Thalassomedon
It had a long neck (with 63 vertebrae), a long snout, long, sharp teeth (up to 5 cm long), a short, pointed tail and four flippers, each about 1.5–2 meters (4.9–6.6 ft) long. This reptile was about 40 feet (12 m) long; its skull was about 18.7 inches (47 cm) long.