Sclerotomes become subvidided into an anterior and a posterior compartment.

http://en.wikipedia.org/wiki/Human_vertebral_column

Sclerotomes become subvidided into an anterior and a posterior compartment. This subdivision plays a key role in the definitive patterning of vertebrae that form when the posterior part of one somite fuses to the anterior part of the consecutive somite during a process termed resegmentation. Disruption of the somitogenesis process in humans results in diseases such as congenital scoliosis.