Dinosaur eggs mislabelled for years

Fossilized nest in Calgary collection turns out to be one-of-a-kind

Jamie Komarnicki, Canwest News Service

Published: Vancouver Sun, Friday, November 14, 2008

The first clue something was wrong was the shape of the dinosaur eggs—long and pointed at one end rather than smooth and round.

The fossilized nest that contained five of the 12-centimetre-long eggs sat mislabelled in a private Calgary collection for years, its significance undetected.

But a closer look by University of Calgary paleontologist Darla Zelenitsky determined the eggs were not, in fact, the rounded, “dime-a-dozen” duck-billed dinosaur find.

Rather, the eggs belonged to a small theropod, or meat-eating dinosaur, closely linked to birds—making the fossil the first known nest of its kind.

“This is a brand new nest to North America and worldwide,” said Zelenitsky, lead author of a paper published Thursday in the journal Palaeontology.

But the scientific detective work doesn’t stop there.

Researchers still don’t know the exact identity of the mysterious mother who abandoned the eggs 77 million years ago to the swelling waters on a sandy river beach, Zelenitsky said.

But they have picked up clues of her reproductive habits.

The mother dinosaur hunkered down on the banks of a fast-flowing river in the Montana badlands, said Francois Therrien, a co-investigator in the study and curator of dinosaur paleoecology at the Royal Tyrrell Museum.

She built a sandy mound, then laid about a dozen eggs, two at a time, placing them in a ring around the nest before climbing atop to keep them warm, he said.

These behaviours are closely identified with the brooding habits of birds—details that further cement the significance of the discovery, Therrien said.

“This nest reveals that modern birds aren’t unique in the way they reproduce; they actually inherited a lot of ways that they lay eggs from their dinosaur ancestors,” Therrien said.

“This tells us what we see as modern birds laying eggs and the way the eggs are shaped, it’s an actual, gradual acquisition of traits through time.”

The fossilized nest was discovered near Cut Bank, Mont., in the 1990s and belonged to a private Calgary collection.

It had been labelled the more common hadrosaur, or duck-billed dinosaur.

Examining the collection several years ago, Zelenitsky noticed the unusual patterns of the eggs. Realizing the significance of the nest if it belonged to a meat-eater, she began an in-depth investigation when the fossils arrived at the Royal Tyrrell.

Researchers have since narrowed the possible mother down to two likely candidates: a small raptor called a dromaeosaurid, or an ostrich-like caenagnathid.

“It’s going to be one of those two; neither one of those two types of nests are known,” Zelenitsky said.

The dinosaur likely weighed about 40 kilograms and was 2.5 to three metres long, she said.

The mother’s identity may only be truly revealed if another nest of this type is discovered with an adult atop, or embryos inside the eggs, Zelenitsky said.

“As more and more of these dinosaur nests are uncovered, it just keeps putting all of the pieces together,” she said.

The fossilized nest goes on display at the Royal Tyrrell at the end of the month.