Nearly 19 million years ago something caused the death of 90% of the world's open-ocean sharks. What happened to cause the massive kill off is a mystery to scientists.
Sharks are amazing ocean predators, and they're some of the most powerful creatures in the sea. But 75% of shark species are currently threatened with extinction.
The new study, in the journal Nature Communications, builds on findings from a 2020 study that concluded sharks were “functionally extinct” on 20% of the world's coral reefs.
Overfishing has driven the global abundance of oceanic sharks and rays to decline by nearly three-quarters (71%) in the past 50 years, says a global study published today in Nature.
About 19 million years ago, sharks had an extinction event of their own. Over 70 percent of the pelagic, or open-water, shark species disappeared, and their abundance dropped by 90 percent.
Researchers say that fossils found in sediment in the Pacific helped them see that some 19 million years ago the population of sharks plunged, but they can't say what it was that killed the ocean predator, according to an article in Science published earlier this month.
THE CENOZOIC ERA (65 million years ago - present day)
Hammerheads were the last of the modern shark families to evolve, and did so in the Cenozoic. Their evolution date is estimated at between 50 and 35 million years ago.
Overfishing and illegal fishing of sharks for their fins is depleting populations worldwide. There is often a general lack of even basic management monitoring, control, and surveillance of many fisheries.
Without sharks as apex predators, the entire ocean ecosystem could fall out of balance. They not only maintain the species below them in the food chain, but also indirectly maintain seagrass and coral reef habitats.
The USA and Australia are the most sharks infested countries in the world. Since the year 1580, a total of 682 shark attacks have killed more than 155 people in Australia. In the United States, 1,563 attacks have already caused over 35 deaths.
Since sharks help balance the ecosystem, their disappearance would lead to a catastrophic domino effect. Fish populations would explode out of control, leading to mass shortages of food and other marine resources.
The loss of sharks has led to the decline in coral reefs, seagrass beds and the loss of commercial fisheries. By taking sharks out of the coral reef ecosystem, the larger predatory fish, such as groupers, increase in abundance and feed on the herbivores.
Megalodons are extinct. They died out about 3.5 million years ago. And scientists know this because, once again, they looked at the teeth.
The earliest megalodon fossils (Otodus megalodon, previously known as Carcharodon or Carcharocles megalodon) date to 20 million years ago. For the next 13 million years the enormous shark dominated the oceans until becoming extinct just 3.6 million years ago.
Between 2,000 and 3,000 ancient shark species have been described based on the fossil evidence. Ancestry of sharks dates back before the earliest known dinosaur. Although the dinosaurs are long gone, sharks still live on.
Overfishing large predators such as shark, tuna and cod in the past 40 years has left the oceans out of balance, and could result in the disappearance of these fishes by 2050, according to Villy Christensen of the University of British Columbia's Fisheries Center.
How Many Sharks Are Killed a Year? Around 100 million sharks are killed each year worldwide, according to a paper published in Marine Policy in 2013.
How Many Sharks Are Killed Every Year? An estimated 100 million sharks are killed per year throughout the world, a startlingly high number and one that is greater than the recovery rate of these populations.
Here's a 'fun' statistic to consider – sharks have been on earth for around 450 million years surviving five mass extinction events, and so if we think of their existence as a 24 hour clock, overfishing has wreaked havoc in just 0.02 seconds!
Estimates show that there are as many as 1 billion sharks in the world. This means there's a shark for every seven or eight humans. They can be found in every ocean in the world and just about every oceanic habitat, including the open ocean, deep sea, coral reefs, shallows, and beneath Arctic ice.
Sharks have six highly refined senses: smell, hearing, touch, taste, sight, and electromagnetism. These finely honed senses, along with a sleek, torpedo-shaped body, make most sharks highly skilled hunters. They often serve as top predators - keeping populations of prey species in check.
Today there are two living coelacanth species, known as Latimeria, which have basically remained unchanged over the past 100 million years. Horseshoe crabs are ancient creatures that first appeared at least 480 million years ago during the Ordovician Period and don't appear to have changed much since.
Sharks have roamed the Earth's oceans for more than 400 million years. In the process, the animals have survived five mass extinction events, including the one that wiped out the dinosaurs. This latter extinction event occurred around 66 million years ago, marking the end of the Cretaceous period.
Sharks have roamed the world's oceans for hundreds of millions of years. In that time, many species have barely changed. But some strange sharks are still evolving—and have even learned to walk. Meet the walking sharks.