SP-40 Dinosaur Lake: The Story of the Purgatoire Valley Dinosaur Tracksite Area

Latest research on the largest dinosaur track site in North America located in remote area near La Junta, Colorado. Summarizes natural and social history of region; identifies trackmakers; discusses erosion and other problems on the site. 64 pages. 73 figures. SP-40

From the Introduction:

The Purgatoire Tracksite is associated with strata (layers of rock) known as the Morrison Formation. This geologic strata, dating from the Late Jurassic Epoch — about 150-million years ago — is one of the most famous dinosaur-bearing deposits in the world, containing well-known fossil sites such as Dinosaur National Monument. First discovered in 1877, near Morrison, Colorado, the formation quickly yielded some of the world’s best known dinosaurs (such as Stegosaurus and Apatosaurus — better known as “Brontosaurus”) in the form of partial or complete skeletons used to stock the world’s museums and introduce dinosaurs to a broad international audience.

The late 1800s were a period of intensive digging for dinosaurs remains. The activity of this time was dubbed the “Bone Wars” due to an intense rivalry that developed between Edward Cope and Othniel C. Marsh, two of North America’s most famous 19th century paleontologists. As a result of this “dinosaur bone rush,” little attention was paid to tracks until the 20th century. It was not until the 1930s that the Purgatoire site, and several other important dinosaur tracksites in the western United States were discovered. Even then, the potential and significance of the tracksites were not realized.

The perception of tracks as relatively insignificant fossil evidence began to change in the 198Os, in the wake of the so-called “dinosaur renaissance.” During this time dinosaurs acquired a new image as agile and intelligent creatures rather than plodding behemoths. Because tracks are made by live creatures, they provide dynamic evidence that sheds light on animal locomotion, speed, behavior, and ecology. The result of this reawakening of scientific interest was that previously known fossil footprint sites were reinvestigated and many new sites discovered.