|Fossils and 3D computer models of Tribrachidium|
Tribrachidium was small and possessed a highly unusual triradial symmetry characteristic of a group of Ediacarans known as trilobozoans. This form of symmetry is seen nowhere else in the animal kingdom, both living and extinct. It is a failed experiment in body building.
A recent study by an international team of researchers, led by Dr Imran Rahman from the University of Bristol has shown that Tribrachidium's unusual design was well suited to a mode of nutrition known as suspension feeding - previously undocumented in the Ediacara biota. Suspension feeding is the capture of suspended particles from a water column which are too light to settle. This was achieved using computational fluid dynamics. More commonly encountered in the world of engineering, this mode of analysis is used to model the flows of water or air around and within pieces of machinery. This study, represents one of the first applications of the technique in palaeontology, following previous research also carried out by researchers from Bristol University.
|The computational flow dynamic models of Tribrachidium. The grey |
arrows represent flow direction. The double height set show the
recirculation of currents in the eddy behind the organism
In just the same fashion, the low velocity region behind Tribrachidium developed currents which recirculated back towards the body, and chanelled by the structure of the body, towards pits at the apex of the organism. Here nutritious particles in the water could be absorbed.
'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,' said Dr Simon Darroch, from Vanderbilt University, Tennessee. '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.'
The Ediacara biota were responsible for creating the first dynamic ecosystems on the planet. Yet this is a relative term. The Ediacaran ecosystems have been viewed as simple compared to those of the Cambrian and later periods. However, this study shows the gulf between them is not as vast as previously thought.