More than 110 million years ago, two dinosaurs—a long-necked, herbivorous sauropod and a carnivorous therapod—ran through the mud of an ancient river bed near what is now Glen Rose, Texas. Their tracks, preserved in rock, were excavated in 1940 and removed from the riverbed to be studied. Though a third of the trackway was subsequently lost, scientists this week announced they have managed to reconstruct the scene of the prehistoric chase in its entirety, using photographs from the original excavation and a cutting-edge form of technology known as photogrammetry.
In 1940, when American paleontologist Roland T. Bird first discovered and excavated the dinosaur chase site—part of a larger site called the Paluxy River Trackway–he found that some of the therapod tracks were actually inside the sauropod tracks. This led Bird and other scientists to conclude that the meat-eating therapod (a top predatory group that includes Tyrannosaurus rex) was chasing the sauropod. Removed from the Paluxy River bed and divided into blocks, the tracks were taken to different locations for study, including the American Museum of Natural History in New York City and the Texas Memorial Museum.
Though some of the blocks (representing about a third of the trackway) have since been lost, a team of scientists has been able to achieve extraordinary results by turning to photographs taken by Bird during the 1940 excavation. According to an article published this week in the journal PLOS ONE, the scientists analyzed 17 of Bird’s photographs using a technique known as photogrammetry. After determining the angle from which each photo was taken, they melded views from different camera angles to build a digital model of the chase site with three-dimensional depth. By comparing the photographs with Bird’s hand-drawn map of the site, the scientists have reconstructed the entire 148-foot (45-meter) chase for the first time since its removal from the site.
Though the new 3-D image is fuzzier at the north end, where there were less comprehensive photographs, it is sharp enough to see the dinosaurs’ toe prints at the south end. Now, the researchers will be using their conclusions as part of their larger study of the tracks in the area. Having a 3-D model will allow them to study depth and weight distribution for each dinosaur, which in turn will help determine how the dinosaurs walked and how fast they were going. According to lead researcher Peter Falkingham from London’s Royal Veterinary College, the therapod tracks might have been made by an Acrocanthosaurus, while the sauropod was likely similar to Paluxysaurus or Sauroposeidon.
As Falkingham told the Daily Mail, the technology his team used is not new, and has already been implemented in various other fields to create highly accurate 3-D models. However, the new project showed that photogrammetry could be taken a step further, and applied with great success in the field of paleontology. “In recent years technology has advanced to the point where highly accurate 3D models can be produced easily and at very little cost just from digital photos,” Falkingham said. “That we can apply that technology to specimens, or even entire sites, that no longer exist but were recorded photographically is extremely exciting.”