Unusual Fossil of a Fish With Anal Fins Offers New Insight into Evolution

While conducting a study on the Euphanerops fossils in Quebec, Canada, Dr Robert Sansom from the Faculty of Life Sciences, Manchester, came across a paired fin of Euphanerops, a fossil jawless fish found some 370 million years ago.

This makes the fish the first vertebrate to have paired appendages such as fins, arms or legs. With the help of 3D scans of the fossil and comparison of specimens preserved in different conditions, Dr Sansom traced that the fish had two fan-shaped fins positioned on the right and left.

"Euphanerops is unique because its anal fin is paired meaning there is one fin on each side of the fish. Up until now anal fins have only been seen on jawed fish where they are unpaired and this is true of both extinct and modern fish." Dr Sansom said in a press statement.

He says that the period of Euphanerops was crucial as it goes back to the evolutionary split between the jawed and jawless fish. This represents the important stage in the evolution of paired appendages

The researchers don't have a clear explanation as to why fins are positioned so far back on the fish. They don't know what advantage the fish receives with this.

This finding shows that there was some degree of developmental and evolutionary experimentation on fish. And this may help throw light on the evolution and diversification of vertebrate appendages.

The study was published in the Royal Society's Journal Biology Letters.