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World's oldest eggs shed new light on dinosaur evolution

Press Trust of India  |  Toronto 

The world's earliest known eggs -- dating back 195 million years -- have revealed new information about the of in the gigantic animals, scientists say.

Researchers led by the Mississauga in Canada studied the fossilised remains of eggs and eggshells discovered at sites in Argentina, and

At 195 million years old, they are the earliest known eggs in the fossil record, the researchers said.

They were all laid by a group of stem sauropods -- long-necked herbivores that ranged in size from four to eight metres in length and were the most common and widely spread dinosaurs of their time.

"Reptile and mammal precursors appear as skeletons in the fossil record starting 316 million years ago, yet we know nothing of their eggs and eggshells until 120 million years later," said from the

"It's a great mystery that eggs suddenly show up at this point, but not earlier," Reisz said in a statement.

According to Koen Stein, a at in Belgium, the eggs represent a significant step in the of

Spherical, and about the size of a goose egg, these eggshells were paper-thin and brittle, much thinner than similar-sized eggs of living

"We know that these early eggs had hard shells because during fossilisation they cracked and broke, but the shell pieces retained their original curvature," said Stein, of the project.

The researchers analysed shell thickness, membrane, mineral content and distribution of pores, looking for clues about why these early eggs might have developed hard shells.

The study shows that hard-shelled eggs evolved early in dinosaur with thickening occurring independently in several groups, but a few million years later other reptiles also developed hard-shelled eggs.

One possibility is that hard and eventually thicker shells may have evolved to shield fetal dinosaurs and other reptiles from predators.

"The hard shells would protect the embryos from invertebrates that could burrow into the buried nests and destroy them," Reisz added.

(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)

First Published: Fri, March 15 2019. 12:15 IST