New evidence of Chinese origin! The oldest "star dinosaur" appeared in Chongqing

Author: Zhang Qingdan

In the world of dinosaurs, Stegosaurus is a peculiar dinosaur. It has two rows of upright bone plates along its spine from the front of its neck to its tail, and uses 2 to 4 pairs of large bone spurs at the end of its tail as weapons. Its head is only as big as a watermelon, and it is a vegetarian, making it a well-known star dinosaur.

Dinosaur fossils are important codes for people to understand how dinosaurs lived and became extinct billions of years ago.

However, there are not many stegosaurus fossils found worldwide, and most of the skeletons are in poor completeness, so the relationships between stegosaurus and their early evolution still need further study.

Recently, a research paper on the origin of stegosaurus was published in the Journal of Vertebrate Paleontology.

Researchers discovered the oldest stegosaurus fossil in Asia at the Yunyang dinosaur fauna in Chongqing, and named this stegosaurus Yuanshi Bashanosaurus.

This study adds new evidence that stegosaurus originated in Asia and also solves many mysteries about stegosaurus.

The first new genus and species of dinosaur from the Shaximiao Formation in Yunyang

One day in January 2015, villagers in Laojun Village, Pu'an Township, Yunyang County, Chongqing City found a large stone in the field that looked like a bone, and they immediately reported it. The Chongqing Municipal Planning and Natural Resources Bureau quickly organized experts to investigate and determined that it was a dinosaur fossil.

The expert team conducted an investigation around the bone and discovered that there were huge resources of dinosaur fossils here, buried with rich secrets.

Even more incredible is that through the investigation of fossil resources, researchers have discovered that dinosaur fossils have been exposed in an area of ​​18.2 kilometers across four townships, including 17 fossil layers. In 2019, an expert group headed by Zhou Zhonghe, an academician of the Chinese Academy of Sciences and a researcher at the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, concluded that the Chongqing Yunyang dinosaur fauna has the characteristics of a wide distribution range, a long time span, and rich species. It is a world-class concentrated burial site of dinosaur fossils with very high scientific value and development and utilization value.

In order to explore these precious fossil resources, the 208 Geological Relics Protection Institute of Chongqing Municipal Bureau of Geology and Mineral Resources has carried out relevant research work.

"According to the division of exposed strata, the stegosaurus fossils we studied this time came from the lower strata of the Shaximiao Formation. It is the first new genus and species of dinosaur in the Shaximiao Formation, and also the fourth new genus and species of dinosaur named in the Yunyang dinosaur fauna in Chongqing." Li Ning, co-first author of the paper and researcher at the 208 Institute of Geological Relics Protection of the Chongqing Municipal Bureau of Geology and Mineral Resources, told China Science Daily.

Dinosaurs are divided into two major categories: saurischians and ornithischians. Saurischians are divided into theropods and sauropods; ornithischians can be divided into stegosaurus, ornithopods, ankylosaurs, ceratosaurus and pachycephalosaurs. The Yuanshi Bashanosaurus named this time belongs to the stegosaurus among the ornithischians.

The name was inspired by a line from a poem by Li Shangyin: "Night rains in Bashan swell the autumn pond." "'Bashan' represents Chongqing, and 'Yuanshi' means that this newly named stegosaurus represents the most basic or primitive group of stegosaurus," said Li Ning.

Important evidence for the Chinese origin of stegosaurus

In the late Early Jurassic and Middle Jurassic, a global marine transgression occurred on the Earth, and shallow seas invaded the interior of many continents. The result of this marine transgression was a scarcity of Early and Middle Jurassic terrestrial sedimentary strata.

During this period, very limited dinosaur fossils were discovered in the world, and related dinosaur research was almost blank.

In 1874, Stegosaurus fossils were first discovered in Britain.

Since then, more and more Stegosaurus fossils have been discovered on every continent in the world except Oceania and Antarctica.

Dinosaur scholars all over the world are trying to find out when Stegosaurus appeared on Earth. There has always been a lot of controversy about its true origin.

