Wyoming dinosaur footprint officially measured
BILLINGS – Young guys and old fossils seem to converge in a unique and special way in Glenrock, Wyoming.
It was outside Glenrock, about 25 miles east of Casper, that Sean Smith found the skull of a triceratops in 1994 when he was only 19. His discovery led to the skull’s excavation and the eventual creation of the Paleon Museum to house the fossil. The find put the community of 2,600, situated on the southern bank of the North Platte River, on the paleontological map.
It was at a summer Paleon Museum dig years later that a 13-year-old Scott Persons visited and became more fully convinced – despite laboring under the hot Wyoming sun – that he would pursue paleontology as a lifetime profession.
“Before Glenrock, for me paleontology was dinosaurs in books and their skeletons in display halls and behind glass cases,” Persons said in a University of Alberta press release. “This was the first time I got my hands dirty in the field and in a fossil preparation laboratory.”
It was also during that visit that Smith showed Persons the dinosaur tracks.
“Sean led me out to a sandstone slope and started brushing away at an indented spot,” Persons recalled. “At first, it looked like a prehistoric pothole. But soon I could see the imprints of three big toes each with sharp claw tips. It was so cool my jaw dropped. Then, Sean pointed up slope, and there were two more!”
Now a graduate student at the University of Alberta, Persons helped Smith to formally measure and describe three dinosaur tracks embedded in nearby sandstone. Together, the duo authored a research paper on the rare footprints that has now been published in the peer-reviewed journal “Cretaceous Research.”
“It’s one of our first published items, so it’s a pretty big deal for us,” said Smith, who is now the director of paleontology at the museum.
The first three-toed track was noticed in the sandstone bed of a ravine in 2000. By digging under dirt and grass nearby, two more tracks from the same dinosaur were revealed in a left, right, left stride. By measuring the size of the tracks and distance between them Persons verified that they were made by a large theropod, like a tyrannosaur, about 66 million years ago.
“Tyrannosaur tracks are extremely rare, but what makes this site particularly cool is we have a left, right, left series, so we can measure stride lengths,” Persons told the Billings Gazette.
The distance between the tracks showed the meat-eating dinosaur was moving at a speed of about 2.5 to 5 mph – a slow trot.
“The tracks are just a bit too small to belong to a full-grown T. rex,” Persons said in the press release. “But they could very well be the tracks of an adolescent Tyrannosaurus rex, or they could belong to the closely-related smaller tyrannosaur Nanotyrannus. We really can’t say which.”
Other tracks dot the same stone – what was likely an ancient, sandy shore – including some type of ceratops – a family that includes the well-known triceratops – and a hadrosaur, the duck-billed dinosaurs commonly found in Montana fossil remains.
“One of the cool aspects about this is it deals with who walked in the same place at the same time,” Smith said.
The museum would like to excavate the tracksite to protect it from erosive weather, but its location in the ravine means the work would have to be done by hand, which isn’t practical for dealing with such a large slab. So for now, plaster casts of the tracks have been made and are on display at the museum.
Describing the theropod tracks fit in well with Persons’ doctoral thesis examining how dinosaurs walked and ran. As part of that research, he has also traveled to a central China tracksites that included impressions left by raptors. Persons hopes the published paper will help put the little museum that helped inspire him on the public’s radar.
“The tracks are still in the field,” he said. “If you go to Glenrock today, visit the Paleon Museum, and are up for a little hike, you can see the prints just like I did.”