The Curve-billed Reedhaunter (Limnornis curvirostris) and the Straight-billed Reedhaunter (Limnoctitesrectirostris) are marsh-dwelling ovenbirds that were first collected by Charles Darwin in Uruguay.Each has a limited distribution in southernmost Brazil, Uruguay, and northern Argentina, within which thebirds occupy very distinct habitats. Originally described as congeners because of overall similarity of plumage,the two species have been treated as close relatives through most of their history despite obviousstructural differences. We analyzed DNA sequences from three different genes of these species, comparingthem with a wide variety of other species of Furnariidae and several outgroup taxa. Limnoctites rectirostrisbelongs among the species traditionally placed in Cranioleuca, being most closely related to the marshdwellingSulphur-throated Spinetail (C. sulphurifera) among the species we sampled. This is supported byvocalizations and nidification. Limnornis curvirostris forms a clade with the Wren-like Rushbird (Phleocryptesmelanops), with the Sharp-tailed Streamcreeper (Lochmias nematura) as a rather distant sister-taxon. A closerelationship between Limnornis and Phleocryptes is supported by the apparently unique nest architecture andblue-green egg color.