Of Dinosaurs, Marketing and Truth; Lark Quarry

We were 100km south of Winton, in remote central western Queensland. As we sat and had lunch under the little shelter – even in autumn the temperature was well over 30 degrees – a dinosaur arrived to inspect us. It was small, quick, warm-blooded and feathered, like many of its direct forebears among the Theropod group of dinosaurs which perished in the aftermath of the cataclysmic meteorite strike some 65 million years ago.

Grey-headed Honeyeater Lichenostomus keartlandi, Lark Quarry CP;
a living dinosaur.

Coincidentally we had just come from inspecting with some awe a superb area of direct evidence of the existence of some of these Theropod ancestors, carefully protected in a purpose-built structure just metres away. This was Lark Quarry Conservation Park, gazetted in 1982 to protect the spectacular evidence, as it was interpreted, of the only dinosaur ‘stampede’ to be so far discovered, in the form of over 3000 fossilised footprints. National Heritage Status was applied in 2004.

Lark Quarry dinosaur site interpretive centre, set in a beautiful arid landscape.
Its forerunner was a large roof, erected in 1979 to protect the newly exposed dinosaur tracks.
When the Conservation Park was gazetted in 1982 a walkway was constructed above it to provide a memorable viewing experience. The superb visitors' centre opened in 2002 (and reopened the following year when an internal rammed earth wall, which collapsed almost immediately, was repaired!). It is jointly managed by Queensland Parks and Wildlife Service and Winton Shire Council, with advice from the Queensland Museum.
Today access to the footprints is only possible in the company of a trained volunteer guide, for a modest fee.

The world of 95 million years ago was a very different one from the one we enjoyed that day, walking a track through the stunted woodland and spinifex-covered ‘jump-ups’ after viewing the tracks.

The modern landscape is an arid one, dominated by hard-capped sedimentary 'jump-ups' covered with spinifex (spiny hummock grasses of the genus Triodia, which dominate 25% of Australia) above plains where Normanton Box Eucalyptus normantonensis, a shrubby mallee form, is the most common tree.
The wet forested swamplands that the dinosaurs inhabited are hard to imagine now.

Back then, deep into the Cretaceous but 30 million years before the sudden extinction of all non-bird dinosaurs, the land was dominated by forested wetlands, warm and humid with over 1000mm of rain a year. According to the understanding of those who painstakingly excavated, protected and interpreted it, the scene forever set in stone was played out when a large Theropod dinosaur (not Tyrannosaurus rex but of its ilk) surprised a mixed herd of small Theropods and Ornithopods (the ‘other’ major group of dinosaurs, mostly herbivores which, despite their name – ‘bird foot’ – did not lead directly to modern birds!) at a waterhole. In the panic which ensued, the confusion of tracks of the small dinosaurs is overlaid by the massive footprints of the huge predator. The clarity of some of them is superb. 

The small dinosaurs are described as long-toed Skartopus (a Theropod) and short-toed Wintonopus (an Ornithopod). It is important to recognise that both species are known only from footprints (not an unusual situation with dinosaurs, the term for their study being ichnology); Skartopus is known only from Lark Quarry. Further, the big predator is the only evidence that large carnivorous Theropods occurred in Cretaceous Australia (though there had previously been some in the Jurassic).

The trackway from the viewing platform, a chaos of clearly identifiable tracks.
There are doubtless many more still covered by the surrounding rock, visible at the back.

The clarity of many of them seems remarkable;
to the left can clearly be seen the long-toed prints of Skartopus.

Here a massive footprint of the apparent pursuing predator overlays the smaller prints.

It’s a great story, and one which is worth a lot of money to the Shire, as a lot of people make the trek of 100km from Winton, and presumably many of them stay an extra day there to do so. The street rubbish bins in Winton are in the shape of dinosaur feet, and signs point the way to the Dinosaur Stampede. 

But... And isn’t there always a but? Things may not always be as they seem; science is an eternally ongoing process of investigating further, questioning the accepted, testing what has already been taken as given. And so it is with the Lark Quarry site.

The investigative heroes, or spoiling villains, depending on your perspective, are (then Ph D student) Anthony Romilio and his supervisor Steven Salisbury, both of the University of Queensland. It began with a publication in 2011, wherein they re-examined the big ‘predator’ tracks and concluded that in fact they belonged to a large vegetarian Ornithopod, similar to the famed Muttaburrasaurus langdoni, named for the nearby town of Muttaburra. This is not the first time it had been suggested that the tracks might be so explained, but no-one had previously done the detailed analysis.

This removes the anomaly (which certainly didn't represent an impossible problem) of this being the only evidence of a Tyrannosaurus-type in Australia at that time. It also led to the next question; if this was a harmless herbivore, why were the little ones fleeing? The appearance of an elephant doesn’t create panic among antelopes. So, Romilio and Salisbury, plus Ryan Tucker of James Cook University, looked again at the ‘stampede’ tracks, and concluded in January this year (2013) that they are no such thing. Worse, they decided that Skartopus didn’t even exist!

Their explanation, painstakingly studied and explained, is that this was a crossing point, used by many animals over a period of time. Some strides were simply too long for the size of the animal, which would be explained if they were ‘bouncing’ through water, especially downstream. The long-toed ‘Skartopus’ tracks were actually those of Wintonopus in relatively deep water, pushing along the bottom with their claws.There is a nice little animation here which helps explain it.

'Skartopus' tracks, now interpreted as being made by a buoyed-up Wintonopus pushing along the bottom sediments as it part-floated across the river.

Very similar swim-traces like these were made by different-sized dinosaurs, indicating that the water depth varied. The authors believe that the footprints represent not a single panicked event, but a period of days or even weeks during which animals either swam or waded the crossing, depending on its depth and their size, which ranged from that of a chook to an emu.

Wintonopus crossing the river, leaving the characteristic deep scratches in the sediment,
as illustrated by researcher Anthony Romilio, courtesy of Science Daily.

Is this definitive? Of course not, though it’s pretty convincing and to date hasn’t been challenged. Does this devalue the site? Again, of course not, it simply refines our understanding of what happened. It’s as close to a photograph of life in the Permian as we’re going to get and is of world significance. The only importance of the ‘stampede’ scenario was a marketing one. Sadly this has influenced some people to seek to suppress the science – always a sad situation – and some Shire representatives have instructed the volunteer interpreters not to mention the new evidence.

Even if this interpretation proves not to be the ultimate ‘truth’ about the site, it is a current truth and deserves as much air and light as the more ‘sellable’ one. Truth has a way of emerging though and commercial interests are unlikely to bury it for long. Better that it was told now.

And in that vein I must sadly accept that the little dinosaur which visited us at lunch that day probably didn’t have direct Theropod ancestors among the nearby track-makers after all. It was a good story while it lasted, but that is after all the nature of science. 

Don’t take my word for it though – go and see for yourself some time. And when you do, be sure to ask about this story; they need to know that we know...

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