When the Guinness Book of Records calls the Flower Urchin the most dangerous urchin in the world, you know you shouldn't be messing around with it. Commonly found in the Indo-West Pacific region, what makes the Flower Urchin deadly is its venom. The venom contains two toxins: Contractin A and Peditoxin. Contractin A can cause spasms and clumping of red blood cells while Peditoxin can cause convulsions, anaphylactic shock and death.