Anomalocaris: Cambrian Arthropod Predator

Anomalocaris was the top arthropod predator of the Cambrian oceans, and indeed the largest creature yet alive at that point. This armored marine creature had a long, plated diamond-shaped body between two and five feet in length, with a small head with two anterior appendages for grabbing prey. Some species vary with regard to the size of the head and the presence of a fluke-like tail at the end of the body. However, all species of anomalocaris seemed to move by undulating the body up and down to create a wave-like motion. Fossilized remains of anomalocaris have been found in shale deposits in Canada, the United States, China, and Australia, although complete finds have been rare. Indeed the lack of complete skeletons caused a great deal of frustrations for early paleontologists and scientists who had uncovered incomplete remains.

It took a while for scientists to piece together what anomalocaris actually was. Upon discovery of fossilized remains, early scientists mistakenly believed that the anterior appendages used for grasping prey were actually the bodies of shrimp (due to their likeness). Also, fossilized imprints of the circular mouth of anomalocaris were initially mistaken to be some form of soft-bodied creature like a jellyfish and the anomalocaris body was thought to be a sponge. Eventually, the pieces were put together and several distinct species of anomalocaris were identified from fossilized remains in different parts of the world.

Anomalocaris preyed on a number of creatures living in the Cambrian seas, primarily other arthropods such as trilobites. Due to its size and specialization, it can be classified as one of the first superpredators, ravaging marine populations during the Cambrian. The circular mouth was lined with jagged, pointy toothlike structures which could crush through the hard armor of the trilobite while the anterior appendages held it in place. These appendages were segmented "arms" that contained barblike projections which would have helped to hold struggling prey in place. These mouthparts resemble those of some insects alive today as well as parasitic fish like lamprey. The presence of multi-lens eyes on eyestalks would have helped anomalocaris locate prey which had not yet evolved such complex sensory organs. Some varieties were more successful hunters than others, and those with smaller mouthparts might have preyed on smaller ocean fauna.

Anomalocaris, along with the anomalocarid family died out after the Mid-Cambrian Period. It is likely that other, more specialized arthropod predators such as giant sea scorpions began to rival them as the top predators in the ocean.