12-9 of Patten and Carlson. Somites formation accompanies neural plate closure and proceeds in a rostral to caudal direction.
Presomitic mesoderm has a positional identity before somite formation.
A signal from the notochord induces sclerotome formation . Maintenance of the sclerotome requires a signal from the neural tube. The posterior half of one sclerotome fuses with the anterior half of the next caudal sclerotome to form a single vertebrae. The dorsal root ganglia and peripheral nerves exit between the vertebrae. Formation of the tail bud.