About two dozen families of eurypterids “sea scorpions” are known from the fossil record.
Although these ancient predators have a superficial similarity, including a defensive needle-like spike or telson at their tail end, they are not true scorpions. They are an extinct group of arthropods related to spiders, ticks, mites and other extant creepy crawlies.
Eurypterids hunted fish in the muddy bottoms of warm shallow seas some 460 to 248 million years ago before moving on to hunting grounds in fresh and brackish water during the latter part of their reign. Their numbers diminished greatly during the Permian-Triassic extinction, becoming extinct by 248 million years ago.
Eurypterids are found in Canada, most notably at the Ridgemount Quarry near Niagara Falls. This near-perfect specimen of Eurypterus remipes, held by my young cousin Sivert, was named the official state fossil of New York in 1984.