Aegirocassis benmoulae — an ancient ancestor of all anthropods, a category of animals which includes crustaceans as well as spiders and insects such as ants — swam through the sea roughly 480 million years ago eating plankton and at the time, it was the largest animal on the planet, according to a new study published on March 11, 2015 in the journal Nature.
The study was conducted by researchers affiliated with Yale University, Ghent University, and the University of Oxford.
Peter Van Roy, co-author of the report and an archaeologist at Yale, was quoted by The Verge in a report as having said that the ancient crab relative “would have dwarfed anything else at the time,” making it at least “twice as big” as the next largest animal on the planet while it was alive.
It would have dwarfed anything else at the time, being twice as big as the next biggest animal — at the very least […] They were absolutely massive.
When the bits and pieces of the animal were first discovered, archaeologists saw their spiny appendages and misinterpreted them as a shrimp’s body. Others mistook their toothed mouths for jellyfish, but then a group of researchers figured it out back in 1985 when they realized that these weren’t different species, they were all pieces of a single group of early marine animals known as anomalocardids.Anomalocardids, which were large sea creatures, are the ancient ancestors of anthropods, which are an invertebrate animal of the large phylum Anthropoda exhibiting segmented bodies, jointed limbs, and usually a chitinous shell which undergoes moltings. This includes insects, spiders and other arachnids, myriapods, and crustaceans.