[citation needed] The thorn-tailed rayadito was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae.

[3] The naturalist Joseph Banks had provided Latham with a water-colour drawing of the bird by Georg Forster who had accompanied James Cook on his second voyage to the Pacific Ocean.

[7] The thorn-tailed rayadito is approximately 14 centimetres (5.5 in) in length including the tail, and an average adult weighs around 11 grams (0.39 oz), with males being around 10 percent heavier than females.

[8] The most distinctive feature of a bird frequently compared to a tit[9] is the long "thorn"-tail with twelve spiny rectrices, which gradually develops in juveniles as they mature.

Typical voices of the thorn-tailed rayadito include:[10] It is found in noisy flocks from central Chile and adjacent Argentina, south to Tierra del Fuego.

[13] Like most furnariids, the thorn-tailed rayadito is exclusively insectivorous, and like the tits of the northern hemisphere it searches bark and moss surfaces for small insects.

The latter is distinctly longer than in north temperate species at the same distance from the equator, but not nearly so long as in many tropical, Australian and southern African passerines[16][22] where young are not independent for over sixty days.