MOSASAUR

Mosasaurs are an extinct carnivorous aquatic lizard, which are often related to modern-day monitor lizards, Gila monsters, and snakes. They existed, in what is now considered Western Europe and North America, during the Campanian and Maastrichtian age of the late Cretaceous period, between 82 and 66 million years ago. They had deep barrel-shaped bodies and lived near the water’s surface where they preyed on fish, turtles, ammonites, smaller mosasaurs, birds, pterosaurs, and plesiosaurs. The type species, M. hoffmannii, is considered the largest mosasaur ever discovered, with an estimated length of up to 56 feet from nose to tail and an estimated weight of over 20,000 pounds! Similar to snakes, mosasaur’s had jaws that could expand in order to help the animal swallow large, whole prey. Also, like a snake, mosasaurs had two sets of teeth in their upper jaws. The second set was smaller and further back, and it was these teeth that would help the mosasaur while holding on to and devouring its struggling prey. Today, it is estimated that there were over 30 different species of mosasaur to have been in existence, with the latest species, Ectenosaurus shannoni, being recently identified within the U.S. state of Alabama, as of the year 2023.

MOSASAUR FOSSIL HISTORY

Mosasaurs went extinct at the end of the Cretaceous period. Hidden below the crystal-clear waters of the Gulf of Mexico, the Chicxulub impact crater marks the site of an asteroid that struck the Earth an estimated 66 million years ago. It is widely accepted that the devastation and climate disruption from the impact was the cause of the Cretaceous–Paleogene extinction event, claiming an end to the reign of the mosasaur, as well as most other species of dinosaur. During this time, within what is now considered the North American continent, the Western Interior Seaway was the habitat of numerous types of animals, including several species of mosasaur. In fact, a number of distinct species of mosasaur have been discovered here, including the largest known to have inhabited the region, Tylosaurus. The most complete Tylosaurus fossil, which is housed at the University of Kansas Natural History Museum, measures 45 feet in length. It is estimated that this creature would have weighed over 10,000 pounds.

Interestingly, it has been documented that several Native American tribes of the Midwest United States had previously discovered and interpreted mosasaur fossils long before they were first described. Early depictions of mosasaurs have been passed down through Native American oral history, which once described the fossils as early remnants of mythological beings.

The name "mosasaur" is a conjunction of two words: 'Mosa', which stands for the Meuse River in Holland, which is the location where Mosasaurs were first described; and the word, 'Saur', or Sauros, which is the Greek word for ‘lizard’. The conjunction of these terms forms the description, “the lizard of the Meuse River”.