"The oldest stegosaurus fossils found before are located in Morocco, Africa, so some scholars believe that stegosaurus originated in Africa. However, the Taibai Huayangosaurus in Zigong, Sichuan, my country is also a very primitive stegosaurus species, so some scholars believe that stegosaurus originated in China."

Dai Hui, co-first author of the paper and senior engineer of the 208 Geological Relics Protection Institute of Chongqing Bureau of Geology and Mineral Resources, told China Science Daily.

Bone morphology is the most basic and most commonly used research method for studying dinosaur fossils and many vertebrate fossils.

The fossil materials of Yuanshi Bashansaurus discovered this time include skeletal fossils of the scapula, coracoid bone, dorsal vertebrae, caudal vertebrae, femur, tibia, fibula, metatarsal bones, xiphoid plate, and tail spine.

Li Ning introduced that from the morphological characteristics, Yuanshi Bashansaurus has obvious differences from other stegosaurus. Its morphological characteristics are similar to those of early armored dinosaurs (the ancestors of stegosaurus) and other early stegosaurus (such as Taibai Huayangsaurus). It can be seen that Yuanshi Bashansaurus belongs to the early stegosaurus group.

The results of stratigraphic dating show that Yuanshi Bashanosaurus lived 169 million years ago, earlier than Taibai Huayangosaurus and comparable in age to the oldest stegosaurus fossil discovered in Morocco, with richer and more complete materials.

Therefore, Yuanshi Bashanosaurus is the oldest stegosaurus in Asia and one of the oldest stegosaurus in the world.

There are 17 species of Stegosaurus recognized worldwide, of which China accounts for about 40%. The discovery of Yuanshi Bashanosaurus not only enriches the types of Chinese Stegosaurus, but also makes China the sole source of half of the world's four oldest Stegosaurus species.

"Therefore, whether in terms of the number of Stegosaurus species or the degree of antiquity, the discovery of Yuanshi Bashanosaurus provides new evidence that stegosaurus originated in Asia, and also enhances the global status of Chongqing's stegosaurus community," said Li Ning.

This research has also been recognized by world-renowned stegosaurus research experts.

"The discovery of Yuanshi Bashanosaurus adds to the evidence that stegosaurus originated in the early Middle Jurassic (or even Early Jurassic). At the same time, Yuanshi Bashanosaurus is also one of the earliest known ornithischian dinosaurs," said Dr. Susannah Maidment, a paleontologist at the Natural History Museum in the UK and one of the authors of the paper.

Exploring the causes of fossil accumulation

The Chongqing Yunyang Dinosaur Fauna is the most densely distributed "treasure trove" of dinosaur fossils in Chongqing, with a rich variety of dinosaur fossils. Why are there so many dinosaur fossils in Yunyang?

"Research has found that there are many strata of dinosaur fossils in Yunyang, which means that dinosaurs did not exist here at a certain period, but have lived here for millions of years. This shows that about 180 million to 160 million years ago, the ancient environment, vegetation and water sources in Yunyang were very suitable for the survival of dinosaurs," Dai Hui explained.

"According to our research, there is a mud volcano in the Yunyang Fossil Area 1, and a disaster has occurred there. High-temperature mud and toxic gases were ejected at the same time, leading to the death of a group of dinosaurs, so there are a large number of dinosaur fossils buried here." Dai Hui said.

The research on dinosaur fossils is a huge, relatively boring and time-consuming project, but in Dai Hui's view, this work is very meaningful.

"Fossils are like a 'magic mirror'. They can take us 'through' the age of dinosaurs and help us understand the appearance and environment of dinosaurs. The discovery of more fossils will only bring us closer to the truth, which makes us very motivated."

Paleontological research can help humans explore the origin and evolution of life and construct the history of the evolution of life on Earth.

"We can understand the boundaries of nature from paleontological research and exploration, so that we can better understand the earth on which we depend for survival and create a better future for human life," said Li Ning.

Related paper information:

https://doi.org/10.1080/02724634.2021.1995737

China Science Daily (2022-03-10 Page 1 News original title: "169 million years old! Asia's oldest stegosaurus discovered in Chongqing")

Editor | Zhao Lu

Typesetting | Guo Gang

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