I just spotted these in my backyard. It seems like they popped up overnight. I have no clue what kind they are.
You wouldn't know it from the picture, but the spot where they are growing is where the previous owner buried his dog right before I took over. Nothing grew in that area for the first year, which was surprising because every other part of the property is constantly being taken over by various weeds and
volunteer plants (My neighbor says it is because the dog was evil.). I like to think the mushrooms are a good sign that the soil there is bouncing back from the dry, cracked earth it was when I moved in.