 Hershkovitz identified "Holochilus" as one of the members of a "sigmodont" group of American rodents, also including "Sigmodon", "Reithrodon", and "Neotomys", on the basis of its flat-crowned molars, which are lophodont (the crown consists of transverse ridges).In 1981, "H. magnus" was also recognized in the Late Pleistocene of Buenos Aires Province, Argentina, and in 1982 it was recorded from Rio Grande do Sul in southern Brazil.In a 1980 article, Argentine zoologist Elio Massoia recognized the resemblance between Winge's "Hesperomys molitor" and Hershkovitz's "Holochilus magnus", and recommended that the former be reclassified as a species of "Holochilus", "Holochilus molitor".