Corticioid

Corticioid refers to a growth form rather than a single taxonomic group, describing fungi that produce crust-like, resupinate fruiting bodies that lie flat on their substrate, usually wood. These crusts lack a distinct cap and stem and spread over the surface as a thin to moderately thick layer. The surface can be smooth, zonate, or rough, and the underside carries the hymenium where spores are produced; the underside texture may be pore-bearing, smooth, or occasionally slightly tooth-like depending on the species.

Corticioid fungi are predominantly saprotrophs, playing a major role in the decomposition of wood and the cycling of nutrients in forest ecosystems. They are widespread in temperate and tropical forests and can be found on fallen branches, logs, and stumps, as well as occasionally on living trees as pathogens or weak parasites. Morphologically, corticioid species occur across multiple taxonomic lineages within the Agaricomycetes, and the term is used to describe a form rather than to denote a single evolutionary group. Molecular studies have shown that corticioid growth has evolved independently in diverse clades, leading to a wide distribution of corticioid species in different orders and families.

Because corticioid fungi encompass a broad and heterogeneous set of taxa, identification often relies on microscopic features such as spore shape and size, basidia, and other microscopic characters, alongside macro-morphology. They are of interest for studies of wood decay processes, lignocellulose degradation, and forest ecology, and some species are examined for enzymatic properties useful in biotechnology.