CHONGQING (CQNEWS) -- A new fish fossil has been found in Xiushan, Chongqing, with the highest level in the history of paleontological research in Chongqing. On March 3, Chongqing Municipal Bureau of Planning and Natural Resources held a media briefing to introduce the recent publication of the international academic journal Acta Geologica Sinica (English edition) on the discovery of a new type of fish fossil found in Xiushan, Chongqing, which is about 436 million years old.
It marks the first time a “family” has been established in the 152-year history of paleontological fossil research in Chongqing, and Binhai Yongdong fish is the oldest vertebrate fossil in the city, said Wei Guangbiao, Deputy Director of the Chongqing Institute of Geological Survey.

Without fins or active feeding, this 4-centimeter fish was a poor swimmer

On several palm-sized rocks brought by researchers from the Chongqing Institute of Geology and Mineral Resources, there are semicircular marks about 1.5cm long. The two eyes, middle dorsal pores and part of the middle transverse conduit veins are clearly visible.

“We were able to reconstruct what it looked like. It was about 4cm long, with a hard armor on its head. Its eyes were up and there were no fins.” Dr Chen Yang of the Chongqing Institute of Geology and Mineral Resources, the first author of the paper, said: “These fish have long been extinct, and these characteristics are quite different from today’s fish.”
According to the geological time division, Binhai Yongdong fish belongs to the Silurian period of Paleozoic, long before the emergence of dinosaurs. In the late Ordovician period before the Silurian, Marine life on the Earth experienced a great extinction event, “Almost 80% of Marine life after the Ordovician extinction, and the Binhai Yongdong fish is a new species appeared in the Silurian period. Because of their small size, they were at a disadvantage in the ocean,” Wei said.

“Binhai Yongdong fish had a flat abdomen”, Chen said. They didn’t have mandibles, so they had no ability to bite. They had a hole on their abdomen that allowed them to feed passively through water flow.”

According to Chen Yang’s analysis, Binhai Yongdong fish got used to the benthic life in their daily life, close to the bottom of the sea. Relying on the body swing left and right, they didn’t have strong swimming ability.
There are also “treasure” in this strata in Xiushan, and next a key laboratory is to be set up

“We found more than 20 armored fish heads at the excavation site.” Chen said the fossilized part is the head of the fish, which was discovered in 2020 in a strata dating back 436 million years in Yongdong Town, Xiushan Tujia and Miao Autonomous County.

The classification of the biological world can be divided into kingdom, phylum, class, order, family, genus and species according to the level of the hierarchy. The higher the position, the higher the biological classification level.
The newly named Binhai Yongdong fish is a brand-new “family” creature, “This is a transitional position between the Chinese armored fish and the ‘true armored fish cluster’, and this discovery also fills in the Chinese armored fish. The gap between the two important morphological types, the genus and the true armored fish cluster, makes the morphological evolution of the true armored fish clearer, and also adds a new high-level biological type to the world's ancient fish.” Chen Yang said.

This discovery fills a gap in the previous evolution of armored fish, and the study of its laws can also restore the early evolution of many vertebrates, which is crucial for the study of the early evolutionary stages of life.

A complete fauna is buried in this strata of Xiushan, which includes not only fish, but also many invertebrate fossils. There are also various types of jawed and jawless fish. Lu Yuchuan, Director of the Mining Protection Division of the Chongqing Municipal Planning and Natural Resources Bureau, said that the next step is to increase investment, incorporate Xiushan deep time geological work into the national plan, and promote the establishment of the Chongqing Key Laboratory of Major Geological Events and Deep Time Digital, and continue to dig deep into the research value of paleontological fossils.