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419 million year-old fish fossil may reveal origins of the human jaw

As a kid, I used to ponder the origins of my unusually square jawline while looking in the bathroom mirror. After reading this story in Nature News, I wonder if I should have pondered my jaw’s origins while walking the halls of the nearest aquarium instead. Researchers from the Chinese Academy of Sciences in Beijing discovered a well-preserved 419 million year-old fossil that suggests the armor-plated fish, called Entelognathus primordialis, may be the earliest known species with a jaw like ours.

From Nature News:

Entelognathus primordialis is a new addition to the placoderms, a class of armour-plated fishes that lived from about 430 million to 360 million years ago. Like most vertebrates, including mammals, placoderms had a bony skull and jaw, but most of them had simple beak-like jaws built out of bone plates.

If you're stifling a yawn, consider this: Researchers have seen fossils of this fish species before, but they were in less than pristine shape. Based on these fossils, most scientists concluded that this species was unrelated to humans.

Now, the discovery of this well-preserved fossil described in the journal Nature by paleontologist Min Zhu, PhD, and his team may upend this view of our family tree. Eliot Barford of Nature News explains:

There is a serious possibility that the modern bony visage originated with E. primordialis’s ancestors. This would mean that humans look more like the last common ancestor of living jawed vertebrates than we thought, and that sharks are less primitive than palaeontologists assumed, having done away with their bones as an adaptation.

However, the rearranged family tree is not yet quite conclusive, write the authors of a related News & Views article. There remains a chance that E. primordialis evolved its jaw independently from the bony fish, so that we did not inherit it, and the resemblance is an illusion.

Holly MacCormick is a writing intern in the medical school’s Office of Communication & Public Affairs. She is a graduate student in ecology and evolutionary biology at University of California-Santa Cruz.

Previously: Stanford study investigates our most-recent common ancestorsRecent shared ancestry between Southern Europe and North Africa identified by Stanford researchers and Stanford engineer studies bones that aid hearing
Photo by cuatrok77

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