High Quality Content by WIKIPEDIA articles! Paxillus involutus, commonly known as the brown roll-rim, common roll-rim, or poison pax, is a basidiomycete fungus widely distributed across the Northern Hemisphere. It has been unintentionally introduced to Australia, New Zealand, and South America, where it has likely been transported in soil with European trees. Various shades of brown in colour, the fruit body grows up to 6 cm (2.4 in) high and has a funnel-shaped cap up to 12 cm (5 in) wide with a distinctive inrolled rim and decurrent gills that may be pore-like close to the stipe. Although it has gills, it is more closely related to the pored boletes than to typical gilled mushrooms. It was first described by Pierre Bulliard in 1785, and was given its current binomial name by Elias Magnus Fries in 1838. Genetic testing suggests that Paxillus involutus may be a species complex rather than a single species.