Psephellus, a segregate of Centaurea, counts ca. 75-80 Old World species. Nearly all are confined to eastern Turkey, the Caucasus and northwestern Iran (Wagenitz & Hellwig 2000, Duran & al. 2009). Its generic status was advocated based on morphological, anatomical, palynological and caryological grounds (Wagenitz & Hellwig l.c.) and more recently confirmed by molecular data as well (e.g. Aydin & al. 2013). Characteristic features are perennial life form, leaves tomentose, usually non-decurrent appendages, etc. At least one species, Psephellus dealbatus, is a fairly popular garden ornamental. It has been recorded as an escape in Belgium.
Aydin Ö, Çoşkunçelebi K., Gültepe M. & Güzel M.E. (2013) A contribution to taxonomy of Centaurea including Psephellus (Asteraceae) based on anatomical and molecular data. Turk. J. Bot. 37: 419-427. [available online at: http://journals.tubitak.gov.tr/botany/issues/bot-13-37-3/bot-37-3-1-1204...
Duran A., Öztürk M. & Doğan B. (2009) A New Species of the Genus Psephellus (Asteraceae) From North-East Anatolia, Turkey. Ozean Journal of Applied Sciences 2(1): 103-111. [available online at: http://ozelacademy.com/OJAS_v2n1_12.pdf]
Sosnovskii D.I. (1998) Centaurea subgenus Psephellus. In: Borisova A.G. (ed.), Flora of the U.S.S.R., vol. 28. Koeltz Scientif Books: 523-551.
Wagenitz G. (1975) Centaurea. In: Davis P.H. (ed.), Flora of Turkey and the East Aegean Islands, vol. 5: Edinburgh University Press, Edinburgh: 465-585.
Wagenitz G. & Hellwig F.H. (2000) The genus Psephellus Cass. (Compositae, Cardueae) revisited with a broadened concept. Willdenowia 30: 29-44. [available online at: http://www.bioone.org/doi/pdf/10.3372/wi.30.30102]