The Early Cambrian Halkieria is a mollusc

Halkieria evangelista was originally interpreted as a stem-group brachiopod. It was laterproposed that the brachiopods evolved from a halkieriid ancestor that curved ventrally, lost thefoot and radula, developed a lophophore as a new feeding organ, and modified the sclerites tochaetae. Molluscan affinities have been discussed by a number of authors. We have studieds ome of the original material of Halkieria and found that all the characters that can be observed with certainty are compatible with characters in living molluscs. The combination of characters observed in Halkieria does not fit with any of the living classes of molluscs, so we propose placingit in a new class, Diplacophora. Living polyplacophorans have hairs secreted by a number of epithelial cells and containing nerve cells; they are clearly not homologous with annelidchaetae. Thus, there is no support for theories that regard Halkieria as belonging to the stemgroup of either the annelids or brachiopods.