Anomalocarids are an ancient marine arthropod relative. They are abnormal and resemble enlarged predatory shrimp, growing up to 1 m long. These giant hunters dominated the small tropical oceans where modern China is located today and ruled the Cambrian period. They are the earliest forms of an apex predator, feeding on every organism in the prehistoric seas, such as trilobites; hard-bodied invertebrates, and priapulid worms; which are soft-bodied invertebrates. Anomalocarids have enormous front appendages lined with serrated barbs for seizing unfortunate prey. These shrimp-like creatures may have flipped the hard-bodied trilobites over to expose the much softer underside. Cambrian marine life was bizarre, creatures such as hallucigenia crawled across the ocean floor like spiked, long-legged caterpillars!
Examples of larger organisms thriving in the cambrian seas are trilobites. Trilobites were a very successful group, they survived multiple mass extinctions and diversified each time. Unfortunately, they became extinct prior to the Triassic period, and thus never co-existed with dinosaurs and remain extinct today. However, during their time they were the first adapting form of life in existence. For example, multiple species developed large protruding spines, likely present to offend possible predators. Others became more stream-lined and formed large compound eyes, these species would have actively swam through open seas. On the other hand, most early species were flat and lacked large eyes – adapted to consuming organic matter and even burying beneath thin layers of rock and sand.
