Family Pennariidae McCrady, 1859

Diagnosis. (modified after Calder 2010). Capitate hydroids with erect colonies; stems monosiphonic, branches giving rise to hydranth pedicels, perisarc firm. Hydranth naked, spindle-shaped, with an aboral whorl of long filiform tentacles semicapitate distally, an oral whorl of short, capitate tentacles. Eumedusa without manubrium, with four radial canals and four rudimentary tentacles bulbs, velum not penetrated.