Elasmosaurus, being a long necked plesiosaur, was a carnivorous creature living in a near shore environment in the Western Interior Seaway of what is now North America. At the time the Western Interior Seaway cut what is now North America in half, creating two continents (Appalachia in the east and Laramidia in the west) and the shallow ocean was the home of a multitude of species. This large number of species, especially of smaller (and hence lower on the food chain) fish and invertebrates, led to an explosion in larger predators as well, of which Elasmosaurus was one. How is it such a successful predator? We shall examine this over the next week, starting tomorrow morning.
Everhart, M. J. (2005). Oceans of Kansas - A Natural History of the Western Interior Sea. Indiana University Press, Bloomington, Indiana, 344 pp.