The megalodon, a fallen star of the prehistoric ocean
With its 20 meters long estimated and its teeth over 15 centimeters, Otodus megalodon remained for a long time the archetype of the sailor superpredator. A beast that we readily imagined tracking the primitive whales in the warm waters of Miocene, reigning without sharing on the seas for almost 20 million years, before disappearing mysteriously about 3.6 million years ago.
Zinc in teeth: a precious indicator
Unlike bones, cartilage – which is mainly constituted by the skeleton of sharks – is preserved very badly. Fortunately, their teeth are often very well preserved in sediments, becoming real time capsules. In this study, scientists were interested in a particular element present in dental enamel: zinc.
More specifically, they measured the proportions of an isotope of zinc, the ZN-66, whose presence varies according to the position that an animal occupies in the food chain. The more carnivorous eats other carnivores, the more the heavy isotope content decreases. This isotopic relationship therefore becomes a direct tracer of the trophic level of the animal.
The researchers have thus analyzed the fossil teeth of the megalodon and several other missing sharks, of which Otodus chubatensisa close cousin. By comparing their results to those of current sharks, they were able to rebuild the diet of these giants with unprecedented finesse.
The megalodon: a predator, yes … but also a opportunist
The results are final: the megalodon occupied the summits of the food chain, as expected. But he was not a specialized killer only in whale hunting, as certain hypotheses suggested. In reality, his diet seems to have been much more varied.
According to isotopic data, it certainly fed on marine mammals, but also large fish, medium -sized sharks, and probably other less spectacular prey. This diversity in its diet makes it a general predator, capable of adapting its menu according to the availability of resources.
In other words, the megalodon was not a specialized brute, but rather an intelligent ocean giant, both formidable and pragmatic.
© Uwe Dettmar for Goethe UniversityJeremy McCormack with a fossilized megalodon tooth (Otodus megalodon).
A winning strategy … Up to a certain point
This ability to diversify its diet could explain why the megalodon prospered for so long. In perpetual change marine environments, this ecological flexibility was an undeniable asset. It allowed him to go through several periods of climate and biological upheavals.
But that didn't make him invincible. Around 3.6 million years, the megalodon died, and the exact reasons are still debated. Among the hypotheses: the drop in its usual prey, the cooling of the oceans, and above all, the arrival of a new actor on the marine scene – Carcharod Carchariasthe large modern white shark.
Smaller, more agile, and probably better suited to new ecosystems, the latter could have come into direct competition with the megalodon for certain prey, helping to precipitate its decline.
A major methodological advance
Beyond the fascinating case of megalodon, this study marks a turning point in marine paleontology. The use of zinc isotopes as a diet indicators opens a new path for the study of old ecosystems. So far, paleontologists had to be satisfied with indirect analyzes (teeth wear, fossil stomach content, etc.).
From now on, thanks to this fine geochemical approach, it becomes possible to map the missing trophic networks with a precision never reached. Which, ultimately, will not only better understand the past balances, but also to better anticipate the future of current superproductors in a context of global change.
End of myth, beginning of complexity
What this study reveals is that no predator-as gigantic and terrifying as it is-escapes the rules of an ecosystem. Even the megalodon, undisputed king of the oceans, was not an uncontrollable war machine, but an animal subject to ecological dynamics, competition, and at random of evolution.
Behind the Hollywood figure of the seas monster, it is a more nuanced portrait that emerges: that of an intelligent, adaptive, but vulnerable survivor. And which, like so many other species in the history of the earth, ended up disappearing, carried away by the flow of time.
Source : Earth and Planetary Science Letters
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