Origin, Development and Evolution of the Fish Skull

The evolutionary origin of the brain and braincase of fishes remains largely elusive. The development of the vertebrate skull is dependent on the presence of an embryonic neural crest whose cells migrate to induce the formation of various elements of the cranial skeleton, dentitions and certain soft tissues. Much progress has been made in the understanding of the vertebrate skull since pioneering anatomical descriptions made last century. In the last few decades, studies involving micro-anatomy, ontogenetic development, molecular biology and gene expression have shed light on key developmental processes that seem to be widely shared among vertebrates. However, molecular biology and ontogenetic studies have been restricted to a small number of fish species. There is still much uncertainty about precise homologies between parts of the skull of distinct groups of fishes, due to the fact that the vertebrate skull shows a remarkable morphological and anatomical plasticity.