Typhlotanaidae Sieg, 1984, is one of the most diverse Tanaidacea families from deep-sea waters. Its diversity is underestimated, and evolutionary relationships within the family remain mostly unknown. Deep-sea typhlotanaids collected from 23 sites across the Kuril-Kamchatka Trench and nearby waters were studied using an integrative taxonomy approach, combining morphological and genetic data (i.e., the mitochondrial subunit I of the cytochrome oxidase (COI) and the 18S rDNA nuclear gene). One new species of Typhlamia and two new species belonging to two new genera are described, significantly increasing the known diversity of typhlotanaids from the NW Pacific. The molecular phylogeny obtained, despite being preliminary results, was congruent with morphological data and supports the monophyly of different groups such as the ‘short-bodied’ forms (represented by Ty. cornutus and Ty. eximius) or the ‘collar’ forms (e.g., Ty. variabilis and Torquella). Molecular data confirm the non-monophyly of Typhlotanais species. Finally, the new typhlotanaid taxa seem to have distinct bathymetric distribution and ecological requirements, but further data on environmental factors and species abundances are still needed.

A new family of paratanaoidean Tanaidacea, the hamatipedids, formerly part of the Typhlotanaidae, is established to accommodate three genera (Hamatipeda and two new). Deep-sea hamatipedids collected from four sites in the Atlantic (Argentine and Guiana basins) and 14 sites from the Southeast coast of Australia were studied using a taxonomic approach combining morphological and morphometric data. Four new species of Hamatipeda and one of a new genus are described from different deep-sea areas of the Atlantic and Pacific oceans. Hamatipeda sima originally classified within Hamatipeda, is transferred to a new genus. We observed that several morphometric characters (i.e., length of the last two pereonites) in different life-stages of one of the new Hamatipeda species (neuter, manca-2, and manca-3) are correlated with the total body length (TBL). Applying a morphometric approach, we aimed: (1) to identify those ontogenetic-dependent characters, and (2) to detect the characters, which can be used in discrimination of Hamatipedidae species, regardless their life-stage.

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Re-examination of historical collections allowed us to resolve the taxonomic status of Typhlotanais sandersi Kudinova-Pasternak, 1985, originally described based on a single specimen from Great-Meteor Seamount. The holotype of this species was considered lost and the species redescribed based on a second specimen from the type locality by Błażewicz-Paszkowycz (2007a), who placed Ty. sandersi on a newly established genus Typhlamia. Thorough morphological analysis of Typhlamia and Typhlotanais species and recently obtained genetic data of typhlotanaids from N Atlantic and NW Pacific waters allow us to conclude that the redescription of Ty. sandersi by Błażewicz-Paszkowycz (2007a) was based on a wrongly labelled specimen that, rather than a type of Ty. sandersi, represents in fact a new species of Typhlamia. The morphological comparison of the type species of Typhlotanais (Ty. aequiremis) with all ‘long-bodied’ typhlotanaid taxa with rounded pereonites margins (i.e., Typhlamia, Pulcherella, Torquella), and the use of genetic evidence, support the establishment of a new genus to accommodate: Ty. sandersi, Ty. angusticheles Kudinova-Pasternak, 1989, and a third species from N Atlantic waters, that is described here for the first time. Current knowledge on ‘long-bodied’ typhlotanaids with rounded pereonites is summarised and a taxonomical key for their identification provided.