First giant filter feeder

The first giant filter-feeding animal was Aegirocassis benmoulai, the largest-known species of an ancient prehistoric group of arthropod invertebrates called radiodonts. It existed 480 million years ago, during the early Ordovician period. Exceeding 2 m (6 ft 6 in) long in total length, it was not only the largest radiodont ever, but also the largest animal of any kind known to have existed during that period – more than twice as long as the next largest animal species alive back then. A. benmoulai was formally named and described in the Journal of the Geological Society on 7 July 2015, based upon a well-preserved fossil disinterred from the Fezouata Formation deposits in Morocco, and it vaguely resembled a large crustacean with a whale-like head. Its name honours its discoverer, Moroccan amateur fossil collector Mohamed Ben Moula, as well as the Norse sea god Aegir.

Radiodonts, also known as anomalocarids, constitute a stem-group of arthropods, and also include among their number the famous giant carnivorous proto-arthropod Anomalocaris, which existed around 500 million years ago during the early/mid-Cambrian Period. At 38 cm (1 ft 3 in) long (excluding its tail fin), it was truly enormous for its time, and is thought to have been one of the earliest apex predators.