sharks are amazing fish that have been around since long before the dinosaurs existed

鲨鱼在恐龙出世前就已经存在了.
sharks（主语） are （系动词）amazing fish（表语） that （定语从句的连接词,也是定语从句的主语）have been around（谓语） since（时间状语从句的连接词） long before the dinosaurs existed（后面都是时间状语）been around 和since 分别翻译为什么been around ----四处活动since----自从