Monday, September 28, 2020

Tylosaurus: Beast of the Week

Today we'll be checking out an iconic sea monster.  Watch out for Tylosaurus proriger!

 was a gigantic meat-eating marine reptile that lived during the late Cretaceaous period, 80 million years ago in what is now the middle of North America, which during its time was a shallow sea.  There are a few known species belonging to the genus, Tylosaurus.  The biggest, called Tylosaurus proriger, would have been almost fifty feet long from snout to tail.  The genus name translates to "Knob Snout" because of the protruding bony tip of this animal's jaws. When alive Tylosaurus would have eaten meat, preying on pretty much any animal it could catch in its environment.

Tylosaurus proriger attacks the prehistoric turtle, Archelon.

Tylosaurus belongs to the family of reptiles called mosasauridae, which were actually a kind lizard, closely related to extant monitor lizards.  Mosasaurs are known in the fossil record only in the Cretaceous period, at the end of the Mesozoic era, and evolved from terrestrial lizard ancestors.  Despite their late appearance in the oceans, they quickly became extremely successful and some, like in the case of Tylosaurus, became top predators in their communities. For whatever reason mosasaurs went extinct at the same time as all of the non-avian dinosaurs about 66 million years ago.  

Tylosaurus skeleton on display at the National Museum in Washington D.C.

Tylosaurus was indeed one heck of a predator.  Many fossils have been uncovered that show evidence of it having eaten virtually every other animal it shared its habitat with, including plesiosaurs, ammonites, sharks, bony fish, birds and even smaller mosasaurs.  These fossils include bones with Tylosaurus teeth marks in them to actual remains of other animals found inside the stomach cavity of Tylosaurus skeletons.  To be such a predator, Tylosaurus had more than just size on its side.  Inside this animal's mouth were many sharp, cone-shaped teeth.  These teeth were backed up by tremendous jaws that no doubt could crush or at least hold on tightly to whatever they got around.  It also had two extra rows of teeth inside the roof of its mouth.  these teeth were likely to help manipulate food down its throat after being seized by the main set of jaws.  

Tylosaurus skeletal mount on display at the Academy of Natural Sciences in Philadelphia, Pennsylvania.

Like one of our modern kinds of marine reptiles, sea turtles, Tylosaurus had four paddle-shaped flippers instead of digits and claws.  Tylosaurus wouldn't have relied on its flippers to propel it through the water, however.  Instead, Tylosaurus had a long, powerful tail, which had immense muscles at its base and likely tipped with a fluke like a shark, to power through he water.  Its flippers, which were modified walking limbs from its land-dwelling ancestors, were probably more useful for turning and maneuvering in short quarters.  This combination of traits would have made Tylosaurus a relatively fast-moving animal in the water, which also gave it an edge when hunting large prey like plesiosaurs and turtles.  

Tylosaurus skin impression.  Check out those keeled scales!  Very snake-like.

We know, thanks to a wonderfully preserved specimen, that Tylosaurus would have had diamond-shaped scales on its body, similar to some modern snakes and lizards.  These scales were even keeled which probably would have helped the animal swim faster by cutting the water around it as it moved.

That's all for this week!  As always feel free to comment below!


Cope ED. 1869. [Remarks on Macrosaurus proriger.] Proceedings of the Academy of Natural Sciences of Philadelphia 11(81): 123.

Everhart MJ. 2005. Oceans of Kansas - A Natural History of the Western Interior Sea. Indiana University Press, 322 pp.

Snow, F. H. (1878). "On the dermal covering of a mosasauroid reptile". Transactions of the Kansas Academy of Science 6: 54–58.

Lindgren, J.; Caldwell, M.W.; Konishi, T.; and Chiappe, L.M. (2010). "Convergent Evolution in Aquatic Tetrapods: Insights from an Exceptional Fossil Mosasaur". In Farke, Andrew Allen. PLoS ONE 5 (8): e11998. doi:10.1371/journal.pone.0011998. PMC 2918493. PMID 20711249.

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