Image of the Day: Early Bilaterian

The newly described Ikaria wariootia was a small, wormlike creature that marked an important evolutionary step between early multicellular organisms and more complex modern animals.

Amy Schleunes
Amy Schleunes
Mar 31, 2020
An impression of Ikaria wariootia generated by a 3D laser scan
DROSER LAB/UCR

Scientists have discovered one of the oldest known bilaterians, organisms with symmetrical sides and a gut that opens on either end, in 55-million-year-old fossilized deposits from Nilpena, South Australia, according to a study published on March 23 in PNAS

A 3-D laser scanner revealed that the wormlike creature had a cylindrical body measuring between 2 and 7 millimeters long and 1 and 2.5 millimeters wide, according to a press release, and was relatively complex compared to other organisms from the same time period because it appears to have burrowed under the sand on the ocean floor, suggesting “rudimentary sensory abilities.” 

“We thought these animals should have existed during this interval, but always understood they would be difficult to recognize,” Scott Evans, a recent doctoral graduate from the University of California, Riverside, says in the statement. “Once we had the 3D scans, we knew that we had made an important discovery.”

Impressions left behind by Ikaria wariootia
DROSER LAB/UCR

S.D. Evans et al., “Discovery of the oldest bilaterian from the Ediacaran of South Australia, PNAS, doi:10.1073/pnas.2001045117, 2020.