It boasted a 9-foot-long jaw of razor-sharp teeth and nose-to-tail lengths of up to 60 feet—three times that of an average Great White shark. As the largest shark to have ever lived, the Carcharocles megalodon commanded the ocean for more than 20 million years.

Then, suddenly, the massive, fearsome predator vanished, a mystery that has plagued paleontologists for years.

But a study published in late June in the journal Nature Ecology & Evolution has concluded that the disappearance was actually part of a larger underwater extinction.

In addition to the megalodon, one-third of the largest creatures, or megafauna, to have lived underwater became extinct during the Pliocene Epoch, the era during which they had thrived.

The study, published by researchers from the Paleontological Institute and Museum of the University of Zurich, revealed that this mass extinction mimics the more commonly known one during the Ice Age.

“It’s astonishing that an extinction even like this, among the biggest animals in the oceans, could go undetected until now,” study co-author Dr. John Griffin of Swansea University, in Wales, U.K., told the ITV network. “It overturns the assumption that the oceans’ biodiversity was resistance to the environmental change in Earth’s recent history.”

(Credit: Reinhard Dirscherl/ullstein bild via Getty Images)
(Credit: Reinhard Dirscherl/ullstein bild via Getty Images)

Among the creatures lost in the Pliocene-era extinction event were seabirds, turtles, marine mammals and sharks. By comparing that Epoch to one just after it (the Pleistocene), scientists concluded that around half the species of marine mammals from the earlier period had disappeared.

Of the marine megafauna specifically, 36 percent became extinct as a result of the event, with warm-blooded animals being particularly susceptible. That analysis includes a loss of 43 percent of sea turtles, 35 percent of sea birds and 9 percent of sharks.

Scientists don’t know what caused the extinction, but have hypothesized that it resulted from natural environmental changes to the coasts.

According to the authors of the Nature Ecology & Evolution paper: “We hypothesize that the abrupt loss of productive coastal habitats, potentially acting alongside oceanographic alterations, was a key extinction driver.”

Based on their findings, the researchers have concluded that marine megafauna are more susceptible to changes in the environment than previously thought. They plan to use that information to better analyze and predict the status of current giants of the sea.