The oldest dinosaur nursery has been found, dating back to 190 million years ago, in South Africa, and researchers say that little baby footprints were uncovered that gives significant clues about the evolution of family behaviors.
The newly unearthed clutches of eggs, many with embryos inside, belonged to the plant-eating dinosaur Massospondylus, a prosauropod, or predecessor of the largest animals to ever walk the Earth, long-necked sauropods such as Brachiosaurus.
The international team of researchers conducted their excavation in the Golden Gate Highlands National Park in South Africa. The nesting ground, now largely covered in reddish-brown muddy siltstone, predates previously known nesting sites by 100 million years.
“The eggs, embryos and nests come from the rocks of a nearly vertical road cut only 25 meters (82 feet) long,” said researcher Robert Reisz, a paleontologist at the University of Toronto at Mississauga. “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 eggs and nests proved difficult to unearth because the eggshells are extremely delicate at less than 100 microns in thickness, or less than the width of a human hair, making it easy to inadvertently destroy them. “We literally spent days and days searching for the eggs and nests, spending most of our time on our hands and knees, but once we were able to recognize what to look for, we found four nests within 10 minutes,” Reisz told LiveScience.
The nests unearthed to date each held up to 34 round eggs in tight clusters. The skeletal remains of the mothers suggest they were about 20 feet (6 meters) long, while their eggs were only about 2.3 to 2.7 inches (6 to 7 centimeters) wide. The mothers carefully arranged these eggs, the researchers say, basing this on the high level of organization of the nests and eggs.
From the fine-grained nature of the sediments holding the eggs, the researchers think the dinosaur nests were built near a lake or a slow-moving river.