A hundred million years ago, a tiny baby stegosaurus hopped on its hind legs in today’s China.
This adorable toddler’s footprint the size of a cat from the Cretaceous Age was discovered in Xinjiang, an area of northwestern China. At just 2.25 inches (5.7 centimeters) in length, this is the smallest stegosaur print ever found, the authors reported March 3. in the magazine Palaios
The site where the small prints were found was also pockmarked with large footprints of stegosaurs – a group of herbivorous dinosaurs that included the genus Stegosaurus – which averaged about 11 inches (29 cm) long at the back foot and about 5.3 inches (12.7 cm) long at the front foot. There was a small footprint on the back with the distinctive three-toed shape of stegosaurs. It is not clear to which species the footprint belonged, but skeletal remains of a species called Wuerhosaurus homheni have been found nearby. This species is only known from fragmentary bones, but those scientists know it bore the iconic back plates that stegosaurs are famous for.
“Like the Stegosaurus, this little dinosaur probably had spines on its tail and bony plates along its back as an adult, ” says study co-author Anthony Ramilio, a researcher in the Dinosaur Lab at the University of Queensland, said in a statement
Possible small footprints of stegosaurs have been found before, but whether they were really stegosaur babies is controversial. Small traces have been found near Morrison, Colorado, in rocks from the Jurassic period (199 million to 145 million years ago), but not all paleontologists agree that these footprints are fossils. One of the co-authors of the new paper, paleontologist Marin Lockley, professor emeritus at the University of Colorado in Denver, argues that those prints are really just chunks of irregularly shaped mud embedded in sandstone.
Unlike the larger tracks at the Xinjiang site, the small track was not elongated. This was intriguing to researchers, as it suggests the baby stegosaurus may not have moved like its adult counterparts.
“Stegosaurs usually walked with their heels on the ground, just like humans do, but on all fours, leaving long footprints,” Romilio said. “The small track shows that this dinosaur moved with its heel off the ground, just like a bird or cat does today. We didn’t see these kind of shortened tracks before when dinosaurs walked on two legs.”
It’s possible that young stegosaurs walked on their hind legs and transitioned to 1.2 meters as they got bigger, said study co-author Lida Xing, a paleontologist at the Chinese University of Geosciences in Beijing.
“A full set of traces of these tiny footprints would give us the answer to this question, but unfortunately we only have one footprint,” Xing said in a statement.
Originally published on Live Science.