Parasaurolophus

Plesiolophus is a lambeosaurine hadrosaur known from the same locality, but an earlier time period than Parasaurolophus. Though it is nearly impossible to know conclusively, Plesiolophus cannot be ruled out as a direct ancestor. Like Parasaurolophus, Plesiolophus would have had a distinct crest protruding backward from its skull.

Pectoral girdles and forelimbs of dinosaurs in left lateral view, depicting resting scapular and forelimb orientations in different dinosaurian groups as recommended according to the results of this study. In each case, solid horizontal line is parallel to long axis of sacrum. A. theropods without semilunate carpals (Dilophosaurus wetherilli, UCMP 37302). B. theropods with semilunate carpals other than Caudipteryx (Velociraptor mongoliensis, after reference [60]). C. Caudipteryx (C. sp., after reference [8]). D. ceratopsids (Styracosaurus albertensis, NMC 344). E. basal sauropodomorphs (Plateosaurus engelhardti, AMNH 6810). F. non-hadrosaurian ornithopods (Thescelosaurus neglectus, reference [62]). G. hadrosaurids (Parasaurolophus walkeri, after reference [48]). Angle labels: B = scapular orientation relative to long axis of sacrum. E = elbow angle. S = shoulder angle. W = wrist angle. See Materials and Methods section for descriptions of angles.