BEIJING, Dec. 17 (Xinhua) -- A team of Chinese scientists has announced the discovery of a new fossil lungfish species in southwest China's Yunnan Province, offering important insights into a crucial phase of early vertebrate evolution.

The finding, published in the journal Current Biology, was led by researchers from the Institute of Vertebrate Paleontology and Paleoanthropology (IVPP) of the Chinese Academy of Sciences.

Lungfishes, first appearing in the Devonian period, are the closest living relatives of tetrapods --four-limbed vertebrates -- making their evolutionary history particularly fascinating to scientists.

The research focuses on the species Paleolophus yunnanensis, which lived around 410 million years ago during the Early Devonian period.

The newly identified fossil is significant because it provides a long-sought morphological link between the earliest known lungfish, Diabolepis speratus -- also found in south China -- and later, more derived lungfish species, said Zhu Min, a professor from IVPP.

The fossil consists of a remarkably well-preserved three-dimensional skull, just 25 millimeters long. High-resolution CT scanning revealed that Paleolophus exhibits a mix of features. It retains primitive traits seen in Diabolepis, such as teeth on the upper lip, while also displaying characteristics common in early true lungfishes.

Unique adaptations include an unusually large nasal cavity and strongly developed jaw muscles, suggesting a possible diet of hard-shelled prey.

One of the most important anatomical details is a partially fused connection between the jaw structure and the braincase, which represents a key transitional stage in skull evolution.

Through phylogenetic analysis, the research team places Paleolophus at the base of the "Eudipnoi," a group comprising all lungfishes except the most primitive Diabolepis.

The study, utilizing precise geological dating, indicates that the major evolutionary transition from Diabolepis to true lungfishes occurred rapidly, within a window of just four million years between 416 and 412 million years ago, said Zhu.

The discovery also provides new biogeographical clues. Morphological similarities between Paleolophus and Early Devonian lungfishes from North America suggest that the ancient South China Plate and North American Plate were either connected or in close proximity during that period, aiding the dispersal of these animals.