Sparrow-sized raptor Dromaeosauriformipes rarus used its wings to glide

Dromaeosauriformipes rarus is a species of dinosaur so small that when their tracks were first discovered, paleontologists thought juveniles might have made them. The smallest dinosaur tracks ever discovered have since been confirmed as a species of raptor the size of a modern-day sparrow. Now, scientists have found tracks that appear to show that these tiny theropods may have been able to fly, or at least bound, using their wings for assistance.

In South Korea, in the Jinju Formation, an area rich with fossilized footprints, scientists found two trackways made by the raptors.

The second trackway showed three identical footprints spaced much farther apart, with steps of 25 centimeters and 31 centimeters. To make such strides using only hindlimbs, the authors of the 2018 paper calculated that the little biped must have been moving at 38 kilometers per hour—roughly 10.5 meters per second, faster than sprinter Usain Bolt's world-record 100-meter dash.

That grabbed the attention of paleontologist Alexander Dececchi of Dakota State University and lead author of the new paper. "How would this work?" he said. "Well, there's only one way—and that's if the wings are helping them."

Science

While Dececchi and his team are convinced that this is evidence of a "takeoff, landing, or … wing-aided running," not everyone is convinced.

"The claims are quite extraordinary, but I don't think the evidence presented is equally as extraordinary," says paleontologist Peter Falkingham of Liverpool John Moores University, who specializes in dinosaur locomotion and footprint analysis.

If confirmed, this discovery would add a new evolutionary path to flight, in addition to that which led to modern-day birds.

Previously: Great Moments in Pedantry: How "Jurassic Park" got Velociraptors wrong