North America, Mexico, West Indies, Central America, South America, Asia, Africa.
Genera 9, species ca. 130 (4 genera, 11 species in the flora).
Thuidiaceae are characterized by pinnate branching and strongly differentiated stem and branch leaves. The stems are usually amply clothed with paraphyllia, but in smaller plants, paraphyllia are often sparse. The laminal cells of stem and branch leaves are short and papillose.
Haplocladium (referred to Leskeaceae) might be confused with various Thuidiaceae. However, in Haplocladium, the paraphyllia are not papillose (as they are throughout Thuidiaceae) and branch leaves terminate in a smooth, sharp cell, rather than a truncate, multipapillose cell (except in Rauiella praelonga). Thuidiaceae were distilled by W. R. Buck and H. A. Crum (1990), emphasizing sexuality, placement of laminal cell papillae, papillosity of the cells of the paraphyllia, morphology of axillary hairs, and seta ornamentation. More recently, A. Touw (2001) provided a different generic scheme apparently based primarily on knowledge of the Asian flora.
|1||Stems 1-pinnate||> 2|
|1||Stems (1-)2-3-pinnate||> 3|
|2||Plants large; stems erect-ascending; laminal cells 1-papillose; branch leaf costae not covered with cells apically.||Abietinella|
|2||Plants medium-sized; stems creeping; laminal cells multipapillose; branch leaf costae covered with cells apically.||Rauiella|
|3||Plants small; sexual condition autoicous; paraphyllia unbranched; laminal cells multipapillose on both surfaces.||Cyrto-hypnum|
|3||Plants large; sexual condition dioicous; paraphyllia lanceolate or filiform-branched; laminal cells papillose only abaxially, usually 1-papillose.||Thuidium|