Last updated May 31, 2018 at 9:30 am
3D anatomy of skull reveals previously unknown details.
An ancient Australian fossil found in NSW has helped clarify the origin of modern bony fishes and other vertebrates in prehistoric history.
Researchers from Flinders University in Adelaide have described the 3D anatomy of the skull of a 400-million year old fossil fish, Ligulalepis, revealing previously unknown details of the pattern of dermal skull bones, shape of the brain cavity and other soft tissue features, such as nerves and blood vessels.
The oldest known bony fish can be traced back to around 425 million years. All are part of a sub-group called lobe-finned fish. However, most modern bony fish are part of a different sub-group called ray-finned fish, which can only be confidently traced back about 390 million years.
The species Ligulalepis was once thought to represent the oldest ray-finned fish. However, subsequent studies have disputed its position in the evolutionary tree.
To address this, Dr Alice Clement and colleagues re-examined the original Ligulalepis skull fossil, alongside a newly discovered second skull fossil of the same species. Modern X-ray scanning techniques were used to produce detailed 3D models of both skulls and compare them to other prehistoric bony fish.
The experiments identified many previously unknown features of the Ligulalepis skull that suggest the species was not a ray-finned fish; rather, it existed just before bony fish split into two sub-groups (lobe-finned and ray-finned).
The analysis also suggests Ligulalepis was the species most closely related to another group of fish called psarolepids.
Overall, these findings clarify our understanding of the evolutionary tree of all vertebrates, including humans.
The paper published in the journal eLife.