Doctoral student Anthony Romilio took 3D images of thousands of small dinosaur tracks from the central-western Queensland site. “Many of the tracks are nothing more than elongated grooves, and probably formed when the claws of swimming dinosaurs scratched the river bottom,” says Romilio. “Some of the more unusual tracks include ‘tippy-toe’ traces – this is where fully buoyed dinosaurs made deep, near-vertical scratch marks with their toes as they propelled themselves through the water.”
Other tracks provide clearer foot morphology, indicating an animal wading while partly supported by the water.
Most of the prints at Lark Quarry are from very small dinosaurs, and Romilio’s supervisor, Dr Steve Salisbury of the School of Biological Sciences, says the fact that they were able to touch the bottom while swimming suggests the water was just 14 cm deep. “Other traces look similar but are made by larger animals, suggesting the water must have been 40 cm deep at the time, so we think the tracks record crossings over a few days or a week during which the depth fluctuated,” says Salisbury.
While the evidence of changing water levels casts doubt on the idea of a single herd of panicked dinosaurs, Salisbury notes that when water depth increased many smaller dinosaurs would have left no mark on the bottom at all, suggesting that the total numbers making the...
