Mosasaur
Mosasaurs (from Latin "Mosa" meaning the 'Meuse river', and Greek σαύρος "sauros" meaning 'lizard') are an extinct group of large marine reptiles containing 38 genera in total. Their first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764. Mosasaurs probably evolved from an extinct group of aquatic lizards known as aigialosaurs in the Early Cretaceous. During the last 20 million years of the Cretaceous period (Turonian-Maastrichtian ages), with the extinction of the ichthyosaurs and pliosaurs, mosasaurs became the dominant marine predators. They became extinct as a result of the K-Pg event at the end of the Cretaceous period, about 66 million years ago.
Timeline of mosasaur research
By this time the first mosasaur fossils from the United States were discovered by the Lewis and Clark expedition, and the first remains in the country to be scientifically described were reported slightly later from New Jersey. This was followed by an avalanche of discoveries by the feuding Bone War paleontologists Edward Drinker Cope and Othniel Charles Marsh in the Smoky Hill Chalk of Kansas. By the end of the century a specimen of "Tylosaurus" would be found that preserved its scaley skin. Later Samuel Wendell Williston mistook fossilized tracheal rings for the remains of a fringe of skin running down the animal’s back, which subsequently became a common inaccuracy in artistic restorations.