Twelve new lichenized species are described in Arthoniales and Ostropales from seasonally dry tropical forest in Mexico: eight in Graphidaceae, one in Gomphillaceae, and one each in Arthoniaceae, Roccellaceae, and Opegraphaceae. The new species are: Acanthothecis alba Herrera-Camp., Barcenas-Peña & Lücking, differing from A. poitaeoides in the erumpent to prominent ascomata with partially exposed disc and the relatively broader ascospores; Bactrospora lecanorina Herrera-Camp., Altamirano & Lücking, differing from the other species with patellarioides-type ascospores by the zeorine ascomata, in combination with narrow ascospores; Cryptothecia chamelensis Herrera-Camp., Bautista & Lücking, differing from C. inexpectata and C. irregularis in the perlatolic acid chemistry and the much smaller ascospores; Fissurina aperta Herrera-Camp., Barcenas-Peña & Lücking, differing from F. adscripturiens and F. novae-zelandiae by its exposed, disc and thin, erect margins; F. cinereodisca Altamirano, Colín & N.Sánchez, differing from F. furfuracea in the shorter ascomata with grey disc and thin, margin; F. jaliscoensis Herrera-Camp., Barcenas-Peña & Lücking, differing from F. subnitida in the shorter lirellae with exposed disc and thin margins; F. reticulata R. Miranda, Herrera Camp. & Lücking, differing from F. tuckermaniana by its muriform ascospores; F. tenuimarginata Herrera-Camp., Barcenas-Peña & Lücking, differing from F. cinereodisca in the smaller lirellae with yellowish-translucent disc and thinner margin; Gyalideopsis caespitosa Barcenas-Peña, Herrera-Camp. & Lücking, differing from other species of the genus in the initially zeorine apothecia and the sessile hyphophores with caespitose diahyphae; Ocellularia tomatlanensis Herrera-Camp., Colín & Lücking, differing from other Ocellularia species with small, transversely septate, hyaline ascospores and protocetraric acid by the absence of a columella; Phaeographis sarcographoides Herrera-Camp., N.Sánchez & Lücking, differing from other species of Phaeographis with inspersed hymenium, 3-septate ascospores, and lack of secondary substances, in the robust, prominent to sessile ascomata with often dissected disc; and Vigneronia mexicana Herrera-Camp., Bautista & Lücking, sp. nov., differing from V. spierii in the prominent to sessile ascomata with brown margin and light grey-pruinose disc. The new combination Vigneronia caceresiana (Kalb & Aptroot) Lücking & Herrera-Camp., comb. nov., is also proposed.