Radulaceae

Radulaceae is a family of liverworts, and the only family in the order Radulales. The family comprises three genera: Radula, Cladoradula, and Dactyloradula, recognised as distinct following a 2022 taxonomic revision. Distinguishing features include bilobed leaves arranged in two rows, with the smaller lobe folded under the larger one, and rhizoids (root-like structures) uniquely emerging from leaves rather than stems. The family lacks underleaves, which are common in other liverwort families. Fossil evidence from Burmese amber indicates the family had diversified by the Cretaceous period, approximately 98 million years ago, with molecular studies suggesting its divergence from related groups occurred during the Permian period.

While Radula occurs worldwide from sea level to 4,000 metres elevation, Cladoradula shows a disjunct distribution across tropical and temperate regions, typically growing on tree bark and shaded rocks in submontane and lower montane forests between 400 and 2,100 metres. Dactyloradula is endemic to Japan and uniquely features finger-like appendages at the base of each leaf lobe. The family includes both rare and widespread species, with several Macaronesian endemics facing significant conservation challenges. Among these, Radula visianica is assessed as Critically Endangered, with fewer than 50 individuals remaining in Austria, while others are threatened by climate change, habitat modification, and increased fire frequency. Recent molecular phylogenetics analysis has refined understanding of relationships within the group, with the genus Porella identified as its closest relative.