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A single tantulus larva was found at the abyssal depth of the Indian Ocean attached to a harpacticoid host of the family Cletodidae. It represents a new genus and species of Tantulocarida, family Basipodellidae. Its ultrastructure was studied with SEM. This genus can be easily distinguished from the other genera of Basipodellidae by the pore pattern, bilobed oral disk with strong longitudinal ridges and the posterior projection of the cephalic shield. A morphological analysis of two related families Basipodellidae and Deothertridae shows that they represent polyphyletic taxa and need further revision.

Although the naupliar and cypridiform stages of the enigmatic y‐larvae of Facetotecta have been found in the marine plankton worldwide, they still represent the last significant group of crustaceans for which the adult forms are still unknown. From a number of y‐cyprids representing different taxa from different locations, we employ scanning electron microscopy to describe fine morphological details of all external structures of this unique larval form. We document different segmentation patterns of the abdomen and presence/absence of the labrum and structural differences in the antennules, labrum, paraocular process, thoracopods, and telson lend support for the erection of several new genera as opposed to the single Hansenocaris . The data presented here emphasize the morphological limits of the genus Hansenocaris and the “bauplan” of cyprydiform larvae of Facetotecta. Although the optimum pathway is a joint analysis of both molecular and morphological characters, we use the morphological characters of y‐cyprids to align them cladistically and determine the limits of the genus Hansenocaris s.s. and describe common characters for all y‐cyprids including six pairs of the lattice organs instead five pairs considered as a ground pattern for all Thecostraca. We also determine plesiomorphic and apomorphic characters of all known y‐cyprids and separate them from other thecostracan cypridiform larvae.

A new ectoparasitic ascothoracidan species has been discovered off northern Tasman Sea at a depth of 520 m. Single female, described herein as Waginella ebonita Kolbasov and Newman sp. nov. in the family Synagogidae Gruvel, 1905, was collected on the column of crinoid Metacrinus sp. This is the first study of a new form of Waginella to be based on the extensive use of both light and scanning electron microscopy to document the fine-scale external morphology. We studied the external morphology of other two species of Waginella, W. cf. axotremata and W. sandersi utilizing SEM and compared fine structures of all congeners. The genus Waginella represents a monophyletic taxon including at least 4 species having similar and unique morphology even on the ultrastructural level. Two species, W. cf. axotremata and W. cf. metacrinicola may represent at least two complexes of species. The morphology of an attachment apparatus in all species of Waginella suggests that they remain attached to the host for a considerable period of time. The lattice organs of Waginella have a unique structure distinguishing from all Thecostraca. Waginella ebonita sp. nov. is the second species of this genus known to harbor hyperparasitic cryptoniscid isopods representing parasitic castrators.