Complex skeletons emerged on the evolutionary timeline some nine million years earlier than previously thought.
So argues a new study that examines a tiny marine animal found in Namibia called Namacalathus hermanastes that was widespread during the late Ediacaran Period about 550 million years ago.
Prior evidence placed the start of complex animal life in the Cambrian Period, about 541 million years ago, during the Cambrian explosion, from which most key animal groups evolved.
The new study, published in the journal Proceedings of the Royal Society B and led by University of Edinburgh's Rachel Wood, suggests the tiny animal needs to be re-evaluated.
"This fossil has been known for a long time, and was assumed to have been a primitive animal, such as a sponge or coral," said Wood in an announcement. "This study suggests that it was, in fact, more advanced. We have suspected that these complex animals were present in the Ediacaran, but this study provides the first proof."
Wood and her team examined very well preserved fossils of N. hermanastes and found evidence for a rigid skeleton comprised of calcium carbonate, from which marine creatures' shells are created.
The complex structures, say the researchers, are similar to bottom-dwelling sea creatures today.