Oldest Ever Dinosaur Nesting Site Found in South Africa

Close-up of embryonic skeleton of Massospondylus from clutch of eggs at the nesting site. The head was pushed out of the egg after death, probably because of gases produced by decay. (D. Scott)

A prosauropod nesting site has been discovered from 190 million years ago. It is 100 million years older than the previously known site, according to new research published in the Proceedings of the National Academy of Sciences.

The site is multileveled with at least 10 nests belonging to dinosaurs of the genus Massospondylus, which had long necks and lived during the Jurassic and Cretaceous periods.

Each nest contains tight clutches of up to 34 fossilized eggs, many of which contain embryos, and there are also hatchling foot- and handprints, showing that the young dinosaurs stayed at the site until they had grown at least double in size.

“The eggs, embryos, and nests come from the rocks of a nearly vertical road cut only 25 meters [82 ft.] long,” said study co-author Robert Reiszy at the University of Toronto–Mississauga in a press release. “Even so, we found 10 nests, suggesting that there are a lot more in the cliff, still covered by tons of rock.

“We predict that many more nests will be eroded out in time as natural weathering processes continue.”

The nest groupings suggest that the site was used repeatedly, a behavior called “nesting fidelity,” and the dinosaurs may have aggregated before laying, which is called “colonial nesting.”

“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 David Evans at the Royal Ontario Museum in the release.

This may be the oldest known example of colonial nesting. Laying females would have been six meters long, and their eggs were only about 6 to 7 centimeters wide, indicating that the mothers probably organized the eggs carefully during laying.