It's taken along time but the head with teeth is finally identified. One weird animal with no precursors:-http://www.theverge.com/2015/6/24/8838169/hallucigenia-worm-fossil-nature-study-2015-"'We've known this animal for over 100 years, and it just sort of seems wrong that we didn't know which end was the head and which end was the tail," Smith says. "Even just finding out where the head was was quite exciting, so the fact that it's also key to unlocking a recognized, but poorly defined group… that was really the icing on the cake, I suppose.'"-Great video animations