535-million-year-old animal microfossils with rare preserved muscle discovered in China

An international research team has discovered musculature fossils dating back some 535 million years to the early Cambrian Age in China.

The team of paleontologists has reported their discovery of the microfossils, which have preserved the introvert musculature of cycloneuralians, a group of animals that includes roundworms, horsehair worms and mud dragons.

The study was led by Zhang Huaqiao, a researcher at the Chinese Academy of Sciences' Nanjing Institute of Geology and Palaeontology, and published online on Wednesday in the journal Proceedings of the Royal Society B: Biological Sciences.

One of the three phosphatized and millimeter-scale specimens found in the South of Shaanxi province is better preserved than the others, consisting of five increasingly large rings that are connected with 19 radial and 36 longitudinal structures, Zhang said.

The rings are compressed to varying degrees, implying the cycloneuralians were flexible when alive. This musculature would have facilitated movement and feeding, according to Zhang.

"Early animal muscle fossils have provided an important basis for our understanding of the evolution of locomotion. Through these fossils, we can learn how animals moved in ancient times and how they gradually developed the locomotor skills they have now," he said.