Tricholoma ustaloides

The cap is red-brown or chestnut-brown with a paler margin, very sticky when moist, and has a diameter of 4 to 8 cm (1.6 to 3.1 in).^[1] The overall shape of the cap is bell-like when young, later flattening to a more irregular convex shape in maturity, and often developing a lobed appearance. The margins of the caps are usually turned inwards. The gills are crowded together, adnate or emarginate in attachment to the stipe, and white or a light ochraceous yellow with dark brown stains when old or bruised. The stipe is 4 to 10 cm (1.6 to 3.9 in) long by 1 to 2 cm (0.4 to 0.8 in) thick, roughly spindle-shaped (fusiform), with red-brown fibrils and a sharply defined zone of white color at the stalk apex, especially in more mature specimens.^[2] The flesh is white or cream, smelling strongly of meal, with a bitter taste.^[3][4]

Spores have a roughly spherical or ellipsoid shape, are hyaline, smooth, non-amyloid, and have dimensions of 5.5—7.0 x 4.5—5.5 μm.^[1] Basidia are 4-spored and cystidia are absent.^[4]

This mycorrhizal species typically grows in small groups, and is often found near trees in the genera Quercus and Fagus.^[1]

Although relatively rare, it has a widespread distribution in Europe, limited by the presence of its preferred tree hosts. Its first recorded appearance in Mexico was 1984.^[5]