The foliicolous lichen flora of Mexico IV: a new, foliicolous species of Pyrenothrix (Chaetothyriales: Pyrenothrichaceae).

Pyrenothrix mexicana Herrera-Campos, Huhndorf & Lücking spec. nova is described from leaves in the upper montane rainforest of Oaxaca State, Mexico. It is the second species in the genus Pyrenothrix Riddle, established at the beginning of the twentieth century for the single species, P. nigra Riddle, a corticolous lichen restricted to southeastern United States. Both taxa have the same thallus and perithecial morphology and anatomy, but P. mexicana differs by its longer, transversally septate ascospores. The perithecial anatomy of Pyrenothrix is documented and its systematic affinities are discussed, and we conclude that the family Pyrenothrichaceae Zahlbr. should be placed in the order Chaetothyriales.