How many years were dinosaurs the dominant creature on Earth?
About 165 million years. The “Age of Dinosaurs,” called the Mesozoic Era of life on our planet, is made up of three geologic Periods – first the Triassic, then the Jurassic, and finally the Cretaceous. These three covered a time span of 169 million years, ending about 66 million years ago. (Our Earth is an old planet!) About 900 different species of dinosaurs existed over the span of those many years.
What happened to dinosaurs?
During the millions of years dinosaurs roamed Earth, species emerged and evolved. About 66 million years ago, dinosaurs became extinct, most likely as a result of an asteroid striking our planet possibly in a region of Mexico. Like the hugest volcano imaginable, tons of rock, dust and fire affected our atmosphere with debris and toxic smoke so thick that sunlight couldn't get through. All over Earth, it was like winter when it's hard to grow food. 75% of all animal species – including dinosaurs – and 50% of all plant species did not survive this change in climate that took 200,000 years – yup! that's 2,000 centuries! - to improve enough for new plants and animals to develop. Some life forms did survive the big extinction. You see some of them every day. Birds are descendants of dinosaurs, the smaller theropod or fierce foot species. Think about it... and look at any bird.
What physical characteristics of birds remind you of a dinosaur?
On the exterior surface, the scale pattern of bird skin resembles modern-day lizards as well as ancient terrible lizards. Even feathers are a kind of scale. And talons – those sharp hooked claws like toenails – are similar to dinosaurs'.
On the inside of their bodies, birds and some dinosaurs share bones we call hollow that are really made up of a network of struts and air pockets, just perfect for flight. Another bone birds have and dinosaurs had is the wishbone, just below the throat, that also helps birds to fly. One dinosaur was called Ichthyornis (ik-thee-OR-nis) - ichthy means fish, and ornis refers to bird. This “fishbird” had a spine that was similar to a fish but was the size of a pigeon and may have looked a little like a seagull because of the design of its jaw that came to a toothless beak.
Small dinosaurs with beaks may have survived extinction because they could dig at the ground for seeds, even hard seeds, that got digested by an organ called a gizzard that is still part of a bird's stomach. Dinosaur species that evolved into birds were very small and were bipedal; they walked on two feet. One such avian dinosaur was Archaeopteryx (ar-kee-OP-ter-ix) that weighed only two pounds. Velociraptors (vuh-LAH-suh-rap-ters) that most of us know from the “Jurassic Park” movies weighed about 100 pounds but were so much smaller than a dinosaur such as Tyrannosaurus rex!
What about bird brains?
Today we think the phrase bird brain means someone stupid – without much going on in the brain department! But back when a scientist named Darwin recognized that species evolve over time, depending on many environmental factors, he popularized the phrase survival of the fittest. That often also meant survival of the smartest. Bird ancestors who did survive succeeded in part because of their brains. In fact, modern birds have very complex brains, second only to the brains of mammals (including humans).
Some avian dinosaurs also had impressive brains. One theory is that the first ancestors of birds were larger creatures. As these creatures evolved, becoming smaller to survive, their brains remained large. By examining the fossilized skulls of various dinosaurs, avian dinosaurs with more complex brains survived while those with a simpler brain did not. It's possible that being smarter helped the dinosaur ancestors of birds survive extinction because they found ways to adapt to the Earth's changing surface and atmospheric conditions.
When did humans first recognize such creatures as dinosaurs?
Not until the 1600s - 400 years ago – did people start to study dinosaur fossils, mistaking them for bones of giant humans as if there were such beings. It wasn't until the 1800s - 200 years ago - that scientists realized fossils were bones of ancient – really ancient! - dinosaurs. The word dinosaur was first used in 1842, created from two Greek words – deinos (terrible) and sauros (lizard). Often big bones were found buried in the earth, and sometimes mold fossils were discovered – a mold or shape of a footprint or a feather or even a leaf that had hardened in mud. Now in our modern times, we have much more advanced technology, such as carbon dating, that helps us identify fossils and the time period they came from. When studying the development of birds and their various species, we now use genetic testing to look deep into avian history.
What do we still not know about avian dinosaurs and their connection to modern birds?
We don’t know where or when modern birds first existed. We don’t know exactly what species evolved into a true bird as we define it or what the steps were in this evolution. We do not know when or how flight evolved. But we do know that paleontologists – those people who study ancient things – are always discovering something new. Eventually we will solve those mysteries.
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