About 13,000 species were extinct as documented in fossil record

All free-living. Superficially resembles jellyfish in the Cnidaria phylum, but possesses 8 rows of cilia arranged in stacks of combs (known as comb plates or ctenes) for locomotion. With the exception of members from the Beroidea order which lack tentacles, and Haeckelia rubra which possesses stinging cells, all other species possess colloblast cells which secrete a glue-like substance to capture preys. Exclusively marine.