Aegirocassis benmoulai

Aegirocassis was a remarkable sea scorpion that thrived during the Ordovician period, around 460 million years ago. As one of the largest known eurypterids, it grew up to 2 meters (6.5 feet) in length, dominating the marine ecosystems of its time. Its body was covered in hard exoskeletons, and it possessed a unique set of specialized front appendages, which scientists believe were adapted for filter feeding. These appendages, shaped like large, paddle-like structures, helped Aegirocassis sweep through the water, capturing plankton and small invertebrates. Unlike many of its predatory relatives, which used claws to seize prey, Aegirocassis likely used these feeding appendages in a similar fashion to modern filter-feeding arthropods like certain crabs and shrimp. Its well-developed compound eyes indicate it had excellent vision, and it likely used its large, muscular limbs for swimming in the open ocean, propelling itself with a side-to-side rowing motion. Aegirocassis’s unique ecological role during the Ordovician represents an early example of filter feeding in large arthropods, and it likely helped shape the dynamics of ancient marine food chains.