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Six new marine species of the silica-scaled heterotrophic genus Thaumatomastix are formally described: two were found in Canadian Atlantic Ocean coastal waters (T. asymmetrica sp. nov. and T. sablensis sp. nov.) and four from Canadian Pacific Ocean coastal waters (T. inornata sp. nov., T. multipora sp. nov., T. gwaii sp. nov. and T. curvata sp. nov.). These discoveries more than double the number of known marine species of this genus from four to ten. The scale structures of all differ significantly from those of previously known species and therefore warrant erection as new species. Amended descriptions of two previously little-known freshwater species (T. triangulata and T. nigeriensis) are provided based on specimens found in freshwater ponds and lakes in Ontario, Lanada, and provide evidence refuting the recent published proposals to transfer T. triangulata back to the photo-autotrophic genus Chrysosphaerella and to transfer T. nigeriensis to the related thaumatomonad genus Reckertia. Until now, all known species of Reckertia (including several taxa previously classified in Thaumatomastix) were marine. This paper describes the first known freshwater species of Reckertia (R. hindoni sp. nov.) found in two separate Ontario ponds. The similarities and differences among many of the marine and freshwater species of Thaumatomastix suggest a common ancestor but significant evolutionary divergence over time and space. [ABSTRACT FROM PUBLISHER]

Near-shore benthic sediment samples collected at low tide from the western Atlantic Ocean (Sable Island, Nova Scotia, Canada) and the eastern Pacific Ocean (Haida Gwaii (Queen Charlotte Islands), British Columbia, Canada) were searched for little-known species of the rhizarian (Cercozoa) genera Pinaciophora, Rabdiaster and other related rotosphaerids. Several representatives with complete investitures of silica-scales (the structure of which is taxonomically diagnostic) were studied by transmission and scanning electron microscopy. The validity of the genus Pinaciophora (sensu Penard, 1904) as defined by a single type of plate-scale only, was strengthened by the discovery of Pinaciophora rubicunda and of another previously undescribed entity, both of which lacked spine-scales. Several earlier reports of loose scales from marine habitats, and erroneously identified as the freshwater P. fluviatilis, might be assigned to P. marina sp. nov. The new genus Thomseniophora was erected to include all ‘Pinaciophora' previously known to produce spine-scales and seven new taxa were described. Six other little-known species of Thomseniophora, Pinaciophora and Rabdiaster were described from the Canadian west coast (Pacific Ocean) including one new species of Pinaciophora. The addition of Thomseniophora brings the number of genera assigned to the Rotosphaerida to six: Pinaciophora, Thomseniophora, Rabdiaster, Rabdiophrys and Pompholyxophrys. The presence of several apparently closely related taxa in the same collection (same location and sampling date) strengthens the conclusion that relatively small differences in the morphology of their siliceous scales were more likely caused by genetic differences than by environmental influences. [ABSTRACT FROM PUBLISHER]