ESTIMATING SPEEDS OF DINOSAURS FROM TRACKWAYS: A RE-EVALUATION OF ASSUMPTIONS

Rainforth, Emma C., and Manzella, Melissa, Environmental Science, Ramapo College of New Jersey, 505 Ramapo Valley Road, Mahwah, NJ 07430; erainfor@ramapo.edu, mmanzell@ramapo.edu


For 30 years, using equations determined by Alexander (1976), paleontologists have estimated speeds of dinosaurs from their trackways; the fundamental assumption, based on limited observations, was that dinosaur hip height is approximately four times foot length. Thulborn (1990) subsequently determined that the leg length to foot length ratio ranges from 4.5-6.0, according to type and size of dinosaur. Given that the focus of many published footprint studies is to estimate dinosaur speed from Alexander’s equations, it is critical that the hip height of the track maker can be ascertained from the footprint measurement. If there is high variability in the ratio of hip height:foot length within a group of dinosaurs, speed estimates are going to be extremely unreliable.
This study examined the relationship between foot length and leg length in a variety of dinosaurs. Measurements of 24 dinosaur specimens included ornithischians (bipedal and quadrupedal), theropods, dinosauriforms, birds, and sauropods. Leg length was defined as femur + tibia + metatarsal III; foot length was defined as that part of the foot preserved in footprints (digit III phalanges ± claw + metatarsal III – metatarsal IV). Leg and foot lengths were compared and it was found that in bipedal ornithischians the foot to leg length ratio is ~5.4-5.9, and in theropods, 2.8-4.2. Contrary to previous studies, we found that (1) there is no correlation between dinosaur size and foot to leg length ratio, (2) the foot to leg length ratio is greater than previously estimated, and (3) the foot to leg length ratio is highly variable for each group of dinosaurs. We conclude that estimating dinosaur speed from trackways should not be undertaken lightly, and the results be interpreted with caution.








Geological Association of New Jersey 24th Annual Meeting, October 12-13, 2007. In Rainforth, E.C. (ed.), 2007, Contributions to the Paleontology of New Jersey (II): Field Guide and Proceedings, Geological Association of New Jersey 24th Annual Conference and Field Trip, p. 4.