Description

Pentecopterus is an eurypterid genus, a group of aquatic arthropods that no longer exists. Fossils of Pentecopterus have been documented from the Darriwilian period of the Middle Ordovician, dating back as far as 467.3 million years ago.

Belonging to the Megalograptidae family of eurypterids, Pentecopterus is categorized within a group that distinguishes itself from other eurypterids through the presence of two or more pairs of spines per podomere on prosomal appendage four. This family also displays a reduction in most spines and possesses large exoskeletons adorned with ovate to triangular scales. With an estimated length of around 1.7 meters (5 ft 7 in), Pentecopterus ranks among the largest eurypterids and arthropods ever found.