Psammina multiloculata Kamenskaya, Gooday, Tendal, 2015

Fig. 13

Psammina multiloculata Kamenskaya, Gooday, Tendal, 2015: p. 584 –585, Figs 2, 3.

Psammina multiloculata Kamenskaya, Gooday, Tendal, 2015 . Kamenskaya et al., 2017, 300–301, Fig. 1a–d.

Material examined. Box core 10. Specimen RC0490 (morphology).

Description. Shipboard photographs. The single specimen stood vertically on the surface of the nodule to which it was attached (Fig. 13A, B). It comprised a basal stalk and an upper part with a number of plate-like elements radiating out from a central axis. The apparent height of the test, viewed from different angles, ranged from about 7.0 to 7.5 mm (mean 7.2 mm), but this was strongly influenced by foreshortening. The width varied from 4.4 to 5.9 mm (mean 5.37), depending on which plates were in view. Three main plates were visible when the test was viewed from above (Fig. 13C); they were more or less straight or slightly curved, of fairly even width (0.33-0.48 mm), and measuring 3.3, 2.5 and 2.0 mm in length. The plate of intermediate length divided at the end into two short side plates, about 0.90 and 1.10 mm long. The height of the stem, measured as the distance between the base and the highest side plate but again foreshortened to varying degrees, ranged from 2.16 to 3.14 mm depending on the orientation, and the width from 1.15 to 1.90 mm. It tapered downwards but widened slightly at the base.

Most of the test surface was dark, but with a paler zone around the plate rims, particularly along their upper edges (Fig. 13A, B). A vague, approximately concentric zonation is visible on some of the plates, together with a faint pattern comprising small, slightly raised patches and shallow depressions, corresponding to the compartmentalization described below.

Preserved specimen. The test, detached from the nodule, measures 10.7 mm long and 6.2 mm wide, as orientated in Fig. 13D. Most of the stem and the three upper plates are intact (Fig. 13D–E), although there is some damage around the edges of the plates. The test wall is very thin (~20 µm) and delicate (Fig. 13F–H). It is composed of fine transparent mineral grains, probably quartz, mixed with sponge spicules fragments, scattered dark particles and occasional reddish grains. Most of the non-biogenic grains are ~35 µm or less in size, although some are larger. At least one agglutinated foraminiferan test is incorporated into the wall. Where the edge of the test is intact, the wall continues around it with no obvious apertures. The overall colour is dark grey, influenced by the stercomare that largely fill the test and are dimly visible through the thin wall.

The test interior is partitioned into cell-like compartments. These are visible on the surface as slightly raised patches filled with dark stercomare, except for the pale peripheral zone (Fig. 13F). These patches are often somewhat rectangular and tend to be arranged concentrically, particularly towards the margin. It is difficult to give precise sizes, but they are on the order of ~600–700 µm long and ~420 µm wide. The cytoplasm is visible on broken edges as pale whitish strands enclosed within a delicate, transparent granellare tube, as well as larger, more irregular masses, notably in the stem.

Remarks. This is the first record of Psammina multiloculata from outside the Russian license area in the more central part of the CCZ. Our specimen agrees fairly well with the original description (Kamenskaya et al., 2015), particularly as regards the basically plate-like test morphology and its characteristic internal subdivision into small, cell-like compartments. There are some differences. The four Russian specimens either lacked a stalk (as in the holotype) or had a very short stalk. One of the two additional specimens described by Kamenskaya et al. (2017) had a short, tapered stalk, 5 mm long and up to 15 mm wide, while the other comprised the stalk, 5 mm long and 8 mm wide, and just the base of the upper plate-like part. The much larger size of the Russian specimens (usually> 20 mm maximum dimension) suggests the greater proportion of the test occupied by the stalk in our specimen may be a juvenile feature.

Our specimen of P. multiloculata shares many features with Psammina sp. 3 from Stratum B of the UK-1 area, illustrated and briefly described in the supplementary material for Gooday (2017a; Supplementary Figure 4d, e therein). This earlier specimen is similar in size, 8.5 mm high and a maximum of 5.5 mm wide. The test wall contains a high proportion of sponge spicules, and the interior is partitioned into compartments that are occupied by stercomare masses of irregular width (typically 200–300 µm) and granellare strands (65–80 µm wide). The main difference is that the test is curled around to form an almost tubular structure. Possibly, they are conspecific, but this cannot be confirmed in the absence of genetic data.