Armed with powerful jaws and sharp teeth, tyrannosaurs were built to kill. But they were also built for something else, researchers say: speed.
As if giant, toothy dinosaurs weren’t scary enough, new evidence suggests tyrannosaurs were tailor-made for running. Even velociraptors, seen in “Jurassic Park” as gold-medal sprinters, weren’t so finely tuned for quickness, the new study concludes.
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Velociraptors “could drop down out of a tree and slash you apart,” says Eric Snively of the University of Wisconsin, La Crosse, who was not involved with the new study. But the new results, he says, “have shown that velociraptor and its relatives really were kind of pokey.”
The takedown of velociraptor started with an exhaustive survey of the fossilized legs of 50-plus species of carnivorous dinosaurs. Sizing up the legs of little dinos was easy. Getting a read on the gams of the big guys took a “ladder and a really long tape measure,” says study co-author Scott Persons, a graduate student at Canada’s University of Alberta.
Persons and his supervisor Philip Currie, also of the University of Alberta, analyzed the length of each animal’s lower leg – a key to swiftness – while taking into account the animal’s overall size. They found that some meat-eating dinos, though of massive proportions, had very long lower legs. Such leg dimensions allow an animal to cover more ground with each stride.
Among the standouts were the tyrannosaurs, a group that includes not only the famous Tyrannosaurus rex but also species like T. rex’s smaller cousin Gorgosaurus and its Asian look-alike Tarbosaurus, the researchers say in this week’s Scientific Reports.
“Tyrannosaurs as a group are the Radio City Rockettes of the meat-eating dinosaurs,” Persons says. “They’re super-leggy.” Leggiest of all was a lanky reptile that Persons thinks should be labeled Nanotyrannus, the species name some scientists give to a predator that looked like a small T. rex. Nanotyrannus, Persons says,was “the cheetah to T. rex’s lion.”
Not every scientist is convinced by the new findings. The idea behind the study is “really interesting,” says Kevin Middleton of the University of Missouri, and “they might be totally and completely right. But my view is we don’t know yet.” He’d like to see further analysis to verify the results.
Persons says his comparisons stand, and he also has another, more tangible piece of evidence for the swiftness of tyrannosaurs: the tracks of a tyrannosaur out for a walk, an extremely rare find. Persons and his colleagues describe the 66-million-year-old tracks, which meander across a stone slab in Wyoming, in a recent edition of Cretaceous Research.
The spacing of the footprints shows the animal was moving at a pace that for humans would be “a brisk walk … or maybe even a slow jog,” Persons said. That speed, he says, indicates a tyrannosaur would have no trouble catching up with something like a duckbill dinosaur, a plant-eater that would’ve made a nice tyrannosaur meal.
“If you had this dinosaur as a pet and you were walking it, you would get some pretty good exercise,” Snively says. Unlike velociraptor, “they definitely weren’t pokey.”
