In the 1940's Harold Urey set out to determine why the dinosaurs went extinct at the K/T boundary; he began isotopically analysing
invertebrates with the intention of creating a paleotemperature scale (Barrick, 1998). He believed that there may have been a climatic shift at the K/T boundary that caused the extinction of the dinosaurs (Barrick,
1998). Since then the field of isotope paleontology has expanded greatly, and in the past decade it has virtually exploded (Corfield and Norris, 1998).