Marasmius plicatulus

The cap is mahogany with a velvety texture and up to 4 centimetres (1+1⁄2 in) wide.^[1][2] The gills are adnate, widely spaced, and pallid to pinkish. The stipe is dark, smooth, up to 13 cm (5 in) long and 3 mm (1⁄8 in) thick.^[1][2][3] The spore print is white.^[2] It is too tough and thin for consideration as edible.^[2]

It is the largest Marasmius species found on the North American West Coast.^[4][5] Some members of the genus from further east are vaguely similar.^[1]

The red pinwheel is often found in association with oak trees or conifers.^[5] From November to February, it is common on the Pacific coast,^[1] but it has been observed as far inland as Idaho.^[5]