[2] It was first formally described as a new species in 1953 by Swedish lichenologist Adolf Hugo Magnusson, as a member of the genus Caloplaca.

The type specimen was collected in 1939 by John Walter Thomson in Lake Koshkonong, Wisconsin.

In the original description, Magnusson notes a similarity to the lichen now known as Gyalolechia flavovirescens, but distinguishes the new species by its lack of a visible thallus, the sordid-reddish color of its discs, and the "unusually narrow" septa of the spores.

[3] Patrik Frödén, Ulf Arup, and Ulrik Søchting transferred the taxon to Xanthocarpia in 2013, following molecular phylogenetic analysis of the family Teloschistaceae.

Despite the nearly imperceptible thallus, the tiny apothecia can grow so profusely so as discolor large areas of sidewalks yellow.