Placidium

{{Automatic taxobox

| image = Tree Stipplescale (4752735806).jpg

| image_caption = Placidium arboreum

| taxon = Placidium

| authority = A.Massal. (1855)

| type_species = Placidium michelii

| type_species_authority = A.Massal. (1856)

| subdivision_ranks = Species

| subdivision =

}}

Placidium is a genus of crustose to squamulose to almost foliose lichens. The genus is in the family Verrucariaceae. Most members grow on soil (are terricolous), but some grow on rock (saxicolous). 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.

Members of the genus are commonly called stiplescale lichens or earthscale.Field Guide to California Lichens, Stephen Sharnoff, Yale University Press, 2014, {{ISBN|978-0-300-19500-2}}{{rp|327}}

Taxonomy

The genus was circumscribed in 1855 by Italian lichenologist Abramo Bartolommeo Massalongo.

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, 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.

Species

Placidium arboreum {{small|(Schwein. ex E. Michener) Lendemer (2004)}}
Placidium californicum {{small|Breuss (2000)}} – USA
Placidium lesdainii {{small|Breuss (2002)}}
Placidium nigrum {{small|T.T.Zhang & X.L.Wei (2022)}} – China
Placidium nitidulum {{small|T.T.Zhang & X.L.Wei (2022)}} – China
Placidium podolepis {{small|(Breuss) M.Prieto (2012)}}
Placidium umbrinum {{small|(Breuss) M.Prieto & Breuss (2009)}}
Placidium varium {{small|T.T.Zhang & X.L.Wei (2022)}} – China
Placidium yoshimurae {{small|(H.Harada) Breuss (1996)}}

References

{{Reflist|colwidth=30em|refs=

{{cite journal |last1=Breuss |first1=O. |year=1996 |title=Ein verfeinertes Gliederungskonzept für Catapyrenium (lichenisierte Ascomyceten, Verrucariaceae) |trans-title=A refined outline concept for Catapyrenium (Lichenized Ascomycetes, Verrucariaceae) |journal=Annalen des Naturhistorischen Museums Wien |volume=98 (Suppl.) |pages=35–50 |language=de}}

{{cite journal |last1=Breuss |first1=O. |last2=Bratt |first2=C.C. |year=2000 |title=Catapyrenioid lichens in California |journal=Bulletin of the California Lichen Society |volume=7 |issue=2 |pages=36–42}}

{{cite book |last1=Massalongo |first1=A. |year=1855 |title=Symmicta lichenum novorum vel minus cognitorum |location=Verona |publisher=Typis Antonellianis |language=la |url=https://books.google.com/books?id=zU0-AAAAcAAJ&pg=PA75}}

{{cite journal |last1=Prieto |first1=María |last2=Olariaga |first2=Ibai |title=(2697–2698) Proposals to conserve the names Placidium and P. michelii with conserved types (Verrucariales: lichenized Ascomycota) |journal=Taxon |volume=68 |issue=4 |year=2019 |doi=10.1002/tax.12100 |pages=855–856|s2cid=214192536 |doi-access=free }}

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{{cite journal |last1=Zhang |first1=Tingting |last2=Zhang |first2=Xin |last3=Yang |first3=Qiuxia |last4=Wei |first4=Xinli |year=2022 |title=Hidden species diversity was explored in two genera of catapyrenioid lichens (Verrucariaceae, Ascomycota) from the deserts of China |journal=Journal of Fungi |volume=8 |issue=7 |page=e729 |doi=10.3390/jof8070729 |pmid=35887484 |pmc=9319096 |doi-access=free |url=https://www.researchgate.net/publication/362316368}}

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Category:Verrucariales

Category:Eurotiomycetes genera

Category:Lichen genera

Category:Taxa described in 1855

Category:Taxa named by Abramo Bartolommeo Massalongo