 It is possible, however, that the faunal assemblage at El Cobre Canyon represents two horizons, with species including "Limnoscelis paludis" and "Desmatodon hollandi" inhabiting the lower (Late Carboniferous) assemblage, and other species including "Edaphosaurus novomexicanus, Platyhystrix rugosus, Sphenacodon ferox, Aspidosaurus novomexicanus, and Ophiacodon navajovicus" inhabiting the upper (Early Permian) assemblage.