Notes on the nomenclature and taxonomy of Chiastophyllum and Umbilicus oppositifolius (≡ Cotyledon oppositifolia, ≡ Chiastophyllum oppositifolium) (Crassulaceae subfam. Sempervivoideae) Author Smith, Gideon F. 0000-0002-5417-9208 Ria Olivier Herbarium, Department of Botany, Nelson Mandela University, P. O. Box 77000, Gqeberha, 6031 South Africa. smithgideon 1 @ gmail. com; https: // orcid. org / 0000 - 0002 - 5417 - 9208 smithgideon1@gmail.com Author Monro, Anna M. Australian National Herbarium, Centre for Australian National Biodiversity Research (a joint venture between Parks Australia and CSIRO), GPO Box 1700, Canberra ACT 2601, Australia. text Phytotaxa 2022 2022-09-16 564 2 239 247 journal article 147237 10.11646/phytotaxa.564.2.7 0ac69fbc-2113-4f21-8b1f-e5a926eea567 1179-3163 7087286 Umbilicus oppositifolius (Ledeb. ex Nordm.) Ledebour (1843: 176) . Homotypic synonyms :— Cotyledon oppositifolia Ledeb. ex Nordmann (1837: 313) . Chiastophyllum oppositifolium (Ledeb. ex Nordm.) Stapf (1930: 316–317) . Type :— ““ Caucasus ” ( Nordmann 329 [LE])” fide Walker (2003: 366 , as “ T ”, i.e., “(nomenclatural) type ”, see Eggli 2003 : X) . Taxonomic placement of Chiastophyllum and Umbilicus oppositifolius :—At present Chiastophyllum is usually treated as a section in Umbilicus , as U . sect. Chiastophyllum , with the genus included in the Telephium clade of Crassulaceae subfam. Sempervivoideae ( Eggli et al . 1995: 179 , 191, Walker 2003: 364 , Thiede & Eggli 2007: 97 , Messerschmid et al . 2020: 893 ). Umbilicus sect. Chiastophyllum is monotypic, with U. oppositifolius the only included species. Umbilicus oppositifolius has fibrous roots, while the roots of all other species of Umbilicus are tuberous or rhizomatous. The leaves of U. oppositifolius are not peltate and are more or less ovate, whereas all its congeners have more or less peltate leaves with the leaf blades varying little from an orbicular outline ( Fig. 2 ) ( Smith & Figueiredo 2011 ). The flowers of U. oppositifolius range from light to bright yellow and are carried in branched, arched inflorescences ( Fig. 1 ). Selected forms of the species are available in the horticultural trade.