Washington, Nov 14 : Scientists have solved a 77-million-year old mystery of a unique fossilized nest and eggs, by determining the egg layer to be a small theropod (meat-eating) dinosaur.
The scientific detective work was conducted by University of Calgary (U of C) and Royal Tyrrell Museum researchers.
"Working out who the culprit was in this egg abandonment tragedy is a difficult problem to crack," said Darla Zelenitsky, U of C paleontologist and the lead author of the research.
"After further investigation, we discovered that this find is rarer than we first thought. It is a one of a kind fossil. In fact, it is the first nest of its kind in the world," she added.
According to Zelenitsky, she first saw the nest in a private collection, which had been collected in Montana in the 1990s.
The nest was labeled as belonging to a hadrosaur (duck-billed) dinosaur, but she soon discovered it was mistakenly identified.
In putting all the data together, she realized they had a small theropod (meat-eating) dinosaur nest.
"Nests of small theropods are rare in North America and only those of the dinosaur Troodon have been identified previously," said Zelenitsky.
"Based on characteristics of the eggs and nest, we know that the nest belonged to either a caenagnathid or a small raptor, both small meat-eating dinosaurs closely related to birds. Either way, it is the first nest known for these small dinosaurs," she added.
The nest tells scientists more about the behaviour of the animal as well as some valuable information relating to the characteristics of modern birds.
"Our research tells us a lot about the dinosaur that laid the eggs and how it built its nest," said Francois Therrien, a co-investigator in the study and curator of dinosaur palaeoecology at the Royal Tyrrell Museum in Drumheller.
The fossil nest is a mound of sand about half a metre across and weighing as much as a small person.
The eggs were laid two at a time, on the sloping sides of the mound, and form a ring around its flat top, where the nesting dinosaur would have sat and brooded its clutch.
"Based on 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," said Therrien.