These ancient relatives to the arthropods of old swam in the seas that covered the planet. Their fossils have been found in places that are (now) as far apart as Canada, China, and Australia.
Anomalocaris grew up to 3ft in length, and had a segmented body that allowed it to swim using an undulating motion. They also had complex, stalked eyes, and two arms covered in barbs that extended from the mouth. The mouth itself was circular, and may have been able to crush hard-bodied prey like Trilobites.
The interesting anatomical features of Anomalocaris made it difficult to identify for many, many years. Different body parts were found independent from one another, and were actually attributed to several different animals, including Jellyfish and Crustaceans. While the first fossils were discovered in 1892, it took until 1985 for scientists to realize all of those fossils belonged to the same animal!
Status : Extinct, lived during the Cambrian ~500 million years ago
Location : Worldwide
Size : Length up to 1m
Classification : Class : †Dinocaridida -- Order : †Radiodonta
Family : †Anomalocarididae -- Genus : †Anomalocaris
Images : Worldlesstech