Quetzalcoatlus sp. (Kellner and Langston 1996, Q. northropi, Lawson 1975), Late Cretaceous, ~65mya, ~80 cm skull length, was a smaller version of the largest flying creature, represented here by its humerus, several times larger than the humerus of the smaller, more completely known specimen. Quetzalcoatlus was derived from a sister to Chaoyangopterus and Zhejiangopterus and was the last of its lineage and among the last of all pterosaurs to become extiinct at the latest Cretaceous.
Much larger than and distinct from Zhejiangopterus, the skull of Quetzalcoatlus was relatively smaller, more of the ratio in Chaoyangopterus, with a similar morphology, but a longer rostrum. The jawline appears to bend down posteriorly. A crest surmounted the rear of the antorbital fenestra. The mandible was flatter with a smaller ventral crest.
The cervicals were very much elongated. The dorsals were shorter.
The scapula/coracoid was fused and massive, much larger than the small sternal complex. The wing phalanges rapidly decreased distally. Manual 4.4 was a vestige.
The pelvis was similar to Zhejiangopterus, but relatively smaller. The prepubis ventral process was expanded and the anterior process reduced.
Metatarsal V was very large, nearly as wide as the rest of the metatarsus. The metatarsals were closer to those in Chaoyangopterus in relative length.
Comparisons to Zhejiangopterus are useful in determining the flightworthiness of both taxa. In Quetzalcoatlus the the pectoral girdle was massive, despite the short wings, and the pelvis was relatively small, just the opposite of Zhejiangopterus. Also compare these taxa with the flightless pterosaur, SoS 2428.
See the pterosaur family tree here.
Hone and Benton (2006) reported, "The remarkable extinct flying reptiles, the pterosaurs, show increasing body
size over 100 million years of the Late Jurassic and Cretaceous, and this seems
to be a rare example of a driven trend to large size (Cope’s Rule)." They arrived at this "result" by drawing a straight line from early pterosaurs, like Anurognathus, to the Late Cretaceous pterosaur, Quetzalcoatlus over time and by deleting all purpoted juveniles. They did not realize that 1) there were four pterodactyloid-grade lineages; 2) the purported juveniles were actually adults; and 3) any sort of a roller-coaster effect of size increase/decrease/increase/decrease over time would be negated by drawing a straight line.