abruptly-bulbous agaricus or the flat-bulb mushroom - klompvoetchampignon (dutch)

Some American authors consider this species to be synonymous with A. silvicola, while some in Europe have synonymized it with the similar species A. essettei. American mycologists Steve Trudell and Joseph Ammirati noted in a 2009 field guide: "The name A. abruptibulbus has been applied to forms with bulbous stipe bases, but variation in stipe shape is so great that the use of this name has been largely abandoned.