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Smithsonian National Museum of Natural History
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Department of Paleobiology

Anomalocaris canadensis (proto-arthropod)

Anomalocaris

This fearsome-looking beast is the largest known Burgess Shale animal. Some related specimens found in China reach a length of six feet! The giant limbs in front, which resemble shrimp tails, were used to capture and hold its prey. A formidable mouth on the undersurface of the head had a squared ring of sharp teeth that could close in like nippers to crack the exoskeleton of arthropods or other prey. With those large eyes and a body half flanked with a series of swimming lobes, this must have been an active, formidable predator! Anomalocaris is one of the most widely distributed of the Burgess Shale animals. In addition to Canada and China, specimens have been unearthed in Cambrian deposits in Greenland and Utah.

After death this large organism tended to disintegrate and fall apart into separate chunks, and completely intact fossil remains are very rare. Since these chunks resembled other kinds of simple animals (such as those shrimp-like front limbs), for a long time the separated pieces were interpreted to be individual animals. No one was able to recognize Anomalocaris for what it was until complete specimens began to be found! If you look at photos of actual fossil pieces, the jaws and the forelimbs (below), you'll see how easy it to be mistaken.

Anomalocaris
  • Anomalocaris - jaws

Anomalocaris
  • Anomalocaris - forelimbs

Anomalocaris canadensis (ah-NOM-ah-LAH-kariss KAN-ah-DEN-sis. Anomalos (Gr.) = unusual; caris (Gr.) = shrimp; hence: "Unusual Canadian shrimp".


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