An underwater alien fossil which lived 300 million years ago, has baffled scientists to this day. Numerous studies have already been undertaken to reveal its true origin and its anatomical function, but none has been successful in fully explaining its existence. According to experts, the most recent research that identifies the creature as a blood-sucking fish is actually flawed.

Terrifying with its eyes on the end of a long thin stalk, and teeth at the end of a long narrow trunk, the alien-looking creature, dubbed as the Tully Monster, is perhaps the strangest creature to have ever lived. Since its discovery almost 60 years ago, the ancient fossil is still a complete mystery, researchers claim. Last year, researchers claimed to have solved the mystery, concluding their findings that the Tully Monster was a Lamprey fish that sucks the blood of its prey using its sucker.

However, experts at the University of Pennsylvania say the mystery persists. Their latest research reveals that the classification of the underwater alien is wrong. This development has reopened the Tully Monster mystery, The Sun reports. "This animal doesn't fit easy classification because it's so weird," lead-researcher, Professor Sallan, a paleontologist at the University of Pennsylvania, says. There are disagreements among fossil experts about its anatomical use.

Professor Sallan adds that most of his colleagues don't agree that the Tully monster could be a fish. Known to scientists as 'Tullimonstrum gregarium', the mysterious monster has been known since the 1950s when the first fossils were found. The ancient remains were first found in Mazon Creek fossil beds in Central Illinois, the Daily Mail reports.

The animal is difficult to classify because it's so weird, Professor Sallan explains. The flaw of recent researches is its inability to conclusively identify the creature as a vertebrae. For now, the classification and origin of the underwater alien fossil remains a mystery.