Ancient baby sharks were raised in nurseries 16 million years ago, fossil teeth reveal

Ancient giant predatory sharks used nurseries to raise their young millions of years ago, according to a new study that investigated fossilized megalodon teeth.

Five potential nurseries, dated 3.6 to 16 million years ago, have been identified by researchers at the University of Bristol using fossil teeth of different lengths.

Slow to reproduce, megalodon nurseries likely contributed to the success – and subsequent demise – of this iconic predator, the authors found.

They examined nine areas where megalodon remains were found, and say five may have been nurseries, because most of the remains found were of newborn or young animals.

Breeding these ancient shark babies in this way may have improved survival, but it may also have contributed to the demise of the monstrous sharks, they say, as the lack of suitable breeding sites could have contributed to their extinction.

Nursery areas are critical to the success of many marine species and play a key role in maintaining viable adult populations, the researchers explained.

As part of the study, the international team – from the United States and the United Kingdom – examined the size class structure of the extinct giant shark across these potential nursery sites.

Otodus megalodon is the largest shark ever lived, with body length estimates of up to 50-60 feet for the largest adult individuals.

This species inhabited the warm and temperate waters of all major ocean basins, covering an interval of nearly 20 million years, from the lower Miocene to the Pliocene.

Most studies evaluating the causes of global distribution, the evolution of gigantism and the extinction of these huge sharks have focused on the impact of climatic factors and / or on the abundance and migration patterns of potential prey. .

They also looked at competition with other large predatory species, the availability of suitable habitats and the presence of regional body temperature.

However, far less attention has been paid to important aspects of their reproductive biology, including how they raise their young.

Shark nurseries are often found in geographically distinct regions with high productivity, defined by the high abundance of hatchlings.

These nursery areas have been identified in a number of living shark species, and scientists speculated that the megalodon used them, but there was no evidence.

As part of this new study, the team surveyed nine sites around the world and found megalodon teeth representing sharks of different sizes, including juveniles.

They found that this size distribution was similar to that seen by modern sharks.

‘The use of nursery areas is likely to play a key role in the evolutionary history of some shark species,’ the researchers explained.

This is especially true when it comes to megalodon, which is thought to have been a slow-growing species with a high age of maturity.

They benefited from a strategy to maximize the survival of their young through nurseries is evidence in the growth rings found in fossils.

‘It therefore seems plausible that the use of nursery areas could have been essential for O. megalodon in order to reduce neonatal and juvenile mortality,’ the team said.

This would allow them to “provide maximum recruitment, thus maintaining viable populations on a long-term time scale.”

The results were published in the journal Biology Letters.