According to Kerrigan (Agaricus of North America) A. reducibulbus has occasionally been misidentified as A. abruptibulbus. My initial impression here was abruptibulbus (because in the past I had often applied this name to the aromatic woodland type with the small abrupt basal bulb). But the innately fibrous cap surface points toward reducibulbus, as does the slight yellow staining on the bulb (difficult to detect in the photos).