If you look far enough back on the human evolutionary chart, you'll find something you might not expect -- ancestors with shark-like heads (Photo: Creative Commons)

If you look far enough back on the human evolutionary chart, you'll find something you might not expect -- ancestors with shark-like heads, according to a new study, published Thursday in the journal Nature. New research on Acanthodes bronni, a fish from the Paleozoic era, revealed that it is the ancestor of all vertebrate life.

"The common ancestors of all jawed vertebrates today organized their heads in a way that resembled sharks," John Finarelli,, study coauthor and 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."

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Animals split into two groups approximately 420 million years ago, according to the study, and Acanthodes bronni may have been on the forefront of the split . One group, gnathostomes, meaning "jaw-mouths," includes tens of thousands of living vertebrate species, ranging from fish and sharks to birds, reptiles, mammals and humans, researchers said. The other, cartilaginous fish, includes sharks and rays.

"Unexpectedly, Acanthodes turns out to be the best view we have of conditions in the last common ancestor of bony fishes and sharks," Michael Coates, study coauthor and professor of organismal biology and anatomy at the University of Chicago, said in a statement. "Our work is telling us that the earliest bony fishes looked pretty much like sharks, and not vice versa. What we might think of as shark space is, in fact, general modern jawed vertebrate space."

Researchers conducted CT scans on the Acanthodes bronni and found that while studies have shown it to be similar to bony fish, it was related to modern sharks as well.

"For the first time, we could look inside the head of Acanthodes, and describe it within this whole new context," Coates said. "The more we looked at it, the more similarities we found with sharks."

Maureen Kearney, program director in National Science Foundation's Division of Environmental Biology, which helped fund the research, said the study sheds light into an important evolutionary divergence.

"This study is an example of the power of phylogenetics combined with the comparative morphology of living and fossil organisms," she said in a statement. ""It shows us important evolutionary transitions in the history of life, providing a new window into the sequence of evolutionary changes during early vertebrate evolution."