A team led by Robert Reisz of the University of Toronto-Mississauga have identified the oldest-known dinosaur embryos, which belonged to a species that lived 190 million years ago, the BBC reports. The eggs of Massospondylus, an ancestor of giant sauropods like Brontosaurus, were dug up in South Africa in 1976, and contain well-preserved embryos. Using these embryos, they reconstructed what dinosaur babies might have looked like when alive. These dinosaurs belong to a group known prosauropods, big, four-legged dinosaurs with long necks. The 20-cm long skeletons inside the eggs were going to hatch, but never had the chance. They would have had long front legs, so they would have walked on all fours, rather than two legs, like adults. Their heads were also disproportionately big. They’re the oldest embryos ever found of a land-dwelling vertebrate.