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Dino of the week: the Parasaurolophus. Large crest on its head used like a horn rather than a snorkel

July 10 , 2016

by Dave Dormer

Of all the dinosaurs, this one had the best chance of being a radio star. Called the Parasaurolophus, it was a duck-billed plant eater about the size of a pickup truck that had a unique characteristic — a large crest jutting from the back of its head that served as a horn.

As part of the summer-long series Backyard Dinosaurs — which will feature a different dinosaur found in Alberta each week — University of Alberta paleontologist Scott Persons explained to the Homestretch how scientists came to that conclusion, and were even able to reproduce the sound it may have made.

Which dinosaur are we looking at today?

For our first backyard dinosaur, I want to talk about a critter called Parasaurolophus. It's a kind of duckbill or hadrosaur. So, it was a plant-eater, about the size of a big pickup truck. Of all the dinosaurs, I think Parasaurolophus is the best candidate to be a radio star, because it's the one dinosaur that scientists can attempt to recreate what it sounded like.

How do you do that?

Well, it's not easy. But to explain that, we need to talk about a bizarre mystery that Parasaurolophus presents. When the first Parasaurolophus skeleton was excavated in Alberta back in the early 1920s, the dinosaur's skull seemed to defy all explanation. Parasaurolophus has been called the dinosaurian bishop or pompadour, because it has an enormous meter-long cylindrical crest jutting out the back of its head.

Like a horn on Triceratops?

No. That's what was so strange. There's no way that crest could have been a piercing horn or battering ram. For one, the tip just wasn't sharp, it was round, it was slightly bulbous and inside the crest was hollow, which would have made it very, very fragile. It was a long empty chamber that ran from the dinosaur's nostrils, up through to the end of the crest, then it does a U-turn and loops back around and goes back down through the crest and to the mouth and throat. In effect, the crest housed a massive extension of the nasal passage.

Did it have a purpose?

Well, some of world's top paleontologists tried to figure that out. Shortly after Parasaurolophus was found, a bunch of different hypotheses got thrown at this problem of what did this crest do. And now, the plot thickens, because the mystery of Parasaurolophus's head got mixed in with the mystery of duckbilled dinosaur hands. About 10 years earlier, the world's first dinosaur mummy was discovered and by that I mean it was a dinosaur skeleton that included not just the bones but also a lot of fossil skin and soft tissue still clinging to the skeleton. This dinosaur mummy was also a duckbill and one of the things it showed was that there was a lot of extra flesh around the digits, around the fingers in the hands. So this mummified dinosaur mitten, as it was called, was taken as an indicator that duckbilled dinosaurs had webbed feet and everyone thought that meant they really did behave like ducks and spent a lot of time swimming.

Does the swimming connect with a big head crest?

Some paleontologists did think the two had a lot to do with each other. First, it was proposed that the hollow crest might have been a snorkel, that Parasaurolophus could stick the crest out of the water and breathe through, while it was grazing on water plants. But that idea didn't hold up, since, although the crest looks like a snorkel, the tip is totally solid. So, even if it was projecting out of the water, there would be no way for air enter or exit. Other paleontologists reasoned then, if it wasn't for snorkeling, maybe it was for scuba diving. This idea was that the crest acted as an extra air reserve. By breathing in through its nose, the dinosaur could fill the crest with fresh air, and then, when diving down to feed, it could breathe the reserve of air through its throat in order to stay submerged longer.

So did it dive like a duck?

No. The later discovery of duckbill dinosaur forepaw tracks has shown definitively that we were totally wrong about them having webbed feet. In fact, in a way, the exact opposite seems to be true. The extra flesh on their hands didn't form a web for paddling through the water, it formed a big cushioning pad, like you would find on the feet of camels for walking over hard dry ground. The ecology of duckbills got totally rewritten. Not being divers actually made a lot of sense for a number of other reasons. For instance, the teeth and jaws of hadrosaurs were way stronger than what would be needed to chew soft water plants.




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