The trilobites seen in this image was once found widespread in the ocean. Something Changed To Limit and finally abolish their success. What do scientists use this example as proof of ? The answers are A. life changes over time and B. Vesitigial organisms once had a function in ancient times.The trilobites first appeared in the Cambrian period and though they entered a decline int the Devonian period, some of them survived until Permian time or for a period of 270 million years. They were divided into 3 segments and were early examples of arthropods. They tended to live on or near the bottom of the oceans and were scavengers in part and as well as living on the ocean floor some swam and fed on plankton.