Oldest T. Rex Relative Unveiled
Dr Occult writes "A group of researchers have found the forefather of T. Rex in Xinjiang province in northwestern China. It lived around 160 million years ago. This makes it more than twice as old as T. Rex, and the most primitive known member of the family. The researchers were surprised to learn the 3m long dinosaur sported a spectacular feathered crest on its head which may have been brightly coloured."
Considering it's a fossil, I'd say they look at the bones...
An interesting anagram of "BANACH TARSKI" is "BANACH TARSKI BANACH TARSKI"
You are acting like there is some sort of binary: either they know for certain, or its just a guess. This is nonsense. Some things are known to a very high degree of certainty, because multiple lines of evidence all converge. Sometimes things are less well supported... and people generally say so.