Mosasaurs - (pronounced MOES-ah-SAWR)

Mosasaurs ('Meuse river' in the Netherlands and Greek sauros meaning 'lizard') were giant, serpentine (snake-like) marine reptiles.

They were not dinosaurs, but were related to snakes and monitor lizards.

 

Mosasaurs were powerful swimming reptiles that had adapted to living in shallow seas. These carnivores (meat-eaters) still breathed air. They were a short-lived line of reptiles that went extinct during the K-T extinction, 65 million years ago.

Some Mosasaurs include the Mosasaurus (40-59 feet long with sharp teeth from the North Atlantic), Platecarpus, Tylosaurus (33-40 feet long with sharp teeth, from the North and Plotosaurus, Clidastes, Plioplatecarpus and Globidens (with flat teeth for crushing shellfish).

The first Mosasaur discovered, Mosasaurus hoffmani, was found in the Netherlands in 1780. These predators evolved from semi-aquatic squamates known as the aigialosaurs, close relatives of modern-day monitor lizards, in the early Cretaceous Period.

During the last 20 million years of the Cretaceous Period, with the extinction of the last ichthyosaurs and the decline of the Cretaceous plesiosaurs and pliosaurs, mosasaurs became the dominant marine predators. They were well-adapted to living in the warm, shallow epicontinental seas prevalent during the Late Cretaceous Period.

Mosasaurs had a body shape similar to that of modern-day monitor lizards (varanids), but were more elongated and streamlined for swimming. Their long head had very pointed, powerful jaws with many sharp teeth. Mosasaurs had four short, paddle-like limbs adapted to life in the water. A long tail, perhaps finned, completed its serpentine body. Their limb bones were reduced in length and their paddles were formed by webbing between their elongated digit-bones. Their tails were broad and supplied the locomotor power.

This method of locomotion may have been similar to that used by the conger eel or sea snakes today. The animal may have lurked and pounced rapidly and powerfully on passing prey, rather than hunting for it. Mosasaurs had a double-hinged jaw and flexible skull (much like that of a snake), which enabled them to gulp down their prey almost whole.

Mosasaurs were carnivores, hunting and eating fish, turtles, mollusks and shellfish. Fossil ammonites have been found with many telltale Mosasaur toothprints in their shells, indicating that Mosasaurs repeated bit these hard-shelled animals in order to break their shell and get to the soft meat.

The various mosasaurs went extinct during the K-T extinction, 65 million years ago.

Mosasaurs were so well adapted to living in shallow epicontinental seas that they gave birth to live young, rather than return to the shore, as sea turtles do, to lay eggs.

The first fossil remains were discovered at the Meuse river about 1780.

Scientific Classification:

Kingdom: Animalia

Phylum: Chordata

Class: Sauropsida

Order: Squamata

Suborder: Lacertilia

Family: Mosasauridae