Sciaphylax

Sciaphylax is a genus of passerine birds in the family Thamnophilidae.

The genus contains two species:

These species were formerly included in the genus Myrmeciza. A molecular phylogenetic study published in 2013 found that Myrmeciza was polyphyletic. In the resulting rearrangement to create monophyletic genera, the two chestnut-tailed antbirds was moved to a newly erected genus Sciaphylax. The type species is the southern chestnut-tailed antbird. The name of the new genus combines the Ancient Greek words skia "shadow" and phylax "a watcher".

Sciaphylax occur in non-overlapping regions. Species in this genus are known for their reddish to chestnut plumage, short tails, and sexually dimorphic features. They typically forage near the ground, often alone or in pairs, capturing insects through perch-gleaning and short leaps.

Their vocalisations include loudsongs and brief call notes, which differ between species and show geographic variation, particularly in S. hemimelaena. The nests are open cups, usually supported by palm leaves or forest debris, and only females have been observed to incubate the eggs. Molecular phylogenetic studies have identified Sciaphylax as a sister genus to Cercomacroides, and both belong to a clade separate from traditional Cercomacra. While S. hemimelaena is relatively common and occurs in several protected or undisturbed areas, S. castanea has a more restricted distribution and may be vulnerable due to habitat degradation and limited scientific attention.

Based on mitochondrial and nuclear DNA sequences, molecular phylogenetic investigations have identified Sciaphylax as the sister genus to Cercomacroides, which is a recently established genus including numerous species previously classified under Cercomacra. These two genera are part of the same clade as Drymophila and Hypocnemis. However, they are more distantly related to Cercomacra.

The genus Sciaphylax is composed of small-bodied birds with relatively short, thin tails and body proportions. These antbirds typically weigh between 14.5 and 17 g (0.5 and 0.6 oz) and have a body length ranging from 11 to 12 cm (4.3 to 4.7 in). They are known for their distinct reddish to chestnut colouration. Sciaphylax antbirds generally exhibit a dark reddish to yellowish chestnut colour on the upperparts. Male Sciaphylax tend to have brighter plumage with black and white markings, while females show softer, more muted tones. Distinctive features include black wing coverts with noticeable pale tips, a pale scapular patch with black subterminal dots, and differing degrees of black on the neck and chest in males. Their prominent wing covert patterns and reddish-brown colouration extending toward the end of the body, including the tail. The tail is typically concolorous with the central underparts, particularly in males, and may appear paler in contrast with the darker upperparts.

Members of the genus Sciaphylax have been found in eastern Peru, the southwest of Brazil, the south of Colombia, the east of Ecuador, and the north of Bolivia. The distribution of the two species do not overlap. The southern chestnut-tailed antbird (Sciaphylax hemimelaena) is found in the southwestern to central Amazonian Brazil (from the east of Madeira River to southwestern Pará, south to Rondônia, south to Acre, and western and northern Mato Grosso), as well as north Bolivia (east and west Santa Cruz, Pando, La Paz, Western Beni, and Cochabamba). The northern chestnut-tailed antbird (Sciaphylax castanea) is distributed in the north of Peru (Loreto, San Martín), east of Ecuador (Zamora-Chinchipe, Napo, and Pastaza), as well as extreme southern Colombia (Putumayo).