The family Proalidae is a small group of monogonont Rotifera that was erected as the subfamily Proalinae of the Notommatidae by Harring & Myers (1924). It was given family rank by Bartoš (1959). The Proalidae comprises predominantly free-living epiphytic-epibenthic and psammobiontic species, inhabiting the littoral zone of fresh, thalassic and athalassic waters, and damp terrestrial habitats. Some species live epizoic on invertebrates and others are endoparasites of algae or ectoparasites of invertebrates.
Despite the eariy discovery of most of the species, the study of the Proalidae has been neglected due to the difficult identificarion of preserved specimens. As a consequence their distribution is insufficiently known and many species probably await description. The status of several species is confused, due largely to the fact that descriptions and illustrations of earlier authors are poor and only partially accurate.
A thorough revision of the Proalidae is actually hampered by the above mentioned lack of adequate descriptions and all but inexistent type material. Moreover, apart from a few exceptions, most of the species are rare and collected infrequently, and comparatively few specimens were available for this study. It is, however, clear that only a comprehensive application of scanning electron microscopy for the study of trophi structure, will allow a better specific identification and understanding of the inter-relationship of the species. This study is a first attempt at such a revision.