15 Invertebrate Fossils-Mid

Invertebrate Fossils FOCUS Question What can we learn by studying the fossils of invertebrates?

Ancient Treasure In the 1880s, people in Canada were working on a new railroad. It would stretch across the entire country. They even had to build tracks over the massive Rocky Mountains. The railroad company sent a geologist named Richard McConnell to find a route through the mountains. Once there, he noticed strange shapes in the rocks. He had found thousands of fossils! They turned out to be some of the oldest animal fossils ever found. The rocks in this area became known as the Burgess Shale. By studying the fossils there, scientists have learned a lot about what Earth was like hundreds of millions of years ago.

Finding Invertebrate Fossils Fossils are traces of living things from long ago. When you think of fossils, you might think of dinosaur or fish bones. The Burgess Shale fossils are all invertebrates—animals without backbones. All fossils give us clues about the habitat where the plant or animal lived when it was alive. Imagine finding a coral fossil. A living coral's habitat is a warm ocean. So, the area where you found the fossil must have been under warm water long ago. Fossils of invertebrates are some of the best fossils for studying Earth's past. Science in Your World 1. Most body fossils came from bones, shells, teeth, and other hard materials. They are the most common. 2. Trace fossils came from tracks, nests burrows or other things plants and animals leave behind. They are less common. 3. Soft body fossils came from soft body parts such as flesh. They are very rare.

Why are invertebrate fossils helpful for looking at the past? Invertebrates are the most numerous animals on Earth. They include insects, worms, snails, and countless other animals. They also lived hundreds of millions of years before dinosaurs. The bones of big animals can get scattered over a wider area. Invertebrates are often small. Their fossils are more likely to be found whole. Also, soft bodies usually rot before they can become fossils. Many invertebrates have hard shells. Shells become fossils easily. For these reasons, invertebrates are the most common animal fossils. The easier it is to find a fossil the easier it is to study.

Invertebrate History The First Life Earth formed about 4.5 billion years ago. The first living things appeared about 3.8 billion years ago. They were simple cells like bacteria. These simple cells were the only life on Earth for millions of years! Then, about 540 million years ago, cells began to come together. They formed more complex living things. These were the first animals. In a short time, thousands of new species appeared. They quickly spread across the planet. This sudden development is called the Cambrian Explosion.

In the Sea Many kinds of invertebrates appeared during the Cambrian Explosion. They included animals that look like today's sea stars, snails, shrimp, and squid. The Burgess Shale is from this time. Scientists think a landslide along the coast buried many small aquatic invertebrates, which then became fossils. The Burgess Shale even has soft body fossils from animals such as worms. All these animals lived in warm, shallow seas. The floors were soft and mucky. That means that the place where the tall, snowy Canadian Rockies are today was once covered with warm salt water!