Overview
- A peer-reviewed study in BMC Zoology reports freshwater isotope signatures in a Hell Creek mosasaur tooth dated to about 66 million years ago.
- Oxygen and strontium ratios in the enamel match river water, and the tooth shows no evidence of having been transported after death.
- Carbon isotope values are unusually high for mosasaurs, indicating shallow-water foraging and raising the possibility of scavenging drowned dinosaurs.
- The tooth is assigned to a prognathodontine mosasaur and its size implies an individual roughly 11–12 meters long, comparable to the largest killer whales.
- Two slightly older mosasaur teeth from nearby sites show similar freshwater signals, supporting a model of a freshening Western Interior Seaway with a surface freshwater layer.