Description: Medium-sized canastero, about 17–18 cm long. It has a long, graduated tail ending in sharp points—a feature that gives it its scientific name (heterura, “distinct tail”)—which allows it to be distinguished from other canasteros. The plumage is brown on the back and crown, with wings and tail of an intense reddish-rufous tone, very visible in flight. The throat is whitish with fine gray streaks and a rufous-brown throat patch; the chest and belly are grayish cream, with browner flanks and ochraceous undertail coverts. It shows a faint light brown eyebrow, brownish face, and brown eyes. The bill is black on the upper mandible and pink on the lower, with a dark tip; the legs are black. Male and female are similar.

Geographical distribution: Inhabits the Andes of northern Bolivia and northwestern Argentina, in Jujuy, Salta, and Tucumán, where its records are scarce and localized, especially in Santa Ana (Jujuy) and Cuesta del Obispo (Salta). In Argentina, it was only confirmed in the 1990s, as specimens collected in 1914 in Tucumán had been misidentified, actually belonging to Asthenes pyrrholeuca. Today, its presence in Tucumán is almost a mystery.

Habitat: High Andean scrublands and grasslands, between 2,500 and 4,100 m a.s.l., especially in humid ravines with patches of alder (Alnus acuminata), queñoa (Polylepis spp.), and grasslands dominated by Festuca. Prefers slopes with scattered shrubs and rocky or tufted grass areas, as well as dense thickets.

Feeding: Insectivorous. Feeds on arthropods actively sought on the ground or among low vegetation. Occasionally joins mixed flocks.

Behavior: Restless; runs and flicks its tail while moving. Moves quickly among bushes and grasslands, as well as on the ground, though it rarely remains visible for long. Observed alone or in pairs. Its song consists of short, explosive trills that rise and fall rapidly (“chííííírrrch”), slower toward the end.

Nesting: The nest is a bulky cup built with dry twigs, located in the lower or middle parts of dense bushes or thickets.

Conservation status: Species with a restricted range in the Andes of southern Bolivia and northwestern Argentina, where it is uncommon and of low density. In Argentina, it is categorized as Vulnerable (VU) due to habitat fragmentation and degradation caused by livestock, the cutting of queñoas and alders, and fires. Internationally, it is listed as Least Concern (LC), though with a decreasing population trend.