In 1902, Scottish writer and screenwriter J.M. Barrie created the character of a child who never grows up: Peter Pan. Gorgosaurus can be considered a theropod that never grows up, too: not because it reached sexual maturity without developing adult traits, like modern axolotls, but because, due to some very famous historical montages, it’s frequently represented as an immature specimen even when the illustrator means to depict an adult. It doesn’t help that Scott Hartman’s skeletal, quite easy to stumble upon on a Google Search, represents an immature specimen, too (keep in mind that Dr. Hartman specifies this).
It’s only in the Walking With Dinosaurs 3D movie (2013) that Gorgosaurus shakes off this uncomfortable iconography: “Gorgon” from the movie is modeled using as a reference the holotype, an adult specimen. So will the PNSO model, released ten years later, also depict an adult Gorgosaurus? Let’s see.
Upon its release, the Gorgosaurus PNSO had raised some eyebrows due to its proportions. The skull, in particular, didn’t look much like the one in Walking With Dinosaurs 3D, which since ten years is how many think Gorgosaurus. And they’re right: it does not match the skull of a fully developed Gorgosaurus, like TCMI 2001.89.1. But it perfectly matches that of ROM 1247, a six-meter-long animal. By the way, a scan of this skull was uploaded by the WitmerLab on the Sketchfab website (a 3D model viewer), and the PNSO sculptor could easily have used it as a reference.
And in the same way, proportions match with ROM 1247: Tyrannosauridae ancestors were not hulking behemoths, but lithe, cursorial animals. It’s debated whether the adults – which weighed several tons, and whose cursorial specializations must deal with the size they achieved – were as fast, but less mature specimens, decidedly smaller, retained runners traits. This trend is exacerbated in Tyrannosaurus, in which the adult shows such morphological disparity with the juvenile that the latter was once not recognized as Tyrannosaurus and variously classified in other genera (such as Nanotyrannus, Stygivenator, Dinotyrannus). Now, if we compare the PNSO model with the ROM 1247 mount displayed at the Royal Ontario Museum, we see that it has the same small head and long legs that had eyebrows rising at first.
Thus, PNSO Gorgosaurus represents a not fully developed specimen. The reason for this choice may be the desire to further differentiate it from the Albertosaurus released just a week earlier. Differences between Gorgosaurus and Albertosaurus, once the skeleton is covered with soft tissues, are – as far as we know – relatively few: an easy way to distinguish the two is that Gorgosaurus has a more rectangular skull, while in Albertosaurus the snout is arched (rather dramatically in at least one specimen).
As for the rest, the Gorgosaurus shows the usual attention to detail of all PNSO models: inside the mouth, there are the choanal openings, the cloaca is sculpted, the neck is suitably robust, and the skin folds follow the movement (especially noticeable when comparing the right side with the left) and in the forelimbs, the second finger is longer than the first, as in most predatory theropods (the third finger, on the other hand, has been lost in the more derived Tyrannosauroids). Particularly interesting is the position in which the forelimb is depicted: instead of dangling as in other reconstructions, is partially tucked along the sides.
A trait that distinguishes Albertosaurus and Gorgosaurus from their relatives is a tail about ten vertebrae shorter, as seen in a well-preserved specimen (TMP 91.36.500). The tail of the PNSO model looks like it’s a couple of centimeters too long when compared to this fossil. It could be a marginal mistake on the sculptor’s part, or a deliberate choice. There are two specimens of Leptoceratops (CMN 8887 and CMN 8888) that show variability in tail length, but they have not been studied in detail to check if one of the tails was restored or not, and in any case, they are very distant relatives of Gorgosaurus, basically at the opposite end of dinosaurs’ evolutionary tree.
The PNSO Gorgosaurus shows a slight overbite, like some of the older models. In this case, the discrepancy could be attributable to technical difficulties with the articulation, since the skull is smaller than that of the three most recent PNSO Carcharodontosauridae (Giganotosaurus, Meraxes, Mapusaurus), whose skull had no overbites.
To sum up, once accepted that the model does not represent a fully developed specimen and therefore will not be on the same scale as the other PNSO Tyrannosauridae (but neither is Lythronax by the way), the PNSO Gorgosaurus is a faithful representation of a rather well-known and well-studied specimen.
BIBLIOGRAPHY
Holmes T.; Holmes L.; Skrepnick M. Meat-Eating Dinosaurs: The Theropods. Enslow Pub Inc, 2001. 128 pp. Retrieved from archive.org
Snively E.; Russell A.P. (2007) Functional variation of neck muscles and their relation to feeding style in Tyrannosauridae and other large theropod dinosaurs. The Anatomical Record Advances in Integrative Anatomy and Evolutionary Biology, 290: 934-957
Voris J.T.; Zelenitsky D.K.; Therrien F.; Ridgely, R.C.; Currie P.J.; Witmer L.M. (2021) Two exceptionally preserved juvenile specimens of Gorgosaurus libratus (Tyrannosauridae, Albertosaurinae) provide new insight into the timing of ontogenetic changes in tyrannosaurids. Journal of Vertebrate Paleontology, 41:6, DOI: 10.1080/02724634.2021.2041651
The author would like to thank users from the Theropods 2.0 Discord server for contributing to this article.