When people think of “big sharks,” they usually think of the legendary shark, Megalodon (Otodus megalodon), which reached at least 50 feet (15 meters) in length when it was ruling our oceans million years ago. So, it should come to no surprise that they gave birth to pups that are larger than most adult humans… right?
Yes, you read that right. Their babies were larger than humans. Gulp!
Almost everyone knows Megalodon… but there still exist large gaps in our knowledge of them. And thanks to this latest study in the international journal Historical Biology, scientists have shed vital light on the reproductive biology, growth, and life expectancy of these extinct predators. “As one of the largest carnivores that ever existed on Earth, deciphering such growth parameters of O. megalodon is critical to understand the role large carnivores play in the context of the evolution of marine ecosystems,” said Kenshu Shimada, a paleobiologist at DePaul University in Chicago and lead author of the study.
Like most ancient sharks, experts go by fossil records to understand not only the animal itself but what life was like for them. Thankfully, it is not just teeth that we have leftover from Megalodon! It has a rich fossil record, and there even exists a vertebral specimen in the Royal Belgian Institute of Natural Sciences in Brussels. This gave the team an opportunity to examine incremental ‘growth bands’ (like tree rings) using CT scanning techniques. The vertebrae – thought to have been from an individual that was about 30 ft (9 m) long – measured about 6 in (15 cm) in diameter and had 46 annual growth bands meaning it died when it was 46 years old. A young shark, since a growth curve model appears to indicate its life expectance of at least 88-100 years, commented Shimada.
By back-calculating the individual’s body length when each band formed, the study suggests that the shark’s size at birth was about 6.6 ft (2 m) in length. Sounds big, right? Well, turns out that this data implies that Megalodon gave live birth to possibly the largest babies in the shark world! “Results from this work shed new light on the life history of Megalodon, not only how Megalodon grew, but also how its embryos developed, how it gave birth, and how long it could have lived,” said co-author Martin Becker from William Paterson University.
Huge babies for a huge shark? Checks out. “My students and I examine spiny dogfish shark anatomy in class and to think that a baby Megalodon was nearly twice as long as the largest adult sharks we examine is mind-boggling,” explained co-author Matthew Bonnan from Stockton University. But it turns out these pups didn’t get nourishment from momma shark alone, but their siblings! Like the Lamniform sharks we have today, the data suggests that embryonic Megalodon also partook in form of intrauterine cannibalism practice known as “oophagy”. Oophagy, literally “egg eating”, happens when developing sharks would feast on their ‘potential siblings’ while still in the mother’s uterus.
Sounds harsh to eat your siblings for a meal. But it is a ‘shark eat shark’ world and gives the pups a fighting chance against larger predators. Giving birth to such large baby sharks was most likely energetically costly for the mother, but it is the least she can do since there is no parental care involved once the pup makes its grand entrance into the world.