Using measured stride and footprint lengths, scientists have calculated the speeds of over 60 dinosaur species. One of the real life factors to remember while doing these calculations is the gait of the dinosaurs when they made the tracks. The difference between walking and running and the transitions between these movements had to be kept in mind. Another factor was the actual leg bone lengths of the dinosaurs, which helped determine the reasonable speed types for the various dinosaurs. For example, the similar lengths of the femur and tibia bones in the legs of a Tyrannosaurus rex suggest a slower attainable speed than that of the ornithomimids, which had a shorter femur and longer tibia. With all these caveats in mind, some examples of the calculated speeds of dinosaurs include: