The new approach provides an alternative technique for gathering information about the habitats of ammonites—an extinct type of shelled mollusk that’s closely related to modern-day nautiluses and squids. The study was recently publishedin PLOS ONE.
The two sites have fossils from the same era—the Upper Cretaceous—but the quality of ammonite preservation is quite different. In the Pierre Shale, ammonite jaws are found inside the body chambers of well-preserved ammonites, while in the Mooreville Chalk, the jaws are fossilized but the ammonite shells are gone. However, the use of ammonite jaws to derive ancient temperatures permits a comparison of these two sites.