Abstract
This paper is an invited contribution to the Zootaxa series ‘Animal biodiversity: An outline of higher-level classification and survey of taxonomic richness.’ (Zhang 2011). This series pertains to living biodiversity and the species numbers given here are more or less derived from the World Register of Marine Species (WoRMS), for which the two authors of this paper are listed as editors (PEB hands-on editor; DPG advisory editor). Thus circumscribed, Bryozoa includes 3 classes, 4 orders, 187 families, 808 genera and 5869 species [Phylactolaemata 86 species, Stenolaemata 543 species, Gymnolaemata 5240 species (Ctenostomata 319 species, Cheilostomata 4921 species)]. Although all Phylactolaemata and several species of Ctenostomata are freshwater organisms, the full list of bryozoan species is accessible on WoRMS. The WoRMS list must be understood to be provisional, owing to the need for taxonomic revisions of many genera. Nevertheless, even if not all species in the list are accurately attributed to genera, the names represent operational taxonomic units (OTUs) that are indicative of living species diversity as known to date.