Dinosaur eggs are preserved as oblate to semispherical structures that also show distinctive shell microstructures. In some cases, dinosaur eggs have preserved parts of embryonic dinosaurs, which can help to correlate a dinosaur egg with a species of dinosaur, such as Maiasaurus and Oviraptor . However, the egg itself is the trace fossil, whereas any bodily remains of an embryo constitute a body fossil. An assemblage of eggs in close association with one another in the fossil record is often regarded as part of a clutch , meaning that these eggs represent one egg-laying episode. This dinosaur egg, attributed to the theropod Oviraptor , is partially crushed but still shows the asymmetrical and oval shape associated with this species' eggs.
Shell fragments are to the right of the egg.
This pair of partially preserved dinosaur eggs come from the Late Cretaceous Nanxiong Basin of southeastern China, a locality that has yielded thousands of dinosaur eggs. A nest is a biogenic structure typically containing a clutch and commonly represented by an arrangement of eggs in a semicircular or spiraled pattern. In some instances, a raised area surrounding the eggs will denote the border of the nest. No evidence exists indicating that any dinosaurs lived in trees, let alone built nests in trees. Nests are sometimes found containing hatchlings or other remains of juveniles, which assists in the identification of the parental species.