Theropods of the Judith River Formation of dinosaur Provincial Park, Alberta, Canada Author Currie, P. J. text 1987 1987-12-31 Tyrrell Museum of Paleontology Drumheller, Alberta Editor Currie P. J. Editor Koster E. H. Fourth Symposium on Mesozoic Terrestrial Ecosystems 51 60 book chapter http://doi.org/10.5281/zenodo.3676391 246dae96-99ed-4bb9-9ae7-b0223b873cf6 3676391 Gorgosaurus libratus frontals are characterized by the presence of a prefrontal socket, the reduction of the orbital rim to a notch , and the retention of a relatively short (rostrocaudally), overlapping suture for the postorbital ( Fig. 1g ). immature frontals of Gorgosaurus libratus can be distinguished from that of cf. Aublysodon by their relatively greater thickness and width for a given length. in Daspletosaurus torosus , the shape of the frontal has been changed by the enlargement of the lacrimal and postorbital, causing an increase in the posterior width of the frontal ( Fig . 1h ), and a lengthening of the postorbital suture.