{{Short description|Genus of lichen}} {{Use dmy dates|date=July 2025}} {{Use Oxford spelling|date=July 2025}} {{Automatic taxobox | image = Rimularia gibbosa 1624799768.jpg | image_caption = ''Rimularia gibbosa'' | taxon = Rimularia | authority = Nyl. (1868) | type_species = ''Rimularia limborina'' | type_species_authority = Nyl. (1868) | subdivision_ranks = Species | subdivisions = }}
'''''Rimularia''''' is a genus of lichen-forming fungi in the family Trapeliaceae.<ref name="CoL_CDZD4"/> Established by the Finnish lichenologist William Nylander in 1868 from specimens collected on granitic rocks in France, the genus comprises 14 accepted species as of 2025. These rock-dwelling lichens form thin, crust-like growths that range from reddish-brown to dark olive-brown in colour and produce small black fruiting bodies with distinctive branched internal structures.
==Taxonomy==
''Rimularia'' was circumscribed by the Finnish lichenologist William Nylander in 1868. In his original description of the genus, Nylander characterized ''Rimularia'' as having a thin, ash-grey thallus that is either smooth or slightly roughened, with black fruiting bodies (apothecia) that are either flush with the surface or slightly raised. He noted that the spores are colourless, {{lichengloss|simple}} (undivided), and elliptical in shape, measuring about 0.018–0.025 millimetres in length. Nylander distinguished this new genus from related groups by several key features: unlike {{lichengloss|pyrenocarpous}} lichens, ''Rimularia'' lacks the small pore-like openings (ostioles) typical of that group, and unlike ''Mycoporum'' and ''Acarospora'', it does not have the disc-shaped or flask-shaped fruiting body structure characteristic of those genera.<ref name="Nylander 1868"/>
Nylander established ''Rimularia'' based on collections from granitic rocks in Gaul and Haute-Vienne, France, where it was found growing alongside ''Lecanora cinereae'' var. ''gibbosae''. He noted that while the genus might appear similar to certain ''Pertusaria'' species at first glance, it could be reliably distinguished by the continuous nature of its thallus and the distinctive structure of its fruiting bodies, which lack the characteristic features found in the related genus ''Pertusaria''.<ref name="Nylander 1868"/>
==Description==
''Rimularia'' forms a thin, crust-like thallus that sits directly on the substrate rather than rising above it. The surface is continuous but may crack into small, irregular plates ({{lichengloss|areoles}}) as it ages. Depending on exposure and microhabitat the thallus ranges in colour from reddish or yellowish brown to dark olive-brown, and occasionally it appears chalk-white. A microscopic {{lichengloss|epinecral layer}}—an outer film of dead fungal cells—covers the living {{lichengloss|algal layer}}; there is no differentiated {{lichengloss|cortex}}. The photosynthetic partner is a minute, spherical green alga (a {{lichengloss|chlorococcoid}} photobiont).<ref name="Orange et al. 2021"/>
Reproductive bodies are small, black apothecia that begin partly embedded and become stalkless (sessile) with maturity. Their discs can be flat, centrally raised like a tiny shield-boss (umbonate) or divided into winding ridges ({{lichengloss|gyrose}}). Unlike many lichens, ''Rimularia'' lacks a {{lichengloss|thalline margin}}; the visible rim is the {{lichengloss|true exciple}}, a persistent ring of contorted, often gyrose, black tissue. Inside, the upper hymenial layer reacts blue with iodine (I+), a signal of amyloid structures in the ascus apex. The paraphyses—slender sterile filaments threading the hymenium—are richly branched and interlinked (anastomosed) but their dark-tipped ends do not swell. Beneath, a dark-brown to black {{lichengloss|hypothecium}} merges with the exciple.<ref name="Orange et al. 2021"/>
Each cylinder-to-club-shaped ascus (''Rimularia''-type) holds eight ascospores. These are initially colourless, ellipsoidal to almost spherical and single-celled, but turn brown just before they are released; they lack the gelatinous outer coat ({{lichengloss|perispore}}) seen in some other genera. Immersed pycnidia produce rod-shaped, transparent conidia that enable asexual propagation. Chemical analyses reveal a suite of secondary metabolites—norstictic, stictic and gyrophoric acids—along with an unidentified compound that fluoresces pink under ultraviolet light. Together with the branched paraphyses and the distinctive iodine-positive ascus apex, these features separate ''Rimularia'' from superficially similar brown-spored genera such as ''Porpidia'' and ''Fuscidea''.<ref name="Orange et al. 2021"/>
