How do scientists identify dinosaur footprints?

It is extremely uncommon for an animal's fossilized bones to be preserved along with its final footprints, and this makes it challenging to identify the exact species of animal that produced any particular print. However, scientists can narrow down the identities of dinosaur trackmakers by comparing the foot shape, pattern of movement and evidence of body size revealed by the tracks with what is known about dinosaur species living at the time the track was made. A small dinosaur running on two legs, for example, will leave very different prints than a large dinosaur moving slowly on four legs.

Fossil tracks of a nodosaur and a theropod.  The theropod print has  impressions left by three long toes.  The nodosaur print is rounder and shows the positions of five stubby digits.  Sketches show the positions of the bones in each foot.

Nodosaur and theropod footprints (left, top and bottom) and drawings of their foot bones (right). Click to zoom.

Several lines of evidence tell us that the print shown on the top row if this image was made by the front foot of an ankylosaur. The print has five blunt digits ("fingers") arranged in an arch, and behind them there is a faint impression of the "palm". The arrangement of hand bones and hoofed fingers in ankylosaurs, which we know from skeletons, could have created a print that looks like this. In addition, similar prints have been discovered in other places where ankylosaur bones have been found. Other kinds of dinosaurs had fewer digits, or claws instead of hooves, and their prints would reflect that. The bottom row of this image shows a theropod track and an outline of theropod foot bones for comparison.

Narrowing the identity down further, it is likely that the ankylosaur print was made by a nodosaur because this is the only kind of ankylosaur known from these deposits, and they are the most common Early Cretaceous ankylosaurs worldwide. The print is small, suggesting it came from a young animal.