Not all prehistoric creatures were monsters, but this one was.

An ancient fossil long-kept in a Canadian museum turned out to be a previously undiscovered primordial monster worm with scary, snapping jaws, a new study revealed.

The creature, which swam Earth's ancient seas about 400 million years ago, has been named after a famous metal musician as well as the scientist who collected the sample at least two decades ago.

Metal Worm

In the study, scientists from the United Kingdom, Sweden, and Canada examined an ancient fossil that has been stored at the Royal Ontario Museum for 20 years, after scientist Derek Armstrong collected samples at a remote exposure in Ontario in 1994.

Now, a few years later, a team from University of Bristol, Lund University, and the museum officially identified the specimen as the remains of an extinct bristle worm and named it Websteroprion armstrongi. The creature was named in honor of Armstrong, who discovered the fossil, and Alex Webster, a "monstrous bass player" from Death Metal band Cannibal Corpse.

Luke Parry, a scientist from University of Bristol and a co-author of the study, said it seemed apt to name the creature after Webster, whom he has admired.

"Alex Webster just seemed like the perfect fit for a giant worm with saw-like jaws," said Parry.

David Rudkin, an assistant curator at the Royal Ontario Museum, said the fossil is an exceptional example of the value of searching in unexplored areas for finding new things, as well as the importance of investigating museum collections to scrutinize overlooked gems.

Gigantism In Animals

Although the fossil investigated by scientists only contained the species' jaws, which were at least 1 to 2 centimeters long (0.39 to 0.79 inches), researchers believe the body of the monster worm was more than 1 meter long (3 feet). Most fossil samples typically require a microscope to be seen, but studying W. armstrongi presented a different case.

In fact, W. armstrongi possessed the biggest jaws ever recorded in this type of animal, with its jaws visible to the naked eye.

"We can tell from the shape of the jaws that it is closely related to other similar [modern-day] worms that can grow to large sizes," said Parry.

Scientists compare this ancient monster worm to Bobbit worms, part of the giant eunicid species, which are fierce and opportunistic predators that use their jaws to seize fish, squid, and octopuses and drag them to burrows.

Mats Eriksson, a researcher from Lund University and the lead author of the study, said such gigantism in animals is ecologically important because of its competitive dominance. However, gigantism is still poorly understood among marine worms, he said.

In this case, W. armstrongi demonstrates a unique polychaete gigantism in the Paleozoic era. Furthermore, researchers added that the fossil shows that gigantism in species with jaws was limited to a certain evolutionary clade within the eunicid species, and has evolved over time.

Details of the study are issued in the journal Scientific Reports.