Mazosia flavida

The thallus is a continuous, crustose film with a cortex, dull olive-green in color, up to about 1 cm (0.4 in) in diameter and less than 0.05 mm thick. It is not surrounded by a prothallus. It has yellowish dots that are ellipsoid and radially arranged, about 0.05 × 0.025 mm in size and spaced roughly 0.1 mm apart. The medulla of these dots is pale yellow. The photobiont is trentepohlioid (a Trentepohlia-type green alga). The ascomata (fruiting bodies) are solitary and sit on the surface of the thallus, with an unconstricted base. They are round, 0.3–0.5 mm wide and up to 0.2 mm high, with a dark gray, flat disc and a thin white, powdery (pruinose) coating, and a yellowish margin raised above the disc and about 0.1 mm wide. The excipulum is pale yellow, the hypothecium dark brown, and the hamathecium is not inspersed and shows no reaction in the IKI test (IKI–). Each ascus contains eight ascospores. The spores are hyaline (colorless), cylindrical, and 9-septate, 46–52 × 3.5–4.5 μm, and soon fragment, without any surrounding gelatinous sheath. Pycnidia have not been observed. Standard spot tests were negative (UV–, C–, K–, KC–, P–) and thin-layer chromatography was not performed because of the limited material. Based on the yellow color and the lack of a K reaction, the pigment is thought to be an emodin-derived anthraquinone.^[2]

Mazosia flavida grows on living leaves in primary rainforest in the Reserva Cristalino region of Mato Grosso, Brazil, at elevations of about 250 to 350 m (820 to 1,150 ft). It is known only from Brazil, and no additional occurrences had been reported as of 2025.^[2][3]