Paleontologists in China have just published a series of four papers describing an astonishing set of fossils belonging to the earliest known jawed vertebrates, some of which lived as far as 440 million years ago. years – that is, tens of millions of years before the first terrestrial vertebrates appeared.
The fossils, unearthed at sites in China’s Chongqing and Guizhou regions, are exceptionally well-preserved. Among them are fossils showing an outer bony “armor” and several pairs of fin spines belonging to a new species of particular interest. These features have helped the researchers classify the new species, called Fanjingshan Renovata after a famous mountain and a UNESCO World Heritage Site in China, as an acanthodian, subterranean predator ancient shark-like sea.
Professor Zhu Min from the Institute of Vertebrate Paleontology and Human Paleontology (IVPP) of the Chinese Academy of Sciences said: “This is the oldest known jawed fish with anatomy. New data allow us to place Fanjingshan in the phylogenetic tree of early vertebrates and obtain essential information about the evolutionary steps leading to the origin of important vertebrate adaptations. such as functions, sensory systems, and paired appendages”.
The most striking thing about Fanjingshan is the skin on the shoulders. These spines are fused into a cluster of cutaneous scapula plates. It shed scales like bony fish, not cartilaginous fish like modern sharks, which suggests that 439 million years ago jawed vertebrates not only lived in the ocean, but also had a very high level of diversification. .
“This degree of hard tissue variation is unprecedented in chondrichthyans, a group that includes modern cartilaginous fish and their extinct ancestors,” said lead author Dr. Pham Qujing said.
Paleontologists also discovered Qianodus Dupis, a 439-million-year-old fish with the earliest teeth ever found; Shenacanthus vermiformis, a small cartilaginous fish 30 mm long, reveals important insights into the ancestors of sharks; and Xiushanosteus mirabilis, a small jawed, “armored” intermediate fish may reveal one of the key stages in vertebrate evolution.
Paleontologist Qiang Li of Qujing Normal University said: “Qianodus provides us with the first tangible evidence of teeth and jaw extensions from a critical early period in vertebrate evolution. living”.
This amazing set of fossils will help scientists shed light on a difficult period in vertebrate evolution. Judging from the DNA of living organisms, molecular biologists believe that the first jawless vertebrates appeared about 450 million years ago. Then a new line of jawed vertebrates appeared, which later evolved into the first bony fish, some of which moved their habitats to land to become vertebrates. The first terrestrial life was in the late Devonian – a period sometimes referred to as the “Age of the Fish” – a decisive moment in evolutionary history that would eventually lead to the emergence of amphibians and cows. reptiles, dinosaurs, birds and mammals, including us humans.
However, the existing fossil record does not provide enough evidence for this sophisticated stage of vertebrate evolution, no fossils or complete skeletons have been found in rocks of this age. more than 425 million years or so. But the new fossils help fill a large gap in the fossil record, showing that the skeletal anatomy of jawed vertebrates dates back to about 440 to 420 million years ago.
References: ZME; Nature; Zhihu