Due to the nature of the bones being jumbled into sandstone nodules, and completely disarticulated, it has been suggested that "Protoavis" was reworked from later sediments. However, a basic stratigraphic principle, the "principle of inclusions", is a special case of the principle of cross-cutting relationships. It states that rock has to exist before it can be included in other sedimentary rock. Reworking is the process of weathering fossils or rock containing fossils out of rocks already present, transporting them, and redepositing them in sediments which are later lithified as new sedimentary rocks. Since the Jurassic rocks occurred "after" the Triassic sediments of the Dockum Group, they could not have been reworked into the Dockum sediments as inclusions.