Marasmius siccus

Common Name: Orange Pinwheel
Description: Cap 0.5-3 cm across, bell-shaped with flattened or depressed center, with deep, wide, radial pleats; rust-orange to rust-brown or pale tawny; minutely velvety. Stem 20-70 by 1-2 mm high and wide.
Habitat: scattered to gregarious on leaves, wood, twigs, etc., of deciduous trees. Very common. Found east of the Great Plains in North America.
Edible: unknown.

Source: Mushrooms of North America by Roger Phillips.