title=A functional analysis of flying and walking in pterosaurs|journal=Paleobiology|volume=9|issue=3|pages=218–239|doi=10.1017/S009483730000765X|bibcode=1983Pbio....9..218P|s2cid=88434056}}</ref> Like in other azhdarchoids, the cervical vertebrae were low, with [[Vertebra|neural arches]] that were essentially inside the [[Vertebra|centrum]].<ref name=":1" /> In most azhdarchids, the [[Vertebra|neural spine]] of the seventh cervical vertebra was fairly long. This was not the case in ''Q. lawsoni'', where the neural spine was shorter.<ref name="andres2021" /> Internally, the cervical vertebrae were supported by trabeculae that increased their buckling load substantially (about 90%). This may have been an adaptation for counteracting [[shear force]]s exerted on the neck while in flight, though may have also enabled [[Agonistic behaviour|agonistic]] neck-bashing behaviors like those seen in [[giraffe]]s.<ref name=":2">{{Cite journal |last1=Williams |first1=Cariad J. |last2=Pani |first2=Martino |last3=Bucchi |first3=Andrea |last4=Smith |first4=Roy E. |last5=Kao |first5=Alexander |last6=Keeble |first6=William |last7=Ibrahim |first7=Nizar |last8=Martill |first8=David M. |date=April 23, 2021 |title=Helically arranged cross struts in azhdarchid pterosaur cervical vertebrae and their biomechanical implications |journal=iScience |volume=24 |issue=4 |pages=102338 |doi=10.1016/j.isci.2021.102338 |pmid=33997669 |pmc=8101050 |bibcode=2021iSci...24j2338W |issn=2589-0042}}</ref> While airborne, the neck of ''Q. northropi'' would have likely assumed a slight S-shaped curve, similar to swans.<ref name="padian2021" /> Similar to other azhdarchids, the torso was proportionally small, about half as long again as the [[humerus]].<ref name=":1" /><ref name="CW942">{{Cite journal |last1=Cai, Z. |last2=Wei, F. |name-list-style=amp |year=1994 |title=On a new pterosaur (''Zhejiangopterus linhaiensis'' gen. et sp. nov.) from Upper Cretaceous in Linhai, Zhejiang, China |url=http://paleoglot.org/files/Cai&Wei_94.pdf |journal=Vertebrata PalAsiatica |volume=32 |pages=181–194}}</ref> In ''Quetzalcoatlus'' specifically, the vertebrae at the base of the neck and the [[Shoulder girdle|pectoral girdle]] (shoulder girdle) are poorly known. The first four [[Dorsal vertebra|dorsal]] (back) vertebrae are fused into a [[notarium]],<ref name="andres2021" /> as in some other pterosaurs and birds,<ref>{{Cite journal |last1=Aires |first1=Alex Schiller |last2=Reichert |first2=Leici Machado |last3=Müller |first3=Rodrigo Temp |last4=Pinheiro |first4=Felipe Lima |last5=Andrade |first5=Marco Brandalise |date=2021 |title=Development and evolution of the notarium in Pterosauria |journal=Journal of Anatomy |language=en |volume=238 |issue=2 |pages=400–415 |doi=10.1111/joa.13319 |issn=0021-8782 |pmc=7812132 |pmid=33026119}}</ref> particularly ornithocheiroids.<ref name="andres2021" /> The vertebral count of the notarium is unlike ''[[Zhejiangopterus]]'', which had six notarial vertebrae, but like ''[[Azhdarcho]]''. Most other dorsal vertebrae are absent, except for three which had been integrated into the [[sacrum]]. Around seven dorsal vertebrae were free of the notarium and sacrum. Four true sacral vertebrae are preserved, though there were likely seven in all. No [[Tail|caudal]] (tail) vertebrae are preserved.<ref name="padian2021" />[[File:Pone.0013982.g003.png|thumb|250x250px|Holotype humerus of ''Q. northropi'' (A), alongside the humeri of ''Pteranodon'' (B) and ''Pterodactylus'' (C). The first two scale bars are 100 mm, whilst the third is 10 mm.]]
