Nesolechia oxyspora is a species of lichenicolous (lichen-dwelling) fungus in the family Parmeliaceae. It was first scientifically described as a member of the genus Abrothallus by Edmond Tulasne in 1852. Abramo Bartolommeo Massalongo transferred it to Nesolechia in 1856. It has acquired about a dozen synonyms as it has been shuffled to various genera in its taxonomic history.
In 2017, Divakar and colleagues used a then-recently developed "temporal phylogenetic" approach to identify temporal bands for specific taxonomic ranks in the family Parmeliaceae, suggesting that groups of species that diverged within the time window of 29.45–32.55 million years ago represent genera. They proposed to synonymize genus Nesolechia with Punctelia (its lichen-forming sister group), because Nesolechia originated relatively recently and fell under the timeframe threshold for genus level. This proposed synonymy was not accepted in a later critical analysis of the temporal phylogenetic approach for fungal classification. Despite this, the synonym Punctelia oxyspora is still used by some sources.
The spores, measuring 14–22 by 5–7 μm, are spindle-shaped. The is chestnut brown, and the hymenium turns blue when treated with iodine (J+). The ascomata (fruiting bodies), which are 0.1–0.4 mm in size, form dense clusters. Initially, they develop inside the lichen thallus, but eventually break through the and slightly protrude. The disc starts off flat with a fine margin, then becomes slightly convex and marginless, with a dull black-brown colour.
This fungus species appears to be cosmopolitan in distribution. It is found on the thalli of various foliose (leaf-like) and fruticose (shrub-like) lichens, where it sometimes induces the formation of galls.