Stereodiktyoma Gooday & Holzmann, 2024

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 : 169-170

Stereodiktyoma Gooday & Holzmann gen. nov.

Diagnosis. Test attached, delicate, forming a complex three-dimensional network of tubular elements, not arranged according to any particular pattern. Wall soft, finely agglutinated.

Etymology. From the Ancient Greek στερεός (stereós), literally meaning “solid” but in this context three-dimensional, and the Greek diktyoma meaning a ‘network’. Gender neuter

Remarks. Stereodiktyoma has morphological characteristics that resemble those of several existing genera. Tendalia has a reticulated arrangement of tubes, but these lie more or less in one plane and the walls are thinner, coarser-grained and more rigid and brittle than those of the new genus. In some species of Syringammina , notably the type species S. fragilissima, the test comprises a three-dimensional system of tubes. However, like those of Tendalia , the tubes are relatively thin-walled, rigid and brittle, as well as being arranged, at least peripherally, in a distinct pattern, with ‘radial branches’ and ‘anastomosing lateral branches (that) form consecutive layers’ (p. 36 in Tendal, 1972). The new genus is most similar morphologically to Shinkaiya lindsayi , also the type species of its genus. This has a test comprising a meshwork of anastomosing tubes, the walls of which are relatively thick, fine-grained, soft delicate, and therefore quite similar to those of the new genus.

There is no genetic support for a close relationship between Stereodiktyoma and either Shinkaiya or Syringammina ( Fig. 1 ). It does branch in the same clade as Tendalia , although with no bootstrap (BV) support. The closest species to Stereodiktyoma genetically is Galatheammina sp. 2 of Gooday et al. (2017a). This relationship is supported by 100% BV, but as explained below, there is very little morphological similarity between the two species.

Figures

FIGURE 1. PhyML phylogenetic tree based on the 3'end fragment of the SSU rRNA gene, showing the evolutionary relationships of 79 foraminiferal sequences belonging to monothalamids. Specimens marked in bold indicate those for which sequences were acquired during the present study. The tree is unrooted. Specimens are identified by their accession numbers. Numbers at nodes indicate bootstrap values (BVs). Only BVs>70% are shown.