''Placidium nigrum'' is a species of
squamulose
A squamulose lichen is a lichen that is composed of small, often overlapping "scales" called squamules. If they are raised from the substrate and appear leafy, the lichen may appear to be a foliose lichen, but the underside does not have a "skin ...
(scaley),
ground-dwelling lichen in the family
Verrucariaceae
The Verrucariaceae are a family of mostly lichenised fungi in the order Verrucariales. The lichen-forming species, which comprise the vast majority of the family, have a wide variety of thallus forms, and include crustose (crust-like), foliose ( ...
. It is found in
Northwest China
Northwest China () is a statistical region of China which includes the autonomous regions of Xinjiang and Ningxia and the provinces of Shaanxi, Gansu and Qinghai. It has an area of 3,107,900 km2.
The region is characterized by a (semi-)arid con ...
and the
Tibetan Plateau
The Tibetan Plateau (, also known as the Qinghai–Tibet Plateau or the Qing–Zang Plateau () or as the Himalayan Plateau in India, is a vast elevated plateau located at the intersection of Central, South and East Asia covering most of the Ti ...
, where it grows on sandy soil surfaces in semi-arid and arid regions.
The lichen was
formally described as new to science in 2022 by Tingting Zhang and Xinli Wei. The
type specimen
In biology, a type is a particular wiktionary:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to a ...
was collected from the
Da Qaidam
Da Qaidam is an administrative committee in Haixi Prefecture in northwestern Qinghai province, China. It borders Gansu province to the north.
The area administered as is divided between the two towns of Qaidam itself also called Xitieshan ...
(
Haixi Mongol and Tibetan Autonomous Prefecture
Haixi Mongolian and Tibetan Autonomous Prefecture (; mn, á ¬á á ¶á ¢á °á ¢â€¯á ¶á ¢á ¨ á ®á £á ©á á £á ¯ á ²á ¥á ªá ¡á ³ á ¦á ¨á ³á ¦á °á ¦á ²á ¡á ¨â€¯á ¦ á ¥á ªá ¡á ·á ²á ¡á á ¡á ¨ á µá á °á á ¬á ¤ á µá §á ¦; bo, མཚོ་ནུབ་འ...
), at an altitude of ; it has since been collected at altitude ranges between . The
species epithet ''nigrum'' alludes to the black area surrounding the
thallus
Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms wer ...
that results from an aggregation of
pycnidia
A pycnidium (plural pycnidia) is an asexual fruiting body produced by mitosporic fungi, for instance in the order Sphaeropsidales ( Deuteromycota, Coelomycetes) or order Pleosporales (Ascomycota, Dothideomycetes). It is often spherical or inve ...
(
asexual fruiting bodies). These abundant, tiny pycnidia occur both superficially on the thallus surface (''laminal'') and on the lobe edges (''marginal''). ''Placidium nigrum'' does not react with any of the standard
chemical spot tests, and no
lichen product
Lichen products, also known as lichen substances, are organic compounds produced by a lichen. Specifically, they are secondary metabolites. Lichen products are represented in several different chemical classes, including terpenoids, orcinol deriva ...
s were detected from the species using
thin-layer chromatography
Thin-layer chromatography (TLC) is a chromatography technique used to separate non-volatile mixtures.
Thin-layer chromatography is performed on a sheet of an inert substrate such as glass, plastic, or aluminium foil, which is coated with a t ...
.
References
Verrucariales
Lichen species
Lichens described in 2022
Lichens of China
{{Eurotiomycetes-stub