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.
Reptiles, such as crocodiles and lizards, have legs that sprawl out to the side. Their thigh bones are almost parallel to the ground. They walk and run with a side-to-side motion. Dinosaurs, on the other hand, stand with their legs positioned directly under their bodies.
Crocodiles
Well, crocodiles share a heritage with dinosaurs as part of a group known as archosaurs (“ruling reptiles”), who date back to the Early Triassic period (250 million years ago). The earliest crocodilian, meanwhile, evolved around 95 million years ago, in the Late Cretaceous period.
Alligators & Crocodiles: These sizeable reptiles survived–even though other large reptiles did not. Birds: Birds are the only dinosaurs to survive the mass extinction event 65 million years ago. Frogs & Salamanders: These seemingly delicate amphibians survived the extinction that wiped out larger animals.
Around 66 million years ago, at the end of the Cretaceous period, an asteroid struck the Earth, triggering a mass extinction that killed off the dinosaurs and some 75% of all species.
"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."
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.
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.
Surviving crocodiles did not change throughout millions of years because they arrived at an equilibrium where they were efficient and versatile enough that they did not need to evolve to exist, reports the Conversation.
When the meteor struck, temperatures on Earth's surface skyrocketed. Many animals had nowhere to flee, but roaches could take shelter in tiny soil crevices, which provide excellent protection from heat.
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!
Today's birds are the last of the dinosaurs, descendents of ancestors that didn't just survive this mass extinction, but evolutionarily exploded into thousands of species distributed around the world.
Evidence suggests an asteroid impact was the main culprit. Volcanic eruptions that caused large-scale climate change may also have been involved, together with more gradual changes to Earth's climate that happened over millions of years.
Crocodiles relatives are believed to have existed either before dinosaurs or right when dinosaurs first appeared! Crocodile ancestors date back 240 million years to the Triassic period, that's the same era that dinosaurs first began to flourish.
But paleontologists rarely find preserved gut contents in crocodilians, perhaps because their guts contained powerfully corrosive acids, as do those of modern crocodiles. This new find provides the first definitive evidence showing that dinosaurs were eaten by giant Cretaceous crocs, the scientists reported Feb.
For the first time, scientists have found indisputable evidence that an ancient crocodile ancestor chowed down on a dinosaur.
Another crocodilian expert, Adam Rosenblatt, told me that while the ageing process in these animals is still not fully understood, the evidence we do have "all points to the conclusion that crocodilians are not immortal and are subjected to natural ageing and death processes".
Genetic studies have demonstrated that humans are still evolving. To investigate which genes are undergoing natural selection, researchers looked into the data produced by the International HapMap Project and the 1000 Genomes Project.
Gigantism in crocodiles has been reported several times in the fossil record. In North America, the oldest body fossil evidence of giant crocodiles is of Deinosuchus at about 82 million years, estimated to have been between eight to 12 metres long.
Global water temperature dropped; that reduced the area where megalodon, a warm-water shark, could thrive. Second, because of the changing climate, entire species that megalodon preyed upon vanished forever. At the same time, competitors helped push megalodon to extinction – that includes the great white shark.
The cooling of the planet may have contributed to the extinction of the megalodon in a number of ways. As the adult sharks were dependent on tropical waters, the drop in ocean temperatures likely resulted in a significant loss of habitat.
“It would be a gigantic failure for humanity that would affect everything from coral reefs to food security and climate change. Once sharks are gone, there is nothing we can do to replace the critical role they play in the balance of the oceans."
Unfortunately, dinosaurs probably cannot be cloned and brought back to life. Their DNA is too old since dinosaurs have been extinct for over 65 million years. Any genetic information is not likely to survive for one million years, so the dinosaurs are simply too old to be cloned.
The dinosaurs went extinct around 66 million years ago and with so much time having passed it is very unlikely that any dinosaur DNA would remain today. While dinosaur bones can survive for millions of years, dinosaur DNA almost certainly does not. But some scientists continue to search for it - just in case.
Researchers have known that dinosaurs lived in polar regions since oil workers found dinosaur bones there in the 1950s, Erickson said. In the following decades, scientists with the University of Alaska Museum of the North discovered the remains of teensy baby dinosaurs in the state.