The tanaidaceans are a group of around 1,500 known species of mostly small (0.5 to 2 cm long) Peracarida that occur worldwide. They are mainly marine and benthic (bottom-dwelling), but a handful of species live in brackish or nearly fresh water. They often live in burrows or tubes and are known from ocean depths ranging from coastal (1 to 2 m) to around 9000 m. Many are suspension feeders, but some are detritivores or predators.
classified into 35 families
(Brusca and Brusca 2003; Kakui et al. 2011 and references therein)
Kakui et al. (2011) analyzed phylogenetic relationships within Tanaidacea using data from the 18S
An excellent online source on the Tanaidacea is Gary Anderson's Peracarida Taxa and Literaturewebsite.