CONTENTS Introduction . . . 1 What Are Fossils? Chapter 1 . . . 10 From the Rocks
Chapter 5 . . . 51 Plant-Eating Dinosaurs
Chapter 2 . . . 21 Clues to the Past
Chapter 6 . . . 61 Meat-Eating Dinosaurs
Chapter 3 . . . 32 Plants and Microbe Fossils
Chapter 7 . . . 70 Boom and Bust
Chapter 4 . . . 42 Animals, Including Humans!
Chapter 8 . . . 79 How Paleontologists Work
Glossary * Metric Conversions Resources * Investigate Essential Questions Index
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KE YW OR D PR OM PTS fossil discoveries
CHAPTER 1
FROM THE ROCKS Fossils tell the story of ancient life. But it’s not easy to go from being a living organism to being a fossil. It’s a complicated process that can take millions of years! Fossils come in different shapes and sizes. They are divided into three types: ** body fossils
** trace fossils
** chemical fossils
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INVESTIGATE!
What can fossils tell us about the kinds of environments that existed long ago?
From the Rocks
TRACE FOSSILS are formed
of wood that has been turned to stone.
amber: hard, fossilized resin. Resin is a sticky substance that oozes from trees.
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organisms. This kind of fossil includes the hard parts of animals, such as bones, teeth, and shells. Petrified wood , seeds, and seed casings are other examples of body fossils. An entire organism trapped in amber is a body fossil.
petrified wood: a fossil
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BODY FOSSILS are made from the bodies of
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when an organism acts A PALE on its environment. CALL O U S ANY WO NTO T O E You can think of Y G RK R E it as fossilized behavior. Foot or paw prints, claw marks, and marks from a tail dragging in sand or mud are all trace fossils. Nests, eggs, burrows, holes, and spaces left by roots of ! es n o Laz y b plants are more examples. Even poop can turn into a fossil! Fossilized poop that turned to stone long ago is called coprolite. Another group of trace fossils are called gastroliths. These are stones found in the stomachs of some animals. The stones help digest food.
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EXPLORE carbon: an element found
in living things, including plants. Carbon is also found in diamonds, charcoal, and graphite.
sedimentary rocks: rocks
formed from sediments or the remains of plants or animals. Sedimentary rock can also form from the evaporation of seawater.
sediments: small particles of rocks or minerals, such as clay, sand, or pebbles. evaporation: when a liquid
heats up and changes to a gas.
CHEMICAL FOSSILS are chemicals
found in rocks that were made by living creatures long ago. They include away of rock or soil by water natural gas and oil. Some of the oldest and wind. evidence of life comes from a certain OR type of carbon that was produced by D S TO K N O microorganisms nearly 3.5 billion years ago.
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erosion: the gradual wearing
SEDIMENTARY ROCKS
Most fossils form in sedimentary rocks . These are rocks made from sediments such as sand or mud. The sediments are pressed tightly and often cemented together to form stone. Sedimentary rock can also form from the evaporation of seawater.
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Rain, wind, and ice break larger rocks into smaller and smaller pieces. This is a process called weathering, or erosion .
From the Rocks
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Water or air carries the sediments to other places while breaking them into even smaller pieces. As more sediments land in one area, they get buried deeper and pressed together. Heat and pressure change the soft sediments into hard sedimentary rocks.
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Sedimentary rocks can have layers of l! hil different kinds of rock, one on top of the other. s In a fo s When they first form, the layers are horizontal. Once they become rocks, the layers can tilt or fold because of forces in the earth. Different sedimentary rocks form in different environments. A river might carry small and large sizes of sediments. The ocean floor usually contains tiny sediments, or mud. Sedimentary rocks are forming all of the time, even right now!
HOW A FOSSIL FORMS
decay: to rot.
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Most plants and animals never become fossils. They decay first. Lots of steps have to happen for an organism to become a fossil.
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EXPLORE minerals: solids that
are found in rocks and in the ground. Rocks are made of minerals. Gold and diamonds are precious minerals.
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When a plant or animal dies, the remains usually break apart or are eaten by other creatures. But sometimes they are buried quickly by sediments such as sand or mud. Then they have the chance to become fossils.
The soft tissue, including the skin, usually rots away. Water with minerals dissolved in it seeps into the sediments and fills the tiny pores in the bones and shells. In rare cases, even the soft parts of a plant or animal, such as skin and organs, are replaced by minerals.
More sediments pile on. The pressure and heat from the weight of all of those sediments harden the mineral solution and the surrounding sediments into rock. A fossil is born! Much later, the rock might be lifted up by movements in the earth. If the rocks above the fossil are eroded by wind, water, and ice, it leaves the fossil exposed to be found by us.
