For around 20 million years, gigantic sharks called megalodons roamed the oceans across the globe, eating whales, porpoises, and even other sharks. But while megalodons are known for being the prehistoric ocean's apex predator as adults, they first had to survive their vulnerable juvenile stage. A recent study suggests that young megalodons spent their early years in relatively safe and secluded coastal regions known as shark nurseries. According to the study authors, these nurseries may have played a key role in shark evolution.

Paleontologists compared the size of megalodon teeth from eight sites known as well as one newly discovered fossil-rich site in Spain. Of these locations, five were determined to be likely megalodon nurseries due to the prevalence of newborn and juvenile-sized teeth in comparison to the number of adult teeth. These five nurseries varied dramatically in age, with some dating back nearly 16 million years, while others were only three to four million years old. The researchers concluded that the megalodons’ reliance on nurseries must have been a stable characteristic throughout their long existence on earth.

As with many modern-day sharks, megalodons likely benefitted from nurseries due to their extremely slow rate of development. Some paleontologists estimate that they may have taken over 25 years for megalodons to reach their final adult size. If juveniles lacked a safe place to live, they could easily have been eaten by the same animals that their larger relatives considered prey.

The discovery of these megalodon nurseries suggests that this strategy for juvenile protection may have been one reason why this species survived for so many millions of years. On the flip side, the widespread loss of coastal habitats due to climatic changes likely caused a spike in mortality of juvenile megalodons and may have been a critical factor driving the extinction of this iconic species.