The Patagonian Forest Earthcreeper (Upucerthia saturatior) is a distinctive furnariid that inhabits the Patagonian forests of central-western Argentina and adjacent Chile within the Nothofagus Center of Endemism. After its description as a species in 1900, U. saturatior was quickly subsumed, without comment or study, as a subspecies of the Scale-throated Earthcreeper (U. dumetaria), a treatment followed by most subsequent authors. On the basis of an apparent geographical cline within U. dumetaria and a reanalysis of the morphology and plumage of reported intergrades between U. dumetaria and U. saturatior, there is no evidence of intergradation between these taxa. Upucerthia saturatior differs from U. dumetaria by its song (“p-p-tirik-tirik-tirik-tirik-tirik-tiruk” vs. “pli-pli-pli-pli-pli . . .”), which is also three times faster in dumetaria, call (“pep” vs. “keep”), morphology (smaller and darker with a short black bill vs. larger and paler with a long brown bill), distinctive tail pattern, breeding habitat (forest borders vs. shrubby steppe and open highland habitats), and migration patterns (trans-Andean vs. north-south). These differences exceed those between U. jelskii and U. albigula and are far greater than those between U. jelskii and U. validirostris; they overwhelmingly support ranking U. saturatior as a full species. The existence of a forest-dwelling species of Upucerthia parapatric to an open-country Upucerthia provides an opportunity for testing the role of habitat shift between dry exposed habitats and forest habitats (and vice versa) during speciation.