Jellyfish

• Rhizostomeae - Cassiopeidae, Catostylidae, Cepheidae, Lychnorhizidae, Lobonematidae, Mastigiidae, Rhizostomatidae, Stomolophidae
Largest jellyfish
The lion's mane jellyfish, Cyanea capillata, have long been cited as the largest known jellyfish, and are arguably the longest animal in the world, with fine, thread-like tentacles up to 36.5 m (120 feet) long (though most are nowhere near that large). They have a painful, but rarely fatal, sting.