Genus Mrabella Kosakyan, Lahr, Mulot, Meisterfeld, Mitchell and Lara 2016
Diagnosis: Test elongated-pyriform, laterally compressed, with the lateral sides gradually tapering toward the pseudostome. Lateral margins distinctly compressed giving the impression of a thick and wide hollow keel. Because of this, the test is elongated elliptical with the pointed end in the profile. Test colourless, composed of quadrangular shell plates similar to those in Quadrulella species.
Type species. Mrabella subcarinata (Gauthier-Lievre, 1957) Kosakyan, Lahr, Mulot, Meisterfeld, Mitchell and Lara, 2016.
Included taxa: Q. subcarinata Gauthier-Lièvre, 1957 and the similar taxon Q. plicata Hoogenraad and De Groot, 1940.
Remarks: Kosakyan et al (2016): “A behaviour exhibited by the majority of members in the hyalosphenids is kleptosquamy, or the ability to scavenge plates from prey and use them to make the shell (Lahr et al., 2015). Under this framework, a possible scenario is that Mrabella is in fact using scales from preyed upon Quadrulella, or scavenging these scales from the environment to construct the shell. For instance, the description of Nebela galeata from Africa by Gauthier-Lièvre (1957) is almost identical to Q. subcarinata in the general shape and dimensions of the test (L=180–200, W=98–144, aperture 31–41 µm). Furthermore, square plates typical for Quadrulella can be integrated in the shell of N. galeata (Gauthier-Lièvre, 1957; Fig. 10a). Moreover, Gauthier-Lièvre (1957) documented other Quadrulella species from the same locality where she found Nebela galeata and Quadrulella subcarinata; these other Quadrulella species could therefore have provided the square plates used by these two species.”