Quadrulella texcalense Pérez-Juárez, Serrano-Vázquez and Lara, 2017
Description: Test (shell) pyriform, with a rounded posterior end; posterior 1/3 of the tests, sides converging towards the aperture or pseudostome, either straight, slightly convex or slightly concave, laterally compressed and transparent. Test composed of square endogenous plates that range in size between 3.3 and 6.5 µm in a single cell, generally arranged in an orderly fashion although some may be irregularly arranged. Aperture curved (convex), oval-shaped in frontal view, with the typical organic rim considered as a synapomorphy of the family Hyalospheniidae.
Dimensions: length = 97–126 µm, width = 53–68 µm, aperture width = 24–32 µm (n=21)
Ecology: Desert soil, Mexico.
Remarks: Quadrulella texcalense exceeds most other species in size, with the exception of Q. scutellata and Q. quadrigera, from which it differs on the base of its more regular plates. The size of its plates and its general pyriform shape reminds of the much smaller Q. variabilis.