Researchers in China have discovered two ancient fish fossils, dating back over 400 million years, which are reported to fill a significant gap in the evolutionary understanding of vertebrates, including humans.
The discoveries were made by a research team from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences (CAS) after more than a decade of fieldwork and laboratory research.
Key Discoveries
Eosteus chongqingensis: The Earliest Complete Bony Fish
One fossil, named Eosteus chongqingensis, was found in Chongqing Municipality. This creature, measuring approximately 3 cm, is identified as the world's earliest known complete bony fish fossil, dating back 436 million years. Its discovery indicates that core bony fish characteristics emerged 10 million years earlier than previously understood.
Megamastax amblyodus: Silurian's Largest Vertebrate
The second fossil, Megamastax amblyodus, was discovered in Qujing, Yunnan Province. Dating to approximately 423 million years ago, this fish exceeded one meter in length, making it the largest known vertebrate of the Silurian Period. Advanced imaging technology revealed its complete three-dimensional head structure, including double-rowed teeth with internal sharp spines.
Evolutionary Significance
Filling the Evolutionary Gap
Both Eosteus chongqingensis and Megamastax amblyodus are classified within the bony fish stem group, representing primitive types that existed prior to the divergence of ray-finned and lobe-finned fishes. Bony fishes form the main trunk of the vertebrate tree of life, with ray-finned fishes evolving into most modern fish species and a lineage of lobe-finned fishes eventually venturing onto land to become all tetrapods, including humans.
According to Zhu Min, an academician of CAS from the IVPP, information on these primitive bony fishes was previously scarce, making it difficult to determine the morphology of the most recent common ancestor of ray-finned and lobe-finned fishes.
These new findings are stated to illuminate the morphology of this common ancestor and enrich the understanding of the early radiation of jawed vertebrates. They also clarify the evolutionary trajectory of jaws and teeth in early bony fishes.
A Crucial Point in Vertebrate Development
The researchers state that these fossils represent a crucial point in the evolutionary path from fish to human, demonstrating that bony fishes had diversified by that period, establishing a foundation for the eventual transition to land and the subsequent evolution of diverse vertebrate life on Earth.