[1] Found in Brazil, this species is distinguished by its eccentric (not centrally positioned) red ostioles (the openings of the fruiting bodies).

[2] The type specimen of Pyrenula rubrolateralis was collected from Mata do Crasto in Santa Luzia do Itanhy, Sergipe, Brazil, at an elevation of approximately 10 m (33 ft).

The ascospores are brown, irregularly biseriate (arranged in two rows), with mostly rounded to somewhat diamond-shaped internal cavities separated from the wall by a thick layer.

Chemically, the ostioles do not react with potassium hydroxide (K–), the thallus does not fluoresce under ultraviolet light, and no substances were detected using thin-layer chromatography.

It is similar to the North American species Pyrenula wetmorei, which differs by having an inspersed hamathecium (containing oil droplets) and ascospores with black pigment bands that obscure the septa.