[2] The genus is characterized by a corticate thallus and diverse ascomata structures, which can be simple, aggregated, or forming pseudostromata.

The genus was circumscribed in 1824 by German botanist Franz Gerhard Eschweiler, with Astrothelium conicum assigned as the type species.

The ostioles, or small openings that allow the release of spores, can be located at the apex or eccentrically on the ascomata and may appear as either simple or fused structures.

[4] Within the hamathecium, the tissue that houses the asci (spore-producing structures), the cells are either clear or filled with oil droplets.

They can also exhibit a variety of forms, including transversely septate or muriform, reflecting their segmented or multi-cellular nature.