Researchers at Flinders University have uncovered new details about an ancient Antarctic fish fossil closely related to the early ancestors of animals that eventually moved from water onto land more than 380 million years ago.
Using advanced neutron imaging technology, scientists examined the skull and braincase of Koharalepis jarviki, a large lobe-finned fish that lived during the Devonian Period, often known as the “Age of Fishes.”
The fossil was discovered in Antarctica’s Lashly Mountains region and remains the only known specimen of the species.
Researchers used non-destructive scanning methods to look inside the fossil without damaging it. The scans revealed internal structures hidden for hundreds of millions of years and provided new insight into the anatomy and evolution of ancient fish linked to the earliest four-limbed vertebrates.
“This precious fossil belongs to a group called the Canowindridae which highlights the ancient links between Australia and Antarctica,” said Alice Clement, a research fellow at Flinders University and co-author of the study published in Frontiers in Ecology and Evolution.
Researchers said Koharalepis belonged to the Canowindrid family, a group of fish that once lived across East Gondwana. Fossils from the family have been found in both Antarctica and Australia.
Scientists consider Canowindrids close relatives of the earliest tetrapods, the ancient vertebrates that later evolved into land animals.
Researchers studying a rare Antarctic fossil have uncovered new clues about how ancient fish evolved traits that later helped vertebrates move onto land more than 380 million years ago. pic.twitter.com/YitFnSfOU1
— Tom Marvolo Riddle (@tom_riddle2025) May 26, 2026
Lead author Corinne Mensforth said the fossil is especially important because it preserves the internal bones of the skull.
“We chose to focus on Koharalepis as it is the only fossil in the entire family to preserve the internal bones of the skull, which gives us valuable insights into its braincase and neuroanatomy,” Mensforth said.
The scans showed that the fish’s brain shared features with species associated with the evolutionary transition from aquatic life to life on land.
Researchers also identified adaptations linked to living near the water’s surface. These included openings on the top of the skull that may have allowed additional air intake, along with a light-sensitive organ connected to circadian rhythms.
Scientists said these features may have helped the animal survive in shallow freshwater environments where oxygen levels near the surface were higher.
The study also offered clues about the fish’s behavior. Researchers estimated Koharalepis grew to about 1 meter (3.3 feet) long and likely acted as an ambush predator that hunted smaller animals.
“With relatively small eyes it must have relied heavily on its other senses to capture its prey,” Mensforth said.
John Long, emeritus professor at Flinders University, said modern imaging technology allowed scientists to study the fossil’s internal anatomy in unprecedented detail.
The findings provide new evidence about how ancient lobe-finned fish adapted to changing environments during a critical stage in vertebrate evolution and how some species eventually developed traits that supported life on land.
