Mosasaurus

Mosasaurs represent a group of extinct marine reptiles. They were strong swimmers with long, slender bodies similar to snakes (although they had four limbs, all finned, and probably a fin on the tail), they ate fish, turtles, sea urchins, crustaceans and molluscs. The smallest known mosasaur was about 3 meters long, but the largest reached up to 18 meters.

Mosasaurs were not dinosaurs but “lepidosaurs” (i.e. reptiles with overlapping scales), a group that includes snake lizards.

It is believed that mosasaurs evolved from “aigialosaurs”, which were semi-aquatic lizards that lived in the Cretaceous period, ancestors of “guardian lizards”, such as the monitor lizard.

In 1869, Edward D. Cope suggested that mosasaurs and snakes share a common marine ancestor. This idea was based on the similarities observed in the mandibles of mosasaurs and snakes, the reduced limbs, and the fact that mosasaurs could have moved in a similar way to snakes. In 1990, the discovery of fossils of early snakes with vestigial limbs in marine sediments appeared to provide support for this hypothesis. However, recently, other fossils of early snakes have been found showing them as animals with hind limbs and an apparently burrowing lifestyle, so some doubt has arisen about the idea that mosasaurs and snakes are close relatives.

Mosasaurs appear to have evolved during the early part of the Cretaceous period, probably around 96 million years ago. In the last 20 million years of the Cretaceous, after the extinction of the ichthyosaurs, they became the dominant predators. However, all mosasaurs died during the mass extinction at the end of the Cretaceous period.

The first publicized discovery of a mosasaur fossil dates back to 1778. A fossil was found in a limestone quarry, in 1780, near the town of Masstricht, Holland. However, it was not named or scientifically described for a long time and the name that was later given, Mosasaurus, means “Meuse Lizard”, and refers to the nearby Meuse River. Subsequently, other fossils that had previously been found in the same area, and had been exhibited around 1770, they were identified as mosasaurs. Since then, other mosasaur fossils have been found in many other countries around the world, including Australia, Canada, Denmark, Mexico, New Zealand, Peru, Sweden and the United States, as well as in Africa and off the coast of Antarctica.