Psilolechia is a genus of four species of crustose lichens. It is the only member of Psilolechiaceae, a family that was created in 2014 to contain this genus.
The genus Psilolechia was established by Abramo Bartolommeo Massalongo in 1860. Formerly classified in the family Pilocarpaceae, molecular phylogenetic analysis showed that Psilolechia represented a distinct lineage that deserved placement at the familial level, the Psilolechiaceae, which was formally circumscribed in 2014. This arrangement was accepted in later large-scale updates of fungal classification. Psilolechiaceae is in the order Lecanorales, in the suborder Sphaerophorineae, which also includes the families Pilocarpaceae, Psoraceae, and Ramalinaceae.
Psilolechiaceae is a monogeneric family of crustose lichens with effuse, ecorticate (lacking a cortex), leprose thalli formed by goniocysts (aggregations of photobiont cells surrounded by short-celled hyphae) containing Trebouxia or stichococcoid algae. The apothecia lack a distinct margin, and the asci are 8-spored and have a cylindrical to clavate shape. They feature a central, elongated tube-like structure, and a non-amyloid ascus wall surrounded by a thin outer layer. Both the tube-like structure and the thin outer layer stain dark blue in K/I. Ascospores are oblong-ovoid to tear-shaped, simple (rarely 1-septate in P. leprosa), and hyaline.
Psilolechia contains four species:
Psilolechia species grow in locations that are humid and shaded. P. leprosa tends to grow on mineral-enriched rocks and siliceous rocks, and is often recorded around old mines.