A team of researchers including paleontologists from the University of Alberta have found evidence that younger tyrannosaurs were more slim and slender than older tyrannosaurs.
The group, made up of a collaboration of University of New England, University of Bologna, Alberta-based Cutbank Palaeontological Consulting, the Philip J. Currie Dinosaur Museum and the University of Alberta, analyzed fossilized footprints of the dinosaurs to see how their feet were shaped and how they moved.
“The results suggest that as some tyrannosaurs grew older and heavier, their feet also became comparably more bulky,” said Nathan Enriquez, lead author on the study and a PhD student at the University of New England.
The team documented tyrannosaur footprints in the Grande Prairie area, analyzing them using a method called geometric morphometrics, which uses a computer to scale the footprints to the same size and clarify variations in the track shape along a trackway.
They found that the “heel” impressions were greater in tracks that were larger.
“The smaller tracks are comparably slender, while the biggest tyrannosaur tracks are relatively broader and had much larger heel areas,” said Enriquez. “This makes sense for an animal that is becoming larger and needs to support its rapidly increasing body weight.”
This study also suggests that as tyrannosaurs got older their ability to run would decline, and although previous studies of tyrannosaurs’ bone and muscles had reached similar conclusions, this new evidence from the footprint study reinforces that the dinosaur would get less athletic and bulkier with age.