Dinosaurs
1. In the early 1800s people in England were fascinated with fossils. Fossils are the remains of living things that have been preserved in rock. Dinosaurs' fossils were found on nearly every continent. Mostly found in China and the United States.People found giant bones and wondered what animals they belonged to. They had never heard of dinosaurs.
2. In 1842, Richard Owen was the first person to use the word dinosaur, which means "fearfully great lizard."Fossils are buried deep in the ground. They come to the surface when the ground wears away or is dug up. A dead dinosaur sank in the mud or was covered by sand blown by the wind.Over a long period of time, the layer of mud or sand thickened and became hard rock. The animal remains hardened and turned into stone. This is called fossilization.
3. Movement of the earth's crust and erosion caused the fossils to rise back up to the surface.Scientists who study fossils are called paleontologists. The first thing a paleontologist does when fossils have been found is to make a detailed map of the bones.
4. They take measurements, make drawings, and take photographs.Fossil bones are wrapped in strips of plaster. Then they are transported to a laboratory, where they are identified. Once scientists put together a skeleton, they can figure out where the muscles went by marks they leave on bones.
5. Fossils are fragile. They have to be removed very carefully. Paleontologists use brushes, chisels, hammers, and picks. Scientists have learned more about dinosaurs by studying the footprints they left in the ground.Earth is about 4.5 billion years old.
6. Many kinds of animals or species have lived on Earth. Then the species died, or evolved into other species. The species called dinosaurs once lived all over the Earth.Many animals and plants already lived on Earth at the time. But not humans. We didn't appear until around 100,000 years ago. Around 65 million years ago, dinosaurs disappeared--- they became extinct.
7. Dinosaurs lived over a period of 170 million years. Some were enormous. Others were as small as chickens! But they all had certain characteristics in common. They had scaly skin. They laid eggs.They walked upright on their feet instead of crawling like other reptiles.
8. Dinosaurs are classified into two main groups according to their hips. Saurischians were "lizard-hipped" dinosaurs. Ornithischians were "bird-hipped" dinosaurs.All ornithischians, and some saurischians, were plant eaters, or herbivores. Other saurischians were meat eaters, or carnivores.
9. Plant-eating dinosaurs were the first animals able to reach treetops and eat the leaves. Carnivores gathered together in groups to hunt and feed off other animals.Scientists still don't know why dinosaurs completely disappeared 65 million years ago, while other animals survived. A meteorite may have crashed into Earth. There may have been gigantic volcanic eruptions.
10. Dinosaurs may have lost in competition with other species.After the Dinosaurs, other reptiles, however, survived. Fish and amphibans continued evolving. Mammals appeared at the same time as dinosaurs, 235 million years ago. They spread all over the earth. Mammals are warm-blooded. Their babies develop inside their mother before being born. At birth, they are nourished by their mother's milk.
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1. In the early 1800s people in England were fascinated with fossils. Fossils are the remains of living things that have been preserved in rock. Dinosaurs' fossils were found on nearly every continent. Mostly found in China and the United States.People found giant bones and wondered what animals they belonged to. They had never heard of dinosaurs.
2. In 1842, Richard Owen was the first person to use the word dinosaur, which means "fearfully great lizard."Fossils are buried deep in the ground. They come to the surface when the ground wears away or is dug up. A dead dinosaur sank in the mud or was covered by sand blown by the wind.Over a long period of time, the layer of mud or sand thickened and became hard rock. The animal remains hardened and turned into stone. This is called fossilization.
3. Movement of the earth's crust and erosion caused the fossils to rise back up to the surface.Scientists who study fossils are called paleontologists. The first thing a paleontologist does when fossils have been found is to make a detailed map of the bones.
4. They take measurements, make drawings, and take photographs.Fossil bones are wrapped in strips of plaster. Then they are transported to a laboratory, where they are identified. Once scientists put together a skeleton, they can figure out where the muscles went by marks they leave on bones.
5. Fossils are fragile. They have to be removed very carefully. Paleontologists use brushes, chisels, hammers, and picks. Scientists have learned more about dinosaurs by studying the footprints they left in the ground.Earth is about 4.5 billion years old.
6. Many kinds of animals or species have lived on Earth. Then the species died, or evolved into other species. The species called dinosaurs once lived all over the Earth.Many animals and plants already lived on Earth at the time. But not humans. We didn't appear until around 100,000 years ago. Around 65 million years ago, dinosaurs disappeared--- they became extinct.
7. Dinosaurs lived over a period of 170 million years. Some were enormous. Others were as small as chickens! But they all had certain characteristics in common. They had scaly skin. They laid eggs.They walked upright on their feet instead of crawling like other reptiles.
8. Dinosaurs are classified into two main groups according to their hips. Saurischians were "lizard-hipped" dinosaurs. Ornithischians were "bird-hipped" dinosaurs.All ornithischians, and some saurischians, were plant eaters, or herbivores. Other saurischians were meat eaters, or carnivores.
9. Plant-eating dinosaurs were the first animals able to reach treetops and eat the leaves. Carnivores gathered together in groups to hunt and feed off other animals.Scientists still don't know why dinosaurs completely disappeared 65 million years ago, while other animals survived. A meteorite may have crashed into Earth. There may have been gigantic volcanic eruptions.
10. Dinosaurs may have lost in competition with other species.After the Dinosaurs, other reptiles, however, survived. Fish and amphibans continued evolving. Mammals appeared at the same time as dinosaurs, 235 million years ago. They spread all over the earth. Mammals are warm-blooded. Their babies develop inside their mother before being born. At birth, they are nourished by their mother's milk.
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