Australia's stampeding dinosaurs take a dip

Jan 08, 2013

(Phys.org)—Queensland paleontologists have discovered that the world's only recorded dinosaur stampede is largely made up of the tracks of swimming rather than running animals.

The University of Queensland's (UQ) PhD candidate Anthony Romilio led the study of thousands of small dinosaur tracks at Lark Quarry Conservation Park, central-western Queensland.

Mr Romilio says the 95-98 million-year-old tracks are preserved in thin beds of siltstone and 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 scratched the ," Romilio said.

"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.

"If that was the case we would expect to see a much flatter impression of the foot preserved in the ."

Mr Romilio said that similar looking swim traces made by different sized dinosaurs also indicated fluctuations in the depth of the water.

"The smallest swim traces indicate a minimum water depth of about 14 cm, while much larger ones indicate depths of more than 40 cm," Mr Romilio said.

"Unless the water level fluctuated, it's hard to envisage how the different sized swim traces could have been preserved on the one surface.

"Some of the larger tracks are much more consistent with walking animals, and we suspect these dinosaurs were wading through the ."

Mr Romilio said the swimming dinosaur tracks at Lark Quarry belonged to small, two-legged known as ornithopods.

"These were not large dinosaurs," Mr Romilio said.

"Some of the smaller ones were no larger than chickens, while some of the wading animals were as big as emus."

The researchers interpreted the large spacing among many consecutive tracks to indicate that the dinosaurs were moving downstream, perhaps using the current of the river to assist their movements.

Given the likely in water depth, the researchers assume the tracks were formed over several days, maybe even weeks.

Previous research had identified two types of small at Lark Quarry: long-toed tracks (called Skartopus) and short-toed tracks (called Wintonopus).

The UQ scientists found that just like you 'shouldn't judge a book by its cover', you also 'shouldn't judge a track by its outline'.

"3D profiles of 'Skartopus' tracks reveal that they were made by a short-toed trackmaker dragging its toes through the sediment, thereby elongating the tracks," explained Romilio.

"In this context, they are best interpreted as a just another variant of Wintonopus."

Romilio's supervisor and coauthor of the new paper, Dr Steve Salisbury, added that, "3D analysis of the Lark Quarry tracks has allowed us to greatly refine our understanding of what this site represents.

"It is also allowing us to learn more about how these dinosaurs moved and behaved in different environments," Dr Salisbury said.

For the past 30 years, the tracks at Lark Quarry have be known as the world's only record of a 'dinosaur stampede'.

Previous research by Romilio and Salisbury in 2011 also showed the larger tracks at Lark Quarry were probably made by a herbivorous dinosaur similar to Muttaburrasaurus, and not a large theropod, as had previously been proposed.

"Taken together, these findings strongly suggest Lark Quarry does not represent a 'dinosaur stampede'," Romilio said.

"A better analogy for the site is probably a river crossing."

Dr Salisbury said regardless of how it was interpreted, these findings took nothing away from the importance of the site.

"Lark Quarry is, and will always remain, one of Australia's most important dinosaur tracksites," Dr Salisbury said.

The new study was published in the January 2013 issue of Journal of Vertebrate Paleontology.

Explore further: Changing dinosaur tracks spurs novel approach

Related Stories

Scientists discover first dinosaur trail in Victoria

Aug 10, 2011

Two sandstone blocks discovered by palaeontologists have provided the most extensive evidence of dinosaur footprints in Victoria. Found at Melanesia Beach, near Cape Otway, they represent 85 per cent of the ...

Polar dinosaur tracks open new trail to past

Aug 09, 2011

Paleontologists have discovered a group of more than 20 polar dinosaur tracks on the coast of Victoria, Australia, offering a rare glimpse into animal behavior during the last period of pronounced global warming, about 105 ...

Ancient mammal tracks found at national monument

Jul 24, 2009

(AP) -- Hundreds of tiny footprints left by mammals some 190 million years ago have been found on a canyon wall in a remote part of Dinosaur National Monument, park officials said Thursday.

How to look at dinosaur tracks

Apr 30, 2007

A new study appearing in the May issue of The Journal of Geology provides fascinating insight into the factors geologists must account for when examining dinosaur tracks. The authors studied a range of larger tracks from t ...

Recommended for you

Crowd-sourcing Britain's Bronze Age

15 hours ago

A new joint project by the British Museum and the UCL Institute of Archaeology is seeking online contributions from members of the public to enhance a major British Bronze Age archive and artefact collection.

Roman dig 'transforms understanding' of ancient port

16 hours ago

(Phys.org) —Researchers from the universities of Cambridge and Southampton have discovered a new section of the boundary wall of the ancient Roman port of Ostia, proving the city was much larger than previously ...

User comments : 0

More news stories

Newlyweds, be careful what you wish for

A statistical analysis of the gift "fulfillments" at several hundred online wedding gift registries suggests that wedding guests are caught between a rock and a hard place when it comes to buying an appropriate gift for the ...

Can new understanding avert tragedy?

As a boy growing up in Syracuse, NY, Sol Hsiang ran an experiment for a school project testing whether plants grow better sprinkled with water vs orange juice. Today, 20 years later, he applies complex statistical ...

Roman dig 'transforms understanding' of ancient port

(Phys.org) —Researchers from the universities of Cambridge and Southampton have discovered a new section of the boundary wall of the ancient Roman port of Ostia, proving the city was much larger than previously ...

Crowd-sourcing Britain's Bronze Age

A new joint project by the British Museum and the UCL Institute of Archaeology is seeking online contributions from members of the public to enhance a major British Bronze Age archive and artefact collection.

Hackathon team's GoogolPlex gives Siri extra powers

(Phys.org) —Four freshmen at the University of Pennsylvania have taken Apple's personal assistant Siri to behave as a graduate-level executive assistant which, when asked, is capable of adjusting the temperature ...

Better thermal-imaging lens from waste sulfur

Sulfur left over from refining fossil fuels can be transformed into cheap, lightweight, plastic lenses for infrared devices, including night-vision goggles, a University of Arizona-led international team ...