EVOLUTIONARY RELATIONSHIPS OF CARTILAGINOUS FISHES - AN IMMUNOLOGICALSTUDY

An investigation of the phylogenetic relationships of a number of cart ilaginous fish based on the use of the immunological properties of the iron-binding serum protein, transferrin, is presented. Data on immuno logical distance and the rate of amino acid substitution are used to p roduce a dendrogram. The tree confirms the close relationships of the holocephalan species examined which are a sister group of other neosel achians. The tree also indicates that the squaloids and galeoids are s eparate groups and that Heterodontus belongs with the galeoids. It is also clear that the divergence between the squaloids, galeoids (includ ing Heterondontus) and the Holocephali is an ancient one and that the rajids probably diverged from this basal stock rather than any more re cent squaloid/squatinoid/galeoid grouping.