The oldest known muscle tissues have been found, researchers report, in the fossilized tissues of a soft-bodied creature that shares an ancestor with modern sea anemones, jellyfish and corals.

The 560-million-year-old fossil bears an impression of muscles as fibers arranged in parallel bundles, said Alexander G. Liu, a paleobiologist at the University of Cambridge in England and the lead author of a new study in the journal Proceedings of the Royal Society B.

“They are preserved in a very similar way to jellyfish tissue throughout the fossil record,” he said.

Dr. Liu and his colleagues from England and Canada discovered the fossil in Newfoundland in 2008 and suspected that they might have stumbled on muscle tissue.