MOSASAUR STOMACH CONTENTS: DIET COMPOSITION OF DIFFERENT MOSASAURS

Mosasaurs, extinct marine reptiles, were prominent predators of the Western Interior Seaway, the large epicontinental sea that covered most of North America during the Cretaceous. Examination of fossil mosasaur stomach contents has allowed reconstruction of general paleo-diet for mosasaurs. Previous studies have cataloged the stomach contents of individual mosasaurs; however, analyses have not been done to see if diet varies among mosasaur genera or if different genera occupy different ecological niches. This study has compiled stomach-content data from eleven mosasaurs from seven genera. Four specimens were Tylosaurus spp., which were among the largest mosasaurs in the Western Interior Seaway. Here, I test the hypotheses that tylosaurs had significantly different diets than other mosasaurs, and that tylosaurs had more gut content specimens per individual than other mosasaurs. Tylosaur specimens had significantly more remains of marine reptiles and sharks in their stomach contents relative to other mosasaur genera. Tylosaurs were also preserved with significantly fewer fish, turtles, and invertebrates; the latter two were not present in tylosaurs, but were common components of the stomach contents of other genera. The number of organisms preserved in the stomach contents per individual, however, is not significantly different between tylosaurs and other mosasaur genera. The differences in dietary composition could be due to differences in feeding behavior or in the body size of the individuals studied.