A number of potentially poisonous mushrooms are superficially similar but do not match all the key characteristics. The less common Coprinopsis romagnesiana
differs in that the cap is covered with darker brown appressed scales and lacks granules when young. It interacts with alcohol in a similar way to Coprinopsis atramentaria
. Coprinellus domesticus
and Coprinellus radians
, of unknown edibility, differ in that the young cap is dotted with whitish scales and the fungus forms a mat of orange hair-like fibers on the decaying log that it grows from. The less common Coprinellus flocculosus
, of unknown edibility, differs in that the young cap is covered with tufts of whitish, felty warts. The edible Coprinellus disseminatus
differs in that it is smaller (under 2 cm broad), lacks granules on the cap, and does not become inky when old.