Early birds like Archaeopteryx were far too heavy to sit on their eggs without cracking them. The conclusion holds true for non-bird dinosaurs too, leading to fresh doubts about how to interpret spectacular fossils that appear to show dinosaurs brooding their eggs.
Most birds today lay eggs with strong, hard shells. This strength is necessary because many birds practice contact incubation – meaning the adult rests its body weight directly on the eggs. But just because modern bird eggs can support the weight of a brooding adult it doesn’t necessarily follow that ancient bird eggs could, says …