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About 23 million years ago, one of the most voracious predators that has ever travelled the oceans of the Earth appeared: the megalodon. This nightmarish shark, the largest of all time, was almost 20 meters long, three times the size of white sharks, and weighed 50 tons. No wonder he continues to fascinate both scientists and the film industry, which even made him last summer the protagonist of a box office success of those to consume with popcorn.
Although most researchers believe that the monster ended extinct – 2.5 million years ago, according to a team from the University of California Merced (USA) -, its authentic destiny has been questioned in some occasions, to the point that there are those who have claimed to have sighted it today or have been attributed to remains found on the coasts or the death of other sharks. The myth was in its day fed by some television programs that suggested that the giant could continue to cross the waters.
Now, researchers from the also American University William Paterson believe they have discovered the reason why it is impossible for the megalodon to remain hidden in the depths of the oceans. As explained at the annual meeting of the American Union of Geophysics (AGU), it was the high body temperature of this huge fish that finally ended with him.
Like the current sharks, such as white or mako, the megalodon could adjust the temperature of its body as it was in cold or hot water. This would have allowed him to survive successfully in different habitats, an advantage when hunting, as explained by the authors of the study in the magazine LiveScience. But while the ancestors of the current sharks that lived with the megalodon had body temperatures between 20 º C and 30 º C, the brutal beast could have oscillated between 35 º C and 40 º C, similar to that of mammals such as whales.
Such heat would have required a very active metabolism and, therefore, feed frequently. But then the weather warmed up and the megalodon dams (which ranged from big fish and turtles to whales, dolphins, seals or other marine mammals) moved to cooler waters at higher latitudes. The shortage of food and competition with new species of predators, such as killer whales, may have been the fatal combination that led the giant to extinction after having reigned for 21 million years
Read in your teeth
What makes the existence and extinction of megalodons a mystery to researchers is that the anatomy of these ancient sharks was very similar to that of modern sharks, with skeletons made of cartilage instead of bone. This characteristic, also common to the rays, distinguishes them from other vertebrates. But it means that sharks do not leave large fossilized remains like other animals do. The bone is mineralized and fossilized, something that the cartilage does not do or does wrong.
But like modern sharks, the extinct teeth were made of calcium phosphate, which makes them very abundant in the fossil record. This is precisely what researchers have used for their study. To find out if the body temperature of the megalodon was similar to that of modern sharks, the scientists examined the isotopes of carbon and oxygen in the teeth of the ancient shark and those of modern sharks. These isotopes form different bonds depending on the temperature of the animal when teeth develop.
With this technique, the team was able to estimate the average body temperature of the megalodon and find clues as to what led to the extinction. “Large climatic changes combined with evolutionary limitations may provide the key to the extinction of the largest shark species that has ever roamed the planet,” they conclude. The monster may no longer sail the oceans but its magnetic legend and scientific interest are still alive .
Source: ABC ES