Systematic affinities of Zygophylacidae (Cnidaria: Hydrozoa: Macrocolonia) with descriptions of 15 deep-sea species Author Gu, Zhangjie Author Ruthensteiner, Bernhard Author Moura, Carlos J. Author Liu, Lihua Author Zhang, Rui Author Song, Xikun text Zoological Journal of the Linnean Society 2022 Zool. J. Linn. Soc. 2022-06-17 196 52 87 http://zoobank.org/22984f44-21e0-43ab-9d46-547c8306448a journal article 133182 10.1093/zoolinnean/zlac036 f1c43083-ab5f-4130-82f0-0418e8954791 0024-4082 7035312 22984F44-21E0-43AB-9D46-547C8306448A FAMILY ZYGOPHYLACIDAE QUELCH, 1885 Diagnosis: Solitary hydrothecae arising from hydrorhiza directly, or erect, pinnate or flabellate colonies, with polysiphonic hydrocauli in most species, otherwise monosiphonic. Hydrocladia mostly arranged in one plane, alternate to subopposite. Hydrothecae mostly tubular, seldom campanulate or subuliform, with short to long pedicel, with one or two diaphragms, with or without indentation (intrathecal projections) at distal part of the hydrothecae, and with one to numerous nematothecae on hydrocauli, hydrocladia and/or apophyses of hydrocladia. Gonothecae congregate to form coppiniae on stem or its hydrocladia; coppiniae with or without defensive tubes, the latter occasionally provided with hydrothecae or nematothecae. Individual gonothecae solitary or adnate, generally elongate or ovoid, seldom flask- or carrot-shaped, apices either with a circular aperture or with one to three straight or curved short tubes. Remarks: Molecular data contributed by the present study support the genetic distinction and validity of the family Zygophylacidae ( Figs 21 , 22 ). Based on specimens examined in this study and morphological diagnoses proposed by Rees & Vervoort (1987) , Vervoort (1987) and Cornelius (1995) , both zygophylacids and lafoeids have similar tubular hydrothecae. However, they differ in the fact that nematothecae and hydrothecal diaphragms are commonly present in Zygophylacidae , but are absent in Lafoeidae ( Bouillon et al. 2006 ; this study).