Mosasaurs are an extinct group of large marine reptiles.
Their first fossil remains were discovered in a limestone quarry at Maastricht on the Meuse in 1764.
During the last 20 million years of the Cretaceous period, 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.
Fossils are named from the Latin word fossus which literally means having been dug up. They are the preserved remains or traces of animals plants and other organisms from the remote past.
A fossil normally preserves only a portion of the deceased organism usually that portion that was partially mineralised during life such as the bones and teeth of vertebrates or the chitinous exoskeletons of invertebrates.
