Hypotrachyna angustissima is a species of foliose lichen in the family Parmeliaceae.Marcelli, M. P., and Celio Henrique Ribeiro. "Twenty-one new species of Parmeliaceae (lichenized fungi) from southeastern Brazil." Mitt. Inst. Allg. Bot. Hamburg 30.32 (2002): 125–155. This species is characterised by the occurrence of usnic acid in its cortex, and salazinic acid in its medulla and laminal isidia. In this it resembles Hypotrachyna microblasta, but the latter has wider laciniae and larger apothecia, and is laterally overlapping. Its epithet angustissima is derived from the Latin angusti, meaning "narrow", due to this species' very narrow laciniae.
Description It possesses a yellowish-green thallus that measures wide, its laciniae are plane and adnate. Its surface is continuous and somewhat irregularly cracked, being isodichotomously ramified. The species' axilla is oval, it counts with truncate apices, and a black-lined margin. It shows no lacinules nor soredia while showing weakly laminal maculae.
Its isidia are cylindrical with an irregular diameter, being between 0.2 and 0.8 mm high. Its medulla is white, while its underside is black, possessing a shiny and rugose, lighter margin. Its central surface is veined and papillate. Its rhizines measure between long, being coloured the same as the lower cortex and with a frequent distribution. Its apothecia is plane, with a diameter of and a crenate margin. It counts with 8 spores per ascus, which are ellipsoid. Pycnidia are absent in Hypotrachyna angustissima.
Habitat This species was first found in the Ibitipoca State Park, in Minas Gerais, on a rocky wall.
References
Further reading Holz, Ingo, and Robbert S. Gradstein. "Cryptogamic epiphytes in primary and recovering upper montane oak forests of Costa Rica–species richness, community composition and ecology." Plant Ecology 178.1 (2005): 89-109.