A revision of corticolous Mazosia specimens showed that four species are present, all differing from the foliicolous taxa in the genus. One of them is widely distributed in the tropics and the others are, as far as is known, neotropical. Three species are co-occurring in NE Brazil. They can be distinguished as follows: M. leptosticta (Nyl.) Sparrius has longer ascospores (22–35×4–7 µm) than the other species, M. endonigra A. A. Menezes, M. Cáceres & Aptroot sp. nov. has sessile apothecia on a smooth thallus and occasionally also sessile pycnidia, M. carnea (Eckfeldt) Aptroot & M. Cáceres comb. nov. has immersed apothecia and a smooth thallus, and M. viridescens (Fée) Aptroot & M. Cáceres comb. nov. has distinct verrucae on the thallus. Descriptions are given and an identification key is presented to all Mazosia species with 3-septate ascospores, which includes all corticolous species known so far.
