The bryozoan families Sclerodomidae, Bifaxariidae, and Urceoliporidae and a novel type of frontal wall

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Abstract
The type- and other genera of the bryozoan families Bifaxariidae, Sclerodomidae, and Urceoliporidae have been examined. Most bifaxariids, including Bifaxaria, Diplonotos, and two new genera, Raxifabia and Xenicobrium, are uniquely characterised by a double frontal-wall arrangement not previously described — i.e., a primary spinocyst overlaid by paired umbonuloid wall elements with a median longitudinal suture between. Domosclerus (= Sclerodomus sensu Harmer), and two other new genera, Aberrodomus and Smithsonius, lack a spinocyst. On the basis of zooidal and frontal-wall morphology, the superfamily Bifaxarioidea established by d’Hondt (1985) is justified. Sclerodomids, comprising Sclerodomus, Cellarinella, Systenopora, and Cellarinelloides, are strictly umbonuloid, with a uniformly porous (though centrally imperforate) frontal wall and no underlying spinocyst. The Sclerodomidae is here included in the superfamily Umbonuloidea Canu. Excluded from the Sclerodomidae is Pseudosclerodomus d’Hondt and Schopf, which, though also umbonuloid, is provisionally regarded here as an exochellid genus. The Urceoliporidae, comprising Urceolipora and Reciprocus n. gen, are cryptocystidean and may be included in the Schizoporelloidea Jullien. Bifaxaria vagans Thomely is made the type of a new cryptocystidean genus, Vix, and monotypic family, Vicidae (Schizoporelloidea).