A team of paleontologists from the United States, Canada and Argentina has analyzed the fossilized eggs of two different non-avian dinosaurs, Protoceratops and Mussaurus, and found that the eggs resembled those of turtles in their microstructure, composition, and mechanical properties. They've also found that hard-shelled eggs evolved at least three times independently in the dinosaur family tree. For many years there was scant fossil evidence of dinosaur eggs, and all known examples were characterized by thick, calcified shells -- leading paleontologists to speculate that all dinosaur eggs were hard-shelled, like those of modern crocodiles and birds. "The assumption has always...