Researchers in China have identified a new species of fossil lungfish dating back more than 400 million years, offering rare insight into a critical stage in early vertebrate evolution.
The fossil was discovered in Early Devonian rock layers in Zhaotong, a city in southwest China’s Yunnan Province. The research team was led by Prof. Zhu Min of the Chinese Academy of Sciences, who is affiliated with the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing. The findings were published recently in the journal Current Biology.
The newly identified species, named Paleolophus yunnanensis, dates to about 410 million years ago. Researchers say it provides a long-missing anatomical link between the earliest confirmed lungfish species and later members of the group.
Why lungfishes matter in evolution
Lungfishes are the closest living relatives of tetrapods, the group that includes amphibians, reptiles, birds, and mammals. They first appeared during the Devonian Period, when vertebrates were beginning to diversify rapidly.
Although lungfishes were once widespread and varied, only three living genera survive today. Scientists consider them key to understanding how early vertebrates adapted to changing aquatic environments and eventually moved toward life on land.
A missing link in the fossil record
Until now, researchers had struggled to trace how early lungfishes evolved from primitive forms into the so-called “true” lungfishes. The gap centered on the transition from Diabolepis speratus, an early lungfish species previously found in southern China, to later lineages with more advanced skull structures.
According to the study, Paleolophus helps resolve that problem by preserving features from both stages of evolution.
A rare three-dimensional skull
The fossil includes the world’s first known three-dimensionally preserved lungfish skull from the Pragian Stage of the Early Devonian. The skull measures just 25 millimeters, or about 1 inch, in length.
Despite its small size, researchers say it preserves exceptional anatomical detail. This makes it one of the most informative lungfish fossils ever recovered from this period.
Mixed traits reveal evolutionary transition
High-resolution CT scans revealed that Paleolophus combines both primitive and advanced traits. It shares early features with Diabolepis, including teeth on the upper lip and a prominent pineal region in the skull.
At the same time, the fossil displays characteristics typical of early true lungfishes, marking it as a clear intermediate form in lungfish evolution.
Feeding adaptations and skull evolution
The fossil also shows signs of unique adaptation. Researchers identified an unusually large nasal cavity and strongly developed jaw muscles. These traits suggest the fish may have fed on hard-shelled prey that required a powerful bite.
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One of the most significant findings lies in the structure of the skull itself. The palatoquadrate–neurocranial region is partially fused, capturing a rare transitional stage in skull evolution.
Early sarcopterygians had a primitive “dual articulation” skull, while later lungfishes evolved an autostylic skull in which the upper jaw is fully fused to the braincase. Paleolophus falls between these two conditions.
Rapid diversification in early lungfishes
Using CT data and phylogenetic analysis, the research team placed Paleolophus at the base of Eudipnoi, a newly refined taxonomic group that includes all lungfishes except Diabolepis.
Precise geological dating shows the evolutionary transition from Diabolepis to true lungfishes occurred over just 4 million years, between about 416 million and 412 million years ago. Researchers describe this as a brief but intense period of diversification.
Clues to ancient geography
The study also offers new insights into early lungfish distribution. Researchers noted close anatomical similarities between Paleolophus and Early Devonian lungfish fossils found in North America.
These similarities suggest the South China Plate and the North American Plate were either connected or geographically close during the Early Devonian. Scientists say this proximity may have allowed early lungfishes to spread across regions that are now separated by vast oceans.
A clearer picture of early vertebrate life
Researchers say the discovery strengthens southern China’s importance as a key region for studying early vertebrate evolution. More broadly, the fossil helps clarify how ancient fishes developed key traits that later supported the transition toward life beyond water.
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