Conserved and unique transcriptional features of pharyngeal arches in the skate (Leucoraja erinacea) and evolution of the jaw

The origin of the jaw is a long-standing problem in vertebrate evolution. Classical hypotheses of serial homology proposed that the upper and lower jaw evolved through modification of dorsal and ventral gill arch skeletal elements, respectively. If the jaw and gill arches are derived members of a primitive branchial series, we predict that they would share common developmental patterning mechanisms. Using RNAseq/differential gene expression analyses, we find broad conservation of dorsoventral patterning mechanisms as well as unique transcriptional features within the developing mandibular, hyoid and gill arches of a cartilaginous fish, the skate (Leucoraja erinacea).