Pleurophascaceae Broth.

The Pleurophascaceae are a monotypic family, with features of its single Australasian genus described below.

The recognition of this monotypic family is justified by a large number of unique or near-unique morphological features. These include: large, inoperculate capsules, a spore sac attached to the exothecial wall by anastomosing cellular filaments, subterranean and creeping primary stems with scale-like leaves, broadly elliptic to nearly round leaves with very thick-walled and porose cells and no costa. The position of the sex organs can be either terminal or on short lateral branches; secondary (erect) stems are mostly encased in a dense weft of pale, smooth rhizoids.

Brotherus (1924, pp. 155, 219) placed the Pleurophascaceae in its own suborder in the Dicranales, emphasising its ecostate leaves, the lateral placement of its sex organs, and large, spherical, and cleistocarpous capsules with immersed stomata. Vitt (1984, p. 754) placed Pleurophascum in a monotypic family Pleurophascaceae Broth., adjacent to the Dicnemonaceae. Both the classification used for the Flora of Australia (McCarthy 2006) and the classification proposed by Goffinet et al. (2009) placed the Pleurophascaceae in the Pottiales, with the large and cosmopolitan family Pottiaceae and the monogeneric families Mitteniaceae and Serpotortellaceae. The Pleurophascaceae are highly distinct morphologically in an Australasian context, and are deserving of familial recognition.