Thouarella biserialis ( Nutting, 1908 )

TAYLOR, M. L., CAIRNS, S. D., AGNEW, D. J. & ROGERS, A. D., 2013, <strong> A revision of the genus <em> Thouarella </ em> Gray, 1870 (Octocorallia: Primnoidae), including an illustrated dichotomous key, a new species description, and comments on <em> Plumarella </ em> Gray, 1870 and <em> Dasystenella </ em>, Versluys, 1906 </ strong>, Zootaxa 3602 (1), pp. 1-105 : 90

24. Thouarella biserialis ( Nutting, 1908)

Amphilaphis biserialis Nutting, 1908: 573 , pl. 43, fig. 4, pl. 47, fig. 4; Cairns & Bayer 2009: 28 (listed)

Thouarella biserialis Kinoshita 1908c: 519–520 , 2 text figs; Kükenthal 1915: 151 (listed); 1919: 438–9; 1924: 301; Parrish & Baco 2007: 192 (listed)

Thouarella (Diplocalyptra) biserialis Cairns, 2010: 417 , figs 2–3

Material examined: Holotype, USNM 22583, USFWS Albatross 398210, Mawiliwili, Kaua’i Island , Hawaii, North Pacific Ocean , 21˚56’25”N, 159˚21’40”W, 73–426 m, June 1902, 2 short branches.

Description

Modified from description in Cairns (2010):

The holotype, now in 2 fragments of 4 cm and 3 cm length, appears to be from a dichotomously branched, uniplanar colony. The polyps are cylindrical to clavate, 1.2–1.5 mm high, curved upward at 45°, and arranged in pairs standing on opposite sides of the branchlets with the plane of the colony. The polyps are rarely in whorls of 3. There are 6–7 scales in 8 longitudinal rows, 5–6 in the outer lateral rows, 2–3 in the inner lateral rows and 1–2 adaxially. Adaxial rows are short, revealing a largely naked adaxial face.

The operculars are lanceolate to widely-triangular, small (up to 280 µm high), and bluntly tipped, with a H:W of 1.6–2.0. The outer opercular surface is flat and has granules proximally whilst the distal inner surface is smooth (unkeeled), bearing rounded longitudinal bulges.

The marginal scales are triangular, up to 400 µm high, with a H:W of 1.5–1.8, with a wide multi-keel area on the inner surface and granules sparsely covering the outer surface. The marginal scales fold over the smaller operculars, shielding them from view.

The body-wall scales are often wider than high, up to 290 µm high with a H:W of 0.67–1.1. Those in the upper part of the polyp have a series of longitudinal ridges on the distal inner surface, resulting in a serrated distal edge.

The coenenchymal scales are elliptical, up to 300 µm in diameter and their outer surface is concave and smooth with some granules.

For images see Cairns (2010).

Distribution

Known only from type locality southeast of Kaua’i , Hawaii, at depths of 73–426 m.

Comparisons

Being dichotomously branched with polyps in pairs, T. biserialis is comparable to T. parva and T. coronata . Thouarella parva is most similar to T. biserialis as both have polyps that depart branchlets at 45˚ and more rounded marginals than those found on polyps of T. coronata . However, the polyps of T. biserialis have a distinct keel on the inner surface of marginals, something not clearly illustrated for T. parva . Additionally, polyps of T. biserialis appear more clavate than those of T. parva and T. coronata . The polyps of T. coronata are a similar size to those of T. biserialis , however, they diverge from branchlets at 90˚ rather than 45˚. Additionally, the polyps of T. biserialis are clavate rather than being distally flared, as in T. coronata , which also has polyps with taller, more pointed marginals than found on T. parva .