Dinosaur eggs had strong shells and could become fossils. The lengths of these oval eggs range from 3cm to 56cm, with slightly different shapes. They are often found in nests.
Many kinds of dinosaur bones and eggs were excavated in Eren Basin, Inner Mongolia. In the 1970s, three nests of dinosaur eggs and many egg shells were discovered in northern Jilantaiyanchi. The nests were all buried in purple sandstone and were some 100-200 meters from each other. They are similar to the eggs of the modern terrapin. The dinosaur eggs were oval-shaped, 142mm long and 138mm wide, and about the same size.
In 1989, a nest of 13 well-preserved fossil dinosaur eggs was discovered in formations of cretaceous sandstone in Urad Rear Banner, Inner Mongolia. The eggs were found with their large ends pointing inward and their small ends pointing outwards. They were 17-18cm wide and 778cm long with 1-2cm thick shells. The ends of each egg were similar, with small round ends slightly bigger than less round ends.
