Big news arrived this week from a smallish stegosaur discovered in Asia, which researchers say is the oldest ever found in the region and possibly even the oldest in the world. Stretching just shy of 3 meters (9.8 feet), the newly named Bashanosaurus primitivus was strutting around roughly 160 million years ago.
The specimen’s significance, discussed in the Journal of Vertebrate Paleontology, is reflected in its name, with “Bashan” paying homage to the ancient name for the area of Chongqing, China, where it was found while “primitivus” is Latin for first. The latter of these highlights B. primitivus’s place right at the start of stegosaurus’s time on Earth.
“Our analysis of [B. primitivus’s place in the stegosaurus] family tree indicates that it is one of the earliest-diverging stegosaurs along with the Chongqing Lizard (Chungkingosaurus) and Huayangosaurus,” said lead researcher Dr Dai Hui, from Chongqing Bureau of Geological and Mineral Resource Exploration and Development, in a statement.
“These were all unearthed from the Middle to Late Jurassic Shaximiao Formation in China, suggesting that stegosaurs might have originated in Asia.”
Stegosaurs are among the most recognizable of dinosaurs thanks to the enormous armored plates that lined their spines. The remains B. primitivus’s discovery was built on included several of these plates, as well as bones from the back, shoulder, thigh, feet, and ribs.
What makes them so special is they date back to the Bajocian stage of the Middle Jurassic period, which occurred between 170.3 million and 168.3 million years ago, planting the species at a much earlier stage than most known stegosaurs.
The new dinosaur, which roamed the planet 168 million years ago, plays a part in uncovering how the stegosaurs evolved – of which, to this day, little is known.
It had markedly different features from other Mid-Jurassic stegosaurs including thick-based armor plates, bony thigh projections, and less developed shoulder blades which made it easier for the researchers to establish it as a new species. It also plants it more firmly at an early stage of stegosaurs’ evolution, supported by its similarities with some of the first armored dinosaurs dating back a further 20 million years.
“All these features are clues to [Bashanosaurus primitivus]’s’ place on the dinosaur family tree”, Hui concluded. “Bashanosaurus can be distinguished from other Middle Jurassic stegosaurs, and clearly represents a new species.”
In other prehistoric species news, a contentious paper was published this week that posits the “tyrant lizard king” Tyrannosaurus rex might have been three species instead of just one.