Heleopera steppica Useros & Lara, 2023
Diagnosis: Transparent test, colourless or yellowish. Ovoid shape, but vertically compressed and with a flatter oral side. Narrow and elliptical terminal oral aperture with a thin cement collar. Test composed of circular and elongated siliceous shell plates of various sizes, obtained from diatom frustules and Euglyphida shell scales, on which they prey.
Dimensions: Shell length: 60.7 – 71.0 μm, average 66.05, standard deviation (SD) 2.49 μm (N = 24); Maximum width 27.9 – 46.1 μm, average 41.73, SD 3.49 μm (N = 24); Oral width 20.3 – 32.7 μm, average 24.91, SD 3.03 μm (N = 24); Distance from point of maximum with to bottom of the test 15.6 – 26.0 μm, average 20.93, SD 2.95 μm (N = 24).
Ecology: Found in mosses from Mediterranean-continental shrublands and grasslands growing on gypsum soils.
Geographical distribution: Spain (39°59′30′’N, 3°36′55′’W)
Remarks: Heleopera steppica can be diagnosed by its specific mtDNA (COI) and nuclear (SSU rRNA) sequences and by its phylogenetic placement. It is morphologically very similar to H. sylvatica and falls within the size range given in Penard (1890) original description of 50 – 75 μm, although it is smaller than the range given in Todorov & Bankov (2009), 88 – 108 μm. The original description of Penard illustrated individuals with perpendicularly attached siliceous plates on the margin of the aboral region, which are absent in Heleopera steppica.