It propelled itself through the water by undulating the flexible lobes on the sides of its body.[4] Each lobe sloped below the one more posterior to it,[5] and this overlapping allowed the lobes on each side of the body to act as a single "fin", maximizing the swimming efficiency.[4] The construction of a remote-controlled model showed this mode of swimming to be intrinsically stable,[6] implying that Anomalocaris would not have needed a complex brain to manage balance while swimming. The body was widest between the third and fifth lobe and narrowed towards the tail; it had at least 11 lobes in total.[5] It is difficult to distinguish lobes near the tail, making an accurate count difficult.[5] Anomalocaris had a large head, a single pair of large, compound eyes on stalks comprising approximately 16,000 lenses,[7][8] and an unusual disk-like mouth. The mouth was composed of 32 overlapping plates, four large and 28 small, resembling a pineapple ring with the center replaced by a series of serrated prongs.[2] The mouth could constrict to crush prey, but never completely close, and the tooth-like prongs continued down the walls of the gullet.[9] Two large 'arms' (up to seven inches in length when extended[9]) with barb-like spikes were in front of the mouth.[3] The tail was large and fan-shaped, and along with undulations of the lobes, was probably used to propel the creature through Cambrian waters.[2][4][10] Stacked lamella of what were probably gills attached to the top of each lobe.