A giant shark, Otodus megalodon, ruled the oceans, without competition, 5 million years ago. However, it disappeared, being replaced by a “smaller” cousin, the great white shark, according to a European study.
In the food chain, O. megalodon at one time occupied the highest trophic level – the rank – that was the top predator. A conclusion drawn in particular from the size of its teeth, sharp triangles that easily exceed ten centimeters, or the width of a palm. It is one of the only remains that can be used to study the animal, whose cartilaginous skeleton, as in all sharks, does not lend itself to fossilization.
An international team of researchers is bringing in NatureCommunication a new light on this giant over 15 meters, which reigned in the oceans over 3 million years ago.
The sudden disappearance, of recorded fossilsof this carnivore, among the largest ever, remains a puzzleemphasizes the study signed by Jeremy McCormack, geoscientist at the German Max Planck Institute.
It offers a new tool for evaluating the trophic level ofO. megalodon and its competitors, from the zinc contained in the enamel of their teeth. This metal, which is vital, is found in food and fixed to teeth.
Resource competition
It is found there in the form of two isotopes – two types of atoms -, where the larger or smaller proportion of one of them, zinc 66, has a direct link to the animal’s place in the food chain. The lower its proportion, the higher the animal in the food chain.
Researchers have tested this recent technique in examining fossils from many museums and current species. Among the latter, the great white shark and the Mako shark are at their highest trophic level today.
But 20 million years ago, during the Miocene, that honor went Otodus chubutensisa giant shark fond of fish and cetaceans. Otodus megalodon it thrives as a peak predator, but at a lower tropical level, until the Pliocene period, about 5 million years ago.
Tests show that the megalodon then lost ground against Carcharias carcharodon, the great white shark. Although smaller in size – it doesn’t reach more than six meters – it is known to be very opportunistic in terms of food. The study of Nature note that the two species are at the same level in the food chain.
We don’t know why O. megalodon completely lost. A study in 2016 found a gap between the collapse of its population and a decrease in the diversity of cetaceans in which it fed, along with the loss in particular baleen whales. The authors of the study Nature support this hypothesis of a co-evolution and co-extinction of two types of sharks and whales.
They also see an important factor in competing with the great white shark. Their study suggests a possible competition for food resources between two lines of sharks. That great white shark ended up winning.
Source: Radio-Canada
