Aliena parva

Description. The holotype is formed of 15 scattered clusters of polyps encrusting the surface of a barnacle about 4 cm in diameter; the barnacle plates are covered by many epibionts and several small, unbranched hydroids (Fig. 2 A). The polyps are in clusters, 0.15 - 1.10 cm in longest dimension and composed of 3 - 20 polyps (Fig. 2 A). The polyps are closely spaced; those that are preserved partially expanded are up to 2.0 mm tall (from the base to the proximal border of tentacles) (Fig. 2 B). Polyps are retractile into calyces that are up to 0.75 mm in diameter, and up to 1.0 mm tall when the anthocodia is retracted. The surface of the calyx is covered by a dense layer of sclerites giving it a slightly granular appearance. The tentacles are transparent with yellow sclerites. When retracted, the yellow sclerites can be observed at the polyp-mound summit (Fig. 2 C). The coenenchyme is thin and without differential sclerite layers; it extends over the substrate. Coenenchymal sclerites are asymmetrical spindles with variable ends: pointed, blunt, bifurcated, or a combination (Figs 4, 5). They are straight or slightly curved, 0.16 - 0.35 mm long, and 0.02 - 0.08 mm wide (Figs 4 A, 5 A), with simple tubercles, not very crowded on the surface; they do not have complex tubercles or waists. Anthocodial sclerites are mostly red flat rods, 0.20 - 0.30 mm long and 0.02 - 0.06 mm wide, with serrated or prickly borders and sparse thorns on the surface, and smaller biscuit-like rods, 0.06 - 0.10 mm long and 0.02 - 0.03 mm wide (Fig. 4 C, 5 B). Anthocodial rods are arranged ' en chevron ', forming points but not a collaret (Fig. 2 B). The flat rods are arranged in longitudinal rows along the polyp body (Fig. 2 B, 5 D). Tentacular sclerites are spine-like rods with a bent end 0.14 - 0.29 mm long and 0.02 - 0.03 mm wide (Figs 4 B, 5 C). Colonies are dark red in life and when preserved (Fig. 2 A-C). Coenenchymal sclerites are mostly dark red, but sometimes with lighter hues (Fig. 4 A). The characteristics of the paratypes are very consistent with those of the holotype.

Figs 2, 3, 4, 5, 6

Distribution. Colonies were found at various localities north of Isla del Coco around Manuelita Afuera, Manuelita Canal and Bajo Manuelita; and northwest at Roca Sucia, 05 ° 32.875 ' N, 087 ° 04.956 ' W and Viking Rock (Isla Cascara), 05 ° 33.006 ' N, 087 ° 03.865 ' W, NW of the island (Fig. 1). Only known from the type locality. The bathymetric range was 20 - 30 m.

Etymology. Parvus (L), in allusion to the small size of the polyps. Gender feminine: Aliena parva.

Materials examined. Holotype. MZUCR 3679, lot 1, ethanol-preserved, Manuelita Afuera, Isla del Coco, 05 ° 33.791 ' N, 087 ° 02.934 ' W, 22 m depth, J. Cortes and M. Cruz, 4 December 2021. Paratypes. MZUCR 3680, lot 2, same data as holotype. MZUCR 3681, lot 1, lot 2, ethanol-preserved, Manuelita Canal, Isla del Coco, 05 ° 33.524 ' N, 087 ° 02.940 ' W, 20 - 30 m depth, B. Naranjo, 12 October 2021. MZUCR 3682, ethanol-preserved, Bajo Manuelita, Isla del Coco, 05 ° 33.849 ' N, 087 ° 02.676 ' W, 23 m, J. Cortes and A. Klapfer, 6 December 2021. MZUCR 3683, Manuelita Afuera, Isla del Coco, 05 ° 33.791 ' N, 087 ° 02.934 ' W, 29 m depth, O. Breedy, 28 September 2022. MZUCR 3684, Manuelita Afuera, Isla del Coco, 05 ° 33.791 ' N, 087 ° 02.934 ' W, 25 m depth, O. Breedy, 4 October 2022.