Unexpanded cap cylindrical-elliptical, 3.0-6.0 cm tall x 2.0-2.5 cm broad, broadly obtuse-conic in age, final diameter up to 7.0 cm; margin at first tight to the stipe, blunt, striate, then decurved, at maturity often radially torn, recurved or collapsing towards the stipe; surface more or less glabrous at the disc, pale-tan, elsewhere whitish, striate-plicate, fibrillose to squamulose, the scales recurved with tan-brown tips, eventually blackening from the margin; context white, 3 mm at the disc, less than 1 mm, towards margin, deliquescing; odor not distinctive; taste, mild.
Gills free, remote at maturity, crowded, up to 7.0 mm broad, pallid in youth, then pinkish, minutely fringed with a hand lens, finally blackish; lamellulae up to four-seried with some forking.
Stipe Stipe 4.0-9.0 cm long, 6.0-10.0 mm thick, narrowed towards the apex, swollen to sub-bulbous at the base, hollow, the core with a white cottony thread in the upper portion; surface whitish, appressed-fibrillose, greyish-tan where handled, becoming greyish in age (not from spores); context also greyish at maturity, especially above, the base sheathed with a white tomentum; partial veil white, felty-floccose, inconspicuously sheathing from below, sometimes leaving partial scale-rings on the lower stipe, more commonly forming a ring usually at the stipe base
Spores 17.5-22.5 (25) x 11.0-13.5 x 9.5-11 µm, elliptical to almond-shaped in face-view, more narrowly elliptical in profile; smooth, dark-brown mounted in water, hilar appendage not conspicuous, germ pore slightly eccentric; spore print black
Solitary to clustered on horse manure and straw; fruiting year-round during moist periods; occasional.
Coprinus sterquilinus is a smaller, infrequent cousin of Coprinus comatus, the Shaggy Mane. The two species are strikingly similar and were it not for differences in substrate, could easily be confused. Coprinus sterquilinus, as noted above, grows on horse manure and straw, while Coprinus comatus, despite a common misconception, does not, occurring rather on roadsides, newly landscaped areas, grassy areas etc. Besides size, Coprinus sterquilinus also differs in having a slightly less scaly cap, a stipe surface and context that becomes greyish with age, and spores that are distinctly larger with an eccentric rather than central germ pore. Coprinus calyptratus is also similar, especially at maturity, but has a thick, star-shaped universal veil patch on the cap disc and grows in sandy soils.