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The Mesozoic Sea

ancient sea creatures frolic in the waves
Smithsonian Institution

Before large mammals, reptiles ruled the ocean. During the Mesozoic, the time period when dinosaurs roamed on land, many of these large creatures were the top predators in the ocean food chain and fed on fish, cephalopods, bivalves, and even one another. Pterosaurs, flying reptiles, were also a key part to Mesozoic ocean ecosystems because they also ate fish.