About a 107 million years ago a dinosaur from the family of the Tyrannosaurus Rex stalked or followed a long-necked herbivorous giant along what is now known as the Paluxy Riverbed, near Glen Rose, Texas.
At least, that's what the fossil footprints seem to show. But despite this being one of the most famous dinosaur tracksites in the world, it was at risk of being lost to scholars, and part of it was already gone — until now.
Using old photos and computer software, a group of researchers successfully created a 3-D digital model of the footprints, published today in the journal PLOS ONE.
Almost lost
In 1939 Roland T. Bird, who collected fossils for Barnum Brown of the American Museum of Natural History, wrote about a new and exciting discovery in the Paluxy Riverbed. He found the first unambiguous tracks of a sauropod in the area, which he named Brontopodus after the then-most famous of the sauropods, the non-existent Brontosaurus.
Along this section of the river, it seemed the sauropod was followed by a theropod, which was probably an Acrocathosaurus, a predator related to and similar in size and shape to the Tyrannasaurus. Though it's hard to say what happened there millions of years ago, theories range from one dinosaur following or stalking the other to an actual dinosaur attack.
Whatever it was, museums wanted a part.
Bird returned in 1940 to excavate the site. During the excavation he took photos and hand-drew maps. Then, this particular portion of the riverbed was cut out and split into three parts.
One portion was sent to the American Museum of Natural History, one part to the Texas Memorial Museum, and the third section was lost or destroyed. And in 1988, the section in Texas began to deteriorate.
Reconstructing the tracks
A group of researchers decided to try and digitally reconstruct the three parts together, using a technique called photogrammetry to stitch the information from the photos together, showing what the site looked like before it was taken out of the riverbed.
Only 12 of Bird's 17 photos could be matched and used for the reconstruction, and researchers didn't have much information about those pictures, which would help see how they connected. What they did have was combined with laser scans of the blocks in Texas and New York, and then compared to the old hand-drawn maps.
"I’m totally blown away that it worked, given that photogrammetry works best if you know focal lengths, lens used, and sensor size, and obviously we had none of that," study researcher Peter Falkingham, of the University of London and Brown University, told Business Insider in an email.
According to Falkingham, this success is extremely promising. Not only will it help inform upcoming research on tracks, but it could be used to restore other old sites and artifacts.
Here's the model they ended up with, which shows the Acrocathosaurus and Sauropod tracks left in the muddy riverbed while the predator stalked its prey:
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