The bowl-shaped nest measuring 2.3 feet in diameter and containing the remains of Protoceratops andrewsi dinosaurs was found in Tugrikinshire, Mongolia.
"Finding juveniles at a nest is a relatively uncommon occurrence, and I cannot think of another dinosaur specimen that preserves 15 juveniles at its nest in this way," said David Fastovsky, a University of Rhode Island professor of geosciences.
An analysis of the 70-million-year-old fossils found all 15 were about the same size and had achieved the same state of growth and development, suggesting they represent a single clutch from a single mother, a university release said Monday.
They were likely less than a year old when they died, Fastovsky said.
"Death likely occurred during a desert sandstorm," he said. "My guess is that the initial and present-day dryness contributed significantly to the superb preservation, not just of Protoceratops, but of all the fossils from this unit."