Life habit: lichenized Thallus: umbilicate-rosette shaped, squamulose, crustose-squamulose, subfruticose, gelatinous when wet surface: black, rarely grayish pruinose, smooth, sometimes nodulose or granulose anatomy: ecorticate, homoiomerous, loose network of hyphae surrounding large photobiont cells photobionts: primary one a chroococcoid cyanobacterium, secondary photobiont absent Ascomata: apothecial, laminal on thallus, orbicular, semi-immersed to sessile, margin distinct, with thick thalloid rim ontogeny: hemiangiocarpous, forming pycnoascocarps from ascogonia beneath the pycnidia ascoma anatomy: exciple: hyaline; epithecium: brownish yellow; hypothecium: hyaline, asci: prototunicate, wall thin, nonamyloid, 8-spored ascospores: simple, ellipsoid, broadly ellipsoid or globose; 8-14 µm long, 4-11 µm wide; walls: thin, hyaline Conidiomata: pycnidial, laminal, immersed conidia: ellipsoid or bacilliform, c. 3 x 1 µm Secondary metabolites: none detected Geography: arid, semi-arid to warm temperate regions Substrate: limestone and calcareous rock. Notes: Species of the Phylliscum macrosporum group are similar. Formally, the separation is based on the gelatinous sheath coloration of the photobiont cells which may not be a reliable character. Species of the Phylliscum demangeonii group differ in the lack of paraphyses and possess tapered ascus tips. Paulia is also similar but lacks an exciple and the ascomata arise from a web of generative hyphae.