Massospondylus

MEET THE ANIMAL

Meet Massospondylus

Massospondylus carinatus was a plant-eating dinosaur from Early Jurassic southern Africa. Eggs found in South Africa’s Golden Gate Highlands National Park preserve tiny embryos, giving researchers evidence from before hatching as well as from larger animals. These fossils are delicate. Their size makes ordinary preparation difficult, and a baby’s developing skull cannot be treated as a scaled-down adult head. [S1]

Powerful X-rays from a synchrotron, a facility that generates an intense beam, allowed scientists to reconstruct the embryos’ skulls in three dimensions. They compared the developing bones with those of living reptile relatives. This analysis suggested that the embryos were substantially earlier in development than previously thought, rather than almost ready to hatch. Their apparent maturity was a conclusion to test, not something obvious from finding an egg. [S1]

The developing jaws contained two kinds of teeth. Researchers interpreted one simple set as temporary teeth that would be lost before hatching; the other resembled the teeth used later. The embryos consequently record a changing body inside the egg, not just the starting point of a familiar adult skeleton. Their preservation reveals development in detail while leaving the behavior of the adults around these particular eggs unresolved. [S1]