The following 16 new species of Trypetheliaceae are described from Brazil: Astrothelium aeneoides Aptroot, differing from A. aeneum by the absence of pigment on the thallus, but medulla of pseudostroma K+ blood red and ascospores 3-septate, lumina diamond-shaped; A. curvatum Aptroot & M. Cáceres with immersed pyriform ascomata with lateral ostioles and bent, muriform ascospores, 74–90×25–34 μm; A. globosum Aptroot & M. Cáceres with immersed ascomata, thallus consisting of nearly globose warts and ascospores 3-septate, 35–40×11–13 μm; A. graphicum Aptroot & S. M. A. Martins with an extended, reticulate pseudostroma, which is lower than the slightly bullate thallus, orange pruina on the thallus and pseudostroma and ascospores muriform, 60–66×12–16 µm; A. longisporum Aptroot, J. R. Silva & M. Cáceres, which differs from A. megaspermum by the eccentric ostioles and the 8 instead of 4 ascospores per ascus; A. macrostomum Aptroot which is similar to A. eustomum (Mont.) Müll. Arg., but differing by the 5–7-septate ascospores 65–85×16–19 μm.; A. megeustomum Aptroot & Fraga Júnior which is similar to Astrothelium eustomum, but with muriform ascospores 117–125×17–21 μm; A. pictum Aptroot with 5-septate ascospores, red crystals in the pseudostroma medulla and lichexanthone in the thallus; A. rubrocrystallinum Aptroot & M. Cáceres which is similar to A. annulare, but with copious red crystals in a thick layer around the ascomata and ascospores 22–27×7–9 μm; A. simplex Aptroot & S. M. A. Martins with 3-septate ascospores and a very rough thallus, differing from A. sinuosum by the lack of lichexanthone; A. sinuosum Aptroot & Gumboski with an ostiolar UV+ yellow reaction, bullate thallus and a wavy gelatinous sheath around the ascospores; A. tetrasporum Aptroot & M. Cáceres which is similar to A. puiggarii, but differs by the non-inspersed hamathecium and the ascus that contains only 4 ascospores; Polymeridium endoflavens Aptroot, D. S. Andrade & M. Cáceres with yellow oil inspersion in the hamathecium and 5–7-septate ascospores 32–37×10–13 μm; P. longiflavens Aptroot, Mendonça & M. Cáceres with yellow oil inspersion in the hamathecium, an apical ostiole and 9–11-septate ascospores 57–70×12–14 μm; Trypethelium luteolucidum Aptroot, Mendonça & M. Cáceres which is similar to T. regnellii, but differs by the presence of anthraquinone crystals in the pseudostromata; and Viridothelium leptoseptatum Aptroot & M. Cáceres, resembling Astrothelium aeneum but with no pigment on the thallus, a thin to absent thallus cover on the ascomata and thin-walled, constricted ascospores with lumina of a similar shape to the ascospore cell walls. Most are known only from Brazil, but a few are also known from Mexico, Puerto Rico, and/or Guyana. North-eastern Brazil is the centre of diversity of the genus Polymeridium, with 33 species now known.