The taxonomy of the genus Vejdovský, 1882 is reviewed. New morphological information on (Vejdovský, 1882), the type species of the genus, is provided, and a new reference material is presented. The generic diagnosis is emended with details derived from the developmental trajectory of the valves, from the juvenile stage A-3 to the adult. Those criteria clearly differentiate from the related genus Kaufmann, 1900. As here redefined, is a phylogentic lineage of the subfamily Candoninae containing extant species presently living in aquatic subterranean habitats and fossil species recovered from non-marine Late Palaeogene to Neogene and Quaternary deposits in Europe and western Asia. The type species of is considered a metaspecies, taxonomically treated as (), which includes populations resembling the newly designated reference material. The homeomorphic triangular valve shape of the Candoninae is discussed. Careful examination of the valve morphology of combined with the analysis of limb traits helps to distinguish representatives of this genus from unrelated phylogenetic groups presenting similar triangularly shaped valves. It is emphasised that for a useful description of taxa both transmitted light and scanning electron microscopy are necessary.

Quantitative approaches dealing with soft- and hard-part morphological variability of ostracods are very rare for most species. Here we present intraspecific limb and shell variability of the Neotropical freshwater ostracod species assumed as . For the first time such an analysis considered adult females and males, as well as juveniles. Variability of the appendages included the antennule, second antenna as well as the first and second thoracopod and was analysed in terms of ratios of podomeres, setae and limbs. Limb variability of adult and juvenile individuals (down to A-3) is generally low. The highest variation is shown in podomere proportions of the antennas, while thoracopods and setae provide minor and/or non-significant influence on the variability. Based on discrimination analyses shell parameters (i.e., shell length, position of the transversal sulcus) emerge to be more important for differentiation of groups than limb ratios. Adult females exhibit a large size range in which two clearly separated morphotypes exist. Although differences in limbs are small their existence can be proven also on the basis of proportions between podomeres of the antennas. Males and juveniles, however, do not display a separation into corresponding subgroups or morphotypes. The presence of two morphologically similar females and only one type of males indicates the coexistence of female morphotypes which may represent either two (cryptic) species or a mixed reproduction population in which parthenogenetic and sexual reproduction coexists.