THE PHYLOGENETIC POSITION OF ECHMATOCRINUS-BRACHIATUS, A PROBABLE OCTOCORAL FROM THE BURGESS SHALE

The biological affinities of Echmatocrinus brachiatus Sprinkle, from t he Burgess Shale (Middle Cambrian) of British Columbia, are re-evaluat ed based on study of all available material. This animal has an elonga te, thinly plated/scaled body with a holdfast at one end and a calyx w ith eight(?) arms/tentacles at the other. Each of the latter bears alt ernating pinnule-like branches, and the pattern of the textured platin g is very irregular, except for the uniserially plated arms/tentacles. Originally, Echmatocrinus was considered to be a crinoid, and recentl y it has been considered to be a cnidarian. The lack of any unequivoca l echinoderm characters tends to discount the crinoid affinities of Ec hmatocrinus. Some characters suggest affinities with octocoral cnidari ans, but, again, unequivocal affinity with cnidarians is lacking. Howe ver, the presence of eight arms/tentacles, an elongate conical body, a nd plating similar to living primnoid octocorals suggest that an octoc oral affinity is more probable.