Tylocliostomum
Tylocliostomum is a fungal genus in the family Ramalinaceae. It comprises the single species Tylocliostomum viridifarinosum.
Taxonomy
The genus Tylocliostomum was circumscribed in 2020 by the lichenologists Pieter P.G. van den Boom and Nicolas Magain. It is distinguished from the related genus Tylothallia by several microscopic features, including its different spore-containing structures and simpler filaments in the reproductive tissue. Unlike the somewhat similar-looking genus Cliostomum, it lacks spore-producing structures called pycnidia and has a different cellular arrangement in its fruiting body wall. The genus name Tylocliostomum alludes to its evolutionary relationships and appearance, combining elements of two related genera: Tylothallia, with which it shares genetic ancestry, and Cliostomum, which it resembles in its outward appearance.Description
Tylocliostomum viridifarinosum forms a thin, continuous crust on its, with a distinctive powdery or mealy texture. The surface consists of tiny green granules measuring 8–20 micrometres in diameter. The lichen's reproductive structures are small, ranging from 0.15 to 0.4 millimetres across, and vary from flat to slightly convex. These apothecia have a rim that is either the same colour as or slightly paler than the central, though this rim often disappears as the structure matures. The disc itself can be white to pale cream, sometimes with a slight yellowish tinge, or occasionally medium grey with a bluish-grey cast.When examined microscopically, the spores are narrowly ellipsoid to rod-shaped, measuring 11–17 by 2.5–3.2 μm, with a single cross-wall and thin walls. Each spore-producing sac contains eight spores. The species contains no detectable lichen substances when tested with standard chemical spot tests.