Dolichopterus

Dolichopterus is a genus of the prehistoric sea scorpions, arthropods in the order Eurypterida.

Distribution
It lived in the Late Silurian (around 420 million years ago) in shelf or epicontinental seas of the region where Avalonia, Baltica and Laurentia met during the Caledonian orogeny; its fossils have been found in modern-day North America and the Baltic region. They were about 25–30 centimetres (10–12 in) long.

Relative
Strobilopterus probably was one of the closest relatives of Dolichopterus, but overall the phylogeny and systematics of the family Dolichopteridae is disputed: some place it closer to the Eurypteridae, while others assign it to the second lineage of sea scorpions which contains the Stylonuridae.