Phylogeny of the sponge family Polymastiidae was reconstructed based on 25 morphological characters. Twenty-one polymastiid species and three suberitid species, Suberites domuncula as outgroup, Aaptos aaptos and A. papillata as sister groups, were included in the analyses. The reconstructions were done in PAUP* running heuristic search with the parsimony criterion. We analysed three possible evolutionary scenarios based on three alternative interpretations of the body plan of Quasillina brevis and Ridleia oviformis: first-Ridleia possesses aquiferous papillae whereas Quasillina lacks them, second-both genera lack papillae and third-the body in both genera is a single hyperdeveloped papilla. All three scenarios excluded the secondary loss of the papillae in the polymastiid evolution. Scenario 2 also excluded the secondary loss of the regular choanosomal skeleton, while scenario 1 assumed its loss in Ridleia and scenario 3 admitted its loss in both Ridleia and Quasillina. We prioritised scenario 2 due to its maximal parsimony and rescaled consistency index and subsequently favoured the clustering of Ridleia and Quasillina separately from the monophyletic polymastiid clade. In all three scenarios Pseudotrachya hystrix clustered separately from other polymastiids in agreement with the molecular evidence, and thus the exclusion of Pseudotrachya from Polymastiidae was proposed. The relationships between A. papillata, Tentorium semisuberites, Polymastia uberrima, the clade Weberella bursa ? Polymastia boletiformis and the main polymastiid clade were ambiguous. Meanwhile, all scenarios showed the non-monophyly of Polymastia and Aaptos. Our hypotheses should be tested by reconstructions based on larger taxon sampling of hadromerid species and larger sets of morphological and molecular characters before any ultimate taxonomic decisions are taken.Electronic supplementary material The online version of this article (

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Polymastiidae (Porifera: Demospongiae) of the Nordic and Siberian Seas are revised and compared with the related species of the North Atlantic based on the morphological data from the type and comparative material and the molecular data from fresh samples. Twenty species from six polymastiid genera are recorded. Two species, Polymastia svenseni from Western Norway and Spinularia njordi from the Norwegian Sea, are new to science. One species, Polymastia andrica, is new to the Nordic Seas and two species, Polymastia cf. bartletti and P. penicillus, are new to the Scandinavian Coast. Distribution of the polymastiids in the North Atlantic and Arctic is discussed and the allegedly wide distribution of Spinularia sarsii and S. spinularia is questioned.

All polymastiid sponges displaying ornamented exotyles are reviewed and their morphological affinities are reconsidered. The study embraces all known species of Proteleia, Sphaerotylus, Trachyteleia and Tylexocladus as well as several species of Polymastia. A new genus, Koltunia, is established for the Antarctic species Proteleia burtoni based on the unique shape of distal ornamentations of its giant exotyles and on the absence of a spicule palisade in its cortex, a rare feature among the polymastiids. Three new species of Sphaerotylus are described -S. renoufi from the British Isles, S. strobilis from South Africa and S. tjalfei from West Greenland. Transfer of one New Zealand species from Polymastia to Proteleia and of one Chilean species from Polymastia to Sphaerotylus is proposed. The present study provides a background for future integrative phylogenetic analyses based on comprehensive molecular and morphological datasets which should reveal the natural relationships between the polymastiid taxa.

All species of Vosmaeria are re-described using type and additional material. The phylogenetic relationships between Vosmaeria ssp. and other demosponge taxa are reconstructed based on 28S-rDNA sequences analyses. V. crustacea, the type species, is widely distributed in the NE Atlantic and characterized by a thinly encrusting growth form, the location of ostia and oscula exclusively on papillae, a dense and firm ectosomal skeleton, the absence of subectosomal aquiferous cavities and the blunt distal tips of tylostyles. Hydrochemical conditions may account for the smaller spicule size of the White Sea population compared to those in the North and Barents Sea. V. reticulosa, known from the Chilean and Peruvian coasts, is distinguished by a massive growth form, a reticulated ectosomal skeleton, the absence of papillae, the scattering of ostia and oscula over the surface, the presence of subectosomal cavities and the acerate distal tips of tylostyles. V. levigata, known exclusively from the English Channel, shares the absence of papillae and the acerate distal tips of tylostyles with V. reticulosa, but the only surviving material consists of dissociated spicules slides, and consequently its status remains unclear. On the basis of substantial morphological differences we propose to split Vosmaeria into two monospecific genera – Vosmaeria, with type species V. crustacea, and Johannesia gen. nov., with type species V. reticulosa. Both genera clearly belong to Halichondriidae based on the tangential arrangement of the ectosomal skeleton, the presence of oxeas. Molecular phylogenetic analyses support a split into two genera and confirm the classification of both within the Halichondriidae.