Phylogenetic Relationships of Echinoderms : Biochemical Evidence

Abstract

THE conclusion that present day asteroids and ophiuroids have descended from the crinoids by way of somasteroids¹ has been challenged by G. M. Philip², who argued that palaeontological evidence would not bear out the apparent homologies of structure of living sea-stars and crinoids. Fell, the proponent of the theory, has given a seemingly adequate reply³. Both authors, however, appear to be unaware of, or have chosen to ignore, evidence from comparative biochemistry that clearly has a bearing on the problem of the relationships of the echinoderm phyla : it suggests that crinoids may lie on a different line of descent from any of the other four classes. In fact, in so far as biochemistry constitutes acceptable evidence, it makes Fell's proposal that Somasteroidea, Asteroidea and Ophiuroidea are sub-classes of class Crinoidea¹ appear to be untenable.