British and U.S. researchers say they've used X-ray video techniques to record how a large bird, a guinea fowl, makes tracks in an effort to better understand preserved dinosaur tracks and how they were make.
The researchers the Royal Veterinary College in London, working with colleagues at Brown University, used X-Rays to make a video of the birds walking through a trough filled with poppy seeds in an effort to create a 3D model of how tack get made.
What has made studying ancient dinosaur footprints difficult is a lack of knowledge about the interaction between a creature's foot and a substrate, which might be hard and flat or porous and deformable, like sand, clay or mud.
Although footprints in soft substrate are often better preserved, they can be complex because their creation might involve the creature making them sinking a bit into the substrate then having to pull the foot out.
Researchers Peter Falkingham and Stephen Gatesy decided to use guinea fowl as a stand-in for a similarly-sized dinosaur, Corvipes lacertoideus, which left track in some sediment around 250 million years ago in the northeastern United States.
Since birds are the direct ancestors of dinosaurs, the researchers could have used almost any bird species, and admitted the choice of a guinea fowl was somewhat arbitrary.
"It just happened to be both available and the right size to fit in the X-ray machine," says study lead author Falkingham of the London college said.
The researchers placed a long trough filled with poppy seeds, which act in a manner similar to sand, inside an enclosure that had been equipped with X-ray video equipment that captured images of both of the bird's flesh and bones and also the movement of the seeds as the bird walked through them.
The resulting video "is the first time anyone has been able to see a footprint being formed," Falkingham says.
While the birds left almost indistinguishable footprints on the surface of the seeds, because of the way the seeds collapsed as they pulled their feet out, clearly visible prints could be made out half an inch below the surface in the X-ray images.
However, those prints did not resemble the true shape of the birds' feet because the birds were spreading their toes and they set their feet down then brought them together again when they lifted their feed.
Scientists have seen the pattern this created in preserved dinosaur tracks, the researchers noted, and understanding how tracks are formed will help paleontologists reconstruct the movement of dinosaur feet.
