{{Short description|Genus of lichen}} {{Automatic taxobox | image = | image_caption = | taxon = Psoromidium | authority = Stirt. (1877) | type_species = ''Psoromidium wellingtonii'' | type_species_authority = Stirt. (1877) | subdivision_ranks = Species | subdivision = ''P. aleuroides''<br /> ''P. versicolor''<br /> ''P. wellingtonii'' | synonyms_ref = <ref name="Species Fungorum synonymy"/> | synonyms = *''Degeliella'' {{small|P.M.Jørg. (2004)}} *''Psoromaria'' {{small|Nyl. ex Hue (1891)}} }}

'''''Psoromidium''''' is a genus of cyanolichens in the family Pannariaceae.<ref name="Wijayawardene et al. 2020"/> It has three species.

==Taxonomy==

The genus was circumscribed by Scottish naturalist James Stirton in 1877,<ref name="Stirton 1877"/> based on the type species ''P.&nbsp;wellingtonii'' (later synonymised with ''P.&nbsp;aleuroides'') collected by John Buchanan near Wellington, New Zealand. The genus belongs to the family Pannariaceaein the order Lecanorales. ''Psoromidium'' is closely related to certain elements within the heterogeneous genus ''Psoroma'', but is distinguished by the absence of a {{lichengloss|photobiont}} in the apothecial margin. Like ''Psoroma'', it has a green algal photobiont as the main photobiont present in a layer below the upper {{lichengloss|cortex}} of the {{lichengloss|squamules}}, with ''Nostoc'' occurring in scattered, well-defined cephalodia.<ref name="Galloway & James 1985"/>

The taxonomic history of the genus involves several nomenclatural changes. In 1875, Stirton described ''Lecidea aleuroides'', which would later become the type species of ''Psoromidium''. In 1888, William Nylander described ''Psoroma descendens'' (later determined to be identical to ''L.&nbsp;aleuroides'') and suggested a possible new genus ''Psoromaria'' for it. In 1894, Müller Argoviensis transferred both ''P.&nbsp;wellingtonii'' and ''L.&nbsp;aleuroides'' to the genus ''Phyllopsora''. The genus ''Psoromaria'' Nyl. was later determined to be a synonym of ''Psoromidium''.<ref name="Galloway & James 1985"/>

The generic name combines elements suggesting its relationship to ''Psoroma'' while indicating its distinct status. The genus is considered a relict of the lichen flora that existed on the Pacific front of Gondwanaland in Cretaceous and Tertiary times, supported by its disjunct distribution pattern and restriction to cool-temperate and subalpine habitats.<ref name="Galloway & James 1985"/>

==Species== *''Psoromidium aleuroides'' {{small|(Stirt.) D.J.Galloway (1983)}} *''Psoromidium versicolor'' {{small|(Müll. Arg.) D.J.Galloway (1983)}} *''Psoromidium wellingtonii'' {{small|Stirt. (1877)}}

==References== {{Reflist|refs=

<ref name="Galloway & James 1985">{{cite journal |last1=Galloway |first1=D.J. |last2=James |first2=P.W. |title=The lichen genus ''Psoromidium'' Stirton |journal=The Lichenologist |volume=17 |issue=2 |year=1985 |doi=10.1017/S0024282985000226 |pages=173–188}}</ref>

<ref name="Species Fungorum synonymy">{{cite web |title=Synonymy: ''Psoromidium'' Stirt., Proc. Roy. phil. Soc. Glasgow 10: 304 (1877) |url=https://www.speciesfungorum.org/Names/SynSpecies.asp?RecordID=4525 |publisher=Species Fungorum |access-date=2 June 2021}}</ref>

<ref name="Stirton 1877">{{cite journal |last1=Stirton |first1=J. |year=1877 |title=On new genera and species of lichens from New Zealand |journal=Proceedings of the Philosophical Society of Glasgow |volume=10 |pages=285–306}}</ref>

<ref name="Wijayawardene et al. 2020">{{cite journal |display-authors=6 |last1=Wijayawardene |first1=Nalin |last2=Hyde |first2=Kevin |first3=Laith Khalil Tawfeeq |last3=Al-Ani |last4=Somayeh |first4=Dolatabadi |last5=Stadler |first5=Marc |last6=Haelewaters |first6=Danny |last7=Tsurykau |first7=Andrei |last8=Mesic |first8=Armin |last9=Navathe |first9=Sudhir |last10=Papp |first10=Viktor |last11=Oliveira Fiuza |first11=Patrícia |last12=Vázquez |first12=Víctor |last13=Gautam |first13=Ajay |last14=Becerra |first14=Alejandra G. |last15=Ekanayaka |first15=Anusha |last16=K. C. |first16=Rajeshkumar |last17=Bezerra |first17=Jadson |last18=Matočec |first18=Neven |last19=Maharachchikumbura |first19=Sajeewa |last20=Suetrong |first20=Satinee |year=2020 |title=Outline of Fungi and fungus-like taxa |journal=Mycosphere |volume=11 |pages=1060–1456 |doi=10.5943/mycosphere/11/1/8 |doi-access=free|hdl=10481/61998 |hdl-access=free }}</ref>

}}

{{Taxonbar |from1=Q7256124 |from2=Q10467690 |from3=Q22103718}}

Category:Pannariaceae Category:Lichen genera Category:Peltigerales genera Category:Taxa named by James Stirton Category:Taxa described in 1877