Egg-cellent find.

Think the egg buried in the back of your fridge is old? Not compared with the 121-million-year-old egg recently unearthed by scientists in China. What's more, the fossilized (turned to stone) egg contains the perfectly preserved remains of a developing pterosaur (TER-uh-soar, flying reptile related to dinosaurs).

"It's an incredible find," says paleontologist (fossil scientist) Paul Sereno. Usually when an animal dies, it decays (breaks down into simpler parts) or is eaten by another organism. This either leaves no trace of the animal, or--at best--just its bones.

In this case, scientists believe a nearby volcano erupted, and debris covered the egg as it sat on an ancient lakeshore. Buried instantly beneath ash, the egg and developing pterosaur were sealed off before the reptile's remains could decay.

One secret revealed by the fossil? "We've never known how pterosaurs reproduced," explains Sereno. "Now we know that this [species]--and likely all [species of] pterosaurs--laid eggs." Case cracked!