Footprints and other trace fossils are formed when an organism makes a mark in sand or mud. The mark is covered and filled in by sediment, which then hardens into a fossil.
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From the Rocks Middle Ages: the
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People have been interested in fossils for a long time. But they didn’t always understand what fossils were or where they came from.
name for a period of time from around the years 350 to 1450.
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EARLY FOSSIL HUNTERS
Long ago, people thought fossils came from the sky or grew from the earth. The ancient Chinese thought that large fossilized dinosaur bones came from flying dragons. In the Middle Ages , Europeans thought fossils were the remains of Noah’s flood. Maybe giant bones came from giant humans.
In the 1600s, a Danish physician and priest named Nicolas Steno studied fossils. He was one of the first people to prove that fossils are the remains of once-living organisms. Steno compared tongue-shaped stones with the teeth of living sharks. He showed that they were teeth from ancient sharks.
THE FATHER OF PALEONTOLOGY Georges Cuvier is sometimes called the “Father of Paleontology.” He showed that rock layers in one area could be matched to rocks in other areas based on the fossils contained in the rocks. Cuvier proved that animals can become extinct. This was a crazy idea at the time! He compared the remains of elephants to fossils of mammoths to show they weren’t the same species. You can compare the remains too. What is different about these two jawbones?
KE YW OR D PR OM PTS Cuvier mammoth jaw
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EXPLORE evolve: to change
over time, sometimes into something more complex.
theory of evolution:
a scientific theory that explains how species change over time.
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Richard Owen described the fossil Archaeopteryx in 1863. It had wings like a bird and teeth like a dinosaur. Archaeopteryx was shown to be a bridge between dinosaurs and birds.
Paleontologist Charles Lyell showed that there was a sequence of fossils through time. Charles Darwin combined Lyell’s observations with his own of the natural world. He suggested that new species evolve over time. In 1859, Darwin published On the Origin of Species, which explained the theory of evolution .
Scientists have taken the understanding developed by these early scientists and expanded it. Now, we have a good understanding of the development of life on earth through time from fossils.
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INVESTIGATE!
It’s time to consider and discuss: What can fossils tell us about the kinds of environments that existed long ago?
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SOAP EROSION Rocks are eroded by wind, water, and ice. Try this activity to get an idea of one way a rock can erode.
**bar of soap **sponge slightly larger than the soap **kitchen or bathroom sink
1 Place the bar of soap on top of the sponge. Set
the sponge under the faucet of the kitchen or bathroom sink. Let the rest of your family know what you’re doing so they won’t disturb your experiment!
2 Start a scientific method worksheet in your
study journal. What do you think will happen to the soap after sitting under dripping water for 5 minutes? An hour? Two hours?
3 Turn the faucet on so that it slowly
drips water onto the soap.
4 Check back after a few
minutes and again after about an hour. Does the soap look different? If not, keep the soap under the dripping faucet longer.
THINGS TO NOTICE: How has the dripping water changed the
appearance of the soap? Would it take the water a shorter or longer amount of time to erode rock compared with soap? Why? What would happen if you increased or decreased how fast the water drips? Try it out and see if your predictions are correct.
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SEDIMENTARY SUCCESSION TREAT Sedimentary rocks are sometimes made up of different layers that form in different environments. Over millions of years, the sea level rises and lowers, creating different environments in the same place. Use your imagination and yummy ingredients to make a sedimentary rock you can eat! Imagine you are standing in a river that flows into the ocean. The river contains pebbles, gravel, sand, and mud that are deposited near where you are standing.
**clear plastic cup **M&Ms, chocolate chips, and candy bars broken into different size pieces **Rice Krispies cereal **Oreos or other similar cookies, crushed into fine pieces **spoon **milk
1 In the bottom of the cup, place a layer of large and small pieces
of candy bars, chocolate chips, and M&Ms. This represents different-sized sediments from a river.
2 Imagine the sea level rises and now you’re standing on a
beach. What are you standing on? Put a layer of Rice Krispies into your cup to represent sand.
3 Imagine the sea level rises again. You’re still in the same place,
but 10 feet underwater! Put a layer of crushed Oreos in the cup. to represent the mud that settles at the bottom of the ocean.
4 Imagine the sea level goes down, then goes down again. Put
a layer of Rice Krispies in the cup to represent beach sand, then a layer of large and small pieces of candy, chocolate chips, and M&Ms to represent the river sediments.
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law of superposition:
5 Press down the layers in your cup
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to represent the compression from the weight of sediments. Pour milk into the cup to represent water with minerals that cements sediments together into rock.
the scientific law that sedimentary layers are deposited with the oldest on the bottom and the youngest on top.
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6 Look at the layers from the side. You should see rocks on the bottom, then sandstone, then mudstone, then sandstone, and rocks on top. Draw and label the layers in your science journal. Now dig in!
