400 million-year-old fish fossils reveal how life began moving onto land

The discoveries come from work led by teams in Australia and China. Their research expands on decades of investigation by Flinders University paleontologists studying fossils from the famous Gogo Formation in northern Western Australia, as well as collaborations with scientists at the Chinese Academy of Sciences.

Research on both living and fossil lungfish provides important anatomical evidence about how tetrapods evolved. Tetrapods are vertebrates with limbs, including humans, that eventually made the transition from water to life on land.

CT Scans Reveal New Details in Gogo Lungfish Fossil

A puzzling fossil from the Late Devonian Gogo Formation in WA has now been examined using advanced imaging techniques such as CT scanning and computed tomography. The findings were published in the Canadian Journal of Zoology.

Lead author Dr. Alice Clement from Flinders University's Palaeontology Lab says the work is gradually revealing the remarkable diversity of lungfish preserved at the Gogo fossil site. The research also revisits older specimens that were previously too damaged to study in detail.

One such fragmentary fossil has proven particularly valuable. It originated from what scientists consider Australia's first 'Great Barrier Reef,' a Devonian era reef system located in the Kimberley region of northern WA.

"The unusual specimen was so enigmatic, the authors who first described it in 2010 considered it could be a whole new type of fish never before seen in science," explains Dr. Clement, from the College of Science and Engineering.

"Using high-tech scanning, this time we were able to create comprehensive new digital images of the external and internal cranium, showcasing the complexity of the brain cavity of this fascinating lungfish," she says.

"In fact, we were also able to confirm that previous impressions were probably viewed upside down and back to front."

Coauthor Hannah Thiele worked with multiple museums and research facilities, including the Australian Nuclear Science and Technology Organisation (ANSTO), to analyze the fossil using advanced imaging tools.

"We were able to compare its most preserved inner ear area with other Gogo lungfish. This is an extra data point in the amazing collection of lungfish and early vertebrate species," she says.

"It adds to the wider understanding of the evolution of these earliest lobe-finned fishes, both in Gondwana and across the world."

Ancient Lungfish Skull From China Reveals Evolutionary Clues

A separate study published in the journal Current Biology focuses on another remarkable fossil discovery. Researchers reconstructed the skull of an early lungfish species known as Paleolophus, which lived in seas that once covered what is now southern China about 410 million years ago.

Flinders researcher Dr. Brian Choo collaborated with scientists at the Chinese Academy of Sciences, led by the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing. The team named the new fossil species Paleolophus yunnanensis ('Old crest from Yunnan').

"Paleolophus gives us an unprecedented look at a lungfish from a time between their earliest appearance and their great diversification a few million years later," says Dr. Choo, from the College of Science and Engineering at Flinders University.

"It was a time when the group was just starting to develop the distinctive feeding adaptations that would serve them for the remainder of the Devonian and onwards to the present day."

Lungfish represent an extremely ancient branch of the vertebrate family tree. Dr. Choo notes that they include species still alive today, such as the Australian lungfish from Queenland, which has long intrigued scientists because of its close evolutionary relationship to tetrapods, or vertebrates with limbs including humans.

"The exceptional lungfish skull unearthed in 410 million-year-old rocks in Yunnan gives us major insights into the rapid evolutionary diversification between the early-, mid- and late Devonian."

Dr. Choo adds that the fossil shows both similarities and differences when compared with the earliest and most primitive Diabolepis fossil from southern China, as well as other species such as Uranolophus from Wyoming in the US and Australia's Dipnorhynchus.

The China study was supported by the National Natural Science Foundation of China (92255301 and 42302005) and the Australian Research Council Discovery Project (DP 220100825).

The Gogo study was supported by funding from the Australian Research Council (ARC DP 220100825). Researchers acknowledge the Gooniyandi community and country for access to their land, fossils and knowledge.