A new trove of fossils has turned up in southern China (in Guizhou province) that sheds a little more light on the history of ancient jawed vertebrates, a group that includes humans. The fossil find dates from 439 to 436 million years ago and includes a large variety of never-before-seen species of small, toothy and bony fish.
Strange and ancient fish
As part of the rock layers known as China’s Rongxi Formation , the new fossil bed is full of amazing species that push back the dates of our earliest jawed animal ancestors by about 15 million years.
The mandible represents one of the success stories of the animal kingdom, as its development was a fundamental innovation in the evolution of vertebrates; it gave bony animals like us the ability to eat a far greater myriad of foods than the filter-feeding mouths of our ancestors allowed. This helped early animals with backbones move into new environments that continued to shape their anatomy, leading to the great diversity of body shapes and different behaviors we see in vertebrates today.
The fossils “help trace many structures of the human body back to ancient fish, about 440 million years ago , and fill in some key gaps in the evolution of ‘fish to human,'” explained the researchers from the Institute of Vertebrate Paleontology and Paleoanthropology. of the Chinese Academy of Sciences.
The first creatures to develop a backbone were fish, and they did so about 480 million years ago. Genetic analyzes have suggested that around 450 million years ago, those fish also developed jaws.
an armored shark
The most striking specimen in this treasure trove of fossils is Fanjingshania renovata , which was a somewhat strange shark , equipped with bony armor and paired fin spines. Not only is this an ancient fossil, but it has also allowed researchers to gain insights into anatomy far beyond what we can normally glean from such ancient fossils.
“This is the oldest jawed fish with known anatomy. The new data allowed us to place Fanjingshania on the family tree of early vertebrates and gain much-needed insight into the evolutionary steps that lead to the origin of important vertebrate adaptations, such as jaws.” , sensory systems and paired appendages,” says Zhu Min of the Chinese Academy of Sciences in Beijing in one of the published papers.
The creature’s fin spines are among the biggest finds, as the feature helped scientists pinpoint the new species’ position on the evolutionary tree of early vertebrates. The team also determined that fossilized bones from Fanjingshania reveal resorption and remodeling that are generally associated with skeletal development in bony fishes, including humans.
Another shark ancestor, Shenacanthus vermiformi, and a more ancient fish species , Xiushanosteus mirabilis , were also discovered, this time in a southern Chinese fossil bed dating to the same period called the Huixingshao Formation.
Another study describes the fossil teeth of another, previously unknown shark relative, called Qianodus duplicis, dating to about 439 million years ago, making them the oldest known teeth of any vertebrate. It had dental spirals that had to be studied with magnifying glasses and X-ray radiation due to its very small size (no more than 2.5 mm).
These fascinating new discoveries help fill in some important landmarks during our prehistoric evolutionary journey from fish to us.
Referencia: Y. Zhu et al. The oldest complete jawed vertebrates from the early Silurian of China. Nature. Vol. 609, September 29, 2022, p. 954. doi: 10.1038/s41586-022-05136-8.
Z. Gai et al. Galeaspid anatomy and the origin of vertebrate paired appendages. Nature. Vol. 609, September 29, 2022, p. 959. doi: 10.1038/s41586-022-04897-6.
M. Friedman. Fossils reveal the deep roots of jawed vertebrates. Nature. Vol. 609, September 29, 2022, p. 897. doi: 10.1038/d41586-022-02973-5.