Megalograptidae

Megalograptidae are a family of eurypterids, an extinct group of aquatic chelicerate arthropods commonly known as "sea scorpions".

The megalograptids were likely the first major successful group of eurypterids, evidenced by a Late Ordovician radiation. All known members of the Megalograptidea are from the Late Ordovician of Laurentia with the exception of the large Pentecopterus from the Middle Ordovician.