Beautiful Claws of a Tiny Water Bear: a Review and Proposal for Claw Configuration

Tardigrades in the genus Milnesium have complex double claws on each leg, which consist of two slender primary branches and two basal secondary branches. The latter usually have two or three hooks. For more than a century, taxonomists have had great difficulties evaluating the claw variation in species identification in Milnesium. This review explains the complicated story and proposes a new notation system for Milnesium claw configuration with a discussion about anterior-posterior axes on tardigrade legs.