Cnidarians are perhaps the most alien-like, macroscopic animals on the planet. The word "cnidarian" means "nettle," which references most of the cnidarians' ability to sting and cause pain, somewhat similar to nettle plants. The sting is delivered by cells called cnidocytes, which fire harpoon-like structures into other organisms and inject them with venom (used for defense as well as prey-capture of fish and crustaceans). Cnidarians are classified into four known groups: the Scyphozoans (true jellyfish), Hydrozoans (hydroids, colonial jellies, and medusas), Cubozoans (box jellyfish), and Anthozoans (corals, anemones, sea fans, and sea pens). They are brainless and heartless, instead depending on specialized receptors and nerves in order to perform basic functions of the body. The oldest known cnidarian fossils date back to the Ediacaran period, approximately 580 million years ago. Though cnidarians have almost endless jelly-like forms, most of these creatures do not fossilize as well as corals, whose bodies possess hard skeletons that are more prone to mineralizing. Today they exist in a myriad of environments, from polar regions, to warm oceans, and even fresh water. Their amazing diversity has produced homes and feeding grounds for fish in the form of coral reefs and anemones, as well as the most venomous animal on the planet, the combjelly, and the largest invertebrate known, the 120 ft. long Lion's Mane jellyfish.
Click on the images below to see the incredible fossils we offer in our cnidarian selection:
Anthozoans: Coral, Sea Anemones & kin