Skin deep: Dinosaur scales provide clues to Alberta's ancient past

For some dinosaur species, the evolutionary changes resulting from their dispersal across the Earth were only skin deep.

'It's undoubtedly much easier for differences in skin to evolve'

Fossilized skin of the Saurolophus, a duck-billed dinosaur which once roamed the Earth, is the subject of new research on dinosaur evolution. ( L. Xing and Y. Liu)

For some dinosaur species, the evolutionary changes resulting from their dispersal across the Earth were only skin deep.

It's their scales that might hold all the secrets.

As part of CBC's summer-long series Backyard Dinosaurs — which will feature a different dinosaur found in Alberta each week — University of Alberta paleontologist Scott Persons has been exploring this aspect of paleontology.

The recent discovery of beautifully preserved skin from the T- Rex has renewed public fascination around the epidermis of dinosaurs.

But the find was not the first of its kind.

A duck-billed dinosaur, or hadrosaur, by the name of Saurolophus has provided plenty of clues on the topography of ancient Earth.

"In Latin, the name Saurolophus means lizard crest," Persons said in an interview with Radio Active. "And the most distinctive feature of Saurolophus is its bony head crest, which looked like a conical party hat, strongly inclined to the rear." 

Fossils of the Saurolophus have been found in Alberta and across the Pacific in the Gobi Desert of Mongolia.

The Dragon's Tomb

Renowned paleontologist Phil Bell has discovered that while skeletons of Albertan and Mongolian Saurolophus are very similar, their skin is dramatically different. 

Well-preserved skin fossils from Saurolophus have been found on both continents. The best came from a spot in the Gobi Desert romantically nicknamed The Dragon's Tomb.

"I have been there and the place just takes your breath away," Persons said. "There are dozens of articulated Saurolophus skeletons, often with large patches of skin preserved right over the bones." 

Spots and stripes

Skin fossils at the Dragon's Tomb have a mosaic of small scales broken up by occasional large ovoid scales. Alberta's Saurolophus lacks these big scales, Persons said.
Scott Persons says the fossilized skin has provided new insight into ancient Earth and the evolution of the dinosaurs. (Amanda Kelley)

Also, the Mongolian species has a row of large, vertical, semicircular scales running down the spine of its back, resembling the edge of a big pie crust, a feature the Alberta fossils lack, he said.

Researchers also noticed some of the scales along the tail of Mongolian Saurolophus are arranged in a striped pattern, whereas, in the Albertan species, they are more circular.

Scientists hypothesized that those patterns may have corresponded to patterns in colour. If so, a Saurolophus from Asia may have been striped, while the Alberta species may have been spotted, said Persons.

The Saurolophus' presence on both continents is an important piece of evidence telling us that, at some point back in the Late Cretaceous — about 70 million years ago — there was a land bridge spanning what is now Alaska and eastern Russia, Persons said.

And the difference in their skin is proof that two disparate species evolved after a population of the creatures travelled across that bridge.

"The dinosaur probably originated on one landmass and, eventually, a fairly large sub-population gradually worked its way to the other, where it became adapted in subtle ways to life in the new environment," said Persons.

"It's undoubtedly much easier for differences in skin to evolve."
Palaeontologist Phil Bell, pictured here in the Albertan badlands, is responsible for discovering the striking differences in the skin of these duck-billed dinosaurs. (Scott Persons)