Anomalocaris

Anomalocaris was a marine arthropod from the early to middle Cambrian period. It is one of the first hyper carnivores to appear on Earth.

Facts
Anomalocaris is thought to have been a predator. It propelled itself through the water by undulating the flexible lobes on the sides of its body. Each lobe sloped below the one more posterior to it, and this overlapping allowed the lobes on each side of the body to act as a single "fin", maximizing the swimming efficiency. The construction of a remote-controlled model showed this mode of swimming to be intrinsically stable, meaning that Anomalocaris need not have had a complex brain to cope with balancing while swimming. The widest part of the body was on the third to fifth lobe; it narrowed towards its tail, and had at least 11 lobes in total. The more posterior lobes are difficult to discriminate, making an accurate count difficult. Anomalocaris had a large head, a single pair of large, compound eyes on stalks comprising approximately 16,000 individual lenses, 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. The mouth could constrict to crush prey, but never completely close, and the tooth-like prongs continued down the walls of the gullet. Two large 'arms' (up to seven inches in length when extended) with barb-like spikes were positioned in front of the mouth. The tail was large and fan-shaped, and along with undulations of the lobes, was probably used to propel the creature through Cambrian waters. Stacked lamella of what were probably gills attached to the top of each lobe. For the time in which it lived, Anomalocaris was a truly gigantic creature, reaching lengths of up to two meters.

Water Dwellers
An Anomalocaris was first seen attacking and killing a trilobite. It then fought against another Anomalocaris. One of them lost the fight, damaging and splitting its armour in the process. A shoal of Haikouichthys then harassed and fed off of the Anomalocaris whilst it was still alive.

Trivia

 * Upon his initial discovery in 1912, Anomalocaris was believed to be multiple animals; his front appendages were believed to be the hinder halves of shrimp ("strange" because their "legs" weren't segmented), his mouth was believed a jellyfish, and his body a sea cucumber or a sponge. This mistake was only realised in the 1980s, providing the modern reconstruction as the metre-long (2 metres including the tail in some species) flippered monster.