The sole member of the genus Ramphocaenus is very widely distributed through the lowlands of Middle and South America, from southern Mexico south to Panama, and both east and west of the Andes, with a disjunct population in the Atlantic Forest of Brazil. Compared with the relatively tiny body, both the bill and the tail appear very long, especially the former. Most of the upperparts are dull to warm brown, with a largely black tail, a slight pale supercilium, and largely dull underparts. As many as 15 subspecies are generally recognized; variation principally focuses on underparts coloration and pattern, with some populations having dark-streaked throats and being much warmer-colored over the face and below. The Long-billed Gnatwren can be rather difficult to observe as it generally remains in dense cover, often some distance above the ground, although its rattled song draws the attention.