Ancient Arthropod Was Seven Feet Long

Posted on March 12, 2015

Aegirocassis benmoulae

A fossil has been discovered of one of the biggest arthropods that ever lived. Aegirocassis benmoulae was seven feet long and inhabited southeastern Morocco about 480 million years ago. The sea creature had gills, modified legs and fed using a filter system.

Yale University paleontologist Derek Briggs says in a statement, "Aegirocassis is a truly remarkable looking creature. We were excited to discover that it shows features that have not been observed in older Cambrian anomalocaridids - not one but two sets of swimming flaps along the trunk, representing a stage in the evolution of the two-branched limb, characteristic of modern arthropods such as shrimps."

The giant arthropod is named after its discoverer Mohamed Ben Moula. The researchers say the creature's apparent filter-feeding apparatus is unique from an ecological standpoint. Most anomalocaridids were active predators that grabbed prey with spiny head limbs. Aegirocassis benmoulae appears to have harvested plankton.

Peter Van Roy, an associate research scientist at Yale, led the research on the enormous sea creature. Van Roy says, "Giant filter-feeding sharks and whales arose at the time of a major plankton radiation, and Aegirocassis represents a much, much older example of this - apparently overarching - trend."

Van Roy also told NPR that Aegirocassis was the biggest living animal on the planet at the time. He says it was nearly three times as big as any other creature living during its time period.

A research paper on Aegirocassis can be found here in the journal, Nature.

Photo: Marianne Collins/ArtofFact