Some of the world's most bizarre fossils - alien-like figure-eight water creatures - have surprisingly just been identified as distant relatives of humans, according to a new study.

Although they were first unearthed over 100 years ago, scientists are just beginning to understand "vetulicolians," blind water creatures dating back to 500 million years ago.

Given the strange figure eight shape of these "filter feeders," it's no wonder scientists were only just recently able to place them on the tree of life.

"Although not directly related to humans in the evolutionary line, we can confirm that these ancient water creatures are among our distant cousins," Dr. Diego Garcia-Bellido, lead author of the paper, said in a statement.

"They are close relatives of vertebrates - animals with backbones, such as ourselves," he added. "Vetulicolians have a long tail supported by a stiff rod. This rod resembles a notochord, which is the precursor of the backbone and is unique to vertebrates and their relatives."

These creatures are so bizarre, that even after they were first discovered in 1911, it took until 1997 for them to be identified as their own species, vetulicolians, let alone be found to be related to humans. They have since been discovered in countries all across the globe, such as Canada, Greenland, China and Australia.

But the fossils that led to the latest revelation came from those on Kangaroo Island off the coast of South Australia, which the researchers named Nesonektris (Greek for "Island Swimmer").

"Vetulicolians are further evidence that life was very rich in diversity during the Cambrian period, in some aspects more than it is today, with many extra branches on the evolutionary tree," Garcia-Bellido added.

"They were simple yet successful creatures, large in number and in distribution across the globe, and one of the first representatives of our cousins, which include sea squirts and salps."

The finding is described in further detail in the journal BMC Evolutionary Biology.