A Moment of Terror in Stone
About 95 million years ago, a flat, muddy lakeside in ancient Queensland was the scene of sudden panic. Over a space the size of a basketball court, more than 3,300 fossilized footprints record the chaotic movements of a herd of small dinosaurs. The tracksite, part of the Winton Formation sandstone, holds the only known fossil evidence of a dinosaur stampede in the world. The scene features at least 150 small, two-legged dinosaurs, including chicken-sized coelurosaurs and larger, emu-sized ornithopods. The density of the prints is exceptionally high, with an average of 16.36 footprints per square meter on the main exposed surface.
The footprints belong to two main ichnotaxa (a classification based on trace fossils): Wintonopus, made by small plant-eating ornithopods, and Skartopus, attributed to small carnivorous coelurosaurs. These creatures were gathered at the water's edge when a much larger dinosaur appeared, triggering a frantic escape. The event was preserved when the mud tracks were buried by sand and other sediments as water levels rose and fell, eventually turning to stone over millions of years. The entire fossil surface is now protected from weathering by a large, climate-controlled conservation building erected in 2002.
A Scientific Debate
The classic interpretation of the Lark Quarry tracks involves a large, carnivorous theropod, perhaps six meters long with 50-centimeter feet, causing the smaller dinosaurs to flee. The large tracks were originally assigned to the ichnogenus Tyrannosauropus. However, later scientific analysis has challenged this entire narrative. Some research suggests the large tracks, reassigned to the ichnogenus Amblydactylus, were made not by a predator, but by a large plant-eating dinosaur similar to Muttaburrasaurus.
Further studies have proposed an alternative to the stampede hypothesis. Analysis of the sediments suggests the tracks may have been made over a longer period, perhaps several days, as different groups of dinosaurs crossed a seasonal water channel. In this interpretation, the jumble of tracks is not a single moment of terror, but an accumulation of footprints left by dinosaurs walking and wading through the water. Scientists have also found that the footprint shapes of Skartopus and Wintonopus overlap, suggesting they may have been made by the same type of dinosaur moving in different ways on the soft sediment. This ongoing scientific debate adds a layer of complexity to the story fossilized in the rock.