Dictydiaethalium plumbeum a Slime Mould
The specific name means “lead” after its grey form. The ones I found were brown.
I have never found the mature (spore-producing) form of this species before although I have seen plasmodium a couple of times.
This fruiting body for this species is referred to variously as a pseudoaethalium or aethalium.
These were about thumbnail size but they can measure 10cm.
They were scattered across a rotting tree branch on the ground.
The asexual plasmodium is shown in the last image.
Olympus EM-1, (aperture priority), Olympus m4/3 30mm f3.5 ED macro, f8 ISO 2000, hand-held.