They have stolonal hydroid colonies, and their medusae are benthic and can crawl across the sediment; in many species they have lost the ability to swim however.

[1] Several members of this lineage were formerly considered a separate family Eleutheriidae.

[2] The hydranths have a circular mouth surrounded by a single whorl of adhesive tentacles which each bear a little knob at the tip; in some Cladonematidae an aboral whorl of thread-like unknobbed tentacles is also present.

Cladonematidae medusae have a various extend of nematocysts around their umbrellar margin, varying between a continuous dense ring to none at all among the species.

The mouth is bordered either with clusters of nematocysts, or with short lips of tissue, or fringed with branching tentacles.