All the bones of the craniofacial skeleton are united by the fibrous sutures, and those of the neurocranium are lined additionally by the dura mater. The sutures and dura mater are not only integral structural elements of the formed skeleton, but during morphogenesis they also are sites of appositional growth of the membranous bones of the vault and inductive interactions that regulate the process of suture obliteration, respectively (1 -5 ). When sutures fail to form or are prematurely fused prior to cessation of rapid brain growth, morphogenesis of the entire head is severely altered (6 ). Although a variety of approaches employing transplantation of embryonic rudiments and surgical perturbation of elements of the developing craniofacial skeleton have demonstrated that cellular interactions among the perisutural tissues are critical to morphogenesis (1 ), recent development of media and methods for growing fetal rat and mouse calvaria in vitro from non-mineralized rudiments may allow identification of the molecules and mechanisms underlying normal craniofacial development (3 ,7 -11 ).
