Extremus Quaedvl. & Crous, Fungal Systematics and Evolution 3: 127 (2019).
MycoBank number: MB 829395; Index Fungorum number: IF 829395; Facesoffungi number: FoF 06848; 2 morphological species (Species Fungorum 2020), 1 species with molecular data.
Type species – Extremus adstrictus Quaedvl. & Crous.
Notes – Extremus is the type genus of Extremaceae. Quaedvlieg et al. (2014) informally established this genus which was validated by Crous et al. (2019b). It is characterized by brown, subcylindrical to ellipsoid conidiogenous cells, catenate, subcylindrical to ellipsoid conidia with hyaline to slightly darkened hila. Quaedvlieg et al. (2014) transferred Devriesia adstricta and D. antarctica to Extremus based on phylogenetic analysis. The genus now contains two species and their morphology is only known from culture (Egidi et al. 2014).