Tracks left by a bird-sized dinosaur suggest it used wings to run faster

22 Oct 2024, 13:23 by Bob Yirka

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Illustrated reconstruction of Dromaeosauriformipes rarus running along the muddy shore of an ancient lake. Credit: Alex Boersma/PNAS

A small international team of biologists, geologists and paleontologists has found evidence that a bird-sized dinosaur from the early Cretaceous used its wings to run faster. In their study published in the Proceedings of the National Academy of Sciences, the group analyzed both the footprints and the creature that left them and reported evidence for wing-assisted running.

Dinosaurs sometimes left behind footprints as they walked across stretches of mud. In some instances, these prints became fossilized and survived to modern times—they are known as trackways. Study of trackways has helped scientists learn more about how ancient creatures walked or ran.

In this new study, the research team focused their efforts on a trackway uncovered at a dig site in Jinju Formation, in a southeastern part of South Korea. The tracks were notable because of the large distance between footprints relative to their size—from 25 to 31 centimeters.

Testing of the tracks showed they were made approximately 106 million years ago and that the dinosaur that made them was mostly likely a bird-sized dinosaur known as Dromaeosauriformipes rarus.

In evaluating the measurements of the distance between the tracks and the size of the muscles in its legs, the researchers found that the tiny dinosaur could not have run fast enough for its footfalls to be so far apart without assistance—mostly likely from wings. They estimate it was running at 38 kph when the tracks were made.

Artist’s illustration of a pre-avian dinosaur flapping its arms to help it run at high speed. Credit: Julius T. Csotonyi

Because the tracks suddenly end, it is impossible to tell if the creature was taking off, landing or simply flapping wings as a means of land-based propulsion. Thus, it is not known if the dinosaur could fly. The possibility exists, however, because prior research has shown that D. rarus was feathered.

The findings add credence to theories that the emergence of flight was not linear, that many creatures evolved the ability independently. If it can be proven that D. rarus could fly, that would prove that feathered dinosaurs besides the avian lineage could fly. The researchers suggest that it is also possible that D. rarus represents a precursor to non-avian dinosaur flight.

More information: T. Alexander Dececchi et al, Theropod trackways as indirect evidence of pre-avian aerial behavior, Proceedings of the National Academy of Sciences (2024). DOI: 10.1073/pnas.2413810121

Journal information: Proceedings of the National Academy of Sciences