Few specimens of Tachira Antpitta are in existence, but it is presumed to be monomorphic. Similarly, it is presumed to present the typical Grallaria silhouette if seen in life. Otherwise it is fairly boldly marked with a gray crown and otherwise olive brown upperparts, all of which are finely scaled with black. The throat is olive brown with fine black spotting, bordered laterally by a bold whitish or creamy malar stripe. The upper breast is buff brown, blending to a dull white belly and with increasingly distinct fine black barring. The crissum is a rich buffy ochraceous.
Tachira Antpitta is very similar to the nominate subspecies of Scaled Antpitta (Grallaria guatimalensis guatimalensis), but has a dark throat, more whitish (rather than ochraceous) lower breast and belly which bear fine black barring, and a less evident or absent crescent-shaped marking across the upper breast.
Both sexes of Tachira Antpitta have a brown forecrown blending to a gray hindcrown and nape, with all these areas scaled black. The upper parts are otherwise olive brown, including the rump, tail, and wings. Apart from the tail and wings, the upperparts are similarly narrowly scaled black. The uppertail coverts are cinnamon brown. The chin and throat are olive brown with black tipped feathers, while the upper breast is buff brown, becoming dull whitish on with indistinct gray lines on the lower breast. The flanks are buffier and less strongly barred, while the crissum is rich buff. The head is further marked with a broad, light-buff malar stripe and a central throat spot of similar color (Krabbe and Schulenberg 2003).
Wetmore and Phelps (1956) described the holotype as:
"Pileum to the level of the posterior margin of the eyes sepia, becoming Saccardo's umber on forehead, with each feather edged narrowly with black around the exposed margin; posterior part of crown and hindneck neutral gray, also margined with black, except in the line of an indistinct superciliary, extending from the center of the eye back above the ear coverts, in which the black edging is absent or very slightly evident on a few of the feathers; feathers of this superciliary anteriorly becoming whitish basally, tipped with buffy brown, and extending thus to base of bill behind nostril; back, scapulars and rump between light brownish olive and brownish olive, the feathers edged narrowly with black; upper tail coverts cinnamon-brown; rectrices sepia, with the exposed webs bister; wing coverts and outer webs of secondaries olive-brown; primaries fuscous-black, the outer webs edged with olive-brown; loral area mixed blackish and buffy brown; space beneath eye clove brown, with the anterior feathers whitish to buffy brown basally; ear coverts and sides of neck olive-brown; a pronounced rictal streak extending from the base of the mandible to the level of the posterior margin of the ear coverts, with the feathers dull white basally, washed with cream-buff near the tips, and tipped with black; throat and upper foreneck with the feathers olive-brown basally, merging into dull black at the tips; lower foreneck with a broad spot in which the feathers basally are dull white becoming cream-buff, with an indefinite line of dull black separating the lighter basal color from the buffy brown tip; upper breast buffy brown with concealed whitish shaft streaks; lower breast and sides dull whitish, barred with mouse gray, the barring merging with the lighter color so that while distinct, the lines are not sharply delimited, the whole washed lightly with clay color; flanks with the barring more indefinite and the clay color wash more evident; lower abdomen dull whitish washed with chamois; under tail coverts slightly paler than buckthorn brown ; under wing coverts ochraceous-buff', with the outer margin olive brown; axillars sepia, edged with cinnamon-buff; inner webs of innermost primaries and outer secondaries with a slight wash of chamois. Bill dull black, becoming pale olive-buff at base of mandible; tarsi and toes hair brown (from dried skin)."
Bill: black, but base of mandible pale, olive buff.
Tarsi and toes: brown.
Bare parts color data from Wetmore and Phelps (1956) and Krabbe and Schulenberg (2003).
Total length: 15-19 cm (Meyer de Schauensee and Phelps 1978, Hilty 2003, Krabbe and Schulenberg 2003, Restall et al. 2006, Ridgely and Tudor 2009).
Linear measurements (from Wetmore and Phelps 1956; n = 1, holotype, male):
Wing length: 97.8 mm
tail length: 38.7 mm
bill length (culmen from base): 26.8 mm
tarsus length: 43.7 mm