Allocalicium

Allocalicium is a single-species fungal genus in the family Caliciaceae. It is monotypic, containing the single pin lichen species Allocalicium adaequatum. This lichen occurs in North America, South America, Europe, and the Russian Far East, where it grows on branches and twigs of deciduous trees and shrubs, typically those of alder and poplar. The species was originally described in 1869 as a member of Calicium, but molecular phylogenetics analysis demonstrated it was not a member of that genus and so Allocalicium was created to contain it.

Allocalicium is characterised by a thallus that grows predominantly under the surface of its bark substrate, though variations exist. Its characteristic structures include olive-brown stalked ascomata, dark brown apothecia (fruiting bodies) measuring 0.4–0.7 mm, and spores with unique spiral ridges formed by the uneven rupture of the outer spore wall. The photobiont partner of the lichen is from the green algal genus Trebouxia.