On a quick visit on a sunny Christmas Day I was pleased and surprised to find several groups of the shining ink cap (Coprinus micaceus).
Although it often comes up in grassy places it is a species that grows on decaying, often buried, wood.
The species is sometimes said to be edible and is not poisonous as such. Like other members of the genus it does, however, have an adverse effect if eaten in combination with alcohol and is therefore best avoided. It is small and hardly worth it anyway.