Thanks to Phil for pointing this one out. In a recent Science publication, Karen Osborn et al. describe a new class of deep sea dwelling worms, that go by the name of swima worms. They have some interesting attributes with regard to bioluminescence, such as the ability to "drop" little light bombs to distract would be predators. When I saw one particular species in the accompanying photographs, I was really struck by how basic some adaptations are that lead to diverse groups of species such as Cephalopods and, say, Anomalocarids, all derived from the same segmented bodyplan. The second specimen from the left in the accompanying photograph (C.O. BBC Science news) being a fine example of all the building blocks being available.