A crust fungus, growing as if the cap of the mushroom attached to the wood instead of by a stalk, a habit called resupinate. Starts as small, circular patches that grow and fuse to form an irregular crust. The spore-bearing surface is composed of pores which split up to form a maze of tubes and teeth. The color is white to cream to brownish.
On dead wood, usually of deciduous trees. In Wildwood common, but often ignored.
Milk white toothed polypore (Irpex lacteus) is similar, but whiter and with more pronounced teeth instead of pores.
Strangely, Schizopora paradoxa is also a song by the Wojtek Mazolewski Quintet!