The Arthoniales is the second largest order of mainly crustose lichens, but fruticose lichens are present as well. The order contains around 1500 species, while the largest order with lichenized fungi, the Lecanorales, contains more than 14000 species.
Cryptothecia is a genus of white to greenish crustose lichens that grow on bark, wood, or leaves, in tropical or subtropical areas worldwide. It has a conspicuous prothallus that develops around its periphery which can be bright red in some species, hence the common name wreath lichen. The main vegetative body (thallus) lacks a cortex (ecorticate and is often immersed in the substrate or byssoid. The medulla is white, well defined, and often peppered with calcium oxalate crystals. Ascomata are not well defined, being cushions of soft white mycelium immersed in the medullary tissue, hence the name from the Greek krypto = "to conceal" and theke = "a container or sheath". It contains Trentepohlia, a green alga, as its photobiont partner.
Roccella is a genus of 23 species of lichens in the family Roccellaceae. The genus was circumscribed by Swiss botanist Augustin Pyramus de Candolle in 1805, with Roccella fuciformis as the type species.
The Trypetheliaceae are a family of mainly lichen-forming fungi in the order Trypetheliales. The family consists almost exclusively of corticolous (bark-dwelling), crustose lichens with an almost strictly tropical distribution.
Herpothallon is a genus of crustose lichens in the family Arthoniaceae. It has about 50 species.
Pyrenidium is a genus of lichenicolous (lichen-dwelling) fungi. It is the only genus in the family Pyrenidiaceae. It has 13 species.
Astrothelium bivelum is a species of corticolous (bark-dwelling), crustose lichen in the family Trypetheliaceae. Found in Brazil, it was formally described as a new species in 2016 by lichenologists André Aptroot and Marcela Cáceres. The type specimen was collected by the authors in the Parque Natural Municipal de Porto Velho, in a primary rainforest. The lichen has a smooth and somewhat shiny, ochraceous-green thallus with a 0.4 cm-wide rough and irregular prothallus; the thallus covers areas of up to 3 cm (1.2 in) in diameter. The presence of the lichen does not induce the formation of galls in the host. The ascomata are pear-shaped (pyriform), measure 0.5–0.7 mm in diameter, typically aggregate in groups of two to six, and are usually immersed in the bark tissue. The characteristics that distinguish it from other members of Astrothelium include the diffusely pseudostromatic, erumpent ascomata that are covered by thallus and have an external pink pigment, with each containing a single group of fused ascomata; and the 5-septate ascospores. A. bivelum is one of the few Astrothelium-like species with 5-septate ascospores that does not contain lichexanthone.
Astrothelium eustomurale is a species of corticolous (bark-dwelling), crustose lichen in the family Trypetheliaceae. Found in Brazil, it was formally described as a new species in 2016 by lichenologists André Aptroot and Marcela Cáceres. The type specimen was collected by the authors in the Parque Natural Municipal de Porto Velho, in a low-altitude primary rainforest. The lichen has a smooth and somewhat shiny, pale yellowish-grey thallus that lacks a prothallus and covers areas of up to 12 cm (4.7 in) in diameter. The presence of the lichen does not induce the formation of galls in the host. The ascomata are pear-shaped (pyriform) and typically occur in aggregates of two to five, usually immersed in the bark tissue under the pseudostromata and with a whitish-coloured tissue that contrasts with the surrounding thallus. Black pycnidia are abundant on the pseudostromata. The area around and including the ostiole of the ascomata contains lichexanthone, a lichen product that causes these areas to glow yellow when lit with a long-wavelength UV light. The characteristics that distinguish it from other members of Astrothelium include the UV+ yellow nature of the ostiole; and the fused, erumpent pseudostromatic ascomata that have a white cover contrasting it with the thallus colour.
Architrypethelium hyalinum is a species of corticolous (bark-dwelling), crustose lichen in the family Trypetheliaceae. Found in Costa Rica and Brazil, it was formally described as a new species in 2008 by lichenologist André Aptroot. The type specimen was collected by Harrie Sipman from the Las Cruces Biological Station in Puntarenas. The lichen has a smooth to uneven, olive-green thallus. Its ascomata occur solitarily, have an apical ostiole, and measure 0.7–1.5 mm in diameter. Ascospores number 4 to 8 per ascus, have an oblong to ellipsoid shape with 3 septa, and measure 100–150 by 30–50 μm. These spores are among the largest of the 3-septate lichens in the Trypetheliaceae. Both the thallus and ascomata contain lichexanthone, a lichen product that causes these structures to glow yellow when lit with a long-wavelength UV light; A. hyalinum is the only species in genus Architrypethelium that contains lichexanthone.
