This a great lesson about problems with identification. This is a genuine Cambrian fossil but was identified as "Anomalocaris roulette mouth". Thanks to a member of this forum I was put in touch with Dr Allison Daley from Oxford, a leading Anomalocaris expert from the Burgess Shale. The Doc confirmed to me that it was not Anomalocaris, but Omnidens Amplus, a Cambrian predator worm. I mentioned this to the seller and supplied an article on distinguishing the two, and got the Omnidens for 2\3 price! Love it.