Largest stalked jellyfish

The largest stalked jellyfish or stauromedusan is Janet's stalked jellyfish Lucernaria janetae, which has a calyx diameter of 10 cm and height of 3 cm in the living state (preserved specimens shrink and are therefore smaller). First discovered in 2003, it was formally described in 2005 and is the only species of stalked jellyfish known from the Pacific Ocean, where it lives in association with hydrothermal vents on the ocean floor. It was named after American marine biologist Dr Janet Voight, in recognition of her commitment to discovering and describing new species of deep-sea invertebrate.

Unlike other types of jellyfishes, stalked jellyfishes remain permanently attached to their substratum when adult, never becoming free-floating medusae, and their wide, tentacle-bearing upper region is referred to as the calyx.

Traditionally, they were categorized as a taxonomic order, Stauromedusae, within the taxonomic class Scyphozoa, the latter housing all true jellyfishes, but more recently their order has been reassigned to a separate taxonomic class of its own, Staurozoa, outside of but related to Scyphozoa.