Arriagadoolithus patagoniensis was named by Agnolin et al. (2012) [The unique combination of following microstructure characters distinguish Arriagadoolithus from remaining egg-types: three layers (external, prismatic, mammillary) of distinct calcite texture in eggs with a diameter of ca. 70 mm (?maximum width) and unknown length; average value of eggshell thickness 1 mm; variable ornamentation of the outer shell surface including low irregular-shaped nodes, isolated node-like ridges, and low long ridges interconnected with each other to form a net, thus the combination of plexi-ramo-tuberculate and unique dendro-reticulate ornament may represent autapomorphic character of this oospecies; microlaminated external layer (90–100 μm) with two distinct textures; unevenly distributed squamate texture in the prismatic layer; visible prismatic columns, tubocanaliculate and obliquicanaliculate pore system with funnel-like openings on the outer surface; large pneumatic canals expanded into spatial chambers (up to 270 μm in diameter) within the prismatic layer (this latter feature may represent an autapomorphy of this oospecies); prismatic to mammillary layer thickness ratio 4.9:1 to 4.4:1]. It is considered to be a form taxon. Its type specimen is MPCA 1290, an egg, and it is a 3D body fossil. Its type locality is Salitral Ojo de Agua (general), which is in a Campanian/Maastrichtian fluvial sandstone in the Allen Formation of Argentina.