Thouarella Gray, 170: 45.— Wright & Studer, 1889: 59 –61.— Cairns, 2010: 415.—Taylor, et al., 2013: 20–21 (monograph of genus, including key to all species).— Cairns & Wirshing, 2018: 11. Thouarella (Thouarella) Cairns & Bayer, 2009: 33.
Type Species. Primnoa antarctica Valenciennes, 1846, by monotypy.
Diagnosis. Colonies bottlebrush in shape or uniplanar, the latter branched dichotomously or pinnately. Polyps isolated on branches (nominate subgenus) or arranged in pairs or whorls (subgenus Euthouarella). Polyps protected by 6–8 rows of body wall scales, the 2 adaxial rows having smaller and fewer scales, especially near base of polyp. Marginal scales capable of folding over operculum, arranged in two circles of four scales. Marginals have a prominently keeled inner surface.
Discussion. The genus was monographed by Taylor et al. (2013), in which all species were described, illustrated and keyed. They divided the genus into two groups: group 1 having isolated polyps, group 2 having polyps arranged in pairs or whorls. Cairns & Wirshing (2018) resurrected subgeneric names for these two group names. The genus currently consists of 32 species, and, although worldwide in distribution, is concentrated in the Subantarctic and Antarctic regions.
Distribution. Worldwide, 11–6400 m.