The genus Prionolejeunea belongs in the Lejeuneaceae, the most advanced and highly specialized family among the leafy Hepaticae (Mizutani, 1961). This vast family is also the most difficult hepatic group in terms of generic delimitation (Gradstein, 1982). Since the revolutionary generic concept of the Lejeuneaceae was established by Spruce (1884), nearly 100 currently accepted genera with about 2000 species have been described. The difficult taxonomy of the family can be explained by the remarkable morphological diversity of the genera. This variability led to numerous descriptions of new species by many authors, especially by Stephani (1898-1924). Schuster (1963) attempted to arrange the genera into homogeneous or interrelated groups and emphasized the need for monographic work on the genera. Advances in the classification of the family were provided by new findings on the sporophyte structure and its taxonomical importance by Mizutani (1961). These findings led to a subdivision of Lejeuneaceae into two subfamilies, Ptychanthoideae and Lejeuneoideae, largely based on features of the sporophyte (Mizutani, 1985a Gradstein, 1994a).