Anomalocaris prehistoric marine animal. Computer illustration of an Anomalocaris sp. marine animal swimming over sponges (Vauxia sp. and Wapkia sp.) on the ocean floor around 500 million years ago, during the Middle Cambrina period. Growing to over one metre long, Anomalocaris is believed to have been a formidable predator with two large feeding arms in front of its mouth that are covered in barb-like spikes. It may have been one of the earliest arthropods. Also shown are a trilobite (Olenoides serratus) and small flower-like Dinomischus sp. animals.