
Placopsis is a genus of lichen-forming fungi in the family Trapeliaceae. First introduced as a subgenus in 1861 by William Nylander, the genus now comprises about 50 named species worldwide and shows its greatest diversity in the Southern Hemisphere. These lichens are conspicuous crustose to forms that typically grow on rock or soil, characterised by orbicular or irregularly spreading patches with lobed margins. A defining feature of the genus is the presence of cephalodia, which are nodules containing cyanobacteria that are often centrally placed on the thallus. This distinctive appearance in
GENUS
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Placopsis is a genus of lichen-forming fungi in the family Trapeliaceae. First introduced as a subgenus in 1861 by William Nylander, the genus now comprises about 50 named species worldwide and shows its greatest diversity in the Southern Hemisphere. These lichens are conspicuous crustose to forms that typically grow on rock or soil, characterised by orbicular or irregularly spreading patches with lobed margins. A defining feature of the genus is the presence of cephalodia, which are nodules containing cyanobacteria that are often centrally placed on the thallus. This distinctive appearance inspired the common name 'bull's-eye lichens' for some North American species.
==Taxonomy==
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).