Researchers Find Ancient Extinction Event Among Large Marine Creatures

More than a third of large ocean-dwelling species disappeared roughly 2 million years ago

A large number of ancient marine species, including the massive megalodon shark, disappeared in a marine extinction event roughly 2 million years ago. MasPix/Alamy

Millions of years ago, gigantic creatures dominated the planet. While animals like wooly mammoths and cave bears wandered the lands, massive megalodon sharks and sea sloths took to the seas.

During the last ice age, which ended roughly 11,700 years ago, many of these large land animals perished in a mass extinction event. But researchers have long thought that ocean-dwelling creatures resisted the changes that eliminated so many land dwellers. Now, new research suggests that isn't the case. As UPI’s Brooks Hays reports, after a recent statistical analysis of the marine fossil record, researchers were surprised to find that before the ice age wiped out many large land creatures, a mass extinction event swept through the seas.

The death toll was high. The analysis suggests large drops in the genetic diversity, or number of species, at the time. There was a reduction of up to 55 percent of marine mammals, 43 percent of sea turtles, 35 percent of sea birds, and nine percent of sharks. Seven groups of animals in costal waters known as functional entities—creatures that serve the same purpose in their ecosystems—were also lost, reports Hays.

In a press release, the team says that the loss, which totaled roughly one third of all large marine creatures, is “relatively modest.” But the creatures themselves were impressive. The event took out giant sea sloths, turtle species and massive sharks like the megalodon, a 50-foot-long beast. According to the researchers, these sea animals were likely more fragile than previously thought. 

The extinction event also impacted the rest of Earth. Without the usual animals swimming the seas, new predators emerged. Competition between species likely changed, and animals had to adapt to their new environment. Sea levels also are thought to have dramatically shifted at the time, so the coastal habitats that supported marine life were affected.

There was an upside, though: Room for new species meant that other megafauna came into existence. Animals like the yellow-eyed penguin and the polar bear eventually developed to fill the gap.

So why did all that marine life die? The team thinks that habitat loss—mainly due to shifting sea levels—drove most of the change. And they draw connections between this ancient event and what’s happening with Earth’s climate today.

As human-caused climate change speeds up, they warn, “the potential consequences for marine megafauna should not be underestimated.” The marine giants of the Pliocene and Pleistocene may have died in large numbers, but there’s still a chance to save the animals of the Anthropocene.

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