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Earliest Evidence Of Jaws Discovered In 500M-Year-Old Fish Fossil

June 12, 2014
Image Caption: Illustration of Metaspriggina swimming. Credit: Drawing by Marianne Collins. © Conway Morris and Caron.

Brett Smith for redOrbit.com – Your Universe Online

Paleontologists working in the Canadian Rockies have uncovered the 500 million-year-old fossilized remains of a fish with jaw-like structures – the first time this feature has been seen so early in the fossil record, according to a new paper published in the journal Nature.

Fish fossils from the Cambrian are very uncommon and in most cases poorly preserved. The newly discovered species, dubbed Metaspriggina, also provides evidence for how the earliest vertebrates developed. The species would eventually lead to other fish species, but also dinosaurs and mammals, including humans.

“The detail in this Metaspriggina fossil is stunning,” said study author Simon Conway Morris, a paleobiologist at the University of Cambridge. “Even the eyes are beautifully preserved and clearly evident.”

[ Watch the Video: Metaspriggina swimcycle ]

The study team noted the fossil’s branchial arches – known to have played a major role in the evolution of vertebrates, including the origin of jaws – are what make it so unique. It had been thought that these structures only exist as a series of single arches, but Metaspriggina now indicates that they actually existed in couplets. The anterior-most pair of arches is also somewhat thicker than the rest, and this simple distinction could be the first step in an evolutionary shift that led to the appearance of the jaw, the researchers said.

“Once the jaws have developed, the whole world opens,” Morris said. “Having a hypothetical model swim into the fossil record like this is incredibly gratifying.”

“Obviously jawed fish came later, but this is like a starting post – everything is there and ready to go,” said study author Jean-Bernard Caron, a curator of invertebrate paleontology at the Royal Ontario Museum.

The fossils were retrieved from a number of locations, including the Burgess Shale location in Canada’s Rocky Mountains, one of the most productive Cambrian fossil deposits in the world. The new fossils are a part of the Cambrian ‘explosion’, a period of rapid evolution that began about 540 million years ago, when most significant animal phyla started.

“Not only is this a major new discovery, one that will play a key role in understanding our own origins, but Marble Canyon, the new Burgess Shale locality itself has fantastic potential for revealing key insights into the early evolution of many other animal groups during this crucial time in the history of life,” Caron noted.

During expeditions carried out by the Royal Ontario Museum in 2012, 44 new Burgess Shale fossils were gathered near Marble Canyon in Kootenay National Park in British Columbia. The study team used these fossils, along with more gathered from the eastern United States, to reclassify Metaspriggina as one of the first vertebrates.

“The Government of Canada is excited about this incredible fossil find,” noted David Wilks, Member of Canadian Parliament for the region where the fossil was found. “As an international leader in conservation and steward of the Burgess Shale, Parks Canada is pleased to provide its research partners with access to the fossils.

“Their remarkable discoveries inform the work we do to share this rich natural history through our popular guided hikes, and to protect this important Canadian heritage in a national park and UNESCO World Heritage Site,” he added.


Source: Brett Smith for redOrbit.com - Your Universe Online



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