Caloplaca pseudocitrina

Caloplaca pseudocitrina, a little-known species of lichen saxicolous (rock-dwelling) lichen in the family Teloschistaceae. Found in southern Tajikistan, it has a (scaley) thallus forming extensive yellow-orange spots. It was formally described as a new species in 2002 by the lichenologists Imomnazar Kudratov and Oleksandr Khodosovtsev.

Taxonomy
Caloplaca pseudocitrina is a part of the Caloplaca citrina species complex, which, at the time its original publication, was had not yet been resolved taxonomically. It is distinguished from Caloplaca citrina (in the broad sense) by its larger coupled with a narrow septum (internal partition). Similar taxa like C. citrina var. arcis, known only in a sterile state, and soil-dwelling relatives C. heterospora and C. tominii, also have narrow spore septa but differ in other morphological aspects.

Description
The thallus of Caloplaca pseudocitrina is, forming expansive spots that can reach several centimetres in diameter. The are yellow-orange, flat to, and range from 0.2 to 2.0 mm in size. These squamules, either solitary or composed of 3–6 microlobes, attach centrally to the with somewhat free margins and are. The cortex is, measuring 18–24 μm in thickness, with cells around 4.8–7.2 μm. Soralia are typically developed at the edges of the squamules, with, yellow-orange soredia measuring 30–50 μm in diameter.

Apothecia in this species are to, ranging from 0.2 to 1.2 mm in width, generally one or two per squamule. The varies from concave to convex, orange in colour, with a yellow-orange margin. The is, thickening from 15 to 20 μm in the centre to 90–110 μm laterally. The is poorly developed. The is yellowish, about 10 μm high. The is hyaline and measures 30–50 μm in height. The hymenium stands 40–60 μm tall. Paraphyses are unbranched to apically branched, 1.8–2.2 μm wide, with apical cells reaching 3.6–4.5 μm in width. Asci contain eight spores each. The is from the green algal genus Trebouxia, with cells measuring 6.0–12.0 μm in diameter.

Habitat and distribution
This species has so far been observed growing on metamorphic limestone in the arid regions of southern Tajikistan at high altitudes, particularly in the Chormagzak pass, "Schirbibi" locality, at an elevation of around 1850 m.