Anomalocaris is a strange and interesting genus. So strange, in fact, that three separate parts of their fossils were once identified as three separate creatures. It took nearly a century from the discovery of the first piece, for Anomalocaris canadensis to be properly identified and unified into single animal1.
Anomalocaridids, the group in which Anomalocaris belongs, grew to over a meter in length. Although small in comparison to marine animals today, at the time they swam the oceans (see an animation), between 540 and 472 million years ago, they were the biggest predators in the sea by far1,2.
Anomalocaridids had two segmented tentacle-like appendages that were probably used in hunting, perhaps by stabbing or by grasping prey. Their mouth was circular and had ‘teeth’ that closed like a camera shutter. Some of them may have eaten hard-bodied animals like trilobites, but it is thought that soft-bodied animals were their primary prey.