Story highlights Mystery around identity of deep-sea creature that resembles a purple sock has been solved

The Xenoturbella flatworm is an animal that belongs to an early branch of life

(CNN) A new species of deep-sea creature that resembles a discarded purple sock has been identified as an early form of life in a discovery that will help scientists understand how animals have evolved over time.

The very simple creature, Xenoturbella, has no brain, gills, eyes, or reproductive organs, and only one opening through which food goes in and waste goes out. And although the animal was first described in 1949, its peculiar biology left scientists baffled for decades.

One of the lead authors of the study that finally identified it -- published in the journal Nature -- said previous research had led scientists to believe that the creatures had evolved from more complex organisms.

"What we've shown is that, no, they probably always were simple," said Nerida Wilson, a research scientist with the Western Australian Museum. "So our little guys are simple because they are one of the early branches of the tree of life."

The deep sea worm, pictured here on a U.S. dime, sits at the bottom of the evolutionary tree.

The 'purple sock'

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