North America, South America, Eurasia, Africa, Atlantic Islands (Iceland).
Genera 3, species 19 (3 genera, 15 species in the flora).
Fontinalaceae are distinguished by the aquatic or semi-aquatic habitat, long axillary hairs, absence of stem central strand, lack of stomata, odd exostome morphology, and unusual trellised endostome. The exostome teeth in Fontinalaceae are linear, with outer and inner plates equally high. The endostome is firm rather than membranous because of relatively heavy secondary thickening.
All three genera and most species of Fontinalaceae are found in North America. Brachelyma, which is semi-aquatic with a strong single costa and occasional stem paraphyllia, appears to be the basal genus in the family. Fontinalis, on the other hand, is generally aquatic with a nearly absent costa, well-developed, often bulging alar cells, and immersed to short-emergent capsules, and it appears to be the most derived genus in Fontinalaceae.
|1||Leaves ecostate or nearly so.||Fontinalis|
|1||Leaves with costae present||> 2|
|2||Leaves oblong-lanceolate to lanceolate; calyptrae covering operculum only; setae0.7-1.5 mm; capsules immersed.||Brachelyma|
|2||Leaves lanceolate to linear-lanceolate; calyptrae covering capsule; setae 3-15(-20) mm; capsules immersed, emergent, or exserted.||Dichelyma|