Distinct from no. 42, the skull of no. 57 was longer and flatter, with more teeth. The antorbital fenestra was relatively shorter, due to the long flat beak, and the orbit was smaller.
The cervicals were elongated, as in Huanhepterus. The dorsal were relatively shorter, but continued to include 12 vertebrae. The sacrals were the longest of any pterosaur, extending to nearly two-thirds of the torso. They were much more robust than the dorsals and coosified. The caudals were a reduced to tiny beads.
The sternal complex was semi-circular with a deep keel. The scapula was reduced but continued to articulate with the sixth dorsal. The coracoid. already small in this clade, became more slender. The humerus and radius+ulna were less than half the relative length compared to no. 42. The metatacarpus and other wing elements were even shorter, terminating in extremely tiny vestigial phalanges. Fingers I-III were smaller, but not by as much.
The ilim extended as far as the sacrals did creating the largest pelvis among pterosaurs. What Wellnhofer (1970) considered a tail, was actually the posterior illium and associated sacrals. The pubis and ischium were slightly separated ventrally and relatively shallow. The prepubis was a wide fan-like shape. The femur appeared to be long in lateral view, but compared to no. 42, it was shorter and more slender.
This is the first detailed examination of this specimen along with the first reconstruction. JME-Sos 2428 (no. 57) would have retained the ability to vigrously flap its wings to frighten enemies and generate thrust, but the wings were too short and the body was too heavy for sustained flight. While Henderson (2010) figured that Quetzalcoatlus might have been flightless due to its size, it did not have the short wing/huge torso/small pectoral girdle combination that JME-Sos 2428 (no. 57) had.
When one encounters a reptile with such a huge torso, one begins to wonder if the diet had switched to plants, perhaps algae in the case of this wader.
See the pterosaur family tree here.