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.
Paleontology in Kansas
In 1870, O. C. Marsh led a paleontological expedition into the western United States on behalf of Yale University. Late in the November of that year they visited the area around Fort Wallace. They spent several days prospecting for fossils in modern Wallace and Logan Counties along the banks of the Smoky Hill River. Persevering against cold weather, they made several finds. One was the nearly complete skeleton of the mosasaur "Clidastes" that took four days to excavate. Among the fossils discovered by Marsh's crew in western Kansas were the far ends of two pterosaur wing metacarpals. These were the first scientifically documented fossils of the pterosaur that would later be named "Pteranodon". This formal naming occurred six years later, in 1876.