Definition of families, subfamilies, genera and subgenera of the Eutardigrada, and keys to their identification

The systematic arrangement of the Eutardigrada has radically changed since 1969 due to the new evaluation of characteristics of the claws and of the bucco-pharyngeal apparatus and the use of some characters overlooked before. After that date, as a consequence, four new families and 40 genera have been instituted. Given the changes and number of novelties, the authors have updated the definitions of all familial and generic taxa and have provided keys to aid identification.