Aulacomniaceae
Dioicous or autoicous (not in Victoria). Asexual reproduction by leaf-like gemmae clustered on a terminal pseudopodium. Mats, tufts or cushions on soil, logs or rocks. Stems simple or sparingly branched, sometimes by innovations, rarely with an unbranched basal stipe and a branched apical frond section (not in Victoria), tomentose throughout or at base; central strand present. Leaves complanate or arranged around stem and facing all directions, erect to wide-spreading when moist, crisped, twisted or scarcely altered when dry, symmetric or asymmetric; apex rounded, obtuse, acute or acuminate; costa subpercurrent to excurrent as a mucro, dividing leaf unevenly or dividing leaf evenly; margin with single or paired teeth or serrulate toward apex, rarely entire (not in Victoria), often bi- or multi-stratose, with or without a distinct border of elongated cells; laminal cells subquadrate, short-rectangular, elliptic, rounded-hexagonal or irregular, often becoming more elongate toward base, smooth or papillose; alar cells not differentiated. Acrocarpous or pleurocarpous. Capsules erect to horizontal, straight to curved, exserted, operculate, smooth or sulcate. Calyptra cucullate, glabrous. Operculum rostrate. Peristome double or rarely single (not in Victoria); exostome of 16 entire teeth or absent (not in Victoria); endostome of 16 well-developed segments, with a basal membrane; cilia present.
Four genera and twelve species distributed throughout most of the world, but absent from Antarctica; three genera and species in Victoria.
Hymenodontopsis and Mesochaete, which have traditionally been placed in the Rhizogoniaceae, were shown by phylogenetic analyses of combined chloroplast and mitochondrial DNA sequences to be closer related to Aulacomnium than they are to Rhizogonium and have been transferred to the Aulacomniaceae (Bell et al. 2007). Additionally, some of the species previously recognised in Pyrrhobryum were shown in these analyses to be better placed in Hymenodontopsis and so are also included in the Aulacomniaceae (see Hymenodontopsis mnioides). This circumscription of Aulacomniaceae produces a morphologically heterogeneous family that is ill-defined morphologically. However, some morphological support for grouping these genera together is offred by similarities between some of the species in these genera to each other. Mesochaete and Aulacomnium heterostichum both have sulcate capsules, undulate, oblong-ovate and asymmetric leaves with smooth cells and coarsely toothed margins and the apical leaves are often caducous (O’Brien 2007), while Mesochaete and Hymenodontopsis are connected by being pleurocarpous and have smooth laminal cells and serrate margins more than one cell thick.
SpinningBell, N.E.; Quandt, D.; O’Brien, T.J.; Newton, A.E. (2007). Taxonomy and phylogeny in the earliest diverging pleurocarps: square holes and bifurcating pegs. The Bryologist 110: 533–560.
O’Brien, T.J. (2007). The Phylogenetic Distribution of Pleurocarpous Mosses: Evidence from cpDNA Sequences, in Newton, A.E. & Tangney, R.S. (eds.), Pleurocarpous Mosses Systematics and Evolution, pp. 19–40. Taylor & Francis Group, Boca Raton.
