Myeloconis parva is a species of corticolous (bark-dwelling), crustose lichen in the family Porinaceae. Found in Amazonian Brazil, it was formally described as a new species in 1996 by Patrick M. McCarthy and John Elix.
Myeloconis parva has a thallus that is grayish or greenish-brown, and can grow up to or more wide. The thallus is continuous, with a matte to slightly glossy surface that is closely appressed or somewhat raised near the margin. Closer to the centre, the thallus is raised, peeling and flaking, and very uneven, and is approximately 30âÂÂ100 üm thick. The lichen has no , but has an uppermost layer that is amorphous and 6âÂÂ10 üm thick. The algal cells are 5âÂÂ12 by 5âÂÂ10 üm, and the medulla contains masses of sulphur-yellow crystals that are sometimes exposed. When treated with K, the crystals turn reddish, but they do not fluoresce under UV light. The hyphae are 2âÂÂ3 üm wide, and the is thin, dark brown to almost black.
Ascomata are very uncommon in Myeloconis parva, and are mostly immature. They are almost entirely immersed in the thallus and have an outwardly inconspicuous appearance. The ascomata are irregularly convex thalline swellings, each with a shallow, 70âÂÂ100 üm diameter, apical depression and a minute, medium to dark brown ostiole. The ascomatal wall is dark olive-brown to almost black, 50âÂÂ90 üm thick near the apex, and 40âÂÂ60 üm thick at the base. The is pale to medium brown and is approximately 20 üm thick. The is spherical and is 0.2âÂÂ0.4 mm in diameter, while the filaments are 0.7âÂÂ1 üm thick. Mature asci have not been observed. The ascospores are to elongate-fusiform and are irregularly massed or in the asci. They have 21âÂÂ26 transverse divisions, with each loculus having 1 or 2 (sometimes 3) longitudinal or diagonal divisions. The ascospores have a 2âÂÂ3 üm-thick wall and are 94âÂÂ132 by 18âÂÂ23 üm in size.