More than 100 million years ago, on a muddy stretch of land that is now Australia, nearly two-dozen species of dinosaur once roamed.

There were duck-billed ornithopods, which left long, three-toed tracks in their wake. Heavy armoured dinosaurs pressed large, tulip-shaped prints into the soil. Predators scratched the ground with their talons. And the feet of gigantic, long-necked sauropods created bathtub-sized depressions in the dirt.

Asteroids struck, continents moved, sea levels rose and fell. What was once a damp, forested environment surrounded by shallow seas became the hot, rugged coastline of northwestern Australia.

Richard Hunter lies next to a 1.7 metre dinosaur footprint belonging to a sauropod. The scale Richard is holding is 40cm long. Credit:Steve Salisbury

But the dinosaurs' tracks remained. The footprint assemblage, which contains evidence of 21 species, is the most diverse in the world, researchers reported Friday in the Journal of Vertebrate Paleontology.