Genus Quadrulella (Cockerell 1909) sensu Kosakyan et al. 2016
Diagnosis: Test pyriform, or elongated pyriform, with the lateral sides tapering towards the pseudostome, with or without distinct neck. Always laterally compressed, elliptical in cross section. Pseudostome ranging from linear to strongly curved, with or without thickened organic lip. Test hyaline, composed of self-secreted square siliceous plates.
Type species: Quadrulella symmetrica (Wallich 1864) Cockerell 1909.
Included taxa: Q. acuminata, Q. alata, Q. camerounensis, Q. elegans, Q. elongata, Q. quadrigera, Q. madibai, Q. scutellata, Q. tropica, Q. symmetrica, Q. texcalense and Q. variabilis.
Ecology: Sphagnum and moss, generally submerged.
Remarks: Quadrulella differs from Nebela and Hyalosphenia by the use of square, siliceous self-secreted plates in the construction of the test. It may be confused with Mrabella, which has similar test shape and square plates. The most distinctive characteristic is the presence of a lateral pronounced hollow keel in the genus Mrabella (although Q. alata also exhibits a lateral keel, we consider it to be flat and not hollow, even if this detail is not mentioned in the original description of the species), and the fact that square plates of Quadrulella are self-secreted, while the origin of square plates of Mrabella is unclear.
Reference: Kosakyan, A., Lahr, D.J.G. , Mulot, M., Meisterfeld, R., Mitchell, E.A.D. and Lara, E.: Phylogenetic reconstruction based on COI reshuffles the taxonomy of hyalosphenid shelled (testate) amoebae and reveals the convoluted evolution of shell plate shapes – Cladistics (2016) 1–18.