Tiny fossils push back complex skeleton timeline

Washington D.C.: The fossils of a tiny marine creature unearthed in Namibia has suggested that complex skeletons evolved far earlier than we previously thought.

The find is the first to suggest the earliest complex animals on Earth - which may be related to many of today's animal species - lived millions of years earlier than was previously known.

Until now, the oldest evidence of complex animals - which succeeded more primitive creatures that often resembled sponges or coral - came from the Cambrian Period, which began around 541 million years ago. Scientists had long suspected that complex animals had existed before then but, until now, they had no proof.

Genetic family tree data suggested that complex animals - known as bilaterians - evolved prior to the Cambrian Period. The finding suggests that bilaterians may have lived as early as 550 million years ago, during the late Ediacaran Period.

The study suggests that complex animals existed long before a period in the planet's history - known as the Cambrian explosion - during which most major animal groups evolved.

University of Edinburgh's Rachel Wood, who led the study, said that this fossil has been known for a long time, and was assumed to have been a primitive animal, such as a sponge or coral. This study suggests that it was, in fact, more advanced.

The study is published in the journal Proceedings of the Royal Society B.