Pyrenodesmia micromarina

Pyrenodesmia micromarina is a species of saxicolous (rock-dwelling), crustose lichen in the family Teloschistaceae. It is found in the Eastern Mediterranean, specifically along the coasts of the Black Sea and the Sea of Marmara in Russia, Turkey, and Ukraine. It grows on coastal rocks and occasionally concrete, often in Mediterranean scrub vegetation.

Taxonomy
The lichen was first formally described as a new species in 2016 by the lichenologists Ivan Frolov, Oleksandr Khodosovtsev, and Jan Vondrák, who placed it in the genus Caloplaca. The type specimen was collected near Gaziköy in a small brook valley at elevations of 20 – above sea level. Frolov and Vondrák later transferred it to genus Pyrenodesmia.

Description
This species of Pyrenodesmia is recognized by several key features: it lacks anthraquinones (common in the family Teloschistaceae), and its thallus, which is usually thinner than 200 μm, does not have a distinct cortex and has a colouration. The mature apothecia are typically smaller than 0.5 mm in diameter, with a black with a true, zeorine exciple.

The thallus of Pyrenodesmia micromarina is ochre to grey, occasionally with white spots, and forms small, irregular to roundish spots. It consists of tightly arranged, flat. The medulla is inconspicuous, and the is made up of spherical cells. The is usually not developed, but an  cortex might be present with an indistinct boundary. The lichen does not have vegetative diaspores and occasionally has a white, particularly around the apothecia.

Apothecia are small, with a black and a  that matches the thallus in colour. The hymenium is colourless and may contain stacks of extracellular crystals. The asci are, containing eight , colourless with rather wide septa.

are commonly observed, with darker grey tops on the thallus surface. The are ellipsoid to broadly ellipsoid.

Chemistry
Chemical tests reveal that the thallus and apothecia are negative for potassium hydroxide (K), calcium hypochlorite (C), and p-phenylenediamine (P) reactions and are not fluorescent under ultraviolet light. The and the outer cells of the  contain, which reacts to water and potassium hydroxide. However, no substances were detected by high-performance liquid chromatography in apothecia and thallus samples.

Distribution and ecology
Caloplaca micromarina is a maritime species found in the Eastern Mediterranean, specifically along the coasts of the Black Sea and the Sea of Marmara in Russia, Turkey, and Ukraine. It grows on coastal rocks and occasionally concrete, often in Mediterranean scrub vegetation. The species co-occurs with various lichens including Aspicilia contorta, Caloplaca conversa, and Candelariella aurella.