On the basis of a well-preserved pelvis of Anhanguera sp. from the Lower Cretaceous (Aptian) of the Chapada do Araripe, Brazil, the problem of terrestrial locomotion in pterosaurs is discussed. A three-dimensional reconstruction of the pelvis led to a lateral, dorsal and posterior orientation of the acetabula. By use of the preserved proximal ends of the femora of the same individual, the articulation in the hip socket could be tested. The normal articulation of the femur resulted in a horizontal position of the femur shaft, probably during flight. For constructional reasons the femur could not be brought down to a vertical position. Therefore, a parasagittal swing of the femora necessary for a bird-like stance and gait must have been impossible. It is suggested that in pterosaurs the wing membrane was attached to the upper leg, which helped in stretching, steering and cambering. Moreover, on the basis of comparisons of the fossil preservation of pterosaurs Compsognathus and Archaeopteryx in the Solnhofen limestone, it is concluded that the femora of pterosaurs were splayed out laterally, and that they had a semi-erect gait. They were not bipedal animals, but had to use their fore limbs as well on the ground. Nevertheless, as vertebrates extremely adapted to flight, they could not have been able quadrupeds, either.
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