Rhizocarpon torquatum
Rhizocarpon torquatum is a species of saxicolous, crustose lichen in the family Rhizocarpaceae. This species is recognised by its pale, thick, smooth, thallus that contains hypostictic acid as a major metabolite, and its large apothecia that are distinctively adorned with a whitish inner collar in immature stages.
Taxonomy
It was first described by the lichenologists Patrick M. McCarthy, John Alan Elix, and Gintaras Kantvilas. The specific epithet torquatum—meaning adorned with a collar in Latin—refers to the characteristic appearance of the apothecia's margin, which often retains a whitish inner collar. This feature, along with the chemical profile and apothecial anatomy, helps distinguish Rhizocarpon torquatum from similar species.Description
The thallus of Rhizocarpon torquatum is crustose and, forming colonies approximately wide, varying in colour from greyish white to pale grey with a greenish tint. The thallus, up to 300 micrometre thick, with a to texture with smooth to coarsely areoles that are contiguous and mostly flat. The thallus lacks a true, instead featuring an uppermost directly above a discontinuous.Apothecia are numerous, ranging from 0.52 to 1.30 mm in diameter, with a margin that can be thick and varies from being the same as the blackish to considerably paler. These reproductive structures are initially embedded but become more prominent as they mature. The is annular, typically darkening to brown-black, and the is thick.