Abstract
A well-preserved pelvis of a large pterodactyloid pterosaur from the Santana Formation (Aptian) of Brazil is described. The pelvis is the first in which the orientation of the acetabulum is unambiguous. The acetabulum is directed laterally and posteriorly, and indicates that the femur could be brought under the body. This would allow bipedal locomotion, and a new model of bipedal locomotion for pterodactyloid pterosaurs is presented.