Reconstruction of the giant filter feeder, scooping up a plankton cloud. Aegirocassis benmoulae was one of the biggest arthropods that ever lived. Family members include today's insects, spiders and lobsters. Marianne Collins/ArtofFact hide caption

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Think Man-Sized Swimming Centipede — And Be Glad It's A Fossil

This sea monster swam Earth's seas about 480 million years ago and was the biggest creature of its day, scientists say.

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Sternman Scott Beede returns an undersized lobster while checking traps in Mount Desert, Maine. Robert F Bukaty/AP hide caption

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