What could a guineafowl strolling through a bed of poppy seeds have to do with a dinosaur footprint made 200 million years ago?Stephen Gatesy, professor of ecology and evolutionary biology at Brown, and his former postdoctoral fellow Peter Falkingham, now at the Royal Veterinary College in the United Kingdom, used measurements from X-ray videos of the 3-D foot movement of a chicken-like bird as an input for a computer simulation of a substrate of poppy seeds.
In this way, they could visualize the displacement of seeds through time and study the “birth” of tracks at different depths. The researchers then used the model to clarify previously unexplained features of a Jurassic dinosaur track.
Gatesy described a video summarizing the approach: “On the left, a guineafowl walking through poppy seeds is captured by high-speed (250 fps) video using X-ray and standard light imaging. Three-dimensional bone models have been registered by X-ray Reconstruction of Moving Morphology (XROMM) and overlaid on both videos. On the right are animations of our particle simulation produced using the real foot motion by the discrete element method (DEM).
Simulations enable visualization of how footprints form at any depth through interaction among foot shape, foot movement, and substrate properties. In this dry, sand-like material, very clear tracks are preserved below the surface, but these reflect foot entry and exit rather than static anatomy. Relating track features to formation dynamics helps explain the origin of track diversity in the fossil record and aids reconstruction of dinosaur locomotion.”
The birth of a dinosaur footprint: Subsurface 3D motion reconstruction and discrete element simulation reveal track ontogeny. Peter L. Falkingham and Stephen M. Gatesy. PNAS 2014; doi:10.1073/pnas.1416252111