Anthracocarpon andinum, a new terricolous species, is described from northern Argentina. The most important differences from A. virescens (Zahlbr.) Breuss are in thallus morphology and size and shape of the ascospores. Anthracocarpon andinum develops a squamulose thallus covered by a sulcate epinecral layer. The squamules of A. virescens are smaller, thinner and covered by a thin and continuous epinecral layer. In addition, A. andinum has paler rhizines than A. virescens. Thallus thickness, spore width and length/width ratio of ascospores are significantly different for the two species.