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Oldest Dinosaur Embryos

An adult skeleton of Lufengosaurus

An adult skeleton of Lufengosaurus, a species of dinosaur from which the oldest dinosaur embryos have been found.

By Stephen Luntz

The world’s oldest dinosaur embryos have been found in southern China, providing insight into the developments of the largest creatures ever to roam the land.

The embryos are named Lufengosaurus after the nearest city to the location where the discovery was made. Lufengosaurus was a sauropodomorph, a clade that included Plateosaurus, which grew to 10 metres long.

The rocks in which the embryos were found are 190–197 million years old, dating them to the Lower Jurassic.

All the bones found are from the same species, but they come from adults, young and embryos, sometimes with egg-shell fragments mixed in. Low-energy flooding disturbed the bed sufficiently to mix many of the bones.

The Nature paper in which the discovery was announced begins, “Fossil dinosaur embryos are surprisingly rare,” but third author Dr Eric Roberts of James Cook University says that “the surprising things is that we find any at all”.

The differing stages of development of the bones suggests that the eggs from which they came were laid weeks apart, providing the scientists with an opportunity to observe their development over time. “The assumption is that these animals were not spending a great deal of time in the egg, similar to modern birds and crocodiles,” Roberts says.

Evidence could be seen of muscles becoming active while the dinosaurs were still in the egg, suggesting that they moved around before hatching.

The high ratio of vascular spaces in the vertebrae suggests very rapid growth, which Roberts says may indicate a specialised diet and a symbiotic relationship with bacteria to allow effective digestion of food once the animals left the egg.