Parvoolithus

Parvoolithus is an oogenus of Mongolian fossil egg. They are known from a single small, smooth egg, which cannot be assigned to any known oofamily. It is very similar to the eggs of modern birds in many aspects; in fact, a cladistic analysis by Zelenitsky and Therrien found it to be a sister taxon to the guinea fowl (genus Numida), indicating that they represent the eggs of birds, rather than a non-avialan theropod.