7-Foot-Long ‘Sea Monster’ Was Ancestor of Shrimp

Ancest ShrimpEarly ancestors of today’s shrimp were huge, yet peaceful, creatures, suggests a new study that sheds light on these gentle giants that lived around 485 million years ago.

The animals, described in the latest issue of the journal Nature, are called anomalocaridids, and they lived more like today’s enormous baleen whales than modern tiny shrimp.

Lead author Peter Van Roy of Yale University and Ghent University, with colleagues Allison Daley and Derek Briggs, focused on the remains of a particular anomalocaridid, Aegirocassis benmoulae. It grew to become about 7 feet long.

“The huge size of A. benmoulae represents a much earlier example of a filter-feeding lifestyle correlating to gigantism,” Van Roy and his team wrote.

The remains of this species were unearthed at a site in Morocco. Its anatomy shows that, when alive, it would have passively strained out plankton and other nutrients suspended in water. A specialized filtering structure took care of the straining.

The study shows how ancient this method of feeding is. Today’s clams, krill, sponges, baleen whales, certain sharks, flamingos, some ducks, and other animals are filter feeders. This marine beast, however, was an early ancestor of shrimp, other crustaceans, insects and spiders.

If you look closely at the image of A. benmoulae, you’ll see that each of its trunk segments has flaps that bear a resemblance to either walking limbs or gill flaps seen on the trunks of modern insects, spiders and crustaceans.

source : http://news.discovery.com/animals/7-foot-long-sea-monster-was-ancestor-of-shrimp-150311.htm

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