New research suggests Earth's first ecosystems were extraordinarily complex, and were not the simple setups that scientists had previously believed them to be.

A team of researchers looked at how a 555-million-year-old organism with no known modern relatives fed, and found they were some of the world's first complex organisms, the University of Bristol reported. The ancient creatures, dubbed Tribrachidiums, fed by collecting particles suspended in water, a technique that has never before been documented in organisms this old. In the past, researchers believed these organisms formed simple ecosystems characterized by only a few feeding modes.

"For many years, scientists have assumed that Earth's oldest complex organisms, which lived over half a billion years ago, fed in only one or two different ways. Our study has shown this to be untrue, Tribrachidium and perhaps other species were capable of suspension feeding. This demonstrates that, contrary to our expectations, some of the first ecosystems were actually quite complex," said Simon Darroch, an Assistant Professor at Vanderbilt University.

The researchers made their findings using CT scanning and a computer modeling approach called computational fluid dynamics. The method simulates fluid flows and is commonly used in engineering purposes such as aircraft design. This is one of the first times computational fluid dynamics has been used in the field of paleontology.

"Methods for digitally [analyzing] fossils in 3D have become increasingly widespread and accessible over the last 20 years. We can now use these data to address any number of questions about the biology and ecology of ancient and modern organisms," co-author Rachel Racicot, a postdoctoral researcher at the Natural History Museum of Los Angeles County.

The findings were published in a recent edition of the journal Science Advances