The first member of the family Ferugliotheriidae to be discovered, "Ferugliotherium windhauseni", was named in 1986 by Argentinean paleontologist José F. Bonaparte on the basis of a tooth from the Late Cretaceous Los Alamitos Formation of Argentina. Bonaparte placed "Ferugliotherium" as the only member of the new family Ferugliotheriidae, which he tentatively assigned to the order Multituberculata, a large group of extinct mammals (distinct from both monotremes and therians, the two major groups of living mammals) that was particularly widespread in the northern continents (Laurasia), but had never previously been found in the south (Gondwana). In 1990, Bonaparte named another species, "Vucetichia gracilis", from Los Alamitos. He placed it in the family Gondwanatheriidae, together with "Gondwanatherium", another Los Alamitos mammal, within the order Gondwanatheria, which also contained the family Sudamericidae, then with the single genus "Sudamerica". Bonaparte considered the gondwanatheres to be probably most closely related to the xenarthrans (sloths, armadillos, and anteaters) within a group called Paratheria.