Change based on synonymy in A Cumulative Checklist for the Lichen-forming, Lichenicolous and Allied Fungi of the Continental United States and Canada, Version 21. Esslinger recognizes no subspecies. Underlying change based on Arup et al. (2013), who write of this new genus,

Almost all species with poorly developed or lacking thallus except A. scopularis which has a well-developed, lobate thallus. Cortex, when developed, mostly an amorphous layer or consisting of an indistinctly paraplectenchymatous tissue, named alveolate by Vondrák et al. (2009), although in A. scopularis composed of anticlinally arranged hyphae. A. vitellinula with a conspicous but usually very thin thallus. Apothecia mainly zeorine; spores polardiblastic with medium to long septum. Pycnidia orange but usually lacking; conidia ellipsoid.

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Taxonomy: Athallia is a well-supported monophyletic group. Even though A. skii is on a long branch at the base of the clade in the ITS analysis (Fig. 2) it ts in all respects very well with the rest of the genus; thus there is no problem to accommodate it in the genus. According to the combined analysis the closest relatives seem to be Calogaya and Flavoplaca with mainly lobate and crustose members, respectively. e species in Athallia cannot with certainty be separated from the genus Flavoplaca without a molecular analysis, but because it is not in a sister relationship to Athallia it cannot be united with this genus without includ- ing also several other genera (Fig. 1). Usually the species in Flavoplaca produce a more strongly developed thallus than those in Athallia and often form also soredia or blastidia. ere are also several species in other genera, e.g. Polycauliona and Parvoplaca, having a reduced thallus similar to many species in Athallia.