From ScienceDaily:
Ediacaran fossils have a slightly bizarre appearance not shared by any modern animal groups. For decades, researchers believed these enigmatic fossils were ecologically simple. However, borrowing a method from modern ecology — fitting species to relative abundance distributions — Vanderbilt University paleontologist Simon A.F. Darroch and his team learned that these organisms were more like modern animals than once thought.
The analyses showed that a majority of fossil assemblages bear the hallmarks of being ecologically complex, and Ediacara biota were forming complex communities tens of millions of years before the Cambrian explosion. The creatures lived partially submerged in what was once the ocean floor, some of them suspension feeding, others filter feeding, still others passively absorbing nutrition. A few were even mobile.
Complex communities are ones that comprise species competing for numerous different resources or species that create niches for others (as in many modern-day ecosystems). The team found that the signature of complex communities extends all the way back to the oldest Ediacaran fossils. In other words, as soon as macroscopic life evolved, it began forming diverse ecological communities not unlike those in the present day.
…
“Supporting a simple model would suggest that these mysterious organisms were universally primitive, sharing the same basic ecology and all competing for the same resources,” he said. “Support for the complex model would instead suggest that they likely competed for a variety of different resources, just like modern animals. Our analyses support the complex model, illustrating that — even though they may look bizarre — these mysterious fossils may have far more in common with modern animals than we thought.” Paper. (paywall) – Simon A. F. Darroch, Marc Laflamme, Peter J. Wagner. High ecological complexity in benthic Ediacaran communities. Nature Ecology & Evolution, 2018; DOI: 10.1038/s41559-018-0663-7 More.
In short, there was no long, slow, Darwinian development of complex communities. We need a word for this: How about… ecological creationism?
See also: Researchers: First Ediacaran animal identified
and
Oldest known multicellulars are Ediacaran seaweed 555 mya