2001 Volume 90 Pages 167-209
Based on multi-character analyses of selected species the Thuidiaceae are redefined, and a realignment is presented of the species previously accommodated in Thuidium s. amplo (Thuidium Schimp. sensu Brotherus 1925, Thuidiopsis (Broth.) M.Fleisch., and Pelekium Mitt.), based on a similar analysis of numerous well-known species and additional information from many remaining ones. The family is characterized by a large combination of character states shared by all genera: regularly pinnate ramification; scattered paraphyllia; mostly cordate or triangular, acute to long-acuminate, plicate stem leaves with recurved margins often bearing paraphylloid appendages below; single, strong, often almost percurrent and almost always distally rough costae bearing paraphylloid or pseudoparaphylloid appendages near insertion; narrow, both mammillose and papillose median leaf cells (mostly ornamented at both leaf faces); weakly differentiated basal and apical leaf cells; undifferentiated or poorly defined alar cell groups consisting of cells shorter than the adjacent leaf cells, if differentiated; leaves of ultimate branches markedly different from stem leaves in bipinnate or tripinnate species; tubular perichaetia with inner leaves ending in a straight, flexuose, or twisted acumen; ovoid to cylindrical, inclined capsules (except in many specialized epiphytes); rarely distinctly collenchymatous exothecial cells; superficial stomata; a hypnoid peristome; and almost always cucullate, naked, smooth calyptrae. Included are Abietinella, Actinothuidium, Boulaya, Bryochenea, Bryonoguchia, Echinophyllum, Haplocladium, Helodium, Hylocomiopsis, Orthothuidium, Pelekium, Rauiella, Thuidiopsis, Thuidium, Aequatoriella gen. nov. (type: Thuidium bifarium Bosch & Sande Lac.), and Indothuidium gen. nov. (type: Thuidium kiasense R.S.Williams). Pelekium sensu Brotherus is judged polyphyletic. Pelekium s.str., consisting of the type species (P. velatum) is lumped with Cyrto-hypnum (Thuidium subg. Thuidiella), for which Pelekium is the older name. Inouethuidium is excluded. The genera are briefly discussed. In Appendix I the 2 new genera, Thuidium pseudoglaucinum sp. nov., Bryochenea vestitissima (Besch.) Touw, comb. nov., and 28 new combinations in Pelekium are validated, and heterotypic synonyms are proposed relating to American, European, and Madeiran species. The American Pelekium muricatulum (Hampe) Touw (earlier lumped with Pelekium minutulum) is reinstated.