Megalodons, which went extinct 3.6 million years ago, are believed to have grown to lengths of 50 feet. Credit: Alex Boersma/PNAS
Phys.org has an article about Megalodon. Otodus megalodon, which means "big tooth", was a very large shark that lived from the Oligocene 28 million years ago up to the Pliocene, just 3.6 million years ago. O. megalodon is classified as a mackerel shark, which is not closely related to the great white shark, Carcharodon carcharias. New research published in the journal Proceedings of the National Academy of Sciences looked at fossil teeth and concluded that Megalodon was warm blooded. Maintaining a higher energy level would have given it a body temperature, which may have given it an advantage in the competition over resources.
In the new study, the scientists looked for answers in the megalodon's most abundant fossil remains: its teeth. A main component of teeth is a mineral called apatite, which contains atoms of carbon and oxygen. Like all atoms, carbon and oxygen can come in "light" or "heavy" forms known as isotopes, and the amount of light or heavy isotopes that make up apatite as it forms can depend on a range of environmental factors. So the isotopic composition of fossil teeth can reveal insights about where an animal lived and the types of foods it ate, and—for marine vertebrates—information like the chemistry of the seawater where the animal lived and the animal's body temperature.
"You can think of the isotopes preserved in the minerals that make up teeth as a kind of thermometer, but one whose reading can be preserved for millions of years," said Randy Flores, a UCLA doctoral student and fellow of the Center for Diverse Leadership in Science, who worked on the study. "Because teeth form in the tissue of an animal when it's alive, we can measure the isotopic composition of fossil teeth in order to estimate the temperature at which they formed and that tells us the approximate body temperature of the animal in life."
