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Feathers for flirting or flying?

Alberta researchers say dino fossils point to showing off

By: Staff Writer

Posted: 10/26/2012 1:00 AM | Comments: 0

The Canadian Press An artistic reconstruction of the feathered Ornithomimus dinosaurs. (CP)

CALGARY -- A set of 70-million-year-old fossils from southern Alberta has added weight to theories dinosaurs may have first sprouted feathers to show off, not take off.

Darla Zelenitsky, a paleontologist at the University of Calgary, says three years of study on dinosaur fossils found near Drumheller, Alta., suggest the features most closely linked with flight evolved for a completely different reason.

"They may have initially evolved as a secondary sexual characteristic," says a paper published Thursday in the prestigious journal Science.

"These wing-like structures would have been used for reproductive activities (courtship, display, brooding) and were only later... co-opted for other roles including flight."

The fossils in question -- the oldest feathered dinosaurs ever found -- are from three members of the species Ornithomimus edmontonicus, an agile, two-legged dinosaur that looked like a large ostrich and most likely lived off a mixed diet of bugs, fruit, leaves, eggs and the occasional small animal.

Ornithomimus aren't the direct ancestors of modern birds, but still offer clues to their development.

"Our specimens show the most primitive occurrence of wing-like structures," says Zelenitsky. "These specimens thus push back the occurrence of wing-like structures and give insight into their early uses."

On two of the individuals, one adult and one juvenile, Zelenitsky found traces of filamentous feathers -- a primitive form of feather without the rigid central shaft.

That would have been exciting enough.

The fossils, found in 2008 and 2009, have pushed back the date of the earliest fossil feather by about 10 million years. As well, they were the first feathered dinosaur fossils found in North America and the first found in relatively coarse sandstone.

But things got even more interesting when Zelenitsky compared the two fossils with a third adult Ornithomimus unearthed in the same area in 1995. Despite being from exactly the same species, this dinosaur had much more advanced feathers.

"Their distribution and orientation are similar to the insertion pattern of covert feathers, which form the bulk of the feather covering in modern bird wings."

At about 150 kilograms, Ornithomimus was too big to fly, says Zelenitsky. And the fossils also suggested real feathers weren't something Ornithomimus grew until it was fully adult.

That allowed her to make a couple of inferences:

"Because they're in these large dinosaurs, (wings) haven't evolved for flight," Zelenitsky says. "(And) because these wing-like structures develop later in life, that suggests they were used for purposes like display or courtship or egg-brooding."

Feathered dinosaurs were first discovered in China in the late 1990s.

-- The Canadian Press

Republished from the Winnipeg Free Press print edition October 26, 2012 A17

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