Muscles in animals may have developed 560m yrs ago

Researchers have discovered the fossil that comprised of bundles of fibers in a broadly four-fold symmetrical arrangement, suggesting the presence of animals with muscles 560 million years ago.

The researchers from the University of Cambridge have interpreted the new fossil, which was discovered in Newfoundland, Canada, as a cnidarian: the group which contains modern animals such as corals, sea anemones and jellyfish.

Historically, the origin, evolution and spread of animals had been viewed as having begun during the Cambrian Explosion, a period of rapid evolutionary development starting 541 million years ago when most major animal groups first appeared in the fossil record.

Lead author of the paper, Dr Alex Liu, said that in recent decades, discoveries of preserved track ways and chemical evidence in older rocks, as well as molecular comparisons, had indirectly suggested that animals had a much earlier origin than previously thought.

The new fossil, named Haootia quadriformis, dates from the Ediacaran Period, an interval spanning 635 to 541 million years ago and also differs from any previously described Ediacaran fossil as it shows a body plan that was similar to that seen in modern cnidarians.

The researchers determined that the similarities between Haootia quadriformis and both living and fossil cnidarians suggest that the organism was probably a cnidarian, and that the bundles represent muscular tissue.

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