Tuesday, 13 January 2015

Two-faced fish our last common ancestor

January 13, 2015

Chuck Bednar for redOrbit.com – Your Universe Online

The next time you call your spouse a “two-faced son-of-a-bitch,” just know that estimation is actually kind of realistic. Even for yourself.

A two-faced fish more than 400 million years old is likely the last common ancestor of all jawed vertebrates–including us–and provides additional evidence that sharks are not primitive creatures, as had long been assumed.

The skull of the creature, which was named Janusiscus after the two-faced Roman god Janus, possesses external features that led experts to believe that it had belonged in osteichthyans, the group that includes both bony fishes and all land-based creatures with backbones.

However, when scientists from Oxford University and Imperial College London used X-ray CT scanning to take a closer look inside the skull, they found that the structure surrounding its brain was actually closer to that of cartilaginous fishes (chondrichthyans) such as sharks and rays.

“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,” study author Dr. Matt Friedman of Oxford’s Department of Earth Sciences said in a statement. “It tells us that the ancestral jawed vertebrate probably doesn’t fit into our existing categories.”

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