Hello!

This a megalograptus, or mixopterus, which are both species of eurypterid, though this eurypterid is more likely to be a megalograptus, since mixopteruses' third pair of appendages were much smaller than the megalograptuses'. It was about the size of a person, though a little smaller, while the Jaekeloptreus, another type of eurypterid was much larger than a human, though the megalograptus was a very unique species, which was only similar to the previously mentioned mixoptreus. The megalograptuses' name means "Big/Great writing" since it was originally thought to be a graptolite (a type of filter-feeding animal). These guys lived near shore, capturing prey with its appendages that are seen in many (and possibly all) eurypterids.

-C