In Depth

Why everyone’s talking about Ikaria wariootia

Worm-like creature that could be 'ancestor of all animal life' found in Australia

The earliest organism that could be the ancestor of all animal life has been found in fossil deposits in Australia.

This tiny, worm-like creature, measuring between two and seven millimetres long, lived more than 555 million years ago.

Named Ikaria wariootia, it is the earliest known bilaterian – meaning an organism with a front and back, two symmetrical sides, and openings at both ends connected by a gut, says The Times.

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What has happened?

For 15 years, scientists agreed that 555 million-year-old Ediacaran Period fossilised burrows in Nilpena, South Australia, were made by bilaterians, reports Science Daily.

However, there was no sign of the creature that made them until a team led by University of California, Riverside (UCR) geologists noticed tiny, oval impressions near the burrows.

The organism is important in evolutionary biology because “a multitude of animals, from worms to insects to dinosaurs to humans, are organised around this same basic bilaterian body plan”, reports UCR.

Being bilaterian, or possessing bilateral symmetry, allows organisms to move purposefully. Ikaria was a complex organism, compared to others from the period, and burrowed in sand layers on the seabed to find food, “indicating rudimentary sensory abilities”, says Science Daily.

The burrows also show V-shaped ridges, “suggesting Ikaria moved by contracting muscles across its body like a worm”.

The genus name Ikaria comes from the word “ikara”, meaning meeting place in the language of the local people, says the Times. The nearby Warioota Creek supplies the species name.

What has the reaction been?

Palaeontologist and lead author of the study, Scott Evans of the Smithsonian Institution’s National Museum of Natural History in Washington, told Science Daily: “Once we had the 3D scans, we knew that we had made an important discovery.”

“This is what evolutionary biologists predicted,” said Mary Droser, co-author and professor of geology. “It’s really exciting that what we have found lines up so neatly with their prediction.”

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