Polymeridium neuwirthii is a species of corticolous (bark-dwelling) lichen in the family Trypetheliaceae. Found in Venezuela, it was formally described as a new species in 2014 by Dutch lichenologist André Aptroot. This lichen has a pinkish-grey thallus that does not fluoresce under ultraviolet light. P. neuwirthii is similar to Polymeridium quinqueseptatum but can be differentiated by its with large oil droplets and consistently 7-septate, rough . The ascomata are 0.4âÂÂ0.6 mm in diameter, with a spherical that is and solitary. The ostiole is apical, and the contains large oil droplets. There are eight ascospores per ascus, which are iodine-negative, 7-septate, and measure 30âÂÂ33 by 9âÂÂ10 üm. The ascospore wall is roughly ornamented. No chemical substances have been detected in this lichen. The type specimen was collected in Puerto Ayacucho, Venezuela, on a twig of a shrub. The species is named in honour of the collector of the type and only specimen, Gerhard Neuwirth.