Gonaxiidae Maggioni, 2021

Galea, Horia R. & Maggioni, Davide, 2021, An integrative study of some species of Gonaxia Vervoort, 1993 from off New Caledonia, with the establishment of Gonaxiidae as a new family of thecate hydroids (Cnidaria: Hydrozoa), Zootaxa 5004 (3), pp. 401-429 : 404

Family Gonaxiidae Maggioni , fam. nov.

Diagnosis. Hydroids forming upright colonies of macroscopic size built up along a fascicled, simple or branched main stem. Cladia biseriate, alternating along the stem and, when present, its branches forming either simple-pinnate or multi-pinnate, planar colonies with straight stems, or pinnate cladia-bearing branches spirally arranged along a strongly geniculate stem. Division into internodes often indistinct in both stems and cladia; usually a hydrotheca per equivalent of cladial internode; on stems, two successive cladia separated by three consecutive hydrothecae, of which the proximal most is axillar; cladia borne on short stem apophyses. Hydrothecae flask-shaped to tubular, immersed for a varied degree into their corresponding internodes, free part variably projecting out- to upward, aperture distal, transverse, margin provided with three rounded cusps (two latero-adaxial, one abaxial) separated by shallow embayments, operculum composed of three triangular flaps. Gonothecae arising from the component tubes of the stems, either club-shaped and fully free above their origin, or long, tubular, partly adnate to the stem proximally and diverging distally, in all cases provided apically with a rounded, transverse aperture, broader in females than in males.