I have shown that one of the most fundamental differences 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 cranial skeletal-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. Currently my work is focused on the timing and pattern of early neural crest migration in marsupials. In recent years I have demonstrated that neural crest differentiates and migrates earlier in marsupials, relative to neural tube or somite differentiation, than in another other vertebrate thus far reported. I am now focusing on the patterns of expression of major genes thought to impose regional identity on the neural crest and neural tube.
In addition I am looking at the phylogenetic context of these heterochronies, with a comparative study of early development in therian mammals, monotremes, and non-mammalian amniotes in order to identify the primitive developmental condition for mammals.