In the foreground, Anomalocaris has captured a hapless trilobite, seized in its anterior giant appendages which are manoeuvering the prey towards the armoured mouth. Colour plate and partial caption taken from Morris, Simon Conway. 1998. The Crucible of Creation, The Burgess Shale and Rise of Animals. Oxford University Press.
An oddity?
Anomalocaris has not been classified in any existing group; hence why we have chosen to dub it a “Burgess Shale Oddity”. Anomalocaris does not appear to be a member of the phylum Arthropoda. It does not have serial, jointed appendages, and its mouth does not resemble that of any existing arthropod. Variation has been found in specimens that is significant enough that the naming of multiple species of Anomalocaris has been necessary, however.
Size of the predator
The size of Anomalocaris is immediately striking in comparison with the other organisms of the Burgess Shale. Specimens have been found that are up to 60 cm or 2 ft long. Furthermore, it has been extrapolated from the size of the mouth and feeding appendages of some species that they could grow up to 6 ft in length! Anomalocaris has been described as the most widely distributed organism in the Burgess Shale, as partial specimens have been found in Cambrian beds in China, Greenland, and around the world.
Locomotion
The depiction of Anomalocaris on this page shows it swimming with the lobes found along most of its body. Because they are not jointed, it is not believed that Anomalocaris could have walked. To see how Anomalocaris moved, check out cool 3-D animations at http://homepage1.nifty.com/burgess/aaj.html
Feeding
The mouth of Anomalocaris would have been incapable of completing closing. It is believed that it would have used its frontal appendages to place food in its mouth, and then the constricting mouth would have broken open the exoskeleton of its prey. (Many organisms in the Burgess Shale are ancient arthropods and possess exoskeletons.) Trilobites have been discovered with bite marks that may have come from Anomalocaris. This is a big difference from the oral arms of the jellyfish that Walcott envisioned!
