North America, Mexico (Veracruz), Eurasia, Atlantic Islands, Pacific Islands (New Zealand), Australia.
Genus 1, species 3 (2 in the flora).
Climaciaceae are characterized by dendroid branching from a primary rhizomelike subterranean stem, erect capsules, and abundant filiform paraphyllia that are intermediate in morphology between rhizoids and paraphyllia. The longitudinal cauline lamellae on the stipe of Pleuroziopsaceae (monospecific, Pleuroziopsis) (R. R. Ireland 1968) has been used to separate that family, but stem lamellae can be found in Climacium as well (D. H. Norris and M. S. Ignatov 2000). The absence of filiform paraphyllia, strongly decurrent leaves with inflated alar cells, and cernuous, asymmetric capsules of the genus Pleuroziopsis separate the two families.
A. L. Andrews (1954) found rhizoidlike paraphyllia in both Climaciaceae and Hylocomiaceae; H. A. Crum and L. E. Anderson (1981) agreed. The rhizoids in Climacium are red, minutely roughened, with oblique cross walls. The paraphyllia are often mixed with the rhizoids, and are hyaline to tinged with red, smooth, with perpendicular cross walls. According to D. H. Norris and M. S. Ignatov (2000), however, the paraphyllia of Climacium are actually rhizoids, and there is intergradation of morphology. The red-brown exostome in Climacium is incurved when dry in contrast to the erect, yellow-brown segments of the endostome.