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Did You Know?
In Did You Know? the National Geographic magazine team shares extra information we gathered to expand your knowledge of our featured subjects.

To aid in capturing prey, some ancient marine reptiles evolved features such as supersize eyes, fearsome teeth, or extremely long necks. Thalassomedon's 20-foot (6-meter) neck helped it ambush schools of fish from below. With 62 vertebrae, the neck stretched about 14 feet (4 meters) longer than a modern giraffe's, which has only seven vertebrae. But while Thalassomedon may seem like a blueprint for the Loch Ness monster, scientists say its neck probably couldn't have risen too far above the surface; buoyant underwater, its head and neck would not easily be supported in thin air. Also, writes paleontologist Michael Everhart in Oceans of Kansas: A Natural History of the Western Interior Sea, "since the eyes of a plesiosaur are located on top of the skull and are generally directed upward, the plesiosaur would almost have to turn its head upside down to look down at the water in search of prey from above the surface." Plesiosaurs like Thalassomedon had ample food below the surface, where they likely feasted on fish such as Apsopelix, which were abundant some 95 million years ago, during the late Cretaceous period. Easing into a school from below, Thalassomedon would turn its head to the side, snapping its jaws on the quarry.

—Michael Klesius and Kathy Maher