Kaliwatan sa bakukangon ang Hydraena unca.^[1] Una ning gihulagway ni Valladares ni adtong 1989.^[2] Ang Hydraena unca sakop sa kahenera nga Hydraena, ug kabanay nga Hydraenidae.^[1][3]

Kini nga matang hayop na sabwag sa:

• Portugal
• Espanya

Walay nalista nga matang nga sama niini.^[1]

1. ↑ ^{1.0 1.1 1.2} Roskov Y., Kunze T., Orrell T., Abucay L., Paglinawan L., Culham A., Bailly N., Kirk P., Bourgoin T., Baillargeon G., Decock W., De Wever A., Didžiulis V. (ed) (2019). "Species 2000 & ITIS Catalogue of Life: 2019 Annual Checklist". Species 2000: Naturalis, Leiden, the Netherlands. ISSN 2405-884X. TaxonID: 53252933. Retrieved 2019-11-11. {{cite web}}: |author= has generic name (help)CS1 maint: multiple names: authors list (link)
2. ↑ Valladares, L. F. (1989) Separación específica de las dos subespecies de Hydraena cordata Schaufuss, 1833 sensu Berthélemy (1965) (Coleoptera: Hydraenidae), p. 143. In: Abstracts volume. , International Congress of Coleopterology, Barcelona, September, 18-23, 1989; Asociación Europea de Coleopterología, Barcelona. 156 pp.
3. ↑ Newton A.F. (2019). StaphBase: Staphyliniformia world catalog database (version Nov 2018). In: Species 2000 & ITIS Catalogue of Life, 2019 Annual Checklist (Roskov Y., Ower G., Orrell T., Nicolson D., Bailly N., Kirk P.M., Bourgoin T., DeWalt R.E., Decock W., Nieukerken E. van, Zarucchi J., Penev L., eds.). Digital resource at www.catalogueoflife.org/annual-checklist/2019. Species 2000: Naturalis, Leiden, the Netherlands. ISSN 2405-884X.