Meeting Abstract
The giant pterosaur Quetzalcoatlus northropi (QN) lived at the very end of the Cretaceous Period, about 67 million years ago, in Texas. It was named on the basis of a few incomplete post-cranial bones that suggested a wingspan of 11-13 m; a morph about half this size is known from numerous bones and partial skeletons. In the air, like most large aerial animals, it mainly soared, but it could flap to some degree. On the ground, like all pterodactyloids, QN walked quadrupedally, but this was mainly because its metacarpals were so long that the manus could not avoid touching the ground. Pterosaurs were originally bipedal, like their ancestors. Manipulation of QN’s forelimb and hindlimb bones confirms that in a quadrupedal pose the humerus had limited rotation (about 25°) and the forearm and metacarpus could be slightly elevated and depressed at the elbow, but the forelimb had no significant retractive power. All joints of the hindlimb are hinges except the hip, a ball-and-socket offset by a neck oriented dorsally, medially, and posteriorly. The hindlimb thus had an erect stance and parasagittal gait, as in other ornithodirans. Pterodactyloids such as QN lifted their limbs unusually, because overstepping was not possible: the lift cycle was LM – LP – RM – RP, where M is manus and P is pes; however, the sequence of emplacement would have been LP – LM – RP – RM. The full step cycle was: LM lift – LP lift – LP place – LM place – RM lift – RP lift – RP place – RM place. Although technically quadrupedal, QN showed its bipedal heritage when it walked on land.
