Based on the most recently published morphological cladistic analysis of the family Agoristenidae, the taxonomic position of an undescribed harvestman species was evaluated. According to the results of an updated phylogenetic analysis, the description of a new monotypic genus is proposed to accommodate this new species. The diagnostic characters of the new genus are: free tergites II and III with three large tubercles, and femora and tibiae of legs II–IV with longitudinal rows of conspicuous tubercles. Muscopilio onod gen. et sp. nov. inhabits Andean rainforests in Cundinamarca department, Central Colombia. Remarkably, almost all individuals collected in the field had at least three families of bryophytes, including mosses (Leucomiaceae) and liverworts (Plagiochilaceae, Lejeuneaceae), growing on their legs, and suggesting a mutualistic relationship between epizoic organisms and harvestmen.