Dino News and Views: The Great Parasaurolophus Pathology

Friday, December 4, 2020

The skeleton of Parasaurolophus on display at the Royal Ontario Museum. Look closely for the signs of injury in its bones. Photo by missbossy, CC BY 2.0

Despite its status as a fairly popular and famous dinosaur, the tube-crested duckbill Parasaurolophus walkeri is actually quite rare. The first specimen known to science, collected from Alberta’s Dinosaur Provincial Park and housed at the Royal Ontario Museum in Toronto, is still the most complete example of this species.

While the iconic backwards-sweeping, tube-shaped crest of this dinosaur is one of its most famous features, the Toronto Parasaurolophus specimen has a variety of other weird features that stand out to the discerning eyes of palaeontologists. Several bones on the left side of the dinosaur, including some vertebrae, ribs, and hip bones, all show some strange growths deformities. These are most obvious in the backbones just over the shoulders where, instead of sticking straight upwards like normal, two of the vertebral spines have grown bizarrely away from each other, forming a strange v-shaped notch in the animal’s back. The foreword-facing spine in this notch had also fused with the vertebral spine in front of it, which itself had a weird disc-shaped growth of bone at its tip.

The presence of this odd dorsal notch in Parasaurolophus had early Canadian palaeontologists scratching their heads, unable to convincingly explain why these features existed. No other hadrosaur, including other specimens of Parasaurolophus, show such conditions. We now know that strange growths and deformities seen in dinosaur bones often arise from injuries and infections acquired by the animals while they were still alive. The study of dinosaur bone injuries and diseases is an ever-growing field these days, and brand new research from Filippo Bertozzo and colleagues has used this approach to study the weird anomalies of the Toronto Parasaurolophus.

The authors of this new paper argue that many of the bone deformities in this dinosaur, given that they’re confined to just the animal’s left side, can be explained by it having suffered a nasty injury while it was alive. The left ribs near the shoulder show healed fractures, meaning something big hit the side of animal at one point. The object had also slammed down hard on the dinosaur’s back, deforming its vertebral spines and producing the strange back notch.

What could have struck such a nasty blow to this dinosaur? It’s hard to say for sure, since we can’t go back in time and witness the event for ourselves. There’s certainly some likely possibilities we can consider, though. Perhaps it was attacked by another dinosaur, maybe a member of its own kind during courtship battles. Perhaps it was hit by a big falling rock. Or perhaps (and I think this might be the most likely scenario) it was hit by a falling tree trunk, as illustrated in some striking palaeoart in the paper itself.

The authors reason that the unusual bone growth in the dinosaur’s hip may have resulted from it essentially figuring out how to balance and walk again after suffering such an injury.  The weird disc-shaped bone growth in front of the backbone notch might indicate that this is where a ligament that ran along the top of the dinosaur’s neck to the back of its skull connected. Knowing how this ligament spanned the neck of Parasaurolophusfurther allowed Bertozzo and colleagues to determine what other palaeontologists have been suspecting for a while now- that Parasaurolophus, and probably most other duckbills, had really thick, well-muscled necks.

Learning all this brings us some fascinating new insights into a popular yet enigmatic dinosaur. Seeing the trials of its life written into its very bones makes us realize that Parasaurolophus, and all other dinosaurs, were once living animals, just trying to get by in a tough world.

Source: www.mayerthorpefreelancer.com/