148 million years ago, a baby sauropod – about the size of a pug dog – ran alongside an older dinosaur, perhaps its parent, in what is now the foothills near Denver, Colorado.
At the annual meeting of the Geological Society of America in Denver, scientists reported they found the baby’s ancient footprints outside the town of Morrison, Colorado. They suspect the dinosaur impressions – clear prints from the youngster and partial prints by the adult dinosaur accompanying it – were made by Apatosaurus, a giant, long-necked vegetarian sauropod once known as Brontosaurus.
The adult Apatosaurus is the largest dinosaur to be located in the Denver metro area, according to researchers, and are the length of three school buses and weighing in at the equivalent of eight Asian elephants.
The prints believed to have been made by the running Apatosaurus infant are smaller than a coffee mug, according to one of the discovers, Matthew Mossbrucker, director of the Morrison Natural History Museum in Boulder, Colorado.
“The distance between each step is two times wider than what we observe in walking tracks, indicating the animal was at a low-speed run,” Mossbrucker said. “I am not aware of any running sauropod tracks anywhere.”
One difference between the prints left by the infant and the adult dinosaur in the located prints is that the baby Apatosaurus impressions show only the hind paws, leading researchers to suspect either its hind paws eclipsed and removed the front paw track or it was running only on its hind paws. The tracks left by the adult dinosaur were made while it was walking – as opposed to the baby, who appears to have been scurrying to keep up – showed both the hind and front paws.
In an interview with Livescience magazine, Mossbrucker admitted “We’ve been arguing for more than a century as to whether or not sauropods could stand up on their back paws. Apparently they can, and the young can even run.”
He also noted that the baby dinosaur may not have technically met the definition of the word ‘running’, but if you were able to see the way it was moving while leaving these prints, most observers would say it was at least doing its own version of running.
Mossbruker clarified their definition by adding “In the end, we might have a baby sauropod that is running like a Basilisk lizard, a modern lizard that is mostly a quadroped, but when spooked it runs on its hindlegs,” Mossbrucker said.
Research is now being made to understand the biomechanics of Morrison’s sauropods and what a running baby sauropod might have looked like.
Photo via Matthew T. Mossbrucker / Museum of Natural History
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