Anomalocaris

Anomalocaris (from Ancient Greek ανώμαλος, meaning "anomalous", and καρίς, meaning "shrimp", with the intended meaning "unlike other shrimp") is an extinct genus of radiodont, an order of early-diverging stem-group marine arthropods. It is best known from the type species A. canadensis, found in the Stephen Formation (particularly the Burgess Shale) of British Columbia, Canada. The other named species A. daleyae is known from the somewhat older Emu Bay Shale of Australia. Other unnamed Anomalocaris species are known from China and the United States. Like other radiodonts, Anomalocaris had swimming flaps running along its body, large compound eyes densely packed with lenses, and a single pair of segmented, frontal appendages, which in Anomalocaris were used to grasp prey. Estimated to reach 34.2–37.8 cm (13.5–14.9 in) long excluding the frontal appendages and tail fan, Anomalocaris is one of the largest animals of the Cambrian, and thought to be one of the earliest examples of an apex predator, though others have been found in older Cambrian lagerstätten deposits. Anomalocaris was only known from its frontal appendages when it was first described in 1892, which were originally considered to be the body of a shrimp-like arthropod. Due to initially only being known from isolated body parts, Anomalocaris has a convoluted taxonomic history, being historically confused with the related radiodont genus Peytoia, with complete body specimens of Anomalocaris only being described in the late 20th century. It is the type genus of Anomalocarididae, a family which previously included all radiodonts but recently only Anomalocaris and a few closely related taxa.