Kathleen Smith, Biology

I study a wide variety of topics on cranial development, function and evolution in vertebrates. In recent years I have focused on comparative studies of craniofacial development in marsupial and placental mammals. This work has demonstrated that the most fundamental difference between the two taxa is a delay in marsupials of the development of the central nervous system (CNS) and cranial sense organs and an advancement of certain cranialskeletal-muscular tissues. Specifically, in marsupials the central nervous system and particularly the forebrain is delayed relative to the development of the bones around the oral apparatus, the chondrocranium and the differentiation of cranial muscles. This observation is important because in many fundamental ways the central nervous system is responsible for patterning the skeletal tissues of the head. In particular, the CNS, through the differentiation of the neural crest, provides the material for the cranial skeleton, and the CNS provides signals thought to be important in the induction and patterning of the chondrocranium.

I am continuing this study using a variety of morphological and molecular-genetic markers that indicate early differentiation and patterning in the central nervous system and skeletal tissues of the head. In particular, I am examining the timing and pattern of early neural crest migration in marsupials. In addition, I am looking at the phylogenetic context of these heterochronies.

Three sets of taxa are included: Monotremes will help elucidate the primitive mammalian condition; selected eutherian and metatherians will confirm that the patterns in Mus and Monodelphis are general for these clades; and, finally, comparisons with non-mammalian amniotes will further allow identification of the primitive developmental condition for mammals.