Calonarius oliveopetasatus

Calonarius oliveopetasatus, formerly known as Cortinarius oliveopetasatus,^[1] is a species of mushroom in the family Cortinariaceae. It is rare.^[2]

The cap of Calonarius oliveopetasatus starts out dark green, before becoming olive brown as the mushroom gets older. It starts out round or convex and becomes convex or flat.^[2] The gills start out buff in color and become yellowish and eventually rusty brown.^[3] The stipe is about 5.5-10 centimeters long and 1–2.5 centimeters wide. It has a bulbous base that is about 2.5-4.5 centimeters wide. The stipe is yellowish to brownish.^[4] A cortina is present and the spore print is rusty brown.^[2] The spores can be almond-shaped or lemon shaped, and there are four spores per basidium. Cheliocystidia are absent, but clamp connections are present.^[4] When potassium hydroxide is applied, the cap of the mushroom turns orangish brown and the stipe turns dark brown.^[3]

Calonarius oliveopetasatus grows under conifers such as douglas fir. It is found on the Olympic Peninsula and in the Cascades, where it grows in old-growth forests.^[2]