Anomalocaris is an extinct radiodont genus from the early to middle Cambrian period. Like most radiodonts, Anomalocaris had large compound eyes, several swimming flaps running along the body, and a sing pair of frontal appendages used to grasp prey. Anomalocaris was one of the biggest animals in the Cambrian, and is thought to be one of the earliest apex predators. Anomalocaris was only known from its frontal appendages when it was initially described in 1892, which were originally presumed to be the body of a shrimp-like arthropod. Owing to this fragmented initial understanding, Anomalocaris possesses a complex taxonomic lineage, historically confounded with the related radiodont Peytoia, with complete Anomalocaris specimens only being described in the late 20th century.
Anomalocaris propelled itself through the water via undulations of its flexible lateral flaps. These flaps, each descending sequentially, facilitated an overlapping configuration, this allowed the lobes on each side of the body to act as a single "fin", maximizing the swimming efficiency. Based on fossilized eyes from the Emu Bay Shale, the stalked eyes of Anomalocaris were 30 times more powerful than those of trilobites, which were long thought to have had the most advanced eyes of any contemporary species. With one specimen having over 24,000 lenses in one eye, the resolution of the 3-centimeter-wide (1.2 inches) eyes would have been rivaled only by that of the modern dragonfly, which boasts 28,000 lenses in each eye. Further, estimations of ecdysozoan opsins suggest that Anomalocaris may have had dichromatic color vision.