Phylliscaceae
The Phylliscaceae are a family of lichen-forming ascomycete fungi placed in the order Lichinales. Members are mostly small cyanolichens that form thin crusts tightly attached to rock, or minute, scale-like rosettes. These lichens are typically found growing on rocks in sunny, dry locations where they form small, crusty patches or tiny leaf-like scales. They partner with cyanobacteria instead of green algae, which helps them survive in harsh, drought-prone environments where other lichens cannot establish.
Taxonomy
The family was introduced by Elias Magnus Fries in 1861 under the name Phylliscei. Fries defined the group by a small, somewhat leaf-like thallus that is attached at a central point and by fruiting bodies that are embedded in the thallus. In his treatment he placed Phylliscum as a representative genus. Fries' of Phylliscum emphasised minute, mostly single-bladed thalli with the photosynthetic granules wrapped in a gelatinous layer; the apothecia are immersed and the spore sacs contain many simple, colourless, ellipsoid spores. He cited Phylliscum endocarpoides as a typical species and noted it on calcareous and siliceous rock faces in northern Scandinavia, probably widespread across Arctic regions but easily overlooked because of its very small size.The family has long been placed within the order Lichinales. A class-wide multilocus study published in 2024 re-examined relationships across Lichinomycetes and issued an emended circumscription of the family. That analysis, which sampled 190 specimens representing 126 species, showed that several traditional family and genus boundaries conflicted with DNA-based relationships and proposed a revised framework. Within this framework, genera such as Peltula, Phylliscum, Phyllisciella, Peccania, and allied small saxicolous cyanolichens are treated in Phylliscaceae.