The genus was first described by Italian mycologist Giacomo Bresadola in 1911,[1] and contains two widely distributed species,[2] J. argillacea and J. ochroleuca.

The genus name of Jaapia is in honour of Otto Jaap (1864 - 1922), who was a German botanist (Mycology, Lichenology and Bryology).

Molecular phylogenetics analysis showed it to be a sister group (one of two clades to the Gloeophyllales, resulting from the splitting of a single lineage) to the rest of the Agaricomycetidae.

[4] Sexual states occur on rotting, water-saturated wood and are filmy, patchy basidiocarps with cylindrical cystidia intermixed with basidia with four long sterigmata and narrowly fusoid basidiospores.

[5] The genome of Jaapia argillacea lacks lignin-degrading peroxidases typical of white rot fungi, but has fifteen genes coding for lytic polysaccharide monooxygenases; experiments demonstrate localized erosion of all wood cell wall layers, similar to other white rots.