During the time of the dinosaurs, the seas were ruled by giant marine reptiles. You can learn about some of them, the plesiosaurs, in Ranger Rick Zoodinos. But what other reptiles lived in the oceans, and what made them different from the plesiosaurs?

Ichthyosaurs were one of the earlier groups of marine reptiles during the time of the dinosaurs, or Mesozoic Era—they evolved during the Triassic Period (the time of the earliest dinos) and survived well into the Cretaceous (the end of the dinosaurs). These reptiles were fish-like in appearance—their name even means “fish lizard.” Plesiosaurs thrived during the middle of the Mesozoic Era, during the Jurassic Period. These creatures came in many shapes and sizes, but they often had a “Nessie”-like appearance, with long necks and flippers. Mosasaurs were late on the scene—they didn’t develop until the Cretaceous Period, but they came to dominate the oceans. They were more lizard-like in appearance, and they could be huge—this one, nicknamed “Bruce” is on display at a museum in Canada. It’s 43 feet long!

Photo by Mike Beauregard

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