Development of Jaws
Jaws evolved from the two anterior gill arch supporters
gill arches of cartilage in early fish; stabilize tissue between gills and keep gill slits open for water exchange
Stepwise evolution: gill arches became bent into “> form”
Fusion of top and bottom parts of two gill arches with hinges at the points; top half not yet attached to skull except at rear
Later: fusion of top half with skull underside
Teeth developedfrom modified skin skales