Opabinia of the early Cambrian . Arthoscorpio, a cave-dwelling, aquatic scorpion with a striking resemblance to Brontoscorpio of the Silurian. Cave Shark, a cave-dwelling, fast-swimming shark that preyed upon of worms and scorpions. Wormsnatcher, a cave-dwelling, crocodile-like, predatory amphibian with a striking resemblance to Rhinesuchus of the Late Permian. Mint Seaweed,