Flexammina Voltski & Pawlowski, 2015, gen. nov.

Flexammina gen. nov.

Etymology. ‘ Flex ’ from English ‘flexible’ denoting the plasticity of the test shape; ‘ ammina ’—from the Greek ‘psammon’ meaning ‘sand’—refers to the agglutinated mineral material covering the test.

Type species. Flexammina islandica.

Diagnosis. Test free or attached, monothalamous. The test shape is subspherical or elongated when free, domelike when attached; aperture subcircular to irregular, surrounded by a short collar; test wall flexible, formed by a thick layer of mineral grains with an underlying layer of organic material.

Phylogenetic position. The type species F. islandica branches in the clade M of monothalamous foraminifera, based on the phylogenetic analysis of SSU rDNA gene sequences.

Remarks. There are some monothalamids that morphologically resemble Flexammina. Of these, Leptammina Cedhagen et al. (2009) is a genus from the deep Weddell Sea, with a similar test morphology possessing a flexible spherical test composed of fine mineral particles and a collared aperture. However, there is no evidence that Leptammina is able to assume attached dome-shaped form; its test wall agglutination is more uniform and finer. Moreover, this genus is very distant genetically, belonging to the ‘clade C’ of monothalamids. Some species of Hemisphaerammina Loeblich and Tappan (1957) and Crithionina Goës (1894) superficially resemble the attached form of Flexammina by the test shape and the character of their test wall agglutination. However, their tests lack the aperture on the upper surface and the basal test wall in Hemisphaerammina is completely absent. According to genetic data, Hemisphaerammina is branching at the base of the ‘clade F’ of monothalamous foraminifera, while the genus Crithionina is polyphyletic.

Finally, some foraminifera reported further in this study, mostly the undetermined saccamminids ICEMON 3 and ICEMON 6 were poorly distinguishable from smaller, free individuals of F. islandica. We did not find enough specimens of these saccamminids to provide the full descriptive information and clearly outline the essential morphological differences, but none of them were genetically close to Flexammina.