page_title: Anomalocaris
section_title: Diet
hierarchical_section_title: Anomalocaris / Paleobiology / Diet
caption_attribution_description: English: A reconstruction of Anomalocaris canadensis
context_page_description: Anomalocaris is an extinct genus of radiodont, an order of animals thought to be closely related to ancestral arthropods. The first fossils of Anomalocaris were discovered in the Ogygopsis Shale by Joseph Frederick Whiteaves, with more examples found by Charles Doolittle Walcott in the Burgess Shale. Originally several fossilized parts discovered separately were thought to be three separate creatures, a misapprehension corrected by Harry B. Whittington and Derek Briggs in a 1985 journal article. Anomalocaris is thought to be one of the earliest examples of an apex predator, though others have been found in older Cambrian lagerstätten deposits.
context_section_description: A long-standing view holds that Anomalocaris fed on hard-bodied animals, including trilobites—making it one of the first predators—and its mid-gut glands strongly suggest a predatory lifestyle. However, its ability to penetrate mineralised shells has been questioned. Some Cambrian trilobites have been found with round or W-shaped "bite" marks, which were identified as being the same shape as the mouthparts of Anomalocaris. Stronger evidence that Anomalocaris ate trilobites comes from coprolite, which contain trilobite parts and are so large that the anomalocarids are the only known organism from that period large enough to have produced them. However, since Anomalocaris lacks any mineralised tissue, it seemed unlikely that it would be able to penetrate the hard, calcified shell of trilobites. Rather, the coprolites may have been produced by a different organisms, such as the trilobites of the genus Redlichia. 
  The lack of wear on anomalocaridid mouthparts suggests they did not come into regular contact with mineralised trilobite shells, and were possibly better suited to feeding on smaller, soft-bodied organisms by suction, since they would have experienced structural failure if they were used against the armour of trilobites. A. canadensis may have been capable of feeding on organisms with hard exoskeletons due to the short, robust spines on its appendages. However, as opposed to Peytoia whose mouthpiece is more rectangular with short protruding spines, the mouthpiece of A. canadensis has a smaller and more irregular diamond-shaped opening, not permitting strong biting motions, and indicating a suction-feeding behavior to suck in softer organisms.
  Phylogenetic analyses have also found A. briggsi to belong to the closely related, filter-feeding family Cetiocaridae, which suggests that may have been a filter-feeder as well.
  One suggested possibility is that anomalocaridids fed by grabbing one end of their prey in their jaws while using their appendages to quickly rock the other end of the animal back and forth. This produced stresses that exploited the weaknesses of arthropod cuticles, causing the prey's exoskeleton to rupture and allowing the predator to access its innards. This behaviour was originally thought to have provided an evolutionary pressure for trilobites to roll up, to avoid being flexed until they snapped.
  Anomalocaris magnabasis, a large species of Anomalocaris discovered south of the Burgess Shale, had spinules projecting from the spine base. These small, thin spines would have allowed Anomalocaris magnabasis to be a more effective hunter of soft bodied prey, able to pick up and quickly ensnare priapulids and other animals that lacked a hard shell.
caption: Reconstruction of Anomalocaris canadensis.
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