Geokolloqium, Dr. Jeremy McCormack

- GEOWISSENSCHAFTLICHES KOLLOQUIUM -

Who ate whom? Unravelling the ecology of giant sharks and other extinct predators using the novel zinc isotope proxy

Presentation from Dr. Jeremy McCormack
Goethe-Universität Frankfurt

Reconstructing the diet and trophic ecology of long extinct animals remains one of the greatest challenges in palaeontology. Diet is a key driver of evolution and often a predictor of a species’ extinction risk. Rare cases of preserved stomach content, coprolites (fossilised faeces) and bite marks offer snapshots of fossil trophic interactions but are not necessarily a true reflection of a species regular diet. Stable isotope analyses of collagen nitrogen on the other hand, is a well-established method to identify a vertebrate’s trophic position but is usually not applicable to fossils older than 100,000 years due to poor protein preservation. Zinc is incorporated into the mineral phase of bones and teeth and as such has a much better long-term preservation potential, especially in the hypermineralised outer layer of teeth, the enamel(oid). Only in recent years zinc isotope ratios in bioapatite were discovered to be a particularly promising diet and trophic level proxy. In this talk, I will demonstrate how we can use this novel proxy to identify an extinct animal’s trophic ecology and its position within ancient food webs. I will discuss the ecology of one of the largest predators that ever existed on earth, the giant shark Otodus megalodon, and how the use of zinc isotopes and other geochemical proxies may help us understand how and why a predator could reach these sizes and why this gigantic shark went extinct.