{{Short description|Species of lichen}} {{Use dmy dates|date=October 2025}} {{Use Oxford spelling|date=October 2025}} {{Speciesbox | image = Buellia venusta - Flickr - pellaea (2).jpg | taxon = Diplotomma venustum | authority = Körb. (1860) | synonyms_ref = <ref name="Species Fungorum synonymy"/> | synonyms = {{Collapsible list|bullets=on |''Rhizocarpon alboatrum'' var. ''venustum'' {{au|(Körb.) Anzi (1864)}} |''Buellia alboatra'' var. ''venusta'' {{au|(Körb.) Th.Fr. (1874)}} |''Lecidea alboatra'' var. ''venusta'' {{au|(Körb.) Vain. (1883)}} |''Diplotomma epipolium'' f. ''venustum'' {{au|(Körb.) Arnold (1884)}} |''Buellia epipolia'' var. ''venusta'' {{au|(Körb.) Mong. (1900)}} |''Lichen amylaceus'' var. ''venusta'' {{au|(Körb.) Mong. (1900)}} |''Buellia venusta'' {{au|(Körb.) Lettau (1913)}} |''Diplotomma epipolium'' var. ''venustum'' {{au|(Körb.) Szatala (1938)}} |''Buellia margaritacea'' var. ''venusta'' {{au|(Körb.) Räsänen (1943)}} |''Diplotomma alboatrum'' var. ''venustum'' {{au|Körb. (1858)}} |''Lecidea epipolia'' var. ''venusta'' {{au|Körb. ex Hepp (1860)}} }} }}
'''''Diplotomma venustum''''' is a species of saxicolous (rock-dwelling) crustose lichen in the family Caliciaceae.<ref name="CoL_36P3H"/> It is widely distributed, having been recorded from all continents, where it grows on calcareous rocks.<ref name="Kantvilas 2025"/>
==Taxonomy==
The lichen was first formally described as a new species by German lichenologist Gustav Wilhelm Körber in 1860. Körber's Latin {{lichengloss|diagnosis}} emphasised the firmly attached, granular-powdery thallus with very fine wrinkling, and the mostly solitary apothecia that are immersed in the thallus when young but become convex with a black {{lichengloss|disc}}. He characterised the colourless ascospores as ellipsoidal to spindle-shaped with 4 cross-walls (4-septate) and noted they turn sooty-brown with age. The species was described from limestone and dolomite rocks in mountainous regions of central Europe, including collections from Germany, Austria, and the Carpathian Mountains.<ref name="Körber 1860"/>
==Description==
''Diplotomma venustum'' forms a crust-like thallus that is tightly attached to the substrate (crustose) and often broken up by numerous irregular cracks and fissures ({{lichengloss|rimose}}). The margin may become weakly {{lichengloss|lobed}}. A thin black border (the {{lichengloss|prothallus}}) is sometimes visible around the thallus. The upper surface is chalky white, grey, or ochre-tinged and lacks powdery vegetative propagules. The interior (medulla) is white and contains abundant needle-shaped crystals of calcium oxalate; these crystals also generate the fine white {{lichengloss|pruina}} that commonly dusts the fruiting {{lichengloss|discs}}. Under ultraviolet light the thallus does not fluoresce (UV−), and standard spot tests on the thallus and medulla are negative in North American material (K−, P−, C−); outside North America, some collections react K+ (yellow turning red) and P+ (yellow-orange), reflecting the presence of norstictic and connorstictic acids in the medulla.<ref name="Timdal 2007"/>
==References== {{Reflist|refs=
<ref name="CoL_36P3H">{{Catalogue of Life |id=36P3H |title=''Diplotomma venustum'' Körb. |access-date=16 October 2025}}</ref>
<ref name="Kantvilas 2025">{{cite web |last=Kantvilas|first=Gintaras |title=''Diplotomma'' |url=https://flora.tmag.tas.gov.au/lichen-genera/diplotomma/ |work=Flora of Tasmania Online |publisher=Tasmanian Herbarium, Tasmanian Museum and Art Gallery |location=Hobart |access-date=16 October 2025}}</ref>
<ref name="Körber 1860">{{cite book |last=Körber |first=Gustav Wilhelm |year=1865 |title=Parerga lichenologica. Ergänzungen zum Systema lichenum Germaniae |volume=2 |publisher=E. Trewendt |location=Breslau |page=179 |language=de |url=https://www.biodiversitylibrary.org/page/45825692 |doi=10.5962/bhl.title.87905}}</ref>
<ref name="Species Fungorum synonymy">{{cite web |title=GSD Species Synonymy. Current Name: ''Diplotomma venustum'' Körb., Parerga lichenol. (Breslau) 2: 179 (1860) |url=https://www.speciesfungorum.org/GSD/GSDspecies.asp?RecordID=384514 |publisher=Species Fungorum |access-date=16 October 2025}}</ref>
<ref name="Timdal 2007">{{cite book |year=2007 |chapter=''Romjularia'' |title=Lichen Flora of the Greater Sonoran Desert Region |editor-first1=Thomas H. |editor-last1=Nash III |editor-first2=Corinna |editor-last2=Gries |editor-first3=Frank |editor-last3=Bungartz |volume=3 |publisher=Lichens Unlimited, Arizona State University |location=Tempe |pages= |url=https://lichenportal.org/portal/taxa/index.php?taxon=Diplotomma+venustum+%28K%C3%B6rb.%29+K%C3%B6rb.&tid=55030&formsubmit=Search+Terms}}</ref>
}}
{{Taxonbar |from1=Q10473793 |from2=Q108697428 |from3=Q108572867 |from4=Q108573434 |from5=Q105486850 |from6=Q108574233 |from7=Q108596459}}
Category:Caliciales Category:Lichens described in 1858 Category:Cosmopolitan lichens Category:Taxa named by Gustav Wilhelm Körber