Authors: Sharon E. Bartholomew-Began
Plants with a prostrate, leafless rhizome with descending, hyaline, leafless stolons and aerial leafy shoots; growth via tetrahedral apical cell; central strands of hydroids present. Leafy shoots 3-ranked, isophyllous or anisophyllous with the reduced row of leaves dorsal; oil bodies present; rhizoids absent. Sexual condition dioicous or monoicous; antheridia and archegonia with a common pattern of development at least in early ontogenetic stages; acrogynous or anacrogynous. Sporophyte protective structure a shoot-calyptra, a true calyptra, or a perigynium; perianth absent. Sporophytes with capsule wall 1-stratose with each cell traversed by a single, annular, longitudinal thickening band.
Genus 1, species 7 (1 genus, 1 species in the flora): temperate, subtropical and tropical regions, nearly worldwide, but disjunct and local.
Haplomitriaceae constitutes the sole family of the Haplomitriales (= Calobryales), with Haplomitrium Nees representing the sole extant genus of the family. The Paleozoic fossil genus, Gessella C. Poulsen from Denmark is also considered a member of the Haplomitriaceae.
Bartholomew-Began, S. E. 1991. A morphogenetic re-evaluation of Haplomitrium Nees (Hepatophyta). Bryophytorum Bibliotheca. 41. Berlin.