Cranfillia is a genus of ferns belonging to the family Blechnaceae, placed within the subfamily Blechnoideae under the Pteridophyte Phylogeny Group (PPG I) classification of 2016. The genus falls in the order Polypodiales, one of the largest orders of leptosporangiate ferns.
The circumscription of Cranfillia is contested. It is accepted as a distinct genus in the 2016 PPG I framework and in the contemporary World Ferns checklist, which recognises approximately twenty-three species. However, some authorities prefer a broader concept of the genus Blechnum that absorbs Cranfillia and other segregate genera of subfamily Blechnoideae, treating Cranfillia as a synonym of Blechnum in the wide sense.
As a member of Blechnaceae, Cranfillia shares the family's characteristic ladder fern morphology: pinnate or pinnatifid fronds with elongated, strap-like pinnae and a distinctive arrangement of sori running in a continuous line parallel to the costa on either side of the midrib. The family has its greatest diversity in the Southern Hemisphere, particularly in tropical and temperate regions of the Pacific, Australasia, and South America.
Distribution
Cranfillia belongs to the family Blechnaceae, subfamily Blechnoideae, a group distributed predominantly across the Southern Hemisphere, with centres of diversity in the Pacific, Australasia, and South America. No species-level range data are provided in the sources consulted for this genus as a whole.
Taxonomy Notes
Cranfillia was circumscribed under the Pteridophyte Phylogeny Group (PPG I) classification of 2016 as a segregate genus within Blechnaceae subfamily Blechnoideae. The treatment remains disputed: some authorities maintain it as a valid genus with around twenty-three species, while others subsume it within a broadly defined Blechnum that spans the entirety of subfamily Blechnoideae.
