沧龙科（Mosasauridae），Mosa在拉丁语意为荷兰的默兹河（Meuse river），sauros在希腊文意为蜥蜴。沧龙类是种如蛇般弯曲的海生爬行动物。第一个沧龙类化石在1780年于默兹河流域的马斯垂克市发现。有些专家认为这些凶残的海中掠食者，与蛇关系密切，因为牠们的颌部、头颅骨结构上极度相似。沧龙类并非恐龙，属于鳞龙类，鳞龙类是身上覆盖者重叠鳞片的爬行动物。沧龙类从早白垩纪的半水生有鳞目动物演化而来，例如现代巨蜥的近亲崖蜥科（Aigialosauridae）。在白垩纪的最后2000万年期间（土仑阶到马斯垂克阶），沧龙类成为优势海中掠食者，而鱼龙类灭绝，上龙类与蛇颈龙类衰退。星海沧龙

Mosasaurs (from Latin Mosa meaning the 'Meuse river', and Greek σαύρος sauros meaning 'lizard') 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. 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 decline of plesiosaurs, mosasaurs became the dominant marine predators. They became extinct as a result of the K-T event at the end of the Cretaceous period, approximately 66 million years ago.