Prehistoric Dinosaur Hub on Instagram: "Mosasaurs were ancient marine reptiles that lived during the late Cretaceous period, around 70 to 66 million years ago. These fascinating creatures were not dinosaurs but rather a group of large, carnivorous reptiles. Here are some key facts about mosasaurs: Impressive Size: Mosasaurs could reach impressive sizes, with some species growing up to 50 feet (15 meters) in length. They were apex predators of their time, ruling the ancient seas. Powerful Swimmer