World’s Largest Dinosaur Tracksite Has At Least 16,600 Footprints And Sets Many World Records

A record-breaking site in Bolivia preserves foot, tail, and clawprints left behind by hundreds, or even thousands, of dinosaurs in mud at the edge of what was then a lake. Finding all the prints, let alone establishing which came from the same individuals, will be an immense task, but already 16,600 prints have been found, the largest number ever recorded at one site. This set of tracks also sets the record for the most trackways, tailprints, and continuous swimways.

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A waterhole in Africa draws many species today, each of which will leave its prints in wet clay when conditions are right. The same thing must have happened millions of times through the Jurassic and Cretaceous periods, but only a few have survived until today. Conditions for preserving footprints are different from those that yield good fossil teeth and bones, so trackways often tell us a lot about times and places where we lack other good records.

Bolivia is particularly rich in dinosaur trackways, many of which have not been well-studied. However, the immense Carreras Pampa tracksite in Torotoro National Park represents an opportunity too good to pass up. A team led by Dr Raúl Esperante of the Geoscience Research Institute was rewarded with the realization that the site sets numerous world records, and have now described their observations of this abundance in a paper stretching to 125 pages.

“It’s amazing working at this site, because everywhere you look, the ground is covered in dinosaur tracks," the authors said in a statement. 

Most fossil tracksites preserve prints from a handful of individual animals. Lark Quarry in Australia has become famous for 3,300 prints made by three species. The longest continuous dinosaur trackway in Europe is in the UK and features hundreds of 166-million-year-old sauropod tracks. The world's previous longest dinosaur trackway (we may need to update our video below) is in Colorado, USA.   

Carreras Pampa is built on a different scale. Tracks have been found on an area spanning 7,485 m² (1.8 acres). The authors report 1,321 trackways (two or more prints made by the same individual) and 289 solitary prints, all laid down in the late Cretaceous when the end was nigh. A total of 16,600 three-toed therapod fossilized footprints set a new world record for the number of individual dinosaur footprints. 

The site hosts a wide range of print shapes and sizes that range from less than 10 centimeters (4 inches) to more than 30 centimeters (11 inches), indicating plenty of species were present during the brief window when the impressions could be preserved. Yet all seem to have been from theropod dinosaurs or birds, with none of the sauropods or ornithischians on which larger theropods fed, despite the finding of parallel sauropod tracks elsewhere in Torotoro. The vast majority of the print-makers were small, with only a few footprints larger than 30 cm found among the thousands. Few of the makers were likely to be more than 1.25 meters (4.2 feet) high.

Only one trackway was made by an animal likely to have weighed more than a ton.

Trackways claimed to show four-legged dinosaurs wading or partially swimming have aroused considerable controversy in recent years. There will be plenty to debate at Carreras Pampa; the authors argue that numerous claw marks at the site represent the highest number of continuous swimming trackways in the world, as the claws of dinosaurs swimming in shallow water scraped the mud.

The tracks identified at this point come from nine locations dotted across the site, together comprising two-thirds of the total area. How many more remain buried? Often, just two prints are seen approaching or arriving from the edge of a site, and the authors think longer trackways remain to be unearthed. In other cases, a specific animal’s tracks can be seen at one location, appearing again traveling on another sediment bank. 

Exposure in modern times must be very recent, because only quite small areas are badly eroded. The prints have become a tourist attraction, but fortunately, guides and park rangers have prevented damage to the site from non-experts who might get too close in their enthusiasm.

Most of the prints appear to have been made by animals moving at 5.5-7.5 kilometers per hour (3.3-4.8 miles per hour), faster than the average dinosaur footprints, but still leisurely and apparently neither fleeing predators nor chasing prey. However, there are exceptions, with a few tracks made by animals moving around 20 km/h (12 mph).

The preservation is so clear that tail traces can be seen on more than 30 trackways, the first time a dinosaur tail trace has been found anywhere in South America. Indeed, these are the first theropod tail traces found in the entire Southern Hemisphere.

“This site is a stunning window into this area’s past. Not just how many dinosaurs were moving through this area, but also what they were doing as they moved through,” the authors said. 

The study is open access in PLOS ONE.