A tough, whitish to tan, often kidney-shaped tooth fungus on hardwood sticks, with short packed spines that age from white to dark brown and black. The cap margin blackens with maturity. It is common in eastern North America.
Widely distributed in North America east of the Great Plains; reliably documented from the Caribbean, Central America, Brazil and Russia. East Asian records probably represent M. subadustum (MushroomExpert).
Characteristics
Cap: 4-8 cm, circular to kidney-shaped or lobed, flat to shallowly depressed; dry, bald or finely velvety, often lumpy; white to buff, tan or grayish, zoned; bruises slowly grayish; thin margin becomes dark brown to black. Spines: 2-5 mm, tightly packed, white becoming brown and then black from the margin inward; may look poroid near the margin. Stem: often absent or reduced, to 4 cm, central or lateral. Flesh: white, tough. Odor and taste: not distinctive. Spore print: white. Spores: 3-4 x 0.5-1 um, sausage-shaped, smooth (MushroomExpert).
