Article: The phylogenetic position of Echmatocrinus brachiatus, a probable octocoral from the Burgess Shale

The biological affinities of Echmatocrinus brachiatus Sprinkle, from the Burgess Shale (Middle Cambrian) of British Columbia, are re-evaluated based on study of all available material. This animal has an elongate, thinly plated/scaled body with a holdfast at one end and a calyx with eight(?) arms/tentacles at the other. Each of the latter bears alternating pinnule-like branches, and the pattern of the textured plating is very irregular, except for the uniserially plated arms/tentacles. Originally, Echmatocrinus was considered to be a crinoid, and recently it has been considered to be a cnidarian. The lack of any unequivocal echinoderm characters tends to discount the crinoid affinities of Echmatocrinus. Some characters suggest affinities with octocoral cnidarians, but, again, unequivocal affinity with cnidarians is lacking. However, the presence of eight arms/tentacles, an elongate conical body, and plating similar to living primnoid octocorals suggest that an octocoral affinity is more probable.