Mosasaurus fossil map
Where fossils of Mosasaurus have been found, shown on the Earth as it looked about 66 million years ago and on today’s map.
Dots are fossil collections recorded in the Paleobiology Database. The “then” view moves today’s fossil sites back to their positions 66 million years ago (the time slice nearest the median age of the fossils) using the Merdith et al. (2021) plate model; positions are approximate. Open on the timeline map →
| Group | Mosasaurs |
|---|---|
| Lived | 100.5–61.66 million years ago (Cenomanian to Danian) |
| Periods | Cretaceous, Paleogene |
| Family | Mosasauridae |
| Named by | Parkinson 1822 |
| Fossil records | 130 occurrences at 101 locations (PBDB) |
| Found in | United States, Syria, UK, Morocco, New Zealand, Poland, Netherlands, Belgium, Spain, Russian Federation … |
| Rock formations | txn:38049, Navesink, Hornerstown, Severn, Pierre Shale, Bearpaw Shale |
About Mosasaurus
Mosasaurus (; "lizard of the Meuse River") is the type genus (defining example) of the Mosasauridae, an extinct group of aquatic squamate reptiles. It lived from about 82 to 66 million years ago during the Campanian and Maastrichtian stages of the Late Cretaceous. The genus was one of the first Mesozoic marine reptiles known to science—the first fossils of Mosasaurus were found as skulls in a chalk quarry near the Dutch city of Maastricht in the late 18th century, and were initially thought to be crocodiles or whales. One skull discovered in 1778 was famously nicknamed the "great animal of Maastricht". In 1808, naturalist Georges Cuvier concluded that it belonged to a giant marine lizard with similarities to monitor lizards but otherwise unlike any known living animal. This concept was revolutionary at the time and helped support the then-developing ideas of extinction. Cuvier did not designate a scientific name for the animal; this was done by William Daniel Conybeare in 1822 when he named it Mosasaurus in reference to its origin in fossil deposits near the Meuse River. The exact affinities of Mosasaurus as a squamate remain controversial, and scientists continue to debate whether its closest living relatives are monitor lizards or snakes.
Text in “About” is quoted from the Wikipedia article Mosasaurus (revision 1381031127), licensed under CC BY-SA 4.0; introduction excerpted verbatim, formatting removed. Ages, family, authority and fossil records: Paleobiology Database, accessed 22 October 2026. Ages are those of the rock layers the fossils were found in. Wikidata: Q312131.
