Liopleurodon was a large carnivorous marine reptile (more than 20 feet in length) that lived during the Middle Jurassic Period (160-155 million years ago) in a shallow sea that once covered what is now Europe. Unlike the more familiar plesiosaurs like Elasmosaurus, which had small heads and a long neck, Liopleurodon had a huge head and short neck. History: Liopleurodon was first discovered by the French paleontologist Henri Sauvage in 1873. All he found were teeth, but they were very distinctive in lacking ridges or serrations that are normally seen on large fossil reptile teeth. Sauvage knew that he had a new animal, and named it Liopleurodon, referring to the smooth sides of the teeth. Scientific Name: Liopleurodon, meaning smooth-sided tooth. Many large reptiles had distinct ridges or serrations on their teeth, but Liopleurodon was distinct in totally lacking these features. Characteristics: Liopleurodon belonged to a special branch of plesiosaurs called pliosaurs.