First, dinosaur fossils are found almost exclusively in sedimentary rocks, in other words, rocks that form when sand, silt, mud, and organic material settle out of water or air to form layers that are then compacted into rock. So in looking for dinosaur fossils, one must find outcrops of sedimentary rocks.
Second, no dinosaurs are known to have lived in the ocean, where most sedimentary rocks form. Instead, one must look in sedimentary rocks that were deposited on the continents, primarily by rivers and streams or in lakes into which the streams emptied. Occasionally, dinosaur fossils are also found in sedimentary rocks representing ancient, desert sand dunes and their associated habitats.
Third, the sedimentary rocks must have been formed or deposited during the Mesozoic Era, the geologic time period when nonavian dinosaurs lived. Finally, it's best to search in regions where little vegetation covers the surface of the ground, so that any fossil fragments weathering out of the sedimentary rock layers can be more easily seen. These regions of barren ridges and ravines are often called badlands.
In order to find appropriate, Mesozoic, sedimentary rock layers, paleontologists often use geologic maps, which document the kinds of rock layers of different geologic ages that are exposed on the surface. Once appropriate rock layers are found, the search for dinosaur fossils can begin with a reasonable hope of finding the kinds of dinosaurs one is searching for. But commonly, other kinds of fossils are serendipitously discovered during the search.
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.
To watch the videos, go to www.amnh.org/explore/amnh-tv. Click on the "Dinosaurs Explained" Tab on the left side of the page. In the playlist, start with the first question and play each video consecutively for a mini-course in dinosaur fossils.
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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