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| Lark Quarry |
Lark Quarry Dinosaur Trackways
95 million years ago Lark Quarry was part of a great river
plain, with sandy channels, swamps, and lakes brimming with freshwater mussels,
lungfish, and crocodiles. Rainfall was over a metre per year, so the
surrounding lowland forest was lush and green.
On the day our drama unfolds, some 95 million years ago,
herds of small two-legged dinosaurs came to drink at the lake. There were at
least 150 dinosaurs of two different kinds - carnivorous coelurosaurs about the
size of chickens, and slightly larger plant-eating ornithopods, some of them as
large as emus.
A huge meat-eating theropod, smaller than a Tyrannosaurus,
approached the lake. It slowed, saw the other dinosaurs gathered at the water’s
edge and began to stalk, then turned and charged. The stampeding herd of
smaller dinosaurs left a chaotic mass of footprints in the mud as they ran to
escape.
The site where the dinosaur footprints were found was once a
streambed leading into a lake. The water level had dropped, exposing mudflats.
When the dinosaurs stampeded, they left perfect footprints in the half-dried
and still plastic mud. Sun, wind, and rain would normally destroy tracks like
this. But just a few days after the footprints were made, it began to rain and
the lake rose gently, covering the tracks with sandy sediments before the mud
had dried enough to crack. The next flood buried them below a meter of sand and
a meter of mud. Over time, more sediment was laid down. As millions of years
passed, the sediment layers were compressed to form rock and a low range
eventually formed.
Local Station Manager, Glen Seymour, first discovered the
Dinosaur Trackways in the 1960s. He thought they were fossilised bird tracks,
and showed them to local enthusiast Peter Knowles. What they were looking at
was, and still is today, the world's only recorded evidence of a dinosaur
stampede.
It wasn’t until scientists visited the area in 1971 that the
Trackways story began to unfold. Although the scientists were looking for
Cretaceous mammals, Peter showed them the dinosaur tracks as a matter of
interest. The last period of the Mesozoic era, around 146 to 65 million years
ago. Many dinosaurs and other organisms died out at the end of this era.
Five years later, paleontologists and volunteers began the
task of removing rock to expose the Trackways layer. In the years that followed, the Trackways began to
deteriorate and palaeontologists from Queensland Museum raised concerns about
the possible loss of the Trackways unless action was taken to stabilise and
protect them from further damage. A new conservation building, funded by Queensland Heritage
Trails Network, was erected in 2002.
Fossilised footprints would not tell us much without
scientific interpretation. Scientists used mathematics, comparisons and
inspired guesswork to uncover the story of the Trackways.
Back in the lab, scientists studied each footprint print on
a latex mould taken from the site. The footprints were measured and described,
and (where individual tracks could be followed) pace length, stride length and
pace angulation were measured. Scientists then compared the footprints to dinosaur
skeletons from all over the world with feet roughly matching the Lark Quarry
tracks. The dinosaur running speeds were worked out using equations
based on the locomotion of living animals, incorporating size, weight and
flexibility differences. Once the scientists knew which dinosaurs made the tracks,
how many there were and how fast they were moving, they were able to piece
together the stampede story.
In recent years there has been some doubt about the original scientific interpretation. Around 2010, some scientists looked more closely at dinosaur tracks. When various proportions of the outlines that had been published in 1984 were compared alongside other dinosaur tracks, these scientists suggested that they appeared to belong to a plant-eating ornithopod rather than a theropod. If it was a large-bodied ornithopod, maybe it was something similar to Muttaburrasaurus, which we know inhabited this part of Queensland around the time the Lark Quarry tracks were made.
Since both the large footprints and drag marks have small dinosaur tracks overprinting them, the dinosaurs that made the smaller tracks must have crossed the area much later. From research that was published in 2013 it was know that some of these smaller dinosaurs were running, some were wading and some were even swimming. It would appear that the footprints could have been made over a period of time and not all on the one day.
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In recent years there has been some doubt about the original scientific interpretation. Around 2010, some scientists looked more closely at dinosaur tracks. When various proportions of the outlines that had been published in 1984 were compared alongside other dinosaur tracks, these scientists suggested that they appeared to belong to a plant-eating ornithopod rather than a theropod. If it was a large-bodied ornithopod, maybe it was something similar to Muttaburrasaurus, which we know inhabited this part of Queensland around the time the Lark Quarry tracks were made.
Since both the large footprints and drag marks have small dinosaur tracks overprinting them, the dinosaurs that made the smaller tracks must have crossed the area much later. From research that was published in 2013 it was know that some of these smaller dinosaurs were running, some were wading and some were even swimming. It would appear that the footprints could have been made over a period of time and not all on the one day.
Whatever the real story, it's a fascinating place to visit.
