The long-standing mystery of Palaeospondylus is solved using X-ray.

In 1890, Palaeospondylus gunni was discovered in Scotland, and its phylogenetics was a mystery ever since. This tiny eel-looking creature is said to be around for more than 390 million years ago.

There are no teeth or dermal bones in its fossil record, making it a mysterious fish-like fossil vertebrate. Researchers have been unable to solve it since its discovery in 1890.

Scientists used synchrotron radiation X-ray micro-computed tomography to analyze Palaeospondylus gunni cranial skeletons at the histological level.

A cartilaginous skeleton and the lack of paired appendages indicate that Palaeospondylus gunni belongs to Sarcopterygii, a group of lobe-finned fishes.

According to Dr. Hu, the lead author, it is still difficult to determine exactly what the animal was.

This discovery could provide a wealth of information about four-limbed animals' evolutionary history and morphological features.

Dr. Hu is of the view that this new information, comprising of a long-last joint investigation of scientists around that globe, is required for solving the mystery behind Palaeospondylus gunni.