The lineated foliage-gleaner is long and weighs . The sexes have the same plumage. Adults of the
nominate subspecies S. s. subalaris have a discontinuous light buff
supercilium that extends to the nape; the rest of their face is blackish brown with small buff markings. Their crown is dark brown with thin buff streaks. They have a narrow ill-defined darker brown collar with wide buff streaks. Their back is rich dark brown with long thin buff streaks, their rump a plain rich dark brown, and their uppertail
coverts dark brown with chestnut tips. Their tail is dark chestnut and their wings are rich dark brown with light
rufescent brown at the bend. Their throat is buff with blurry brownish streaks, their breast dark brown with buff streaks, their belly and flanks a slightly paler brown with thinner streaks that disappear towards the rear, and their undertail coverts the paler brown with wider ochraceous streaks. Their iris is brown to dark brown, their
maxilla dark brown to black, their
mandible variable from grayish horn to ivory, and their legs and feet olive-green to greenish gray. Juveniles are generally brighter overall than adults, with a blacker cinnamon-streaked crown, a more reddish brown back, black speckles on the chin, a more ochraceous cinnamon supercilium, neck, and breast, richer brown flanks, and cinnamon-brown undertail coverts. Subspecies
S. s. lineata has a paler but more rufescent back than the nominate, a heavily marked buffy yellow throat, and slightly more olivaceous underparts with thinner streaks.
S. s. tacarcunae is similar to
lineata but with a darker more olive-brown back, a paler more yellowish throat, and grayer underparts. Compared to the nominate,
S. s. striolata has a slightly darker and less rufescent crown with heavier buff streaks, wider streaks on the back, less rufescent wings, a paler and less buffy throat, and wider and more extensive streaks on the underparts.
S. s. olivacea has a more blackish brown crown than the nominate and the most olivaceous underparts of all the subspecies.
S. s. mentalis has a blacker crown than the nominate, more conspicuous streaks on the crown and nape, a darker and more buffy yellow throat, and slightly more rufescent underparts with stronger streaks. ==Distribution and habitat==