Lathagrium cristatum

Lathagrium cristatum, the fingered jelly lichen or fingered rock-jelly, is a species of cyanolichen in the family Collemataceae. Originally described by Carl Linnaeus in 1753, the species has a complex taxonomic history involving numerous synonyms and nomenclatural challenges that were only resolved through formal conservation of the name in 1996. The lichen forms distinctive dark olive-green to blackish rosettes on calcareous rocks, with thin, narrow lobes that have characteristically wavy, toothed margins. It has a widespread distribution across the Northern Hemisphere, occurring in diverse climates from arid lowland deserts to arctic and alpine zones. Like other members of its family, it contains cyanobacteria as its photosynthetic partner, enabling it to fix atmospheric nitrogen. The species typically grows in undisturbed natural habitats on hard limestone or dolomite, often in exposed sites moistened by rain runoff. ...read more on Wikipedia.