Ancient slowpoke.

A 1-centimeter-long 505-million-year-old fossil from British Columbia connects two lineages of marine invertebrates from the Cambrian period that scientists hadn't previously linked. One group, the halkieriids, protected themselves with plates and mineralized shells--"like armored slugs," says Simon Conway Morris, a paleontologist at the University of Cambridge in England. Wiwaxiids, the other lineage, carried spiny plates. The newly described creature, Orthrozanclus reburrus, had a shell at the front and spines all around (inset: artist's reconstruction). In the March 2 Science, Conway Morris and Jean-Bernard Caron of the Royal Ontario Museum in Toronto argue that O. reburrus, halkieriids, and wiwaxiids should be put together in a new group. The researchers speculate that the proposed group included various ancestors of modern-day mollusks, annelid worms, and brachiopods.