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.
History of paleontology
In 1808, Cuvier identified a fossil found in Maastricht as a giant marine reptile that would later be named "Mosasaurus". He also identified, from a drawing, another fossil found in Bavaria as a flying reptile and named it "Pterodactylus". He speculated, based on the strata in which these fossils were found, that large reptiles had lived prior to what he was calling "the age of mammals". Cuvier's speculation would be supported by a series of finds that would be made in Great Britain over the course of the next two decades. Mary Anning, a professional fossil collector since age eleven, collected the fossils of a number of marine reptiles from the Jurassic marine strata at Lyme Regis. These included the first ichthyosaur skeleton to be recognized as such, which was collected in 1811, and the first two plesiosaur skeletons ever found in 1821 and 1823. Many of her discoveries would be described scientifically by the geologists William Conybeare, Henry De la Beche, and William Buckland. It was Anning who observed that stony objects known as "bezoar stones" were often found in the abdominal region of ichthyosaur skeletons, and she noted that if such stones were broken open they often contained fossilized fish bones and scales as well as sometimes bones from small ichthyosaurs. This led her to suggest to Buckland that they were fossilized feces, which he named coprolites, and which he used to better understand ancient food chains.