[5] Hypochnus sanguineus (Sw.) Kuntze[6] Thelephora sanguinea Sw.[7] Cryptothecia rubrocincta is a species of lichen in the fungal family Arthoniaceae.

The species is distributed in subtropical and tropical locations throughout the southeastern United States, as well as Central and South America, and has been collected infrequently in a few locales in Africa.

The body of the lichen forms continuous, circular crust-like patches on dead wood, readily recognizable by the prominent red pigment.

Moving outwards from the center, zones of color may be distinguished, the first gray-green, the second white, and finally a bright red cottony rim.

The red pigment, called chiodectonic acid, is one of several chemicals the lichen produces to help tolerate inhospitable growing conditions.

The International Code of Botanical Nomenclature states that names of fungi adopted by Fries in Systema Mycologicum vols.

[15] From the center outwards, three color zones can be differentiated in mature specimens; the first grayish-green, the second white, and finally a bright red cottony rim.

[18] The lichen has a distinct prothallus—fibers of whitish fungal hyphae at the edge that lack photobiont, and which project beyond the thallus onto the growing surface.

[20][26] It is rarer in Africa, having only been collected from three geographically widely separated mountain regions: São Tomé and Príncipe, Tanzania, and DR Congo.

[15] The lichen typically grows on rough bark in sheltered and shaded habitats in moist and dense subtropical forests.

The white crystalline zone contains calcium oxalate dihydrate, or weddellite, a chemical substance found in other lichens and extremophiles growing on calcium-rich surfaces.

[28] Because the lichen grows on calcium-poor surfaces, calcium ions are thought to be acquired from rain, bird droppings, and airborne particles.

[18] The elliptical brown-colored flecks, which can be observed in both the red and pink zones of the thallus, are made of confluentic acid and calcium oxalate monohydrate.

The monohydrate is thought to be a more chemically stable metabolic byproduct of calcium oxalate dihydrate; the function of confluentic acid in the brown flecks is unclear.