What is a dinosaur?
All groups of animals share common traits. Mammals are warm-blooded, have fur, and produce milk for their young. When finding common traits of dinosaurs, scientists relied on the fossil record – evidence left behind in the rocks over millions of years.
- Laid and hatched from eggs
- Had up-right posture rather than a sprawling posture like an alligator.
- Had specific structure of hip and thigh bones. The top of the thigh bone turned inward to fit inside the socket of the hip.
All dinosaurs belonged to one of two different groups:
- Ornithischia (bird-hipped dinosaurs), includes Triceratops, Stegosaurus, and Hadrosaurs (duck-billed dinosaurs)
- Saurischia (lizard-hipped dinosaurs), includes two-legged dinosaurs like Tyrannosaurus rex and Utahraptor as well as gigantic sauropods like Brachiosaurus and Apatosaurus.
How do we know what dinosaurs looked like?
Artists partnered with paleontologists to piece together the clues left behind in the fossil record to figure out what dinosaurs looked like. Fossilized bones give an idea of what the dinosaur’s structure and profile looked like… once scientists figure out how the bones fit together. Imprints of dinosaur skin and footprints, called trace fossils, tell the story of the texture of the dinosaur’s scales or feathers and even how the dinosaurs walked and interacted with their environment.
Artists and scientists also look at the rocks surrounding fossils to deduce the dinosaurs’ habitat. These rocks tell scientists if 180 million years ago the environment was a grassy plain or a dense mangrove forest.
As for dinosaur color, most representations are usually determined by the artist’s imagination. But advances in technology offer new insights. Microscopic structures called melanosomes are responsible for producing color in animals. They live in soft tissues like skin, feathers, and scales. New imaging technology identifies these melanosomes in fossilized dinosaur soft tissue. From there, scientists compare the fossilized melanosomes to modern melanosomes to figure out their color. Read more about dinosaur colors in the Smithsonian Magazine.
What dinosaurs are still alive today?
Dinosauria, the clade that encompasses all dinosaurs, went extinct 65 million years ago. But that doesn’t mean that all traces of dinosaurs are extinct from the living world.
In a scientific view, modern birds are a living group of dinosaurs. Birds descended from a group of dinosaurs called theropods, which included Tyrannosaurus rex, Allosaurus, and Dilophosaurus. This makes modern birds and dinosaurs similar to cousins.
How did dinosaurs go extinct?
The most common theory is that an asteroid hit the earth off the Gulf of Mexico 65 million years ago. Called the Chicxulub impactor, the crater left behind by the asteroid collision is 93 miles wide and 12 miles deep.
This asteroid impact caused the 5th mass extinction event, known as the Cretaceous–Paleogene extinction event. This event wiped out three-quarters of all plant and animal species on earth, including the dinosaurs. Notable survivors of the event can still be seen today, including sharks, reptiles, alligators, and birds.
How many dinosaurs are there?
So far, paleontologists have discovered about 700 species of dinosaurs across 300 different genera. However, scientists believe they have only scratched the surface in discovering new dinosaurs.
How do we know what dinosaurs sounded like?
Paleontologists glean clues from dinosaur skulls to figure out what dinosaurs might have sounded like. Some dinosaurs had crests on top of their heads that likely filled with air as the dinosaur breathed. The air could be pushed out of these crests to make a sound, similar to a horn.
Some dinosaur fossil remains included an organ called a syrinx. Today, syrinx are only found in bird and are used to vocalize all sorts of sounds, including honks and bird songs. By comparing the syrinx to the rest of the bone structures and then comparing those structures to living birds, scientists deduce what the dinosaurs sounded like.
Dr. Julia Clarke, a paleontologist from the University of Texas, believes that many carnivorous (meat-eating) dinosaurs used low-pitched, closed-mouth sounds. Imagine the T-rex from Jurassic Park, but instead of a bellowing roar, consider a crocodilian growl, cooing, or swooshing sounds.
You can read more about dinosaur sounds in this article from the Carnegie Museum of Natural History.