Cap narrowly ellipsoid to obovate, 4.0-11.0 (15) cm tall, 2.0-4.0 cm broad, not expanding, the margin fused to stipe except occasionally breaking free in senescence; surface two-layered, the outer layer cream-white, sparsely covered with flattened tan-colored scales, partially sloughing off in age, revealing a thin, brittle, glabrous cream to buff-colored inner layer, the latter eventually fissured or cracked, releasing spores; odor and taste untried.
Gills replaced by a puffball-like gleba, at first pallid to yellowish, sometimes with vinaceous tints, at maturity dark-brown, dark reddish-brown to blackish, the spore mass embedded in a capillitium.
Stipe 4.0-9.0 (12) cm long, 0.5-1.0 thick, straight, more or less equal except for a soil-encrusting, abruptly bulbous base; surface covered by a whitish to cream-colored membrane, fragmenting with age, exposing a pallid, longitudinally striate under-surface; context consisting of a woody cortex and cottony-fibrous pith, lacking the "cottony cord" seen in Coprinus comatus; partial veil absent.
Spores 10-15.0 (16.0) x 9.5-13.5 µm, globose to ovoid, smooth, with a thick double-wall, prominent germ pore, inconspicuous hilar appendage, and lacking a pedicel; spores ochre-colored when mounted in KOH, blackish in deposit.
Scattered to grouped along dry washes and roadsides of the desert regions of California; fruiting spring, summer, and fall after periods of moisture; dried fruiting bodies persisting for months; occasional to locally common.
Known as the Desert Shaggy Mane due to its resemblance to Coprinus comatus, Podaxis pistillaris has traditionally been thought to be a close relative. Although they both belong in the Agaricaceae, molecular studies suggest that they are not as close as once thought, a notion supported by their dissimilar natural histories. Podaxis pistillaris differs from Coprinus comatus with its persistent fruiting bodies and secotioid habit, i.e. a cap that typically remains closed through development, protecting the fertile tissue from dessication. Gills and forcible spore discharge are replaced by a puffball-like gleba, and the spores, which are double-walled, presumably also an adaptation to xeric conditions, are released only when cracks form in the senescent fruiting bodies. In contrast, Coprinus comatus, a moisture-loving species, produces short-lived, fleshy fruiting bodies with gills that soon deliquesce into an inky liquid, helping to liberate the single-walled spores.