ABSTRACT
Three new approaches in molecular systematics are reviewed. The first consists of a new way of inferring phylogenies from nucleotide sequence data. This technique removes the effects of parallel and convergent evolution if the sequences diverged under the Kimura 3 parameter process. The second uses rare genomic events, such as mitochondrial gene order rearrangements and the amplification of repetitive DNAs as phylogenetic markers. The third uses homeobox gene expression patterns to establish inter-phylum homologues. Special emphasis is given to a review of the molecular data relevant to the question of the relationships among the major extant echinoderm classes: there is strong support for the echinoids and holothurians being monophyletic, and for the unrooted topology (A,0),(E,H).
