Trichothelium longisetum sp. nov. (Porinaceae) is described from a rainforest in northeastern Ecuador. It has a non-radiating photobiont, prominent, black perithecia, each with numerous, long-acute to acicular, black setae, and elongate-bacilliform, 9–15-septate ascospores. Remarkably, this lichen grows on wood rather than on the living leaves or bark of trees or shrubs. Four species of Porina are also reported for the first time from Ecuador.