Sharks (superorder Selachimorpha) are fish with a full cartilaginous skeleton and a highly streamlined body.
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Atlantic White Shark Conservancy
— José Truda Palazzo, Jr. (@TrudaOceans) February 7, 2017
What’s older than sharks? Almost nothing. Sharks have been swimming in the ocean for more than 400 million years. They predate practically everything that has a spine, including humans and dinosaurs.