Distant Human Ancestor Had Shark Head

Peer far enough back in the human family lineage, and you'll find a fishy ancestor that looked surprisingly like a shark.

In fact, this now-extinct fish was among the first to split from sharks, whose bones are made of cartilage, to evolve into a line of tough-boned species that includes everything from bony fish to human beings. A new analysis finds that this controversial class of animals was more shark-like than expected.

"The common ancestors of all jawed vertebrates today organized their heads in a way that resembled sharks," study researcher John Finarelli, a vertebrate biologist at University College, Dublin, said in a statement. "Given what we now know about the interrelatedness of early fishes, these results tell us that while sharks retained these features, bony fishes moved away from such conditions."

Finarelli and his colleagues examined a fish called Acanthodes bronni, part of the acanthodian group of fish, which included the earliest vertebrate animals with jaws. A. bronni lived about 290 million years ago, during the Paleozoic period. The shark family and the bony fish families split about 460 million years ago. 


A. bronni left few traces besides its fossil scales and fin spines. But a few fossilized, fragmented skulls survived millions of years in the ground and now reside in museum collections. The researchers made silicone rubber casts of these fossils in order to reconstruct the anatomy of the fish's heads.


Read on:  http://www.livescience.com/20937-fishy-human-ancestor-shark.html