What Is a Fossil?

Paleontology is the science of studying fossils from ancient organisms, and paleontologists are scientists who find and study those fossils.

Definitions of exactly what constitutes a fossil vary to some extent, but basically, fossils are naturally preserved physical traces of long-dead organisms. Usually, these traces consist of an organism's hard parts, such as bones, teeth, shells, or wood. Occasionally, when conditions are optimal, soft parts of organisms can also fossilize, such as impressions of skin, body outlines, and, more commonly, leaves. In almost all cases, fossils provide information about the original shape and structure of these physical traces; however, they usually do not provide any information about the original color of the body parts. Other traces of objects made by organisms, such as footprints, burrows, and nests, also qualify to be called fossils. Also, most definitions of fossils require that the organism's body part or other physical trace be more than 10,000 years old in order to truly be called a fossil.

However, objects made by prehistoric humans, such as pottery, arrowheads and buildings, are not considered to be fossils, but instead are referred to as anthropological artifacts.

This video is part of a series, "Dinosaurs Explained," produced by the American Museum of Natural History. In the series, Museum paleontologists answer the most frequently asked questions about dinosaurs.

Episode 1: What Is and Is Not a Dinosaur?

Episode 2: Who Discovered the First Dinosaur Fossils?

Episode 3: How Do Dinosaurs Get Their Names?

Episode 4: Are Any Dinosaurs Still Alive Today?

Episode 5: How Many Kinds of Dinosaurs Are There?

Episode 6: Where in the World Did Dinosaurs Live?

Episode 7: What Is the Earliest-Known Dinosaur?

Episode 8: What Were the Biggest and Smallest Dinosaurs?

Episode 9: What Did Dinosaurs Eat?

Episode 10: How Fast Were Dinosaurs?

Episode 11: How Intelligent were Dinosaurs?

Episode 12: Did Dinosaurs Fight?

Episode 13: How Did Dinosaurs Reproduce?

Episode 14: Did Dinosaurs Travel in Herds or Packs?

Episode 15: What Was Dinosaur Skin Like?

Episode 16: How Fast Did Dinosaurs Grow, and How Long Did They Live?

Episode 17: What Color Were Extinct Dinosaurs?

Episode 18: Were Dinosaurs Warm-Blooded?

Episode 19: How Did All Dinosaurs Except Birds Go Extinct?

Episode 20: Can We Clone Extinct Dinosaurs From DNA Preserved in Their Fossils?

Episode 21: What Is a Fossil?

Episode 22: How Do We Know Where to Look for Dinosaur Fossils?

Episode 23: How Are Dinosaur Fossils Discovered and Collected?

Episode 24: How Are Dinosaur Fossils Prepared in the Laboratory?

Episode 25: How are skeletal mounts of dinosaurs in museum exhibits built?

Episode 26: Where are all the dinosaur fossils kept once they're prepared?

Episode 27: How Do We Know Which Kind of Dinosaurs Were Most Closely Related?

Episode 28: How do we know how long ago dinosaurs lived?

Episode 29: In what kind of environments did dinosaurs live?

Episode 30: How does studying dinosaurs benefit humanity?

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