Astrothelium fijiense is a species of corticolous (bark-dwelling), crustose lichen in the family Trypetheliaceae. Found in Fiji, it was formally described as a new species in 2016 by Robert Lücking, Khwanruan Naksuwankul, and Helge Thorsten Lumbsch. The type specimen was collected from Nakoba Levu at an altitude of 750 m (2,460 ft); there, it was found growing on bark on a steep slope in a secondary forest. The lichen has a smooth to uneven, light olive-yellow thallus that covers areas of up to 5 cm (2 in) in diameter. Both the thallus and the pseudostromata contain lichexanthone, a lichen product that causes these structures to fluoresce a yellow colour when lit with a long-wavelength UV light. The species epithet fijiense refers to the type locality. The characteristics of the lichen that distinguish it from others in genus Astrothelium are the distinctly pseudostromatic ascomata, and the presence of lichexanthone on the pseudostromata. Astrothelium cinereorosellum is somewhat similar, but that species has slightly longer ascospores and does not have lichexanthone on the pseudostromata.
Vigneronia is a genus of lichen-forming fungi in the family Roccellaceae. It has five species. The genus was circumscribed in 2014 by Damien Ernst, with Vigneronia spieri assigned as the type species. This species, originally described as Schismatomma spieri from collections made in the Galápagos Islands, has since been recorded from mainland Ecuador and the Antilles (Curaçao). The genus is named after Ernst's wife, Nathalie Vigneron, who accompanied him on collecting trips.
Vigneronia spieri is a species of corticolous (bark-dwelling), crustose lichen in the family Roccellaceae. It is found in the Galápagos Islands, mainland Ecuador and the Antilles (Curaçao).
Enterographa rotundata is a species of corticolous (bark-dwelling) crustose lichen in the family Roccellaceae. This species was discovered in Brazil, growing on the smooth bark of trees in the Brazilian Caatinga forest. It has round apothecia, a feature that sets it apart from most of its kind.
Neosergipea is a genus of lichen-forming fungi in the family Roccellaceae. It has four species, all of which are corticolous (bark-dwelling), crustose lichens that are found in the tropical forests of Brazil. This genus is related to the genera Dichosporidium, Enterographa, and Erythrodecton. It distinguishes itself through unique morphological characteristics and certain chemical constituents, in particular, its non-carbonised ascomata and the presence of a vivid orange anthraquinone compound.
Neosergipea bicolor is a rare species of corticolous (bark-dwelling), crustose lichen in the family Arthoniaceae. Found only in Brazil and described as a new species in 2017, Neosergipea bicolor is characterised its dual-coloured appearance.
Neosergipea hyphosa is a species of corticolous (bark-dwelling) lichen in the family Roccellaceae. This lichen species is uniquely characterised by its olive-green thallus—a type of vegetative tissue—and spherical ascomata, or fungal reproductive structures. It is most commonly found on tree bark in Brazil. The name hyphosa alludes to the distinct hyphose surface of the thallus.
Opegrapha ramisorediata is a rare species of corticolous (bark-dwelling), crustose lichen in the family Opegraphaceae. Known to occur only in northeastern Brazil, it was described as a new species in 2017. It is characterised by a thin, pale greenish-mauve thallus.
Megalotremis is a genus of lichen-forming fungi in the family Monoblastiaceae. It has 16 species. The genus was circumscribed by Dutch lichenologist André Aptroot in 1991, with Megalotremis verrucosa assigned as the type species. Megalotremis is a pyrenolichen genus, meaning its species have perithecioid ascocarps: spherical or flask-shaped, sessile or partly immersed in the thallus, with a single opening (ostiole) and enclosed by a distinct wall.
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 lirellate ascomata.
Byssoloma xanthonicum is a species of corticolous (bark-dwelling), crustose lichen in the family Pilocarpaceae. It is found in New Caledonia.
