Ultimate Dinosaurs: Like Problems Inspire Like Solutions

In my last blog article, I hinted at the upcoming Ultimate Dinosaurs special exhibition here at the Canadian Museum of Nature. Today I’m excited to officially announce its opening—from June 11 to September 5, 2016.

The exhibition features dinosaurs from the southern hemisphere, many of which may appear strange and alien to our North American eyes.

One hundred and forty-five million years ago, during the Jurassic Period, the ancient supercontinent of Pangaea divided into two landmasses: a northern one called Laurasia and a southern one called Gondwana. Ultimate Dinosaurs tells the story of dinosaur evolution on Gondwana.

Gondwana continued to divide into the continents we know today (namely, South America, Africa, Madagascar, Australia and Antarctica). During the subsequent 80 million years or so, dinosaur populations became increasingly isolated as the continents drifted apart, and evolution followed a very different path on each one.

A map.

Map of Earth as it appeared 150 million years ago, as Laurasia and Gondwana were beginning to separate from one another. Image: © Ron Blakey and Colorado Plateau Geosystems, Inc.

The result was a diverse panoply of creatures that exhibit an endless array of bizarre adaptations. But the southern forms weren’t entirely devoid of analogues here in the northern hemisphere. In many cases, distantly related, yet similar-looking animals occupied both halves of the globe, a bit like North American placental wolves and Australian marsupial wolves of the modern era.

Take, for example, the South American Austroraptor and North American Utahraptor. Both dinosaurs were about the size of a large bear, and yet they appear to have evolved their large size independently, perhaps in response to hunting increasingly large prey on their respective continents.

Their earliest common ancestor was nearer in size to a dog—hardly something we’d consider terrifying today. But the large size, rapid speed, and killer claws of Austroraptor and Utahraptor would have made these animals feared in their time (and maybe a little today, too!).

Composite: Two photos of mounted dinosaur skeletons.

Austroraptor (left) and Utahraptor (right) were only distantly related raptor dinosaurs, yet they evolved large body size independently. Images: Jordan Mallon, Jim Kirkland © Canadian Museum of Nature

Another example of evolutionary convergence is between the North American tyrannosaurid Daspletosaurus and the South American abelisaurid Carnotaurus. Both predators were massive (exceeding 9 m in length), had deep skulls that were reinforced for biting prey, and dinky little arms.

In fact, the arms were so small that many palaeontologists consider them to have been useless. It seems that both these carnivores independently concentrated their killing power in their skull, and their arms, which were once used for prey dispatch, dwindled away from inactivity. Use it or lose it, fellas!

Composite: Two photos of mounted dinosaur skeletons.

Carnotaurus (left) and Daspletosaurus (right; collection #CMNFV8605) were separated by thousands of kilometres and millions of years of evolution, but both converged on similar body plans with deep skulls and highly reduced arms. Images: Jordan Mallon © Canadian Museum of Nature

Finally, consider the North American hadrosaurid Edmontosaurus and the South American sauropod Nigersaurus. Really, these animals are from opposite sides of the dinosaur family tree and look nothing like each other. But look closer: they both have an unusually wide muzzle for cropping low-growing plants.

In the case of Edmontosaurus, the muzzle consisted of a horny beak; in Nigersaurus, it was a battery of straight, pencil-like teeth. With their faces pointed at the ground, each herbivore could easily decimate large swaths of herbage in record time, which is an important adaptation when you consider the large body they needed to feed.

Composite: Two photos of dinosaur skulls.

Similar low-cropping habits led to the independent evolution of square muzzles in the sauropod Nigersaurus (left) and the hadrosaurid Edmontosaurus (right; collection #CMNFV2288). Images: Jordan Mallon © Canadian Museum of Nature

I can’t stress enough what a great exhibition this is. You can travel to no other place in the northern hemisphere to see this same parade of bizarre creatures.

If you’re anywhere near Ottawa this summer, be sure drop by the Canadian Museum of Nature to treat your eyeballs to Ultimate Dinosaurs. You may have to wait another geological age for this opportunity to come again.

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