Work supported on a previous NSF grant has demonstrated that the development of craniofacial systems in placental and marsupial mammals is characterized by large scale changes in relative rate and timing. Specifically, the development of the central nervous system and skeletal system are both dramatically slowed in metatherians relative to eutherians, however, the development of the muscular system is greatly accelerated. These results confirm hypotheses that suggest metatherians possess specific developmental adaptations to the requirements of their life history and suggest, somewhat surprisingly, that the development of craniofacial systems is quite plastic. In the current project these results will be extended in two major directions. First, craniofacial development will be examined in other mammalian species to ask whether the variation is limited to characterizing the two largest mammalian groups, eutherians and metatherians. Second, preliminary studies on the cellular and molecular bases of the developmental patterns observed will be initiated and the development of the nervous system will be examined in detail. This study will combine comparative information with data on gross, histological, cellular and molecular processes to allow an integrated approach to craniofacial development. The results obtained will address specific and significant problems on mammalian biodiversity and provide opportunities to examine the mechanisms of and constraints on developmental patterns.
