Thouarella Gray, 1870

Cairns, Stephen D. & Häussermann, Verena, 2021, A new species of Thouarella from Chilean Patagonia, Spixiana 44 (1), pp. 1-8 : 2-4

Genus Thouarella Gray, 1870

Thouarella Gray, 1870: 45 . – Cairns, 2006: 175-176; 2011: 4-5. – Taylor et al., 2013: 20-21 (species groups 1 and 2, complete synonymy). – Taylor & Roger, 2015: 197.

Thouarella (Diplocalyptra) Kinoshita, 1908: 454 . – Cairns & Bayer, 2009: 34-35.

Thouarella (Euthouarella) Kükenthal, 1915: 149 . – Cairns & Bayer, 2009: 34. – Cairns & Wirshing, 2018: 18.

Thouarella (Parathourella) Kükenthal, 1915: 150 .

Thouarella (Epithourella) Kükenthal, 1915: 150-151 . – Cairns & Bayer, 2009: 35.

Thouarella (Thouarella) Bayer, 1956 : F220. – Cairns & Bayer, 2009: 33-34. – Cairns & Wirshing, 2018: 18.

Type species. Primnoa antarctica Valenciennes, 1846 , by monotypy.

Diagnosis (from Cairns 2011). Colonies bottlebrush, uniplanar pinnate, or dichotomous in branching.

Polyps isolated (occurring on all sides on the stem and branchlets in a random fashion, i. e., subgenus Thouarella ) or arranged in pairs of whorls (subgenus Euthouarella ). Each polyp covered by 6 or 8 longitudinal rows of body wall scales, the scales on the adaxial side reduced in size and number to accommodate inward flexing of polyp. Marginal scales often arranged in 2 circles of 4 scales that alternate with one another, each marginal bearing simple or ornate longitudinal keel or multiple keels that, when the marginals fold over the opercular scales, glide along the outer concave surface of the underlying opercular scales. Opercular scales lanceolate or tongue-shaped, often bearing a longitudinal ridge on inner surface; smaller accessory opercular scales sometimes present.

Remarks. The genus Thouarella has been intensely studied over the last century, its species being allocated to various subgenera and species groups (see synonymy above) based on various morphological criteria such as polyp placement, colony branching, and nature of the distal edge of the marginal scales. The history of research in this genus is recounted by Cairns (2006, 2011), Cairns & Bayer (2009), Taylor et al. (2013), Taylor & Rogers (2015), and Cairns & Wirshing(2018), and will not be repeated here, except to say that the monograph of Taylor et al. (2013) includes descriptions and illustrations of all extant species to that time (usually based on type material), an exhaustive key to the species, and a discussion of character states. Most recently, the molecular studies of Taylor & Rogers (2015) and Cairns & Wirshing (2018) suggest that there are two subgenera within the genus, differing in the arrangement of their polyps, i. e., randomly (nominate subgenus) or in pairs and whorls (subgenus Euthouarella ). The nominate subgenus consists of 25 species, subgenus Euthouarella consists of nine species.The new species described herein belongs to the nominate subgenus.

Distribution. Cosmopolitan, especially common in the Antarctic and Subantarctic, 11-6400 m.