Great White Sharks May Have Played Role in Megalodon Extinction

by johnsmith

Researchers from the Max Planck Institute for Evolutionary Anthropology and elsewhere have looked at zinc isotopes found in the teeth of extanct wild and aquarium sharks and compared them to the teeth of extinct megatooth sharks.

Otodus megalodon. Image credit: Karen Carr / CC BY 3.0.

Otodus megalodon. Image credit: Karen Carr / CC BY 3.0.

The trophic level of animals indicates their position within an ecosystem, and diet plays an important role in understanding an animal’s lifestyle and ecology.

Zinc is essential for living organisms and plays a crucial role in various biological processes. It is incorporated into the enamel of teeth when they are formed and can be used as a proxy for understanding an animal’s diet and for inferring its trophic level in the ecosystem.

“Zinc stable isotope analysis of tooth enameloid, the highly mineralized part of teeth, is comparable to much more established nitrogen isotope analysis of tooth collagen, the organic tissue in tooth dentine, which is used to assess the degree of animal matter consumption,” said lead author Dr. Jeremy McCormack, a researcher at the Max Planck Institute for Evolutionary Anthropology and the Goethe-University Frankfur.

“However, on the timescales we investigate, collagen is not preserved, and traditional nitrogen isotope analysis is therefore not possible.”

“We demonstrate, for the first time, that diet-related zinc isotope signatures are preserved in the highly mineralized enameloid crown of fossil shark teeth,” added senior author Professor Thomas Tütken, a researcher in the Institute of Geosciences at the Johannes Gutenberg University.

Dr. McCormack, Professor Tütken and their colleagues developed a new method for inferring diet in fossil organisms by using zinc isotopes.

They generated a database of zinc isotope values from shark teeth across 20 living species including the great white shark (Carcharodon carcharias), as well as several extinct species, including Otodus megalodon and its ancestor, Otodus chubutensis.

They found that zinc isotope values were preserved in teeth across geological time periods and also indicate the trophic levels of the species.

“We noticed a coherence of zinc isotope signals in fossil and modern analogue taxa, which boosts our confidence in the method and suggests that there may be minimal differences in zinc isotope values at the base of marine food webs, a confounding factor for nitrogen isotope studies,” said Professor Sora Kim, a researcher at the University of California Merced.

The authors compared zinc isotope values between Otodus megalodon and the great white shark and found that when they coexisted, during the Early Pliocene, their trophic levels overlapped and they may have competed for the same food resources, such as marine mammals including cetaceans.

“Our results show, that both Otodus megalodon and its ancestor were indeed apex predators, feeding high up their respective food chains,” said Professor Michael Griffiths, a researcher at the William Paterson University.

“But what was truly remarkable is that zinc isotope values from Early Pliocene shark teeth from North Carolina, suggest largely overlapping trophic levels of early great white sharks with the much larger Otodus megalodon.”

“These results likely imply at least some overlap in prey hunted by both shark species,” said Professor Kenshu Shimada, a researcher at DePaul University, Chicago.

“While additional research is needed, our results appear to support the possibility for dietary competition of Otodus megalodon with Early Pliocene great white sharks.”

The findings appear in the journal Nature Communications.

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J. McCormack et al. 2022. Trophic position of Otodus megalodon and great white sharks through time revealed by zinc isotopes. Nat Commun 13, 2980; doi: 10.1038/s41467-022-30528-9

Source link: https://www.sci.news/paleontology/megalodon-extinction-10865.html

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