Megalograptus (Greek for "big writing") is a four-foot long Ordovician eurypterid (sea scorpion), and was among the earliest known genera. It was named so because its first fossils were of its very spiny legs, which were mistaken for massive graptolites. It lived from 460 to 445 mya. Megalograptus preyed on fish, trilobites, other sea scorpions, and smaller orthocones, using the spines on their claws to feel for their prey hiding in the sand and mud. However, adult Cameroceras, alongside with the bigger sea scorpion species preyed on it instead. Megalograptus did not have a stinger, but may have curled its tail and sword-like telson forward as a threat pose, much like a scorpion.