Paleontologists have discovered the oldest known site of dinosaur fossils in Golden Gate Highlands National Park, South Africa.

The details of the discovery were published Monday in the Proceedings of the National Academy of Sciences. Dating back to 190 million years ago, the site includes several dinosaur nests, eggs, hatchings, and remains of adults for the dinosaur species known as Massospondylus.

The plant-eating species was a predecessor of the largest animals to ever walk the Earth – the long-necked sauopods, such as a Brachiosaurus.

An international team of scientists and researchers excavated the nesting ground. Researcher Robert Reisz, a paleontologist at the University of Toronto at Mississauga, described the find to Discovery News.

"The eggs, embryos and nests come from the rocks of a nearly vertical road cut only 25 meters (82 feet) long," said Reisz. "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."

Very small footprints from young dinosaurs dotting the area revealed significant clues about the growth and evolution of early dinosaurs, researchers said. The hatchery and prints offer the oldest-known evidence that dinosaurs remained in nests until they were at least doubled in size.

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The skeletal remains indicate that the dinosaurs had a very small head and an extremely long neck, and while hatchlings walked on all four legs, adults were bipedal.

"The transition from four legs to two during an individual's lifetime is a very unusual growth pattern that we rarely see in animals, but we do see it in humans."

The eggs and nests were painstakingly unearthed as the eggshells are extremely delicate at less than 100 microns in thickness, or less than the width of a human hair.

"We literally spent days and days searching for the eggs and nests, spending most of our time on our hands and knees," said Reisz. "But once we were able to recognize what to look for, we found four nests within 10 minutes."

South Africa appears to have been a common region for Massospondylus to hatch, and possibly for other species as well. Paleontologists are slowly uncovering embryos within the eggs, and have several in different stages of development. They are currently in the process of comparing the embryos to those found in other nests, marking the first study of different embryological stages in a dinosaur.