The iconic dinosaur, the best known in history:
The dinosaur’s evolutionary origins, for example, are still a mystery. Researchers are eagerly trying to determine how these kings of the Cretaceous period (which spanned from 145 million to 66 million years ago) arose from a line of tiny dinosaurs during the Jurassic period (201 million to 145 million years ago). There is also considerable debate about what T. rex was like as a juvenile, and whether palaeontologists have spent decades mistaking its young for a separate species. Even the basic appearance of T. rex is in dispute: many researchers argue that the giant was covered in fluff or fuzz rather than scales. And then there is the vexing question of why T. rex had such a massive head and legs but relatively puny arms.
Solution: Speculate less, dig more.