Fossilized fat indicates that a sea creature from 550 million years ago could have been the first animal to exist on Earth.

A strange marine organism, resembling a blend of a leaf and a fingerprint in its fossil form, could be the oldest known animal on Earth, with an age of 558 million years.

According to New Scientist, researchers from the Australian National University (ANU) made an important discovery in a remote part of Russia: a Dickinsonia fossil still containing fat molecules. These unique, oval-shaped creatures were soft-bodied with rib-like structures along their sides and grew up to about 4.5 feet long. Described as “strange as life on another planet,” these creatures are detailed in an abstract from a paper published in the journal Science.

Though Dickinsonia fossils were initially discovered in South Australia in 1946, researchers lacked the necessary organic material to classify the organism. 'For over 75 years, scientists have been debating what Dickinsonia and other peculiar fossils from the Ediacaran biota actually were: giant single-celled amoebas, lichen, evolutionary dead ends, or the first animals on Earth,' said senior author Jochen Brocks, an associate professor at ANU, in a statement.

The identification of cholesterol molecules, which are found in nearly all animals but not in bacteria or amoebas, has confirmed that Dickinsonia were animals. These creatures lived in the seas during the Ediacaran Period, from 635 to 542 million years ago. More complex life forms like mollusks, worms, and sponges did not appear until about 20 million years later.

The fossil containing fat molecules was uncovered on cliffs near the White Sea in northwest Russia, an area so remote that researchers had to be flown in by helicopter. Gathering the samples was an extraordinarily dangerous task.

'I had to hang from ropes over the cliff’s edge, dig out massive sandstone blocks, drop them down, wash them, and repeat the process until I found the fossils I was seeking,' said lead author Ilya Bobrovskiy of ANU. Given that this discovery could alter our understanding of Earth’s earliest life forms, the risk seems to have been worth it.