An ornithopod, a small, two-legged herbivorous dinosaur.
QUEENSLAND palaeontologists have discovered the world's only recorded dinosaur stampede is largely made up of the tracks of swimming, not running, animals.
University of Queensland PhD candidate Anthony Romilio led the study of thousands of small dinosaur tracks at Lark Quarry Conservation Park in Queensland's central west.
The tracks, which are 95 to 98 million years old, are preserved in beds of siltstone and sandstone deposited in a shallow river when the area was part of a vast, forested floodplain.
''Many of the tracks are nothing more than elongated grooves, and probably formed when the claws of swimming dinosaurs scratched the river bottom,'' Mr Romilio said on Wednesday.
''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. It's difficult to see how tracks such as these could have been made by running or walking animals.''
Mr Romilio said the swimming dinosaur tracks at Lark Quarry belonged to small, two-legged herbivorous dinosaurs known as ornithopods (pictured). ''These were not large dinosaurs. Some of the smaller ones were no larger than chickens, while some of the wading animals were as big as emus,'' he said.
Previous research had identified two types of small dinosaur tracks at Lark Quarry: long-toed tracks, called Skartopus, and short-toed tracks, called Wintonopus.
For the past 30 years, the tracks at Lark Quarry have been known as the world's only record of a dinosaur stampede.
A 2011 study showed the larger tracks at Lark Quarry were probably made by a herbivorous dinosaur and not a large theropod, as had previously been proposed.
''Taken together, these findings strongly suggest Lark Quarry does not represent a dinosaur stampede. A better analogy for the site is probably a river crossing,'' Mr Romilio said.