The following 24 new species of Trypetheliaceae are described after three weeks of fieldwork in an area with a radius of 50 km around Porto Velho in Rondônia: Astrothelium bivelum with astrothelioid ascomata, 5-septate ascospores with polar gelatinous caps, and a thallus without lichexanthone; A. curvisporum with bent, 5-septate ascospores of 115–135 × 29–36 μm with a 17–22 μm thick gelatinous layer; A. decemseptatum with pseudostroma that are essentially black and look like breaking through the bark, with anthraquinones mostly on the pseudostromata but also on some parts of the thallus, best seen under UV light as the colour of the pruina is not very strong, and ascospores (7–)9–11-septate, fusiform, 50–65 × 11–17 μm; A. disjunctum with black pseudostroma and ascospores 3-septate, (27–)29–33 × (8–) 12–14 μm; A. duplicatum which is similar to A. mesoduplex, but pseudostroma are only yellowish inside and ascospores 45–55 × 11–15 μm; A. eumultiseptatum which is similar to A. eustomum, but with 9–11-septate ascospores of 65–70×15–17μm; A. eustomurale which is also similar to A. eustomum, but with submuriform ascospores of 37–45 × 15–19 μm; A. flavoduplex which is similar to A. mesoduplex, but with ascospores 110–350 × 20–27 μm and the thallus containing lichexanthone; A. flavomurisporum with deeply immersed ascomata with muriform ascospores of 165–200 × 28–35 μm, with a distinctly thickened central septum and yellow oil; A. flavostromatum which is close to A. aeneoides and mainly differs by the bullate thallus and the cream pseudostromata; A. flavum which is similar to A. aeneum, but differs in the contrast between the linear to reticulate yellow stromata and the unpigmented thallus, and the ascospores of 16–18 × 6–7 μm; A. mesoduplex which is similar to A. flavoduplex, but with ascospores 90–100 × 20–23 μm and a thallus without lichexanthone; A. nigrum with mostly conical black pseudostromata that contrast sharply with the thallus, superficially resembling Pyrenula infraleucotrypa; A. novemseptatum which is similar to A. eumultiseptatum, but without lichexanthone anywhere in the thallus or pseudostroma; A. ochroleucoides which is similar to A. corallinum, but with lichexanthone on the thallus and pseudostromata; A. octoseptatum which is similar to A. eumultiseptatum, but with the whole pseudostroma, not just the ostioles, containing lichexanthone, and ascospores somewhat asymmetrical, which is highlighted by the unusual dominant even number of septa (eight) and the asymmetrically placed central septum in the case of uneven septum numbers; A. quatuorseptatum which is similar to A. octoseptatum Aptroot & M. Cáceres, but without lichexanthone, ascospores somewhat asymmetrical, which is highlighted by the unusual dominant even number of septa (four) and the asymmetrically placed central septum in the case of uneven septum numbers; A. robustosporum with solitary ascomata with an eccentric ostiole, and ascospores 11–15-septate, 90–125 × 20–27 μm; A. solitarium which is similar to A. ceratinum (Fée) Aptroot & Lücking, but with ascospores 33–36×10–11μm; A. stromatofluorescens which is close to A. phlyctaena, but with lichexanthone only on the pseudostroma, not on the thallus; A. supraclandestinum is close to A. subclandestinum, but the hamathecium is not inspersed; A. testudineum with solitary ascomata with an eccentric ostiole, an inspersed hamathecium, and ascospores 8 per ascus, muriform, 50–65 × 23–27 μm; A. xanthosuperbum which is similar to A. disjunctum, but with muriform ascospores, 130–160 × 28–35 μm; and Pseudopyrenula flavoreagens which is similar to P. subgregaria, but with lichexanthone in the thallus. Only a few species were also found elsewhere, such as other areas of Brazil, or in Venezuela, Colombia, Guyana, Panama, Australia and/or Papua New Guinea. Currently, 55 species of Trypetheliaceae are known from this spot, including 46 species of Astrothelium. The Amazon basin is the centre of diversity for the family, at least for Astrothelium, the largest genus in the family. Keywords: Australia, Colombia, Guyana, lichens, Panama, Papua New Guinea, Pseudopyrenula, Venezuela.