Dinosaurs made eggs the same way reptiles and birds do today. Females produced them inside their body. Some dinosaurs laid as many as 21 eggs in a single nest. Dinosaurs laid eggs in clusters, sometimes in a spiral in a nest they dug out and covered over with vegetation to keep it warm. They laid eggs that were oval, round or football-shaped and as small as tennis balls and as long as 18 inches.
Dinosaur eggs come in many shapes and sizes from cannonballs to giant footballs.
The biggest are 18 inches long and the smallest are the size of tennis balls. We've found as many as 21 eggs in one nest. The biggest dinosaur eggs we know are shaped like giant footballs and are about 19 inches long. They belong to a meat-eater from Asia called segnosaurus. The smallest dinosaur eggs are just a few inches across and more tennis ball-shaped and we don't know what dinosaur made them.