What are myotomes in cephalochordates?

In cephalochordates, myotomes are blocks of muscles organized into serially repeated units known as metameres. These segmental muscles are well developed and are primarily utilized for locomotion.12

The body of a cephalochordate is largely composed of these segments, a structural organization that also extends to the nerves supplying the myotomes, as well as to certain body cavities and excretory structures. This segmental arrangement is thought to provide more effective body coordination during movement. The myotomes in cephalochordates are highly similar to those found in vertebrates, suggesting that this form of segmentation was present in the common ancestor of both groups.1