From the Greek rhaco (lacerate) and pilos (hair), in reference to the lacerate, pilose calyptra.

Dwarf male plants on female plant leaves (phyllodioicous); normal-sized male plants rare. Lateral leaves oblong-ovate, obtuse to acute, spreading laterally when moist, curved upwards and longitudinally convolute when dry, 1–2 mm long (excluding arista), 0.3–0.9 mm wide; margin plane or slightly undulate near leaf base, unbordered, serrulate to serrate towards the apex, rarely almost entire; costa excurrent as a smooth arista of variable length; laminal cells irregular, (sub)isodiametric, short-rhomboidal to hexagonal, often in oblique rows (then shape more regular), (8–) 10–22 (–30) µm long, thin- to firm-walled, both sides smooth or unimammillose; cells at basal margins and towards base short-rectangular; dorsal leaf shape and size very variable, symmetrical, obliquely forward-pointing, narrowly triangular to ovate.

Perichaetial leaves sheathing, broadly ovate, c. 1.5–1.8 mm long; costa long-excurrent; laminal cells rectangular, 60–80 µm long; paraphyses hair-like, often projecting beyond bracts. Setae 7–30 mm long, yellowish or reddish, twisted to the right in upper part and to the left in lower part. Capsules inclined or horizontal, rarely ±erect, (2.0–) 2.5–3.5 (–4.5) mm long (excluding lid), curved or nearly straight, a small bend just below the oblique orifice; neck short, strumose or not, deeply grooved, with stomata; operculum 0.7–1.8 mm long, rostrate from a convex-conical base; rostrum erect or oblique, (0.5–) 0.7–0.9 (–1.0) mm long, straight or hooked. Exostome brownish; teeth narrowly lanceolate, transversely striate, with a zig-zag median line on outer face, barred on inner face, papillose above; endostome segments well developed; basal membrane c. half the exostome height, smooth; segments broad, keeled, broadly perforated, as long as exostome or slightly shorter; cilia 2 or 3, well developed, nodose or appendiculate.

This predominantly tropical and subtropical genus of about 15 species occurs in both hemispheres and in temperate regions of the Southern Hemisphere; species diversity is greatest in the Malesian region. Two non-endemic species and an additional variety are known from Australia.

Racopilum P.Beauv., Prodr. Aethéogam. 36 (1805). Lectotype: R. mnioides P.Beauv. [= R. tomentosum (Hedw.) Brid.]

Orthographic variant: Rhacopilum.

The genus is often spelled as “Rhacopilum”, which is linguistically correct, but the original spelling by Palisot de Beauvois is followed here.

Koponen, T. & Norris, D.H. (1986), Bryophyte flora of the Huon Peninsula, Papua New Guinea. XVII. Grimmiaceae, Racopilaceae and Hedwigiaceae (Musci), Acta Bot. Fenn. 133: 81–106.

Scott, G.A.M. & Stone, I.G. (1976), The Mosses of Southern Australia. Academic Press, London.

Zanten, B.O. van (1970), De afgrenzing van het geslacht Powellia tegen Racopilum (Musci), Jaarb. Kon. Ned. Bot. Ver. 1969: 54–57.

Zanten, B.O. van & Hofman, A. (1995), On the origin and taxonomic status of Racopilum chilense (Musci, Racopilaceae) by using electrophoretic analysis, Fragm. Florist. Geobot. 40: 405–416.

B.O.van Zanten (2012), Australian Mosses Online 56. Racopilaceae. Australian Biological Resources Study, Canberra. Version 28 June 2012.

First published as:  B.O.van Zanten (2006), Racopilaceae, Fl. Australia 51: 371–376. Australian Biological Resources Study, Canberra & CSIRO Publishing, Melbourne.