What are dinosaur trackways?

Dinosaur trackways are fossil footprints of dinosaurs, which are found all over the world. These trackways developed as dinosaurs (and other animals) walked in the soft sediment or sand along the shorelines of beaches, rivers, ponds, and lakes. Almost immediately after the animals walked by, the tracks were quickly buried in sediment, eventually becoming fossil footprints (also called ichnotaxia). Because such places were good sources of water and food, including lush plants for the herbivores, and plenty of animals for the carnivores, they became natural pathways for all types of dinosaurs. (In fact, the branch of science concerned with the study of footprints is called ichnology.)

So far, the problem with dinosaur trackways is that it is impossible to tell what dinosaur made the footprints. Scientists can only give general an idea of the animals, such as if the tracks belonged to a biped or quadruped dinosaur, and often a sauropod versus a theropod. But that is usually all they can tell from a footprint.

Where was one of the first dinosaur footprints found in the United States?

The first fossilized dinosaur footprint found in the United States is attributed to Pliny Moody in 1800 in Massachusetts. The 1-foot (0.3-meter) print was uncovered at Plinys farm and it was initially thought to be from Noahs Raven, as per the Noah and the ark story in the Bible. Other dinosaur footprints were also found in various New England quarries in the early 1800s, but they were thought to be unimportant. The majority of the tracks were consequently blown to bits in the quarrying process.

What conditions might lead to the best footprints?

Recent experiments show that the best footprints arent made in fresh, new mud. Instead, the presence of a coating on top of older mud leads to the best tracks.

Fresh mud tends to be sticky and flows readily. Footprints made in this type of mud are poorly preserved and leave few little details. Fresh, sticky mud adheres to the feet, leaving at best a partial impression in the ground; as the foot is lifted, some of the surrounding mud flows into the footprint. Footprints made in this type of mud seem to be typical of most of the known dinosaur tracks, which is why they are so hard to associate with particular species.

Linder the right conditions, even the footprints of dinosaurs may be preserved for eons. Such finds can tell paleontologists a great deal about the anatomy and behavior of dinosaurs (iStock).

On the other hand, older coated mud seems to be a much better medium for making and preserving finely detailed footprints. This type of mud is commonly found around ponds and is sometimes covered with a greenish coating of algae and bacteria. Experiments have shown that the coating acts as a binding agent. It keeps the muddy surface together and prevents flow into the footprint after the foot is lifted. It also acts as a parting agent, preventing the mud from sticking to the feet and resulting in deep prints with fine details. A third benefit to the coating is that it slows down the drying of the mud, allowing the prints to be formed.

Tracks made in this coated mud can be deep, very clear, and well-preserved, with plenty of anatomical detail. The most well-known dinosaur footprints were probably made under these conditions.

What are some of the largest dinosaur trackways in North America?

Some of the largest dinosaur trackways are called megatrack sites, where footprintbearing rock can extend for hundreds or even thousands of miles. Several Jurassic and Cretaceous periods sites in North America have such trackways. For example, tracks in the Entrada sandstone beds in eastern Utah (Middle Jurassic) cover about 116 square miles (300 square kilometers); the density of the prints is estimated to be between 1 and 10 per 10.8 square feet (1 square meter). Another is a 150-million-year-old dinosaur trackway in the Purgatoire River Valley, Colorado. The area was once home to a large freshwater lake, allowing dinosaurs to walk through the mud along the edge, and leaving behind vast trails of footprints. Today, over 1,300 of these now-solidified-in-rock footprints are exposed at the Picketwire Canyon- lands dinosaur trackways.

< Prev   CONTENTS   Next >