Fossil records suggest that at one point in history, there were more than 3,000 types of sharks and their relatives. Sharks managed to survive during extinction events when the ocean lost its oxygen – including the die off during the Cretaceous period, when many other large species were wiped out.
Sharks Have Survived Four Mass Extinctions, But Now, They're Endangered. They're older than the dinosaurs, they've survived four mass extinctions, and yet today, in the wake of climate change, pollution, and commercial fishing, sharks are endangered.
Sharks have survived many mass extinction during their presence of 450 million years on Earth. Scientists believe that their ability to repair damaged DNA has helped them survive over the years. Their presence on the planet over millions of years have earned them the title of living fossil.
In fact, sharks and their relatives were the first vertebrate predators on Earth. Shark fossils date back more than 400 million years – that means sharks managed to outlive the dinosaurs, survive mass extinctions, and continue to serve an important role near the top of underwater food chains.
Now new research, detailed online July 11 in the Journal of Geophysical Research-Biogeosciences, suggests freshwater life survived extinction because they were better adapted to withstand rapid changes in their surroundings, which helped them outlast the crises in the wake of the catastrophe.
There are two main reasons. First, crocodiles can live for a very long time without food. Second, they lived in places that were the least affected when the asteroid hit Earth.
Fossil records suggest that at one point in history, there were more than 3,000 types of sharks and their relatives. Sharks managed to survive during extinction events when the ocean lost its oxygen – including the die off during the Cretaceous period, when many other large species were wiped out.
In fact, birds are commonly thought to be the only animals around today that are direct descendants of dinosaurs. So next time you visit a farm, take a moment to think about it. All those squawking chickens are actually the closest living relatives of the most incredible predator the world has ever known!
Land walking is a more recent trend for the epaulette sharks, as only younger members of the species have been recorded doing it. Utilizing their fins as leg-like appendages, the sharks search for prey in reef regions where other sharks can not tread.
Shark ancestor could walk before land animals | PerthNow. A common ancestor of sharks and mammals had the ability to walk on land 400 million years ago Credit: Supplied.
The tardigrade (water bear) has survived all 5 major mass extinction.
As a group, sharks have been around for at least 420 million years, meaning they have survived four of the “big five” mass extinctions. That makes them older than humanity, older than Mount Everest, older than dinosaurs, older even than trees.
“It's a great mystery,” Elizabeth Sibert, a paleobiologist and oceanographer at Yale University, told Science News. “Sharks have been around for 400 million years. They've been through hell and back. And yet this event wiped out (up to) 90% of them.”
Internet rumors persist that modern-day megalodons exist – that they still swim around in today's oceans. But that's not true. Megalodons are extinct. They died out about 3.5 million years ago.
Fun fact of the day: Sharks are older than trees. The earliest species that we could classify as “tree,” the now-extinct Archaeopteris, lived around 350 million years ago, in forests where the Sahara desert is now. But Sharks? They laugh at trees.
So, while most sharks will be 100% fine if they stop swimming, a few iconic species such as great white sharks, whale sharks, hammerheads and mako sharks would suffocate without forward motion or a strong current flowing towards their mouths.
Epaulette sharks (Hemiscyllium ocellatum) are about 3 feet long with paddle-shaped fins they use to walk, whether across the ocean floor or on dry land. They live in shallow waters amid coral reefs in the western Pacific Ocean around New Guinea and northern Australia.
Sharks do not have bones.
Their cartilaginous skeletons are much lighter than true bone and their large livers are full of low-density oils, both helping them to be buoyant. Even though sharks don't have bones, they still can fossilize.
Other than birds, however, there is no scientific evidence that any dinosaurs, such as Tyrannosaurus, Velociraptor, Apatosaurus, Stegosaurus, or Triceratops, are still alive. These, and all other non-avian dinosaurs became extinct at least 65 million years ago at the end of the Cretaceous Period.
Thus, modern birds or avian dinosaurs are alive and the other types of dinosaurs are extinct.
“If we speculate that humans had evolved alongside dinosaurs, then they probably would have been able to co-exist,” says Farke. “Humans already evolved in ecosystems that had large land animals and predators. We probably would have done okay.”
"If dinosaurs didn't go extinct, mammals probably would've remained in the shadows, as they had been for over a hundred million years," says Brusatte. "Humans, then, probably would've never been here."
When the smaller species came out of hiding they found a charred landscape and the air so thick with soot and sulphur dioxide clouds that sunlight was almost completely blocked out for the next year. It was too dark for photosynthesis, so the herbivores died, then the carnivores.
Sixty-six million years ago, dinosaurs had the ultimate bad day. With a devastating asteroid impact, a reign that had lasted 180 million years was abruptly ended. Prof Paul Barrett, a dinosaur researcher at the Museum, explains what is thought to have happened the day the dinosaurs died.