THINGS TO NOTICE: All of these sediments were
deposited in the same place, but in different environments. If the sea level rose again, what layer would be deposited next? If you saw the face of a cliff with layers of sand, then mud, then sand, then mud, what might that tell you about changes in the sea level over time?
THE LAW OF SUPERPOSITION One of the concepts in geology is the law of superposition. This says that sedimentary layers are deposited with the oldest on the bottom and the youngest on top. If you started hiking in the valley and saw the youngest rock, then saw the oldest rock with seashells higher up on the mountain, would this still follow the law of superposition? Are older rocks always lower in elevation than younger rocks?
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MAKE YOUR OWN MOUNTAIN Rocks and fossils are deposited in an orderly fashion, with the oldest on the bottom and youngest on top. But forces in the earth sometimes move rocks and their fossils into different positions. Try this activity to see how that happens.
**at least 3 colors of play clay **butter knife **rolling pin **small seashells or plastic animals **small human figure (optional)
1 Roll out each color of clay to about 6 inches wide
and ¼-inch thick. These are your layers of rocks.
2 Push the shells or plastic animals into one of the layers of clay. This layer represents the rock that forms at the bottom of an ocean, and it is the oldest rock. Stack the layers of clay, with the oldest layer of clay on the bottom.
3 With the layers flat on the table, push from both sides. If the
clay sticks to the table, lift the middle up into a fold. Your hands are like the pushing forces in the earth that squeeze continents together. The middle is a mountain pushing up from the pressure.
4 Slice off the top at an angle
exposing the seashells or animals. This is what happens when rocks are worn away, or eroded, by wind and rain.
THINGS TO NOTICE: If you have a human figure, place it next to
the mountain and imagine you’re on a hike. If you come upon one of those seashells, what might you think?
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Glossary
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amber: hard, fossilized resin.
Resin is a sticky substance that oozes from trees. amphibian: a vertebrate animal, such as a frog or salamander, that needs sunlight to keep warm and shade to stay cool. It lays its eggs in water. archaeology: the study of ancient people through the objects they left behind. A scientist who studies archaeology is a archaeologist. arthropod: an invertebrate animal with a skeleton on the outside of its body. It has a segmented body and jointed legs. Insects and spiders are arthropods. atmosphere: the blanket of air surrounding the earth. atom: a small particle of matter. Atoms are the extremely tiny building blocks of everything.
background extinction:
the constant low-level rate of extinction. biology: the study of living things. camouflage: the colors or patterns that allow a plant or animal to blend in with its environment. carbon: an element found in living things, including plants. Carbon is also found in diamonds, charcoal, and graphite. carbonization: the conversion of organic matter into a carbon film. carnivore: an animal that eats meat. carnivorous: feeding on insects or other animals.
chloroplasts: tiny structures in fossil: the remains of any
the cell of a green plant where photosynthesis takes place. climate: the average weather patterns in an area over a long period of time. climate change: changes to the average weather patterns in an area during a long period of time. cold-blooded: animals such as snakes that have a body temperature that varies with the surrounding temperature. correlate: to relate rocks and fossils from one area with another area. Correlation is often used to determine the age of rocks and fossils. cyanobacteria: microbes that are blue-green in color and use photosynthesis. decay: to rot. dromaeosaur: the name for dinosaur raptors. Raptors were small- to medium-sized meateaters that walked on two legs with long, grasping fingers and a huge claw on each foot. ecosystem: a community of organisms that interact with each other and their environment. environment: everything in nature, living and nonliving, including plants, animals, soil, rocks, and water. erosion: the gradual wearing away of rock or soil by water and wind. evaporation: when a liquid heats up and changes to a gas. evolve: to change over time, sometimes into something more complex. extinction: the disappearance of a species from the earth.
organism, including animals and plants, that have been preserved in rock. genus: a group of organisms that consists of one or more species. geologic timescale: the way the 4.6-billion-year history of the earth is divided up. geology: the study of the earth and its rocks. A scientist who studies geology is a geologist. groundwater: water contained underground in the spaces in soil and sediment. herbivore: an animal that eats plants. herd: a large group of animals. igneous rock: rock that forms from cooling magma. Magma is melted rock below the surface of the earth. index fossil: a type of fossil that is used to identify geologic periods. It correlates rocks from one area with another. invertebrate: an animal without a backbone. law of superposition: the scientific law that sedimentary layers are deposited with the oldest on the bottom and the youngest on top. living fossils: a living species that has changed little from long ago and doesn’t have close relatives still alive. mammal: a type of animal, such as a human, dog, or cat. Mammals are usually born live, feed milk to their young, and usually have hair or fur covering most of their skin.
