The upperparts are dark brown, turning red on the lower back and tail and contrasting sharply with the throat and chest of a bright white.

The White-throated treerunner inhabits the southern tip of the American continent, in Chile and Argentina, from Santiago and Mendoza to Tierra del Fuego.

It seeks out forests with large trees – the old trunks offer suitable nesting sites – whether they are lowland or highland, dense or open.

Its systematic placement has remained unclear within its family, superficial similarities with other Furnariidae gleaning their food from the bark of trees seem to be the result of an evolutionary convergence.

Its range is relatively large and there is no evidence of decline in numbers, so the International Union for Conservation of Nature considers this bird to be of "least concern".

The white-throated treerunner was scientifically described in 1831 under the protonym Dendrocolaptes albogularis by the British explorer Phillip Parker King, who visited Patagonia and Tierra del Fuego among other places.

[2] Burmeister constructs this name from the ancient Greek πυγη (pugē) meaning "rump" and αρριχος (arrhikhos) denoting wicker, to refer to the stiffness of the bird's tail helping it progress along trunks.

It has also been suggested that similarities in plumage and foraging behavior may bring the white-throated treerunner closer to Synallaxis of the genus Aphrastura.

[11] Two molecular phylogenies of the family published in 2009, and then one in 2011, negate such relatedness and clarify the evolutionary history somewhat while implying significant classification changes.

The naming of a subfamily (that of "Pygarrhichinae") or tribe (that of "Pygarrhichini", within the subfamily Furnariinae) is advanced for a clade that would include the white-throated treerunner, the rufous-tailed xenops (Microxenops milleri), species of the genus Ochetorhynchus, and would absorb the band-tailed Eremobius (O. phoenicurus) as well as the crag chilia (O. melanurus), previously placed in the monotypic genera Eremobius and Chilia respectively.

The rest of the lower parts, to the undertail coverts, are made up of white feathers largely bordered with dark brown, giving an irregularly spotted appearance.

[11] It explores trunks quickly and spends more time foraging in smaller branches, looking for prey at the base of leaf petioles.

[17] Outside the breeding season, it may form mixed-species foraging flock with the thorn-tailed rayadito (Aphrastura spinicauda), as well as with the striped woodpecker (Veniliornis lignarius), and sometimes also with the fire-eyed diucon (Xolmis pyrope),[22] Patagonian sierra finch (Phrygilus patagonicus) and the black-chinned siskin (Spinus barbatus).

The breeding season probably spans the southern spring and summer, with eggs laid in November-December and young hatching in December.

[16] This species lives in central and southern Chile and western Argentina, from Santiago and Mendoza to Tierra del Fuego.

[11] The white-throated treerunner appears in some traditional Yagana stories as tatajurj, where it accompanies women and collects epiphytic fungi of the genus Cyttaria (katran in Yagan) from the trunks of Magellanic Beech (N. betuloides), Lenga (N. pumilio), and Ñire (N. antarctica) trees.

[11] The range of the white-throated treerunner is estimated at 470,000 km2 (180,000 sq mi) and its numbers are believed to be stable; thus, the species is considered of "least concern" by the International Union for Conservation of Nature.