London, Nov 29 (IANS): Earth's first ecosystems were more complex than previously thought, a team of researchers have found after studying the mode of feeding of an extinct aquatic organism.

Using a computer modelling approach called computational fluid dynamics, the team of researchers from Canada, the UK and the US were able to show that Tribrachidium, which lived in the oceans some 555 million years ago, fed by collecting particles suspended in water.

"This is called suspension feeding and it had not previously been documented in organisms from this period of time," the researchers, including Dr Imran Rahman from the University of Bristol, observed.

Tribrachidium, whose fossils were used in the study, lived during a period of time called the Ediacaran, which ranged from 635 million to 541 million years ago. This period was characterised by a variety of large, complex organisms, most of which are difficult to link to any modern species.

It was previously thought that these organisms formed simple ecosystems characterised by only a few feeding modes, but the new study - published in the journal 'Science Advances' - suggests they were capable of more types of feeding than previously appreciated.

"The computer simulations we ran allowed us to test competing theories for feeding in Tribrachidium. This approach has great potential for improving our understanding of many extinct organisms," Dr Rahman said.

"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," Dr Simon Darroch, an assistant professor at Vanderbilt University in the US, said.

"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," he added.