Megalodons, known scientifically as Otodus megalodon, were massive sharks that grew up to 15 meters long and roamed the oceans 15 million to 3.6 million years ago, said study author Kenshu Shimada, a professor of paleobiology at DePaul University in Chicago.
The 6.6-foot measurement is reasonably accurate and is consistent with other findings at megalodon farms in Panama and Spain, said Jack Cooper, a fossil shark researcher and PhD student in the department of life sciences at Swansea University in Wales, UK, who was not involved in the study.
The study is important because there isn’t much research on megalodon reproduction, he said.
To determine the animal’s height at birth, researchers looked at CT scans of the vertebrae of a megalodon originally found in Belgium in the 1860s. Like the rings of a tree, a megalodon’s vertebrae have annual growth bands that allow scientists to track the shark’s age.
The specimen was believed to be 46 years old when it died, so Shimada counted the growth bands back to birth and calculated the animal’s height at birth. This particular shark was estimated to be about 30 feet long at death.
Survival of the fittest
These extinct sea creatures did not grow that big in the womb by chance.
While growing inside its mother, megalodons ate other unhatched eggs, known as intrauterine cannibalism.
“As a result of the egg-eating behavior, only a few puppies will survive and develop, but they can all grow significantly large at birth,” Shimada said.
Their large size at birth reduces the chances of the baby megalodons being eaten by other predators.
Some modern sharks that are part of the Lamniformes order – the same to which the megalodons belong – also practice this behavior.
Sand tiger sharks eat other hatched eggs in the womb, and Shimada said they sometimes eat other hatched siblings as well.
It takes a lot of energy for female sand tiger sharks to rear such large babies, he says, but similar to the megalodon, this evolutionary strategy reduces the chances of them being eaten after birth.
Look forward to something
Much remains unknown about the giant shark, Shimada said, looking to discover more. He has had an interest in the megalodon since he was 13 years old when he found a 2-inch megalodon tooth at a geological site outside Tokyo.
While this study has revealed a lot about the birth of a megalodon, the specimen was only 46 years old, which is the middle age for this animal.
Shimada hopes to explore the shark’s later years, estimated to be between 88 and 100 years old, to learn its growth pattern.