Worland Field Office







Can you guess which dinosaur most resembles the dinosaur which walked on the Red Gulch Dinosaur Tracksite?

What is a Tracksite? A tracksite is an area where footprints and other trace fossils are preserved. Tracksites may cover only a few square yards or they may extend for miles. They tell stories about extinct animals that can't be read from body fossils such as teeth and bones.

Tracks, trackways, and tracksites - what are they? A track is a single footprint. A trackway is a row of two or more tracks made by a single animal walking across a surface. A Tracksite is an area where many tracks or trackways are preserved.

Why are the tracks important? Scientists are excited about this site for several reasons. First, this is the largest tracksite in Wyoming, and one of only a few worldwide from the Middle Jurassic Period (160 million to 180 million years old). For part of the Middle Jurassic, Wyoming was covered periodically the the Sundance Sea. Until the tracks were found, it seemed that only sea-dwelling creatures could have lived in the area, and there shouldn't be any footprints here at all!

But there's more to the mystery. What kinds of animals were making these tracks? Middle Jurassic dinosaur skeletons are extremely rare in North America, and there are only a few areas with similar tracks. With few fossils for comparison, the identity of the Red Gulch track-makers have not been identified. Scientists think that the footprints were made by small to medium sized bipedal dinosaurs (walked on their hind legs).

The site is interesting because it is so extensive and unusual in its age and geographic occurrence. Its location makes it easily accessible for scientific research. Even the geologic history of the area, once thought to be well understood, needs to be rewritten because of the tracks' discovery.

When was the Red Gulch Dinosaur Tracksite found? The Tracksite was reported during the summer of 1997.

How old is it? The Tracksite is approximately 167 million years old. The rock layer that preserves the Tracksite was horizontal when the tracks were made. All sediments, such as sandstone, clay, limestone, or silt, are deposited as horizontal layers. Faulting and uplift may later bend, break, and tilt these layers.

Why is the rock layer tilted? The rock layer that preserves the Tracksite was horizontal when the tracks were made. All sediments, such as sandstone, clay, limestone, or silt, are deposited as horizontal layers. Faulting and uplift may later bend, break, and tilt these layers.

What kind of rock is this? The rock is limestone.

What did it look like when dinosaurs were walking here? The dinosaurs were walking across a flat, ripple-marked coastline much like those found in the Bahamas today.

What was the environment like then? Could dinosaurs live in Wyoming's winters? The environment was probably much warmer than present day Wyoming because North America was much farther south 167 million years ago. It was about as close to the equator as Florida is today.

How big were the dinosaurs? The hip-height of some dinosaurs can be estimated by multiplying the length of the footprint by 4 or 5. We think the theropods walked with the body leaning forward from the hips, and the heavy tail extended almost straight backward.

Were the dinosaurs running? Most of the dinosaurs appear to have been walking, not running.

How do we know that? The speed of a small dinosaur can be estimated by comparing its hip-height to its stride length (the distance between two consecutive footprints made by the same foot.) If the stride length is more than three times the hip-height the animal was probably running.


Girls from an elementary school.

Showing the size of the footprint.

A dinosaur footprint at the tracksite.

How old are some other fossils found in this area? The Allosaurus "Big Al" found north of Shell, Wyo. in 1991, is about 15 million years younger than the Tracksite. The plant fossils at Big Cedar Ridge, near Ten Sleep, Wyo. are about half as old as the Tracksite.

What are the oval shaped holes in the Tracksite surface? The oval shaped holes in the Tracksite may have been made by ancient shrimp, clams, or lugworms. One kind made vertical burrows and another made horizontal holes. Understanding this will help reconstruct the environment around the time the tracks were made.

How do scientists investigate the site? Science is a process that follows a few simple rules. Seen as a whole, science may look complicated and difficult, but the individual steps in the scientific method are very clear. Taken one at a time, in sequence, the steps can lead to an objective and defensible conclusion. The first step is observation.

Observation: Scientists who study the earth must learn from observation. Earth history can't be duplicated in an experiment, so geologists and paleontologists must look closely at rocks and fossils to gather information about them. The present is the key to the past. Geologists learn from studying modern systems, the way ancient systems worked.

Analysis: Information from observations is analyzed to learn whether it is meaningful to the study. Irrelevant information may be put aside. Analysis also shows if more information, or a different kind of information, must be gathered before going further.

Hypothesis: Scientists rely on their education and training to form ideas about what their observations have revealed. An idea that might explain their observations is called a hypothesis. Often more than one hypothesis is proposed, because there might be several possible explanations.

Testing: A hypothesis isn't an answer. Each must be tested to see if it explains what was observed. A hypothesis that doesn't provide a complete, objective explanation is rejected, and another must be chosen and tested.

Conclusion: The hypothesis that offers the best explanation of all the information observed and analyzed can become a conclusion. Often an early hypothesis must be modified to fully explain all the observations.

Science is an endless process. Conclusions reached in one study are not necessarily "the truth." They're just the best answer we can reach with the information at hand, and are often the basis for another study.