A recent study published in the journal eLife has described a new armored dinosaur that lived during the Early Jurassic period on the territory of today’s China. Yuxisaurus kopchicki belongs to a group of dinosaurs called thyreophorans (“shield-bearers”), which include well-known creatures such as the Stegosaurus or the Ankylosaurus.
“My colleagues in China discovered this new armored dinosaur in Yunnan, southwest China, in rocks of Early Jurassic age dating to between 192-174 million years ago,” said study co-author Dr. Paul Barrett, a paleobiologist at the National History Museum in London.
“When we put the animal into an evolutionary analysis, it came out close to the common ancestry of stegosaurs and ankylosaurs. This helps to confirm that early armored dinosaurs were living in this region at this time. We know very little about the early history of herbivorous dinosaurs in China, so regionally this is a really important discovery.”
In the past, the highly diverse thyreophoran dinosaurs have largely been associated with rocks dating from the Late Jurassic to the Cretaceous periods (163 to 66 million years ago). Their fossils were mainly found in North America and Europe, making scientists assume that they lived mostly in the northern hemisphere. However, new discoveries of fossils in Morocco, Venezuela, and South Africa have shown that the spatial distribution of this group was much wider than initially thought.
“There are early armored dinosaurs starting to turn up more in the south,” explained Dr. Barrett. “There are two animals from about 200 million years ago from Venezuela and South Africa, that don’t have armor, but might be the earliest members of the group, showing what they looked like before they evolved armor.”
“If these animals were in the group, then it is likely the armored dinosaurs originated in the southern continents, but this idea is controversial. If they aren’t included in the group, then the origins are anchored in the northern hemisphere. At the moment, we’ve no way to choose between these alternatives.”
Yuxisaurus kopchicki has a stockier build and a distinctive arrangement of the armored plates that covered its back compared to other known early armored dinosaurs. Although it was primarily adapted for walking on four legs, the analysis of the fossils indicated that it was also able to walk on two legs. Its discovery sheds more light on the morphological diversity of the early thyreophorans and confirms their wide geographical spread.
Image Credit: ©Yu Chen