First evidence of stomach contents in Mosasaurus missouriensis

New paper published on the marine reptile Mosasaurus missouriensis preserved with first evidence of stomach contents

July 11, 2014

The July 2014 issue of the Journal of Vertebrate Paleontology publishes the culmination of several years of research by Dr. Takuya Konishi, Postdoctoral Fellow at the Royal Tyrrell Museum of Palaeontology.


Dr. Takuya Konishi, Postdoctoral Fellow at the Royal Tyrrell Museum of Palaeontology with Mosasaurus missouriensis on display.

The paper discusses a Mosasaurus missouriensis specimen found in 2008 by Korite International during its ammolite mining operation south of Lethbridge, Alberta. The exquisitely preserved specimen provides the first evidence of what this type of mosasaur looked like, what it ate, how it co-existed with other predatory mosasaurs, and how it behaved.

Mosasaurus missouriensis

Mosasaurus missouriensis

Mosasaurs were highly successful apex predators in the Cretaceous Period aquatic ecosystems—more than 60 kinds of mosasaurs are known to have lived 95 – 65 million years ago. They were the only lizards to have evolved a fish-like anatomy with two pairs of well-developed flippers for steering and a shark-like tail for swimming through the waters.

The specimen, now on display at the Royal Tyrrell Museum, preserves the remains of its last meal—a one-metre-long fish. The fish braincase shows a puncture wound, the same size and shape of the mosasaur’s tooth, indicating this animal used its sharp teeth to dismember fish larger than its head, rather than swallowing its prey whole. The preserved gut contents also indicate that Mosasaurus, with its narrow head and slender jaws, preferred soft prey. They contrasted in food habits with the other aquatic predator of the time, Prognathodon: with its wide head and deep jaws, the latter mosasaur consumed hard, as well as soft prey, allowing the two predators to coexist in the same ecosystem.


Mosasaurus missouriensis stomach contents

Remarkably, due to rapid burial after death, this specimen preserves the rare fossilization of soft tissue—an intact trachea (windpipe) and a good portion of the sternum (chest plate). This is the first time that soft tissue has been found in this type of mosasaur.

Chest plate (sternum) and windpipe

Chest plate (sternum) and windpipe

You can see the specimen in the Alberta Unearthed gallery at the Royal Tyrrell Museum.

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3 thoughts on “First evidence of stomach contents in Mosasaurus missouriensis

    • Hi Mike!
      Thank you for your question. Here is the response given by Dr. Konishi:
      The fish found inside the mosasaur body cavity is referred to a lizardfish, which are typically bottom sea dwellers today, but given the presumed pelagic (i.e., swimming near the surface of the water) nature of Mosasaurus missouriensis, this Late Cretaceous lizardfish consumed by the mosasaur was likely also pelagic.

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