All amniote muscles, except that of the head, derive from a transient embryonic structure termed the dermomyotome. The formation of muscle from the dermomyotome of amniotes uses a highly conserved mechanism that distinct from that deployed by bony fish and amphibians. How the dermomyotome evolved to generate the distinct types of locomotor systems we see deployed through out the vertebrate phylogeny remains unresolved. In a very surprising set of new findings we have recently determined amniote-like muscle development in one of the most basal extant gnathostomes, the elephant shark (C. milii) but not in lamprey and or paddlefish embryos. This proposal seeks to examine the molecular basis of these striking evolutionary changes.