Dino of the week: the Edmontosaurus

It was once so common on the prairies, scientists nicknamed it the cow of the Cretaceous.

Millions of years before bison and cattle began roaming Alberta, a large, duckbilled dinosaur known as the Edmontosaurus grazed here, measuring up to 15 metres in length and the largest weighing nearlynine tonnes.

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As part of a summer-long series Backyard Dinosaurs featuring a different dino found in Alberta each week University of Alberta paleontologist Scott Persons explained to The Homestretch why it was so common.

How common was the Edmontosaurus?

"More fossils of Edmontosaurus have been found than probably any other dinosaur. In fact, it was so common that the dinosaur has been nicknamed the cow of the Cretaceous. And thanks to that abundance of fossil remains, Edmontosaurus is also one of the most studied and wellunderstood dinosaurs. But even so, a lot of recent discoveries of more than just fossil bones have a lot of new insight into the ecology and appearance of this ubiquitous duckbill."

So was it named for Edmonton?

"The city, no. At least not directly. Edmontosaurus was first found in Alberta, but not in the city. It was actually named after the Edmonton Formation,the geologic layer of rocks that the fossil were first excavated from. And that formation is now part of a larger geologic section called the Edmonton Group, and that, in turn, was named for the city. Nevertheless, Edmontosaurus is currently a source of hometown pride, because fossils of this duckbill have since been found within the city limits and that includes what we call the Edmontosaurus bone bed, which is a spot filled with a whole bunch of different skeletons all from the same kind of dinosaur and they're all jumbled together, we've got big adults and juveniles mixed in there."

We know about the duckbill, but what did the Edmontosaurus look like?

"In most respects, Edmontosaurus really is the classic duckbilled dinosaur, although, it does stand out as one of the largest. There are a couple of different species, but a really big adult of the really biggest species was as big, if not even a little bit larger than T. rex, and that means it was pushing around 49 feet in length, with a weight in the neighbourhood of eight to nine tons. Mostof the time, Edmontosaurus walked around on all four legs, but its back legs were much, much bigger than its fore legs, which were relatively narrow and thin so when it was running, it would rear back onto just its hind legs. It's got that classic duckbill which makes the skull extremely long, it's over a metre in length and it's also got a massive tail that was heavily muscled and also strengthened by bony tendons."

Why was it so common?

"The key to the success of Edmontosaurus was its unmatched ability to chew. As a duckbilled dinosaur, Edmontosaurus had not only the big bill at the front of its mouth, which was used to crop off vegetation, but at the back of its mouth behind the bill, it also had what we call dental batteries. Dental batteries are structures formed by rows and rows of teeth. Not big teeth, but little ones, each one was much smaller than the molar of say a cow or a horse.

"These little teeth grew in tightly together, like a picket fence so tight that an Edmontosaurus couldn't have flossed, you physically couldn't force the string between the teeth and collectively, those rows of tightly packed teeth formed a single, broad grinding surface. In addition to not ever having to floss, an Edmontosaurus would also never have needed dentures. Dinosaurs were like modern sharks and crocodiles, in that they never ran out of teeth. New teeth were constantly growing in underneath the old teeth, and would gradually replace them."

Have there been any new discoveries about Edmontosaurus?

"There have been some really cool ones. In 2013 a new specimen of Edmontosaurus was found in Grande Prairie, and this specimen included a whole bunch of soft tissue, skin and things like that from around the skull. And it shows for the first time, although we classically have been drawing this duckbill as have a plain, duckbilled head, it actually had a fleshy crest on top of it, like the comb of a modern rooster."