[3][4] In 2022 the family Cortinariaceae, which previously contained only the one genus of Cortinarius was reclassified based on genomic data and split into the genera of Cortinarius, Aureonarius, Austrocortinarius, Calonarius, Cystinarius, Hygronarius, Mystinarius, Phlegmacium, Thaxterogaster and Volvanarius.

Numerous Cortinarius species were transferred into the genus of Thaxterogaster as a result of this work.

[5] The genus is further divided with subgenus and section classifications:[5] Thaxterogaster is named for the mycologist Roland Thaxter who deposited a specimen at the Farlow Herbarium under the name Secotium magellanicum.

This specimen was examined by Singer and used as the basis for his description of Thaxterogaster magellanicum.

The genus is named for Thaxter whilst 'gaster' refers to the, now obsolete, class Gasteromycetes since the species is gasteroid in form.