Growing on a well desiccated although I haven't seen anything here it looks like it's a birch.
on well-rotted hardwood, presumably oak https://www.mushroomexpert.com/callistosporium_purpureomarginatum.html
Both the new anamorph (asexual) stage and last year’s teleomorph can be seen on this seed pod of the American sweetgum (Liquidambar styraciflua). In the anamorph stage, the tentacle-like fruiting bodies are covered with a light gray/white layer of asexual spores (conidia). Eventually the white/gray conidia layer will disappear and the fruiting bodies will turn into black strands.
Found in leaf litter, on an old, decaying seedpod of the American sweetgum (Liquidambar styraciflua).