Somatic layer of lateral mesoderm tissue derived from somites that goes on to form muscle cells and dermis (see figure below).
Cells in the somite differentiate in two directions: medially to form the sclerotome (eventually the vertebral column) and laterally to form the dermomytome (A). Subsequently, the dermotome (eventually the dermis) and the myotome (eventually muscle) are formed from the dermomyotome (B). Myotome differentiates into two components dorsally the epicure and ventrally the hypomere that become the epaxial and hypaxial muscles, respectively.
See Epimere, Hypomere, Mesoderm, Myotome, Notochord, Sclerotome, Somites