UPPSALA, Sweden, Dec. 7 (UPI) -- Biologists and paleontologists have long struggled to tease out the relationships between some of the planet's first complex organisms and more modern lineages.
The fossil group Ediacaran biota has proven especially puzzling. But in working to understand these ancient creatures, scientists may have happened upon a new way of understanding early evolution.
The animal fossil record doesn't begin in earnest until about 540 million years ago. But Ediacaran biota show up prior to the start date, and have been found all over the world.
In a new survey, published in the journal Biological Reviews, researchers suggest the strange fossil group served as the roots of the earliest animal lineages. Their paper also offers a new perspective on Ediacaran biota's role in facilitating the evolution of Earth's earliest complex organisms.
Previously, researchers argued it was only after the decline of Ediacaran biota organisms that more recognizable lineages proliferated during what's known as the Cambrian explosion. This view assumes Ediacaran biota previously prevented accelerated evolution, just as the dinosaur's dominance delayed the evolutionary progress of mammals.
The new research, however, suggests the presence of Ediacaran biota actually encouraged early animal evolution. The stationary creatures helped concentrate the presence of nutrients above and below the sediment-water boundary, creating early hot spots of biodiversity on the savannahs of East Africa.
The theory plays nicely with the new way of understanding localized evolution, called ecosytem engineering. Ecosystem engineering describes the ways in which certain species, like beavers, play an out-sized role in shaping the environment and creating new evolutionary opportunities for other species.
In addition to playing a cooperative role, researchers believe Ediacaran biota stuck around for a while after the Cambrian explosion.
"Rather than being obliterated by the rise of the bilaterians, the subtle remnants of Ediacara-style taxa within the Cambrian suggest that they remained significant components of Phanerozoic communities," researchers wrote in their new paper.
Eventually, the rise of early animals -- bilaterians or other metazoans -- squeezed out the Ediacaran biota.