[10] It is the type genus of Anomalocarididae, a family which previously included all radiodonts but recently only Anomalocaris and a few closely-related taxa.

[9][8] As Stephen Jay Gould, who popularised the Cambrian explosion in his 1989 book Wonderful Life, appropriately described:[The story of Anomalocaris is] a tale of humor, error, struggle, frustration, and more error, culminating in an extraordinary resolution that brought together bits and pieces of three "phyla" in a single reconstructed creature, the largest and fiercest of Cambrian organisms.

[7] In August 1891, Henri-Marc Ami, Assistant Palaeontologist at GSC, collected many trilobites and brachiopod fossils,[14] along with 48 more of the unknown specimens.

[7]In 1928, Danish paleontologist Kai Henriksen proposed that Tuzoia, a Burgess Shale arthropod which was known only from the carapace, represented the missing front half of Anomalocaris.

The first fossilized mouth of such a kind of animal was discovered by Charles Doolittle Walcott, who mistook it for a jellyfish and placed it in the genus Peytoia.

In 1966, the Geological Survey of Canada began a comprehensive revision of the Burgess Shale fossil record, led by Cambridge University paleontologist Harry B.

[8] In the process of this revision, Whittington and his students Simon Conway Morris and Derek Briggs would discover the true nature of Anomalocaris and its relatives, but not without contributing to the history of misinterpretations first.

[16] Later, while clearing what he thought was an unrelated specimen, Harry B. Whittington removed a layer of covering stone to discover the unequivocally connected frontal appendage identical to Anomalocaris and mouthpart similar to Peytoia.

The find also indicated that advanced arthropod eyes had evolved very early, before the evolution of jointed legs or hardened exoskeletons.

[2] Numerous species have been previously referred to Anomalocaris, but subsequent analyses have doubted this generic assignment,[22][23][24] and reclassified them within different genera.

[36] Each flap sloped below the one more posterior to it,[37] and this overlapping allowed the lobes on each side of the body to act as a single "fin", maximizing the swimming efficiency.

The body was widest between the third and fifth lobe and narrowed towards the tail, with additional three pairs of small flaps on the constricted neck region.

[32] The top one, known as a head shield, dorsal carapace or H-element, was shaped like a laterally-elongated[40] oval, with a distinct rim on the outer edge.

[42] The interpretation of Anomalocaris as an active predator is widely accepted throughout the history of research,[9][8][10] as its raptorial frontal appendages and mid-gut glands strongly suggest a predatory lifestyle.

[45][10][5][6] 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 Peytoia (previously misidentified as those of Anomalocaris[46][10]).

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.

[45][39] A. canadensis was suggested to have been capable of feeding on organisms with hard exoskeletons due to the short, robust spines on its frontal appendages.

[39][26] However, this conclusion is solely based on the comparison with the fragile frontal appendages of suspension feeding radiodonts (e.g. Echidnacaris and Houcaris spp.).

[10] Three-dimensional modelling of various radiodont frontal appendages also suggest that A. canadensis is more capable to prey on smaller (2–5 cm in diameter), active, soft-bodied animals (e.g. vetulicolian; free-swimming arthropods like isoxyids and hymenocarines; Nectocaris).

Postured with the frontal appendages outstretched, Anomalocaris would have been able to swim with maximized speed, similar to modern predatory water bugs.

It probably would have not hunted benthic animals like trilobites, considering the possibility of damaging the frontal appendages on the substrate while trying to grab prey from seafloor at speed.

Instead, other animals such as other radiodonts (e.g. Hurdia, Cambroraster, Titanokorys, Stanleycaris) and artiopods (e.g. Sidneyia) would have been benthic predators in the Burgess Shale.

[1] In the Burgess Shale, Anomalocaris is more common in the older sections, notably the Mount Stephen trilobite beds.

Anomalocaris daleyae (Emu Bay Shale) lived in a comparable environment; the shallow, tropical waters of Cambrian Australia.