The dinosaur in the coal mine

Fossil dinosaur footprints found 50 years ago in a Queensland coal mine – and long thought to belong to a massive Triassic carnivore – have been reanalysed, and found to belong to a large, docile herbivore, according to a new study out today in Historical Biology.

The researchers, from the University of Queensland (UQ), were able to study the prints in unprecedented detail after gaining access to the original fossil, whereas earlier research had been based on old drawings and photographs with limited detail.

“Unfortunately, most earlier researchers could not directly access the footprint specimen for their study,” says Anthony Romilio, UQ palaeontologist and lead author of the study.

“For years it’s been believed that these tracks were made by a massive theropod predator that was part of the dinosaur family Eubrontes, with legs over two metres tall.

“But in any other place around the world, meat-eating dinosaurs only achieved such a big size from the Jurassic period, so this was quite an anomaly.”

The reanalysis has revealed the tracks were actually made by a dinosaur known as a prosauropod, a vegetarian dinosaur with legs about 1.4 metres tall and a body around six metres long.

A chance encounter in a Queensland coal mine

The fossil dinosaur footprints were first uncovered 50 years ago, 200 metres underground at a coal mine near Ipswich, west of Brisbane.

“It must have been quite a sight for the first miners in the 1960s,” says Romilio. “You have these hard-working miners going about their day-to-day, and then standing back and finding this weird thing jutting down from the ceiling.”

According to study co-author Hendrik Klein, a fossil expert from Saurierwelt Paläontologisches Museum, Germany, the prints would have been hanging above the miners’ heads because they were laid down on water-sodden layers of plant debris, which would later have been filled in by silt and sand.

“This explains why today they occur in an upside-down position, right above our heads,” says Klein. “After millions of years, the plant material turned into coal, which was extracted by the miners to reveal a ceiling of siltstone and sandstone, complete with the natural casts of dinosaur footprints.”

The mine has long since closed, but in 1964, geologists from the Queensland Museum mapped the tracks and made plaster casts.

“We made a virtual 3D model of the dinosaur footprint that was emailed to team members across the world to study,” says Klein.

“The more we looked at the footprint and toe impression shapes and proportions, the less they resembled tracks made by predatory dinosaurs. This monster dinosaur was definitely a much friendlier plant-eater.

“This is still a significant discovery even if it isn’t a scary Triassic carnivore. This is the earliest evidence we have for this type of dinosaur in Australia, marking a 50-million-year gap before the first quadrupedal sauropod fossils known.”

Romilio says the footprints are a rare insight in what is a vacuum of information about dinosaurs in Australia in the Triassic, with only two dinosaurs known from the area from that period.

“Australia doesn’t have the same geological activity that lifts up and exposes these much older rocks,” says Romilio. “If you’re in the US, you’ve got older material that’s been forced up in mountains. You’ve also got areas where there were glaciers during the Ice Age that ploughed the landscape and exposed these older rocks.

“But here in Australia, we don’t have such a dramatic alteration of our landscape, so we don’t have that older material coming to the surface.”

If you’re a Queensland resident and want to meet our prosauropod, the cast footprint is on display at the Queensland Museum in Brisbane.