The tiny-headed stegosaurus with long tail spikes is one of the oldest of its kind

An illustration of the Volkswagen Beetle-sized Stegosaurus Bashanosaurus primitivus. (Image credit: Banana Art Studio)

The remains of a newly discovered stegosaurus with huge back plates, long tail spikes and a tiny head belong to one of the oldest such dinosaurs on record, according to a new study.

armored vehicles dinosaura new species called Bashanosaurus primitivuslived in the Middle Jurassic period (174.1 million to 163.5 million years ago) in what is now China. As one of the oldest stegosaurs on record, its discovery adds further evidence that these plant-eating dinosaurs may have originated in Asia, the researchers said.

Bashanosaurus primitivus is one of the first records of Stegosauria in the world so far,” the study’s co-lead researcher Ning Li, a scientist at the Laboratory for Protection and Research of the geographical heritage of Chongqing in China.

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The discovery of B. primitive‘ The remains began in 2015, when a shepherd named Zheng Zhou found a bone-shaped stone in Chongqing, southeast China. He told Li’s lab, which confirmed the “stone” was actually a dinosaur fossil. After excavating the Laojun village site for two years, Li and his colleagues found a remarkable mishmash of dinosaur bones – around 5,000 in all – which included the fossils belonging to the newly described stegosaurus.

“It’s like where I work at Dinosaur National Monument [in Utah]where they get many kinds of dinosaurs preserved in a gigantic bed of bones,” said ReBecca Hunt-Foster, a paleontologist at Dinosaur National Monument who was not involved in the study. “I’m curious to see what else they get from this site? »

Part of the fossil wall that paleontologists excavated in the village of Laojun, China. (Image credit: Courtesy of Ning Li)

The team named the 168 million year old herbivorous beast Bashanosaurus for “Bashan”, the old name of Chongqing, and primitive, which is Latin for “first”. During his life, B. primitive was over 9 feet (2.8 meters) long from snout to tail. It’s a bit smaller than later stegosaurs, Hunt-Foster noted.

Based on sediment analysis where B. primitive was found, the team determined that the stegosaurus lived in a delta near a shallow lake during a scorching drought, Li said.

The ancient beast joins a growing number of known stegosaurs. These dinosaurs, of which there are 14 known species, lived on all continents except Antarctica and Australia. The new species has some differences from its relatives, including the bases of its armor plates, which are thicker and curved outward, unlike the plates on its later relatives’ backs, Li said.

Bashanosaurus can be distinguished from other Middle Jurassic stegosaurs, and is clearly a new species,” Li said. “However, it has similarities to some of the earliest armored dinosaurs, which are over 20 million years old.”

A handful of fossils discovered by paleontologists at the Laojun village site in China. (Image credit: Courtesy of Ning Li)

The other earliest known stegosaurs, chungkingosaurus (Chongqing “lizard”) and Huayangosaurus (Huayang “lizard”), are also from the Middle to Late Jurassic Shaximiao Formation in China, which Li says could imply that stegosaurs originated in Asia.

The new spiked dinosaur “is a pretty critical animal for understanding stegosaur evolution,” said Andrew Farke, director of the Raymond M. Alf Museum of Paleontology in Claremont, Calif., who was not involved in the new study. . “Even though this group is so iconic, we still have a lot to learn about their early evolution.” Studying B. primitivescientists can learn how much early stegosaurs looked — or didn’t — look like their better-known descendants, he added.

As to whether stegosaurs originated in Asia, that’s still relevant. “There is also an early stegosaurus of about the same age known from South America, so I suspect the overall picture may have been quite convoluted,” Farke told Live Science in an email. “We just don’t have the fossils yet.”

The study was published online Thursday, March 3 in the Journal of Vertebrate Paleontology.

Originally posted on Live Science.