wot24

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?
http://youtu.be/Me8BrHY57JI

Episode 2: Who Discovered the First Dinosaur Fossils?
http://youtu.be/FbPGrB-BmH0

Episode 3: How Do Dinosaurs Get Their Names?
http://youtu.be/Wrdmw_Ioovk

Episode 4: Are Any Dinosaurs Still Alive Today?
http://youtu.be/947j2zXm8WA

Episode 5: How Many Kinds of Dinosaurs Are There?
http://youtu.be/xdGe2tMdjxs

Episode 6: Where in the World Did Dinosaurs Live?
http://youtu.be/0lGXGz_lALM

Episode 7: What Is the Earliest-Known Dinosaur?
http://youtu.be/62LK_Ny905o

Episode 8: What Were the Biggest and Smallest Dinosaurs?
http://youtu.be/Icp9eIVMBwU

Episode 9: What Did Dinosaurs Eat?
http://youtu.be/dYrNWPyLtlI

Episode 10: How Fast Were Dinosaurs?
http://youtu.be/GKsygFxt4XI

Episode 11: How Intelligent were Dinosaurs?
http://youtu.be/pXFHtwVQxqk

Episode 12: Did Dinosaurs Fight?
http://youtu.be/hiqlCBH-5C0

Episode 13: How Did Dinosaurs Reproduce?
http://youtu.be/Kp4Dg8XBeUA

Episode 14: Did Dinosaurs Travel in Herds or Packs?
http://youtu.be/jtbpusl0Vo0

Episode 15: What Was Dinosaur Skin Like?
http://youtu.be/6i3EmBNYptk

Episode 16: How Fast Did Dinosaurs Grow, and How Long Did They Live?
http://youtu.be/KyUptMWcmZI

Episode 17: What Color Were Extinct Dinosaurs?
http://youtu.be/bN7XTFlxPTI

Episode 18: Were Dinosaurs Warm-Blooded?
http://youtu.be/oy8Kvt1vOto

Episode 19: How Did All Dinosaurs Except Birds Go Extinct?
http://youtu.be/mCKeogDioWE

Episode 20: Can We Clone Extinct Dinosaurs From DNA Preserved in Their Fossils?
http://youtu.be/H1E_Nwj2dro

Episode 21: What Is a Fossil?
http://youtu.be/WWHJqnfmhQ8

Episode 22: How Do We Know Where to Look for Dinosaur Fossils?
http://youtu.be/XQRZqG7wCPQ

Episode 23: How Are Dinosaur Fossils Discovered and Collected?
http://youtu.be/rYjs8Wtfnzo

Episode 24: How Are Dinosaur Fossils Prepared in the Laboratory?
http://youtu.be/6brUGBR6ll0

Episode 25: How are skeletal mounts of dinosaurs in museum exhibits built?
http://youtu.be/FZNq4SgUqgE

Episode 26: Where are all the dinosaur fossils kept once they're prepared?
http://youtu.be/r8ENj3lTTWk

Episode 27: How Do We Know Which Kind of Dinosaurs Were Most Closely Related?
http://youtu.be/3gNw_6DoVc8

Episode 28: How do we know how long ago dinosaurs lived?
http://youtu.be/6pYPqtdTnrM

Episode 29: In what kind of environments did dinosaurs live?
http://youtu.be/62Z-iSwh3i4

Episode 30: How does studying dinosaurs benefit humanity?
http://youtu.be/vGzVaprEbqs

***
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To find fossils, paleontologists conduct short field trips and longer expeditions to regions around the world where fossils are likely to be found. To be successful, this fieldwork requires considerable funding and careful planning. Each trip is designed to try and find fossils that will shed new light on particular research questions. Commonly, fossils have already been found in the region where the fieldwork is conducted, but if not, geologic maps and satellite photos are used to identify areas where rocks of the right age and ancient environment are exposed on the surface.

To find fossils, paleontologists first carry out an operation called prospecting, which involves slowly hiking across ridges and through ravines, while keeping one's eyes focused on the ground in hopes of finding fragments of fossils weathering out on the surface. Commonly, one covers 5-10 miles in a day of prospecting. Once a fossil fragment is found, the collector brushes away the loose dirt on the surface to see if more of the specimen is buried in the ground. If so, quarrying is initiated to collect the fossil. First, awls, rock hammers, chisels, and other tools are used to remove the rock covering the bones to see how much of the skeleton is present. As bone is exposed, special glue is applied to the cracks and fractures to hold the fossil together.

Next, a trench is dug around the bones so that they essentially sit on a low pedestal. A covering of damp toilet paper is placed over the bones before a layer of plaster bandages is wrapped around the bones to create a hard cast, just like a doctor does around a broken bone. Once the cast hardens, excavating the bone is completed, and the fossil in its cast is packed for shipment back to the museum.