Dinosaur footprints and trackways are trace fossils, meaning they record the activity of an animal rather than its body parts. A single footprint can show the shape of a foot, but a trackway can reveal how an animal moved across soft ground. Paleontologists use trackways to study speed, posture, group behavior, and the environments where dinosaurs lived.
These fossils matter because they preserve moments of behavior that bones alone often cannot show.
A footprint forms when a dinosaur steps into soft sediment such as mud, silt, or wet sand, leaving an impression that later hardens and becomes buried. Over time, minerals cement the sediment into rock, preserving the track as a natural mold or cast. Scientists measure footprint length, stride length, pace, trackway width, and toe angles to infer body size and movement.
By comparing many tracks, they can distinguish walking from running, identify possible herding patterns, and reconstruct ancient shorelines, riverbanks, and floodplains.
Key Facts
- A footprint fossil is a trace fossil because it records behavior, not a body part.
- Stride length is the distance between two successive footprints made by the same foot.
- Pace length is the distance from one footprint to the next footprint, usually left to right or right to left.
- Trackway width helps estimate posture, with narrow trackways often suggesting limbs held more directly under the body.
- Relative speed can be estimated using speed = distance / time, but fossil trackways usually require stride length and hip height estimates.
- A common hip height estimate for many bipedal dinosaurs is hip height ≈ 4 × footprint length.
Vocabulary
- Trace fossil
- A fossil that preserves evidence of an organism's activity, such as a footprint, burrow, or feeding mark.
- Trackway
- A series of footprints made by one animal as it moved across a surface.
- Stride length
- The distance between two consecutive footprints made by the same foot.
- Mudstone
- A fine-grained sedimentary rock formed from compacted mud and clay-rich sediment.
- Substrate
- The surface material, such as mud or sand, that an animal stepped on when making a track.
Common Mistakes to Avoid
- Assuming every large footprint was made by a large dinosaur, because soft mud can spread and distort a track after the foot is lifted.
- Measuring stride from left foot to right foot, because stride length must compare two prints made by the same foot.
- Ignoring the rock layers around the track, because sedimentary context helps show whether the tracks formed on a riverbank, lake edge, floodplain, or beach.
- Treating a footprint as an exact mold of the foot, because claws, toes, skin texture, and pads may be missing or blurred depending on sediment conditions.
Practice Questions
- 1 A bipedal dinosaur track has a footprint length of 35 cm. Using hip height ≈ 4 × footprint length, estimate the dinosaur's hip height in centimeters and meters.
- 2 A trackway shows a stride length of 2.4 m between two right-foot prints. If a dinosaur took 6 strides, how far did it travel based on stride length?
- 3 Two trackways are found in the same mudstone layer, one with deep, wide, messy prints and one with shallow, sharp prints. Explain what differences in sediment moisture, animal weight, or movement could have caused the two patterns.