A group of aquatic animals including jellyfish, corals, and sea anemones, characterized by stinging cells called nematocysts and radial body symmetry. They are among the most ancient animal groups on Earth.
From Greek 'knide' meaning 'nettle', referring to their stinging cells. The scientific name was established in the 19th century when biologists recognized the common features shared by these diverse stinging animals.
Cnidarians are living time capsules that have remained virtually unchanged for over 500 million years! Their stinging cells can fire faster than a bullet, and some species like the immortal jellyfish can theoretically reverse aging and live forever.
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