''Quetzalcoatlus''<nowiki/>' [[scapulocoracoid]], a fusion of the [[scapula]] and [[coracoid]], bones, was U-shaped and broad. Throughout azhdarchid evolution, the scapula had been reducing in length, and this reached its pinnacle in ''Q. lawsoni'', where the scapula was only slightly longer than the coracoid. The [[sternum]], like that of other pterosaurs, was broad. It had a transverse ridge on its posterior (rear) portion, also observed in ''Pteranodon'', albeit it is further forward in that genus.<ref name="andres2021" /> Like other pterosaurs, the bone walls of the sternum were very thin, and in the case of ''Q. lawsoni'', they were as little as {{Convert|1.5|mm|in|abbr=on}} thick.<ref>{{Cite journal |last=Hone |first=David W. E. |date=April 15, 2023 |title=The anatomy and diversity of the pterosaurian sternum |url=https://palaeo-electronica.org/content/2023/3813-the-sternum-of-pterosaurs |access-date=February 2, 2025 |journal=Palaeontologia Electronica |language=en |doi=10.26879/1261|doi-access=free }}</ref> ''Quetzalcoatlus'' and other azhdarchids have forelimb and hind limb proportions more similar to modern running [[ungulate]] mammals than to members of other pterosaur clades, implying that they were uniquely suited to a terrestrial lifestyle.<ref name="witton&naish2008" /> The [[humerus]] was short and robust, with considerable mobility.<ref name="padian2021" /> Its morphology differs somewhat between species, with ''Q. lawsoni''{{'}}s humerus having a proportionally shorter [[Humerus|deltopectoral crest]], and ''Q. northropi''{{'}}s being shaped more like a twisted hourglass. The [[ulna]] of ''Q. northropi'' was relatively shorter than that of ''Q. lawsoni'', measuring 1.36 times the length of the humerus, as opposed to 1.52 times the length of the humerus in ''Q. lawsoni'' and other azhdarchiforms.<ref name="andres2021" />  Like all pterosaurs, ''Quetzalcoatlus'' had a specialized [[Carpal bones|carpal]] (wrist) bone, the [[Pterosaur|pteroid]], which attached to the [[Sesamoid bone|sesamoid]] bone of the wrist. It faced inwards, pointing towards the deltopectoral crest, and supported the [[Patagium|propatagium]]. Specialized muscles allowed it to move slightly.<ref name="padian2021" /> The first digit is the smallest, and the third is the biggest, with the exception of the [[Pterosaur|wing finger]]. As with all pterosaurs, the wing finger was considerably longer than the others.<ref name="andres2021" /> It did not contact the ground, as evidenced by footprints. Whilst on land, it may have been held between the elbow and the torso.<ref name="padian2021" /> The wings were short and broad, and forelimb musclature was extensive. Flapping power came from several [[Skeletal muscle|muscle groups]] on the torso, forearm and [[Manus (anatomy)|manus]] (hand).<ref name="wittonweight2010" />

Typically for a pterosaur, the [[pelvis]] of ''Q. lawsoni'' consists of an [[Ilium (bone)|ilium]], [[Pubis (bone)|pubis]] and [[ischium]] that had fused into a single unit, articulating anteroventrally (towards the front, at the bottom) with the [[wikt:prepubis|prepubis]], a small bone that sat before the pubis and likely helped support the abdominal cavity during respiration.<ref name="andres2021" /> The [[pelvis]] of one ''Q. lawsoni'' specimen (TMM 41954-57) is large compared to that of other specimens, with deep posterior emargination and no preserved [[Pubic symphysis|symphisis]]. This suggests that ''Q. lawsoni'' exhibited sexual dimorphism, similar to that suggested for other [[monofenestrata]]ns (i.e. ''[[Darwinopterus]], [[Anhanguera (pterosaur)|Anhanguera]]'' and ''[[Nyctosaurus]]''). The [[femur]] was significantly more gracile than the humerus, though was still among the most robust bones in ''Quetzalcoatlus''{{'}} skeleton, judging by ''Q. lawsoni''.<ref name="padian2021" /> Based on ''Zhejiangopterus'', the humerus was around eighty percent of the length of the [[tibiotarsus]]. Azhdarchids overall had fairly narrow feet, no longer than 30% of the length of the [[tibia]],<ref name=":1" /> which may have borne fleshy pads similar to those of tapejarids.<ref name=":1" /><ref name="HHLUW022">{{cite journal |last1=Hwang |first1=K.G. |last2=Huh |first2=M. |last3=Lockley |first3=M. |last4=Unwin |first4=D. |last5=Wright |first5=J.L. |year=2002 |title=New pterosaur tracks (Pteraichnidae) from the Late Cretaceous Uhangri Formation, SW Korea |url=http://repository.geologyscience.ru/bitstream/handle/123456789/28316/Hwan_02.pdf?sequence=1&isAllowed=y |journal=Geological Magazine |volume=139 |issue=4 |pages=421–435 |doi=10.1017/S0016756802006647 |s2cid=54996027}}</ref> They were [[plantigrade]], meaning that they walked with the sole of the foot flat on the ground.<ref name="andres2021" /> ''Q. lawsoni'' possessed well-developed pedal (foot) [[ungual]]s, which supported moderately curved claws, shorter and slightly straighter than those of tapejarids.<ref name="padian2021" />