HARARE (dpa) – A weekend in northern Zimbabwe late last month gave South African scientist Theagarten Lingham-Soliar a set of profound experiences that only a handful of people on earth could match.
He was at the centre of a total solar eclipse that turned the world around him black for three minutes in the mid-afternoon. The same day, peering at the ground on a sandstone river bed in Zimbabwe’s Zambezi valley, he realised he was looking at a frozen moment in time where 180 million years ago at least three five-metre carnivorous dinosaurs crossed paths, perhaps within minutes of each other.In the gloom of sunset in a small tributary of the Ntumbe river in the Chewore safari area, the bulges in the rock floor could be viscous mud. The clearly defined, duck-like footprints, 40 centimetres across, could have been left by a pack of Allosauruses passing 10 minutes ago.The new trackway of about eight prints led more or less straight up the river. What startled Lingham-Soliar, senior lecturer in the department of Zoology at the University of Durban-Westville in South Africa, was the second trail that wandered across the main trail, and then a second trail that cut across.“They had to be made very close in time, at most a couple of hours apart,” he said. The Jurassic sun was far hotter than it is now, and would have baked the mud quickly. “It means there was a lot of movement there. It must have been a very busy point.”Closer examination of what appeared to be two distorted footprints revealed each one slightly squashed by another print on top of it. It was even more likely that were made almost simultaneously. Allosaurus, predecessor to the Tyrannosaurus Rex and the dominant carnosaur (carnivorous dinosaur) of the mid-Jurassic age, has been well known to palaeontologists for decades.From hundreds of fossil bone sites (though hardly any in Africa), they reconstructed a picture of lumbering, solitary beasts with rudimentary brains incapable of anything as complex as social behaviour. But, says Lingham-Soliar, “fossils are of dead animals.Seeing footprints is like seeing the animals moving.” Palaeontology has been shaken in recent years by the new science of trackways, following the discovery of trails of footprints in North America. From them emerged radical new theories of dinosaurs that were not only gregarious, but lived in complex family systems and may even have hunted in packs.“We are getting a carnivorous dinosaur that is in contact with other carnivorous dinosaurs. This is not just individuals walking about. Their behaviour patterns may have been grouped together.” The fact that the prints are left by animals walking at a regular, unhurried pace, with no sign of chase or flight, led to another conclusion: “They didn’t seem to be afraid of each other. They were all congregating in the same area. It may have been a family group,” he said. “This is very exciting,” said Lingham-Soliar. “This is perhaps the best evidence so far to indicate that Allosaurus may well have hunted in a group.”The first dinosaur trackway – a trail 34 footprints of an Allosaurus – was identified by Zimbabwean geologist Tim Broderick 17 years ago, only 2 kilometres away from the new site. “Now we see there are masses of footprints in the area,” said Lingham-Soliar. “We found about 50 in the space of 90 square metres. We are convinced we are only skimming the surface.”In some of the prints, the claw marks of the three toes are visible. Others are so fine that the knobbly swellings of the joints are defined. On one trackway, the two footprints come together and behind it is a long, smooth indentation – where the reptile halted in its path stood up – perhaps to sniff the air – and rested its 5 metre tail in the mud.Another is a series of tiny footprints that Lingham-Soliar and Broderick decided was a baby Allosaurus. At one point, the marks show where the infant slipped and fell forward, but tried to break its fall by stretching out its manus (the evolving hand) to the muddy ground. Many of the prints in the riverbed are impressed in different strata of the stone, meaning they were left at least 1,000 years of each other.“We have a large predator roaming around the region, unchanged for 1,000 years. To be able to pinpoint an animal for so long is critical,” said Lingham-Soliar. “Nobody has been able to say before that this particular animal was around in this kind of environment for so long. “All this is a very unusual set of events we are recording. It makes the Chewore area a very important area of the world for footprint studies. Now Africa is on the map.”
