Coniocarpon is a genus of lichen-forming fungi in the family Arthoniaceae. It has eight species of corticolous (bark-dwelling) lichens. This genus is distinct for its crystalline orange, red, and purple quinoid pigments in the ascomata that turn purple in potassium hydroxide solution, its colourless, transversely septate ascospores with large apical cells, and its rounded to ascomata (fruiting bodies).
The genus was circumscribed by Augustin Pyramus de Candolle in 1805. The genus was rejected against Arthonia as proposed in the International Code of Nomenclature for algae, fungi, and plants in Appendices I–VII. In 2014 however, Coniocarpon was resurrected by Andreas Frisch and colleagues for the Arthonia cinnabarina species complex, based on the results of molecular phylogenetics analysis, which showed that it formed a clade with the genus Reichlingia. The type species of the genus, Coniocarpon cinnabarinum, had previously been designated by Rolf Santesson in 1952.
The genus Coniocarpon, as revitalized by Frisch and colleagues in 2014, comprises lichens with a smooth thallus that is either immersed or slightly protruding, typically pale brown and often outlined by a dark line. Its is of the type. The apothecia (fruiting bodies) of these lichens are irregularly rounded to weakly lobed, either or, and emerge singly or in clusters. The is brown, consisting of compressed, vertically aligned hyphae, which sometimes form short hairs on the outer margin and may have old bark cells attached.
The of the apothecia is dark, ranging from flat to slightly convex, and may have a white surface, sometimes overlaid with an orange-red, with margins that are level with the disc and may also be prominently orange-red pruinose, containing crystals. The is brown, composed of branched tips of paraphysoidal hyphae that extend horizontally above the asci. The hymenium is colourless and strongly, with a of densely branched and netted . The is also colourless.
The asci of Coniocarpon are of the Arthonia-type, to in shape, and typically contain eight spores. Its are colourless, with an enlarged apical cell, turning pale brown with granular ornamentation at maturity. Chemically, the exciple and epithecium react blue upon staining with solutions of iodine and potassium iodide, while the hymenium and hypothecium react red with iodine and blue with potassium iodide. The orange-red crystals dissolve in potassium hydroxide solution to form a transient, purplish solution.