The vertebrate jaw is a key innovation in evolution allowing adaptation to new environments. Changes in jaw proportions is a common in lineages allowing for specific feeding and behavioral adaptations. We are interested in variation in size of the jaw and how they vary. Through comparative genetics, we have defined a core regulatory hub controlling jaw size that is conserved among all jawed vertebrates. Through use of zebrafish transgenic models as well as broad comparative genomic analyses, we are dissecting the control of this regulation locus and how it affects variation in jaw size evolution and in disorders affecting the jaw such as microsomia.