The study focuses on an excavation in South Africa where a 190-million-year-old nesting ground was found.
University of Toronto Mississauga paleontologist Robert Reisz says the site reveals clues about the evolution of reproductive behaviour in early dinosaurs.
Reisz and his co-authors — including David Evans of the Royal Ontario Museum and a group of international researchers — say the newly unearthed site predates any previously known by 100 million years.
Their study describes clutches of eggs, many with embryos, as well as tiny dinosaur footprints — evidence that hatchlings remained at the nesting site long enough to at least double in size.
The study was published Monday in the Proceedings of the National Academy of Sciences.
The fossils were found in sedimentary rocks from the Early Jurassic Period in the Golden Gate Highlands National Park in South Africa.
At least ten nests have been discovered at several levels at the site, each with up to 34 round eggs in tightly clustered clutches. Reisz believes more could be buried under the rock.
This dinosaur in question is Massospondylus, a relative of the giant, long-necked sauropods of the Jurassic and Cretaceous periods.
The study says the distribution of the nests in the sediment suggest the dinosaurs returned repeatedly to the site and likely assembled in groups to lay their eggs.
This is the oldest known evidence of such behaviour in the fossil record, the study's authors said.
“Even though the fossil record of dinosaurs is extensive, we actually have very little fossil information about their reproductive biology, particularly for early dinosaurs,” said Evans of the Royal Ontario Museum in Toronto.
Some of the fossilized eggs and embryos from the site are currently on display at the museum in Dinosaurs Eggs and Babies: Remarkable Fossils from South Africa. The exhibition runs until May 1.