Examination of fosillized eggshells reveal the nesting behavours of various dinosaur species
An estimated 150 million years old fossilized dinosuar eggshells offered amazing insight into the nesting behavior of the primitive animal.
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The eggshells fragments consist of 29 different species of dinosaurs and a close examination of these eggshells reveals that most dinosaurs used to cover their eggs with dirt and vegetation, similar to the way the crocodiles do.
But surprisingly some small theropods applied another tactic that was different from the rest. They laid their eggs in nest and kept them uncovered like the modern birds today use to have.
“The evolution of open nest and brooding behavior could have allowed small theropod dinosaurs and obviously birds to move to other nesting locations other than on the ground” and this enabled them to survive over the years. Study co-researcher Darla Zelenitsky, an assistant professor of paleontology at the University of Calgary in Canada said in a statement.
For years, scientists wanted to know what kind of nests dinosaurs used to create for their eggs but they were unable to find out out due to lack of evidences. Eggshells are something too fragile to survive and preserve in the form of fossils.
“Dinosaur nest structures and nesting materials are usually not preserved in the fossil record,” said lead author Kohei Tanaka. “In the past, this lack of data has made working with dinosaur eggs and eggshells extremely difficult to determine how dinosaurs built their nests and how the eggs were incubated for hatching young.”
These egg remains have now provided an opportunity to the researchers to have a close look at shells and compare them with their closest living relatives, birds and crocodiles. They examined porosity or emptiness in the eggshells of dinosaurs as well as 120 modern species of birds and crocodiles.
“Fossil eggs are more challenging to study because fossil specimens are often incomplete,” said Tanaka. “However, some of the microscopic features of the eggshell, such as prosody are preserved, and can be used to infer the types of nests in dinosaurs in the absence complete nests.”
Birds lay eggs in open nests and their eggshells have low porosity. In other words, they have fewer holes in the shells that allow less vapor and gas exchange between the outside environment and the embryo.
While buried eggs, a hatching technique which is normally applied by crocodiles, result in large or more pores on shells.
Researchers found that most dinosaurs, such as the long-necked sauropods, had high-porosity eggs and likely buried their eggs in nests while advance theropods such as the bird-like maniraptorans, incubated eggs in open nests.
“We don’t have eggs for every species of dinosaur, but the more primitive dinosaurs have these buried nests and the more advanced maniraptoran theropods, which are closest relatives of birds, laid open-nest eggs that are exposed.” Zelenitsky said.
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“It was probably not until modern-looking birds that open nests with fully exposed eggs came to be.” Study concludes.