[1][2] The genus was circumscribed in 2014 by lichenologists Sergey Kondratyuk, Ingvar Kärnefelt, John Alan Elix, Arne Thell, and Jae-Seoun Hur.

The cortical layer of the thallus is described as palisade plectenchymatous, meaning it consists of tightly packed cells arranged in a palisade-like formation.

When treated with a solution of potassium hydroxide (i.e., the K spot test), the thallus and apothecia show a purple reaction.

[3] In terms of similarities, Franwilsia closely resembles the genus Mikhtomia in having a hymenium, subhymenium, and basal portion of the true exciple rich in oil droplets.

However, Franwilsia is differentiated by its specific structure of the true exciple and the presence of larger, irregular oil aggregations in the subhymenium.