Conodonts, tiny eel-like creatures that lived from 520 million to 205 million years ago and were our earliest vertebrate relatives, have long been one of paleontology’s great enigmas. These soft-bodied animals had lots of hard parts in their mouths--and since there were also lots of conodonts, those hard parts are now scattered through rocks around the world. But what were they? Filters for straining plankton from the water? Teeth for shredding other animals? Fossils of whole conodont bodies are rare, and they’ve been considered too squashed to be of much help. But this past year Mark Purnell and his colleagues at the University of Leicester in England said they’d discovered how to squeeze more information out of the fossils. They built models of the hard parts and took photos of them from a number of angles. The photos showed what the three-dimensional models would look like if they were pressed flat, like fossils--and the photos that looked most like the real fossils told the researchers which model was most like a living conodont. Purnell’s team then looked for the places on the winning model where the hard parts touched one another and examined those same contact points on the fossils. They found that the points were scratched and chipped--just as teeth would be, from grinding against one another. This evidence suggests that hard parts appeared in order to make the earliest vertebrates more efficient hunters and killers, says Purnell.