Wolfiporia extensa is a  wood-decay fungus of the genus Wolfiporia that is used extensively as a medicinal mushroom and a source of a triterpenoid compound, pachymic acid in Chinese medicine.
It is a wood-decay fungus but has a subterranean growth habit. Genus: Wolfiporia W. extensa is also used extensively as a medicinal mushroom in Chinese medicine. Wolfiporia extensa is a source of a triterpenoid compound, pachymic acid, which has been the object of scientific study based upon the mushroom's role in traditional Chinese medicine. 
