Placopyrenium

Placopyrenium is a genus of saxicolous (rock-dwelling), crustose lichens in the family Verrucariaceae.

Taxonomy
The genus was circumscribed in 1987 by the Austrian lichenologist Othmar Breuss. He assigned Placopyrenium bucekii as the type species.

Description
The genus Placopyrenium is characterised by its (growing on rocks) thallus, which is thick and distinctly patterned, breaking into  (small, island-like sections) or squarrose-areolate (with scale-like, spreading areoles). These areoles have a unique shape, being noticeably narrowed at their base and extending into elongated stipes (stalks), which are ashen in colour on the upper surface due to a protective, while the underside is black. The thallus lacks (root-like hyphae) and the stipes are directly attached to the.

The entire thallus is composed of cells that are either angular or rounded, measuring 5–10 μm in diameter, forming a structure that is nearly, meaning the cells are closely packed together. The areolae's base and sides are enveloped in a (blackened) cortical layer, providing durability and protection.

In terms of reproductive structures, Placopyrenium develops (fruiting bodies) within the thallus. These perithecia lack an (an outer layer or envelope). The asci (spore-producing structures) within the perithecia are, meaning they are shaped like a club. The spores produced in these asci are arranged in two rows, and are either ellipsoidal or ovoid-oblong in shape. These spores are colourless and typically, although they are often uniseptate, meaning they have a single internal division (septum). Additionally, the genus produces short, rod-shaped conidia (asexual spores).

Species

 * Placopyrenium ariyanense Moniri & Breuss (2017) – Iran
 * Placopyrenium breussii Cl.Roux & Gueidan (2011) – Europe
 * Placopyrenium bucekii (Nádv. & Servít) Breuss (1987)
 * Placopyrenium bullatum Aptroot & Yazıcı (2012) – Turkey
 * Placopyrenium caeruleopulvinum (J.W.Thomson) Breuss (2002)
 * Placopyrenium cinereoatratum (Degel.) Orange (2009) – Europe
 * Placopyrenium coloradoense Breuss (2009)
 * Placopyrenium conforme Breuss (2009)
 * Placopyrenium formosum Orange (2009) – Europe
 * Placopyrenium heppioides (Zahlbr.) Breuss (2002)
 * Placopyrenium insuetum Breuss (2000)
 * Placopyrenium iranicum Breuss (2009)
 * Placopyrenium stanfordii (Herre) K.Knudsen (2006)
 * Placopyrenium tatrense (Vězda) Breuss (1990)
 * Placopyrenium trachyticum (Hazsl.) Breuss (1987)
 * Placopyrenium zahlbruckneri (Hasse) Breuss (2002)