==Species== {{As of|2025|July}}, Species Fungorum (in the Catalogue of Life) accept 14 species of ''Rimularia'':<ref name="CoL_CDZD4"/> *''Rimularia actinostoma'' {{au|Coppins & Fryday (2006)}}<ref name="Coppins & Fryday 2006"/> *''Rimularia australis'' {{au|Hertel & Rambold (1990)}}<ref name="Rambold 1989"/> *''Rimularia austrolimborina'' {{au|Coppins & Fryday (2006)}}<ref name="Coppins & Fryday 2006"/> *''Rimularia badioatra'' {{au|(Kremp.) Hertel & Rambold (1990)}}<ref name="Hertel & Rambold 1990"/> *''Rimularia geumodoensis'' {{au|(S.Y.Kondr., Lőkös & Hur) S.Y.Kondr., Lőkös & Hur (2016)}} *''Rimularia gibbosa'' {{au|(Ach.) Coppins, Hertel & Rambold (1990)}}<ref name="Hertel & Rambold 1990"/> *''Rimularia hensseniae'' {{au|Hertel & Rambold (1990)}}<ref name="Hertel & Rambold 1990"/> *''Rimularia intercedens'' {{au|(H.Magn.) Coppins (1993)}} *''Rimularia limborina'' {{au|Nyl. (1868)}} *''Rimularia michoacanensis'' {{au|(B.de Lesd.) Timdal (2002)}}<ref name="Timdal 2002"/> *''Rimularia paradoxa'' {{au| Timdal & W.A.Weber (2002)}}<ref name="Timdal 2002"/> *''Rimularia psephota'' {{au|(Tuck.) Hertel & Rambold (1987)}}<ref name="Hertel 1987"/> *''Rimularia ramboldiana'' {{au|Kantvilas & Elix (2007)}}<ref name="Kantvilas & Elix 2007"/> *''Rimularia subconcava'' {{au|(H.Magn.) Timdal (2002)}}<ref name="Timdal 2002"/>
==References== {{Reflist|colwidth=30em|refs=
<ref name="CoL_CDZD4">{{Catalogue of Life |id=CDZD4 |title=''Rimularia'' |access-date=9 July 2025}}</ref>
<ref name="Coppins & Fryday 2006">{{cite journal |last1=Coppins |first1=Brian J. |last2=Fryday |first2=Alan M. |title=New or previously misunderstood species of ''Lithographa'' and ''Rimularia'' (Agyriaceae) from the southern subpolar region and western Canada |journal=The Lichenologist |volume=38 |issue=2 |year=2006 |doi=10.1017/S0024282906005512 |pages=93–107 |bibcode=2006ThLic..38...93C |url=https://www.researchgate.net/publication/231982394}}</ref>
<ref name="Hertel 1987">{{cite journal |last=Hertel |first=H. |year=1987 |title=Bemerkenswerte Funde südhemisphärischer, saxicoler Arten der Sammelgattung ''Lecidea'' |trans-title=Remarkable finds of southern hemisphere, saxicolous species of the collective genus ''Lecidea'' |journal=Mitteilungen aus der Botanischen Staatssammlung München |volume=23 |pages=321–340 |language=de}}</ref>
<ref name="Hertel & Rambold 1990">{{cite book |last1=Hertel |first1=H. |last2=Rambold |first2=G. |year=1990 |chapter=Zur Kenntnis der Familie Rimulariaceae (Lecanorales) |editor-first1=H.M. |editor-last1=Jahns |editor-first2=Volkmar |editor-last2=Wirth |editor-first3=Josef |editor-last3=Poelt |title=Contributions to Lichenology in Honour of A. Henssen |series=Bibliotheca Lichenologica |volume=38 |publisher=J. Cramer |location=Berlin-Stuttgart |pages=145–189 |isbn=978-3-443-58017-9}}</ref>
<ref name="Kantvilas & Elix 2007">{{cite journal |last1=Kantvilas |first1=G. |last2=Elix |first2=J.A. |year=2007 |title=Additions to the lichen family Agyriaceae Corda from Tasmania |journal=Bibliotheca Lichenologica |volume=95 |pages=317–333}}</ref>
<ref name="Nylander 1868">{{cite journal |last=Nylander |first=W. |title=Addenda nova ad lichenographiam europaeam. Continuatio octava |journal=Flora (Regensburg) |year=1868 |volume=51 |pages=342–348 [346] |language=la |url=https://www.biodiversitylibrary.org/page/58318}}</ref>
<ref name="Orange et al. 2021">{{cite book |last1=Orange |first1=A. |last2=Cannon |first2=P. |last3=Aptroot |first3=A. |last4=Coppins |first4=B. |last5=Sanderson |first5=N. |last6=Simkin |first6=J. |year=2021 |title=Baeomycetales: Trapeliaceae, including the genera ''Coppinsia'', ''Placopsis'', ''Placynthiella'', ''Rimularia'', ''Trapelia'' and ''Trapeliopsis'' |series=Revisions of British and Irish Lichens |volume=18 |page=7 |url=https://britishlichensociety.org.uk/sites/default/files/Trapeliaceae.pdf}}</ref>
<ref name="Rambold 1989">{{cite journal |last=Rambold |first=G. |year=1989 |title=A monograph of the saxicolous lecideoid lichens of Australia (excl. Tasmania) |journal=Bibliotheca Lichenologica |volume=34 |pages=300–302}}</ref>
<ref name="Timdal 2002">{{cite journal |last=Timdal |first=E. |year=2002 |title=Three squamulose species of ''Rimularia'' (Lecanorales) |journal=The Bryologist |volume=105 |issue=2 |pages=219–224 |doi=10.1639/0007-2745(2002)105[0219:TSSORL]2.0.CO;2 }}</ref>
}}
{{Taxonbar|from=Q7334526}}
Category:Baeomycetales Category:Baeomycetales genera Category:Lichen genera Category:Taxa named by William Nylander (botanist) Category:Taxa described in 1868