In this paper, a new species of the Cystoseira complex from Porto Palo di Capo Passero (Sicily, Italy) is described. The species, which shows the same characters as Cystoseira hyblaea Giaccone as described by Giaccone (1986) and Bouafif et al. (2016), from its morpho-anatomical characters, is assigned to the genus Ericaria Stackhouse. Because of “Cystoseira hyblaea” was not validly published name, Ericaria giacconei sp. nov. is here described. The main characteristics of the species are: 1) a caespitose habit; 2) large axes rugged with apices smooth, not prominent; 3) vegetative branches without spinose appendages; 4) primary branches with a cupressoid outline, especially when they are fertile; and 5) receptacles terminal, compact, cylindrical-oval, verrucose, with deciduous spinose appendages. Ericaria giacconei sp. nov. is related to both E. crinita (Duby) Molinari & Guiry and E. barbatula (Kützing) Molinari & Guiry, but it differs from them mainly in the basal system consisting of a robust and compact basal disc and in apex of cauloids smooth and not prominent, never surrounded by spiniform appendages. A critical re-examination of herbarium specimens from Isola delle Correnti (eastern Sicily, Italy) attributed to E. crinita (as C. crinita) demonstrated that they actually belong to our new species.
Sargassaceae, Cystoseira complex, Sicily, Mediterranean Sea