THOMPSONIANUM Wale, 1940
According to 't Hart, Bleij & Zonneveld in IHSP, 2003 "most probably the hybrid S. ciliosum ssp. octopodes x S. marmoreum ssp. reginae-amaliae. Morphologically, it is intermediate bewteen the alleged parents (shape of the rosettes and flower colour) and its pollen fertility is very low."
See also : Alan Smith, The Genus Sempervivum and Jovibarba, 1980