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MOSASAURS

Tylosaurs (including Mosasaurus and Hainosaurus) were the largest mosasaurs. This subfamily of mosasaurs lived in the seas during the late Cretaceous period.

(pronounced MOES-ah-SAWR) Mosasaurs were giant, serpentine (snake-like) marine reptiles. They were not dinosaurs, but were related to snakes and monitor lizards. Mosasaurs were powerful swimmers, 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 ft. feet=12.5-17.6 m long with sharp teeth from the North Atlantic), Platecarpus, Tylosaurus (33-40 feet=10-12.3 m long with sharp teeth, from the North and South Atlantic), Plotosaurus, Clidastes, Plioplatecarpus, and Globidens (with flat teeth for crushing shellfish). The first Mosasaur discovered, Mosasaurus hoffmani, was found in the Netherlands in 1780.

ANATOMY
Mosasaurs were powerful swimmers that had a long, streamlined body. The 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.

Mosasaurs probably had scaly skin; fossil impressions of scales were found near the bones of Plotocarpus, showing a snake-like skin.

WHEN THE MOSASAURS LIVED
The various mosasaurs lived during the late Cretaceous period, going extinct during the K-T extinction, 65 million years ago.

BREATHING
Although Mosasaurs lived their lives in the seas, they still needed to breathe air and had to surface periodically in order to breathe.

DIET
Mosasaurs were carnivores; they hunted and ate 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.

LOCOMOTION
Mosasaurs were powerful swimmers who spent their entires lives in the seas. Mosasaurs probably swam by moving their long body in a snake-like way, also using their finned tail to propel them forwards. They steered with small, webbed feet.

THE NAME MOSASAUR
The name Mosasaur means "Meuse lizard," they were named for the Meuse river in Holland, near the underground limestone mine where Mosasaur fossils were first found.

DISCOVERY OF FOSSILS
Mosasaur fossils have been found in Europs and North America (and a few in Africa and Israel).

CLASSIFICATION
Mosasaur were reptiles, but not dinosaurs. They are:

• Vertebrates
• Tetrapods
• Diapsids - these include all the reptiles (except turtles) and birds. They are distinguished by having two holes in the rear upper part of their skulls and two holes behind the eyes.
• Order Squamata - which includes lizards and snakes
• Family Mosasauridae - Mosasaurs
  • Subfamily Mosasaurinae long-bodied mosasaurs (Gervais, 1853) - including the genera Mosasaurus (Conybeare, 1822), Clistades (Cope, 1868), Liodon (Owen, 1840), Batrachiosaurus (Harlam, 1842), Amphekepubis (Mehl, 1929), Plotosaurus (Camp, 1951), Goronyosaurus (Azzaroli, de Guili, Ficcarelli & Torre, 1972), Globidens (Gilmore, 1912), Carinodens (Thurmond, 1969), Moanasaurus (Wiffen, 1980)
  • Subfamily Plioplatecarpinae short-bodied mosasaurs (Dollo, 1884) - including the genera Pliplatecarpus (Dollo, 1882), Platecarpus (Cope, 1869), Holcodus (Gibbes, 1850), Sironectes (Cope, 1840), Holosaurus (Marsh, 1880), Ancylocentrum (Schmidt, 1929), Baptosaurus (Marsh 1870), Dollosaurus (Yakovlew, 1901), Prognatosaurus (Dollo, 1889), Igdamanosaurus (Lingham-Soliar, 1991), Halisaurus (Marsh, 1869), Prognathodon, Selmasaurus, Yaguarasaurus, Plesiotylosaurus (Camp, 1942)
  • Subfamily Tylosaurinae enormous, short-bodied mosasaurs with abony, toothless snout extension (Williston, 1897) - including the genera Tylosaurus (Marsh, 1872), Macrosaurus (Owen, 1859), Lesticodus (Leidi, 1859), Nectoportheus (Cope, 1868), Hainosaurus (Dollo, 1885), Taniwhasaurus (Hector, 1874)

THE MOSASAUR GENUS MOSASAURUS
Mosasaurus was a mosasaur that was up to 40-59 ft. feet (12.5-17.6 m) long. Mosasaurus had four paddle-like limbs on a long, streamlined body and a long, powerful tail. The large head had huge jaws (up to 4.7 ft =1.45 m long) with many teeth. The jaws could open about 3 feet (1 m). The lower jaw is loosely hinged to the skull with a moveable joint on each side (behind the teeth). This loose joint let it swallow huge prey, like some snakes. They hunted fish, turtles, mollusks, and shellfish. It Mosasaurus lived in the North Atlantic Ocean. Mosasaurus maximus found in Onion Creek, Texas, USA. It was 30 foot (9 m) long and its tail was about 12 ft (3.7 m) long. This huge reptile was discovered in 1934 by University of Texas geology students Clyde Ikins. The first Mosasaur, Mosasaurus hoffmani, was found in the Netherlands in 1780. It was named in 1822 by W.D. Conybeare. Mosasaurs are related to modern-day monitor lizards.

THE MOSASAUR GENUS TYLOSAURUS
(pronounced TIE-low-SAWR-us) Tylosaurus (meaning "swollen lizard") was a mosasaur that was from 33-40 feet (10-12.3 m) long and had long, sharp teeth. It ate fish (possibly including sharks), other Mosasaurs, and birds. Fossils have been found in America (Kansas) and New Zealand.

THE MOSASAUR GENUS HAINOSAURUS
Hainosaurus was a huge mosasaur that was about 50 feet (15 m) long. This is the largest mosasaur yet found. They had sharp teeth and ate fish and squid. Fossils have been found in Europe.

THE MOSASAUR GENUS PLATECARPUS
Platecarpus was a mosasaur that averaged about 14 feet (4.3 m) long (the biggest ones are 24 feet (8 m) long). Platecarpus swam by moving the long tail and used the short flippers to steer. They had sharp teeth and ate fish and squid. Fossils have been found in Europe.

THE MOSASAUR GENUS PLOTOSAURUS
(pronounced PLOAT-oh-SAWR-us) Plotosaurus was a mosasaurthat was about 33 feet (10 m) long. They had four flippers and a tail that ended in a fin. These carnivores had sharp teeth and ate fish, squid, and perhaps shellfish. Fossils have been found in North America.

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