The creatures that controlled the oceans more than 3 million years ago were about 2 meters long at birth, according to a new study in the journal Historical Biology. They were larger than most adult humans.
Researchers made this disturbing discovery when they took X-rays of the vertebra of a fossilized megalodon (Otodus megalodon ) and found that it must have been about six feet long when it was born. The remains of megalodons, which lived in most of the world’s oceans from 15 to 3.6 million years ago, have revealed that adults grew to more than 15 meters in length, but until now it was not clear what would have been their size at birth.
The scientists looked at “growth rings” in chunks of the shark’s preserved skeleton, similar to how rings work in tree trunks that are used to determine the age of a tree. Because, even though teeth make up most of the megalodon fossil record we have, some vertebrae have also been recovered . And it was from several of these vertebrae, housed in the Royal Belgian Institute of Natural Sciences in Belgium, that a new enigma of these mysterious animals has been revealed.
Regarding the studied fossil, a 15 cm wide piece whose cartilage had mineralized, it was estimated that it came from a 9 meter long megalodon, according to comparisons with similar vertebrae observed in great white sharks, a distant descendant.
“The new study is really the first of its kind that has given us a good idea of the megalodon’s size at birth, reproductive mode and growth pattern,” said Kenshu Shimada, professor of paleobiology who led the research at DePaul University in Chicago. (USA).
Impressive hatchlings
The largest predatory shark hatchlings to ever exist are also not far behind. But nurturing such huge calves would have cost the mother a great energy cost. How to solve it? Everything seems to suggest that the offspring supplemented nutrients in utero with an additional help from cannibalism from unborn siblings. Thus, according to experts, it is possible that during their embryonic growth, the largest newborns had eaten other eggs while they were still in the mother’s womb, to achieve that impressive size. It is not something strange, because today it is still a survival strategy shared by some current species of shark.
This, of course, results in fewer live young, but sharks that survive are believed to have a greater survival advantage, as they are born bigger and stronger and have a better chance of taking on predators.
“Oophagia (eating eggs) is a way for a mother to nourish her embryos for a prolonged period of time,” the expert clarifies.
“As one of the largest carnivores to ever exist on Earth, deciphering such growth parameters for O. megalodon is critical to understanding the role large carnivores play in the context of the evolution of marine ecosystems ,” says Shimada. .
Referencia: Historical Biology, DOI: 10.1080/08912963.2020.1861608
