Agaricus deserticola, commonly known as the gasteroid agaricus, is a species of fungus in the family Agaricaceae. Found only in southwestern and western North America, A. deserticola is adapted for growth in dry or semi-arid habitats. The fruit bodies are secotioid, meaning the spores are not forcibly discharged, and the cap does not fully expand. Unlike other Agaricus species, A. deserticola does not develop true gills, but rather a convoluted and networked system of spore-producing tissue called a gleba. When the partial veil breaks or pulls away from the stem or the cap splits radially, the blackish-brown gleba is exposed, which allows the spores to be dispersed.
The fruit bodies can reach heights of 18 cm (7.1 in) tall with caps that are up to 7.5 cm (3.0 in) wide. The tough woody stems are 1–2 cm (0.4–0.8 in) wide, thickening towards the base. Fruit bodies grow singly or scattered on the ground in fields, grasslands, or arid ecosystems. Other mushrooms with which A. deserticola might be confused include the desert fungus species Podaxis pistillaris and Montagnea arenaria. The edibility of Agaricus deserticola mushrooms is not known definitively. Formerly named Longula texensis (among several other synonyms), the fungus was transferred to the genus Agaricus in 2004 after molecular analysis showed it to be closely related to species in that genus. In 2010, its specific epithet was changed to deserticola after it was discovered that the name Agaricus texensis was illegitimate, having been previously published for a different species.