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Glossary mass extinction: periods in the earth’s history when very large numbers of species die out in a short period of time. meteorite: a meteor that is not burned up by the earth’s atmosphere and hits the earth’s surface. microbe: another word for microorganism. microorganism: an organism that is so small it can only be seen with a microscope. Middle Ages: the name for a period of time from around the year 350 to 1450. minerals: solids that are found in rocks and in the ground. Rocks are made of minerals. Gold and diamonds are precious minerals. numerical age: the age of a rock or fossil, usually in millions of years. nutrients: substances in food and soil that living things need to live and grow. organic: something that is or was living, such as animals, wood, grass, and insects. organism: any living thing. ornithischians: dinosaurs that had a hip structure like birds, where the pubic bone points down and backward. All plant-eaters that are not sauropods are ornithischians. paleontology: the study of the fossils of plants and animals. A scientist who studies paleontology is a paleontologist. peat: a brown, soil-like material that contains partially decayed plant matter.
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petrified wood: a fossil
of wood that has been turned to stone. petrify: to change into stone. photosynthesis: the process by which green plants and some microorganisms use sunlight, water, and carbon dioxide to make sugars that they use for food. plankton: microscopic organisms drifting in bodies of water. predator: an animal that hunts other animals for food. prey: an animal hunted by a predator for food. primates: mammals that have large brains, nails on the hands and feet, and a short snout. Apes, monkeys, chimpanzees, and humans are primates. pterosaur: an extinct flying reptile with featherless wings of the Mesozoic Period. radioactive decay: the breakdown of an atom into another kind of atom. radiocarbon dating: a type of radiometric dating that applies to material that was once living. It can only be used for materials that are about 40,000 years old or younger. radiometric dating: a method to determine the numerical age of a rock or fossil. It uses known rates of radioactive decay. relative age: the age of a rock or fossil relative to other rocks or fossils. reptile: an animal usually covered with scales that lays eggs in dry places. Reptiles include snakes, lizards, turtles, and now-extinct dinosaurs.
saurischians: dinosaurs that had a hip structure like lizards, where the pubic bone points forward. All theropods and sauropods are saurischians. sauropods: a group of plant-eating dinosaurs that walked on four legs and had a long neck and tail. sedimentary rocks: rocks formed from sediments or the remains of plants or animals. Sedimentary rock can also form from the evaporation of seawater. sediments: small particles of rocks or minerals, such as clay, sand, or pebbles. species: a group of living things that are closely related and can produce young. stromatolite: a rocky mass made of sediments trapped by mats of bacteria. theory of evolution: a scientific theory that explains how species change over time. theropods: a group of dinosaurs that walked on two hind legs and included all meat-eaters. toxic: something that is poisonous. trackway: a pathway of continuous dinosaur footprints. tsunami: a long, high sea wave caused by an earthquake or other disturbance. vertebrate: an animal with a backbone. warm-blooded: animals such as humans that don’t depend on the temperature around them to stay warm.
Children’s Activity/Education Resource
focus on science
Start an elementary classroom discussion about dinosaurs and you’ll suddenly have a room full of passionately engaged scholars. In Explore Fossils! With 25 Great Projects, readers can expand their dinosaur obsessions into learning opportunities that take them beyond Triceratops, Stegosaurus, and even Tyrannosaurus rex to other animals, plants, and microbes that lived long before humans.
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AGES: 7–10 GUIDED READING LEVEL: V
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Explore Fossils! introduces readers to the study of dinosaurs and the history of life on Earth as revealed by fossils. Through hands-on projects, vocabulary boxes, and high-interest content, children discover how fossils form and learn about the landscape and the plants and animals that lived long ago. Scientists use radiometric dating to test these fossils to discover when O GI S T TOL FIN N they were made, what organisms made them, what O D E those organisms used for energy, what killed them, and a whole lot of other information. All from rocks! That’s a lot of information stored under our feet. With Explore Fossils! children can dig in! In a
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“ Explore Fossils! provides young readers with “ This book by Cynthia Brown and her daughter go a remarkable introduction to paleontology. a long way toward providing reading material at It covers many topics not seen in similar the right level for a highly inquisitive youth. Clear books. The concise and up-to-date text, definitions of vocabulary words are well placed and the clear and instructive illustrations, progressive in building a sound background. The and the end-of-chapter projects make book does not shy away from concepts that are Explore Fossils! the best introduction to challenging but critical to the meaning of fossils.” —Markes Johnson, paleontologist, paleontology that I have ever seen.” —Spencer G. Lucas, PhD, New Professor Emeritus, Williams College Mexico Museum of Natural History and “ This is a fun book with great, thought-provoking ScienceMuseum of Paleontology projects. It offers a surprisingly sophisticated introduction to paleontology for the young and young at heart.” —Charles Marshall, Director, University of California