# Fossil - Source: Kiddle (kids.kiddle.co), CC BY-SA 3.0, Kiddle encyclopedia, adapted from Wikipedia - Reading level: Grade 5 - Subjects: Dinosaurs, Science, History - Topics: fossils, called, ancient, living, rock, fossil - Length: 809 words, about 6 min - Published: 2025-10-17 - Original: - Page: - Open in Sprouts: ![Amonite Cropped](https://sprout.rootsofreason.org/media/kiddle-fossil-facts-for-kids-24f841da68.jpg) Three small ammonite fossils, each approximately 1.5 cm across. ![Trilobite2](https://sprout.rootsofreason.org/media/kiddle-fossil-facts-for-kids-0eef0d7a9a.jpg) A fossil of a trilobite which lived about 444 million years ago. ![Stromatolites Cochabamba](https://sprout.rootsofreason.org/media/kiddle-fossil-facts-for-kids-c5df0ffed3.jpg) Lower Proterozoic stromatolites from Bolivia, South America. These were produced by cyanobacteria. Polished vertical slice through rock. ![Insects in baltic amber](https://sprout.rootsofreason.org/media/kiddle-fossil-facts-for-kids-7240c680ef.jpg) A mosquito and a fly trapped in amber ![Cretaceous Orthoptera fossil](https://sprout.rootsofreason.org/media/kiddle-fossil-facts-for-kids-70b9efe8a2.jpg) Fossil locust from the earliest Upper Cretaceous, ~95 million years ago, Santana Formation, Brazil. A **fossil** is the remains or a sign of an ancient living thing. Fossils tell us about life from millions of years ago. You can find fossils of animals, plants, or tiny protists. They are usually found in sedimentary rock. This type of rock forms from layers of sand, mud, and other materials that build up over time. Most fossils keep the shape of the original living thing. However, the original parts of the body are replaced by hard, inorganic materials. These materials can be things like calcium carbonate (which is in shells) or silica (which is in sand). So, a fossil feels and is made of rock. It has been "turned into rock," a process called *petrification* or *mineralization*. Sometimes, a fossil is not the actual body. It can be an *imprint* or *impression* left in ancient mud. This mud later turned into rock. Some organisms turn into fossils easily, while others do not. The most common fossils come from creatures with hard parts. For example, the hard, calcitic shells of molluscs (like clams and snails) and brachiopods are very common. These sea creatures have created many fossil-rich layers of limestone in the Earth. Soft-bodied organisms can also become fossils, but only in very special conditions. The Ediacaran biota are a good example of soft-bodied fossils. The most famous fossils are often those of giant, prehistoric [dinosaurs](https://sprout.rootsofreason.org/r/kiddle/dinosaur-facts-for-kids). You can see their fossilized bones and tracks in many museums. The study of fossils is called paleontology. Geologists and biologists are the scientists who study them. If they study how ancient living things fit into their environment, it is called paleobiology. ## Where Are Special Fossils Found? There are some places where fossils are found with amazing details. Or, they might be found in very large numbers. Scientists call these special sites *Lagerstätten*. This is a German word. One famous example is the La Brea tar pits in Los Angeles. Another is the Solnhofen limestone quarries in Bavaria, Germany. These places give us a lot of information about ancient life. ## Different Kinds of Fossils Fossils can be different sizes and types. ### Microfossils and Macrofossils - *Microscopic* or very tiny fossils are called "microfossils." You need a microscope to see them. - Larger, *macroscopic* fossils are called "macrofossils." These are things you can see with your eyes, like seashells or mammal bones. ### Pseudofossils Some stones look like fossilized organisms but are not fossils at all. These are called "pseudofossils." They are natural rock formations that just happen to look like living things. ### Trace Fossils and Other Signs Even without the actual body, there can be *indirect* signs of prehistoric life. These are called *trace fossils*. - Examples include a worm's trail or an animal's footprint. These are quite common. - Fossilized excrement (poop) is known as a *coprolite*. - Chemical traces of ancient organisms are called *chemofossils*. - Objects made by prehistoric people are called artifacts. These are not fossils, but they also tell us about the past. Sometimes, even soft-bodied animals can leave permanent impressions or carbon traces. This happens in special cases, giving us fossils of small, soft creatures. ### Other Ways Fossils Form Fossils can also form in other ways, not just by turning into rock. - Sometimes, dryness (desiccation), freezing, or pine resin can preserve living things. - Examples include mummified animals, ice-covered wooly mammoths, and insects trapped in amber. ### Living Fossils *Living fossils* are not fossils in the traditional sense. They are modern-day organisms that look very similar to their ancient ancestors from millions of years ago. They have changed very little over time. Good examples are the ginkgo [tree](https://sprout.rootsofreason.org/r/kiddle/trees), the coelacanth fish, and the horseshoe crab. ## How Were Fossils First Understood? Many people in ancient times noticed fossils. But not everyone understood that they were the remains of living things. One of the first to write about his ideas was the Ancient Greek philosopher Xenophanes (around 570–470 BC). Other writers reported his thoughts: He noticed that shells were found on land and mountains. He saw impressions of fish and seaweed in quarries. He thought these were formed when everything was covered in mud long ago, and the impressions dried in the mud. These ideas were rediscovered in Europe in the 1600s. Scientists like Nicolas Steno in the Netherlands and Robert Hooke in London wrote and lectured about fossils. In the 1700s, people started collecting fossils, and serious thinking about geology began. By the 1800s, geology became a modern science. Fossils played a big part in understanding the theory of evolution. ## Picture credits - Richard Wheeler, CC BY-SA 3.0 () - Kiddle encyclopedia, adapted from Wikipedia, not established () - Didier Descouens, CC BY-SA 4.0 () - Brocken Inaglory, CC BY-SA 3.0 () - Woudloper, Public domain ()