By: Staff

Updated on: 28/03/2022

The Tylosaurus was an enormously large reptilian hunter of the ancient seas that lived during the Turonian to Campanian ages of the Cretaceous period. They have been classified under the order Squamata that includes scaly reptiles including the modern-day snakes and monitor lizards. The Tylosaurus holds the record of being one of the most massive creatures of the world to have ever swum in the oceanic waters.

Scientific Classification


Quick Facts

Geological Period:Cretaceous period (89 to 80 million years ago)
Size:Around 59 feet (18 meters)
Height:Largest specimen was more than 50 feet (around 15 meters) in length
Weight:Largest specimen is estimated to have been about 25,000 kg
Bite Force:3 metric tons (4000 pounds)
Average Lifespan:Unknown
Location/Distribution:North America
Habitat:In the shallow waters, but probably not close to the coast, though it did not move very deep into the ocean
Climate/Environment:Preferred relatively warmer waters
Birth Type (Reproduction):Not sufficient evidence available whether they were oviparous or viviparous, but the latter is extremely likely
Locomotion:Swam using flippers (modification of the arms)

History and Discovery


In 1868, the fossilized holotype-remains of the creature were unearthed by O C Marsh, an American paleontologist, in the middle of a competition with E D Cope, another American paleontologist, as also a comparative anatomist, in Kansas’ Gove County.

Tylosaurus Skeleton

Later again, in 1872, he discovered yet another skeletal remains in the same region, which Marsh grouped with his previous discovery. In fact, there were more bones present in the fossil of the second finding, and it was also better preserved.

In 1911, the largest ever remains of the creature was excavated in Wallace, while in 1918, the Tylosaurus that was discovered had the contents of its stomach intact. The recent most fossil was unearthed in 2009 in Ohio’s Logan County.

Physical Description

Tylosaurus Fossil

These were giant size reptiles with the powerful upper jaw being modified to a long, elongated snout, one of the typical features of these creatures used to locate their prey. It had two rows of pointed, cone-shaped teeth lined on each side of their jaws.

Tylosaurus Skull

The large body of the Tylosaurus was streamlined, with the limbs being modified in the form of flippers. Unlike most other dino species, the hind limbs and the forelimbs were almost of similar measurements, which they used to paddle through the waters at high speed.

The tail of the Tylosaurus was very long and was probably quite thick. Though many illustrators have drawn a beaver-like tail behind its back, most of the scientists are unanimous that the tail was actually bi-lobed.


Picture of Tylosaurus

These animals were ferocious predators, with many of their skulls showing the evidence of fractures that seemed to have caused by the impact of striking on hard objects. Scientists have speculated that these fractures were caused because of the strength they would apply by using their strong jaws to crush their prey or enemies, or while attacking other larger marine animals.

Some paleontologists think that it is also quite likely that these marks were inflicted by other larger Tylosauruses, which again gives evidence to fierce intra-species competitions.


They were strictly carnivorous. Remains of sharks, other large fishes, plesiosaurs, and mosasaurs have been found in the fossils of the Tylosaurus.

Tylosaurus Dinosaur

Interesting Facts

  • In the late 1800s, there was a prevalent misconception that these reptiles had a hump on their dorsal surface, which has been discarded by the modern paleontologists.
  • The name of this ancient creature came from the term ‘tylos’, which in Greek means ‘projection’, and ‘saurus’, from the Greek term ‘sauros’, meaning lizard. Thus the entire name ‘Tylosaurus’ means a ‘lizard with a projection’.
  • The family Mosasauridae (Mosasaurs), to which these creatures belonged, were amongst the most successful and fittest predators of the later Cretaceous period.
  • A fossil unearthed in 1918, with its belly intact, had a plesiosaur in its stomach.

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