Andrewsianthus ferrugineus was described by Riclef Grolle in 1966 based on a type specimen collected in 1962 by Austrian botanist Josef Poelt from a Rhododendron forest near Ringmo, Nepal.

[4] Endemic to the temperate eastern Himalayas,[5] Tritomaria ferruginea is known from Bhutan, India (Sikkim), and Nepal.

[1][6][7] In western Bhutan it has been found growing in damp coniferous forests dominated Abies and Juniperus at 3,440 m (11,290 ft) above sea level,[5] while in India it has been found growing in both moorland and on rocky river banks at altitudes of 4,070–4,075 m (13,353–13,369 ft) above sea level.

[7] Tritomaria ferruginea is green to rusty in colour with overlapping, three-lobed leaves that measure 1–2 mm (0.039–0.079 in) wide.

[3][5] Tritomaria ferruginea is listed as endangered by the International Union for the Conservation of Nature under criteria B1 and B2cd, based on its small area of occupancy and risk of habitat destruction due to deforestation.