Sunday, November 24, 2013

Tylosaurus: Prehistoric Animal of the Week

This week we shall be checking out a true prehistoric sea monster, Tylosaurus!  This is in honor of Nathan Van Vrankan's birthday, who is one of our writers and also works with Tylosaurus

Tylosaurus lived during the Late Cretaceaous about 80 million years ago in a warm, shallow sea that once existed down the middle of North America called the Western Interior Seaway.  There are a few known species belonging to the genus, Tylosaurus.  The biggest, called Tylosaurus proriger, would have been almost fifty feet long as an adult!

Tylosaurus proriger makes a meal out of the prehistoric shark, Cretoxyrhina mantelli A.K.A. the "Ginsu Shark".  That shark would have been about twenty feet long.

Tylosaurus belongs to a family of reptiles called mosasauridae, which are actually a kind of marine 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, and likely 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, would become top predators! 

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 preyed on virtually every other animal it shared its habitat with, including plesiosaurs, ammonites, sharks, bony fish, birds and even smaller Tylosaurus.  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, including two extra rows on the roof of the mouth.  These teeth were backed up by tremendous jaws that no doubt could crush or at least hold on tightly to whatever they got hold of.  Tylosaurus wouldn't have relied on its flippers to propel it through the water.  Instead, Tylosaurus had a long, powerful tail, tipped with a fluke to do this.  Its flippers, which were modified walking limbs from its ancestors, were probably more useful for turning.

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.  We also think, thanks to another nicely preserved mosasaur fossil, that Tylosaurus would have had a shallow fluke on the top of its tail.

That's all for this week!  In the weeks to come we will be checking out some newly discovered dinosaurs and one old dinosaur with a new look!   As always comment below or on our facebook page

References

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.

No comments:

Post a Comment