Dinosaur egg fossils, or oofossils, can be found in strata dating to between 233 million years ago (the mid-Triassic period of the Mesozoic era) to 66 million years ago (the late Cretaceous period of the Mesozoic era). After this point, the only dinosaur egg fossils that can be found are those belonging to birds, the only extant dinosaur group. Egg fossils can rarely be identified to the species that laid them.
