A wood-rotting fungus, that grows over the undersides of fallen dead branches that have lost their bark, a growth habit called coticioid. The "mushroom" consists of a thin yellow undercrust of fungal hyphae on the surface (the subiculum, see below). Coating most of the yellow subiculum is a red layer of spore-bearing structures. Since the fungus grows on the undersides of the branches, the spores fall downwards to the soil. Hiding under the branches allows the mushroom to stay moist and fertile for a long period of time. Coccineo- means scarlet and -fulva means yellow, so this fungus is aptly named.

Supposedly found throughout North America, but rarely seen because it hides under dead branches. In Wildwood, known from the floodplain of Connelly's Run just north of the South bridge, an area rich in fallen wood and hence rich in wood-devouring fungi.

Unmistakable, if you find it. If you search under fallen branches for it, you may find other colorful corticioids like Cobalt Crust (Pulcherricium caeruleum) and Reddish Brown Crust (Hymenochaete tabacina), as well as Red and Yellow Crust's cousin, Wrinkled Crust (Phlebia radiata). Another cousin, Coral-Pink Merulius (Phlebia incarnata) looks like a small, hot pink shelf fungus.