The family Gomphillaceae is characterized by its crust-like thallus, which is the outer layer of the lichen body. These lichens contain chlorococcoid photobionts, which are symbiotic algae that help the lichen to produce food through photosynthesis. The reproductive structures of Gomphillaceae lichens, known as ascomata, can be apothecioid or lirellate in form. Apothecia occur in a few forms, including biatorine or zeorine to sometimes lecideine.
The internal structure of hymenium (the fertile, spore-producing part of the lichen), called the hamathecium, consists primarily of branched and interwoven paraphyses. The asci, or spore-producing sacs, are annelasceous and feature a distinctive apical tholus and ring structure. They can be clavate, oblong, or fusiform in shape and do not exhibit any amyloid properties. These asci typically produce eight ascospores, although some may produce fewer, ranging from one to four spores. The ascospores are hyaline (transparent), and have thin walls and distinct eusepta. They can be ellipsoid or oblong in shape, and their internal divisions (septa) can be transverse or muriform.
Gomphillaceae lichens also produce conidiomata, which are asexual reproductive structures. These are mostly hyphophores, and the conidia are formed as branched hyphae, called diahyphae, within gelatinous masses. The conidia are typically septate, often taking on a moniliform or bead-like appearance, and are also hyaline. In terms of secondary chemistry, Gomphillaceae lichens generally lack any notable substances.
According to a recent (2022) estimate, the Gomphillaceae comprise 26 genera and about 425 species. The following list indicates the genus name, the taxonomic authority, year of publication, and the number of species: