The fossil record of Ordovician eurypterids is quite poor. The majority of eurypterids once reportedly known from the Ordovician have since proven to be misidentifications or pseudofossils. Today only 11 species can be confidently identified as representing Ordovician eurypterids. These taxa fall into two distinct ecological categories; large and active predators from the ancient continent of Laurentia, and demersal (living on the seafloor) and basal animals from the continents Avalonia and Gondwana. The Laurentian predators, classified in the family Megalograptidae (compromising the genera "Echinognathus", "Megalograptus" and "Pentecopterus"), are likely to represent the first truly successful eurypterid group, experiencing a small radiation during the Late Ordovician.