Recently described, inconspicuous and rarely seen bird of rainforest canopy. Small and slender with a long tail; mostly dark gray with a broken white eyering, white belly, and white outer tail feathers. Inhabits canopy of tall forest, especially in regions with sandy soils. Usually seen with mixed-species flocks as it forages actively in outer foliage, sallying for insects and gleaning from leaves, moving long tail from side to side like other gnatcatchers. Thin and indistinct call notes are easily overlooked among calls of other species in flocks, but distinctive shape, active behavior, and long tail with extensive white should clinch identification. Extremely similar to other gnatcatchers of the Guianan Gnatcatcher complex, but no overlap in range. Distinguished from Tropical Gnatcatcher by uniform gray body plumage and lack of a black cap, and from Tooth-billed Wren by slimmer shape and smaller size, lacking any black barring in the plumage.