[2][9] A molecular phylogenetic study published in 2013 found that genus Myrmeciza, as then defined, was polyphyletic.

In the resulting rearrangement to create monophyletic genera M. hemimelaena and M. castanea were moved to a newly erected genus Sciaphylax.

[10][11][3] The southern chestnut-tailed antbird's two subspecies are the nominate S. h. hemimelaena (Sclater, PL, 1857) and S. h. pallens (Berlepsch & Hellmayr, 1905).

Males of the nominate subspecies have a mostly gray head and upper mantle with black centers to the feathers.

Their throat and upper breast are black, the center of their belly white to gray, and the rest of their underparts yellowish red-brown.

Single birds, pairs, and family groups usually forage on the ground or within about 1.5 m (5 ft) of it and only rarely higher.

It feeds from vegetation by gleaning, reaching, and making short jumps from a perch and also probes leaf litter on the ground.

The male southern chestnut-tailed antbird sings "a slow but accelerating, descending series of loud, chiming notes, usually ending with a quiet churred phrase: TEE TEE-tee-ti-tidjrdjr.

Females sometimes answer with a "fairly even-paced, descending series of rising whistles" WEE-wee-wee-wee-wee-djr-djr.

The species' calls are "a single, sharp pik, sometimes in [a] short series, and a quiet, descending, thin rattle".