In the entire history of its existence, the world has experienced five mass extinctions (or 8, depending on which classification you adhere to). The worst of these was the Great Extinction 252 million years ago, caused by catastrophic volcanic eruptions and wiping out 96 percent of all species.
However, some "minor" extinctions, understandably, may have escaped our attention. For example, scientists have long suspected that there was a significant extinction during the transition between the Pliocene and Pleistocene (about 2.6 million years ago), but they find it difficult to determine how catastrophic it was.
Now, a new study by scientists from the University of Zurich has shown that, before the planet's famous megafauna - woolly mammoths and saber-toothed cats - was influenced by many antagonistic factors, the oceans also suffered losses.
This transition between the two geological eras heralded a warm climate change and the onset of extensive glaciation, which appears to have caused a rapid drop in ocean levels and significant water cooling.
Why marine megafauna died out
Based on a new assessment of the fossil record, scientists concluded that this was enough to kill a surprisingly large number of large sea creatures: in total, a third of the marine megafauna became extinct during this transition.
Marine mammals suffered the most, losing 55% of their diversity. In addition, about 35% of seabirds and 43% of sea turtles are extinct. It is noteworthy that during this time only 9 percent of sharks became extinct, but among them there was a rather noticeable and important species.
The disappearance of megalodon
We are, of course, talking about the megalodon - one of the largest and most feared predators in the history of the planet, which grew up to 18 meters. It is interesting that from time to time on the Web there are speculations that this terrible beast is still hiding somewhere in the depths of the oceans.
Despite all these stories, scientists have clearly determined that these megalodons became extinct 2.6 million years ago. Ever since fossil evidence of their existence was first discovered, scientists have been trying to figure out why this happened. Various factors have been proposed, including food chain collapse, excessive competition from other animals, and sudden ocean cooling.
Self-destruction of the food chain
The results of a new study on this topic have been published in the journal Nature Ecology & Evolution. Scientists speculate that the loss of coastal habitat biodiversity due to declining sea levels was enough to trigger a mass extinction that even the ancient giant shark could not survive. In fact, the self-destructive food chain became the cause of the extinction of the megalodon.
"The discovery of this extinction event shows that the biological diversity of the marine megafauna is more sensitive to changes that have occurred in the environment than previously thought," the scientists write. They then refer to contemporary anthropogenic climate change, noting that its "potential impact on marine megafauna should not be underestimated."