Although increasing numbers of vertebrate genomes are being sequenced, there are still stretches of evolutionary history without representation (Thomas and Touchman 2002) . Among aquatic organisms, teleosts are represented by significant EST and genomic sequencing, such as those in zebrafish and pufferfish. Until recently, chondrichthyes, which include elasmobranchs (sharks, rays and skates) were the only major line of gnathostomes, or jawed vertebrates, for which there are no major initiatives to generate genomic sequences. Sequence data from elasmobranchs have provided unique insights into conserved functional domains of genes associated with human liver function, multidrug resistance, cystic fibrosis, G protein coupled receptors, natriuretic peptide receptors, and other biomedically relevant genes (Valentich and Forrest 1991; Henson et al. 1997; Aller et al. 1999; Silva et al. 1999; Greger et al. 1999; Waldegger et al. 1999; Ke et al. 2002; Wang et al. 2002; Yang et al. 2002; Cai et al. 2001 Cai et al. , 2003 Mattingly et al. 2004b) .