The habitat was unusual for A. abruptibulbus... in needle duff under a Blue Spruce tree on a lawn. Only slight yellow staining of some parts; yellow flush on caps. Young button growing with the others. Note the very pale gill color of this fruit body. Left another identical button which matured very quickly (much rainfall), and it ended up looking exactly like the mature specimens seen here. So I'd say these are all the same species. The young specimen lacked the small abrupt basal bulb. Perhaps this feature develops as the mushroom matures?