Pterygotus ("Winged One") was a giant sea scorpion that was a distant ancestor of the modern day crab.
Known as the titan of all Sea Scorpions, Pterygotus was arguably the largest arthropod of all time. Measuring more than three meters in length, they were the size of modern day crocodiles.
Pterygotus is depicted as an ambush hunter, lying in wait under the sea-bed for unsuspecting prey to arrive. The females also cared for their young, as they shared whatever "they turned the tables on" with their young.