Raimondo, F. M. & Domina, G.: Ptilostemon greuteri (Compositae), a new species from Sicily. — Willdenowia 36 (Special Issue): 169–175. — ISSN 0511-9618; © 2006 BGBM Berlin-Dahlem. doi:10.3372/wi.36.36114 (available via http://dx.doi.org/) The rare Ptilostemon greuteri from NE Sicily is described as a species new to science and illustrated. It belongs to P. sect. Ptilostemon due to its non-spiny leaves and the corymbose synflorescence. From the two other species of this section, P. chamaepeuce and P. gnaphaloides, it differs strikingly by the larger size of the whole plant, the flat, lanceolate leaves and the absence of peripheral male flowers. The species, of which about 250 individuals are known, is restricted to a single locality and must be classified as endangered.