Originally experts thought the nest, found in Montana, US, in the 1990s, belonged to a plant-eating hadrosaur, or duck-billed dinosaur. But a new examination suggests it was actually the work of a small theropod, a carnivorous two-legged dinosaur.

“Based on characteristics of the eggs and nest, we know that the nest belonged to either a caenagnathid or a small raptor, both meat-eating dinosaurs closely related to birds,” said researcher Dr Darla Zelenitsky, from the University of Calgary in Alberta, Canada. “Either way, it is the first nest known for these small dinosaurs.”

The fossil nest is a mound of sand about half a metre across and weighing as much as a small person.

Eggs were laid two at a time on the sloping sides of the mound, forming a ring around its flat top. The nesting dinosaur would have sat here to brood its clutch.

Co-investigator Francois Therrien, curator of dinosaur palaeoecology at the Royal Tyrrell Museum in Drumheller, Alberta, said: “Based on the features of the nest, we know that the mother dug in freshly deposited sand, possibly the shore of a river, to build a mound against which she laid her eggs and on which she sat to brood the eggs.

“Some characteristics of the nest are shared with birds, and our analysis can tell us how far back in time these features, such as brooding, nest building, and eggs with a pointed end, evolved – partial answers to the old question of which came first, the chicken or the egg.”

The research is reported in the journal Palaeontology.

ANI

Views: 118