Sea scorpions (eurypterids), extinct giant aquatic arthropods, were apex predators. New research suggests that early species of the scorpion-like carcinosomatoid eurypterids, with spiny limbs, fed on trilobites and later species preferred armoured fishes. Carcinosomatoids evolved into scorpions but giant 400-million-year-old scorpions like Praearcturus and Brontoscorpio, as featured in Walking with Monsters (TV series), were probably crustaceans. Reconstruction...