Abstract
Taxonomic re-examination of the Gammiella ceylonensis complex is done in the light of Sematophyllaceae-Pylaisiadelphaceae circumscription based on morphological and molecular (cpDNAs: rbcL, rps4, and trnL-F) phylogenetic analyses. Three new genera are proposed to accommodate the newly recognized clades. The first is Clastobryellina that is raised from a section level under Clastobryella to include four species—two are existing species with new combinations proposed here (C. ceylonensis, C. merrillii), and two are new species described here (C. lutea, C. orientalis). Clastobryum sect. Clastobryellina is lectotypified by Clastobryum merrillii. The second is Bonnosukea, a new genus described to accommodate only B. serrulata, which is formerly included in Clastobryum, but is shown to be sister to the genus. The last is Microgammiella, a new monotypic genus that is sister to Aptychella, with a newly described species M. flagelliformis. Three species of Clastobryellina, except for a northern Thailand endemic C. lutea, show wide and disjunct distribution in East Asia.