The ancient shark, which belongs to the family of daggernose sharks, was discovered among thousands of fossil fragments and teeth. The shark was dubbed Isogomphodon aikenensis after Aiken County where the species was found. The discovery was led by researchers Dave Cicimurri and Jim Knight of the South Carolina State Museum in Columbia. Mr Cicimurri is the current curator of the natural history museum and Mr Knight is his predecessor.
Aiken county sits on the southwest border of South Carolina, more than 100 miles (160km) from the Atlantic Ocean.
But 30 million years ago, the area would have been swamped with 20ft to 30ft (6.1m to 9.1m) of saltwater.
The conditions would have been perfect for prehistoric sharks, crocodiles and turtles to thrive.
The researchers presented their shark discovery in the peer-reviewed journal PaleoBios.
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Mr Knight told the Aiken Standard: "Anytime you can increase the knowledge of paleobiodiversity, it's exciting.
The shark typically only grows to about 4.5ft (1.5m) in length.
The prehistoric daggernose would have been similar in size at adulthood, reaching up to five feet (1.52m) in length.
The shark's teeth were very short and thin, just a little over a quarter of an inch tall, giving them a needle-like appearance.
According to Mr Cicimurri, the teeth would have been useless for tearing out chunks of flesh from the shark's prey.
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He said: “It probably ate little fish and grabbed them with its small needle-like teeth.
“Then it gulped them down. It chew its food. ”
The ancient daggernose is the first of its kind to be discovered on the planet.
But Mr Cicimurri said more fossils of the aikenensis are likely to be found in other parts of South Carolina, Georgia, Alabama and Mississippi.
He said: "I would be surprised if they popped up somewhere else."