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A pink, flatworm-like animal, earlier known as a single species, but puzzling biologists for more than 40 years, has been finally identified in the waters near Sweden by researchers from the University of California, San Diego. With genetic analysis, the team identified four new species in the Xenoturbella genus.

The unique specimen among this species is the X. churro, a 10-centimeter long purple worm labelled after a popular churro fried-dough pastry located at the bottom of the animal evolutionary tree. It was found in a cold seep in the Gulf of California about 1,700-meters deep. The species discovered apart from X. churro included X. monstrosa, X. hollandorum and X. profunda.

"The findings have implications for how we understand animal evolution," Greg Rouse, lead author of the study, said in a press release. "By placing Xenoturbella properly in the tree of life we can better understand early animal evolution."

The first species found in the Xenoturbella genus was X. bocki, found in the 1950s near Sweden. First called a flatworm, and followed by a simple mollusk, the Xenoturbella recently is classified as closely related to vertebrates and echinoderms. It could even be called a distant relative in its branch.

"When Greg first spotted the worms gliding through a clam field in Monterey Bay, we jokingly called them purple socks," said Robert Vrijenhoek, co-author of the study.

So far, about 1,200 of the unique animal's genes have been identified. It has permitted them to determine that they lie at the bottom of the evolutionary tree of "bilaterally symmetrical animals". As they have "no brain, gills, eyes, kidneys or anus" and their only body opening is their mouth, they are called "evolutionary, simple members of the tree", according to HNGN.

Scientists have now expanded the diversity of the species from one member to five, helping us to become better aware of the evolution of animal organ systems, including "brains, guts and kidneys".

The study was published in the Feb. 3,2016 issue of Nature.