Information on Dinosaur Fossils

Geological Processes

• Dinosaur fossils are not found in just any kind of rock. They are found in sedimentary rock which is characterized by many different strata, or layers, that are laid down over time. Long ago, layers of sedimentary rock trapped dinosaur bodies in the process of decay. The softer parts of the dinosaurs continued to decay, but harder parts were preserved in rock layers, and often their substances were replaced by minerals. Traces of dinosaurs, such as footprints, were also preserved. Today these fossil-filled layers rise to the surface of the earth due to geological movement and due to erosion. When dinosaur fossils come closer to the surface, they may be discovered.

Types of Fossil Finds

• There are three types of condition in which dinosaur fossils may be discovered. An "associated skeleton" is a variety of bones from the same dinosaur. The bones are loosely joined together, but some may be broken or absent. An "isolated bone" is a single dinosaur bone without other bones nearby. An "articulated skeleton" is the most useful type of fossil because it contains all of the bones in their connected order.

Excavation Process

• The process of excavating a dinosaur fossil is challenging. The "overburden" or rock that encases any part of the fossil has to be taken off. Then paleontologists must document the site of the discovery. Since fossils that hit the air can begin to decay, especially fragile bones have to be preserved with chemicals. The remaining bones are covered in plaster jackets and removed from the site.

History

• Dr. Caspar Wistar discovered the first dinosaur fossil in 1787 in New Jersey. Later, in the early 19th century, the fossils of dinosaur footprints were found in New England stone pits. Since these fossils were not valued in the same way that they are today, they were destroyed. It was not until 1824 that William Buckland gave a scientific account of a Megalosaurus fossil. While Buckland's account was complete, the fossil that he was working with was incomplete. The first articulated or complete dinosaur skeleton was not found until 1838 by William Parker Foulke.

Museum Display

• Museums offer displays of fossil discoveries. While actual fossils were displayed originally, today casts are displayed to the public. The American Museum of Natural History in New York City and the Academy of Natural Sciences in Philadelphia, Pennsylvania, are just two examples of the many museums that contain dinosaur fossil collections.