Egg to Adult
Huge dinosaurs are often assumed to have laid giant eggs. In films they are often depicted to be many times bigger than a human. However, there is a restriction to the maximum size of the egg an animal can lay. In general, as the animal gets bigger, the eggshell becomes thicker. If an eggshell is too thick, the baby cannot hatch out. The thickest dinosaur eggs come from sauropods. These eggs could have shells up to 9 millimeters thick and eggs that are able to contain 5.5 liters of fluid. A meter-long egg would be several centimeters thick, making respiration and hatching near impossible. Imagine how thick an egg several times the size of a human would be!

One might ask therefore how a sauropod from an 18 centimeter diameter egg could grow to a 30 meter long animal weighing about 20 tons. Sauropods and other dinosaurs grew very fast. Sauropods may have reached their adult size in only 15-20 years.