The latest and oldest jaw tooth fossil discovered in Chongqing, providing evidence of the evolution

Ancient fish that lived 436 million years ago swam flexibly in the ancient ocean. This was restored by Chinese researchers based on a batch of fish fossil specimens discovered in the Chongqing Special Buried Fossil Library and the Guizhou Shiqian Fossil Library. scene. Among the newly discovered fossil specimens, scientific researchers found the oldest jawed tooth fossils in the world, and discovered a group of ancient fish fossils such as the oldest jawed miracle Xiushan fish, revealing the rise of jawed vertebrates. . On September 29, "Nature" magazine published four academic papers by the team as cover articles at the same time, focusing on this batch of research results on the origin and earliest evolution of gnathostomes.

Three-dimensional artistic reconstruction of the five newly discovered new genera and species of Silurian ancient fish, from From top to bottom: Shenacanthus vermiformis, Fanjingshania renovata, Qianodus duplicis, Tujiaaspis vividus and Xiushanosteus mirabilis). The ages of these fish fossils are 436 million and 439 million years ago respectively. (Produced by imitation stone technology)

Including humans, 99.8% of the existing vertebrates on the earth have jaws and are collectively called jawed vertebrates or gnathostomes. The emergence and rise of jawed animals is one of the most critical leaps in the history of vertebrate evolution, "from fish to man." However, from a global perspective, very few jawed fossils have been discovered during the Silurian Period, 440 million to 410 million years ago, and there is still a 35 million-year gap in the fossil record of early jawed creatures.

In the past ten years, Zhu Min's team, an academician of the Chinese Academy of Sciences and a researcher at the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, has visited more than 200 locations in my country's Silurian strata that may contain fish. The discovery of Chongqing's unique buried fossil library provides important evidence to fill this gap. The discovery process was quite a bit "lucky". In 2019, the scientific research team searched carefully along a newly built winding mountain road in Chongqing. They found a messy pile of rocks on the roadside with a casual tap of a geological hammer. The key to unlocking this "treasure trove" of fish fossils.

On a fossil slate that is only the size of a palm, dozens of fish fossils are clearly identifiable and vivid. "We never expected to find such complete and exquisite fossil specimens in such ancient strata." Zhu Min said with emotion.

Miracle Show Mountain Fish

Using high-precision CT scanning, fine three-dimensional reconstruction, scanning electron microscopy element analysis, full-light imaging and other technologies, scientific researchers discovered the miracle Xiushan fish from the fossils. This is the oldest jawed species currently discovered, and it will be the complete jawed species. The fossil record stretches back 11 million years, tracing the origins of several human body structures to fossil fish from 436 million years ago. The oldest well-preserved stickleback, the Creepyback stickleback, has also been discovered. This is the earliest associated well-preserved large fossil of a cartilaginous fish found in the world, proving that sharks evolved from "wearing armor" evolved from ancestors. The jawless armored fish Tujia fish provides key fossil evidence for the origin of paired appendages in vertebrates.

Zhu Min said that the Chongqing Special Buried Fossil Library is another world-class special buried fossil library discovered in my country after the Chengjiang Biota and the Jehol Biota and provides a large amount of key evidence for exploring important nodes in the evolution of the tree of life. It confirms that as late as 440 million years ago, various major groups of jawed animals were already thriving in South my country. By the late Silurian period, more diverse and larger species of gnathostomes appeared and began to spread across the globe, starting the process of fish landing and eventually evolving into humans.

Creepy stickleback

Important discoveries were also made in the Shiqian Fossil Library in Guizhou, hundreds of kilometers away. From fossil samples with a total weight of about 4 tons, scientific researchers have successively found 23 jaw tooth specimens with a length of only about 2.5 millimeters. They come from the dislocated Guizhou fish. This is the oldest jawed tooth fossil found worldwide, pushing back the earliest fossil record of teeth by 14 million years.

Now, the scientific research team's field work continues. Zhu Min said that detailed research on the two newly discovered fossil libraries will continue to change our understanding of the origin of jaws and the earliest evolution of gnathostomes. "This series of results is just the beginning. I believe there will continue to be surprises in the future." , we still need to continue to pursue and find.”

animal tags： fossil evolution fish sample