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) Author Galea, Horia R. Hydrozoan Research Laboratory, 405 Chemin Les Gatiers, 83170 Tourves, France. Author Maggioni, Davide 0000-0003-0508-3987 Università degli Studi di Milano-Bicocca, Dipartimento di Scienze dell’Ambiente e della Terra, Piazza della Scienza 1, 20126 Milano, Italy. davide. maggioni @ unimib. it; https: // orcid. org / 0000 - 0003 - 0508 - 3987 & Università degli Studi di Milano-Bicocca, Marine and High Education (MaRHE) Center, 12030 Faafu Magoodhoo, Republic of the Maldives davide.maggioni@unimib.it text Zootaxa 2021 2021-07-21 5004 3 401 429 journal article 10.11646/zootaxa.5004.3.1 1175-5326 5120645 0C4DFAA3-5822-456B-916B-84A7BABEB98F Gonaxia crusgalli Vervoort, 1993 Figs 1C , 6F–G , 15 , 16 ; Table 3 Gonaxia crusgalli Vervoort, 1993: 149 , figs 18E, 20, 21A. Material examined. KANACONO, Stn. DW4744, MNHN-IK-2015-2678: a 2.8 cm high, sterile colony; GenBank: MZ 099695 (16S). Remarks. The present material, without gonothecae, is immediately recognizable as being G. crusgalli , due to the pair of fronto-dorsal spurs on its hydrothecae ( Fig. 6F, G ), a character not met with in any of its congeners. As with Vervoort (1993) , the presence of a basal foramen communicating with the hydrothecal lumen could be noted (their distal tips are always closed in the available specimen), but no traces of coenosarc investing their own lumina could be observed, making their role uncertain. Although no reports of branched cladia are available ( Vervoort 1993 ), aberrant branches were seen in the material at hand: 1) in one instance, a short branch is given off from within the proximal most hydrotheca; 2) in another case, an equally short branch takes the place of one of the lateral spurs of a proximal hydrotheca on the original cladium. For a thorough description of this species, refer to Vervoort (1993) . Bathymetric distribution. Between 255–310 m ( Vervoort 1993 ; present study).