Kentucky Miner Finds Extinct Shark Jaw

Apr 11th, 2011 | By | Category: Science and Nature

Just when you thought it was safe to go back onto the land.

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Webster County Coal miner Jay Wright shows the jawbone of a 300-million-year-old shark which he found in the company’s mine in February. Photo by Mike Lynch. Courtesy of Kentucky Geological Survey

25-year-old miner Jay Wright was working 700 feet underground in Webster County, Kentucky this February when he made a surprising discovery. Experts later informed the puzzled miner that what he had found was the jawbone of a prehistoric shark.

Experts believe the jaw represents a shark of the genus Edestus. Edestus swam during the Pennsylvanian Epoch of the Carboniferous Period, when Kentucky was a wetland of “coal swamps.” At this time horsetails and ferns grew throughout a low swampy area in the Midwest United States surrounded by highlands. Flows of sediment from the east and periodic flooding from changing sea levels built up layers rich in tree stumps, branches, leaves, and spores. Over time, heat and pressure transformed these layers into coal deposits, forming the basis of modern coal mines like the one Wright was working in.

Fortunately for Wright, Edestus is long since extinct. Paleontologists believe that in prehistoric times, the largest species of Edestus, Edestus giganteus, grew as large as modern Great White Sharks. The shark’s mouth had only one row of teeth per jaw, making each jaw look like a log with a row of sawtooth shears sticking out of it, and its full mouth look like a pair of jagged scissors. Because of this appearance, Edestus giganteus is also known as the “scissor-tooth shark.”

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A close-up of the fossil shark shows the details of the teeth which have been well-preserved. Photo by Mike Lynch. Courtesy of Kentucky Geological Survey

From what paleontologists can tell, Edestus did not shed its teeth, unlike modern sharks. Instead, it apparently continued growing new teeth and gums near the back of the mouth, which periodically pushed the older teeth and gums forward, until they jutted from the shark’s mouth, reminiscent of the creature in Alien.

Shark skeletons are made of cartilage, which does not easily fossilize. Because of this, most shark fossils are limited to teeth, large fin spines, and tooth-like scales.Edestus giganteus is known only from a single set of teeth. It is rare to find a jaw fossil as large as the one Wright found, according to Jerry Weisenfluh, associate director of the Kentucky Geological Survey in Lexington.

The fossil is now on display at the University of Kentucky’s Mining and Minerals Research Building, located at 504 Rose Street in Lexington. The website of the University’s Kentucky Geological Survey department has a section with a collection of Kentucky shark fossils from the Pennsylvanian Epoch, including other Edestus specimens found in Kentucky mines over the years.

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