Pennaria Goldfuss, 1820: 89.
Type species. Pennaria disticha Goldfuss, 1820, by subsequent designation by Bedot (1901).
Diagnosis. Capitate Hydrozoa having characters of the family Pennariidae.
Remarks. Confusion over the taxonomic status of the name Pennaria, the authorship of which is now attributed to Goldfuss (1820), was clarified by Gibbons & Ryland (1989). Halocordyle Stechow, 1921a is thus regarded as a junior synonym. Other issues surrounding the taxonomy and nomenclature of the genus were discussed by Calder (1988).
Numbers of species currently recognized worldwide in the genus Pennaria vary from eight (Bouillon et al. 2006; Schuchert 2009) to two (Daly et al. 2007), the latter estimate presumably referring to the hydroid stage only.