ABSTRACT
The origin and evolution of chordates and vertebrates, particularly the origin of the vertebrate head, has fascinated researchers for centuries. The origin, development, and comparative anatomy of hard (e.g., skeleton) and soft tissues (e.g., muscles, nervous system, and cardiovascular system) are crucial pieces of information for this investigation. The discovery that both branchiomeric muscles and myocardium are derived from a cardiopharyngeal field was a crucial contribution to understanding of the evolution of chordate muscles. The discovery of the cardiopharyngeal field also revealed genetic mechanisms that are conserved in vertebrates and seem to have been present in the last common ancestor (LCA) of Olfactores. However, in larval amphioxus, the pharynx has an asymmetric development, a feature that was likely not present in the LCA of chordates. However, recent works, as well as some older and unfortunately often ignored studies, clearly show that branchiomeric muscles related to the pharynx were present in the LCA of chordates.
