The fruit body is typically reddish brown to rusty orange to yellow, medium to large, often with a well-developed veil.
Similar genera
Members of Pholiota and Cortinarius are easy to confuse with Gymnopilus. Pholiota can be distinguished by its viscid cap and duller (brown to cinnamon brown) spores, and Cortinarius grows on the ground. Beginners can confuse Gymnopilus with Galerina, which contains deadly poisonous species.
Taxonomy
Gymnopilus was formerly divided among Pholiota and the defunct genus Flammula. The genus has over 200 species worldwide.[2]
Several species of Gymnopilus contain bis-noryangonin [4-hydroxy-6-(4-hydrostyryl)-2-pyrone] and hispidine [4-hydroxy-6-(3,4-dihydroxystyryl)-2-pyrone], which are closely related to the alpha-pyrones found in kava.[8]
a clade formed by G. underwoodii, G. validipes and G. cf. flavidellus
aeruginosus-luteofolius group
lepidotus-subearlei group
Although the genus Gymnopilus was found to be monophyletic, the phylogenetically related groups do not support the traditional infrageneric classifications based on morphology.
^ abcdeGuzmán-Dávalos L. (2006). "A new bluing, probably hallucinogenic species of Gymnopilus P. Karst. (Agaricomycetideae) from Mexico". International Journal of Medicinal Mushrooms. 8 (3): 289–293. doi:10.1615/intjmedmushr.v8.i3.110. ISSN1521-9437.