Stannophyllum spp.

Holzmann, Maria, Barrenechea-Angeles, Inés, Lim, Swee-Cheng & Pawlowski, Jan, 2024, New xenophyophores (Foraminifera, Monothalamea) from the eastern Clarion-Clipperton Zone (equatorial Pacific), Zootaxa 5419 (2), pp. 151-188 : 183-184

Stannophyllum spp.

Supplementary Figs S14–S 16

Material examined (morphology). BC014 RC0598. BC015 RC0613. BC001 RC0036.

Descriptions. Specimen RC0598. A shipboard photograph shows the test attached to a nodule (Supplementary Fig. S14A ). It is 23.2 mm long, 19.5 mm wide, between 530 and 600 µm thick and has a fairly symmetrical and basically subtriangular outline, a semi-circular distal margin and sides that taper down to a relatively narrow attachment point (Supplementary Fig. S14B ). A concentric zonation pattern is visible across the entire test and stands out clearly when the specimen is viewed in transmitted light (Supplementary Fig. S14C ). The surface layer is greyish and more or less continuous. Compared to S. aff. granularium , it includes fewer obvious radiolarians and spicules and a considerably larger proportion of fine-grained material (Supplementary Fig. S14D ). There is also a scattering of brown particles, many of them globular and cyst-like but a few elongate with one serrated side. Linellae form a dense mesh that is visible in occasional chinks in the surface layer and around the margin (Supplementary Fig. S14E ). Granellare strands were not observed.

Specimen RC0613. Shipboard photographs show the specimen attached to a nodule, with the lower part forming a thin layer that spreads across nodule surface (Supplementary Fig. S15A, B ). The upper part extends upwards from the nodule surface, at approximately right angles to the attached part (Supplementary Fig. S15C ). This upstanding section of the test was about 24 mm long. It comprised a narrower lower section, between 8.0 and 9.5 mm wide with a short lobate lateral protuberance, and a wider, irregularly shaped upper section, 15–16 mm wide. The upper part is clearly marked by rather irregular, approximately concentric furrows in the shipboard photographs (Supplementary Fig. S15A ).

The preserved specimen is 985–1300 µm thick, with a thin outer wall ~60 to 100 µm thick. The wall is almost continuous with a rather rough surface and quite similar to that of RC0598, although the overall colour is a rather more greyish shade of brown. It consists basically of a fine-grained matrix with embedded radiolarians. There are few other particles, apart from a number of black grains (presumably micronodules) and one or two protruding spicules. The brownish‘cysts’ that were a feature of RC0598 are absent. Cross-sections of the main part of the test show the interior occupied largely by stercomare and internal xenophyae, mainly radiolarians.

Detachment of the test from the nodule revealed a nearly circular attachment area, measuring 10.5 mm by 10.0 mm, where the wall was absent, and the test interior was in direct contact with the nodule surface (Supplementary Fig. S15D ). Rather featureless stercomare that appeared to be somewhat decayed was attached to the inner surface of this part of the test wall, together with radiolarians. Also present were small pieces of slightly reddish granellare, ~75–115 µm wide. This detached part of the test was largely excavated in order to remove the sparse granellare, revealing strongly developed masses of linellae. Detached fragments of the wall from the main part of the test are also associated with a meshwork on these organic fibres.

Specimen RC0036. Shipboard photographs show the test attached to a nodule, with the main part projecting up from the surface and the lower part spreading across the surface (Supplementary Fig. S16A). The upper part is a lobate structure, 12.8 mm long, 10.7 mm wide and 930–1030 µm thick, with a semi-circular distal (upper) margin (Supplementary Fig. S16B, C). It is brownish in overall colour with a rather muddy surface layer in which are embedded radiolarians of various sizes and a scattering of dark particles together with a few agglutinated foraminiferal tests (Supplementary Fig. S16D). Although the surface is uneven, the embedded particles do not protrude to any great extent. The muddy layer is not present around the test periphery, where the underlying structure of the test, consisting mainly of small radiolarians, is exposed (Supplementary Fig. S16F). The particles are held in place by linellae, which are visible in places around the margin.

At its base the test extends into a single thin sheet, about 13.6 mm long, that was originally attached to the nodule (Supplementary Fig. S16B). The constituent particles comprise mainly radiolarians, micronodules and fine-grained material, held together by linellae. The muddy layer is not well developed so that the particles protrude to a greater extent than on the main part of the test.

Remarks. Like Stannophyllum aff. granularium , these three specimens have a well-developed surface layer of linellae that holds together the test wall. However, in contrast to S. aff. granularium the surface layer is more or less complete without any significant gaps. They also differ from each other, as well as from S. aff. granularium , in a number of other respects. 1) RC0589 has a tapered test whereas and RC0036 and RC0613 are more rectangular. 2) The wall of RC0598 includes distinctive brownish particles, in RC0036 it is muddy and rather thick, in RC0613 it is relatively thin. 3) RC0613 is the greyest of the three (a consequence of the thinner wall and interior filling of decayed stercomare); RC0598 is also basically grey but a rather lighter shade than RC0613, whereas RC0036 is brownish. 4) RC0589 has a fairly distinct concentric zonation, RC0036 and RC0613 lack obvious zonation. 5) RC0613 and RC0036 have thicker tests (985–1300 µm and 930–1030 µm, respectively) compared to RC0598 (530–600 µm), which is more similar in thickness to S. aff. granularium (520–870 µm).

Without genetic data, we cannot determine whether these three specimens represent distinct species or variants of one species, or whether they are related to S. aff. granularium . RC0589 is most similar morphologically to S. aff. granularium , but differences in the test shape, agglutination and the relatively strong zonation suggest that it is not the same. This specimen shares some features with S. zonarium , but lacks the characteristic bundles of linellae that arise from the base of test in this species (Gooday et al., 2020). Morphologically, RC0613 is quite similar to S. paucilinellatum Kamenskaya, Gooday, Tendal, 2017 from the Russian license area in the central CCZ (Kamenskaya et al., 2017). However, linellae are sparsely developed in the Russian species, including within the test wall, so that identification seems unlikely. Granellare fragments taken from the base of RC0613 yielded sequences that do not cluster with those derived from the two undoubted Stannophyllum species for which we have genetic data. For this reason, and because other parts of this specimen appear to be dead, we regard these sequences as unreliable.

Figures

FIGURE 14. Stanophyllum aff. granulatum; sequenced specimen RC0489 (BC010). A, B Shipboard photographs A, Specimen attached to a nodule. B. Side view. C–F, Laboratory photographs. C, Entire specimen. D, E, Edge of test showing granellare branches and fringe of radiolarians attached to organic fibres (linellae). F, Granellare removed from test.

FIGURE 15. Stanophyllum aff.granulatum; specimen that was not sequenced, RC0608 (BC015).A, B,D Shipboard photographs C, E, F, Laboratory photographs.A, B, Specimen attached to a nodule. C. Specimen detached. D, Base of test showing attachment to nodule. E, Detail of surface. F, Edge of test showing organic fibres (linellae). Scales were not available for A and B.