Did all dinosaurs turn out to be extinct, killed when an asteroid hit the Earth 66 million years in the past? Or may just a few of them, by some means, have survived that mass extinction occasion – with their descendants residing even at this time?
It’s thrilling to think about that big dinosaurs are nonetheless rumbling and lumbering round in some distant a part of the world. However no proof of this exists. There are not any cousins of Tyrannosaurus rex stomping by the huge woods of Siberia, no Apatosaurus ambling by the Congo rainforest.
As a paleontologist, I’ve spent a lot of my life finding out historic animals, notably dinosaurs. However I’ve seen solely fossils of those creatures, nothing residing – with one exception. One group of dinosaurs continues to be round. To search out them, simply go outdoors and lookup.
Ankylosaurus was a plant-eating dinosaur with physique armor and a tail membership that might kill any attacker. (Credit score: Daniel Eskridge/iStock through Getty Pictures Plus)
The Killer Asteroid
In 1977, American geologist Walter Alvarez was working within the Apennine mountains in Italy. There, he discovered a skinny layer of clay with an uncommon quantity of metallic known as iridium in. The clay was in between rocks from the Cretaceous and Paleogenedurations and dates from the time the dinosaurs disappeared.
Iridium is uncommon on Earth however extra frequent in some meteorites. Working along with his father, Luis, who was a Nobel-Prize-winning physicist, Walter Alvarez developed the idea {that a} large area rock – an asteroid– collided with Earth 66 million years in the past. This influence left iridium traces all over the world and triggered the unimaginable catastrophe that killed the dinosaurs and numerous different species of animals and crops on land and within the sea.
At first, many scientists rejected the idea. However then, in 1991, geologists found an enormous crater buried below the ocean ground off the Yucatán Peninsula of Mexico. This spot was the place an asteroid, about 6 miles (10 kilometers) throughout, crashed into our planet 66 million years in the past.
The collision was so highly effective it despatched trillions of tons of mud and molten rock into the sky. Many items of molten rock fell again to Earth, inflicting big wildfires in all places. A thick blanket of mud within the ambiance blocked most daylight, resulting in freezing temperatures worldwide. Earth changed into a chilly, desolate place for a few years, even centuries.
The lack of daylight killed many crops. With no meals obtainable for them, huge plant-eating dinosaurs like Triceratops rapidly went extinct. That left huge predators like Tyrannosaurus rex with out prey animals to eat, in order that they died, too.
However smaller animals like mammals, lizards, and turtles may adapt. They may conceal in burrows and stay on all kinds of meals. Fish lived in rivers and lakes and have been protected by their watery houses. And surviving with them: birds, the one remaining dinosaurs.
The grownup Deinonychus weighed as much as 220 kilos (100 kilograms). (Credit score: SCIEPRO/Science Photograph library through Getty Pictures)
The Fowl Connection
Quick-forward about 66 million years: Scientists seen within the nineteenth century how the skeletons of recent birds and fossilized dinosaurs have been alike in some ways. The similarities within the legs and toes have been particularly putting. Nonetheless, most scientists then thought dinosaurs and birds have been too totally different to be intently associated.
Then, in 1964, dinosaur professional John Ostrom found fossils of the dinosaur Deinonychus. It had a mouth filled with sharp enamel with serrated edges like steak knives, lengthy slender fingers with three fingers ending with giant, curved claws, and an enormous claw on the second toe of every foot. A quick hunter that didn’t match the standard concepts about dinosaurs as sluggish and never very energetic, Deinonychus lived in North America through the Cretaceous interval, about 110 million years in the past.
For an additional analysis mission within the early Seventies, Ostrom examined the earliest recognized fowl, Archaeopteryx, which lived 150 million years in the past in what’s now Germany. It had feathered wings and a wishbone, together with reptilelike traits, together with jaws with sharp enamel, fingers with three fingers every, and an extended tail.
Evaluating this historic fowl with Deinonychus, Ostrom realized their skeletons shared many particular options. For instance, each had unusually lengthy arms and fingers, a really versatile wrist, hole bones, and an S-shaped neck.
Based mostly on these and plenty of different similarities, Ostrom confirmed that birds descended from small, predatory, birdlike dinosaurs.
With sharp enamel and an extended, bony tail, Archaeopteryx is a hyperlink to dinosaurs and modern-day birds. (Credit score: Leonello Calvetti/Science Photograph Library through Getty Pictures)
Previously three a long time, paleontologists have found many skeletons of historic birds and birdlike dinosaurs in Jurassic and Cretaceous rocks in China. Surprisingly, the birdlike dinosaurs, together with shut kin of Deinonychus, have been lined in feathers, similar to the birds residing with them. Paleontologists now agree that many, if not all, dinosaurs maintained fixed excessive physique temperatures, similar to birds and mammals do at this time. Feathers saved them heat.
Birdlike dinosaurs didn’t make it by the extinction occasion 66 million years in the past – however among the early birds who had lived alongside them did. They usually advanced into the birds alive at this time.
Consider that: to see a dinosaur, all you want do is look skyward. And as somebody who has studied dinosaurs for a very long time, I’m joyful to know I share the world with dinosaurs.
Hans Sues is a Senior Analysis Geologist and Curator of Vertebrate Paleontology on the Smithsonian Establishment. This text is republished from The Dialog below a Inventive Commons license. Learn the unique article.
