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The Birth of Filter-Feeding Giants

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The Cambrian seas have a new apex predator with the discovery of one of the earliest arthropods measuring twice as large as the previous heavyweight champion.

Every so often a new fossil turns up that really surprises even hardcore palaeontologists, such as the recent discovery of the world’s largest animal of its time, Aegirocassis benmoulae, in Morocco. The beautifully preserved Ordovician fossil remains, dated at around 470–480 million years old, show that Aegirocassis was a close relative of the previous Cambrian heavyweight, the arthropod Anomalocaris, which reached around 1 metre in length and had been considered the apex predator in the Cambrian seas.

However, Aegirocassis was at least double this size (2 metres) and lived primarily as a filter-feeder, scooping schools of plankton and small shrimp-like creatures into its mouth with large scoop-shaped appendages that look similar to the paired flaps at the mouth of a manta ray. Both structures help direct schools of small creatures into the mouth. The work was published online in Nature by a team from Yale University led by Dr Peter Van Roy.

Anomalocarids used a series of flaps along the sides of their body to swim, and it has long been debated if these are homologous to other arthropod limbs. The new fossils solve this mystery and reveal the truth about the relationships of this enigmatic group...

The full text of this article can be purchased from Informit.