the Prehistoric Ocean: Illustrations of Dinosaurs

[Melody Stacker]

Here a Mosasaurus cruises the rocky underwater shoreline of the Late Cretaceous Japanese Islands, looking for a meal.  The ammonites in the background appear to be wishing they were some place else! During the Late Cretaceous, the ocean off the coast of what would become Japan was host to many different species of ammonites...  and many of the same genera of marine reptiles (mosasaurs and plesiosaurs) as were found in the Western Interior Sea.

[Melody Stacker]

A pod of very early and quite small (1-2 m) ichthyosaurs (Utatsusaurus hataii) searches for prey in the waters near present day Japan.  Some of the earliest remains of ichthyosaurs have been found in Japan and China.

[Melody Stacker]

Here a Mosasaurus hoffmanni just misses the mark in an attack on the marine crocodile, Thoracosaurus, in the seas over present day New Jersey. Wanna bet on the outcome? These Maastrichtian age animals are known from both North America and the Netherlands in Europe (the North Atlantic was much smaller 68 million years ago).  Thoracosaurus survived for some time after the K/T boundary event while mosasaurs, plesiosaurs, dinosaurs and many other groups did not. Although first found in the Netherlands, M. hoffmanni is also known from the Western Interior Sea (Texas).

[Melody Stacker]

This rather dramatic picture was done especially for my poster presentation at the 1999 Society of Vertebrate Paleontology meeting in Denver.  It shows a large Cretoxyrhina mantelli shark taking a bite out of a juvenile Tylosaurus.  While we are unsure if these sharks attacked live mosasaurs, or scavenged their carcasses, feeding by sharks on mosasaurs is supported by a lot of fossil evidence. See the Ginsu Shark, Parts and Pieces, and A Moment in Time. 

[Melody Stacker]

"Feathers and all" - It's hard to imagine the scale of this picture.... the little swimming birds (Hesperornis) are about 5 feet long and the Tylosaurus ... well, it's huge.  Modeled after the largest specimen on exhibit (The Bunker Tylosaur), this beast was at least 45 feet long and had a skull that was 6 feet in length.  Read about "A day in the life of a mosasaur" here.

[Melody Stacker]

In this view, a Clidastes (one of the smaller mosasaurs, about 12 feet long) is about to put the bite on a turtle called Calcarichelys somewhere off the ancient gulf coast of what is now Alabama.   Mosasaurs fed on just about anything that was small enough for them to swallow.

[Melody Stacker]

This picture shows an attack by a very large (30'+) mosasaur called Tylosaurus proriger on a much smaller Platecarpus mosasaur. Tylosaurus occasionally killed and ate other species of mosasaurs but there is no evidence to show that any of the mosasaurs were cannibalistic toward their own species.

[Melody Stacker]

This scene is based on a specimen found South Dakota and shows a mother Plioplatecarpus giving birth to the second of her two babies. Until recently, it was assumed that mosasaurs laid eggs on beaches like turtles. Instead, they appear to have given birth at sea just like the ichthyosaurs. 

[Melody Stacker]

This encounter is also based on a recently found specimen of a young adult Mosasaurus conodon that showed evidence (embedded tooth and a broken neck) of being attacked and killed by a larger member of the same species.     

[Melody Stacker]

This picture shows a Plioplatecarpus feeding on a school of fish and is based on a specimen found in Central Alabama by a Historical Geology class from Okaloosa Walton Community College in Northwest Florida.  Plioplatecarpus mosasaurs were more advanced and somewhat specialized.  See the latest Plioplatecarpus page - A Plioplatecarpus from North Dakota

[Melody Stacker]

Globidens was another very specialized mosasaur, with round, crushing teeth.  This picture shows two Globidens dakotensis mosasaurs feeding on clams and other shellfish found on the bottom of the shallow, inland sea that covered South Dakota and much of the middle of North America.

[Melody Stacker]

This picture shows what happens when the hunter becomes the hunted, as a giant pliosaur called Brachauchenius lucasi attacks an early Clidastes mosasaur.  Although pliosaurs became extinct during Turonian time, they were still present in the Western Interior Sea when the first mosasaurs arrived. Even though mosasaurs were top predators, their young were often preyed upon by sharks, large fish, and even other species of mosasaurs.  Life could be short for the unwary.

[Melody Stacker]

"Brachauchenius and Squid" from a painting done for Pete Von Sholly. This picture recreates an actual specimen found in the Turner Sandy Member of the Carlile Shale Formation (Turonian / Late Cretaceous) near Edgemont, South Dakota. This was the latest age that these giant pliosaurs were found in North America.... coincidentally the same time that mosasaurs first appeared.

[Melody Stacker]

The Cretaceous Seas were a dangerous place for lots of good reasons. This view shows two giant (up to 17 feet or more in length) Xiphactinus audax on the prowl for their next meal.  These fish fed by swallowing their prey whole, and are sometimes found with their last meal perfectly preserved inside.

[Melody Stacker]

This picture shows a large (up to 5 feet tall),  flightless seabird called Hesperornis regalis swimming underwater to catch a small fish.   These birds still had teeth in their jaws, but probably behaved much like modern penguins.  Their fossils are much more common in Late Cretaceous marine deposits north of Kansas.