 The fossils of the Burgess Shale were hidden in store rooms until the 1960s . When Whittington and his colleagues first began to publish their Burgess finds in the early 1970s , the fossils became central to the debate about how quickly animals arose , and were interpreted as evidence that all the living bilaterian phyla had appeared in the Early Cambrian , along with many other phyla that had become extinct by the end of the Cambrian . 
