Last week’s “What Is It Wednesday” photo is a pretty amazing specimen on display in the center island of the Museum of Geology main exhibit area.
The actual specimen belongs to the mosasaur Tylosaurus proriger, an enormous marine reptile that reached lengths of forty feet. Tylosaurus was likely one of the apex predators in the Western Interior Seaway, eating whatever it darn-well pleased.
Which brings us to the unique nature of this specimen. While it does contain vertebrae and pelvic elements of Tylosaurus, what is special about this specimen is that it contains stomach contents, ostensibly this mosasaur’s last meal.
Above is a color coded diagram of the stomach contents. The elements outlined in dark blue are those of the “host”, Tylosaurus proriger. Those outlined in orange are of the shark Odontaspis. Red elements are of the bony fish Bananogmius. Light blue elements are of the smaller mosasaur, Platecarpus, and green elements are from the large diving bird Hesperornis.
This fossil tells us a great deal about the paleobiology of mosasaurs, particularly Tylosaurus proriger. As stated above, Tylosaurus was a top tier predator and ate whatever came across its path, including smaller mosasaurs. This specimen represents an amazing snapshot of South Dakota during the late Cretaceous.