The first cut...

Earlier this semester, my vertebrate zoology class discussed the conodonts, the jawless vertebrates that arose in the Cambrian and own the distinction of being the first toothed vertebrates.  New research published in the Proceedings of the Royal Society B and summarized here at Nature News reveals that these first teeth were also among the sharpest.  The  extreme sharpness may have allowed the small, jawless conodonts to produce significant forces with the side to side action their teeth.  In addition, there's evidence that the animals had mechanisms allowing them to sharpen and condition their super-sharp teeth as they were worn down or broken. 
Fossil  conodont teeth were known from Cambrian rocks long before the animals that bore them were identified.  Now, it looks like these relatively little-known vertebrates were solving some evolutionary puzzles before the jawed counterparts that followed them, and in a dramatically different way.