Earth & Sky

Our thanks to the following individuals and institutions who assisted in the preparation of this script:

Martin Lockley
University of Colorado
Denver, CO

David Wolf
U.S. Forest Service

Terry Johnson
U.S. Forest Service

The following books, articles and web sites were used in preparing this script:

Dinosaur Tracks and Other Fossil Footprints of the Western United States, Martin Lockley and Adrian P. Hunt, Columbia University Press, 1995.

Tracking Dinosaurs: A New Look at an Ancient World, Martin Lockley, Cambridge University Press, 1991.

Dinosaur Trackers Research Group – University of Colorado Denver

Friends of Dinosaur Ridge Tracksite

Triassic-Jurassic Footprint Project (Columbia University)

Dinosaur State Park, Connecticut (not all U.S. dino tracks are west of the Mississippi)

Author notes:

Dinosaur tracking is a branch of ichnology, the study of trace fossils. Other ichnologists look at things like fossilized worm burrows and termite mounds, coprolites (fossilized body waste), gizzard stones, eggs, and nests.

Dinosaur trackers usually use rather traditional techniques to gather data on the tracks they locate. They use measuring tapes to size up individual tracks, pencil and notebook to record numbers and make drawings, and latex rubber and plaster to make three-dimensional casts. These techniques, which work well, are the old reliable tools in the dino tracker’s tool kit.

Dino trackers have experimented with new tools for their tool kit. In 1996, for example, dino tracker Dr. Martin Lockley of the University of Colorado – Denver, teamed up with stereo photography experts David Wolf and Terry Johnson of the U.S. Forest Service to make three-dimensional photos of tracks in Comanche National Grassland.

Johnson and Wolf set up a camera above an individual track, pointed down. They snapped a photograph of the track, then moved the camera slightly and snapped another photo of the same track. Offsetting the camera re-created the three-dimensional effect we see with our two offset eyes. Placing each pair of photos in a special viewer showed them as a single three-dimensional image.

This is an old technique. In the late 19th century, for example, “stereopticon” viewers were all the rage. In this century, the technique has been used to project 3-D movies. Planetary scientists use stereo photography to explore other worlds. Sometimes they find that the play of light and shadow on alien landscapes can be misleading. For example, features that look like mountains in individual photographs are revealed to be deep pits in stereo.

Wolf and Johnson took the stereo images of dinosaur tracks one step further. Johnson used computer software to digitize the track images. That is, he reduced them to numerical data points precisely recording the depth, height, and width of the individual tracks. When combined, the data points yielded a precise contour map of each individual track.

Again, this is not a new technique. Stereo images have been used to make contour maps of landscapes and archaeological sites for many years. This was, however, the first time it was applied to dinosaur tracks.

Martin Lockley cautions that this technique is no substitute for on-site inspection by a trained dino-tracking scientist. He prefers to work with the old tools, and would take a plaster cast of a track on his desk over a digital map on his computer monitor any time. But he admits that the new technique has its uses.

For example, very large tracks are hard to cast using plaster. It’s difficult to transport a heavy plaster cast back to the lab. The new technique reduces a large track to a computer file that can be carried in one’s pocket on a CD or even emailed over the Internet. Also, the new technique can be applied to entire trackways, which in some rare cases extend for thousands of meters. For trackways, the camera can be mounted on an airplane, which can then fly over the track site. This is potentially more accurate – not to mention, much easier – than the old technique of recording large trackways using a tape measure and notebook.

Dave Wolf points out that the new technique could also yield casts of tracks. Stereolithography, a technique widely used to create solid models of computer designs, could generate plastic casts using the digital data. The resulting cast would resemble a plaster cast, and could be studied in the same way.

If recorded on CD, track data could be preserved indefinitely. A cast could be generated using stereolithography long after a plaster cast would have crumbled. In fact, a CD could serve as a “dinosaur track preserve” long after natural erosion destroyed the original dinosaur track or trackway.