Eggs show link between dinosaurs and birds

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Current research done by paleontologists at the University of Calgary and Montana State University has led to a new understanding of how some dinosaurs cared for their eggs. 

While dinosaur eggs can be preserved in much the same way as other fossils, complete nests are more difficult to find. 

“The nests of dinosaurs are very rarely preserved — it is usually just the eggs,” said U of C paleontologist Darla Zelenitsky. “Because of that, it has been very difficult to tell how dinosaurs incubated their eggs.”

However, a new method of egg analysis used by Zelenitsky and MSU paleontologist David Varricchio may allow researchers to learn more about these extinct animals.

“We looked at the details of the eggshells to see how these particular dinosaurs may have incubated their eggs,” said Zelenitsky. “We did this by comparing the eggshells of the dinosaurs to those of crocodiles and birds and found that they are closer to birds.”

Zelenitsky and Varricchio chose to research the dinosaur Troodon formosus, a person-sized carnivore found in fossil formations in both Alberta and Montana. Troodons belonged to a group of dinosaurs known as maniraptora and shared many similarities to modern birds. 

“These dinosaurs, Troodons, are closely related to birds,” said Zelenitsky. “They are one of the more interesting species to look at from North America.”

The porosity of the Troodon eggshells led to the conclusion that the dinosaur did not bury the eggs completely, like crocodiles, but instead made direct contact with the eggs during brooding — a feature that further links Troodons with modern birds. With evidence like this being discovered every year, there is now little debate in the scientific community about the link between dinosaurs and birds.

“There used to be a camp that thought that birds were related to reptiles other than dinosaurs, but that was a very small percentage of the paleontological community,” said Zelenitsky. “Since the discovery of so many feathered dinosaurs, as well as other discoveries in respect to anatomy and behaviour, there really is no question that birds are the descendants of dinosaurs.”

Zelenitsky now hopes to use her research methods to determine the brooding behaviour of different groups of dinosaurs, which may provide further understanding into the origin of birds.

“We’re revising the methods we used and looking at not just Troodons, but other dinosaurs as well,” said Zelenitsky. “Anything from sauropods and hadrosaurs, which are only distantly related to birds, to small theropods — we will possibly be able to see how their nesting changed through evolution.”