Megalodon, the largest shark that ever lived, was a fierce predator in prehistoric seas, with a bite force five times as strong as today’s great white. But it was also a wise mother, new research reveals. An analysis of megalodon teeth found from sites across multiple continents suggests these giants commonly used nurseries to improve their youngsters’ chances of survival, just as some modern sharks do.
It is an “exciting” possibility, says Kenshu Shimada, a paleobiologist at DePaul University who wasn’t involved with the work. Still, he says, more research is needed to confirm the findings.
Many modern marine animals, from shrimp to sharks, rely on nurseries. These shallower areas, such as mangroves and seagrass, are rich with nutrients, which help young grow big and strong enough to survive out on their own.
In 2010, researchers led by Catalina Pimiento, a paleobiologist at Swansea University, found possible evidence of a megalodon nursery off the coast of Panama. A number of juvenile megalodon teeth—the only remains the sharks left behind in the fossil record, as their skeletons were made of cartilage—at the 10-million-year-old site suggested youngsters may have lived there. But it was unclear whether the finding was a one-off or such nurseries were widespread.
In the new study, a separate team began to analyze a previously unexamined collection of 25 seemingly small megalodon teeth, all found in the past 20 years in northeastern Spain. They calculated that the teeth belonged to sharks as small as 2.6 meters, dating back to 15 million years ago. That’s less than one-quarter of the size of a full-grown megalodon, which could grow up to 15 meters, roughly the length of a humpback whale. The geology and other fossilized fauna where the specimens were found suggested it was once a shallower coastal area, notes study leader Carlos Martínez-Pérez, a paleobiologist at the University of Valencia, further indicating this could be a nursery site for young megalodons.
The researchers then gathered data on 485 megalodon teeth from eight other locations in the Pacific Ocean, Caribbean Sea, and the Atlantic Ocean. They estimated the sizes of the sharks and the known geographical history and paleoecology of the area. Four additional locations turned out to be potential nurseries 16 million to 3.6 million years ago, the team reports today in Biology Letters. “It puts everything into a global context,” Pimiento says.
The megalodon’s apparent reliance on nurseries brings up new ideas about what drove the great shark to extinction more than 3 million years ago, Martínez-Pérez says. Shoreline loss during that time may have reduced the availability of shallower, protected environments that baby megalodon relied on for survival, he speculates, perhaps driving the species to the brink.
sciencemag.org, 24 November 2020