Placidium is a genus of crustose to squamulose to almost foliose lichens. The genus is in the family Verrucariaceae.[1] Most members grow on soil (are terricolous), but some grow on rock (saxicolous).[2] The fruiting bodies are perithecia, flask-like structures immersed in the lichen body (thallus) with only the top opening visible, dotting the thallus. Lichen spot tests are all negative. Members of the genus lack rhizines, but otherwise resemble members of the genus Clavascidium.[2]
| Placidium | |
|---|---|
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| Placidium arboreum | |
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Fungi |
| Division: | Ascomycota |
| Class: | Eurotiomycetes |
| Order: | Verrucariales |
| Family: | Verrucariaceae |
| Genus: | Placidium A.Massal. (1855) |
| Type species | |
| Placidium michelii A.Massal. (1856)
| |
Members of the genus are commonly called stiplescale lichens or earthscale.[2]: 327
Taxonomy
editThe genus was circumscribed in 1855 by Italian lichenologist Abramo Bartolommeo Massalongo.[3]
María Prieto and Ibai Olariaga suggest that Placidium is a superfluous illegitimate name according to strict application of nomenclatural rules. This is because when Massalongo circumscribed the genus in 1855, he included the original type species of genus Endocarpon, E. pusillum. When Othmar Breuss resurrected the genus for use in 1996,[4] he assigned P. michelii as its type, even though Massalongo did not include P. michelii in Placidium in his original 1855 circumscription, but rather in a later treatment of the genus. In 2019, Prieto and Olariaga submitted a proposal to conserve the name Placidium with Placidium michelii as its conserved type species.[5]
Species
edit- Placidium arboreum (Schwein. ex E. Michener) Lendemer (2004)
- Placidium californicum Breuss (2000)[6] – USA
- Placidium lesdainii Breuss (2002)
- Placidium nigrum T.T.Zhang & X.L.Wei (2022)[7] – China
- Placidium nitidulum T.T.Zhang & X.L.Wei (2022)[7] – China
- Placidium podolepis (Breuss) M.Prieto (2012)
- Placidium umbrinum (Breuss) M.Prieto & Breuss (2009)
- Placidium varium T.T.Zhang & X.L.Wei (2022)[7] – China
- Placidium yoshimurae (H.Harada) Breuss (1996)
References
edit- ^ Wijayawardene, N.N.; Hyde, K.D.; Dai, D.Q.; Sánchez-García, M.; Goto, B.T.; Saxena, R.K.; et al. (2022). "Outline of Fungi and fungus-like taxa – 2021". Mycosphere. 13 (1): 53–453. doi:10.5943/mycosphere/13/1/2. hdl:10481/76378. S2CID 249054641.
- ^ a b c Field Guide to California Lichens, Stephen Sharnoff, Yale University Press, 2014, ISBN 978-0-300-19500-2
- ^ Massalongo, A. (1855). Symmicta lichenum novorum vel minus cognitorum (in Latin). Verona: Typis Antonellianis.
- ^ Breuss, O. (1996). "Ein verfeinertes Gliederungskonzept für Catapyrenium (lichenisierte Ascomyceten, Verrucariaceae)" [A refined outline concept for Catapyrenium (Lichenized Ascomycetes, Verrucariaceae)]. Annalen des Naturhistorischen Museums Wien (in German). 98 (Suppl.): 35–50.
- ^ Prieto, María; Olariaga, Ibai (2019). "(2697–2698) Proposals to conserve the names Placidium and P. michelii with conserved types (Verrucariales: lichenized Ascomycota)". Taxon. 68 (4): 855–856. doi:10.1002/tax.12100. S2CID 214192536.
- ^ Breuss, O.; Bratt, C.C. (2000). "Catapyrenioid lichens in California". Bulletin of the California Lichen Society. 7 (2): 36–42.
- ^ a b c Zhang, Tingting; Zhang, Xin; Yang, Qiuxia; Wei, Xinli (2022). "Hidden species diversity was explored in two genera of catapyrenioid lichens (Verrucariaceae, Ascomycota) from the deserts of China". Journal of Fungi. 8 (7): e729. doi:10.3390/jof8070729. PMC 9319096. PMID 35887484.