They have been found across Asia and the US, as well as in Spain, France, and Argentina, with ages ranging from lower Cretaceous to the Paleocene.

[2] In 1994, his hypothesis was confirmed when Norell et al. discovered embryonic remains of an Oviraptorosaur inside an elongatoolithid egg.

[6] In 1975, Chinese paleontologist Zhao Zikui devised a formal classification system for fossil eggs, in which he created a new oogenus for "Oolithes" elongatus: Elongatoolithus.

[1] Several oviraptorosaurs have been found in association with elongatoolithid eggs,[9] including some specimens still inside the mother.

[9][14] All of them have their arms spread out over the eggs in a bird-like posture, and the parent's body would effectively cover the entire nest.

Also, the clutches were proportionally large compared to the size of the adult, which suggests a polygamous system, similar to modern paleognaths, in which multiple females contribute eggs to a single nest which is then cared for by the father.

This shows that oviraptorosaurs had two functional oviducts (unlike birds, which have only one), and would produce two eggs at a time.

[18] Elongatoolithidae contains the oogenera Nanhsiungoolithus, Elongatoolithus, Macroolithus, Macroelongatoolithus, Ellipsoolithus, Trachoolithus, Heishanoolithus, Ornitholithus, Paraelongatoolithus, Undulatoolithus,[1] and Rodolphoolithus.