LIVING FOSSILS: Clues to the Past
Most living things differ greatly from their early ancestors. But not living fossils. A living fossil is a modern-day plant or animal that closely resembles its ancient relatives.
Coelacanths, horseshoe crabs, dragonflies, tuataras, nautiluses and the hula painted frog are living fossils. Living fossils are a mystery. Why did they change so little when the world around them changed so much?
Take a trip into the past and visit these amazing animals to see how they lived then. And have a look at how their descendants live now. How did these living fossils survive?
Time Line: Make a time line of the history of the earth and show when the animals described in this book lived. (Use a roll of shelf paper or draw the time line with chalk on the playground. If one inch equals a million years you will need about 20 feet to go back to the beginning of dinosaurs and more to go back to the beginning of life on Earth.)
Make an Animal Classification Chart: Make sections for fish, amphibians, reptiles, birds, mammals, invertebrates. List animals that are described in this book in the appropriate category. (Note: invertebrates are animals that have no backbone.)
Peanut Butter and Jelly Geology: The age of a fossil can be determined in part by where it was found. Earth's crust is made of many layers of rock and dirt. They build up over millions of years. In some places, where a hill has been cut along the side of a road, you can see some of the layers. The Grand Canyon is another place to see how the Earth was formed. Each layer represents a period of time.
You can make an "Earth Sandwich" to learn about the layers of the Earth. Each part represents a part of the Earth's crust. When you cut the sandwich in half, it will be like digging through the layers of the Earth. To make your sandwich, you will need: pumpernickel bread for coal, rye bread for sandstone, white bread for limestone, peanut butter for dirt, jelly for oil or tar, raisins for boulders, and pretzel sticks for fossil bones
Make Your Own Fossil: You can make a mold of a living object. It will be similar to a real fossil. You will need: a small paper or plastic cup; wet sand; a small object such as a shell, nut or leaf; plaster of Paris (you can get this at a hardward store or hobby shop; water, spoon, bottom half of a milk carton; newspaper. Spread out the newspaper to catch anything that might spill. Put wet sand into the cup until it is about half full. Pat the sand firmly into place. Carefully press your object into the surface of the sand. Lift it out. You should be able to see the shape of your object in the sand. Put about a cup of dry plaster of Paris in the milk carton. Add water and stir until the mixture is about the thickness of heavy cream. (Add a little water at a time until you have enough.) Make sure that there are no lumps in your plaster of Paris mixture. Then pour the plaster of Paris mixture into the cup. Leave it for an hour or so to harden. When it is hard, peel away the paper cup and throw away the sand. You will see the shape of your object in the plaster. You made your fossil in a few hours. In the Earth, it takes thousands of years for fossils to form.
When you think of fossils, you might think of dinosaur bones or trilobites...something preserved in rock. Something prehistoric. Extinct. But what if some of those ancient creatures still lived among us? Would we recognize them?
Caroline Arnold shows us six amazing creatures that closely resemble their ancient relatives–"living fossils". Comparing "then" to "now" she shows where these creatures live, how they survived, and what their future looks like. Take, for example, horseshoe crabs. One hundred fifty million years ago, horseshoe crabs had hard shells and long tails. They crawled up on sandy beaches to search for worms and shellfish to eat. Not much has changed. If you visit the east coast on a warm summer night when the moon shines full, you're likely to see hundreds of horseshoe crabs pull themselves up onto the beach. They're digging nests and laying eggs, just like they did millions of years ago.
You don't need to travel to the beach to find living fossils; just head to a wetland or hayfield on a warm day and look for dragonflies. Those keen mosquito-devouring hunters are the great-great-great-.....great-grandchildren of dragonflies that lived 280 million years ago. Over the years things changed, like size. Back then dragonflies were larger–the size of a crow.Sue Smith-Heavenrich
Many of us have seen fossils in museums; the trilobites and other insect-like creatures, and the dinosaurs, both small and large. For the most part these animals looking nothing like any animal that is alive today. They went extinct long ago and their very distant modern-day relatives are quite different.
However, there are a few animal species living in the present day that are very similar to their ancient relatives. Their kind survived extinction events and climate change, and they have even survived the assent of mammals. These animals are often called living fossils, and in this book readers will meet a few of these singular creatures.
Perhaps one of the most famous living fossils is the coelacanth. Before the 1930’s scientists thought that this large, marine, lobed-tailed fish had died out sixty-five million years ago. Then a fisherman found a coelacanth in the Indian Ocean and the scientific community went wild speculating about how this animal had survived for so long.
Another species that has remained remarkably unchanged is the horseshoe crab. This animal lived on Earth a hundred million years ago, and it still lives here in the present day.
Many of us will probably never see a live coelacanth or horseshoe crab, but there is one living fossil that most of us are familiar with because they are found all around the world. Two hundred and eighty million years ago large crow-sized dragonflies zipped around marshes preying on smaller insects and other animals. Dragonflies today are a lot smaller, but they still favor environments where there is water, and they are still predators.
Young readers who are interested in fossils and in creatures that lived long ago are going to thoroughly enjoy this book. Readers are shown what six ancient animal species looked like and then they are shown their modern-day counterparts. In addition to telling us about these animals, the text also explains how fossils are formed and how living fossils provide scientists with “clues to the past.” (Marya Jansen-Guber)