The Andean genus Xenophyllum (Compositae, Senecioneae) is distributed along the high-Andes from northeastern Colombia to northern Chile and northwestern Argentina, mainly thriving in the paramo and puna ecoregions. It comprises suffruticose plants forming dense mats, hummocks, or clumps of erect stems. They are characterized by displaying involucral bracts fused at the base, supplementary bracts absent, and mostly radiate capitula with white ray corollas, seldom yellow or pink (disciform in one species). Traditionally, Xenophyllum species were treated as members of the genus Werneria, a morphologically close genus that includes rosettiform or scapiform perennial herbs. As currently circumscribed, Xenophyllum mostly differs from Werneria in having elongate stems. Herein, the first modern and comprehensive revision of the genus recognizing twenty-two species and two subspecies is presented. Werneria decumbens is synonymized with X. weddellii, as well as X. fontii with X. humile and X. oscartovarii with X. dactylophyllum. Likewise, four varietal names and two sectional names are proposed as new synonyms. Seven names are lectotypified, the name X. sotarense is epitypified, W. decumbens neotypified, and the supraspecific name W. sect. Integrifoliae Rockh. is typified. The combination X. crassum subsp. orientalecomb. nov. is made. Descriptions and distribution maps are provided for all accepted species, in addition to an identification key. Ten species are illustrated, three of them for the first time.
