| Summary: | The Balnibarbiinae is one of eight subfamilies of the Olenidae, a diverse family of late Cambrian to Ordovician trilobites. Balnibarbiine species occur in a relatively continuous section of deeper-water sediments exposed along the northeastern coastline of Spitsbergen, Svalbard, as well as scattered deeper-water beds in central Nevada. Results of phylogenetic analyses of the subfamily using both parsimony and Bayesian methods are consistent with a previous hypothesis based on phyletic similarity and stratigraphic range. CloacaspisFortey, 1974, is supported as monophyletic, but the support for BalnibarbiFortey, 1974, is weak, and the genus may be paraphyletic to Cloacaspis even with the reassignment of Balnibarbi ceryxFortey, 1974, to Cloacaspis. New field collections and discovery of previously undescribed material in museum and survey collections provides the basis for emended descriptions of the genus Cloacaspis, as well as Cloacaspis tesselataFortey and Droser, 1999, Cloacaspis ekphymosaFortey, 1974, and Balnibarbi erugataFortey, 1974, and expands the geographic range of the subfamily to Alaska.
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