An investigation of a 415 million year-old fish skull strongly suggests that the last common ancestor of all jawed vertebrates, including humans, was not very shark-like. It adds further weight to the idea that sharks are not 'primitive'.
The fossil skull's external features meant it had always been thought to belong to the bony fishes (osteichthyans), a group which includes familiar fishes such as cod and tuna as well as all land-dwelling creatures with backbones. But when scientists from Oxford University and Imperial College London used X-ray CT scanning to look inside the skull they found the structure surrounding the brain was reminiscent of cartilaginous fishes (chondrichthyans) such as sharks and rays. The fish fossil's 'two faces' led to it being named Janusiscus after the double-faced Roman god Janus.
A report of the research is published in the journal Nature.
'This 415 million year-old fossil gives us an intriguing glimpse of the 'Age of Fishes', when modern groups of vertebrates were really beginning to take off in an evolutionary sense,' said Dr Matt Friedman of Oxford University's Department of Earth Sciences, an author of the report. 'It tells us that the ancestral jawed vertebrate probably doesn't fit into our existing categories.'
Story courtesy of the University of Oxford News and Information Office http://bit.ly/1KEIUis