The genus was circumscribed in 1979 by Josef Poelt and Peter Döbbeler, with the muscicolous lichen Bryostigma leucodontis assigned as the type species.

[4] These taxonomic changes have been disputed, however; in the Revisions of British and Irish Lichens series, the authors note: "Work by Kondratyuk et al. (2020) included twelve new combinations into Bryostigma for these lichenicolous species, but added minimally to understanding of the clade and introduced several errors.

The reproductive structures, called apothecia, are small, convex, and dark brown to black in colour, without a powdery coating (pruina).

The middle layer (hymenium) is either colourless or slightly green, while the base (hypothecium) is darker, sometimes reddish-brown, and reacts similarly to the epithecium with KOH.

The genus also features small reproductive bodies called pycnidia, which are embedded in the thallus and have a reddish-brown outer wall.