A group of geologists from the University of California, Riverside, in the United States, discovered a worm-like creature they have named Ikaria wariootia believed to be the first ancestor of bilaterians, a family tree that contains most familiar animals today, including humans, according to a research paper published on Monday in the journal Proceedings of the National Academy of Sciences.
Scientists earlier discovered multicellular organisms with variable shapes, such as sponges and algal mats. For example, members of the Ediacaran Biota group, which covers the oldest fossils of complex multicellular organisms, are not directly related to today's animals, including lily pad-shaped beings known as Dickinsonia that lack elementary features of the majority of animals, such as a mouth or gut.
The remains of Ikaria were found in fossilized burrows contained within 555 million-year-old Ediacaran Period deposits in Nilpena, South Australia. Scott Evans, a recent doctoral graduate from University of California, Riverside, and Professor Mary Droser, a professor of geology, studied the ancient deposits and made the new finding.
Evans and Droser noticed tiny, oval impressions near some of the burrows. Funded by NASA, the two scholars used a three-dimensional laser scanner that revealed the regular, consistent shape of a cylindrical body with a distinct head and tail and faintly grooved musculature.
Creature that lived more than 555 million years ago is the 'oldest ancestor of all living creatures': The creature, called Ikaria wariootia, lived around 555 million years ago and was found in Australia. The largest of the species being about the same… https://t.co/0tE4ITLyXg pic.twitter.com/48wEnQBW3h— RushReads (@RushReads) March 23, 2020
Research estimates the size of Ikaria to be about two to seven millimetres long and up to 2.5mm wide. The largest example of this creature known to date is believed to be approximately the same size as a grain of rice.
“We thought these animals should have existed during this interval, but always understood they would be difficult to recognize,” Evans said, according to SciTech Daily. “Once we had the 3D scans, we knew that we had made an important discovery”.
The animal was reportedly named to acknowledge the original custodians of the land, as the word 'Ikaria' in the Adnyamathanha language means, 'meeting place', while ‘wariootia’ refers to Warioota Creek, which runs from the Flinders Ranges to Nilpena Station.
“Burrows of Ikaria occur lower than anything else. It’s the oldest fossil we get with this type of complexity,” Droser said. “Dickinsonia and other big things were probably evolutionary dead ends. We knew that we also had lots of little things and thought these might have been the early bilaterians that we were looking for.”
“This is what evolutionary biologists predicted,” Droser said. “It’s really exciting that what we have found lines up so neatly with their prediction.”