Water Bears belong to a lesser known phylum of invertebrate animals, the Tardigrada. The first tardigrades were discovered by Goetz in 1773. Over 400 species have been described since that time.
Tardigrades grow only to a size of about 1mm, but they can easily be seen with a microscope. Tardigrade bodies are short, plump, and contain four pairs of lobopodial limbs (poorly articulated limbs which are typical of soft bodied animals). Each limb terminates in four to eight claws or discs. They lumber about in a slow bear-like gait over sand grains or pieces of plant material.