Rusty Gilled Polypore

 
Shelf or bracket fungus.

These are the gills on the under side of these polypore.

Found on a piece of fallen oak tree limb.

Dark brown and yellow in it's young stage.

Gloeophyllum sepiarium, the rusty gilled polypore, is a wood decay fungus that causes a brown rot. It grows in thin, dark brown brackets on dead trees. The fruiting body grows for only one year, and produces spores in late summer and autumn.  The rusty-gilled polypore is extremely common across North America. The gills are evident on the underside.