Trilobite
Underneath and rarely preserved are three pairs of legs for the head and paired legs for each pleural groove. Trilobites are the earliest known animal to have vision. Some possessed eyes and some seem to have no eyes at all, while others had eyes made up of many parts that could see all around the animal. Trilobites ranged in length from  to , with a typical size range of . The world's largest trilobite, 'Isotelus rex', was found in 1998 by Canadian scientists on the shores of Hudson Bay.