the back spine of a extinct mosasaurus lemonnieri, a aquatic lizard that lived during the cretaceous period in europe and america

america ancient animal animals aquatic back background bone bones cretaceous europe european evolution extinct fish fishes fossil fossils geologic geological geology historical history ichthyology jurassic lemonnieri life limestone lived lizard marine mosasaurus museum old paleontology period prehistoric prehistorical prehistory remain remains research science skeleton specie species spine that time zoology