Resupinatus, A Distinctive Fungus
There is more than one species but these thick, gill-like structures are characteristic. They grow on the undersides of rotting chunks of branches on the ground. This was about 5mm across.
I have had to clone out a passing springtail from one frame of the stereo pair.
Olympus EM-1 (manual mode), Laowa 25mm f2.8 2.5x-5x ultra-macro at f8, TTL flash hand-held.
I think I held a single flash gun in the hand supporting the lens.