A mysterious worm-like creature has puzzled scientists since fossil specimens of it were discovered in Canada in the 1970s.

Called Hallucigenia sparsa, the spiny, multi-legged animal has been found to be related to modern-day velvet worms, according to a new study published in Nature.

The creature is so unusual that scientists didn't realize for decades that they were actually looking at the specimen "upside down and back to front," a Forbes contributor reported.

"Hallucigenia had a row of rigid spines along its back, and seven or eight pairs of legs ending in claws," the researchers described in the study. "The animals were between five and 35 millimeters [.20 and 1.3 inches] in length, and lived on the floor of the Cambrian oceans."

The new report links Hallucigenia to velvet worms through the animal's peculiar cuticles, which are placed inside one another like the layers of an onion--or a velvet worm's jaw, the Washington Post reported.

"The peculiar claws of Hallucigenia are a smoking gun that solves a long and heated debate in evolutionary biology," said lead researcher Martin Smith of the University of Cambridge, as quoted by Forbes.

Discovered in Canada's Rocky Mountains as well as in China and other sites, the fossils have previously been misidentified as annelid worms, which are related to modern earthworms and leeches.

Scientists have since placed the unique worm with legs modified for eating in the Cambrian Explosion era, when major animal groups are included in the fossil record.

"It's often thought that modern animal groups arose fully formed during the Cambrian Explosion," Smith, who is a professor at the university's Department of Earth Sciences, said in a statement quoted by the Post. "But evolution is a gradual process: today's complex anatomies emerged step by step, one feature at a time."

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