Hi Allelopath, If I saw something like this in my region I would think Pholiota genus, then start narrowing it down. Do you have a field guide for your region to consult? If so I'd check into the local Pholiota species possibilities. It may help to know whether growing from hardwood or conifer, and to have a good sense of the top of the cap ornamentation, whether the stem is smooth or not, whether either cap or stem is slimy and so forth. cheers, frog
Yes, I have a guides. I see Pholiota squarossa often enough, but this is not that. Having identified the genus, it may be P. mutabilis, a photo of which is not the local book (Mushrooms of Colorado and the Southern Rocky Mountains). As mentioned in the photo description, it is growing on spruce. Not slimy.